CA2716614A1 - Direct fired conductive subterranean heating system - Google Patents
Direct fired conductive subterranean heating system Download PDFInfo
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- CA2716614A1 CA2716614A1 CA 2716614 CA2716614A CA2716614A1 CA 2716614 A1 CA2716614 A1 CA 2716614A1 CA 2716614 CA2716614 CA 2716614 CA 2716614 A CA2716614 A CA 2716614A CA 2716614 A1 CA2716614 A1 CA 2716614A1
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- flue gas
- subterranean formation
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- combustible fluid
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Abstract
An apparatus for heating a subterranean formation to facilitate production of oil therefrom, the apparatus comprising; a downhole ignition area; a conduit to deliver oxygen, a combustible fluid or a combination thereof, to the down hole ignition area; and a return conduit that recovers flue gas from the down hole ignition area.
Description
DIRECT FIRED CONDUCTIVE SUBTERRANEAN HEATING SYSTEM
Field The invention relates to apparatus and method for production of oil from a subterranean formation.
Background Many reservoirs containing vast quantities of oil including heavy oil and bitumen have been discovered in subterranean formations. However, the recovery of oil from some subterranean formations has been very difficult due to the relatively high viscosity of the oil. In particular, when a production well is drilled into a subterranean formation to recover oil residing therein, often little or no oil flows into the production well. To overcome this problem, various thermal recovery techniques have been used to decrease the viscosity of the oil, thereby making the recovery of the oil easier. However, these techniques can be very energy intensive and can significantly change the pressure conditions in the wellbore.
A need therefore exists to provide heat to a subterranean formation and thereby improve the production of oil from the subterranean formation.
W S Legal\065151 \00002\6340527v 1 Summary In accordance with a broad aspect of the present invention, there is provided an apparatus for heating a subterranean formation to facilitate production of oil therefrom, the apparatus comprising: a downhole ignition area; a conduit to deliver oxygen, a combustible fluid or a combination thereof, to the down hole ignition area; and return conduit that recovers flue gas from the down hole ignition area.
In accordance with another broad aspect of the present invention, there is provided a method for heating subterranean formations, the method comprising: employing an apparatus installed in a subterranean formation including: a down hole ignition area; a conduit to deliver oxygen, a combustible fluid or a combination thereof, to the down hole ignition burner head; and a return conduit that recovers flue gas from the down hole ignition burner head;
igniting a mixture of oxygen and combustible fluid down hole to combust and produce heat and a flue gas; the heat produced conductively heats the subterranean formation; and the flue gas from the ignition area is returned to the surface.
In accordance with another broad aspect of the present invention, there is provided a method for heating a subterranean formation comprising: igniting a mixture of oxygen and a combustible fluid in a wellbore to combust and produce heat and a flue gas, the heat conductively heating the subterranean formation and the flue gas being returned to a surface location, the mixture of oxygen and combustible fluid and the flue gas being isolated from contact with the subterranean formation.
It is to be understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments of the invention are shown and described by way of illustration. As will be realized, the invention is capable for other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention.
Accordingly the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.
WS Legal\065151 \00002\6340527v 1 Brief Description of the Drawings Referring to the drawings, several aspects of the present invention are illustrated by way of example, and not by way of limitation, in detail in the figures, wherein:
Figure 1: a schematic illustration of a possible embodiment of the invention;
Figure 2: a schematic illustration of a possible embodiment of the invention;
Figure 3: a schematic illustration of a possible embodiment of the invention;
and Figure 4: a sectional view through one treatment string useful in the present invention.
Description of Various Embodiments The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention.
However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.
In one embodiment of the present invention, as shown in Figure 1, an apparatus may be installed in a wellbore in thermal proximity to subterranean formation 10 containing oil. The apparatus may provide a combustible mixture of oxygen and a combustible fluid through a system of conduits to the wellbore, which is ignited in the wellbore to combust and generate thermal energy. The combustible mixture of oxygen and combustible fluid may continue to be supplied to the formation to continue generating thermal energy until such generation of thermal energy is no longer needed. The apparatus may include therefore a conduit 14 extending from surface 15 for conducting oxygen from a source 16 and a fuel conduit 18 extending from surface for conducting the combustible fluid from a source 20.
The oxygen may most reasonably be in the form of air and source 16 may therefore include an inlet from the surface atmosphere. Of course, other oxygen sources, such as compressed supplies, etc. would also work well. The combustible fluid may be selected from any gas or W S Legal\065151 \00002\6340527v 1 liquid that is combustible to form thermal energy. Selection of the combustible fluid may consider cost, availability and the tendency for fouling (the cleanliness of the burn). Of course, natural gas may be readily available and generates a clean burn and, therefore, works well for this purpose. However, other combustibles such as propane, diesel and others gases and liquids.
The sources 16, 20 may include pumps, compressors, lines, tanks, etc., as will be appreciated.
The surface equipment, however, is likely to generate a small foot print.
The conduits 14, 18, terminate downhole and the oxygen and combustible fluid are allowed to mix in the wellbore in an ignition area 22 where the generation of thermal energy is desired.
Generally, the oxygen and combustible fluid are maintained separate substantially until they reach area 22 in order to prevent burn back. Ignition may occur in various ways. For example, ignition may be achieved by a flame generated at or adjacent surface which travels to area 22.
However, this may complicate the operation. In one embodiment, for example, an igniter 24 may be positioned in or adjacent area 22. The igniter may take various forms, such as a spark generator, pilot, etc. In some cases, operation of the igniter may only be required once to initiate the operation of the apparatus. However, in some other cases, the igniter may be employed from time to time to restart, or ensure continued, combustion operations.
The ignition generates combustion products including a flame 25, which generates thermal energy. The flame will be generated downstream of the igniter in area 22.
The thermal energy generated may conductively heat the surrounding subterranean formation to facilitate production of the desired products from the subterranean formation.
The generated thermal energy may directly heat oil products and/or may heat other formation fluids to indirectly heat oil products in the formation. For example, the generated thermal energy may conduct out of the apparatus and generate steam from surrounding water, which in turn heats oil products for production thereof.
The apparatus may further include a flue gas evacuation conduit 26 that provides for the evacuation of flue gas, arrows F, from combustion of the oxygen and combustible fluid within the apparatus. The conduit 26 extends from area 22 and may also provide for some heat conduction. In fact, as will be appreciated, there may be no well defined division between area W S Legal\065151\00002\6340527v1 22 and conduit 26. Conduit 26 provides a passage of flue gas to an appropriate handling area.
Generally, conduit will extend to surface and flue gas will be conducted to surface for handling.
The apparatus may provide a closed system such that oxygen, combustible fluid and combustion products, including the flame and the flue gas, all remain isolated from the formation. In such an embodiment, the apparatus may include an outer liner 28 which contains, and may in part define, the inner components of the apparatus, including conduits 14, 18, 26 and provides a substantially fluid tight outer enclosure, while permitting thermal conduction therethrough to the formation.
In one embodiment, the outer liner may be formed of a tubular string of liner (also known as casing) joints.
Because the apparatus may provide a closed system, it does not significantly affect the pressure of the formation. As such, it may have a wide range of applications, even in formations close to the surface and/or those with questionable or no cap rock. In one embodiment, for example, the apparatus may be useful at depths of 60 to 120 meters, at which the use of some systems that have fluid communication with the formation may not be permitted.
