US20150292309A1 - Heater pattern including heaters powered by wind-electricity for in situ thermal processing of a subsurface hydrocarbon-containing formation - Google Patents

Heater pattern including heaters powered by wind-electricity for in situ thermal processing of a subsurface hydrocarbon-containing formation Download PDF

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US20150292309A1
US20150292309A1 US14/646,747 US201314646747A US2015292309A1 US 20150292309 A1 US20150292309 A1 US 20150292309A1 US 201314646747 A US201314646747 A US 201314646747A US 2015292309 A1 US2015292309 A1 US 2015292309A1
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zone
heaters
heater
outer zone
formation
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English (en)
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Harold Vinegar
Scott Nguyen
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GENIE IP BV
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GENIE IP BV
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B36/00—Heating, cooling or insulating arrangements for boreholes or wells, e.g. for use in permafrost zones
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
    • E21B43/243—Combustion in situ
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B36/00—Heating, cooling or insulating arrangements for boreholes or wells, e.g. for use in permafrost zones
    • E21B36/04—Heating, cooling or insulating arrangements for boreholes or wells, e.g. for use in permafrost zones using electrical heaters
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/14—Obtaining from a multiple-zone well
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
    • E21B43/2401—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection by means of electricity
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/30—Specific pattern of wells, e.g. optimising the spacing of wells

Definitions

  • the present invention relates to methods and systems of heating a subsurface formation, for example, in order to produce hydrocarbon fluids therefrom.
  • Hydrocarbons obtained from subterranean formations are often used as energy resources, as feedstocks, and as consumer products.
  • Concerns over depletion of available hydrocarbon resources and concerns over declining overall quality of produced hydrocarbons have led to development of processes for more efficient recovery, processing and/or use of available hydrocarbon resources.
  • In situ processes may be used to remove hydrocarbon materials from subterranean formations that were previously inaccessible and/or too expensive to extract using available methods.
  • Chemical and/or physical properties of hydrocarbon material in a subterranean formation may need to be changed to allow hydrocarbon material to be more easily removed from the subterranean formation and/or increase the value of the hydrocarbon material.
  • the chemical and physical changes may include in situ reactions that produce removable fluids, composition changes, solubility changes, density changes, phase changes, and/or viscosity changes of the hydrocarbon material in the formation.
  • Retorting processes for oil shale may be generally divided into two major types: aboveground (surface) and underground (in situ). Aboveground retorting of oil shale typically involves mining and construction of metal vessels capable of withstanding high temperatures. The quality of oil produced from such retorting may typically be poor, thereby requiring costly upgrading. Aboveground retorting may also adversely affect environmental and water resources due to mining, transporting, processing, and/or disposing of the retorted material. Many U.S. patents have been issued relating to aboveground retorting of oil shale. Currently available aboveground retorting processes include, for example, direct, indirect, and/or combination heating methods.
  • In situ retorting typically involves retorting oil shale without removing the oil shale from the ground by mining.
  • Modified in situ processes typically require some mining to develop underground retort chambers.
  • An example of a “modified” in situ process includes a method developed by Occidental Petroleum that involves mining approximately 20% of the oil shale in a formation, explosively rubblizing the remainder of the oil shale to fill up the mined out area, and combusting the oil shale by gravity stable combustion in which combustion is initiated from the top of the retort.
  • modified in situ processes include the “Rubble In Situ Extraction” (“RISE”) method developed by the Lawrence Livermore Laboratory (“LLL”) and radio-frequency methods developed by IIT Research Institute (“IITRI”) and LLL, which involve tunneling and mining drifts to install an array of radio-frequency antennas in an oil shale formation.
  • RISE Rule In Situ Extraction
  • LLL Lawrence Livermore Laboratory
  • IITRI IIT Research Institute
  • wells or wellbores may be used to treat the hydrocarbon-containing formation using an in situ heat treatment process.
  • vertical and/or substantially vertical wells are used to treat the formation.
  • horizontal or substantially horizontal wells such as J-shaped wells and/or L-shaped wells
  • U-shaped wells are used to treat the formation.
  • combinations of horizontal wells, vertical wells, and/or other combinations are used to treat the formation.
  • wells extend through the overburden of the formation to a hydrocarbon-containing layer of the formation. In some situations, heat in the wells is lost to the overburden.
  • surface and overburden infrastructures used to support heaters and/or production equipment in horizontal wellbores or U-shaped wellbores are large in size and/or numerous.
  • Wellbores for heater, injection, and/or production wells may be drilled by rotating a drill bit against the formation.
  • the drill bit may be suspended in a borehole by a drill string that extends to the surface.
  • the drill bit may be rotated by rotating the drill string at the surface.
  • Sensors may be attached to drilling systems to assist in determining direction, operating parameters, and/or operating conditions during drilling of a wellbore. Using the sensors may decrease the amount of time taken to determine positioning of the drilling systems.
  • Heaters may be placed in wellbores to heat a formation during an in situ process.
  • heaters There are many different types of heaters which may be used to heat the formation. Examples of in situ processes utilizing downhole heaters are illustrated in U.S. Pat. No. 2,634,961 to Ljungstrom; U.S. Pat. No. 2,732,195 to Ljungstrom; U.S. Pat. No. 2,780,450 to Ljungstrom; U.S. Pat. No. 2,789,805 to Ljungstrom; U.S. Pat. No. 2,923,535 to Ljungstrom; U.S. Pat. No. 4,886,118 to Van Meurs et al.; and U.S. Pat. No. 6,688,387 to Wellington et al.; each of which is incorporated by reference as if fully set forth herein.
  • Embodiments of the present invention relate to heater patterns and related methods of producing hydrocarbon fluids from a subsurface hydrocarbon-containing formation (for example, an oil shale formation) where a heater cell may be divided into nested inner and outer zones.
  • One or more heaters of the heater cell are powered primarily by electricity generated by wind.
  • Production wells may be located within one or both zones.
  • heaters are arranged at a relatively high spatial density while in the larger surrounding outer zone, a heater spatial density is significantly lower. Due to the higher heater density, a rate of temperature increase in the smaller inner zone of the subsurface exceeds that of the larger outer zone, and a rate of hydrocarbon fluid production ramps up significantly faster in the inner zone than in the outer zone.
  • the overall density of heaters in the heater cell is significantly less than that within the inner zone.
  • the number of heaters required for the heater pattern is substantially less than what would be required if the heater density throughout the heater cell was that within the inner zone.
  • At least a majority (in some embodiments, at least two-thirds) of heaters of the inner zone are powered primarily by wind electricity while at least a majority (in some embodiments, at least two-thirds) of heaters of the outer zone are powered primarily by fuel combustion.
  • This may be useful, for example, in remote locations with minimal infrastructure where it is relatively easy to install wind turbines despite their expense. Almost immediately after installing the wind turbines and associated inner-zone heaters, it is possible to commence heating of at least the inner zone with minimal delay.
  • the second embodiment relates to the opposite situation.
  • at least a majority (e.g. at least half, or at least two-thirds) of heaters of the inner zone are powered primarily by fossil fuel electricity or by fossil fuel combustion and
  • at least a majority (e.g. at least half, or at least two-thirds) of heaters of the outer zone are powered primarily by wind electricity.
  • the outer zone heaters typically operate for a significantly longer period of time, the second embodiment is particularly advantageous for minimizing CO 2 footprint.
  • a reliable/continuous energy source is important (i.e. rather than relying on intermittent wind or solar), so as to ensure early production of hydrocarbon production from the formation.
  • most inner zone heaters therefore derive their power from fossil fuels as opposed to from intermittent sources. Thus ensures that the inner zone heats up quickly and minimizes a time delay before production begins.
  • thermal energy from the inner zone may migrate outwardly to the outer zone so as to accelerate hydrocarbon fluid production in the outer zone.
  • a rate of hydrocarbon fluid production in the outer zone may ramp up fast enough so that the overall rate of hydrocarbon fluid production for the heater cell as a whole is substantially sustained, over an extended period of time, once the inner zone production rate has peaked.
  • the heater patterns disclosed herein provide the minimal, or nearly the minimal, rise time to a substantially sustained production rate that is possible for a given number of heaters.
  • the heater patterns disclosed herein minimize, or nearly minimize, the number of heaters required to achieve a relatively fast rise time with a sustained production level.
  • a heater spacing within the outer zone is about twice that of the inner zone and/or a heater density within the inner zone is about three times that of the outer zone and/or an average distance, in the inner zone, to a nearest heater is about 2-3 times that within the outer zone.
  • an area of a region enclosed by a perimeter of the outer zone is between two and seven (e.g. at least two or at least three and/or at most seven or at most six or at most five) times (for example, about four times) that enclosed by a perimeter of the inner zone.
  • the inner zone, outer zone or both are shaped as a regular hexagon. This shape may be particularly useful when heater cells are arranged on a two-dimensional lattice so as to fill a two-dimensional portion of the subsurface while eliminating or substantially minimizing the size of the interstitial space between neighboring heater cells. As such, a number of heater cells may entirely, or almost entirely, cover a portion of the sub-surface.
  • Some embodiments of the present invention relate to ‘two-level’ heater patterns where an inner zone of heaters at a higher density is nested within an outer zone of heaters at a lower density.
  • This concept may be generalized to N-level heater patterns where one or more ‘outer’ zones of heaters surround a relatively heater-dense inner zone of heaters.
  • N 2.
  • N 3.
  • N 4.
  • the more outer heater zone is larger than the more inner heater zone.
  • the heater density in the more outer heater zone is significantly less than that in the more inner zone, and although the hydrocarbon fluid production peak in the inner zone occurs at a significantly earlier time than in the more outer zone, sufficient thermal energy is delivered to the more outer zone so once the production rate in the more inner zone ramps up quickly, this rate may be substantially sustained for a relatively extended period of time by hydrocarbon fluid production rate in the more outer zone.
  • further performance improvements may be achieved by: (i) concentrating electrical heaters in the denser inner zone while the heaters of the outer zone are primarily molten salt heaters; and/or (ii) significantly reducing a power output of the inner-zone heater after an inner zone hydrocarbon fluid production rate has dropped (e.g. by a first minimal threshold fraction) from a maximum level; and/or (iii) substantially shutting off one or more inner zone production wells after the inner zone hydrocarbon fluid production rate has dropped (e.g. by a second minimal threshold fraction equal to or differing from the first minimal threshold fraction) from a maximum level; and/or (iv) injecting heat-transfer fluid into the inner zone (e.g.
  • inner zone production well(s) and/or via inner zone injection well(s)) so as to accelerate the outwardly migration of thermal energy from the inner zone to the outer zone—for example, by supplementing outwardly-directed diffusive heater transfer with outwardly-directed convective heat transfer.
  • a heater cell divided into nested inner and outer zones such that an enclosed area ratio between respective areas enclosed by substantially-convex polygon-shaped perimeters of the outer and inner zones is between two and seven, heaters being located at all polygon vertices of inner and outer zone perimeters, inner zone and outer zone heaters being respectively distributed around inner and outer zone centroids such that an average heater spacing in outer zone significantly exceeds that of inner zone, at least a majority of the heaters in the inner zone being powered primarily by fuel combustion and at least a majority of heaters in the outer zone being powered primarily by electricity generated by wind.
  • a heater cell divided into nested inner and outer zones such that an enclosed area ratio between respective areas enclosed by substantially-convex polygon-shaped perimeters of the outer and inner zones is between two and seven, heaters being located at all polygon vertices of inner and outer zone perimeters, inner zone and outer zone heaters being respectively distributed around inner and outer zone centroids such that an average heater spacing in outer zone significantly exceeds that of inner zone, at least a majority of the heaters in the inner zone being powered primarily by fuel combustion and at least a majority of heaters in the outer zone being powered primarily by electricity generated by wind.
  • a heater cell divided into nested inner and outer zones such that an enclosed area ratio between respective areas enclosed by substantially-convex polygon-shaped perimeters of the outer and inner zones is between two and seven, heaters being located at all polygon vertices of inner and outer zone perimeters, inner zone and outer zone heaters being respectively distributed around inner and outer zone centroids such that a heater spatial density in inner zone significantly exceeds that of outer zone, at least a majority of the heaters in the inner zone being powered primarily by fuel combustion and at least a of heaters in the outer zone being powered primarily by electricity generated by wind.
  • a system for in-situ production of hydrocarbon fluids from a subsurface hydrocarbon-containing formation comprising: heaters arranged in a target portion of the formation, the target portion being divided into nested inner and outer zones heaters so that inner zone and outer zone heaters are respectively distributed around inner and outer zone centroids, at least a majority of the heaters in the inner zone being powered primarily by fuel combustion and at least a majority of heaters in the outer zone being powered primarily by electricity generated by wind.
  • a first heater that is powered primarily by fuel combustion is located at most 50 meters from a second heater that is powered primarily by electricity generated by wind.
  • a first heater that is powered primarily by fuel combustion is located at most 35 meters from a second heater that is powered primarily by electricity generated by wind.
  • a first heater that is powered primarily by fuel combustion is located at most 20 meters from a second heater that is powered primarily by electricity generated by wind.
  • a first heater that is powered primarily by fuel combustion is located at most 10 meters from a second heater that is powered primarily by electricity generated by wind.
  • a first heater that is powered primarily by fuel combustion is located at most 5 meters from a second heater that is powered primarily by electricity generated by wind.
  • the average separation distance between neighboring heaters that are each powered primarily by electricity generated by wind exceeds the average separation distance between neighboring heaters that are each powered primarily by fuel combustion.
  • the average separation distance between neighboring heaters that are each powered primarily by electricity generated by wind significantly exceeds the average separation distance between neighboring heaters that are each powered primarily by fuel combustion.
  • the average separation distance between neighboring heaters that are each powered primarily by electricity generated by wind significantly is about twice the average separation distance between neighboring heaters that are each powered primarily by fuel combustion.
  • At least some, or at least a majority, or at least two-thirds of the heaters powered primarily by fuel combustion are electrical heaters that are powered primarily by electricity generated by fuel combustion.
  • At least some, or at least a majority, or at least two-thirds of the heaters powered primarily by fuel combustion are combustion heaters where a combusted gas circulated in the subsurface.
  • At least some, or at least a majority, or at least two-thirds of the heaters powered primarily by fuel combustion are electrical heaters wherein a material is resistively heated by electricity generated by fuel combustion.
  • At least some, or at least a majority, or at least two-thirds of the heaters powered primarily by fuel combustion are advection heaters where a material, that is in thermal communication with a circulating heat transfer fluid flowing in the subsurface, is heated resistively by electricity generated by fuel combustion.
  • the resistively heated material is in the subsurface.
  • the resistively heated material is above the surface.
  • At least some, or at least a majority, or at least two-thirds of the heaters powered primarily by electricity generated by wind are electrical heaters wherein a material is resistively heated by electricity generated by wind.
  • At least some, or at least a majority, or at least two-thirds of the heaters powered primarily by electricity generated by wind are advection heaters where a material, that is in thermal communication with a circulating heat transfer fluid flowing in the subsurface, is heated resistively by electricity generated by wind.
  • the resistively heated material is in the subsurface.
  • the resistively heated material is above the surface.
  • two-thirds of the heaters in the inner zone are powered primarily by fuel combustion and at least two-thirds of heaters in the outer zone being powered primarily by electricity generated by wind.
  • a heater cell divided into nested inner and outer zones such that an enclosed area ratio between respective areas enclosed by substantially-convex polygon-shaped perimeters of the outer and inner zones is between two and seven, heaters being located at all polygon vertices of inner and outer zone perimeters, inner zone and outer zone heaters being respectively distributed around inner and outer zone centroids such that an average heater spacing in outer zone significantly exceeds that of inner zone, at least a majority of the heaters in the inner zone being powered primarily by electricity generated by wind and at least a majority of heaters in the outer zone being powered primarily by fuel combustion.
  • a heater cell divided into nested inner and outer zones such that an enclosed area ratio between respective areas enclosed by substantially-convex polygon-shaped perimeters of the outer and inner zones is between two and seven, heaters being located at all polygon vertices of inner and outer zone perimeters, inner zone and outer zone heaters being respectively distributed around inner and outer zone centroids such that an average heater spacing in outer zone significantly exceeds that of inner zone, at least a majority of the heaters in the inner zone being powered primarily by electricity generated by wind and at least a majority of heaters in the outer zone being powered primarily by fuel combustion.
