CA1289057C - Method for achieving communication between injection and production wells in tar sand deposits - Google Patents
Method for achieving communication between injection and production wells in tar sand depositsInfo
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- CA1289057C CA1289057C CA000533056A CA533056A CA1289057C CA 1289057 C CA1289057 C CA 1289057C CA 000533056 A CA000533056 A CA 000533056A CA 533056 A CA533056 A CA 533056A CA 1289057 C CA1289057 C CA 1289057C
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Abstract
Abstract of the Disclosure A method for achieving communication between an injection well and a production well in tar sand deposits. A
cavity is excavated at a point where the injection well is proximate to the production well. A fluid is injected in the production well at a pressure less than fracture pressure to cause the subterranean formation intermediate the production well and the cavity to collapse and create a highly permeable zone of unconsolidated tar sands, thus forming a communication path between the production well and the injection well. In a preferred embodiment of the invention several injection vertical wells are used in combination with one associated horizontal production well. In this embodiment, a hydraulically balanced system may be established by selectively shutting-in the injection wells while maintaining fluid pressure in the production well. After the communication paths are created, field production operations may begin. Steam and other fluid may be injected in the injection wells to encourage gravity drainage of bitumen toward the production well. Bitumen is produced to the surface through the production well via any number of known artificial lift methods.
cavity is excavated at a point where the injection well is proximate to the production well. A fluid is injected in the production well at a pressure less than fracture pressure to cause the subterranean formation intermediate the production well and the cavity to collapse and create a highly permeable zone of unconsolidated tar sands, thus forming a communication path between the production well and the injection well. In a preferred embodiment of the invention several injection vertical wells are used in combination with one associated horizontal production well. In this embodiment, a hydraulically balanced system may be established by selectively shutting-in the injection wells while maintaining fluid pressure in the production well. After the communication paths are created, field production operations may begin. Steam and other fluid may be injected in the injection wells to encourage gravity drainage of bitumen toward the production well. Bitumen is produced to the surface through the production well via any number of known artificial lift methods.
Description
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METHOD FOR ACHrEVING C0MMUNICATI0N
B~TWEEN INJECTION AND PRODUCTION
Technical Field This invention relatas generally to methods for the recovery of hydrocarbons from subterranean formations. More particularly, this invention relates to methods for enhancing gravity drainage of bitumen in tar sands by establishing an initial communication path between production and injection wells~
Background of the Invention There exist large depos;ts of ~iscous hydrocarbons or bitumen in many areas of the world, such as the Athabasca and Cold Lake regions in Alberta, Canada, the Jobo region in Venezuela, and the Edna and Sisquoc regions in California.
These deposits are often referred to as 9'tar sand" deposits.
Tar sands may be described as sandstone that chiefly contains very viscous to semisolid to solid bitumen, which, in its natural state, cannot be recovered by primary production methods. Tar sand deposits can extend for kilometers and occur in various thicknesses. They can also occur at various depths ' they can lie at or near the earth's surface or under an overburden which may be as much as several hundred meters thick.
Surface mining methods are utilized to extract bitumen from tar sand deposits occurring near the earth's surface. Such surface mining methods are well established in the art.
Bitumen present in tar sand deposits which occurs too deep within the earth to be recoverable by conventional surface mining methods and which is too viscous to flow or be pumped to the surface at native conditions must be extracted by utiliæing in-situ production methods. The Cold Lake region in Alberta, Canada is an example of tar sand reservoirs requiring the use of in-situ production methods for the recovery of bitumen.
In-situ recovery of bitumen from the deeper reservoirs is made possible by utilizing thermal stimulation techniques.
Briefly, thermal stimulation comprises raising the temperature Of the bitumen to reduce its viscosity so that the bitumen will flow to a production well.
Reservoir thermal stimulation techniques may be enhanced by the use of directional drilling techniques.
Horizontal wells, for example, provide additional reservoir intersection. By thus optimizing the flow geometries, they 5'7 increase the productivi~y and, therefore, the utility of thermal stimulation in association with gravity drainage recovery methods.
