CA1286217C - Completion procedure for pads subjected to thermal steam stimulation - Google Patents
Completion procedure for pads subjected to thermal steam stimulationInfo
- Publication number
- CA1286217C CA1286217C CA000534514A CA534514A CA1286217C CA 1286217 C CA1286217 C CA 1286217C CA 000534514 A CA000534514 A CA 000534514A CA 534514 A CA534514 A CA 534514A CA 1286217 C CA1286217 C CA 1286217C
- Authority
- CA
- Canada
- Prior art keywords
- wells
- reservoir
- level
- fluid
- injection
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP 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. optimizing the spacing of wells
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP 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
- E21B43/17—Interconnecting two or more wells by fracturing or otherwise attacking the formation
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP 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
- E21B43/2405—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection in association with fracturing or crevice forming processes
Abstract
ABSTRACT OF THE DISCLOSURE
A method for the production of bitumens from a subterranean reservoir which is penetrated by a plurality of spaced apart wells. In particular, horizontal fractures are formed in the reservoir by injecting high-pressure fluid through the wells. The levels at which the fluid is injected into the reservoir are spaced apart vertically so that a horizontal fracture formed from a first well does not intersect a horizontal fracture formed from a second well. By using this method, well-to-well communication of the fluid along the horizontal fracturing is prevented and the mobilizing effects of the fluid are more uniformly distributed through the reservoir, improving the efficiency of bitumens production from the wells.
A method for the production of bitumens from a subterranean reservoir which is penetrated by a plurality of spaced apart wells. In particular, horizontal fractures are formed in the reservoir by injecting high-pressure fluid through the wells. The levels at which the fluid is injected into the reservoir are spaced apart vertically so that a horizontal fracture formed from a first well does not intersect a horizontal fracture formed from a second well. By using this method, well-to-well communication of the fluid along the horizontal fracturing is prevented and the mobilizing effects of the fluid are more uniformly distributed through the reservoir, improving the efficiency of bitumens production from the wells.
Description
COMPLETION PROCEDURE FOR PADS SUBJECTED
TO THERMAL STFAM STIMULATI ON
Field of the Invention The invention relates generally to the production of hydrocarbons from subterranean reservoirs. This invention relates more particularly to the production of bitumens from underground tar sand beds.
Back~round of the Invention Throughout the world there exist numerous subterranean tar sand formations containing high-density, high-viscosity bitumens which resist recovery by conventional means. The vast Athabasca tar sand field in Alberta Province, Canada represents one of the most notable examples of such formations. The Cold Lake deposits in the same province represent a similar formation.
A variety of methods have been proposed for improving the production of hydrocarbons from these formations by increasing their mobility, including both solvent injection and thermal steam stimulation processes. One currently utilized method is the so-called "huff-and-puff" process. In this method, a well is sunk into the bitumen-bearing formation and completed at a given depth, usually by perforation, so as to establish fluid communication between the well and the 6Z~7 formation. Steam is injected through the producing well into the formation to mobili~e the bitumens. Steam injection is then terminated and, often following some shut-in period, hydrocarbon containing fluids are produced from the same well. In a representative process, steam is injected at high pressures (approximately 10 MPa) into a well for approximately six weeks, until about 10,000 m3 water equivalent steam has been injected. The steam injection pressure applied exceeds the fracture pressure of the formation in order to achieve the required injectivity. The injection of steam is then terminated and the well ls produced for a period of three months or more.
Typical practice is to complete "huff-and-puff" wells at depths determined more or less individually on the basis of geological considerations for that portion of the tar sand bed which they penetrate. ~ence, if the geological considerations indicate that an individual "huff-and-puff" well can most effectively drain a reservoir if completed at a certain true vertical depth (typically somewhere near the lower oil horizon), then each such "huff-and-puff" well penetrating that area of the bed is completed at that same true vertical depth.
Recent study of reservoir behavior during huff-and-puff operations by Applicants indicates that several material disadvantages inhere in the typical completion procedure when applied to tar sand beds of the Athabasca or Cold Lake type.
Applicants studied a cluster or "pad" of "huff-and-puff" wells - ' ~X~62~
which, consistent with the practice described above, had all been completed at about the same true vertical depth in order to drain a portion of an Athabasca- or Cold Lake- type tar sand bed. Through the use of a number of observation wells associated with this particular pad, Applicants obtained data strongly indicative of well-to-well communication over considerable distances via horizontal fractures at the nominal completion depth of the huff-and-puff wells. As summarized in FIGURE 5, significant temperature increases were noted throughout the pad in each of the observation wells at the nominal completion depth of 455 meters. Furthermore, measurements indicated that the minimum horizontal in situ stress exceeded the overburden stress at each of the production wells and positive wellhead pressures were observed on each of the unsteamed wells.