  • a heater cell divided into nested inner and outer zones such that an enclosed area ratio between respective areas enclosed by substantially-convex polygon-shaped perimeters of the outer and inner zones is between two and seven, heaters being located at all polygon vertices of inner and outer zone perimeters, inner zone and outer zone heaters being respectively distributed around inner and outer zone centroids such that a heater spatial density in inner zone significantly exceeds that of outer zone, at least a majority of the heaters in the inner zone being powered primarily by electricity generated by wind and at least a majority of heaters in the outer zone being powered primarily by fuel combustion.
  • a system for in-situ production of hydrocarbon fluids from a subsurface hydrocarbon-containing formation comprising: heaters arranged in a target portion of the formation, the target portion being divided into nested inner and outer zones heaters so that inner zone and outer zone heaters are respectively distributed around inner and outer zone centroids, at least a majority of the heaters in the inner zone being powered primarily by electricity generated by wind and at least a majority of heaters in the outer zone being powered primarily by fuel combustion.
  • At least two-thirds of the heaters in the inner zone are powered primarily by electricity generated by wind and at least two-thirds of heaters in the outer zone being powered primarily by fuel combustion.
  • a centroid of the inner zone is located in a central portion of the region enclosed by a perimeter of the outer zone.
  • each heater cell includes at least one production well located within the inner zone.
  • each heater cell includes at least one production well located within the outer zone.
  • a production well spatial density in the inner zone at least exceeds that of the outer zone.
  • an average heater spacing in outer zone is at least about twice that of inner zone.
  • the area ratio between respective areas enclosed by inner zone and outer zone perimeters is about four, and an average heater spacing in the outer zone is about twice that of the inner zone.
  • a spacing ratio between an average heater spacing of the outer zone and that of the inner zone is about equal to a square root of the area ratio between respective areas enclosed by the inner zone and outer zone perimeters. In some embodiments, a spacing ratio between an average heater spacing of the outer zone and that of the inner zone is about equal to a square root of the area ratio between respective areas enclosed by inner zone and outer zone perimeters. In some embodiments, a heater spatial density in the inner zone is at least about twice that of outer zone. In some embodiments, a heater spatial density in the inner zone is at least twice that of the outer zone. In some embodiments, a heater spatial density in the inner zone is at least about three times that of the outer zone. In some embodiments, a heater density ratio between a heater spatial densities in the inner zone and that of outer zone is substantially equal to an area ratio between an area of the outer zone and that of the inner zone.
  • an area ratio between an area enclosed by a perimeter of outer zone to that enclosed by a perimeter of inner zone is at most six or at most five and/or at least 3.5
  • the one or more heater cells include first and second heater cells having substantially the same area and sharing at least one common heater-cell-perimeter heater.
  • the one or more heater cells further includes a third heater cell having substantially the same area as the first and second heater cells, the third heater cell sharing at least one common heater-cell-perimeter heater with the first heater cell, the second and third heater cells located substantially on opposite sides of the first heater cell.
  • a given heater cell of the heater cells is substantially surrounded by a plurality of neighboring heater cells.
  • a given heater cell of the heater cells is substantially surrounded by a plurality of neighboring heater cells and the given heater cell shares a common heater-cell-perimeter heater with each of the neighboring heater cells.
  • inner zone heaters are distributed substantially uniformly throughout the inner zone.
  • each heater cell being arranged so that within the outer zone, heaters are predominantly located on the outer zone perimeter.
  • At least one of the inner and outer perimeters is shaped like a regular hexagon, like a lozenge, or like a rectangle.
  • the inner and outer perimeters are similar shaped.
  • a majority of heaters are disposed on a triangular, hexagonal or rectangular grid.
  • a total number of inner zone heaters exceeds that of the outer zone.
  • a total number of inner zone heaters exceeds that of the outer zone by at least 50%.
  • At least five inner zone heaters are dispersed throughout the inner zone.
  • At least five or at least seven or at least ten outer zone heaters are located around a perimeter of the outer zone.
  • At least one-third of at least one-half of inner zone heaters are not located on the inner zone perimeter.
  • an aspect ratio is less than 2.5.
  • At least five or at least seven or at least ten heaters are distributed about the perimeter of the inner zone.
  • a majority of the heaters in the inner zone are electrical heaters and a majority of the heaters in the outer zone are molten salt heaters.
  • At least two-thirds or at least three-quarters of inner-zone heaters are electrical heaters and at least two-thirds of outer-zone heaters are molten salt heaters.
  • the system further includes control apparatus configured to regulate heater operation times so that, on average, heaters in the outer zone operate above a one-half maximum power level for at least twice as long as the heaters in the inner zone.
  • control apparatus is configured so that on average, the outer zone heaters operate above a one-half maximum power level for at least three times as long as the inner zone heaters.
  • an average inner-zone heater spacing is between 1 and 10 meters (for example, between 1 and 5 meters or between 1 and 3 meters).
  • the heaters are configured to pyrolize the entirety of both the inner and outer zones.
  • the heaters are configured to heat respective substantial entirety of the inner and outer regions to substantially the same uniform temperature.
  • a ratio between a standard deviation of the spacing and an average spacing is at most 0.2.
  • all heaters have substantially the same maximum power level and/or substantially the same diameter.
  • a ratio between the area of the inner zone and a square of an average distance to a nearest heater within the inner zone is at least 80.
  • a ratio between the area of the inner zone and a square of an average distance to a nearest heater within the inner zone is at least 60 or at least 70 or at least 80 or at least 90 or at least 100.
  • inner and outer zones respective have polygon-shaped perimeters, such that heaters are located at all polygon vertices of inner and outer zone perimeters.
  • the inner zone is substantially-convex.
  • the outer zone is substantially-convex.
  • an average heater spacing in the outer zone significantly exceeds that of the inner zone.
  • an average heater spacing in the outer zone is about twice that of the inner zone.
  • a spacing ratio between an average heater spacing of the outer zone and that of the inner zone is about equal to a square root of the area ratio between respective areas enclosed by the inner zone and outer zone perimeters.
  • a heater spatial density in inner zone significantly exceeds that of the outer zone.
  • a heater spatial density in the inner zone is at least twice that of the outer zone.
  • a heater spatial density in inner zone is at least about three times that of the outer zone.
  • a heater density ratio between a heater spatial densities in inner that of outer zones is substantially equal to a zone area ratio between an area of outer zone and that of inner zone.
  • an average distance to a nearest heater within the outer zone significantly exceeds that of the inner zone.
  • an average distance to a nearest heater within the outer zone is between two and three times that of the inner zone.
  • an average distance to a nearest heater on a perimeter of the inner zone is at most substantially equal to that within inner zone.
  • an average distance to a nearest heater on the outer zone perimeter is equal to at most about twice that on the inner zone perimeter.
  • system further comprises at least one inner zone production well within inner zone and at least one outer zone production well within outer zone.
  • a production well spatial density in inner zone exceeds that of outer zone.
  • a production well spatial density in inner zone is equal to about three times of outer zone.
  • a majority of the outer zone heaters are arranged on a perimeter of the outer zone.
  • heaters are located at all polygon vertices of inner and outer zone perimeters.
  • heaters are located at all vertices of the OZS additional zone perimeter.
  • an average distance to a nearest heater within the outer zone is equal to between about two and about three times that of the inner zone.
  • an average distance to a nearest heater within the outer zone is equal to between two and three times that of the inner zone.
  • a heater spacing of the more outer zone is at least about twice that of the more inner zone.
  • the area ratio between respective more outer and more inner zones is about four, and a heater spacing of the more outer zone is about twice that of the more inner zone.
  • ratio between a heater spacing of the more outer zone and that of the more inner zone is substantially equal to square root of the area ratio between the more outer and the more inner zones of the zone pair.
  • the area ratio between respective areas enclosed by perimeters of the more outer zone and the more inner zone is at most six.
  • the area ratio between respective areas enclosed by perimeters of the more outer zone and the more inner zone is at most five.
  • the area ratio between respective areas enclosed by perimeters of the more outer zone and the more inner zone is at least 2.5.
  • a significant majority of the inner zone heaters are located away from outer zone perimeter.
  • a significant majority of the outer zone heaters are located away from a perimeter of outer-zone-surrounding (OZS) additional zone.
  • OZS outer-zone-surrounding
  • a heater spatial density of the more inner zone is equal to at least about twice that of the more outer zone.
  • a heater spatial density of the more inner zone is equal to at most about six times that of the more outer zone.
  • a centroid of the more inner zone is located in a central portion of the region enclosed by a perimeter of the more outer zone.
  • an average distance to a nearest heater in the more outer zone is between about two and about three times that of the less outer zone.
  • an average distance to a nearest heater in the more outer zone is between two and three times that of the less outer zone.
  • a centroid of inner zone is located in a central portion of the region enclosed by a perimeter of the outer zone.
  • the heater cell includes at least one inner zone production well located within the inner zone.
  • the heater cell includes at least one outer zone production well located within the outer zone.
  • the heater cell includes first and second outer zone production wells located within and on substantially on opposite sides of the outer zone.
  • a production well spatial density in the inner zone at least exceeds that of the outer zone.
  • an average heater spacing in outer zone is at least about twice that of inner zone.
  • the area ratio between respective areas enclosed by inner zone and outer zone perimeters is about four, and an average heater spacing in outer zone is about twice that of inner zone.
  • a spacing ratio between an average heater spacing of the outer zone and that of the inner zone is about equal to a square root of the area ratio between respective areas enclosed by the inner zone and outer zone perimeters.
  • a spacing ratio between an average heater spacing of the outer zone and that of the inner zone is about equal to a square root of the area ratio between respective areas enclosed by inner zone and outer zone perimeters.
  • a heater spatial density in inner zone is at least about twice that of outer zone.
  • a heater spatial density in inner zone is at least twice that of outer zone.
  • a heater spatial density in inner zone is at least about three times that of the outer zone.
  • a heater density ratio between a heater spatial densities in inner that of outer zones is substantially equal to a zone area ratio between an area of outer zone and that of inner zone.
  • an enclosed area ratio between an area enclosed by a perimeter of outer zone to that enclosed by a perimeter of inner zone is at most six or at most five and/or at least 2.5 or at least three or at least three.
  • an average distance to a nearest heater in the outer zone is between about two and about three times that of the inner zone.
  • an average distance to a nearest heater in the outer zone is between two and three times that of the inner zone.
  • an average distance to a nearest heater on the inner zone perimeter is substantially equal to that within inner zone.
  • an average distance to a nearest heater is at most four times that along the perimeter of inner zone.
  • an average distance to a nearest heater is at most three times that along the perimeter of inner zone.
  • an average distance to a nearest heater is at most about twice that along the perimeter of inner zone.
  • an average distance to a nearest heater significantly exceeds that among inner-perimeter heaters located on the perimeter of inner zone.
  • an average distance to a second nearest heater significantly exceeds that among inner-perimeter heaters located on the perimeter of inner zone.
  • the system includes a plurality of the heater cells, first and second of the heater cells having substantially the same area and sharing at least one common heater-cell-perimeter heater.
  • a third of the heater cells has substantially the same area as the first and second heater cells, the third heater cell sharing at least one common heater-cell-perimeter heater with the first heater cell, the second and third heater cells located substantially on opposite sides of the first heater cell.
  • the system includes a plurality of the heater cells, at least one of which is substantially surrounded by a plurality of neighboring heater cells.
  • a given heater cell of the heater cells is substantially surrounded by a plurality of neighboring heater cells and the given heater cell 608 shares a common heater-cell-perimeter heater with each of the neighboring heater cells.
  • inner zone heaters are distributed substantially uniformly throughout inner zone.
  • the heater cell is arranged so that within the outer zone, heaters are predominantly located on the outer zone perimeter.
  • At least one of the inner and outer perimeters is shaped like a regular hexagon, like a lozenge, or like a rectangle.
  • the inner and outer perimeters are like-shaped.
  • a majority of heaters are disposed on a triangular grid, hexagonal or rectangular grid.
  • a total number of inner zone heaters exceeds that of the outer zone.
  • a total number of inner zone heaters exceeds that of the outer zone by at least 50%.
  • At least five inner zone heaters are dispersed throughout the inner zone.
  • At least five or at least seven or at least ten outer zone heaters are located around a perimeter of outer zone.
  • At least one-third of at least one-half of inner zone heaters are not located on inner zone perimeter.
  • each of the inner zone and outer zone perimeters has an aspect ratio equal to most 2.5.
  • each of the inner zone and outer zone perimeters has an aspect ratio equal to least 10.
  • each of the inner zone and outer zone perimeters is shaped like a rectangular.
  • At least five or seven or nine heaters are distributed about the perimeter of inner zone and/or about the perimeter of the outer zone.
  • At least ten heaters are distributed throughout inner zone.
  • a majority of the heaters in inner zone are electrical heaters and a majority of the heaters in outer zone are molten salt heaters.
  • At least two-thirds or at least three-quarters of inner-zone heaters are electrical heaters and at least two-thirds of outer-zone heaters are molten salt heaters.
  • the system further includes control apparatus configured to regulate heater operation times so that, on average, heaters in outer zone operate above a one-half maximum power level for at least twice as long as the heaters in inner zone.
  • the system includes control apparatus configured to regulate heater operation times so that, on average, outer zone heaters operate above a one-half maximum power level for at least twice as long as the inner zone heaters.
  • control apparatus is configured so that on average, outer zone heaters operate above a one-half maximum power level for at least three times as long as the inner zone heaters.
  • an average inner-zone heater spacing is at most 20 meters or at most 10 meters or at most 5 meters.
  • an area of the inner zone is at most one square kilometer.
  • an area of the inner zone is at most 500 square meters.
  • the heaters are configured to induce pyrolysis throughout substantial entireties of both the inner and outer zones.
  • the heaters are configured to heat respective substantial entirety of the inner and outer regions to substantially the same uniform temperature.
  • a ratio between a standard deviation of the spacing and an average spacing is at most 0.2.
  • all heaters have substantially the same maximum power level and/or substantially the same diameter.
  • a ratio between the area of the inner zone and a square of an average distance to a nearest heater within the inner zone is at least 80 or at least 70 or at least 60 or at least 90.
  • At most 10% or at most 7.6% or at most 5% or at most 4% or at most 3% of a length of the outer zone perimeter are at most 10% or at most 7.6% or at most 5% or at most 4% or at most 3% of a length of the outer zone perimeter.
  • an average distance to a nearest heater is at most one-eighth or at most one-tenth or at most one-twelfth of a square root of an area of the inner zone.
  • At most 30% or at most 20% or at most 10% of the inner zone is displaced from a nearest heater by length threshold equal to at most one quarter of a square root of the inner zone.
  • At most 10% of the inner zone is displaced from a nearest heater by length threshold equal to at most one quarter of a square root of the inner zone.
  • the length threshold equals at most one fifth of a square root of the inner zone.
  • an aspect ratio of the inner and/or outer zone is at most four or most 3 or at most 2.5.
  • a ratio between a greater aspect ratio and a lesser aspect ratio is at most 1.5.
  • an isoperimetric quotient of perimeters, of the inner and/or outer zone is at least 0.4 or at least 0.5 or at least 0.6.
  • a perimeter of inner zone has a convex shape tolerance value of at most 1.2 or at most 1.1.
  • heaters are arranged within inner zone so that inner zone heaters are present on every 72 degree sector or every 60 degree sector thereof for any reference ray orientation.
  • FIG. 1 depicts a schematic view of an embodiment of a portion of the in situ heat treatment system for treating the hydrocarbon-containing formation.
  • FIGS. 2-3 , 8 - 14 , and 18 - 37 illustrate in-situ heater patterns in accordance with various examples.
  • FIGS. 4-7 describe illustrative production functions for a two-level heater cell.
  • FIGS. 15-17 illustrate various sub-surface heaters.
  • the following description generally relates to systems and methods for treating hydrocarbons in the formations. Such formations may be treated to yield hydrocarbon products, hydrogen, and other products.
  • an ‘about-tolerance-parameter’ governs an upper bound of the maximum permissible deviation between two quantities that are ‘about equal.’
  • the ‘about-tolerance-parameter’ is defined as the difference between the ‘quantity ratio’ defined in the previous paragraph and 1.