Various thermal stimulation methocls have been proposed in the prior art. For example, U.S. Patent 4,344,485 to Butler discloses a thermal method for continuous recovery of viscous hydrocarbons by gravity drainage. Butler's method includes an injection well for injecting a heated fluid to encourage production of ~itumen through a second, production well. Butler suggests that communication between th~ production and injection wells may be initiated by fracturing of the reservoir. In order to achieve communication between the wells, the product;on well and the injection well are drilled along the fracture trend of the formation. Steam is injected via the fractured injection well to form a flow path along the fractures between the two wells. Butler suggests that as the steam condenses and gives up its heat to the formation, the viscous hydrocarbons are mobilized and oil drains continuously, by gravity, to the production well, where it is recovered, Butler also discloses the use of various well configurations and orientations, in combination with thermal stimulation, to improve the level of hydrocarbon recovery.
RepresentatiYe examples of various other thermal stimulation methods are disclosed in U.S. Patent Nt~bers:
4~265,310 to Britton et al; 4,037,658 to Anderson; 3,960,213 to Striegler et al; 4,2489302 to Churchman, 4,535,845 to Brown et al; and 4,390,067 to Willman.
Although thermal stimulation and directional drilling methods represent a substantial contribution to the art of bitumen recovery from tar sand deposits, these methods suffer from certain limitations.
It is well established that the success of these recovery methods depends upon establishing and maintaining a communication channel between the injection and production wells, However, the establishment of hydraulic communication channels between production and injection wells is an uncertain art. While production and injection wells are, usually, in close proximity to each other inside the tar sands, often as close as a few meters, there is generally no hydraulic communicatlon between them in the reservoir.
As suggested in Butler, an existing technique for obtaining communication between production and injection wells in tar sands deposits consist~ of fracturing the reservoir so that a commtmication path may be established along the fractures between the wells.
The success of establishing and maintaining a communication path between injection and producing wells via hydraulic fracturing is highly dependent, however, on the stress profile and fracture orientation of the reservoir. While wells usually are oriented so as to take advantage of the natural fracture orientation of the reservoir, the reservoir's natural fracture orientation is many times unascertainable. This makes the success of this method difficult to predict. Evel~ in reservoirs where the fracture orientation is ascertainable, fractures may occur in such a fashion as to intersect in undesirable patterns or as not to intersec~ at all.
In addition to th~ difficulties mentioned above, fractures from two or more injector wells may intersect each other before either of them has intersected a production well.
In this case, a short-circuit situation is created which leaves little hope of ever linking the injector well(s) to the production well(s).
To further complicate matters, there exists little data regarding the distribution of ~orce and movement in the reservoir sands during fracturing. It is conceivable therefore that, if and when a fracture intersects the production well, mechanical damage to tubulars and/or connectors will occur.
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Finally, at shallow depths, fracturing to the surface may occur. When fracturing to the surface occurs, satisfactory pressure cannot be maintained in the reservoir during the suhsequent operations.
In addition to the uncertainties associated with hydraulic fracturing as a method for initiating well to well communication in tar sands, the stress state of the reservoir, upon which this method is dependent, limits the freedom wh;ch may be exercised in the orientation of the productio~ and injection wells. Use of the horizont~l well concept is therefore limited to only those flow geometries which are compatible with the natural fracture orientation of the reservoir.
~ ethods less successful than fracturing have been proposed for establishing communication between injection and production welts. One such method proposes to create communication by using solvents or chemical agents to leach a communication path between wells. A representative e~ample of this method is disclosed in U.S. Patent 3,825,066 to Redford.
; Redford discloses a method for developing inter-well communication in tar sands by contacting the bituminous sands with ozone to render the bitumen partly soluble. The method of Redford assumes that communication may be readily established between injection and production wells; it thus fails to indicate how initial communication is accomplished.
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Another method suggested for creating a commlmication path between production and injection wells involves electrical heating. The difficulties associated with setting up the proper electrical pattern in the reservoir make this method impractical.
Other bitumen production methods assume that a communication path may be readily achieved by merely providing heat to the reservoir. One such method has been applied to the particular case of a horizontal well with one or more vertical well bottom hole locations nearby. This method comprises circulating steam through the horizontal well to heat the portion of the reservoir around the horizontal well, thus intending to create a communication path to the vertical well, or wells, by diffusion of heat. The problem with this method is that diffusion of heat from a line source is too slow a process to be practical and the direction of heat transfer is not a ; controllable variable, with the result that communication between the wells remains uncertain.
For the in-situ recovery of bitumen from tar sands, therefore, there exists a need for a method of establishing and maintaining a communication path between injection and production wells which may be practiced with certainty and which is independent of the particular reservoir's physical characteristics.