The thermal energy provided by the apparatus heats the oil in the formation, thereby allowing it to flow for production thereof. Production may be through a producing well.
Alternately, outer liner 28 may be opened to permit flow therethrough, as by removing conduits 14 and 18 and perforating the liner.
The apparatus may include a control system. For example, the flows of oxygen and combustible fluid to be mixed and ignited can be regulated to control the amount of heat produced. In one embodiment, the apparatus may contain one or more valves that regulate the flow of the combustion gasses. These valves may be positioned at various locations along the apparatus.
The control system may further include one or more sensors to provide information on process conditions. As shown in Figure 2, for example, a control system may include one or more of. a flow regulator 130, such as, for example, a throttling valve, for controlling flow through oxygen conduit 114, a flow regulator 132, such as, for example, a throttling valve, for controlling flow through fuel conduit 118, a temperature sensor 134 at a position downhole to detect process temperature and a flue gas monitor 138 for monitoring flue gas characteristics, such as content, temperature, flow rate, etc. The temperature and/or flue gas condition information may be W S Legal\065151 \00002\6340527v 1 communicated to controllers such as directly on regulator 130 and/or regulator 132 or to a control location, such as a surface monitor 136, which indirectly or directly communicates 137 to regulator 130 and/or regulator 132.
Control system components and processes may vary depending on a number of factors, including process conditions, familiarity with apparatus function, etc. For example, during initial operations, there may be redundancy of temperature sensors and flue gas monitors. However, over time, it may be that these redundancies are reduced or eliminated.
The apparatus may further include a flue gas injection system. For example, if desired, the flue gas generated in area 122 can be recovered, in whole or in part, from conduit 126 at surface 115, and pumped back downhole. In one embodiment, therefore, the apparatus may include a flue gas handling system 140, such as for example, including one or more of a compressor, a pump, etc., to condition at least some of the returning flue gas for injection downhole and direct the flue gas, arrows Fi, into a flue gas injection conduit 142. In one embodiment, the flue gas may be mixed with solvents and the flue gas/solvent mixture may be injected downhole to further facilitate production of oil products. Solvents may be added from a solvent source 144 associated with the handling system 140. Suitable solvents may be known to those skilled in the art and may include, for example, propane.
The conduit may extend into a formation of interest. In one embodiment, conduit 142 may extend alongside the outer liner to access the same formation 110 in which the direct heating is occurring. Conduit 142 may include openings 145 through its walls, such that the recovered flue gas, and possibly entrained solvent, may directly access the formation through the openings in the flue gas injection conduit. Injection of flue gas, with or without solvent, may provide for enhanced environmental controls and may further facilitate production of the desired oil products from the subterranean formation.
With reference to Figure 3, another apparatus is shown for installation in a wellbore in thermal proximity to a subterranean formation 210. The apparatus provides oxygen and a combustible fluid through conduits 214, 218 to the wellbore, where the oxygen and combustible fluid is mixed and ignited. The resulting combustion generates thermal energy in the wellbore, which W S Legal\06 5151 \00002\6340527v 1 conducts to the formation to heat, directly or indirectly, the oil of the formation and to facilitate production thereof.
The oxygen may be in the form of air and the combustible may be selected from any gas or liquid that is combustible to form thermal energy. Selection of the combustible fluid may consider cost, availability and the tendency for fouling (the cleanliness of the burn). Of course, natural gas may be readily available and generates a clean burn and, therefore, works well for this purpose. However, other combustibles may also or alternatively be employed such as propane, diesel and others gases and liquids. The sources may include pumps, compressors, lines, tanks, etc., as will be appreciated. The surface equipment, however, is likely to generate a small foot print.
The conduits 214, 218 terminate in the wellbore and the oxygen and combustible fluid conveyed therethrough are allowed to mix in area 222. Generally, the oxygen and the combustible fluid are maintained separate until they reach area 222 in order to prevent burn back. A fuel handler 223 may be provided in area 222 to ready the fuel for combustion thereof. Fuel handler 223 may take various forms depending on the characteristics of the combustible fluid.
For example, the fuel handler may include fluid outlets, nozzles, back flow regulators, mixers, etc. For example, if the combustible fluid is a liquid, the fuel handler may include, for example, an atomizer and a mixer to mix the atomized liquid and the oxygen. If the combustible fluid is a gas, the fuel handler may include, for example, nozzles for outlet of the gasses and a mixer. In one embodiment, for example, fuel handler may include one or more baffles positioned in area 222.
A baffle arrangement creates turbulence in the fluids passing thereby to facilitate mixing thereof in preparation for ignition and also reduces the chances of burn back.
Ignition of the fuel mixture may occur in various ways. In one embodiment, for example, an igniter 224 may be positioned in or adjacent area 222. The igniter may take various forms, such as a spark generator, pilot, etc. In this embodiment, igniter 224 is electrically powered through an electrical connection, for example, extending from surface. Ignition of the fuel mixture generates a flame 225.
The apparatus may further include a flue gas evacuation conduit 226 that will initially accommodate the flame and thereafter provides for the evacuation of flue gas, arrows F, from WS Legal\065151 \00002\6340527v 1 combustion of the oxygen and combustible fluid within the apparatus. The conduit 226 provides a passage of flue gas to an appropriate handling area. Generally, flue gas will be conducted to surface 215 for handling. In one embodiment, to control flue gas evacuation, a valve 227 is provided to act as a damper to control flow through conduit 226. Valve 227 may be adjusted to regulate the flue gas evacuation rate, which may control residence time and reduce the generation of a vacuum effect by up drafting. If the valve is adjusted to restrict the flow rate of flue gas through conduit, for example, residence time of the flue gas in the well may be increased such that the burn may be affected and the latent heat of the flue gas may be conducted to the formation. If valve 227 is adjusted to further open the conduit to fluid flow, the flue gas may evacuate at an increased rate from the well, which may lower the temperature in the well and affect the burn.
The apparatus may provide a closed system such that oxygen, combustible fluid and combustion products, including the flame and the flue gas, remain isolated and out of contact from the formation. In such an embodiment, the apparatus may include an outer liner 228 which contains, and may form in part, the inner components of the apparatus, including conduits 214, 218, 226 and provides a substantially fluid tight outer enclosure, while permitting thermal conduction therethrough to the formation.
One useful treatment apparatus is shown, for example, in Figures 3 and 4. The illustrated treatment apparatus, along its downhole treatment section includes an outer liner 228, an intermediate tubing string 246 extending along the inner bore of the outer liner and an inner tubing string 248 extending along the inner bore of the intermediate tubing string. Outer liner 228 includes an end wall 228a and strings 246, 248 terminate within the outer liner. The outer liner thus forms an outer enclosure and defines the outer limits of the wellbore installation.
The tubing-in-tubing arrangement creates three fluid flow spaces: the first through inner bore defined within inner walls 248a of tubing string, the second between the outer wall of tubing string 248 and inner wall 246a of intermediate tubing string 246 and the third flow space between the outer wall 246b of intermediate tubing string 246 and the inner wall of outer liner 228. The flow spaces define area 222 and define conduits 214, 218, 226 for passage therethrough of the oxygen, the combustible fluid and the flue gas.