  • a value of the ‘about-tolerance-parameter’ is 0.3—i.e. the ‘quantity ratio’ of the previous paragraph is at most 1.3.
  • the ‘about-tolerance-parameter’ is 0.2 (i.e. the ‘quantity ratio’ of the previous paragraph is at most 1.2 or 1.1 or 1.05).
  • the ‘about-tolerance-parameter’ is a global parameter—when the about tolerance parameter is X then all quantities that are ‘about’ or ‘substantially’ equal to each other have a ‘quantity ratio’ of about 1+X.
  • heaters or heater wells
  • a centroid of a ‘candidate’ region e.g. an inner or outer or outer-zone-surrounding (OZS) additional zone
  • OZS outer-zone-surrounding
  • heaters are present, for every ‘reference ray orientation,’ within every 72 degree sector or on every 60 degree sector or on every 45 sector of the ‘candidate region.’
  • heaters are arranged ‘around’ a perimeter of a candidate region, then they are arranged ‘around’ the centroid of the candidate region and on a perimeter thereof.
  • An “aspect ratio” of a shape refers to a ratio between its longer dimension and its shorter dimension.
  • the term “automatically” means such systems, apparatus, and methods function in a certain way without the use of external control (for example, external controllers such as a controller with a temperature sensor and a feedback loop, PID controller, or predictive controller).
  • external controllers such as a controller with a temperature sensor and a feedback loop, PID controller, or predictive controller.
  • a “centroid” of an object or region refers to the arithmetic mean of all points within the object or region. Unless specified otherwise, the ‘object’ or ‘region’ for which a centroid is specified or computed actually refers to a two-dimensional cross section of an object or region (e.g. a region of the subsurface formation).
  • a ‘centroid’ of a ‘heater’ or of a heater well is a ‘centroid’ of its ‘cross section’ of the heater or the heater well—i.e. at a specific location. Unless specified otherwise, this cross section is in the plane in which a ‘heater pattern’ (i.e. for heaters and/or heater wells) is defined.
  • An object or region is “convex” if for every pair of points within the region or object, every point on the straight line segment that joins them is also within the region or object.
  • a closed curve e.g. a perimeter of a two-dimensional region
  • a closed curve is ‘convex’ if the area enclosed by the closed curve is convex.
  • a heater ‘cross section’ may vary along its central axis. Unless specified otherwise, a heater ‘cross section’ is the cross section in the plane in which a ‘heater pattern’ is defined. Unless specified otherwise, for a given heater pattern, the ‘cross sections’ of each of the heaters are all co-planar.
  • a ‘distance’ between a location and a heater is the distance between the location and a ‘centroid’ of the heater (i.e. a ‘centroid’ of the heater cross section in the plane in which a ‘heater pattern’ is defined).
  • the ‘distance between multiple heaters’ is the distance between their centroids.
  • a “formation” includes one or more hydrocarbon-containing layers, one or more non-hydrocarbon layers, an overburden, and/or an underburden.
  • Hydrocarbon layers refer to layers in the formation that contain hydrocarbons.
  • the hydrocarbon layers may contain non-hydrocarbon material and hydrocarbon material.
  • the “overburden” and/or the “underburden” include one or more different types of impermeable materials.
  • the overburden and/or underburden may include rock, shale, mudstone, or wet/tight carbonate.
  • the overburden and/or the underburden may include a hydrocarbon-containing layer or hydrocarbon-containing layers that are relatively impermeable and are not subjected to temperatures during in situ heat treatment processing that result in significant characteristic changes of the hydrocarbon-containing layers of the overburden and/or the underburden.
  • the underburden may contain shale or mudstone, but the underburden is not allowed to heat to pyrolysis temperatures during the in situ heat treatment process.
  • the overburden and/or the underburden may be somewhat permeable.
  • Formation fluids refer to fluids present in a formation and may include pyrolyzation fluid, synthesis gas, mobilized hydrocarbons, and water (steam). Formation fluids may include hydrocarbon fluids as well as non-hydrocarbon fluids.
  • the term “mobilized fluid” refers to fluids in a hydrocarbon-containing formation that are able to flow as a result of thermal treatment of the formation.
  • Produced fluids refer to fluids removed from the subsurface formation.
  • a “heat source” is any system for providing heat to at least a portion of a formation substantially by conductive and/or radiative heat transfer.
  • a heat source may include electric heaters such as an insulated conductor, an elongated member, and/or a conductor disposed in a conduit.
  • a heat source may also include systems that generate heat by burning a fuel external to or in a formation. The systems may be surface burners, downhole gas burners, flameless distributed combustors, and natural distributed combustors.
  • heat provided to or generated in one or more heat sources may be supplied by other sources of energy. The other sources of energy may directly heat a formation, or the energy may be applied to a transfer medium that directly or indirectly heats the formation.
  • one or more heat sources that are applying heat to a formation may use different sources of energy.
  • some heat sources may supply heat from electric resistance heaters, some heat sources may provide heat from combustion, and some heat sources may provide heat from one or more other energy sources (for example, chemical reactions, solar energy, wind energy, biomass, or other sources of renewable energy).
  • a chemical reaction may include an exothermic reaction (for example, an oxidation reaction).
  • a heat source may also include a heater that provides heat to a zone proximate and/or surrounding a heating location such as a heater well.
  • a “heater” is any system or heat source for generating heat in a well or a near wellbore region.
  • Heaters may be, but are not limited to, electric heaters, burners (e.g. gas burners), pipes through which hot heat transfer fluid (e.g. molten salt or molten metal) flows, combustors that react with material in or produced from a formation, and/or combinations thereof.
  • a ‘heater’ includes elongate portion having a length that is much greater than cross-section dimensions.
  • molten salt heater which heats the subsurface formation primarily by heat convection between molten salt flowing therein and the subsurface formation.
  • a ‘heater pattern’ describes relative locations of heaters in a plane of the subsurface formation.
  • Heavy hydrocarbons are viscous hydrocarbon fluids. Heavy hydrocarbons may include highly viscous hydrocarbon fluids such as heavy oil, tar, and/or asphalt. Heavy hydrocarbons may include carbon and hydrogen, as well as smaller concentrations of sulfur, oxygen, and nitrogen. Additional elements may also be present in heavy hydrocarbons in trace amounts. Heavy hydrocarbons may be classified by API gravity. Heavy hydrocarbons generally have an API gravity below about 20°. Heavy oil, for example, generally has an API gravity of about 10-20°, whereas tar generally has an API gravity below about 10°. The viscosity of heavy hydrocarbons is generally greater than about 100 centipoise at 15° C. Heavy hydrocarbons may include aromatics or other complex ring hydrocarbons.
  • Hydrocarbons are generally defined as molecules formed primarily by carbon and hydrogen atoms. Hydrocarbons may also include other elements such as, but not limited to, halogens, metallic elements, nitrogen, oxygen, and/or sulfur. Hydrocarbons may be, but are not limited to, kerogen, bitumen, pyrobitumen, oils, natural mineral waxes, and asphaltites. Hydrocarbons may be located in or adjacent to mineral matrices in the earth. Matrices may include, but are not limited to, sedimentary rock, sands, silicilytes, carbonates, diatomites, and other porous media. “Hydrocarbon fluids” are fluids that include hydrocarbons. Hydrocarbon fluids may include, entrain, or be entrained in non-hydrocarbon fluids such as hydrogen, nitrogen, carbon monoxide, carbon dioxide, hydrogen sulfide, water, and ammonia.
  • An “in situ conversion process” refers to a process of heating a hydrocarbon-containing formation from heat sources to raise the temperature of at least a portion of the formation above a pyrolysis temperature so that pyrolyzation fluid is produced in the formation.
  • An “in situ heat treatment process” refers to a process of heating a hydrocarbon-containing formation with heat sources to raise the temperature of at least a portion of the formation above a temperature that results in mobilized fluid, visbreaking, and/or pyrolysis of hydrocarbon-containing material so that mobilized fluids, visbroken fluids, and/or pyrolyzation fluids are produced in the formation.
  • an ‘isoperimeteric quotient’ of a closed curve is a ratio between: (i) the product of 4 ⁇ and an area closed by the closed curve; and (ii) the square of the perimeter of the closed curve.
  • Kerogen is a solid, insoluble hydrocarbon that has been converted by natural degradation and that principally contains carbon, hydrogen, nitrogen, oxygen, and sulfur. Coal and oil shale are typical examples of materials that contain kerogen.
  • Biten is a non-crystalline solid or viscous hydrocarbon material that is substantially soluble in carbon disulfide.
  • Oil is a fluid containing a mixture of condensable hydrocarbons.
  • this ‘threshold difference’ is at least one half of an inner zone average heater spacing.
  • “Production” of a hydrocarbon fluid refers to thermally generating the hydrocarbon fluid (e.g. from kerogen or bitumen) and removing the fluid from the sub-surface formation via a production well.
  • Pyrolysis is the breaking of chemical bonds due to the application of heat.
  • pyrolysis may include transforming a compound into one or more other substances by heat alone. Heat may be transferred to a section of the formation to cause pyrolysis.
  • “Pyrolyzation fluids” or “pyrolysis products” refers to fluid produced substantially during pyrolysis of hydrocarbons. Fluid produced by pyrolysis reactions may mix with other fluids in a formation. The mixture would be considered pyrolyzation fluid or pyrolyzation product.
  • “pyrolysis zone” refers to a volume of a formation (for example, a relatively permeable formation such as a tar sands formation) that is reacted or reacting to form a pyrolyzation fluid.
  • a ratio between (i) the greater of the two quantities MAX(QUANT 1 , QUANT 2 ) and (ii) the lesser of the two quantities MIN(QUANT 1 , QUANT 2 ) is at least 1.5. In some embodiments, this ratio is at least 1.7 or at least 1.9.
  • a ‘significant majority’ refers to at least 75%. In some embodiments, the significant majority may be at least 80% or at least 85% or at least 90%.
  • Superposition of heat refers to providing heat from two or more heat sources to a selected section of a formation such that the temperature of the formation at least at one location between the heat sources is influenced by the heat sources.
  • “Tar” is a viscous hydrocarbon that generally has a viscosity greater than about 10,000 centipoise at 15° C.
  • the specific gravity of tar generally is greater than 1.000.
  • Tar may have an API gravity less than 10°.
  • a “tar sands formation” is a formation in which hydrocarbons are predominantly present in the form of heavy hydrocarbons and/or tar entrained in a mineral grain framework or other host lithology (for example, sand or carbonate).
  • Examples of tar sands formations include formations such as the Athabasca formation, the Grosmont formation, and the Peace River formation, all three in Alberta, Canada; and the Faja a formation in the Orinoco belt in Venezuela.
  • “Thermally conductive fluid” includes fluid that has a higher thermal conductivity than air at standard temperature and pressure (STP) (0° and 101.325 kPa).
  • Thermal conductivity is a property of a material that describes the rate at which heat flows, in steady state, between two surfaces of the material for a given temperature difference between the two surfaces.
  • Thickness of a layer refers to the thickness of a cross section of the layer, wherein the cross section is normal to a face of the layer.
  • a “U-shaped wellbore” refers to a wellbore that extends from a first opening in the formation, through at least a portion of the formation, and out through a second opening in the formation.
  • the wellbore may be only roughly in the shape of a “V” or “U”, with the understanding that the “legs” of the “U” do not need to be parallel to each other, or perpendicular to the “bottom” of the “U” for the wellbore to be considered “U-shaped”.
  • “Upgrade” refers to increasing the quality of hydrocarbons. For example, upgrading heavy hydrocarbons may result in an increase in the API gravity of the heavy hydrocarbons.
  • “Visbreaking” refers to the untangling of molecules in fluid during heat treatment and/or to the breaking of large molecules into smaller molecules during heat treatment, which results in a reduction of the viscosity of the fluid.
  • Viscosity refers to kinematic viscosity at 40° unless otherwise specified. Viscosity is as determined by ASTM Method D445.
  • VGO or “vacuum gas oil” refers to hydrocarbons with a boiling range distribution between 343° and 538° at 0.101 MPa. VGO content is determined by ASTM Method D5307.
  • wellbore refers to a hole in a formation made by drilling or insertion of a conduit into the formation.
  • a wellbore may have a substantially circular cross section, or another cross-sectional shape.
  • wellbore and opening when referring to an opening in the formation may be used interchangeably with the term “wellbore.”
  • a formation may be treated in various ways to produce many different products. Different stages or processes may be used to treat the formation during an in situ heat treatment process.
  • one or more sections of the formation are solution mined to remove soluble minerals from the sections. Solution mining minerals may be performed before, during, and/or after the in situ heat treatment process.
  • the average temperature of one or more sections being solution mined may be maintained below about 120° C.
  • one or more sections of the formation are heated to remove water from the sections and/or to remove methane and other volatile hydrocarbons from the sections.
  • the average temperature may be raised from ambient temperature to temperatures below about 220° during removal of water and volatile hydrocarbons.
  • one or more sections of the formation are heated to temperatures that allow for movement and/or visbreaking of hydrocarbons in the formation.
  • the average temperature of one or more sections of the formation are raised to mobilization temperatures of hydrocarbons in the sections (for example, to temperatures ranging from 100° to 250°, from 120° to 240°, or from 150° to 230°).
  • one or more sections are heated to temperatures that allow for pyrolysis reactions in the formation.
  • the average temperature of one or more sections of the formation may be raised to pyrolysis temperatures of hydrocarbons in the sections (for example, temperatures ranging from 230° to 900°, from 240° to 400° or from 250° to 350°).
  • Heating the hydrocarbon-containing formation with a plurality of heat sources may establish thermal gradients around the heat sources that raise the temperature of hydrocarbons in the formation to desired temperatures at desired heating rates.
  • the rate of temperature increase through mobilization temperature range and/or pyrolysis temperature range for desired products may affect the quality and quantity of the formation fluids produced from the hydrocarbon-containing formation. Slowly raising the temperature of the formation through the mobilization temperature range and/or pyrolysis temperature range may allow for the production of high quality, high API gravity hydrocarbons from the formation. Slowly raising the temperature of the formation through the mobilization temperature range and/or pyrolysis temperature range may allow for the removal of a large amount of the hydrocarbons present in the formation as hydrocarbon product.
  • a portion of the formation is heated to a desired temperature instead of slowly heating the temperature through a temperature range.
  • the desired temperature is 300°, 325°, or 350° Other temperatures may be selected as the desired temperature.
  • Superposition of heat from heat sources allows the desired temperature to be relatively quickly and efficiently established in the formation.
  • Energy input into the formation from the heat sources may be adjusted to maintain the temperature in the formation substantially at a desired temperature.
  • Mobilization and/or pyrolysis products may be produced from the formation through production wells.
  • the average temperature of one or more sections is raised to mobilization temperatures and hydrocarbons are produced from the production wells.
  • the average temperature of one or more of the sections may be raised to pyrolysis temperatures after production due to mobilization decreases below a selected value.
  • the average temperature of one or more sections may be raised to pyrolysis temperatures without significant production before reaching pyrolysis temperatures.
  • Formation fluids including pyrolysis products may be produced through the production wells.
  • the average temperature of one or more sections may be raised to temperatures sufficient to allow synthesis gas production after mobilization and/or pyrolysis.
  • hydrocarbons may be raised to temperatures sufficient to allow synthesis gas production without significant production before reaching the temperatures sufficient to allow synthesis gas production.
  • synthesis gas may be produced in a temperature range from about 400° to about 1200°, about 500° to about 1100°, or about 550° to about 1000°
  • a synthesis gas generating fluid for example, steam and/or water
  • Synthesis gas may be produced from production wells.
  • Solution mining removal of volatile hydrocarbons and water, mobilizing hydrocarbons, pyrolyzing hydrocarbons, generating synthesis gas, and/or other processes may be performed during the in situ heat treatment process.
  • some processes may be performed after the in situ heat treatment process.
  • Such processes may include, but are not limited to, recovering heat from treated sections, storing fluids (for example, water and/or hydrocarbons) in previously treated sections, and/or sequestering carbon dioxide in previously treated sections.
  • FIG. 1 depicts a schematic view of an embodiment of a portion of the in situ heat treatment system for treating the hydrocarbon-containing formation.
  • the in situ heat treatment system may include barrier wells 1200 .
  • Barrier wells are used to form a barrier around a treatment area. The barrier inhibits fluid flow into and/or out of the treatment area.