Summary of the Invention The present disclosure presents a method for establishing and maintaining communications between wells which alleviates the above-mentioned limitations. A method is described for establishing communication between injection and production wells penetrating a bituminous tar sand deposit which includes: excavating a cavity at a point where the injection well is proximate to the production well, opening the injection well to production, and injecting a fluid in the production well at a pressure less than fracture pressure so as to cause the part of the subterranean formation adjacent the production well and near the injection well to give way, forming a com~unication path between the injection and production wells.
It is an advantage of this disclosure that it provides a means for establishing and maintaining communications channels between injection and production wells located in tar sand deposits which is independent of the stress characteristics of the tar sand deposits.
It is a further advantage that it provides a method for establishing, maintaining, and initiating gravity drainage of bit~en in tar sand deposits and provides flexibility in field operations without the limitations and disadvantages of the prior art.
~ar Si7 g More particularly, in accordance with a first aspect of the invent$on there is provided a method for establishing communication be~ween an in~ection well and a production well penetrating tar sand deposits, including the steps of:
(a) excavating a cavity at a position at which said inJection well is proximate to said production well;
(b) opening said injection well to production; and (c) In~ecting a fluid through said production well into said tar sand deposit at a pressure less than fracture pressure and allowing the part of the subterranean formation intermediate said production well and said cavity to give way, creating a highly permeable zone between said injection and production wells, In accordance with a second aspect of the invention there is provided a method for establishing communication between a substantially horizontal well and a substantially vertical well penetrating a tar sand deposit, including the steps of:
(a) excavating a cavity at a position at which said vertical well is proximate to said horizontal well;
(b) opening said vertical well to production; and (c) injecting a fluid in said horizontal well at a pressure less than fracture pressure and allowing the part of ths subterranean formation intermedia~e said horizontal well and said proximate cavity to give way, forming a communication path between said vertical well and said horizontal well.
In accordance with a third aspect of the invention there is provided a method for establishi.ng communication between a first well and a plurality of second wells penetrating a subterranean formation including tar sand deposits, including the steps of:
, (a) excavating a cavity at locations where each second well is proximate to said first well;
(b) opening said second wells to production;
(cj in~ecting a fluid in said first well at pressures less than fracture pressure for said formation;
(d) obtaining flow in at least one of said second wells and then shutting-in said second well while continuing to in~ect fluid in said first well until ~low is obtained in another second well; and (e) repeating step (d) until flow has been obtained in a-desirable number of second wells, thereby indicating that the subterranean formations ad~acent to said first well and proximate said dssirable number of second wells have given way, creating communication paths between said first well and said desirable number of second wells.
In accordance with a fourth aspect of the invent$on there is provided a method for recovering bitumen from a tar sand formation contain$ng bitumen which comprises:
(a) drilling at least one substantially vertical well and at least one substantially horizontal well into ~aid tar sand Eorlll,ation .~ , (b) excavating a cavity around the base of said substantially vertical well and opening sald substantially vertical well to production;
(c) injecting a fluid in said substantially horizontal well at a pressure less than fracture pressure to cause the part of the subterranean formation intermediate said substantially horizontal well and said proximate cavity to give way, creating a communication path between siaid wells;
(d) injecting hot fluid into the formation, so as to increase the temperature and reduce the viscosity of said bitumen contained in said formation; and (e) allowing gravity drainage of bitumen to said substantially horizontal well and producing bltumen from said formation through said substantially horizontal well.
In accordance with a fifth aspect of the invention there is provided a method for recovering bitumen from a tar sand ~ormation, comprising the steps of:
(a) drilling a first well into said tar sand formation;
(b) drilling a second well into said tar sand formation, said second well being drilled to reach a position proximate said first well;
(c) establishing a cavity surrounding that portion of said second well proximate said first well;
(d) perforating said first well at a position proximate said second well to establish a first perEorated zone in said first well; and (e) in~ecting fluid from said first well through said first perforated zone and into said second well via said cavity, said injection occurring at a pressure below the fracture pressure of said tar sand formation, whereby that portion of said tar sand formation intermediate said first perforated zone and said cavity gives way, establishing a zone of enhanced permeability intermediate said first and second wells.
Embodiments o the invention will now be described with reference to the accompanying drawings wherein:
FIGURE 1 is a schematic cross sectional view of a preferred embodiment of the invention illustrated ~y one vertical well and one horizontal well in communication with each other as accomplished by practicing this invention.