W S Legal\06 5151 \00002\6340527v 1 Since the heat of combustion is to be conducted through the apparatus into the formation, the combustion reaction area 222 and flue gas conduit 226 most reasonably are placed in the flow passage between the outer wall 246b of intermediate tubing string 246 and the inner wall of outer liner 228. As such, the thermal energy is generated, and the products of combustion flow, directly in contact with outer liner 228 such that the heat can conduct directly therethrough to the formation.
The oxygen and combustible fluid can pass through the first and second flow passages. In one embodiment, the space between the outer wall of tubing string 248 and inner wall 246a of intermediate tubing string 246 may form conduit 214 for oxygen and the combustible fluid may be conveyed downhole through the bore of inner tubing string 248.
As noted previously, the oxygen may be in the form of air. The air flow may provide an insulative and/or a cooling effect between the high temperature conditions in conduit 226 and inner tubing string 248. As such, it may be of interest to position more heat sensitive components, such as electrical lines, along or through inner tubing string 248.
Spacers may be employed to maintain the spacing between the strings and between the intermediate string and the outer liner, if desired.
In one embodiment, inner string 248 and possibly also intermediate string 246 may be independently trippable relative to outer liner 228. For example, inner string 248 and possibly also intermediate string 246 may be removable from outer string 228, while the outer string remains in the well. As such, it may be desirable to mount fatigable and/or replaceable mechanisms on the strings 248 or 246. In one embodiment, for example, inner string 248 is formed to be removable and replaceable from within intermediate string 246 and at least some components including one or both of sensors, electrical conductors, igniter 224 and fluid handler 223 are mounted on (secured to or embedded in the material of) the string and can be withdrawn from the well with the inner string, for inspection, replacement, or repair.
Alternately, at least some components can be engageable by strings 246 or 248 such that they can be independently mounted downhole but engageable as by spearing by one of the strings for tripping out of the hole.
W S Legal\065151 \00002\6340527v 1 In one embodiment, the outer liner may be formed of a tubular liner string formed of threaded pipe (liner or casing) joints, intermediate tubing string 246 may be formed of threaded pipe (drill, liner or casing) joints or coiled tubing, inner string 248 may be formed of threaded pipe joints or coiled tubing. The selection of a string material should be made with the consideration of downhole conditions including thermal conduction, durability, etc. and may be made with consideration to cost, tripability, etc. For example, the use of coiled tubing may be of interest, for a string that is to be conveniently removable.
In one embodiment, the apparatus may be configured to define a plurality of heating zones along its length to extend the length along which combustion may occur and, therefore, along which heat may be conducted into the formation. Each heating zone, for example, may include a fuel handler to at least emit oxygen and combustible fluid into a combustion area.
For example, in addition to fuel handler 223, a second fuel handler 223a is positioned downstream, further along conduit 226. Fuel handler 223a has an oxygen supply from conduit 214 and a combustible fluid supply from conduit 218 such that another flame can be generated in this heating zone. In such an embodiment, nozzles may be employed to control the outlet of oxygen and combustible fluid to control the pressure profile along the conduits 214, 218. For example, system nozzles may be employed at the spaced apart fuel handlers 223, 223a to ensure that the supply of fuel gases is graduated along the string, such that outlets downstream continue to have adequate supply.
The apparatus may include a control system. For example, the flows of oxygen and combustible fluid to be mixed and ignited can be regulated to control the amount of heat produced. For example, control system may include one or more of. an oxygen flow regulator, such as, for example, a throttling valve 230, for controlling flow through oxygen conduit 214, a flow regulator such as, for example, a throttling valve 232, for controlling flow through fuel conduit 218, a fluid gas valve 227, a temperature sensor, such as a thermocouple 234, at a position downhole to detect process temperature and a flue gas monitor 238 for monitoring conditions of flue gas, such as content, temperature, pressure, flow rate, etc. The flue gas conditions and/or downhole temperature information is communicated to a control location, such as directly to valves 230, 232 and/or 227 or to a surface or remote monitor 239 and then to valves 230, 232 and/or 227.
W S Legal\065151 \00002\6340527v 1 In one embodiment, for example, the control system seeks to maintain the process temperature between an upper temperature and a lower temperature. The upper and lower temperatures may be selected with consideration as to desired process and apparatus parameters.
For example, the lower temperature may be selected as the temperature on or about which the formation may be suitably heated by conduction to facilitate production thereof. The upper temperature may be selected to be less than the temperature at which apparatus failures will occur, as can be readily determined by a review of apparatus components, such as liners, thermocouples (temperature sensors), wiring, etc. Generally also, the upper temperature may be selected to be below that temperature at which the formation may not respond appropriately. For example, the upper temperature may be selected to be below that temperature at which coking may occur on the outside of the apparatus or below the temperature at which a steam jacket may form about the apparatus. In one embodiment, the upper and lower temperatures are selected to be a range +/-50 C about a desire process temperature, based on formation heating conditions of interest.
It may be desirable to control the system such that a temperature is maintained substantially continuously within the range between the upper and lower temperatures.
Increases in oxygen and/or combustible fluid flow may cause an increase in heat produced.
Similarly, decreases in the flow rate of these fluids may cause a decrease in heat produced. For example, after start-up, the control system may respond to a temperature sensed downhole, for example from temperature sensor 234, such that the flow of the oxygen and/or the combustible fluid to area 222 may continue until a lower temperature threshold is reached. Further, flow of the oxygen and/or combustible fluid may be decreased or stopped when an upper predetermined temperature is reached.
In one embodiment, further or alternative control mechanisms may be employed.
For example, the flow of oxygen and /or combustible fluid can be regulated by a thermally controlled valve 250 (in this case in fluid handler 223a) positioned downhole in area 222. A
thermally controlled valve can act in response to a sensed temperature, if desired, without a control signal, without a power input and without an external mechanical actuation. The thermally controlled valve may increase and/or decrease the flow of a fluid passing therethrough.
W S Legal\06 5151 \00002\6340527v 1 In another embodiment, a plurality of downhole temperature sensors are employed, spaced apart along the length of the string. For example, further temperature sensors 234a, 234b may be spaced apart along liner 230 to permit determination of the temperature profile therealong. If it is determined that a section of undesirable temperature is developing along the length of the liner 230, one or more of valves 230, 232 and/or 227 may be actuated to affect the heat generated at that point either by adjusting the location of the flame, adjusting the heat of the flame and/or by effecting the evacuation rate of the flue gas.
If the apparatus includes more than one heating zone, the control system may sense conditions in one or more of the plural zones and regulate one or more of the fuel handling areas simultaneously or individually. For example, the regulated flow of the fuel gasses may be isolated to individual heating zones or may occur such that any flow regulation is communicated throughout the apparatus. In one embodiment, condition sensing may occur at various locations along the treatment string so that the regulation of fuel gas, for example oxygen, flow into the plural heating zones may be appropriate for the conditions in each zone. For example, in one embodiment, a temperature sensor may be positioned in each of a plurality of locations along the string and a valve may be provided in each of a plurality of heat zones to increase or decrease the flow of at least one of the fuel gasses to each such zone. As such, a particular temperature, for example, between the upper and lower temperature thresholds may be maintained in each of the plurality of heat zones.