  • Barrier wells include, but are not limited to, dewatering wells, vacuum wells, capture wells, injection wells, grout wells, freeze wells, or combinations thereof.
  • barrier wells 1200 are dewatering wells. Dewatering wells may remove liquid water and/or inhibit liquid water from entering a portion of the formation to be heated, or to the formation being heated.
  • the barrier wells 1200 are shown extending only along one side of heater sources 1202 , but the barrier wells typically encircle all heat sources 1202 used, or to be used, to heat a treatment area of the formation.
  • Heat sources 1202 are placed in at least a portion of the formation.
  • Heat sources 1202 may include heaters such as insulated conductors, conductor-in-conduit heaters, surface burners, flameless distributed combustors, and/or natural distributed combustors. Heat sources 1202 may also include other types of heaters. Heat sources 1202 provide heat to at least a portion of the formation to heat hydrocarbons in the formation. Energy may be supplied to heat sources 1202 through supply lines 1204 . Supply lines 1204 may be structurally different depending on the type of heat source or heat sources used to heat the formation. Supply lines 1204 for heat sources may transmit electricity for electric heaters, may transport fuel for combustors, or may transport heat exchange fluid that is circulated in the formation. In some embodiments, electricity for an in situ heat treatment process may be provided by a nuclear power plant or nuclear power plants. The use of nuclear power may allow for reduction or elimination of carbon dioxide emissions from the in situ heat treatment process.
  • the heat input into the formation may cause expansion of the formation and geomechanical motion.
  • the heat sources may be turned on before, at the same time, or during a dewatering process.
  • Computer simulations may model formation response to heating. The computer simulations may be used to develop a pattern and time sequence for activating heat sources in the formation so that geomechanical motion of the formation does not adversely affect the functionality of heat sources, production wells, and other equipment in the formation.
  • Heating the formation may cause an increase in permeability and/or porosity of the formation. Increases in permeability and/or porosity may result from a reduction of mass in the formation due to vaporization and removal of water, removal of hydrocarbons, and/or creation of fractures. Fluid may flow more easily in the heated portion of the formation because of the increased permeability and/or porosity of the formation. Fluid in the heated portion of the formation may move a considerable distance through the formation because of the increased permeability and/or porosity. The considerable distance may be over 1000 m depending on various factors, such as permeability of the formation, properties of the fluid, temperature of the formation, and pressure gradient allowing movement of the fluid. The ability of fluid to travel considerable distance in the formation allows production wells 1206 to be spaced relatively far apart in the formation.
  • Production wells 1206 are used to remove formation fluid from the formation.
  • production well 1206 includes a heat source.
  • the heat source in the production well may heat one or more portions of the formation at or near the production well.
  • the amount of heat supplied to the formation from the production well per meter of the production well is less than the amount of heat applied to the formation from a heat source that heats the formation per meter of the heat source.
  • Heat applied to the formation from the production well may increase formation permeability adjacent to the production well by vaporizing and removing liquid phase fluid adjacent to the production well and/or by increasing the permeability of the formation adjacent to the production well by formation of macro and/or micro fractures.
  • More than one heat source may be positioned in the production well.
  • a heat source in a lower portion of the production well may be turned off when superposition of heat from adjacent heat sources heats the formation sufficiently to counteract benefits provided by heating the formation with the production well.
  • the heat source in an upper portion of the production well may remain on after the heat source in the lower portion of the production well is deactivated. The heat source in the upper portion of the well may inhibit condensation and reflux of formation fluid.
  • the heat source in production well 1206 allows for vapor phase removal of formation fluids from the formation.
  • Providing heating at or through the production well may: (1) inhibit condensation and/or refluxing of production fluid when such production fluid is moving in the production well proximate the overburden, (2) increase heat input into the formation, (3) increase production rate from the production well as compared to a production well without a heat source, (4) inhibit condensation of high carbon number compounds (C 6 hydrocarbons and above) in the production well, and/or (5) increase formation permeability at or proximate the production well.
  • Subsurface pressure in the formation may correspond to the fluid pressure generated in the formation. As temperatures in the heated portion of the formation increase, the pressure in the heated portion may increase as a result of thermal expansion of in situ fluids, increased fluid generation and vaporization of water. Controlling rate of fluid removal from the formation may allow for control of pressure in the formation. Pressure in the formation may be determined at a number of different locations, such as near or at production wells, near or at heat sources, or at monitor wells.
  • Formation fluid may be produced from the formation when the formation fluid is of a selected quality.
  • the selected quality includes an API gravity of at least about 20°, 30°, or 40°.
  • Inhibiting production until at least some hydrocarbons are mobilized and/or pyrolyzed may increase conversion of heavy hydrocarbons to light hydrocarbons. Inhibiting initial production may minimize the production of heavy hydrocarbons from the formation. Production of substantial amounts of heavy hydrocarbons may require expensive equipment and/or reduce the life of production equipment.
  • hydrocarbons in the formation may be heated to mobilization and/or pyrolysis temperatures before substantial permeability has been generated in the heated portion of the formation.
  • An initial lack of permeability may inhibit the transport of generated fluids to production wells 1206 .
  • fluid pressure in the formation may increase proximate heat sources 1202 .
  • the increased fluid pressure may be released, monitored, altered, and/or controlled through one or more heat sources 1202 .
  • selected heat sources 1202 or separate pressure relief wells may include pressure relief valves that allow for removal of some fluid from the formation.
  • pressure generated by expansion of mobilized fluids, pyrolysis fluids or other fluids generated in the formation may be allowed to increase although an open path to production wells 1206 or any other pressure sink may not yet exist in the formation.
  • the fluid pressure may be allowed to increase towards a lithostatic pressure.
  • Fractures in the hydrocarbon-containing formation may form when the fluid approaches the lithostatic pressure.
  • fractures may form from heat sources 1202 to production wells 1206 in the heated portion of the formation.
  • the generation of fractures in the heated portion may relieve some of the pressure in the portion.
  • Pressure in the formation may have to be maintained below a selected pressure to inhibit unwanted production, fracturing of the overburden or underburden, and/or coking of hydrocarbons in the formation.
  • pressure in the formation may be varied to alter and/or control a composition of formation fluid produced, to control a percentage of condensable fluid as compared to non-condensable fluid in the formation fluid, and/or to control an API gravity of formation fluid being produced. For example, decreasing pressure may result in production of a larger condensable fluid component.
  • the condensable fluid component may contain a larger percentage of olefins.
  • pressure in the formation may be maintained high enough to promote production of formation fluid with an API gravity of greater than 20°. Maintaining increased pressure in the formation may inhibit formation subsidence during in situ heat treatment. Maintaining increased pressure may reduce or eliminate the need to compress formation fluids at the surface to transport the fluids in collection conduits to treatment facilities.
  • Maintaining increased pressure in a heated portion of the formation may surprisingly allow for production of large quantities of hydrocarbons of increased quality and of relatively low molecular weight. Pressure may be maintained so that formation fluid produced has a minimal amount of compounds above a selected carbon number.
  • the selected carbon number may be at most 25, at most 20, at most 12, or at most 8.
  • Some high carbon number compounds may be entrained in vapor in the formation and may be removed from the formation with the vapor. Maintaining increased pressure in the formation may inhibit entrainment of high carbon number compounds and/or multi-ring hydrocarbon compounds in the vapor.
  • High carbon number compounds and/or multi-ring hydrocarbon compounds may remain in a liquid phase in the formation for significant time periods. The significant time periods may provide sufficient time for the compounds to pyrolyze to form lower carbon number compounds.
  • Generation of relatively low molecular weight hydrocarbons is believed to be due, in part, to autogenous generation and reaction of hydrogen in a portion of the hydrocarbon-containing formation.
  • maintaining an increased pressure may force hydrogen generated during pyrolysis into the liquid phase within the formation.
  • Heating the portion to a temperature in a pyrolysis temperature range may pyrolyze hydrocarbons in the formation to generate liquid phase pyrolyzation fluids.
  • the generated liquid phase pyrolyzation fluids components may include double bonds and/or radicals.
  • Hydrogen (H 2 ) in the liquid phase may reduce double bonds of the generated pyrolyzation fluids, thereby reducing a potential for polymerization or formation of long chain compounds from the generated pyrolyzation fluids.
  • H 2 may also neutralize radicals in the generated pyrolyzation fluids.
  • H 2 in the liquid phase may inhibit the generated pyrolyzation fluids from reacting with each other and/or with other compounds in the formation.
  • Formation fluid produced from production wells 1206 may be transported through collection piping 1208 to treatment facilities 1210 .
  • Formation fluids may also be produced from heat sources 1202 .
  • fluid may be produced from heat sources 1202 to control pressure in the formation adjacent to the heat sources.
  • Fluid produced from heat sources 1202 may be transported through tubing or piping to collection piping 1208 or the produced fluid may be transported through tubing or piping directly to treatment facilities 1210 .
  • Treatment facilities 1210 may include separation units, reaction units, upgrading units, fuel cells, turbines, storage vessels, and/or other systems and units for processing produced formation fluids.
  • the treatment facilities may form transportation fuel from at least a portion of the hydrocarbons produced from the formation.
  • the transportation fuel may be jet fuel, such as JP-8.
  • Formation fluid may be hot when produced from the formation through the production wells.
  • Hot formation fluid may be produced during solution mining processes and/or during in situ heat treatment processes.
  • electricity may be generated using the heat of the fluid produced from the formation.
  • heat recovered from the formation after the in situ process may be used to generate electricity.
  • the generated electricity may be used to supply power to the in situ heat treatment process.
  • the electricity may be used to power heaters, or to power a refrigeration system for forming or maintaining a low temperature barrier.
  • Electricity may be generated using a Kalina cycle, Rankine cycle or other thermodynamic cycle.
  • the working fluid for the cycle used to generate electricity is aqua ammonia.
  • FIGS. 2A-2E illustrate a pattern of heaters 220 within a cross section (e.g. a horizontal or vertical or slanted cross section) of a hydrocarbon-bearing subsurface formation such as oil shale, tar sands, coals, bitumen-containing carbonates, gibsonite, or heavy oil-containing diatomite).
  • each of the heaters e.g. within heater wells
  • each dot 220 in FIGS. 2A-2D represents a location of a cross section of the respective elongate heater in the plane defined by the subsurface cross section.
  • the heater spatial pattern of FIGS. 2A-2D may occur at any depth within the subsurface formation, for example, at least 50 meters or at least 100 meters or at least 150 meters or at least 250 meters beneath the surface, or more.
  • heaters 220 are respectively disposed at relatively high and low spatial densities (and relatively short and long heater spacings) within nested inner 210 and outer 214 zones of the cross section of the hydrocarbon-bearing formation.
  • (i) nineteen inner zone heaters 226 are disposed at a relatively high density (and relatively short spacings between neighboring heaters) both within an inner zone 210 and around a perimeter 204 of the inner zone 210 (i.e.
  • outer perimeter referred to as an ‘inner perimeter’
  • twelve outer zone 228 heaters are arranged a relatively low density (and relatively long spacings between neighboring heaters) in outer zone 214 so as to be distributed around a perimeter 208 of outer zone 214 .
  • outer zone 214 within outer zone 214 , (i) all outer zone heaters are distributed around the perimeter 208 of outer zone 214 , and (ii) the region between the inner 204 and outer 208 perimeters is relatively free of heaters.
  • heater patterns are defined within a two-dimensional cross-section of the subsurface formation
  • the terms ‘inner zone’ 210 and ‘outer zone’ 214 refer to portions of the two-dimensional cross section of the subsurface formation.
  • various spatial properties related to heater location such as heater spacing, density, and ‘distance to heater’ are also defined within a two-dimensional planar cross-section of the formation.
  • the ‘inner zone’ 210 refers to the entire area enclosed by a perimeter 204 thereof.
  • the ‘outer zone’ 214 refers to the entire area, (i) outside of inner zone 210 that is (ii) enclosed by a perimeter 208 outer zone 214 .
  • the heater patterns illustrated in the non-limiting example of FIGS. 2A-2E are useful for minimizing and/or substantially minimizing a number of heaters 220 required to rapidly reach a relatively-sustained substantially steady-state production rate of hydrocarbon fluids in the subsurface formation.
  • the subsurface formation within the smaller inner zone 210 heats up relatively quickly, due to the high spatial density and short spacing of heaters therein.
  • This high heater spatial density may expedite production of hydrocarbons within inner zone 210 during an earlier phase of production when the average temperature in the inner zone 210 exceeds (e.g. significantly exceeds) that of the outer zone 214 .
  • the combination of (i) heat provided by outer zone heaters; and (ii) outward flow of thermal energy from inner zone 210 to outer zone 214 may heat the outer zone 214 .
  • two distinct ‘production peaks’ may be observed—an earlier inner zone production peak 310 and a later outer zone production peak 330 .
  • these production peaks collectively contribute to an ‘overall’ hydrocarbon production rate within the ‘combined’ region (i.e. the combination of inner 210 and outer 214 regions) that (i) ramps up relatively quickly due to the inner zone peak (i.e. has a ‘fast rise time’) and (ii) is sustained at a near-steady rate for an extended period of time.
  • the twelve heaters located on the ‘inner hexagon’ 204 are inner zone heaters 226 .
  • the ‘outer zone perimeter 208 ’ or ‘outer perimeter 208 ’ which forms a boundary between the outer zone 214 and ‘external locations’ outside of the outer zone is considered part of outer zone 214 .
  • the terms ‘inner zone perimeter 204 ’ and ‘inner perimeter 204 ’ are used interchangeably and have the same meaning; the terms ‘outer zone perimeter 208 ’ and ‘outer perimeter 208 ’ are used interchangeably and have the same meaning.
  • inner 210 and outer 214 zones are (i) nested so that outer zone 214 surrounds inner zone 210 , (ii) share a common centroid location 298 , and (iii) have like-shaped perimeters 204 , 208 .
  • inner 204 and outer 208 zone perimeters are both regular hexagons.
  • inner zone heaters are 226 dispersed throughout the inner zone at exactly a uniform spacing s.
  • inner zone heaters 226 are uniformly arranged on an equilateral triangular grid throughout the inner zone 210 —a length of each triangle side is s.
  • an ‘average heater spacing’ is approximately double that of the inner zone.
  • heaters are distanced from each other by 2s.
  • a third heater on inner perimeter 206 is distanced from both heaters of the pair of adjacent heaters by 2s.
  • twelve outer zone heaters are uniformly distributed around regular hexagonally-shaped outer perimeter 208 so that adjacent heaters on outer perimeter 208 (i) are separated by a separation distance 2s; and (ii) subtend an angle equal to 30 degrees relative to the center 298 of outer zone.
  • An area enclosed by inner perimeter 204 i.e. an area of inner zone 210
  • an area enclosed by outer perimeter 208 i.e. an area of the ‘combined area’ that is the sum of inner 210 and outer 214 zones
  • An area ratio between areas of the outer 210 and inner 214 zones is three.
  • the heater spatial density in inner zone 210 significantly exceeds that within outer zone 214 .
  • the density within inner zone 210 of FIGS. 2A-2E is three times that of outer zone 214 .
  • the heater pattern includes a total of 31 heaters. If the heaters were all drilled at the average inner zone 210 spacing, a total of 61 heaters would be required. Compared to drilling all of the heaters at an average spacing within inner zone 210 , the pattern of FIGS. 2A-2E requires only about half as many heaters.
  • the inner zone and outer zone perimeters 204 , 208 are both regularly-hexagonally shaped.
  • the shapes of the inner and/or outer zone perimeters 204 , 208 are defined by the locations of the heaters themselves—for example, the heater locations may define vertex locations for a polygon-shaped perimeter.
  • inner zone 210 may be defined by a ‘cluster’ of heaters in a relatively high-spatial-density region surrounded by a region where the density of heaters is significantly lower.
  • the edge of this cluster of heaters where an observable ‘density drop’ may define the border (i.e. inner zone perimeter 204 ) between (i) the inner zone 210 where heaters are arranged in a ‘cluster’ at a relatively high density and (ii) the outer zone 214 .
  • the perimeter of outer zone 208 may be defined by a ‘ring’ (i.e. not necessarily circularly-shaped) of heaters outside of inner zone 210 distributed around a centroid of outer zone 214 .
  • This ring may be relatively ‘thin’ compared to the cluster of heaters that form the inner zone 210 .