Such well-to-well communication via horizontal fracturing is disadvantageous in that it results in poor vertical conformance in the tar sand bed. That is, the thermal and other mobilizing effects of the steam stimulation process are not evenly distributed through the formation, resulting in reduced thermal efficiency and a lower recovery factor per well, which further results in the need for additional wells to effectively drain a given area of tar sand bed.
Accordingly, prior to the present invention, there was believed to be no huff-and-puff method for production of bitumen from a subterranean tar sand bed which achieved an improved vertical sweep efficiency by preventing well-to-well communication via horiæontal fracturing.
~z~
Summarv of the Invention The present invention concerns a method for recovering bitumens from a subterranean reservoir penetrated by more than one production well, comprising the steps of establishing fluid communication between a first well and said reservoir at at least one level in said reservoir, establishing fluid communication between a second we].l and said reserYoir at at least one other level in said reservoir, said at least one other level being arranged so as to be a vertically spaced distance from every level at which fluid communication is established in said first well, whereby the intersection of horizontal fractures between said wells at said at least one other level is prevented, injecting fluid via each of said wells into said reservoir at a pressure exceeding the fracture pressure of said reservoir, terminating the injection of fluid into at least onè
of said wells, and recovering bitumen-containing fluids from said reservoir via said at least one of said wells.
Another feature of the present invention is that method in which the steps of injectlng fluid into and recovering bitumen from the tar sand bed via each of said wells is repeated cyclically.
Another feature of this invention is that the method may include the subsequent steps of: terminating the injection of fluid into the formation via at least one well which is in fluid communication with the reservoir at a level below the ~ 2~ 7 median level of communication for those wells in communication with the local area of said reservoir, and producing bitumen from the tar sand bed via those wells through which fluid injection has been terminated.
Yet another feature of this invention is that the method may include producing bitumen from the tar sand bed via those wells through which fluid injection has been terminated while continuously injecting fluid into the tar sand bed via those wells through which fluid injection has not been terminated.
`~ The method of the present invention for producing bitumens from a subterranean tar sand bed has the advantages of increasing the vertical sweep efficiency by preventing adverse well-to-well communication via horizontal fractures.
Brief Description of the Drawin~s FIGS. 1-4 are partial, cross-sectional views of a formation having a reservoir containing high-density, high-viscosity bitumens wherein the sequential method steps in accordance with the present invention are illustrated.
FIG. 5 illustrates vertical temperature distributions observed in observation wells associated with a pad of huff-and-puff wells. The horizontal distances between the observation wells and the nearest steamed huff-and-puff wells are listed in the upper right corner.
-` ~2~
These drawings are not intended as a definition of the invention, but are provided solely for the purpose of illustrating certain preferred embodiments of the invention, as described below.
Detailed Descri~tion of the Invention FIGS. 1-4 illustrate the sequential steps in practicing the method of the present invention for the recovery of high-density, high-viscosity bitumens. As used in this application, the term bitumens is used to mean any heavy, viscous hydrocarbon.
With reference to FIG. l, terrain, or field, 10 is shown to include overburden 12 lying over reservolr 14 containing high-density, high-viscosity bitumen. Reservoir 14 is underlain by stratum 16. Field 10 is provided with injection-production wells 18, 20, and 22 in a conventional manner, which extend from the surface of terrain 10 downwardly into reservoir 14. Three injection-production wells are shown, however, it should be understood that the method of the present lnvention is applicable to use with as few as two injection-production wells, as well as with any other number of injection-production wells disposed in any suitable pattern or configuration.
12~36~
Still with reference to FIG. l, it is seen that wells 18, 20J and 22 are provided with a conventional casingB 24~ 26 and 28 which are cemented in a conventional marmer which prevents the flow of steam along the axis of the wells between the well casings 24~ 26~ and 28 and the well bores (not shown).
With further reference to FIG. 1, the next steps of the present invention will be described. After wells 18J 20, and 22 have been provided, each well casing 24~ 26~ and 28 is perforated in a conventional maTmer to provide it with a plurality of holes or perforations 30J 32~ aT1d 34J which establish fluid communication between each well 18, 20J and 22 and reservoir 14. It should be noted that although fluid communication is here shown as being established by conventional perforation, such communication could be established by any suitable method of forming an opening through the well casing and surrounding cement. Each depth at which each well is perforated is vertically offset from every depth at which each other well is perforated. As used in this application, depth, level, and horizontal refer to relative positions or elevations in the reservoir itself, which may or may not correspond to the absolute elevation of the positions. Although wells 18, 20, and 22 are shown with only one perforated interval each, it should be noted that each well could be provided with any number of perforation levels, so long as each such level is vertically offset from each level of perforation in the other wells.