~5 FIGURE 2 ls a schematic cross sectional view of another embodiment of the invention illustrated by several "vertical" inJection wells (which may be deviated with respect to the earth's surface) in con~unction with one horizontal well.
FIGURE 3 is a schematic site illustration of another embodiment of the invention in a field arrangement where several injection wells have been drilled from a common surface drilling pad in combination with two horizontal production wells.
FIGURE 4 is a schematic view of an embodiment of the invention where a deviated or vertical well terminates directly above the horizontal well.
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~ IGURES 5 and 6 schematically illustrate a fifth and a sixth embodiment of the invention in situations where the cavity is located close to the horizontal well and said cavity is not necessarily located at the bottom end of the vertical well and directly above the horizontal well.
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 Description of the Preferred Embodiments The embodiments concern methods for establishing communication between injection and production wells penetrating a bituminous tar sands deposit and the recovery of product from tar sands. The principal steps in the preferred embodiment include:
excavating a cavity at a point where the injection well is ~roximate to the production well, opening the injection well to production, and in~ecting a fluid in the production well at a pressure less than fracture pressure so as to cause the part of the subterranean formation ad~acent the production well and near the injection well to give way.
This establishes a zone filled with unconsolidated, expanded, highly permeable tar sands. This zone is referred to herein as a "communication path" between the in~ection and production wells. The communication path greatly enhances the production oi bitumen from the 2S tar sand deposit.
;7 FIGURE 1 schematically illustrates a cross section of a tar sands formation 10 and overburden 20 in the vertical plane through a substantially horizontal well 110. One substantially vertical well 112 is drilled to reach a subterranean tar sand formation 10 near horizontal well 110.
~ orizontal well 110 is representative of and understood to mean by reference herein, any variation of such a well, including a well which is substantially vertical from the surface through the overburden and which deviates to substantially horizontal in the pay zone, which may be a tar sand formation 10.
Uith reference to horizontal well 110 and vertical well 112 in Fl~URE 1, a cavity 122 is excavated proximate the location of horizontal well 110. Such excavation will usually be at or near the base of vertical well 112. Excavated cavity 122 may be spherical or cylindrical or one-sided toward the horizontal well or somewhat irregular in form. Typically, the location of cavity 122 will be in the region where vertical well 112 is closest to horizontal well 110. In a typical field arrangement, the distance between vertical well 112 and horizontal well 110 will be less than about 50 meters in the region where the vertical well is closest to the horizontal well. Cavity 122 is, thus, located within this region. The vt ~
~7 distance between vertical well 112 and horizontal well 110 is lmportant to the extent necessary to determine the size of cavity 122. As will be recognized by those skilled in the art, the optimum distance between vertical well 112 and horizontal well 110 in any field arrangement will depend upon the tar sands characteristics, the desired field well ar~angement which will be used with the particular production method, and any practical aspects associated with the size of the cavity required.
The excavation of ca~ity 122 may be accomplished in a number of different ways. The methods used to accomplish such excavations are well known in the art. Such methods include: circulating drilling mud at high rates, or utilizing conventional water jets. Many other effective ways of forming a cavity at the bottom of a well may be practiced to obtain the desired effect. These techniques are well established and known to those skilled in the art. The manner of excavating such a cavity 122 is not as important to practice the new methods here described as that a cavity 122 be excavated.
Excavation continues until a cavity 122 of predetermined size has been washed out, as judged, for example, by the volume of sand brought to surface. The siæe of cavity 122 should be such as to leave a zone between vertical well 112 and horizontal well 110 to allow a collapse of the tflr sands proximate to cavlty 122 when fluid is in~ected into the horizontal well 110 as described below.
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The amount of excavation required is usually small compared to the desired size of the communication path because the bulk volume of tar sands increase when the grain to grain contacts are disrupted. It is estimated that if a commlmication path of 10 cubic meters in volume is desired, some 3 cubic meters of volume needs to be excavated so that the remaining undisturbed 7 cubic meters of sand can expand to 10 cubic meters bulk volume. The expansion is such that the volume which needs to be excavated is about 30% of the expanded volume.