  • a local density within this ‘ring’ of heaters defining outer zone perimeter 208 is relatively high compared to locations adjacent to the ring—i.e. locations within outer zone 214 (i.e. ‘internal locations’ within outer zone 214 away from inner-zone 204 and outer-zone 208 perimeters) and outside of outer zone 214 .
  • the inner and/or outer zone perimeters 204 , 208 are polygon shaped and are defined such that heaters (i.e. a centroid thereof in a cross-section of the subsurface where the heater pattern is defined) are located at all polygon vertices of perimeters 204 , 208 .
  • any heater pattern disclosed herein may also be a heater well pattern.
  • the perimeters 204 , 208 may be defined such that heater well centroids i.e. in a cross-section of the subsurface where the heater pattern is defined) are located at all polygon vertices of perimeters 204 , 208 .
  • heaters are labeled (i.e. for the non-limiting example of FIGS. 2A-2E ) as inner zone heaters 226 or outer zone heaters 228 .
  • 19 heaters are inner zone heaters 226 and 12 heaters are outer zone heaters 228 .
  • heaters may be labeled (i.e. for the non-limiting example of FIGS.
  • inner 210 and outer 214 zones are like-shaped and shaped as regular hexagons.
  • a ‘characteristic length’ within inner 210 or outer 214 zones may be defined relative to a ‘characteristic length’ within inner 210 or outer 214 zones.
  • a ‘characteristic length’ within a region of a cross-section of the subsurface formation is a square root of an area of the region.
  • a ‘characteristic inner zone length’ is a square root of an area of inner zone 210
  • a ‘characteristic inner zone length’ is a square root of an area of outer zone 214 .
  • the area of inner zone 210 is 6 ⁇ square root over (3) ⁇ s 2 so that the ‘characteristic inner zone length’ is approximately 3.2s; (ii) an area of outer zone 214 is three times that of inner zone 210 so that the ‘characteristic outer zone length’ is approximately 5.6s.
  • heaters are typically within heater wells (e.g. having elongate sections), any heater spatial pattern (and any feature or combination of feature(s)) disclosed herein may also be a heater well pattern.
  • One salient feature of the pattern/arrangement of FIG. 2D is the presence of production wells both within inner 210 and outer 214 zones.
  • heater patterns providing this feature may be useful for expediting a rate of conversion of kerogen and/or bitumen of the hydrocarbon-bearing formation into hydrocarbon fluids within inner zone 210 so that an inner zone production peak 310 occurs in an earlier stage of production, and an outer zone production peak 330 only occurs after a delay.
  • Inner zone heaters 226 and outer zone heaters 228 are distributed ‘around’ respective centroids 298 , 296 of inner 210 and outer 214 zones. As will be discussed below (see FIGS. 26A-26B ), when heaters are distributed ‘around’ a centroid then for every orientation of a ‘reference ray’ starting at an ‘origin’ at the location of the centroid ( 296 or 298 ), at least one heater is located (i.e. the heater cross section centroid is located) in every quadrant (i.e. every 90 degree sector) defined by the origin/centroid ( 296 or 298 ).
  • heaters are arranged within inner 210 and/or outer 214 zones so that inner zone heaters 226 or outer zone heaters 228 are present on every 72 degree sector or on every 60 degree sector or on every 45 degree sector of inner or outer zones for every reference ray orientation.
  • Outer zone heaters 228 are predominantly located on or near the outer zone perimeter 208 .
  • the relatively high density of heaters in inner zone 210 causes an outward flow of thermal energy from inner zone 210 into outer zone 214 .
  • Arrangement of outer zone heaters 228 so that they are predominantly located on or near the outer zone perimeter 208 may facilitate the ‘inward flow’ of thermal energy so as to at least partly ‘balance’ the outward flow of thermal energy into outer zone 214 from inner zone 210 .
  • heaters are deployed at most sparsely in the interior portion of outer zone 210 away from inner and outer zone perimeters 204 , 208 . This may be useful for reducing a number of heaters required to produce hydrocarbon fluids in a required manner. Furthermore, the relative lack of heaters within the ‘middle portion’ of outer zone 210 (i.e. distanced from both perimeters 204 , 208 ) may delay production of fluids from this middle portion of outer zone 210 and within outer zone 210 as a whole. As will be discussed below, with reference to FIGS. 4-7 , this delay may be useful for producing hydrocarbon fluids in a manner where a significant production rate (e.g. at least half of a maximum production rate) is sustained for a relatively extended period of time.
  • a significant production rate e.g. at least half of a maximum production rate
  • a ratio between areas enclosed by the outer 208 and inner 204 perimeters is at least 3 or at least 3.5 and/or at most 10 or at most 9 or at most 8 or at most 7 or at most 6 or at most 5 or at most 4.5 and/or about 4. In the examples of FIGS. 2-4 and 7 - 9 , this ratio is exactly four. In some embodiments, arranging heaters according to any of these ratios may be useful for producing hydrocarbons so that an overall rate of production ramps up relatively rapidly (i.e. short rise time) while is sustained for a relatively extended period of time.
  • this ratio is too small, then the amount of time that the rate of production is sustained may be too short and/or the thermal efficiency of the heater pattern may be reduced due to a reduction in the re-use of thermal energy from inner zone heaters within outer zone 210 . If this ratio is too large, this may, for example, cause a dip in production after hydrocarbon fluids are rapidly produced within inner zone 210 .
  • centroid 296 of inner zone 210 is located in a central portion of the region enclosed by outer zone perimeter 208 —upon visual inspection of the heater patterns of FIGS. 2-11 , it is clear that this is true for all of these heater patterns. In some embodiments, substantially centering the inner zone within outer zone is useful for ensuring that a higher fraction of thermal energy from heaters 226 within inner zone 210 is re-used within outer zone 214 , thus increasing the overall thermal efficiency of the heater pattern. Unless specified otherwise, when centroid 296 of inner zone 210 is located in a central portion of the region enclosed by outer zone perimeter 208 , centroid 296 of inner zone 210 is in the inner third of a region enclosed by outer zone perimeter 208 . In some embodiments, centroid 296 of inner zone 210 is in the inner quarter or inner fifth or inner sixth or inner tenth.
  • this threshold distance is at least: (i) at least two-thirds of the inner zone average heater spacing and/or (ii) at least the inner zone average heater spacing or (iii) at least an average distance within inner zone (i.e. averaged over all locations within inner zone 210 ) to a nearest heater; and/or (ii) at least three times (or at least four times or at least five times) the square root of the area of the inner zone divided the number of inner zone heaters.
  • the square root of the area of the inner zone is 3.2s and the number of inner zone heaters is 19, so four times the square root of the area of the inner zone is about 0.51s.
  • the square root of the area of the inner zone is 3.8s and the number of inner zone heaters is 25, so four times the square root of the area of the inner zone is about 0.44s.
  • (G) Perimeters 204 , 208 of inner 210 and/or outer 214 zones are convex or substantially convex—the skilled artisan is directed to the definition of ‘substantially convex’ described below with reference to FIG. 29 . In some embodiments, this may be useful for facilitating outward flow of heat generated by inner zone heaters located at or near the perimeter 204 of inner zone 210 —e.g. so that heat from inner zone heaters located at or near inner zone perimeter 204 flows outwards into outer zone 214 and toward outer zone perimeter 208 rather than flowing inwards towards a centroid 296 of inner zone 210 . In some embodiments, this increases the thermal efficiency of the heater pattern. In some embodiments, a candidate shape is ‘substantially convex’ if an area enclosed by a minimally enclosed convex shape exceeds the area of the candidate shape by at most 20% or at most 10% or at most 5%.
  • An isoperimetric quotient of perimeters 204 , 208 of the inner 210 and/or outer 214 zone is at least 0.4 or at least about 0.5 or at least 0.6.
  • an ‘isoperimetric quotient’ of a closed curve is defined as the isoperimetric coefficient of the area enclosed by the closed curve, i.e.
  • P is the length of the perimeter of the closed curve
  • A is the area enclosed by the closed curve (e.g. an area of inner zone 210 for the ‘closed curve’ defined by perimeter 204 or the sum of the areas of inner 210 and outer 214 zones for the ‘closed curve’ defined by perimeter 208 ).
  • An ‘aspect ratio’ of perimeter 204 of inner 210 and/or of perimeter 208 of outer 214 zone is at most 5 or at most 4.5 or at most 4 or at most 3.5 or at most 3 or at most 2.5 or at most 2.0 or at most 1.5.
  • An “aspect ratio” of a shape refers to a ratio between its longer dimension and its shorter dimension.
  • the inner and outer zones have a similar and/or relatively low aspect ratio that may be useful for efficient re-use of inner-zone-generated thermal energy within outer zone′ 214 and/or for obtaining a production curve exhibiting a relatively fast rise-time with sustained substantial production rate.
  • Perimeters 204 , 208 of inner 210 and/or outer 214 zones have common shape characteristics.
  • inner and outer zone perimeters 204 , 208 are like-shaped. This is not a requirement.
  • IPQ INNER is the isoperimeter quotient of inner zone 210
  • IPQ OUTER is the isoperimeter quotient of outer zone 214
  • MAX(IPQ INNER , IPQ OUTER ) is the greater of IPQ INNER and IPQ OUTER
  • MIN(IPQ INNER , IPQ OUTER ) is the lesser of IPQ INNER and IPQ OUTER
  • a ratio is the isoperimeter quotient of inner zone 210
  • IPQ OUTER is the isoperimeter quotient of outer zone 214
  • MAX(IPQ INNER , IPQ OUTER ) is the greater of IPQ INNER and IPQ OUTER
  • MIN(IPQ INNER , IPQ OUTER ) is the lesser of IPQ IN
  • heaters are ‘distributed substantially uniformly’ in inner 210 and/or outer 214 outer zone. This may allow for more efficient heating of inner zone 210 .
  • visual inspection of a ‘heater layout’ diagram describing positions of heater cross sections is sufficient to indicate when heaters are ‘distributed substantially uniformly’ throughout one or more of the zone(s).
  • heaters may be distributed so as to provide a relatively low ‘heater standard deviation spacing’ relative to a ‘heater average spacing in one or more of the zone(s).
  • any area of the subsurface formation e.g. within inner zone 210 or outer zone 214 , there are a number of ‘neighboring heater spacings’ within the area of the formation—for example, in FIG. 22C (i.e. there are 36 spacings in outer zone 214 (i.e. 30 of the spacings have values of 2a and 6 of the spacings have values of ⁇ square root over (3) ⁇ a) and there are 32 spacings in inner zone 210 (i.e. all 36 of the spacings have a value of a).
  • the average spacing in inner zone 210 is exactly a while the average spacing in outer zone 214 is
  • a quotient of the standard deviation spacing and the average spacing is about 0.05.
  • the average spacing is
  • a quotient of the standard deviation spacing and the average spacing is about 0.072.
  • a quotient between a standard deviation spacing and an average spacing is at most 0.5 or at most 0.4 or at most 0.3 or at most 0.2 or at most 0.1.
  • heaters are dispersed throughout inner zone 214 rather than being limited to specific locations within inner zone (e.g. perimeter 204 )—upon visual inspection of the heater patterns of FIGS. 2-3 , it is clear that this feature is true for all of these heater patterns.
  • the heaters are distributed according to an average heater spacing that is ‘small’ compared to some ‘characteristic length’ of inner zone 210 —for example, an average heater spacing within inner zone 210 may be at most one-half or at most two-fifths or at most one-third or at most one-quarter of the square root of an area of inner zone 210 .
  • This ‘close heater’ spacing relative to a characteristic length of inner zone 210 may be useful for outwardly directing thermal energy from inner zone heaters so as to facilitate heat flow into outer zone 214 .
  • a ratio between (i) a product of a number of inner zone heaters 226 and a square of the average spacing in the inner zone and (ii) an area of inner zone 210 is at least 0.75 or at least 1 or at least 1.25 or at least 1.5.
  • At least 10% or at least 20% or at least 30% or at least 40% or at least 50% of inner zone heaters are ‘interior of inner zone heaters 230 ’ located within inner zone 210 away from inner zone perimeter 204 ;
  • One or more production wells located in inner 210 and/or outer 214 zones are arranged within inner and/or outer zones to efficiently recovering hydrocarbon fluids from the subsurface.
  • locating production well(s) in inner zone 210 is useful for quickly removing hydrocarbon fluids located therein.
  • the angle ⁇ LOC PROD — WELL IZ1 CENT IZ LOC PROD — WELL IZ2 subtended by the locations of the two production wells through inner zone centroid CENT IZ 298 is at least 90 degrees (or at least 100 degrees or at least 110 degrees or at least 120 degrees).
  • a majority or a substantial majority of heaters within inner zone 214 are distributed on a triangular or rectangular (e.g. square) or hexagonal pattern. In some embodiments, this allows for more efficient heating of inner zone 210 ;
  • D spacing is the spacing between adjacent heater wells
  • D well is the diameter of the heater wells
  • c is a proportionality constant that depends on the thermal conductivity and thermal diffusivity of the formation.
  • heaters are deployed at a relatively high density within inner zone 210 and at a relatively low density within inner zone 214 .
  • an ‘average spacing between neighboring heaters’ within the outer zone 214 significantly exceeds that of the inner zone 210 .
  • the amount of time required to pyrolyze kerogen (and/or to carry out any other in-situ hydrocarbon production process—for example, producing hydrocarbon fluids from tar sands) is substantially less in the inner zone 210 than in the outer zone due to the relatively high heater density and/or relatively short heater spacing in the inner zone 210 .
  • FIGS. 4-7 present illustrative production functions describing a time dependence of the hydrocarbon production rate in a subsurface hydrocarbon formation according to one illustrative example. It is expected that a production function sharing one or more feature(s) with that illustrated in FIGS. 4-7 may be observed when producing hydrocarbons using a two-level heater cell—for example, a two-level heater cell having feature(s) similar that of FIG. 2D .
  • FIGS. 4-7 A number of illustrative hydrocarbon production functions related to two-level heater cells are presented in FIGS. 4-7 .
  • temperatures in the inner zone 210 rise more rapidly than in the outer zone 214 , so as to expedite the production of hydrocarbons in the inner zone 210 .
  • a ‘hydrocarbon production temperature’ e.g. a pyrolysis temperature
  • an inner zone production rate peak 310 occurs before an outer zone production rate peak 330 .
  • a production dip may be observed.
  • the production rate peak occurs when a particular zone or region reaches ‘hydrocarbon production temperature’—e.g. a pyrolysis temperature and/or a temperature where fluids are mobilized in a heavy oil formation and/or bitumen-rich formation and/or tar-sands formation.
  • hydrocarbon production temperature e.g. a pyrolysis temperature and/or a temperature where fluids are mobilized in a heavy oil formation and/or bitumen-rich formation and/or tar-sands formation.
  • a production peak 330 of function 358 describing production in outer zone 214 occurs after a production peak 310 of function 354 describing production in inner zone 210 .
  • zones 210 , 214 which may be written as ⁇ Zone 1 ,Zone 2 ⁇ where Zone 1 is the innermost zone (or inner zone 210 ) and Zone 2 is the first zone outside of the innermost zone (or zone 214 ) that sequential production peaks ⁇ Peak 1 ,Peak 2 ⁇ (labeled respectively as 310 and 330 in FIG. 4 ) are observed respectively at times ⁇ t 1 , t 2 ⁇ .
  • An amount of time required to ramp up to the i th peak Peak i is t i .
  • the amount of time required to ramp up to the production peak Peak 1 (labeled as 310 in FIG. 12 ) for the innermost zone Zone 1 (i.e. inner zone 210 ) is (t 1 ⁇ t 0 ); and (ii) the amount of time required to ramp up to the production peak Peak 2 (labeled as 330 in FIG. 4 ) for the zone Zone 2 (i.e. outer zone 214 ) immediately outside of the innermost zone 210 is (t 2 ⁇ t 0 ).
  • this ramp-up time ratio is about three. In some embodiments, this peak time ramp-up ratio is about equal to a zone area ratio between areas of the more outer zone Zone 2 (i.e. outer zone 214 ) and the more inner zone Zone 1 (i.e. inner zone 210 ). For the example of FIG. 2D , a ‘zone area ratio’ between (i) an area of the more outer zone Zone 2 (i.e. outer zone 214 ); and (ii) an area of the more inner zone Zone 1 (i.e. inner zone 210 ) is three. Thus, in some embodiments, for a more inner zone Zone 1 (e.g. inner zone 210 ) and a more outer zone Zone 2 (i.e.