Perforations 30, 32~ and 34 are offset by a sufficient vertical distance to prevent the intersection of any horizontal fractures ~l~ 962~L7 emanating therefrom. A further consideration in determining the vertical offset distance is the optimum vertical spacing of the "huff-and-puff" recovery zones for the subject bitumens.
Techniques for determining such spacing, including reservoir modeling, are kno~m to those skilled in the art. Data derived from the workover of existing "huff-and-puff" wells indicates that the spacing for Cold Lake-type tar sands may be 10 to 20 meters.
After wells 18, 20, and 22 have been provided with perforations 30, 32, and 34 as described, high-pressure fluid (that is, fluid at or above fracturing pressure for reservoir 14) is injected into each injection-production well 18, 20, and 22. The high-pressure fluid travels in the directions showm by arrows 36, passes through perforations 30, 32, and 34 formed in casings 24, 26, and 28 and forms fractures 38, 40, and 42 as it enters the formation. Fractures 38, 40 and 42 are each substantially horzontal and are each vertically offset from the others so that they do not intersect and so that there is no communication via the fractures between wells 18, 20, and 22.
It should be understood that, while it is an object of the present invention to isolate injection fractures from one another, in some embodiments it may still be desirable to have one or more fractured intervals common to several wells: for example, a gravity drainage fracture at the bottom of the reservoir with which each well communicates.
21~
g The injected fluid is usually steam. Consequently, the terms "fluid" and "steam" will hereinafter be used interchangeably. As the steam passes into fractures 38, 40, and 42, heat and fluids pass into reservoir 14, mobilizing the high-density, high-viscosity bitwnen, in the directions shown by small arrows 44.
After a selected quantit~y of high-pressure steam has been injected into each o the injection-production wells 18, 20, and 22, the injection of steam is terminated. Thereafter, as shown in FIG. 2, bitwmen-containing fluids are produced from each of the wells. The bitwmens in reservoir 14 are mobilized in the directions shown by small arrows 46. Bitwmen-containing fluids, as shown by arrows 48, pass along ~he fractures 38, 40, and 42 and through perforations 30, 32, and 34 in well casings 24, 26, and 28 into wells 18, 20, and 22 for production at the surface of field 10 in a conventional manner. After the termination of the injection of steam into injection-production wells 18, 20, and 22 and prior to the production of bitwmen thereform, the injection-production wells may be shut-in, whereby for a time no fluids and/or bitwmens flow outwardly from the injection-production wells.
The injection and production steps illustrated in FIG. 1 and FIG. 2, respectively, may be repeated cyclically, as in the "huff-and-puff" technique described above, in order to optimize the recovery of bitumens as mobilization of the reservoir increases. After a time, the reservoir may be heated ~2~
~10--to the point where the bitumen viscosity drops enough to permit the general downward migration of bitumens to lower levels in the reservoir due to gravity drainage. Consequently, at some point it may become advantageous to cease the injection of steam into those wells which are in communication with the lower levels of the reservoir. Such wells can then be operated more or less continuously as production wells while cyclical injection and production continues in those wells in communication with the reservoir at higher levels. With reference to FIG. 3, this next step of the invention will be described. Injection of steam into injection-production well 22, which is in communication with reservoir 14 at the lowest level of the three wells illustrated, is terminated. Cyclical injection of steam and production of bltumen continues in injection-production wells 18 and 20 as described in the preceding steps, with steam and bitumen-containing fluids moving alternately into and out of wells 18 and 20, through perforations 30 and 32, and along fractures 38 and 40 in the directions shown by arrows 50. Bitumens in reservoir 14 are mobilized alternately in the directions shown by small arrows 52. A certain amount of mobilized bitumen-containing fluids migrate downward through reservoir 14 in the direction shown by arrows 54 and collect in sump 56, through which mobility has been increased by heating and attendant viscosity reduction, along with partial depletion of bitumens from the reservoir by preceding injection and production from well 22.
Bitumen-containing fluids then move along fracture 42 in the direction shown by arrows 58, through perforations 34 and into well 22, from which they are produced in a conventional manner.