The volume of tar sands to be excavated is determined by the si~e of the communication path desired. If, for example, vertical well 112 is located 5 meters above horizontal well 110 and is laterally offset by 5 meters, the path length would be approximately 7 meters. If the desired diameter for the communication path is one meter, then the tar sands volume would be approximately 5.5 cubic meters. Upon disturbing the tar sands, their bulk volume, as explained above, would expand approximately 1.6 cubic meters. This expansion fills the pre-excavated void, which, lf spherical, would have a radius of approximately 0.7 meters.
Where a vertical well ends directly above the horizontal well, the cavity is made at the location of the bottom hole of the vertical well, or slightly higher, as illustrated in FIGURE 4. In some cases a vertical well is laterally off-set from the horizontal well and may penetrate deeper into the formation. In such cases the cavity may preferably be excavated slightly above the level of the horizontal well or in close proximity to the horizontal well as illustrated in FIGURES 5 and 6.
After cavity 122 i5 excavated, vertical well 112 is temporarily left open to production. Fluid is then iniected in substantially horizontal well 110 at a pressure increasing from hydrostatic to less than the natural fracture pressure of the reservoir. The fluid will prçferably be water. Chemicals and~
heat may be added to the fluid as desirable. At a location along the length of horizontal well 110 where the cavity around vertical well 122 is nearby, the reservoir sands adjacent to the horizontal well lack support and will "give way" to create communication path or zone 132 between horizontal well 110 and vertical well 112. "Give way" is defined herein to mean a collapse of the consolidated tar sands intermediate the excavated cavity and the horizontal or production well caused by the pressure of the fluid in the horizontal or production well and resulting in the zone of unconsolidated, highly permeable tar sands referred to berein as the communication path.
The injection of fluid into the horizontal well will cause the wall of the cavity to crumble. The cavity will fill with disturbed, unconsolidated, expanded tar sands and a highly permeable zone will be created between the hori~ontal well and the vertical well. Sand may be produced by vertical well 112 during the sta~t-up process and during the subsequent period of improving the hydraulic communication to a desired quality.
While the minimum amount of excavation required for forming a communication path is relatively small, there are advantages in excavating more than the minimum volume. If a large volume of tar sands is excavated initially at the vertical well~ the communication zone subsequently created will tend to extend itself upwards around the vertical well. This will create a highly permeable "chimney" which will provide rapid growth of the steam chamber during subsequent production operations utilizing steam stimulation. This will result in a rapid start-up of bitumen recovery via gravity drainage.
The minimum volume of excavation may be estimated from an assumption as to the size desired for the communication path. Suppose a 30-meter high chimney of 2-meter diameter is desired. The estimated tar sands volume is thus lO0 cubic meters. Again, assuming that a 30~ volume expansion must be accommodated, the inltial excavation mu6t remove approximately 30 cubic meter8 of undisturbed reservoir volume. At the surface, loose pack material would measure approximately 40 cubic meters.
After the communication path between the vertical well and the horizontal well is created, field production operations may begin. The horizontal well then becomes a producing well, while the vertical well is used to inject hot water, steam, solvents, chemical solutions or any material which will reduce the viscosity of the heavy oil in situ. Steam, for example, is injected into the vertical well to encourage the drainage of bitumen within the reservoir. In the reservoir the steam condenses giving up its heat to the surrounding oil sands. The condensed steam and heated oil flow by gravity to the horizontal production well at the bottom of the communication zone.
Bitumen is produced to the surface via the horizontal well.
Bitumen production to surface may be accomplished via a number of known artificial lift methods. FIGURE 1 illustrates a commonly used sucker rod surface pumping unit 40, which may be emplDyed to pump to the surface the bi~umen which has drained into the horizontal well.
FIGURE 2 illustrates the case of multiple vertical wells 212, 213, and 214 being used in conjunction with one ; horizontal well 210. The different bottom hole cavities 222~
223, and 224 associated with the respective vertical wells will each probably have different volumes of native reservoir sand separating their respective bo~mdaries from horizontal well 210. These differing volumes of undisturb0d sand offer differing resistances to breakdown by fluid pressure in the horizontal well.
Fluid is injected in horizontal well 210 and the vertical well with the weakest resistance to hydraulic communication with the horizontal well, say for example vertical 3~
well 212, will begin to flow first. This first-flowing vertical well is then allowed to flow until a satisfactory in-situ communication path 232 is established. Once satisfactory in-situ communication is established, the vert;cal well is 5 shut-in. The fluid pressure in the horizontal well is then increased gradually until the occurence of fluid breakthrough to a second vertical well, for example 213. ~fter satisfactory flow is established, this second vertical well is shut-in. The sequence is repeated until all vertical wells have been made to 10 achieve hydraulic communication with the horizontal w~ll.