For example, in one embodiment of the present invention the apparatus may have a first heating zone and a second heating zone adjacent to the first heating zone and the first and second heating zones may each be monitored for at least one process condition and combustion in each zone may be independently controlled. For example, the apparatus may be controlled to create a substantially uniform temperature profile across the plurality of heating zones. One heating zone may be controlled separately and perhaps isolated from the other heating zones.
Control system components and processes may vary depending on a number of factors, including familiarity with apparatus function, process conditions, etc. For example, during initial operations, there may be redundancy of temperature sensors and flue gas monitors. However, over time, it may occur that these redundancies are reduced or eliminated.
W S Legal\065151\00002\6340527v1 The apparatus may further include a flue gas injection system. For example, if desired, the flue gas can be recovered, in whole or in part, from conduit 226, and pumped back downhole. In one embodiment, therefore, the apparatus may include a flue gas handling system 240, such as for example, including one or more of a compressor, a pump, etc., to condition the flue gas for injection downhole and to direct the flue gas into a flue gas injection conduit 242. In one embodiment, the flue gas may be mixed with solvents to further facilitate production of oil products. Solvents may be added from a solvent source 244 associated with handling system 240. Suitable solvents may be known to those skilled in the art and include for example propane.
The conduit may extend into a formation of interest. In one embodiment, conduit 242 may be connected to outer liner 230 to access the same formation in which the direct heating is occurring. Conduit 242 may include openings 245 through its walls, such that the recovered flue gas, and possibly entrained solvent, may directly access the formation through those openings.
Injection of flue gas, with or without, solvent may provide for enhanced environmental controls and may facilitate production of the desired products from the subterranean formation.
There may be a plurality of valves 247 along the conduit that regulate the injection of recovered flue gas and possibly solvents by increasing or decreasing the flow into the subterranean formation. In such an embodiment, recovered flue gas and possibly solvents can be injected into a first heating zone without also being released into the second heating zone, it having been decided that production in the second heating zone is not currently of interest or it having been determined that the second heating zone is already of a desired thermal condition.
To install the apparatus, a wellbore must be drilled into the formation of interest. The formation of interest may be an oil-containing formation that would be advantaged by input of thermal energy thereto or a formation adjacent an oil-containing formation that would be advantaged by input of thermal energy thereto. The wellbore may be drilled through, above, below or alongside an oil-containing formation. Generally, the wellbore may extend along a horizontal section.
The apparatus is run into the well and set in place with conduits 214, 218, 226 in fluid communication with surface and any electrical or other communications connected. For example, in one embodiment, outer liner 228 is run into the wellbore and set in place. The outer liner may have its outer surface in communication and possibly in contact with the formation of WS Legal\065151\00002\6340527v 1 interest. While annular treatments, such as gravel packs, cementing, etc. may be accommodated, care might to taken to avoid any disadvantageous reductions in the possible thermal conduction from the liner to the formation. The outer liner may extend entirely to surface or, as shown, be connected into an uphole liner string. In such an embodiment, the outer liner may be connected by any of various liner hanger/packer assemblies 250. Consideration may be given as to the thermal conditions to be withstood downhole and appropriate selections made.
For example, in one embodiment, a metal to metal packer may be employed.
If a flue gas injection conduit is to be provided, that conduit may be run with the liner. For example, the flue gas injection conduit may be connected to the liner, as by strapping, welding, forming integral therewith, etc.
Once the liner is in place, the intermediate and inner tubing strings may be run in to the portion of the liner in which the direct heating is to occur. Generally, the treatment string in which direct heating is to occur extends along a horizontal section of a wellbore, but other configurations can be accommodated.
The conduits thus formed are then connected to a surface wellhead apparatus including inlets, valves, etc.
In one embodiment, a production well 260 may be positioned or existing adjacent to the wellbore in which the apparatus is positioned. The producing well may be directly or offset below the direct heat wellbore or may be above or alongside it. A production well may include various components such as a slotted liner 262, a pump 264 and/or a production string 266 to permit the produced oil to be conducted to surface 215.
A method for heating subterranean formations is provided. The method includes:
igniting a mixture of oxygen and a combustible fluid in a wellbore to combust and produce heat and a flue gas. The heat produced conductively heats the subterranean formation through.
The flue gas is returned to the surface. The thermal energy generated may conductively heat the surrounding subterranean formation to facilitate production of the desired products from the subterranean formation. The generated thermal energy may directly heat oil products and/or may heat other formation fluids to indirectly heat oil products in the formation. For example, the generated W S Legal\06 5151 \00002\6340527v 1 thermal energy may conduct out of the apparatus and generate steam from surrounding formation water, which in turn heats oil products for production thereof.
The flue gas may be maintained out of contact with the formation such that the method does not introduce any foreign fluids to the formation. Thus, the method may avoid any significant change in the pressure of the formation. As such, the method may have a wide range of applications, even in formations close to the surface and/or those with questionable or no cap rock. In one embodiment, for example, the apparatus may be useful at depths of 60 to 120 meters.
In another embodiment, for example, where there are environmental concerns relating to the release of flue gas, the flue gas may be collected at surface and injected downhole. Such injection may include processing of the flue gas at surface, for example, compression and pumping thereof. The injection may be to the formation of interest or to another formation. This may affect the formation pressure.
The formation heating that occurs reduces the viscosity of the oil in the formation and facilitates its production. In one embodiment, the oil is produced through an adjacent producing well. In another embodiment, after heating of the formation, the outer liner can be converted to a producing liner, as by opening ports therethrough (i.e. perforating the liner or opening existing, but previously closed ports) and allowing inflow of oil, which is moved to surface.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from scope of the invention.
Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article "a" or "an" is not intended to mean "one and only one"
unless specifically so stated, but rather "one or more". All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are know or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the WS Legal\065151 \00002\6340527v 1 claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.
W SLegal\065151 \00002\6340527v 1
Field The invention relates to apparatus and method for production of oil from a subterranean formation.
Background Many reservoirs containing vast quantities of oil including heavy oil and bitumen have been discovered in subterranean formations. However, the recovery of oil from some subterranean formations has been very difficult due to the relatively high viscosity of the oil. In particular, when a production well is drilled into a subterranean formation to recover oil residing therein, often little or no oil flows into the production well. To overcome this problem, various thermal recovery techniques have been used to decrease the viscosity of the oil, thereby making the recovery of the oil easier. However, these techniques can be very energy intensive and can significantly change the pressure conditions in the wellbore.
A need therefore exists to provide heat to a subterranean formation and thereby improve the production of oil from the subterranean formation.
W S Legal\065151 \00002\6340527v 1 Summary In accordance with a broad aspect of the present invention, there is provided an apparatus for heating a subterranean formation to facilitate production of oil therefrom, the apparatus comprising: a downhole ignition area; a conduit to deliver oxygen, a combustible fluid or a combination thereof, to the down hole ignition area; and return conduit that recovers flue gas from the down hole ignition area.
In accordance with another broad aspect of the present invention, there is provided a method for heating subterranean formations, the method comprising: employing an apparatus installed in a subterranean formation including: a down hole ignition area; a conduit to deliver oxygen, a combustible fluid or a combination thereof, to the down hole ignition burner head; and a return conduit that recovers flue gas from the down hole ignition burner head;
igniting a mixture of oxygen and combustible fluid down hole to combust and produce heat and a flue gas; the heat produced conductively heats the subterranean formation; and the flue gas from the ignition area is returned to the surface.