12~
Further, after additional depletion of bitumens from the reservoir through repeated application of the steps described above, it may prove advantageous to operate the system so that the wells completed at deeper levels in the reservoir are permanent producers and the remaining wells are continuous injectors, using gravity drainage and/or steam drive to mobilize remaining bitumens to the produc:lng wells. With reference to FIG. 4, this next step of the present invention will be described. Following the final productlon cycle using injection-production wells 18 and 20, production of bitumens from wells 18 and 20 is terminated and steam is substantially continuously injected into injection-production wells 18 and 20. The steam travels out through perforations 30 and 32 and along fractures 38 and 40 in the direction shown by arrows 60, and out into partially depleted reservoir 14 in the direction shown by arrows 62. A steam condensate~bitumen interface is shown by boundary 64, which progresses downward in the direction shown by small arrows 66 as mobilized bitumens, shown by arrows 68, move towards lower areas of reservoir 14, due to gravity drainage or steam drive. Bitumen-containing fluids, as shown by arrows 70, move along fracture 42, through perforations 34 and into well 22, from which they are produced by a conventional manner. Techniques for determining optimum steam injection rates to maximize bitumen recovery and to minimize fingering of the condensate/bitumen boundary in steam drive recovery systems are known to those skilled in the art.
:
~Z~3~;2~
It is to be understood that the invention is not limited to the exact details of construction or operation, exact materials, or exact embodiment shown and described, as obvious modiFications and equivalents will be apparent to one skilled in the art. ~or example, another hi~h pressure fluid, other than steam, could be utilized. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.
TO THERMAL STFAM STIMULATI ON
Field of the Invention The invention relates generally to the production of hydrocarbons from subterranean reservoirs. This invention relates more particularly to the production of bitumens from underground tar sand beds.
Back~round of the Invention Throughout the world there exist numerous subterranean tar sand formations containing high-density, high-viscosity bitumens which resist recovery by conventional means. The vast Athabasca tar sand field in Alberta Province, Canada represents one of the most notable examples of such formations. The Cold Lake deposits in the same province represent a similar formation.
A variety of methods have been proposed for improving the production of hydrocarbons from these formations by increasing their mobility, including both solvent injection and thermal steam stimulation processes. One currently utilized method is the so-called "huff-and-puff" process. In this method, a well is sunk into the bitumen-bearing formation and completed at a given depth, usually by perforation, so as to establish fluid communication between the well and the 6Z~7 formation. Steam is injected through the producing well into the formation to mobili~e the bitumens. Steam injection is then terminated and, often following some shut-in period, hydrocarbon containing fluids are produced from the same well. In a representative process, steam is injected at high pressures (approximately 10 MPa) into a well for approximately six weeks, until about 10,000 m3 water equivalent steam has been injected. The steam injection pressure applied exceeds the fracture pressure of the formation in order to achieve the required injectivity. The injection of steam is then terminated and the well ls produced for a period of three months or more.
Typical practice is to complete "huff-and-puff" wells at depths determined more or less individually on the basis of geological considerations for that portion of the tar sand bed which they penetrate. ~ence, if the geological considerations indicate that an individual "huff-and-puff" well can most effectively drain a reservoir if completed at a certain true vertical depth (typically somewhere near the lower oil horizon), then each such "huff-and-puff" well penetrating that area of the bed is completed at that same true vertical depth.
Recent study of reservoir behavior during huff-and-puff operations by Applicants indicates that several material disadvantages inhere in the typical completion procedure when applied to tar sand beds of the Athabasca or Cold Lake type.
Applicants studied a cluster or "pad" of "huff-and-puff" wells - ' ~X~62~
which, consistent with the practice described above, had all been completed at about the same true vertical depth in order to drain a portion of an Athabasca- or Cold Lake- type tar sand bed. Through the use of a number of observation wells associated with this particular pad, Applicants obtained data strongly indicative of well-to-well communication over considerable distances via horizontal fractures at the nominal completion depth of the huff-and-puff wells. As summarized in FIGURE 5, significant temperature increases were noted throughout the pad in each of the observation wells at the nominal completion depth of 455 meters. Furthermore, measurements indicated that the minimum horizontal in situ stress exceeded the overburden stress at each of the production wells and positive wellhead pressures were observed on each of the unsteamed wells.
Such well-to-well communication via horizontal fracturing is disadvantageous in that it results in poor vertical conformance in the tar sand bed. That is, the thermal and other mobilizing effects of the steam stimulation process are not evenly distributed through the formation, resulting in reduced thermal efficiency and a lower recovery factor per well, which further results in the need for additional wells to effectively drain a given area of tar sand bed.
Accordingly, prior to the present invention, there was believed to be no huff-and-puff method for production of bitumen from a subterranean tar sand bed which achieved an improved vertical sweep efficiency by preventing well-to-well communication via horiæontal fracturing.