  • a ‘zone area ratio’ thereof is substantially equal to a ‘ramp-up time’ ratio for times of their production Peak 1 peaks and Peak 2 .
  • this is true at least in part because a reciprocal of a ‘density ratio’ between heater densities in the more outer (i.e. outer zone 214 ) and the more inner zone (i.e. outer zone 214 ) is also equal to the ramp-up is also equal to about three.
  • FIGS. 4 and 7 Also illustrated in FIGS. 4 and 7 is the overall or total rate of hydrocarbon fluid in the ‘combined region’ (i.e. the area enclosed within outer zone perimeter 208 —this is the combination of inner 210 and outer 214 zones), described by curve 350 having a production rate peak 320 which occurs immediately before that 330 of outer zone 2140 .
  • a ratio SPT/RT between a (i) a sustained production time SPT (i.e. the amount of time that the production rate is contiuously sustained above one-half of a maximum production rate level for the combined region) and (ii) a rise time RT for the combined region is relatively ‘large’—e.g. at least four-thirds or at least three-halves or at least two.
  • a ‘half-maximum hydrocarbon fluid production rate rise time’ or ‘half-maximum rise time’ is the amount of time required for hydrocarbon fluid production to reach one-half of its maximum
  • the ‘half-maximum hydrocarbon fluid production rate sustained production time’ or the ‘half-maximum sustained production time’ is the amount of time where the hydrocarbon fluid production rate is sustained at least one-half of its maximum.
  • FIGS. 5 , 6 and 7 respectively show production rate curves 354 , 358 and 350 for the inner 210 , outer 214 and ‘total’ zones (i.e. the combination of inner and outer zones).
  • a production dip (e.g. occurring after peak 310 and before peak 330 ) is illustrated.—In some embodiments, such a production dip (or any other production dip) may be observed even within a time period of a ‘half-maximum hydrocarbon fluid production rate sustained production time’ as long as the production rate remains above one-half of a maximum rate throughout the time period of the ‘half-maximum hydrocarbon fluid production rate sustained production time’.
  • a relatively large SPT/RT ratio may describe situations where, (i) hydrocarbon fluids are produced (e.g. from kerogen or from bitumen) and removed from the subsurface after only a minimal delay, allowing a relatively rapid ‘return’ on investment in the projection while using substantially only a minimal number of heaters; and (ii) hydrocarbon fluids are produced for a relatively extended period of time at a relatively constant rate. Because hydrocarbon fluids are produced at a relatively constant rate, a ratio between a peak hydrocarbon production rate and an average hydrocarbon production rate for the combined region, is relatively small. In some embodiments, the amount of infrastructure required for hydrocarbon fluid production and/or processing is determined at least in part by the maximum production rate. In some embodiments, a relatively low ratio between a peak hydrocarbon production rate and an average hydrocarbon production rate for the combined region may reduce the amount of infrastructure required for fluid production and/or processing with a minimal number, or near minimal number, of pre-drilled heater wells.
  • FIG. 14A Also illustrated in FIG. 14A are the earlier 980 and later 984 stages of production. During the earlier 980 stage of production, hydrocarbon fluids are produced primarily in inner 210 zone; during the later 984 stage of production, hydrocarbon fluids are produced primarily in outer 214 zone.
  • FIG. 12E is a flowchart of a method for producing hydrocarbon fluids.
  • step S 1551 wells are drilled into the subsurface formation.
  • step S 1555 heaters are installed in the heater wells—it is appreciated that some heaters may be installed before all heater wells or production wells are drilled.
  • step S 1559 the pre-drilled heaters are operated to produce hydrocarbon fluids such that a ratio between a half-maximum sustained production time and a rise time is at least four-thirds, or at least three-halves, or at least seven quarters or at least two. In some embodiments, this is accomplished using any inner zone and outer zone heater pattern disclosed herein. In some embodiments, at least a majority of the outer zone heaters commence operation when at most a minority of inner zone hydrocarbon fluids have been produced.
  • any heater pattern disclosed herein may be thermally efficient.
  • at least 5% or at least 10% or at least 20% of the thermal energy used for outer zone hydrocarbon fluid production is supplied by outward migration (e.g. by heat conduction and/or convection) of thermal energy from the inner zone 210 to the outer zone 214 .
  • a hydrocarbon fluid production temperature e.g. a temperature which results in mobilized fluids, visbreaking, and/or pyrolysis of hydrocarbon-containing material so that mobilized fluids, visbroken fluids, and/or pyrolyzation fluids are produced in the formation
  • a hydrocarbon fluid production temperature e.g. a temperature which results in mobilized fluids, visbreaking, and/or pyrolysis of hydrocarbon-containing material so that mobilized fluids, visbroken fluids, and/or pyrolyzation fluids are produced in the formation
  • a hydrocarbon fluid production temperature e.g. a temperature which results in mobilized fluids, visbreaking, and/or pyrolysis of hydrocarbon-containing material so that mobilized fluids, visbroken fluids, and/or pyrolyzation fluids are produced in the formation
  • a hydrocarbon fluid production temperature e.g. a temperature which results in mobilized fluids, visbreaking, and/or pyrolysis of hydrocarbon-containing material so that mobilized fluid
  • the heater pattern of FIG. 2A may repeat itself.
  • any inner zone-outer zone heater pattern disclosed herein may be a ‘unit cell’ heater pattern which repeats itself. Since any heater pattern disclosed herein (and any feature(s) thereof or combination thereof) may also be a ‘heater well pattern,’ the heater well pattern of FIG. 2A , or of any other embodiment disclosed herein, may repeat itself.
  • each heater cell may individually provide common features (i.e. any combination of features disclosed herein including but not limited to features related to heater spacing features, heater spatial density feature(s), features related to size(s) and/or shape of inner and/or outer zones (or relationships between them), production well features, features relating to operation of heaters or any other feature).
  • an area enclosed by outer zone perimeter 208 is about four times that of inner zone perimeter 204 , a heater density within inner zone 210 significantly exceeds that of outer zone 214 , at least a substantial majority of the inner zone heaters 226 are located away from outer zone perimeter 208 , production well(s) are located in each of inner 210 and outer 214 zones.
  • the area of all cells are substantially equal to a single common value; (ii) for each heater cell of the plurality of cells, a significant portion (i.e. at least one third or at least one half or at least two-thirds or at least three-quarters) of each cell perimeter (e.g. outer zone perimeter 208 ) is located ‘close’ to a neighboring cell perimeter.
  • a ‘candidate location’ of a first heater cell i.e. within the cell or on a perimeter thereof—e.g. cell A 610 ) is located ‘close to’ a second heater cell (e.g. cell B 614 or C 618 ) if a distance between (i) the ‘candidate location’ of the first heater cell and (ii) a location of the second heater cell that is closest to the ‘candidate location’ of the first heater cell is less than a ‘threshold distance.’ Unless otherwise specified, this ‘threshold distance’ is at most two-fifths of a square root of an area of the first heater cell. In some embodiments, this ‘threshold distance’ is at most one third or at most one quarter or at most one sixth or at most one tenth of a square root of an area of the first heater cell.
  • At least a portion e.g. at least 5% or at least 10% or at least 20% or at least 30% or at least 40% or at least a majority of
  • each cell perimeter selected from one of the first and second heater cells is ‘close’ to the other heater cell.
  • one of the cells is a ‘surrounded cell’ whereby an entirety of its perimeter is ‘close to’ neighboring heater cells.
  • a heater cell is ‘substantially surrounded’ when a substantial majority (i.e. at least 75%) of its perimeter is ‘close to’ a neighboring heater cell.
  • different portions of a perimeter of surrounded cell 608 are ‘close to’ six different neighboring heater cells.
  • different portions of a perimeter of surrounded cell 608 are ‘close to’ at least 3 or at least 4 or at least 5 different neighboring cells—e.g. a majority of which or at least 3 or at least 4 or at least 5 of which have an area that is ‘substantially equal’ to that of surrounded cell 608 .
  • first 602 and second 604 neighboring cells which are located on opposite sides of surrounded cell 608 .
  • two neighboring cells CELL 1 NEIGHBOR and CELL 2 NEIGHBOR having respective centroids ⁇ CENT(CELL 1 NEIGHBOR ) and CENT(CELL 2 NEIGHBOR ) are said to be ‘substantially on opposite sites’ of a candidate heater cell CELL CANDIDATE having a centroid CENT(CELL CANDIDATE ) if an angle ⁇ CENT(CELL NEIGHBOR 1 )CENT(CELL CANDIDATE )CENT(CELL NEIGHBOR 2 ) is at least 120 degrees. In some embodiments, this angle is at least 130 degrees or at least 140 degrees or at least 150 degrees.
  • neighboring cells may ‘share’ one or more (e.g. at least two) common outer perimeter heaters 236 .
  • each of the shared heater serves as an outer perimeter heater for two or more neighboring cells.
  • neighboring heater cells may share up to three common outer perimeter heaters.
  • the multi-cell pattern based upon nested hexagons may provide one or more of the following benefits: (i) a significantly lower heater well density (e.g. at most three-thirds or at most three-fifths or at most one-half) compared to what would be observed for the hypothetical case where all heaters were arranged at a uniform density equal to that of the inner zones 210 ; (ii) a relatively short time to first production (e.g. see FIG.
  • FIG. 8 It appreciated that other embodiments other than that of FIG. 8 may provide some or all of the aforementioned benefits.
  • FIG. 9 The pattern of FIG. 9 is similar to that of FIG. 8 —however, in the example of FIG. 9 production wells are arranged at the centroid 296 , 298 of each heater cell, while in the example of FIG. 8 heaters are arranged at the centroid 296 , 298 of each heater cell.
  • a region of subsurface formation is filled with multiple heater cells including cell “A” 610 , cell “B” 614 and cell “C” 618 .
  • cells “A” 610 and “C” 618 share common outer zone perimeter heater “W” 626 ; cells “A” 610 and “B” 614 share common outer zone perimeter heater “X” 639 ; cells “B” 614 and “C” 618 share common outer perimeter heater “Y” 638 .
  • the heater cells do not have identical patterns, and the heater cells may be thought of as ‘quasi-unit cells’ rather than ‘unit cells.’
  • each heater cell individually may contain any combination of feature(s) relating to inner 210 and outer 214 zones described in any embodiment herein.
  • the features include but are not limited to features related to heater spacing (e.g. shorter average spacing between neighboring heaters in inner zone 214 than in outer zone 210 ), heater density (e.g. higher density in inner zone 214 than in outer zone 210 ), dimensions of inner and/or outer zone perimeters 204 , 208 (e.g.
  • any other feature e.g. including but not limited to feature(s) related to heater location.
  • neighboring cells all have like-shaped and like-sized inner zone and outer zone perimeters 204 , 208 .
  • areas or aspect ratios of inner zone and/or outer zone perimeters 204 , 208 of neighboring cells may be similar but not identical.
  • an area enclosed by inner zone and/or outer zone perimeters 204 , 208 of CELL 1 is (i) equal to at least 0.5 times and at most 2.0 times that of CELL 2 or (ii) equal to at least 0.666 times and at most 1.5 times that of CELL 2 ; or (iii) equal to at least 0.8 and at most 1.2 times that of CELL 2 .
  • an aspect ratio of inner zone and/or outer zone perimeters 204 , 208 of CELL 1 is (i) equal to at least 0.5 times and at most 2.0 times that of CELL 2 or (ii) equal to at least 0.666 times and at most 1.5 times that of CELL 2 ; or (iii) equal to at least 0.8 and at most 1.2 times that of CELL 2 .
  • any feature(s) in the previous paragraph relating any pair of neighboring heater cells CELL 1 , CELL 2 may be true for at least one pair of neighboring heater cells CELL 1 , CELL 2 .
  • any feature(s) may be true for various pair sets of cells. For example, if a cell CELL GIVEN surrounded by a plurality of neighbors CELL NEIGHBoR — 1 , CELL NEIGHBoR — 2 , . . .
  • CELL NEIGHBOR — N any feature(s) of the previous paragraph previous paragraph may be true for at least a majority, or for all of the following cell pairs: ⁇ CELL GIVEN , CELL NEGHBoR — 1 ⁇ , ⁇ CELL GIVEN , CELL NEIGHBOR — 2 ⁇ , . . . , ⁇ CELL GIVEN , CELL NEIGHBOR — N ⁇ .
  • a region of the subsurface formation may be ‘substantially filled’ by a plurality of heater cells if at least 75% or at least 80% or at least 90% of the area of the region is occupied by one of the heater cells.
  • the ‘cell-filled-region’ includes at least 3 or at least 5 or at least 10 or at least 15 or at least 20 or at least 50 or at least 100 heater cells and/or is rectangular in shape and/or circular in shape or having any other shape and/or has an aspect ratio of at most 3 or at most 2.5 or at most 2 or at most 1.5.
  • any feature(s) relating pairs of neighboring cells i.e.
  • both a ‘length’ and a ‘width’ of the cell-filled region may be at least 3 or at least 5 or at least 10 or at least 20 heater cells.
  • FIGS. 2-12 relate to heater patterns having at least two ‘levels’—i.e. an inner zone 210 having relatively high heater density and an outer zone 214 having relatively low heater density.
  • one or more heater cells have at least ‘three’ levels.
  • OZS additional zone heaters i.e. heaters located OZS additional zone perimeter 202 or in an interior of OZS additional zone 218
  • OZS additional zone heaters include OZS additional zone perimeter heaters each located on or near OZS additional zone perimeter 202 and distributed around OZS additional zone perimeter 202 .
  • OZS additional zone heaters are predominantly OZS additional zone perimeter heaters—this is analogous to the feature provided by some embodiments and described above whereby outer zone heaters 228 are predominantly outer zone perimeter heaters 236 .
  • the OZS 210 refers to the entire area enclosed by a perimeter 202 thereof. that is also outside of outer zone 214 .
  • an area enclosed by a perimeter 202 of OZS additional zone 218 and four times that of outer zone perimeter 202 , and an average heater spacing within OZS additional zone 218 is about twice that of outer zone 214 .
  • perimeters 204 , 208 , 202 of inner, outer and OZS-additional zones 210 , 214 , 218 are regular-hexagonal in shape and have respective side lengths equal to 2s, 4s, and 8s.
  • respective average heater spacings of inner 210 , outer 214 , and OZS additional 218 zones are equal to s, approximately equal to 2s, and approximately equal to 4s.
  • a perimeter 202 of OZS additional zone 218 is convex or substantially convex.
  • a relation between OCS additional zone 218 and outer zone 214 is analogous to that between outer zone 214 and inner zone 210 .
  • any feature described herein a relationship between inner 210 and outer 214 zones may also be provided for outer 214 and OZS additional 218 zones.
  • Such features include but are not limited to features related to heater spacing (e.g. shorter average spacing between neighboring heaters in inner zone 214 than in outer zone 210 ), heater density (e.g. higher density in inner zone 214 than in outer zone 210 ), dimensions of inner and/or outer zone perimeters 204 , 208 (e.g.
  • any other feature e.g. including but not limited to feature(s) related to heater location.
  • the perimeter 202 of OZS additional zone 218 may be defined by locations of the heater (i.e. to form some a ring-shaped cluster where adjacent locations have a significantly lower heater density).
  • production wells 224 are arranged through each of inner 210 , outer 214 , and OZS additional zone 218 , and are respectively labeled in FIG. 13 as inner zone 2241 , outer zone 2240 and additional zone 224 A production wells.
  • the density of production wells is greatest in the most inner zone (i.e. inner zone 210 ), is the least in the most outer zone (i.e. additional zone 218 ) and has an intermediate value in the ‘mediating’ zone (i.e. outer zone 214 ).
  • a ratio between an inner zone production well density and that of outer zone 210 is three; a ratio between an outer zone production well density and that of additional zone 214 is also three.
  • perimeters 208 , 202 of outer 214 and OZS-additional 218 zones are like shaped. As illustrated in FIGS. 13-14 , this is not a limitation.
  • perimeters 208 , 204 of outer 214 and inner 210 zones are not required to be like-shaped but they may share certain shape-properties—for example, an aspect ratio (see, for example FIGS. 10A-10B ) or any other shape-related parameter discussed herein.