In accordance with another broad aspect of the present invention, there is provided a method for heating a subterranean formation comprising: igniting a mixture of oxygen and a combustible fluid in a wellbore to combust and produce heat and a flue gas, the heat conductively heating the subterranean formation and the flue gas being returned to a surface location, the mixture of oxygen and combustible fluid and the flue gas being isolated from contact with the subterranean formation.
It is to be understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments of the invention are shown and described by way of illustration. As will be realized, the invention is capable for other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention.
Accordingly the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.
WS Legal\065151 \00002\6340527v 1 Brief Description of the Drawings Referring to the drawings, several aspects of the present invention are illustrated by way of example, and not by way of limitation, in detail in the figures, wherein:
Figure 1: a schematic illustration of a possible embodiment of the invention;
Figure 2: a schematic illustration of a possible embodiment of the invention;
Figure 3: a schematic illustration of a possible embodiment of the invention;
and Figure 4: a sectional view through one treatment string useful in the present invention.
Description of Various Embodiments The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention.
However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.
In one embodiment of the present invention, as shown in Figure 1, an apparatus may be installed in a wellbore in thermal proximity to subterranean formation 10 containing oil. The apparatus may provide a combustible mixture of oxygen and a combustible fluid through a system of conduits to the wellbore, which is ignited in the wellbore to combust and generate thermal energy. The combustible mixture of oxygen and combustible fluid may continue to be supplied to the formation to continue generating thermal energy until such generation of thermal energy is no longer needed. The apparatus may include therefore a conduit 14 extending from surface 15 for conducting oxygen from a source 16 and a fuel conduit 18 extending from surface for conducting the combustible fluid from a source 20.
The oxygen may most reasonably be in the form of air and source 16 may therefore include an inlet from the surface atmosphere. Of course, other oxygen sources, such as compressed supplies, etc. would also work well. The combustible fluid may be selected from any gas or W S Legal\065151 \00002\6340527v 1 liquid that is combustible to form thermal energy. Selection of the combustible fluid may consider cost, availability and the tendency for fouling (the cleanliness of the burn). Of course, natural gas may be readily available and generates a clean burn and, therefore, works well for this purpose. However, other combustibles such as propane, diesel and others gases and liquids.
The sources 16, 20 may include pumps, compressors, lines, tanks, etc., as will be appreciated.
The surface equipment, however, is likely to generate a small foot print.
The conduits 14, 18, terminate downhole and the oxygen and combustible fluid are allowed to mix in the wellbore in an ignition area 22 where the generation of thermal energy is desired.
Generally, the oxygen and combustible fluid are maintained separate substantially until they reach area 22 in order to prevent burn back. Ignition may occur in various ways. For example, ignition may be achieved by a flame generated at or adjacent surface which travels to area 22.
However, this may complicate the operation. In one embodiment, for example, an igniter 24 may be positioned in or adjacent area 22. The igniter may take various forms, such as a spark generator, pilot, etc. In some cases, operation of the igniter may only be required once to initiate the operation of the apparatus. However, in some other cases, the igniter may be employed from time to time to restart, or ensure continued, combustion operations.
The ignition generates combustion products including a flame 25, which generates thermal energy. The flame will be generated downstream of the igniter in area 22.
The thermal energy generated may conductively heat the surrounding subterranean formation to facilitate production of the desired products from the subterranean formation.
The generated thermal energy may directly heat oil products and/or may heat other formation fluids to indirectly heat oil products in the formation. For example, the generated thermal energy may conduct out of the apparatus and generate steam from surrounding water, which in turn heats oil products for production thereof.
The apparatus may further include a flue gas evacuation conduit 26 that provides for the evacuation of flue gas, arrows F, from combustion of the oxygen and combustible fluid within the apparatus. The conduit 26 extends from area 22 and may also provide for some heat conduction. In fact, as will be appreciated, there may be no well defined division between area W S Legal\065151\00002\6340527v1 22 and conduit 26. Conduit 26 provides a passage of flue gas to an appropriate handling area.
Generally, conduit will extend to surface and flue gas will be conducted to surface for handling.
The apparatus may provide a closed system such that oxygen, combustible fluid and combustion products, including the flame and the flue gas, all remain isolated from the formation. In such an embodiment, the apparatus may include an outer liner 28 which contains, and may in part define, the inner components of the apparatus, including conduits 14, 18, 26 and provides a substantially fluid tight outer enclosure, while permitting thermal conduction therethrough to the formation.
In one embodiment, the outer liner may be formed of a tubular string of liner (also known as casing) joints.
Because the apparatus may provide a closed system, it does not significantly affect the pressure of the formation. As such, it may have a wide range of applications, even in formations close to the surface and/or those with questionable or no cap rock. In one embodiment, for example, the apparatus may be useful at depths of 60 to 120 meters, at which the use of some systems that have fluid communication with the formation may not be permitted.
The thermal energy provided by the apparatus heats the oil in the formation, thereby allowing it to flow for production thereof. Production may be through a producing well.
Alternately, outer liner 28 may be opened to permit flow therethrough, as by removing conduits 14 and 18 and perforating the liner.
The apparatus may include a control system. For example, the flows of oxygen and combustible fluid to be mixed and ignited can be regulated to control the amount of heat produced. In one embodiment, the apparatus may contain one or more valves that regulate the flow of the combustion gasses. These valves may be positioned at various locations along the apparatus.
The control system may further include one or more sensors to provide information on process conditions. As shown in Figure 2, for example, a control system may include one or more of. a flow regulator 130, such as, for example, a throttling valve, for controlling flow through oxygen conduit 114, a flow regulator 132, such as, for example, a throttling valve, for controlling flow through fuel conduit 118, a temperature sensor 134 at a position downhole to detect process temperature and a flue gas monitor 138 for monitoring flue gas characteristics, such as content, temperature, flow rate, etc. The temperature and/or flue gas condition information may be W S Legal\065151 \00002\6340527v 1 communicated to controllers such as directly on regulator 130 and/or regulator 132 or to a control location, such as a surface monitor 136, which indirectly or directly communicates 137 to regulator 130 and/or regulator 132.
Control system components and processes may vary depending on a number of factors, including process conditions, familiarity with apparatus function, etc. For example, during initial operations, there may be redundancy of temperature sensors and flue gas monitors. However, over time, it may be that these redundancies are reduced or eliminated.
The apparatus may further include a flue gas injection system. For example, if desired, the flue gas generated in area 122 can be recovered, in whole or in part, from conduit 126 at surface 115, and pumped back downhole. In one embodiment, therefore, the apparatus may include a flue gas handling system 140, such as for example, including one or more of a compressor, a pump, etc., to condition at least some of the returning flue gas for injection downhole and direct the flue gas, arrows Fi, into a flue gas injection conduit 142. In one embodiment, the flue gas may be mixed with solvents and the flue gas/solvent mixture may be injected downhole to further facilitate production of oil products. Solvents may be added from a solvent source 144 associated with the handling system 140. Suitable solvents may be known to those skilled in the art and may include, for example, propane.