~z~
Summarv of the Invention The present invention concerns a method for recovering bitumens from a subterranean reservoir penetrated by more than one production well, comprising the steps of establishing fluid communication between a first well and said reservoir at at least one level in said reservoir, establishing fluid communication between a second we].l and said reserYoir at at least one other level in said reservoir, said at least one other level being arranged so as to be a vertically spaced distance from every level at which fluid communication is established in said first well, whereby the intersection of horizontal fractures between said wells at said at least one other level is prevented, injecting fluid via each of said wells into said reservoir at a pressure exceeding the fracture pressure of said reservoir, terminating the injection of fluid into at least onè
of said wells, and recovering bitumen-containing fluids from said reservoir via said at least one of said wells.
Another feature of the present invention is that method in which the steps of injectlng fluid into and recovering bitumen from the tar sand bed via each of said wells is repeated cyclically.
Another feature of this invention is that the method may include the subsequent steps of: terminating the injection of fluid into the formation via at least one well which is in fluid communication with the reservoir at a level below the ~ 2~ 7 median level of communication for those wells in communication with the local area of said reservoir, and producing bitumen from the tar sand bed via those wells through which fluid injection has been terminated.
Yet another feature of this invention is that the method may include producing bitumen from the tar sand bed via those wells through which fluid injection has been terminated while continuously injecting fluid into the tar sand bed via those wells through which fluid injection has not been terminated.
`~ The method of the present invention for producing bitumens from a subterranean tar sand bed has the advantages of increasing the vertical sweep efficiency by preventing adverse well-to-well communication via horizontal fractures.
Brief Description of the Drawin~s FIGS. 1-4 are partial, cross-sectional views of a formation having a reservoir containing high-density, high-viscosity bitumens wherein the sequential method steps in accordance with the present invention are illustrated.
FIG. 5 illustrates vertical temperature distributions observed in observation wells associated with a pad of huff-and-puff wells. The horizontal distances between the observation wells and the nearest steamed huff-and-puff wells are listed in the upper right corner.
-` ~2~
These drawings are not intended as a definition of the invention, but are provided solely for the purpose of illustrating certain preferred embodiments of the invention, as described below.
Detailed Descri~tion of the Invention FIGS. 1-4 illustrate the sequential steps in practicing the method of the present invention for the recovery of high-density, high-viscosity bitumens. As used in this application, the term bitumens is used to mean any heavy, viscous hydrocarbon.
With reference to FIG. l, terrain, or field, 10 is shown to include overburden 12 lying over reservolr 14 containing high-density, high-viscosity bitumen. Reservoir 14 is underlain by stratum 16. Field 10 is provided with injection-production wells 18, 20, and 22 in a conventional manner, which extend from the surface of terrain 10 downwardly into reservoir 14. Three injection-production wells are shown, however, it should be understood that the method of the present lnvention is applicable to use with as few as two injection-production wells, as well as with any other number of injection-production wells disposed in any suitable pattern or configuration.
12~36~
Still with reference to FIG. l, it is seen that wells 18, 20J and 22 are provided with a conventional casingB 24~ 26 and 28 which are cemented in a conventional marmer which prevents the flow of steam along the axis of the wells between the well casings 24~ 26~ and 28 and the well bores (not shown).
With further reference to FIG. 1, the next steps of the present invention will be described. After wells 18J 20, and 22 have been provided, each well casing 24~ 26~ and 28 is perforated in a conventional maTmer to provide it with a plurality of holes or perforations 30J 32~ aT1d 34J which establish fluid communication between each well 18, 20J and 22 and reservoir 14. It should be noted that although fluid communication is here shown as being established by conventional perforation, such communication could be established by any suitable method of forming an opening through the well casing and surrounding cement. Each depth at which each well is perforated is vertically offset from every depth at which each other well is perforated. As used in this application, depth, level, and horizontal refer to relative positions or elevations in the reservoir itself, which may or may not correspond to the absolute elevation of the positions. Although wells 18, 20, and 22 are shown with only one perforated interval each, it should be noted that each well could be provided with any number of perforation levels, so long as each such level is vertically offset from each level of perforation in the other wells.
Perforations 30, 32~ and 34 are offset by a sufficient vertical distance to prevent the intersection of any horizontal fractures ~l~ 962~L7 emanating therefrom. A further consideration in determining the vertical offset distance is the optimum vertical spacing of the "huff-and-puff" recovery zones for the subject bitumens.
Techniques for determining such spacing, including reservoir modeling, are kno~m to those skilled in the art. Data derived from the workover of existing "huff-and-puff" wells indicates that the spacing for Cold Lake-type tar sands may be 10 to 20 meters.