  • Embodiments of the present invention relate to patterns of ‘heaters.’
  • the heaters used may be electrical heaters, such as conductor-in-conduit or mineral-insulated heaters; downhole gas combustors; or heaters heated by high temperature heat transfer fluids such as superheated steam, oils, CO 2 , or molten salts or others. Because the outer zones 214 of heaters may be energized for a substantially longer time than the inner zone of heaters, for example, four times or eight times longer (see FIG. 13A ), a heater with high reliability and long life is preferred for the outer 214 or OZS additional 218 zones.
  • Molten salt heaters have very long lifetimes because they operate at nearly constant temperature without hot spots, and in many chemical plant and refinery applications, molten salt heaters have been operated for decades without shutdown. In addition, molten salt heaters may have very high energy efficiency, approaching 80%, and over the lifetime of the reservoir most of the thermal energy will be supplied to the oil shale from the heaters in the zones with the longest spacing.
  • FIG. 15A is an image of an exemplary electrical heater.
  • FIG. 15B is an image of an exemplary molten salt heater.
  • FIG. 15C is an image of an exemplary downhole combustion heater;
  • FIG. 15D is a cross section of the downhole portion of the the heater of FIG. 15C .
  • molten salt is continuously flowed through the heater.
  • hot molten salt e.g. heated by a gas furnace
  • FIG. 15E A schematic of an advection-based heater is illustrated in FIG. 15E .
  • the source of hot heat transfer fluid is illustrated in the figures as above the surface, this is not a requirement—alternatively or additionally, it is possible to heat the heat transfer fluid at one or more subsurface location(s).
  • FIGS. 16A-16D relate to ‘heaters powered primarily by fuel combustion’.
  • a fuel e.g. a fossil fuel
  • thermal energy of the fuel combustion generates steam which drives a steam turbine to produce electricity.
  • the electrical heater (for example, similar to FIG. 15A ) is powered by the fuel-combustion-derived electricity.
  • fuels which may be combusted include but are not limited to methane, natural gas, propane, flue gas, coal and hydrogen gas.
  • a gas turbine powered by gas combustion generates electricity supplied to the electrical heater.
  • FIGS. 16C-16D Other examples of “heaters powered primarily by fuel combustion” are illustrated in FIGS. 16C-16D (i.e.
  • the generated electricity i.e. from the steam turbine or the gas turbine
  • a material e.g. a ferromagnetic material
  • a heat transfer fluid one example of a heat transfer fluid is a molten salt; another example is a synthetic oil; another example is molten metal.
  • the heat transfer fluid is heated above the surface where the resistively-heated material (i.e. which receives electrical current derived from combustion of fossil fuel) is located within an above-surface storage tank.
  • the heat transfer fluid may be heated in the subsurface—e.g.
  • FIGS. 16A-216D relate to the situation wherein thermal energy of combustion is used to generate electricity. This is not a limitation.
  • Other examples of ‘heaters powered primarily by combustion’ are illustrated in FIGS. 15C-15D discussed above.
  • the heaters of FIGS. 17A-17B are powered ‘primarily by electricity generated from wind.’
  • electricity generated from wind is used to resistively heat a material (e.g. a ferromagnetic material) in thermal communication with a heat transfer fluid.
  • the heat transfer fluid is heated above the surface where the resistively-heated material (i.e. which received electricity derived from wind) is located in an above-surface fluid storage tank.
  • the heat transfer fluid may be heated in the subsurface—e.g. the resistively-heated material (i.e. through which electrical current generated from wind) may be located in the subsurface.
  • an electrical heater is powered by electricity generated from wind.
  • Any electrical heater may include a voltage control system (NOT SHOWN).
  • the turbine may be a microturbine—for example, available from the Capstone Turbine Corporation (United States).
  • At least a majority or at least 2 ⁇ 3 of the heaters are powered primarily by electricity from wind.
  • a majority of at least 2 ⁇ 3 of the heaters are powered primarily by fuel combustion—hot fluids from the combusted fuel may be directly circulated within the subsurface (see FIGS. 15C-15D ) or thermal energy from the fuel combustion may be used to generate electricity (see FIGS. 16A-16C ).
  • FIG. 20-21 In the inner zone, at least a majority or at least 2 ⁇ 3 of the heaters are powered primarily by fuel combustion—hot fluids from the combusted fuel may be directly circulated within the subsurface (see FIGS. 15C-15D ) or thermal energy from the fuel combustion may be used to generate electricity (see FIGS. 16A-16C ).
  • FIGS. 22A-B Some embodiments relate to ‘neighboring heaters’ or ‘average spacing between neighboring heaters.’ Reference is made to FIGS. 22A-B .
  • heaters are arranged according to the same heater pattern as in FIGS. 2A-2D , and heaters are labeled as follows: seven of the outer perimeters heaters are labeled 220 A- 220 G, and nine of the inner zone heaters are labeled as 220 H- 220 P.
  • FIG. 22B illustrates a portion of the heater pattern of FIG. 22A .
  • heaters 220 C and 220 D are ‘neighbors,’ heaters 220 C and 220 J are ‘neighbors,’ heaters 220 J and 220 K are ‘neighbors’) while for other heaters, this is not true.
  • Heaters 220 C and 220 L of the ‘heater pair’ are clearly not ‘neighbors.’ This is because ‘heater-connecting-line segment’ Seg_Connect( 220 C, 220 L) connecting heaters (i.e.
  • FIG. 22C illustrate the same heaters as in FIG. 22 B—line segments of ‘neighboring heater pairs’ are illustrated.
  • the neighboring heater pairs are as follows: ⁇ Heater 220 C, Heater 220 D ⁇ ; ⁇ Heater 220 D, Heater 220 E ⁇ ; ⁇ Heater 220 E, Heater 220 L ⁇ ; ⁇ Heater 220 K, Heater 220 L ⁇ ; ⁇ Heater 220 J, Heater 220 K ⁇ ; ⁇ Heater 220 C, Heater 220 J ⁇ ; ⁇ Heater 220 D, Heater 220 J ⁇ ; ⁇ Heater 220 D, Heater 220 K ⁇ ; ⁇ Heater 220 D, Heater 220 L ⁇ ,
  • FIG. 23A illustrates the same heater pattern as that of FIGS. 2A-2D and FIG. 22A .
  • FIG. 22C lines between neighboring heaters are illustrated.
  • the average line length, or the average ‘heater spacing’ is around 1.95s, or slightly less than 2s.
  • the average line length, or the average ‘heater spacing’ is exactly s.
  • FIG. 23B illustrates ‘connecting line segments’ between neighboring heaters.
  • the average line length corresponding to the average heater spacing, is exactly s.
  • Heater A Two heaters Heater A , Heater B are ‘neighboring heaters’ if the connecting line segment between them (i.e. between their respective centroids) does not intersect a connecting line segment between two other heaters Heater C , Heater D in the subsurface formation.
  • a ‘heater-connecting-line-segment between neighboring heaters’ is ‘resident within’ a region of the subsurface formation (i.e. a two-dimensional cross-section thereof) if a majority of the length of the ‘heater-connecting-line-segment’ is located within the region of the subsurface formation.
  • FIGS. 23C-24 respectively illustrate ‘connecting lines’ between neighboring heaters.
  • an ‘average spacing between neighboring heaters’ and an ‘average heater spacing’ are used synonymously.
  • Embodiments of the present invention relate to inner perimeter heaters 232 , outer perimeter heaters 236 and ‘OZS additional zone perimeter heaters.’
  • the locations of the heaters determine the locations of the perimeters 204 , 208 (and by analogy 202 ) of inner 210 , outer 214 or OZS additional 218 zones.
  • inner perimeter heaters 232 , outer perimeter heaters 236 , and OSC-additional-zone perimeter heaters respectively are located on perimeters 204 , 208 , 202 .
  • these perimeters 204 , 208 , 202 may be determined by a predetermined shape—e.g. a rectangle or regular hexagon or any other shape.
  • a predetermined shape e.g. a rectangle or regular hexagon or any other shape.
  • the inner perimeter heaters 232 there is no requirement for the inner perimeter heaters 232 to be located exactly on inner zone perimeter 204 —it is sufficient for the heater to be located near inner perimeter—e.g. in a ‘near-inner-perimeter’ location within inner zone 210 or within outer zone 214 .
  • outer zone perimeter 208 or OZS-additional zone perimeter 202 may be determined by a predetermined shape—e.g. a rectangle or regular hexagon or any other shape.
  • FIGS. 25A-25B illustrate: (i) locations in the interior 610 of the inner zone 210 ; (ii) locations 614 in inner zone 210 that are ‘substantially on’ inner zone perimeter 204 ; (iii) locations 618 in outer zone 214 that are ‘substantially on’ inner zone perimeter 204 ; (iv) locations 622 in the interior of the ‘interior’ of outer zone 214 (i.e. away from both inner zone and outer zone perimeters 204 , 208 ); (iv) locations 626 in outer zone 214 that are ‘substantially on’ outer zone perimeter 208 ; (v) locations 626 outside of outer zone 214 that are ‘substantially on’ outer zone perimeter 208 .
  • a ratio between (i) a distance from the candidate location 614 to a nearest location on inner zone perimeter 204 and (ii) a distance from the candidate location 614 to a centroid of inner zone 210 is at most 0.25 or at most 0.2 or at most 0.15 or at most 0.05.
  • a ratio between a (i) distance from the candidate location 618 to a nearest location on inner zone perimeter 204 and (ii) a distance from the candidate location 618 to a nearest location on outer zone perimeter 208 is at most 0.25 or at most 0.2 or at most 0.15 or at most 0.05.
  • a ratio between (i) a distance from the candidate location 626 a nearest location on outer zone perimeter 208 and (ii) a distance from the candidate location 626 to a nearest location on inner zone perimeter 204 is at most 0.25 or at most 0.2 or at most 0.15 or at most 0.05.
  • a ratio between (i) a distance from the candidate location 630 a nearest location on outer zone perimeter 208 and (ii) a distance from the candidate location 630 to a centroid 298 of the area enclosed by outer zone perimeter 208 is at most 1.25 or at most 1.15 or at most 1.05.
  • heaters are distributed’ around perimeter 208 of outer zone 214 , this means that heaters (i.e. which are located on or near outer zone perimeter 208 ) are present on every 90 degree sector of outer zone perimeter 208 .
  • FIGS. 26A-26B This is illustrated in FIGS. 26A-26B .
  • FIG. 26A it is possible to divide the cross-area of the subsurface formation into four ‘quadrants’ corresponding to four 90 degree sectors (i.e. since the quotient of 360 degrees and four is 90 degrees) relative to any arbitrary ‘reference ray 316 ’ starting at centroid of outer zone 214 .
  • FIGS. 26A-26B illustrate respective orientations of reference ray 316 .
  • these four portions are defined as (i) the portion of outer zone perimeter 208 located in Q1 160 between points 402 and 404 ; (ii) the portion of outer zone perimeter 208 located in Q2 162 between points 402 and 408 ; (iii) the portion of outer zone perimeter 208 located in Q3 164 between points 406 and 408 ; (iv) the portion of outer zone perimeter 208 located in Q4 166 between points 406 and 404 .
  • these four portions are determined by four points on outer zone perimeter 208 , namely points 402 , 404 , 406 and 408 .
  • FIG. 26B associated with a different orientation of reference ray 316 , these four portions are determined by points 422 , 424 , 426 and 428 , all lying on outer zone perimeter 208 .
  • heaters when heaters are ‘present’ on every 90 degree sector of outer zone perimeter 208 , then irrespective of an orientation of a reference line 316 relative to which four quadrants are defined (i.e. for any arbitrary reference line orientation), there is at least one outer perimeter heater 236 within each of the four quadrants.
  • This concept can be generalized to 72 degree sectors (i.e. to divide the subsurface cross section into five equal portions rather than four quadrants), 60 degrees sectors (i.e. six equal portions or ‘sextants’) and 45 degree sectors (i.e. eight equal portions or ‘octants’).
  • FIGS. 27-28 Reference is now made to FIGS. 27-28 .
  • Embodiments of the present invention relate to features of ‘distances between heaters’ or ‘distances between a heater and a location,’ where ‘distance’ and ‘displacement’ may be used interchangeably.
  • any ‘distance’ or ‘displacement’ refers to a distance or displacement constrained within a two-dimensional cross section for which a heater pattern is defined—for example, including but not limited to any heater pattern illustrated in FIGS. 2-11 and 15 - 16 .
  • embodiments of the present invention relate to apparatus and methods whereby (i) due to the relatively ‘high’ heater density and to the distribution of inner zone heaters 226 throughout inner zone 210 , a significant fraction of inner zone 210 is ‘very close’ to a nearest heater; (ii) due to the relatively ‘low’ heater density and to feature whereby most outer zone heaters 228 are arranged at or near outer perimeter 208 , a significantly smaller fraction of outer zone 214 is ‘very close’ to a nearest heater. As such, the rate of production increases in the inner zone 210 significantly faster than in the outer zone 214 .
  • a ‘distance between heaters’ refers to the distance between respective heater centroids.
  • a ‘heater centroid’ 310 is a centroid of the heater cross-section co-planar the two-dimensional cross-section of the subsurface where any heater pattern feature is defined.
  • heater cross-section is not required to be circular.
  • the ‘distance between heaters 220 ,’ which is the distance between their respective centroids 310 is not necessarily between the locations on the heater surface.
  • Some embodiments refer to a ‘distance’ or ‘displacement’ between a location (indicated in FIGS. 28A-28D by an ‘X’) within the subsurface formation and one of the heaters. Unless indicated otherwise, this ‘distance’ or ‘displacement’ is: (i) the distance D within the plane defined by the two-dimensional cross-section of the subsurface where any heater pattern feature is defined; (ii) the distance D between the location ‘X’ and the heater centroid 310 . In the examples of FIGS.
  • the distance between a location ‘X’ and heater 220 is defined by the distance between heater centroid 310 and location ‘X,’ even for situations where the location ‘X’ is within heater 220 but displaced from heater centroid 310 .
  • FIGS. 29A-29C illustrate the concept of a substantially convex shape. If a candidate shape 720 is convex it is, by definition, also substantially convex. If candidate shape 720 is not convex, it is possible to determine if candidate shape 720 is substantially convex according to one of two theoretical convex shapes: (i) a minimum-area enclosing convex shape 722 —i.e. the smallest (i.e. of minimum area) convex shape which completely encloses the candidate shape 720 ; (ii) a maximum-area enclosed convex shape 724 —i.e. the ‘largest’ (i.e. of maximum area) convex shape which is completely within candidate shape 720
  • first area ratio a ratio between (i) an area enclosed by minimal-area enclosing convex shape 722 and (ii) an area enclosed by candidate shape 720 . It is possible to define a second area ratio as a ratio between (i) an area enclosed by candidate shape 720 and (ii) an area enclosed by maximum-area enclosed convex shape 724 .
  • a candidate shape 720 is ‘substantially convex’ if one or both of these area ratios is at most a ‘threshold value.’ Unless specified otherwise, this threshold value is at most 1.3. In some embodiments, this threshold value may be at most 1.2 or at most 1.15 or at most 1.1 or at most 1.05.
  • ‘convex shape tolerance value’ of the candidate shape 720 is said to be X.
  • the ‘convex shape tolerance value’ is at most 1.2 or at most 1.15 or at most 1.1 or at most 1.05.
  • spatial heater density is defined according to the principles of reservoir engineering.
  • the heater FIG. 2A nineteen heaters are inner zone heaters 226 located on the inner zone perimeter 204 or within inner zone 210 , while twelve heaters are outer zone heaters 228 located on outer zone perimeter 208 or within outer zone 214 .
  • FIG. 30 illustrates a portion of the heater scheme of FIG. 2A , where heaters are labeled as in FIG. 22C .
  • heaters are labeled as in FIG. 22C .
  • the radius of immediate-neighboring-region circles around heaters 220 A, 220 C and 220 G, 220 E and 220 G (i.e. all located on vertices of outer hexagon 208 ) equals a
  • the radius of immediate-neighboring-region circles around heaters 220 B, 220 D and 220 F (i.e. all located halfway between adjacent vertices of outer hexagon 208 ) is
  • ‘outer-hexagon-vertex’ heaters are outer zone heaters are located on vertices of outer hexagon 208
  • ‘outer-hexagon-mid-side’ heaters are outer zone heaters labeled as 220 B, 220 D and 220 F in FIG.