The conduit may extend into a formation of interest. In one embodiment, conduit 142 may extend alongside the outer liner to access the same formation 110 in which the direct heating is occurring. Conduit 142 may include openings 145 through its walls, such that the recovered flue gas, and possibly entrained solvent, may directly access the formation through the openings in the flue gas injection conduit. Injection of flue gas, with or without solvent, may provide for enhanced environmental controls and may further facilitate production of the desired oil products from the subterranean formation.
With reference to Figure 3, another apparatus is shown for installation in a wellbore in thermal proximity to a subterranean formation 210. The apparatus provides oxygen and a combustible fluid through conduits 214, 218 to the wellbore, where the oxygen and combustible fluid is mixed and ignited. The resulting combustion generates thermal energy in the wellbore, which W S Legal\06 5151 \00002\6340527v 1 conducts to the formation to heat, directly or indirectly, the oil of the formation and to facilitate production thereof.
The oxygen may be in the form of air and the combustible may be selected from any gas or liquid that is combustible to form thermal energy. Selection of the combustible fluid may consider cost, availability and the tendency for fouling (the cleanliness of the burn). Of course, natural gas may be readily available and generates a clean burn and, therefore, works well for this purpose. However, other combustibles may also or alternatively be employed such as propane, diesel and others gases and liquids. The sources may include pumps, compressors, lines, tanks, etc., as will be appreciated. The surface equipment, however, is likely to generate a small foot print.
The conduits 214, 218 terminate in the wellbore and the oxygen and combustible fluid conveyed therethrough are allowed to mix in area 222. Generally, the oxygen and the combustible fluid are maintained separate until they reach area 222 in order to prevent burn back. A fuel handler 223 may be provided in area 222 to ready the fuel for combustion thereof. Fuel handler 223 may take various forms depending on the characteristics of the combustible fluid.
For example, the fuel handler may include fluid outlets, nozzles, back flow regulators, mixers, etc. For example, if the combustible fluid is a liquid, the fuel handler may include, for example, an atomizer and a mixer to mix the atomized liquid and the oxygen. If the combustible fluid is a gas, the fuel handler may include, for example, nozzles for outlet of the gasses and a mixer. In one embodiment, for example, fuel handler may include one or more baffles positioned in area 222.
A baffle arrangement creates turbulence in the fluids passing thereby to facilitate mixing thereof in preparation for ignition and also reduces the chances of burn back.
Ignition of the fuel mixture may occur in various ways. In one embodiment, for example, an igniter 224 may be positioned in or adjacent area 222. The igniter may take various forms, such as a spark generator, pilot, etc. In this embodiment, igniter 224 is electrically powered through an electrical connection, for example, extending from surface. Ignition of the fuel mixture generates a flame 225.
The apparatus may further include a flue gas evacuation conduit 226 that will initially accommodate the flame and thereafter provides for the evacuation of flue gas, arrows F, from WS Legal\065151 \00002\6340527v 1 combustion of the oxygen and combustible fluid within the apparatus. The conduit 226 provides a passage of flue gas to an appropriate handling area. Generally, flue gas will be conducted to surface 215 for handling. In one embodiment, to control flue gas evacuation, a valve 227 is provided to act as a damper to control flow through conduit 226. Valve 227 may be adjusted to regulate the flue gas evacuation rate, which may control residence time and reduce the generation of a vacuum effect by up drafting. If the valve is adjusted to restrict the flow rate of flue gas through conduit, for example, residence time of the flue gas in the well may be increased such that the burn may be affected and the latent heat of the flue gas may be conducted to the formation. If valve 227 is adjusted to further open the conduit to fluid flow, the flue gas may evacuate at an increased rate from the well, which may lower the temperature in the well and affect the burn.
The apparatus may provide a closed system such that oxygen, combustible fluid and combustion products, including the flame and the flue gas, remain isolated and out of contact from the formation. In such an embodiment, the apparatus may include an outer liner 228 which contains, and may form in part, the inner components of the apparatus, including conduits 214, 218, 226 and provides a substantially fluid tight outer enclosure, while permitting thermal conduction therethrough to the formation.
One useful treatment apparatus is shown, for example, in Figures 3 and 4. The illustrated treatment apparatus, along its downhole treatment section includes an outer liner 228, an intermediate tubing string 246 extending along the inner bore of the outer liner and an inner tubing string 248 extending along the inner bore of the intermediate tubing string. Outer liner 228 includes an end wall 228a and strings 246, 248 terminate within the outer liner. The outer liner thus forms an outer enclosure and defines the outer limits of the wellbore installation.
The tubing-in-tubing arrangement creates three fluid flow spaces: the first through inner bore defined within inner walls 248a of tubing string, the second between the outer wall of tubing string 248 and inner wall 246a of intermediate tubing string 246 and the third flow space between the outer wall 246b of intermediate tubing string 246 and the inner wall of outer liner 228. The flow spaces define area 222 and define conduits 214, 218, 226 for passage therethrough of the oxygen, the combustible fluid and the flue gas.
W S Legal\06 5151 \00002\6340527v 1 Since the heat of combustion is to be conducted through the apparatus into the formation, the combustion reaction area 222 and flue gas conduit 226 most reasonably are placed in the flow passage between the outer wall 246b of intermediate tubing string 246 and the inner wall of outer liner 228. As such, the thermal energy is generated, and the products of combustion flow, directly in contact with outer liner 228 such that the heat can conduct directly therethrough to the formation.
The oxygen and combustible fluid can pass through the first and second flow passages. In one embodiment, the space between the outer wall of tubing string 248 and inner wall 246a of intermediate tubing string 246 may form conduit 214 for oxygen and the combustible fluid may be conveyed downhole through the bore of inner tubing string 248.
As noted previously, the oxygen may be in the form of air. The air flow may provide an insulative and/or a cooling effect between the high temperature conditions in conduit 226 and inner tubing string 248. As such, it may be of interest to position more heat sensitive components, such as electrical lines, along or through inner tubing string 248.
Spacers may be employed to maintain the spacing between the strings and between the intermediate string and the outer liner, if desired.
In one embodiment, inner string 248 and possibly also intermediate string 246 may be independently trippable relative to outer liner 228. For example, inner string 248 and possibly also intermediate string 246 may be removable from outer string 228, while the outer string remains in the well. As such, it may be desirable to mount fatigable and/or replaceable mechanisms on the strings 248 or 246. In one embodiment, for example, inner string 248 is formed to be removable and replaceable from within intermediate string 246 and at least some components including one or both of sensors, electrical conductors, igniter 224 and fluid handler 223 are mounted on (secured to or embedded in the material of) the string and can be withdrawn from the well with the inner string, for inspection, replacement, or repair.
Alternately, at least some components can be engageable by strings 246 or 248 such that they can be independently mounted downhole but engageable as by spearing by one of the strings for tripping out of the hole.
W S Legal\065151 \00002\6340527v 1 In one embodiment, the outer liner may be formed of a tubular liner string formed of threaded pipe (liner or casing) joints, intermediate tubing string 246 may be formed of threaded pipe (drill, liner or casing) joints or coiled tubing, inner string 248 may be formed of threaded pipe joints or coiled tubing. The selection of a string material should be made with the consideration of downhole conditions including thermal conduction, durability, etc. and may be made with consideration to cost, tripability, etc. For example, the use of coiled tubing may be of interest, for a string that is to be conveniently removable.