After wells 18, 20, and 22 have been provided with perforations 30, 32, and 34 as described, high-pressure fluid (that is, fluid at or above fracturing pressure for reservoir 14) is injected into each injection-production well 18, 20, and 22. The high-pressure fluid travels in the directions showm by arrows 36, passes through perforations 30, 32, and 34 formed in casings 24, 26, and 28 and forms fractures 38, 40, and 42 as it enters the formation. Fractures 38, 40 and 42 are each substantially horzontal and are each vertically offset from the others so that they do not intersect and so that there is no communication via the fractures between wells 18, 20, and 22.
It should be understood that, while it is an object of the present invention to isolate injection fractures from one another, in some embodiments it may still be desirable to have one or more fractured intervals common to several wells: for example, a gravity drainage fracture at the bottom of the reservoir with which each well communicates.
21~
g The injected fluid is usually steam. Consequently, the terms "fluid" and "steam" will hereinafter be used interchangeably. As the steam passes into fractures 38, 40, and 42, heat and fluids pass into reservoir 14, mobilizing the high-density, high-viscosity bitwnen, in the directions shown by small arrows 44.
After a selected quantit~y of high-pressure steam has been injected into each o the injection-production wells 18, 20, and 22, the injection of steam is terminated. Thereafter, as shown in FIG. 2, bitwmen-containing fluids are produced from each of the wells. The bitwmens in reservoir 14 are mobilized in the directions shown by small arrows 46. Bitwmen-containing fluids, as shown by arrows 48, pass along ~he fractures 38, 40, and 42 and through perforations 30, 32, and 34 in well casings 24, 26, and 28 into wells 18, 20, and 22 for production at the surface of field 10 in a conventional manner. After the termination of the injection of steam into injection-production wells 18, 20, and 22 and prior to the production of bitwmen thereform, the injection-production wells may be shut-in, whereby for a time no fluids and/or bitwmens flow outwardly from the injection-production wells.
The injection and production steps illustrated in FIG. 1 and FIG. 2, respectively, may be repeated cyclically, as in the "huff-and-puff" technique described above, in order to optimize the recovery of bitumens as mobilization of the reservoir increases. After a time, the reservoir may be heated ~2~
~10--to the point where the bitumen viscosity drops enough to permit the general downward migration of bitumens to lower levels in the reservoir due to gravity drainage. Consequently, at some point it may become advantageous to cease the injection of steam into those wells which are in communication with the lower levels of the reservoir. Such wells can then be operated more or less continuously as production wells while cyclical injection and production continues in those wells in communication with the reservoir at higher levels. With reference to FIG. 3, this next step of the invention will be described. Injection of steam into injection-production well 22, which is in communication with reservoir 14 at the lowest level of the three wells illustrated, is terminated. Cyclical injection of steam and production of bltumen continues in injection-production wells 18 and 20 as described in the preceding steps, with steam and bitumen-containing fluids moving alternately into and out of wells 18 and 20, through perforations 30 and 32, and along fractures 38 and 40 in the directions shown by arrows 50. Bitumens in reservoir 14 are mobilized alternately in the directions shown by small arrows 52. A certain amount of mobilized bitumen-containing fluids migrate downward through reservoir 14 in the direction shown by arrows 54 and collect in sump 56, through which mobility has been increased by heating and attendant viscosity reduction, along with partial depletion of bitumens from the reservoir by preceding injection and production from well 22.
Bitumen-containing fluids then move along fracture 42 in the direction shown by arrows 58, through perforations 34 and into well 22, from which they are produced in a conventional manner.
12~
Further, after additional depletion of bitumens from the reservoir through repeated application of the steps described above, it may prove advantageous to operate the system so that the wells completed at deeper levels in the reservoir are permanent producers and the remaining wells are continuous injectors, using gravity drainage and/or steam drive to mobilize remaining bitumens to the produc:lng wells. With reference to FIG. 4, this next step of the present invention will be described. Following the final productlon cycle using injection-production wells 18 and 20, production of bitumens from wells 18 and 20 is terminated and steam is substantially continuously injected into injection-production wells 18 and 20. The steam travels out through perforations 30 and 32 and along fractures 38 and 40 in the direction shown by arrows 60, and out into partially depleted reservoir 14 in the direction shown by arrows 62. A steam condensate~bitumen interface is shown by boundary 64, which progresses downward in the direction shown by small arrows 66 as mobilized bitumens, shown by arrows 68, move towards lower areas of reservoir 14, due to gravity drainage or steam drive. Bitumen-containing fluids, as shown by arrows 70, move along fracture 42, through perforations 34 and into well 22, from which they are produced by a conventional manner. Techniques for determining optimum steam injection rates to maximize bitumen recovery and to minimize fingering of the condensate/bitumen boundary in steam drive recovery systems are known to those skilled in the art.