  • outer zone heaters located midway between adjacent vertices of outer hexagon 208
  • ‘inner-hexagon-vertex’ heaters are inner zone heaters are located on vertices of inner hexagon 204
  • ‘inner-hexagon-mid-side’ heaters are inner zone heaters located midway between adjacent vertices of inner hexagon 204 .
  • the total number of heaters ‘belonging to’ inner zone 210 include: (i) seven ‘internally-located’ heaters 226 located within inner zone 210 and not on the perimeter of inner hexagon 204 (i.e. including heaters 220 O and 220 P); (ii) one-half of each of the six inner zone heaters 226 located midway between adjacent vertices of the inner hexagon 204 (i.e. including heaters 220 I, 220 K and 220 M) for a total of three heaters; and (iii) one-third of each of the six inner zone heaters 226 located at vertices of the inner hexagon 204 (i.e. including heaters 220 H, 220 J, 220 L and 220 N) for a total of two heaters.
  • the total number of heaters ‘belonging to’ outer zone 214 include: (i) one-half of each of the six inner zone heaters 226 located midway between adjacent vertices of the inner hexagon 204 (i.e. including heaters 220 I, 220 K and 220 M) for a total of three heaters; (ii) two-thirds of each of the six inner zone heaters 226 located at vertices of the inner hexagon 204 (i.e.
  • heaters 220 H, 220 J, 220 L and 220 N for a total of four heaters; (iii) one-half of each of the six outer zone heaters 228 located midway between adjacent vertices of the outer hexagon 208 (i.e. including heaters 220 B, 220 D and 220 F) for a total of three heaters; and (iv) one-third of each of the six outer zone heaters 228 located at vertices of the outer hexagon 208 (i.e. including heaters 220 A, 220 C, 220 E and 220 G) for a total of two heaters.
  • 12 heaters belong to inner zone 210 and 12 heaters belong to outer zone 214 . Because the area of outer zone 214 is three times that of inner zone 210 , because the number of heaters belonging to inner 210 and outer 214 zones is the same, the heater spatial density within inner zone 210 may be said to be three times that of outer zone 214 .
  • any given region i.e. cross section of the subsurface
  • one determines, for each heater in the formation within or relatively close to the given region, a nearest neighboring heater distance; (ii) for each heater, determines a ‘immediate-neighboring-region circle’ around each heater centroid (i.e. having a radius equal to one half of the distance to a nearest neighboring heater), (iii) computes, for each heater in the formation, a fraction of the immediate-neighboring-region circle located within the given region to determine the fraction (i.e. between 0 and 1) of the heater belonging to the given region; (iv) determines the total number of heaters belonging to the given region and (v) divides this number by the area of the given region.
  • a ratio between (i) a heater spatial density in inner zone 210 ; and (ii) a heater spatial density in outer zone 214 is exactly three.
  • a spatial density ratio between a heater spatial density in inner zone 210 and that of outer zone 214 is at least 1.5, or at least 2, or at least 2.5 and/or at most 10 or at most 7.5 or at most 5 or at most 4.
  • Some embodiments relate to a ‘nearest heater’ to a location in the subsurface formation.
  • location A 2242 (marked with a star) is closer to heater ‘A’ 2246 than to any other heater. Therefore, a ‘distance to a nearest heater at location A’ is the distance between location ‘A’ 2242 and heater ‘A’ 2246 .
  • location B 2252 (marked with a cross) is closer to heater ‘B’ 256 than to any other heater. Therefore, a ‘distance to a nearest heater at location B’ is the distance between location B 2252 and heater B 2256 .
  • location C 2262 (marked with a number symbol) is closer to heater ‘C’ 2266 than to any other heater. Therefore, a ‘distance to a nearest heater at location C’ is the distance between location C 2262 and heater C 2266 .
  • Some embodiments relate to the ‘average distance’ within an area of the subsurface formation or on a curve within the surface formation (e.g. a closed curve such as a zone perimeter 204 or 208 or 202 ) to a nearest heater.
  • a curve within the surface formation e.g. a closed curve such as a zone perimeter 204 or 208 or 202
  • Each location within the area of curve LOC ⁇ AREA or LOC ⁇ CURVE is associated with a distance to a nearest heater (or heater well)—this is the distance within the cross-section of the subsurface formation for which a heater pattern is defined to a heater centroid within the cross-section (see FIGS. 27-28 ).
  • the heater which is the ‘nearest heater’ to the location LOC E AREA or LOC E CURVE within the area or on the curve is not required to be located in the ‘area’ AREA or curve.
  • FIGS. 33-36 illustrate some relatively simple examples.
  • a distance to a nearest heater is the same as the distance to the origin, i.e. ⁇ square root over ((x 0 ) 2 +(y 0 ) 2 ) ⁇ square root over ((x 0 ) 2 +(y 0 ) 2 ) ⁇ .
  • the integral it is possible to compute the integral:
  • the ‘average distance to a nearest heater’ within Region A may be approximated by a distance between (i) a centroid of Region A 2032 —i.e. the point (1 ⁇ 2,1/2); and (ii) heater A 2090 . This distance is equal to approximately 0.71.
  • EQN. 2 is valid for a particular region illustrated in FIG. 33A .
  • AVG_NHD is an abbreviation for ‘nearest heater distance’
  • AVG_NHD ⁇ ( REGION ) ⁇ REGION ⁇ DIST ⁇ ( LOC , HEATER_H ) ⁇ ⁇ ⁇ LOC ⁇ Area_of ⁇ _REGION ⁇ ( EQN ⁇ ⁇ 3 )
  • LOC is a location within REGION
  • dLOC is the size (i.e. area or volume) of an infinitesimal portion of the subsurface formation at location LOC within REGION
  • DIST(LOC,HEATER_H) is a distance between HEATER_H and location LOC.
  • EQN. 3 assumes that only a single heater is present in the subsurface formation.
  • EQN. 3 may be generalized for a subsurface in which a heaters ⁇ H 1 , H 2 , . . . H i . . . H N ⁇ (i.e. for any positive integer N) are arranged at respective locations ⁇ LOC(H 1 ), LOC(H 1 ), . . . LOC(H i ), . . . LOC(H N ), ⁇ .
  • any location LOC within the subsurface formation is associated with a respective nearest heater H NEAREST (LOC) that is selected from ⁇ H 1 , H 2 , . . . H i . . .
  • H N H N ⁇ .
  • a nearest heater H NEAREST LOC
  • Heater P 2102 situated at (0,1).
  • a nearest heater H NEAREST LOC
  • Heater Q 2104 situated at (2,1).
  • a nearest heater distance NHD(LOC) is defined as DIST(LOC, H NEAREST (LOC))—a distance between the location LOC and its associated nearest heater H NEAREST (LOC).
  • EQN. 3 may be generalized as:
  • AVG_NHD ⁇ ( REGION ) ⁇ REGION ⁇ NHD ⁇ ( LOC ) ⁇ ⁇ ⁇ LOC ⁇ Area_of ⁇ _REGION ⁇ . ( EQN ⁇ ⁇ 4 )
  • Region C 2036 may be divided into four sub-regions A1-A4 2080 , 2082 , 2084 , 2086 .
  • a nearest heater H NEAREST LOC A1
  • Heater B 2092 For any location LOC A1 in sub-region A1 2080 , a nearest heater H NEAREST (LOC A1 ) is Heater B 2092 .
  • a nearest heater H NEAREST (LOC A3 ) is Heater A 90 .
  • a nearest heater H NEAREST (LOC A2 ) is Heater C 2094 .
  • a nearest heater H NEAREST (LOC A4 ) is Heater D 2096 .
  • Region C 2036 may be divided into eight sub-regions B1-B8 2060 , 2062 , 2064 , 2066 , 2068 , 2072 , 2074 .
  • a ‘nearest heater’ H NEAREST (LOC B1 ) is Heater B 2092 .
  • a ‘nearest heater’ H NEAREST (LOC B2 ) is Heater E 2098 .
  • a ‘nearest heater’ H NEAREST (LOC B3 ) is Heater E 2098 .
  • a ‘nearest heater’ H NEAREST (LOC B4 ) is Heater C 2094 .
  • a nearest heater H NEAREST (LOC B5 ) is Heater A 2090 .
  • a nearest heater H NEAREST (LOC B6 ) is Heater E 2098 .
  • a nearest heater H NEAREST (LOC B7 ) is Heater E 2098 .
  • a nearest heater H NEAREST (LOC B8 ) is Heater D 2096 .
  • FIG. 35A there are four corner heaters and a fifth more central heater E 2098 situated exactly in the center of the square-shaped region.
  • FIG. 35B there are also four corner heaters—however, the fifth more central heater E′ 98 ′ is situated on the center of one of the square sides rather than in the center of the square.
  • the heater density for both the example of 35 A and of 35 B is identical.
  • the ‘average distance to a nearest heater’ in the example of FIG. 35B is about 0.68, or about 15% greater than that of the example of FIG. 35A . This is due to the less uniform distribution of heaters within Region C 2038 in the example of FIG. 35B .
  • the aforementioned examples relate to the average distance to a nearest heater within an area of the sub-formation formation. It is also possible to compute the ‘average distance to a nearest heater’ for any set of points—for example, along a line, or along a curve, or along the perimeter of a polygon.
  • the ‘average distance to a nearest heater’ along the perimeter 2052 of region A 2032 is given by:
  • AVG_NHD ⁇ ( ALONG_CURVE ⁇ _C ) ⁇ CURVE ⁇ _ ⁇ C ⁇ NHD ⁇ ( LOC ) ⁇ ⁇ ⁇ LOC ⁇ Length_of ⁇ _Curve ⁇ _C ⁇ ( EQN . ⁇ 6 )
  • location LOC is a location on Curve C.
  • Curve is inner zone or outer zone perimeters 204 , 208 .
  • FIG. 37A illustrates fractions of inner 210 and outer 214 zones (and perimeters 204 , 208 thereof) that are heater-displaced or heater-centroid-displaced by at most a first threshold distance; diam 1 /2.
  • Diam 1 is the diameter of a circle centered around each heater centroid 310 .
  • Shaded locations in FIG. 8 are those portions of inner and outer zones which are displaced from a centroid 310 of one or more of the heaters 210 by less than a distance Diam 1 .
  • each shaded circle has an area that is around 3-5% of the area of inner zone 210 .
  • the fraction of inner zone 210 that is shaded is significant—e.g. at least 30% or at least 40% or at least 50% or at least 60% or at least 70% of the area of inner zone 210 . Because a significant number of heaters are located around an entirety of inner perimeter 204 , the fraction of inner perimeter 204 that is shaded is significant—e.g. at least 30% or at least 40% or at least 50% or at least 60% or at least 70% of the length of inner perimeter 204 . In contrast, due to the much lower heater density in outer zone 210 , a much smaller fraction of outer zone 210 is shaded.
  • the portion of the outer perimeter 208 that is heater-displaced or ‘heater-centroid-displaced’ by at most the second threshold distance is significant—e.g. at least 30% or at least 40% or at least 50% or at least 60% or at least 70% of the length of outer perimeter 208 .
  • the area of the circle defining locations (e.g. see the shaded circles of FIG. 37A ) within the subsurface formation (i.e. in the plane in which a heater pattern is defined) is exactly 5% of the area of inner zone 210 .
  • the radius of inner zone 210 equals
  • Embodiments of the present invention relate to apparatus and methods whereby, for a cross-section of the subsurface formation, and for a threshold length or threshold distance that is equal to one-eighth of the area of inner zone 204 , (i) a significant fraction of inner zone 210 is covered by the shaded circles having a radius equal to the threshold distance and an area equal to about 5% of the area of inner zone 204 ; (ii) only a significantly smaller fraction of outer zone 214 is covered by the shaded circles having a radius equal to the same threshold distance, due to the much lower heater density. In some embodiments, a significant fraction of the length of inner perimeter 204 is covered by shaded circles.
  • a ‘significant fraction’ of the length of outer perimeter 208 is covered by shaded circles.
  • a threshold distance or threshold length it is possible to set a threshold distance or threshold length to one-eighth of the area of inner zone 204 so that a magnitude of an area enclosed by a circle whose radius is the ‘threshold distance’ is equal to 5% of that of the inner zone 204 .
  • this threshold distance for the heater patterns illustrated in FIG. 5A , (i) more than 50% (for example, about 60%) of inner zone 210 is heater-displaced or teater-centroid-displaced by less than this threshold distance, and (ii) a much smaller fraction, i.e. about 15-20% of outer zone 214 is displaced by less than this threshold distance.
  • a much smaller fraction i.e. about 15-20% of outer zone 214 is displaced by less than this threshold distance.
  • a ratio between (i) a fraction of inner zone 210 that is heater-displaced or heater-centroid displaced by at most the threshold distance; and (ii) a fraction of outer zone 214 that is heater-displaced or heater-centroid displaced by at most the threshold distance is at least 1.2 or at least 1.25 or at least 1.3 or at least 1.4 or at least 1.5 or at least 1.6 or at least 1.8 or at least 1.9.
  • about 60% of a length of inner perimeter 204 is heater-displaced or heater-centroid-displaced by at most this threshold distance and about 60% of a length of outer perimeter 208 is heater-displaced or heater-centroid-displaced by at most twice this threshold distance.
  • over 75% of a length of inner perimeter 204 is heater-displaced or heater-centroid-displaced by at most this threshold distance and over 75% of a length of outer perimeter 208 is heater-displaced or heater-centroid-displaced by at most twice this threshold distance.
  • Control apparatus may include any combination of analog or digital circuitry (e.g. current or voltage or electrical power regulator(s) or electronic timing circuitry) and/or computer-executable code and/or mechanical apparatus (e.g. flow regulator(s) or pressure regulator(s) or valve(s) or temperature regulator(s)) or any monitoring devices (e.g. for measuring temperature or pressure) and/or other apparatus.
  • analog or digital circuitry e.g. current or voltage or electrical power regulator(s) or electronic timing circuitry
  • computer-executable code and/or mechanical apparatus e.g. flow regulator(s) or pressure regulator(s) or valve(s) or temperature regulator(s)
  • any monitoring devices e.g. for measuring temperature or pressure
  • Some embodiments relate to patterns of heaters and/or production wells and/or injection wells.
  • Some embodiments relate to methods of hydrocarbon fluid production and/or methods of heating a subsurface formation.
  • any feature or combination of feature(s) relating to heater and/or production well locations or patterns may be provided in combination with any method disclosed herein even if not explicitly specified herein.
  • a number of methods are disclosed within the present disclosure, each providing its own set of respective features.
  • any feature(s) of any one method may be combined with feature(s) of any other method, even if not explicitly specified herein.
  • control apparatus may be programmed to carry out any method or combination thereof disclosed herein.
  • each of the verbs, “comprise” “include” and “have”, and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of members, components, elements or parts of the subject or subjects of the verb.
  • an element means one element or more than one element.

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US9605524B2 (en) 2012-01-23 2017-03-28 Genie Ip B.V. Heater pattern for in situ thermal processing of a subsurface hydrocarbon containing formation
US10047594B2 (en) 2012-01-23 2018-08-14 Genie Ip B.V. Heater pattern for in situ thermal processing of a subsurface hydrocarbon containing formation

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US20030146002A1 (en) * 2001-04-24 2003-08-07 Vinegar Harold J. Removable heat sources for in situ thermal processing of an oil shale formation
US7546873B2 (en) * 2005-04-22 2009-06-16 Shell Oil Company Low temperature barriers for use with in situ processes
AU2007313395B2 (en) * 2006-10-13 2013-11-07 Exxonmobil Upstream Research Company Enhanced shale oil production by in situ heating using hydraulically fractured producing wells
US8113272B2 (en) * 2007-10-19 2012-02-14 Shell Oil Company Three-phase heaters with common overburden sections for heating subsurface formations
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9605524B2 (en) 2012-01-23 2017-03-28 Genie Ip B.V. Heater pattern for in situ thermal processing of a subsurface hydrocarbon containing formation
US10047594B2 (en) 2012-01-23 2018-08-14 Genie Ip B.V. Heater pattern for in situ thermal processing of a subsurface hydrocarbon containing formation

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