In one embodiment, the apparatus may be configured to define a plurality of heating zones along its length to extend the length along which combustion may occur and, therefore, along which heat may be conducted into the formation. Each heating zone, for example, may include a fuel handler to at least emit oxygen and combustible fluid into a combustion area.
For example, in addition to fuel handler 223, a second fuel handler 223a is positioned downstream, further along conduit 226. Fuel handler 223a has an oxygen supply from conduit 214 and a combustible fluid supply from conduit 218 such that another flame can be generated in this heating zone. In such an embodiment, nozzles may be employed to control the outlet of oxygen and combustible fluid to control the pressure profile along the conduits 214, 218. For example, system nozzles may be employed at the spaced apart fuel handlers 223, 223a to ensure that the supply of fuel gases is graduated along the string, such that outlets downstream continue to have adequate supply.
The apparatus may include a control system. For example, the flows of oxygen and combustible fluid to be mixed and ignited can be regulated to control the amount of heat produced. For example, control system may include one or more of. an oxygen flow regulator, such as, for example, a throttling valve 230, for controlling flow through oxygen conduit 214, a flow regulator such as, for example, a throttling valve 232, for controlling flow through fuel conduit 218, a fluid gas valve 227, a temperature sensor, such as a thermocouple 234, at a position downhole to detect process temperature and a flue gas monitor 238 for monitoring conditions of flue gas, such as content, temperature, pressure, flow rate, etc. The flue gas conditions and/or downhole temperature information is communicated to a control location, such as directly to valves 230, 232 and/or 227 or to a surface or remote monitor 239 and then to valves 230, 232 and/or 227.
W S Legal\065151 \00002\6340527v 1 In one embodiment, for example, the control system seeks to maintain the process temperature between an upper temperature and a lower temperature. The upper and lower temperatures may be selected with consideration as to desired process and apparatus parameters.
For example, the lower temperature may be selected as the temperature on or about which the formation may be suitably heated by conduction to facilitate production thereof. The upper temperature may be selected to be less than the temperature at which apparatus failures will occur, as can be readily determined by a review of apparatus components, such as liners, thermocouples (temperature sensors), wiring, etc. Generally also, the upper temperature may be selected to be below that temperature at which the formation may not respond appropriately. For example, the upper temperature may be selected to be below that temperature at which coking may occur on the outside of the apparatus or below the temperature at which a steam jacket may form about the apparatus. In one embodiment, the upper and lower temperatures are selected to be a range +/-50 C about a desire process temperature, based on formation heating conditions of interest.
It may be desirable to control the system such that a temperature is maintained substantially continuously within the range between the upper and lower temperatures.
Increases in oxygen and/or combustible fluid flow may cause an increase in heat produced.
Similarly, decreases in the flow rate of these fluids may cause a decrease in heat produced. For example, after start-up, the control system may respond to a temperature sensed downhole, for example from temperature sensor 234, such that the flow of the oxygen and/or the combustible fluid to area 222 may continue until a lower temperature threshold is reached. Further, flow of the oxygen and/or combustible fluid may be decreased or stopped when an upper predetermined temperature is reached.
In one embodiment, further or alternative control mechanisms may be employed.
For example, the flow of oxygen and /or combustible fluid can be regulated by a thermally controlled valve 250 (in this case in fluid handler 223a) positioned downhole in area 222. A
thermally controlled valve can act in response to a sensed temperature, if desired, without a control signal, without a power input and without an external mechanical actuation. The thermally controlled valve may increase and/or decrease the flow of a fluid passing therethrough.
W S Legal\06 5151 \00002\6340527v 1 In another embodiment, a plurality of downhole temperature sensors are employed, spaced apart along the length of the string. For example, further temperature sensors 234a, 234b may be spaced apart along liner 230 to permit determination of the temperature profile therealong. If it is determined that a section of undesirable temperature is developing along the length of the liner 230, one or more of valves 230, 232 and/or 227 may be actuated to affect the heat generated at that point either by adjusting the location of the flame, adjusting the heat of the flame and/or by effecting the evacuation rate of the flue gas.
If the apparatus includes more than one heating zone, the control system may sense conditions in one or more of the plural zones and regulate one or more of the fuel handling areas simultaneously or individually. For example, the regulated flow of the fuel gasses may be isolated to individual heating zones or may occur such that any flow regulation is communicated throughout the apparatus. In one embodiment, condition sensing may occur at various locations along the treatment string so that the regulation of fuel gas, for example oxygen, flow into the plural heating zones may be appropriate for the conditions in each zone. For example, in one embodiment, a temperature sensor may be positioned in each of a plurality of locations along the string and a valve may be provided in each of a plurality of heat zones to increase or decrease the flow of at least one of the fuel gasses to each such zone. As such, a particular temperature, for example, between the upper and lower temperature thresholds may be maintained in each of the plurality of heat zones.
For example, in one embodiment of the present invention the apparatus may have a first heating zone and a second heating zone adjacent to the first heating zone and the first and second heating zones may each be monitored for at least one process condition and combustion in each zone may be independently controlled. For example, the apparatus may be controlled to create a substantially uniform temperature profile across the plurality of heating zones. One heating zone may be controlled separately and perhaps isolated from the other heating zones.
Control system components and processes may vary depending on a number of factors, including familiarity with apparatus function, process conditions, etc. For example, during initial operations, there may be redundancy of temperature sensors and flue gas monitors. However, over time, it may occur that these redundancies are reduced or eliminated.
W S Legal\065151\00002\6340527v1 The apparatus may further include a flue gas injection system. For example, if desired, the flue gas can be recovered, in whole or in part, from conduit 226, and pumped back downhole. In one embodiment, therefore, the apparatus may include a flue gas handling system 240, such as for example, including one or more of a compressor, a pump, etc., to condition the flue gas for injection downhole and to direct the flue gas into a flue gas injection conduit 242. In one embodiment, the flue gas may be mixed with solvents to further facilitate production of oil products. Solvents may be added from a solvent source 244 associated with handling system 240. Suitable solvents may be known to those skilled in the art and include for example propane.
The conduit may extend into a formation of interest. In one embodiment, conduit 242 may be connected to outer liner 230 to access the same formation in which the direct heating is occurring. Conduit 242 may include openings 245 through its walls, such that the recovered flue gas, and possibly entrained solvent, may directly access the formation through those openings.
Injection of flue gas, with or without, solvent may provide for enhanced environmental controls and may facilitate production of the desired products from the subterranean formation.
There may be a plurality of valves 247 along the conduit that regulate the injection of recovered flue gas and possibly solvents by increasing or decreasing the flow into the subterranean formation. In such an embodiment, recovered flue gas and possibly solvents can be injected into a first heating zone without also being released into the second heating zone, it having been decided that production in the second heating zone is not currently of interest or it having been determined that the second heating zone is already of a desired thermal condition.
To install the apparatus, a wellbore must be drilled into the formation of interest. The formation of interest may be an oil-containing formation that would be advantaged by input of thermal energy thereto or a formation adjacent an oil-containing formation that would be advantaged by input of thermal energy thereto. The wellbore may be drilled through, above, below or alongside an oil-containing formation. Generally, the wellbore may extend along a horizontal section.