:
~Z~3~;2~
It is to be understood that the invention is not limited to the exact details of construction or operation, exact materials, or exact embodiment shown and described, as obvious modiFications and equivalents will be apparent to one skilled in the art. ~or example, another hi~h pressure fluid, other than steam, could be utilized. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.
Claims (16)
1. A method for the production of bitumens from a subterranean reservoir which is penetrated by a plurality of spaced apart wells, said method comprising the steps of:
forming substantially horizontal fractures extending from a first well into said formation at at least one level in said reservoir;
forming substantially horizontal fractures extending from a second well into said formation at at least one other level in said reservoir, said at least one other level being arranged so as to be a vertically spaced distance from every level at which horizontal fractures were formed from said first well, whereby the intersection of horizontal fractures between said first and second wells at said at least one other level is prevented;
injecting fluid via each of said wells into said horizontal fractures; and recovering bitumen-containing fluids from each of said wells.
forming substantially horizontal fractures extending from a first well into said formation at at least one level in said reservoir;
forming substantially horizontal fractures extending from a second well into said formation at at least one other level in said reservoir, said at least one other level being arranged so as to be a vertically spaced distance from every level at which horizontal fractures were formed from said first well, whereby the intersection of horizontal fractures between said first and second wells at said at least one other level is prevented;
injecting fluid via each of said wells into said horizontal fractures; and recovering bitumen-containing fluids from each of said wells.
2. The method of claim 1 wherein said fluid is steam.
3. The method of claim 1 wherein the fluid injection and recovery steps are repeated cyclically.
4. The method described in claim 3, further comprising:
terminating the injection of fluid into at least one of said wells from which is formed horizontal fractures at at least one level which is below the median level of the horizontal fractures extending into the local area of said reservoir; and producing bitumen-containing fluids from said reservoir via said at least one well to which fluid injection has been terminated.
terminating the injection of fluid into at least one of said wells from which is formed horizontal fractures at at least one level which is below the median level of the horizontal fractures extending into the local area of said reservoir; and producing bitumen-containing fluids from said reservoir via said at least one well to which fluid injection has been terminated.
5. The method described in claim 4, further comprising: continuously injecting fluid into those horizontal fractures extending into said reservoir from those wells to which fluid injection has not been terminated.
6. A method for the production of bitumens from a subterranean reservoir which is penetrated by a plurality of spaced apart wells, said method comprising the steps of:
establishing fluid communication between a first well and said reservoir at at least one level in said reservoir;
establishing fluid communication between a second well and said reservoir at at least one other level in said reservoir, said at least one other level being arranged so as to be a vertically spaced distance from every level at which fluid communication is established in said first well, whereby the intersection of horizontal fractures between said wells at said at least one other level is prevented;
injecting fluid into said first reservoir level through said first well and into said other reservoir level through said second well at a pressure exceeding the fracture pressure of said reservoir;
terminating the injection of fluid into at least one of said wells; and recovering bitumen-containing fluids from said reservoir via said at least one of said wells.
establishing fluid communication between a first well and said reservoir at at least one level in said reservoir;
establishing fluid communication between a second well and said reservoir at at least one other level in said reservoir, said at least one other level being arranged so as to be a vertically spaced distance from every level at which fluid communication is established in said first well, whereby the intersection of horizontal fractures between said wells at said at least one other level is prevented;
injecting fluid into said first reservoir level through said first well and into said other reservoir level through said second well at a pressure exceeding the fracture pressure of said reservoir;
terminating the injection of fluid into at least one of said wells; and recovering bitumen-containing fluids from said reservoir via said at least one of said wells.
7. The method of claim 6 wherein said fluid is steam.
8. The method described in claim 6, further comprising: shutting in said at least one of said wells for a predetermined period of time following the termination of the injection of fluid into said reservoir and prior to the recovery of said bitumen-containing fluid from said reservoir.
9. The method described in claim 7 wherein the fluid injection and recovery steps are repeated cyclically.
10. The method described in claim 9, further comprising:
terminating the injection of fluid into at least one of said wells which is in fluid communication with said reservoir at a level below the median level of communication for those wells in fluid communication with the local area of said reservoir; and producing bitumen-containing fluids from said reservoir via said wells to which fluid injection has been terminated.
terminating the injection of fluid into at least one of said wells which is in fluid communication with said reservoir at a level below the median level of communication for those wells in fluid communication with the local area of said reservoir; and producing bitumen-containing fluids from said reservoir via said wells to which fluid injection has been terminated.
11. The method described in claim 10, further comprising:
continuously injecting fluid into said reservoir via those wells to which fluid injection has not been terminated.
continuously injecting fluid into said reservoir via those wells to which fluid injection has not been terminated.
12. A method for the production of bitumens from a subterranean tar sand bed which is penetrated by a plurality of spaced apart wells, said method comprising the steps of:
perforating a first well at at least one level in said tar sand bed;
perforating a second well at at least one other level in said tar sand bed, said at least one other level being positioned a vertical spaced distance from every level at which said first well is perforated, whereby the intersection of horizontal fractures between said wells at said at least one other level is prevented;
injecting steam via each of said wells into said tar sand bed at a pressure exceeding the fracture pressure of said tar sand bed;
terminating the injection of steam into each of said wells; and recovering bitumen-containing fluids from said tar sand bed via each of said wells.
perforating a first well at at least one level in said tar sand bed;
perforating a second well at at least one other level in said tar sand bed, said at least one other level being positioned a vertical spaced distance from every level at which said first well is perforated, whereby the intersection of horizontal fractures between said wells at said at least one other level is prevented;
injecting steam via each of said wells into said tar sand bed at a pressure exceeding the fracture pressure of said tar sand bed;
terminating the injection of steam into each of said wells; and recovering bitumen-containing fluids from said tar sand bed via each of said wells.
13. The method described in claim 12, further comprising:
shutting in each of said wells for a predetermined period of time following the termination of the injection of steam into said tar sand bed and prior to the recovery of said bitumen-containing fluids from said tar sand bed
shutting in each of said wells for a predetermined period of time following the termination of the injection of steam into said tar sand bed and prior to the recovery of said bitumen-containing fluids from said tar sand bed
14. The method described in claim 13 wherein the fluid injection, shut-in, and recovery steps are repeated cyclically.
15. The method described in claim 14, further comprising:
terminating the injection of steam into said tar sand bed via at least one of said wells which is perforated at a level below the median level of perforation for those wells penetrating the local area of said tar sand bed; and producing bitumen-containing fluids from said tar sand bed via said wells through which steam injection has been terminated.
terminating the injection of steam into said tar sand bed via at least one of said wells which is perforated at a level below the median level of perforation for those wells penetrating the local area of said tar sand bed; and producing bitumen-containing fluids from said tar sand bed via said wells through which steam injection has been terminated.
16. The method described in claim 15, further comprising:
continuously injecting steam into said tar sand bed via those wells through which steam injection has not been terminated.
continuously injecting steam into said tar sand bed via those wells through which steam injection has not been terminated.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000534514A CA1286217C (en) | 1987-04-13 | 1987-04-13 | Completion procedure for pads subjected to thermal steam stimulation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000534514A CA1286217C (en) | 1987-04-13 | 1987-04-13 | Completion procedure for pads subjected to thermal steam stimulation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1286217C true CA1286217C (en) | 1991-07-16 |
Family
ID=4135414
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000534514A Expired - Lifetime CA1286217C (en) | 1987-04-13 | 1987-04-13 | Completion procedure for pads subjected to thermal steam stimulation |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1286217C (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10012064B2 (en) | 2015-04-09 | 2018-07-03 | Highlands Natural Resources, Plc | Gas diverter for well and reservoir stimulation |
| US10344204B2 (en) | 2015-04-09 | 2019-07-09 | Diversion Technologies, LLC | Gas diverter for well and reservoir stimulation |
| US10982520B2 (en) | 2016-04-27 | 2021-04-20 | Highland Natural Resources, PLC | Gas diverter for well and reservoir stimulation |
-
1987
- 1987-04-13 CA CA000534514A patent/CA1286217C/en not_active Expired - Lifetime
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10012064B2 (en) | 2015-04-09 | 2018-07-03 | Highlands Natural Resources, Plc | Gas diverter for well and reservoir stimulation |
| US10344204B2 (en) | 2015-04-09 | 2019-07-09 | Diversion Technologies, LLC | Gas diverter for well and reservoir stimulation |
| US10385258B2 (en) | 2015-04-09 | 2019-08-20 | Highlands Natural Resources, Plc | Gas diverter for well and reservoir stimulation |
| US10385257B2 (en) | 2015-04-09 | 2019-08-20 | Highands Natural Resources, PLC | Gas diverter for well and reservoir stimulation |
| US10982520B2 (en) | 2016-04-27 | 2021-04-20 | Highland Natural Resources, PLC | Gas diverter for well and reservoir stimulation |
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