The apparatus is run into the well and set in place with conduits 214, 218, 226 in fluid communication with surface and any electrical or other communications connected. For example, in one embodiment, outer liner 228 is run into the wellbore and set in place. The outer liner may have its outer surface in communication and possibly in contact with the formation of WS Legal\065151\00002\6340527v 1 interest. While annular treatments, such as gravel packs, cementing, etc. may be accommodated, care might to taken to avoid any disadvantageous reductions in the possible thermal conduction from the liner to the formation. The outer liner may extend entirely to surface or, as shown, be connected into an uphole liner string. In such an embodiment, the outer liner may be connected by any of various liner hanger/packer assemblies 250. Consideration may be given as to the thermal conditions to be withstood downhole and appropriate selections made.
For example, in one embodiment, a metal to metal packer may be employed.
If a flue gas injection conduit is to be provided, that conduit may be run with the liner. For example, the flue gas injection conduit may be connected to the liner, as by strapping, welding, forming integral therewith, etc.
Once the liner is in place, the intermediate and inner tubing strings may be run in to the portion of the liner in which the direct heating is to occur. Generally, the treatment string in which direct heating is to occur extends along a horizontal section of a wellbore, but other configurations can be accommodated.
The conduits thus formed are then connected to a surface wellhead apparatus including inlets, valves, etc.
In one embodiment, a production well 260 may be positioned or existing adjacent to the wellbore in which the apparatus is positioned. The producing well may be directly or offset below the direct heat wellbore or may be above or alongside it. A production well may include various components such as a slotted liner 262, a pump 264 and/or a production string 266 to permit the produced oil to be conducted to surface 215.
A method for heating subterranean formations is provided. The method includes:
igniting a mixture of oxygen and a combustible fluid in a wellbore to combust and produce heat and a flue gas. The heat produced conductively heats the subterranean formation through.
The flue gas is returned to the surface. The thermal energy generated may conductively heat the surrounding subterranean formation to facilitate production of the desired products from the subterranean formation. The generated thermal energy may directly heat oil products and/or may heat other formation fluids to indirectly heat oil products in the formation. For example, the generated W S Legal\06 5151 \00002\6340527v 1 thermal energy may conduct out of the apparatus and generate steam from surrounding formation water, which in turn heats oil products for production thereof.
The flue gas may be maintained out of contact with the formation such that the method does not introduce any foreign fluids to the formation. Thus, the method may avoid any significant change in the pressure of the formation. As such, the method may have a wide range of applications, even in formations close to the surface and/or those with questionable or no cap rock. In one embodiment, for example, the apparatus may be useful at depths of 60 to 120 meters.
In another embodiment, for example, where there are environmental concerns relating to the release of flue gas, the flue gas may be collected at surface and injected downhole. Such injection may include processing of the flue gas at surface, for example, compression and pumping thereof. The injection may be to the formation of interest or to another formation. This may affect the formation pressure.
The formation heating that occurs reduces the viscosity of the oil in the formation and facilitates its production. In one embodiment, the oil is produced through an adjacent producing well. In another embodiment, after heating of the formation, the outer liner can be converted to a producing liner, as by opening ports therethrough (i.e. perforating the liner or opening existing, but previously closed ports) and allowing inflow of oil, which is moved to surface.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from scope of the invention.
Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article "a" or "an" is not intended to mean "one and only one"
unless specifically so stated, but rather "one or more". All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are know or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the WS Legal\065151 \00002\6340527v 1 claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.
W SLegal\065151 \00002\6340527v 1
Claims (10)
1. An apparatus for heating a subterranean formation to facilitate production of oil therefrom, the apparatus comprising:
(a) a downhole ignition area;
(b) a conduit to deliver oxygen, a combustible fluid or a combination thereof, to the down hole ignition area; and (c) a return conduit that recovers flue gas from the down hole ignition area.
(a) a downhole ignition area;
(b) a conduit to deliver oxygen, a combustible fluid or a combination thereof, to the down hole ignition area; and (c) a return conduit that recovers flue gas from the down hole ignition area.
2. The apparatus as in claim 1, wherein the conduits, and ignition area, are positioned in an enclosure such that fluids are maintained from contacting the subterranean formation.
3. The apparatus as in claim 2, wherein a conduit that recovers flue gas directs the flue gas to a compressor.
4. The apparatus as in claim 3, wherein the compressor compresses and pumps the flue gas down a conduit to be injected into the subterranean formation.
5. The apparatus as in claim 3, wherein the flue gas may be mixed with solvents.
6. The apparatus as in claim 1, wherein the heat may be directed, in varying degrees, to create a plurality of thermal zones within the subterranean formation.
7. A method for heating subterranean formations, the method comprising:
(a) employing an apparatus installed in a subterranean formation including:
(i) a down hole ignition area;
(ii) a conduit to deliver oxygen, a combustible fluid or a combination thereof, to the down hole ignition burner head; and (iii) a return conduit that recovers flue gas from the down hole ignition burner head;
(b) igniting a mixture of oxygen and combustible fluid down hole to combust and produce heat and a flue gas;
(c) the heat produced conductively heats the subterranean formation; and (d) the flue gas from the ignition area is returned to the surface.
(a) employing an apparatus installed in a subterranean formation including:
(i) a down hole ignition area;
(ii) a conduit to deliver oxygen, a combustible fluid or a combination thereof, to the down hole ignition burner head; and (iii) a return conduit that recovers flue gas from the down hole ignition burner head;
(b) igniting a mixture of oxygen and combustible fluid down hole to combust and produce heat and a flue gas;
(c) the heat produced conductively heats the subterranean formation; and (d) the flue gas from the ignition area is returned to the surface.
8. The method as in claim 7, wherein the flue gas is compressed and pumped from surface into the subterranean formation.
9. The method as in claim 8, wherein solvents are added to the flue gas.
10. A method for heating a subterranean formation comprising:
(a) igniting a mixture of oxygen and a combustible fluid in a wellbore to combust and produce heat and a flue gas, the heat conductively heating the subterranean formation and the flue gas being returned to a surface location, the mixture of oxygen and combustible fluid and the flue gas being isolated from contact with the subterranean formation.
(a) igniting a mixture of oxygen and a combustible fluid in a wellbore to combust and produce heat and a flue gas, the heat conductively heating the subterranean formation and the flue gas being returned to a surface location, the mixture of oxygen and combustible fluid and the flue gas being isolated from contact with the subterranean formation.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US24910909P | 2009-10-06 | 2009-10-06 | |
| US61/249,109 | 2009-10-06 |
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|---|---|
| CA2716614A1 true CA2716614A1 (en) | 2011-04-06 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2716614 Abandoned CA2716614A1 (en) | 2009-10-06 | 2010-10-05 | Direct fired conductive subterranean heating system |
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| CA (1) | CA2716614A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10273790B2 (en) | 2014-01-14 | 2019-04-30 | Precision Combustion, Inc. | System and method of producing oil |
-
2010
- 2010-10-05 CA CA 2716614 patent/CA2716614A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10273790B2 (en) | 2014-01-14 | 2019-04-30 | Precision Combustion, Inc. | System and method of producing oil |
| US10557336B2 (en) | 2014-01-14 | 2020-02-11 | Precision Combustion, Inc. | System and method of producing oil |
| US10760394B2 (en) | 2014-01-14 | 2020-09-01 | Precision Combustion, Inc. | System and method of producing oil |
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