Subsequently, if desired, the resistance to communication between the horizontal well and each vertical well will be fine-tuned to make the resistance for each vertical well equal to that for each of the other vertical wells. This can be done by selectively flowing and shutting-in the vertical wells to achieve a hydraulically balanced system.
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Once hydraulic balance is established, the wells are ready for production enhancement operations. Such operations may include injectlng steam or another fluid through the vertical injection wells to stimulate gravity drainage of bitumen in the reservoir toward the production well via the previously established communication paths, 232, 233, and 234.
Bitumen may then be produced from the horizontal well utilizing techniques well known in the art.
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; FIGURE 3 illustrates a field arrangement comprising several injection wells 312-317 in combination with two horizontal wells 310 and 311 where the vertical wells were drilled from one common surface drilling pad 300. The arrangement illustrated in FIGURE 3 may be part of a larger field pattern including other drilling pads.
Cavities 322-327 are excavated thru injection wells 312-317 at points proximate the location of a horizontal well. While injection wells 312-317 are open to production, a fluid is injected in each horiæontal well at a pressure below fracture pressure. As in the earlier example, the injection well with the weakest resistance to hydraulic communication with its associated horizontal well will begi~ to flow first. Upon reaching satisfactory communication, this well will be shut-in.
The fluid pressure in the horizontal well will then be increased until satisfactory communication is obtained in a second well.
The procedure is then repeated until communication is established between each horizontal well and its associated injection wells. After hydraulic communication is fine-tuned by selectively flowlng and shutting-in the vertical wel]s, the field is ready for gravity drainage production operations.
Steam or other fluid is injected through the injection wells to initiate bitumen flow by gravity drainage towards the horizontal wells, where the bitumen is produced to surface.
FIGURES 4-69 illustrate different configurations which may be encountered during field operations.
FIGURE 4, illustrates the situation where injection ~-well 412 is directly above horizontal well 410. A cavity 422 is excavated at the bottom hole location of injection well 412 to form co~nunication path 432.
In FIGURE 5, horizontal well 510 is located to the side of injection well 512. Cavity 522 is excavated at a point where injection well 512 is proximate the horizontal well in order to form communication path 532.
FIGURE 6 illustrates the situation where horizontal well 610 is located to the side of injection well 612 near the injection well's bottom hole locations. Cavity 622 is excavated at the bottom hole location of injection well 612 in order to create communication path 632.
Changes and modifications to the specifically described embodiments can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the claims which follow.
METHOD FOR ACHrEVING C0MMUNICATI0N
B~TWEEN INJECTION AND PRODUCTION
Technical Field This invention relatas generally to methods for the recovery of hydrocarbons from subterranean formations. More particularly, this invention relates to methods for enhancing gravity drainage of bitumen in tar sands by establishing an initial communication path between production and injection wells~
Background of the Invention There exist large depos;ts of ~iscous hydrocarbons or bitumen in many areas of the world, such as the Athabasca and Cold Lake regions in Alberta, Canada, the Jobo region in Venezuela, and the Edna and Sisquoc regions in California.
These deposits are often referred to as 9'tar sand" deposits.
Tar sands may be described as sandstone that chiefly contains very viscous to semisolid to solid bitumen, which, in its natural state, cannot be recovered by primary production methods. Tar sand deposits can extend for kilometers and occur in various thicknesses. They can also occur at various depths ' they can lie at or near the earth's surface or under an overburden which may be as much as several hundred meters thick.
Surface mining methods are utilized to extract bitumen from tar sand deposits occurring near the earth's surface. Such surface mining methods are well established in the art.
Bitumen present in tar sand deposits which occurs too deep within the earth to be recoverable by conventional surface mining methods and which is too viscous to flow or be pumped to the surface at native conditions must be extracted by utiliæing in-situ production methods. The Cold Lake region in Alberta, Canada is an example of tar sand reservoirs requiring the use of in-situ production methods for the recovery of bitumen.
In-situ recovery of bitumen from the deeper reservoirs is made possible by utilizing thermal stimulation techniques.
Briefly, thermal stimulation comprises raising the temperature Of the bitumen to reduce its viscosity so that the bitumen will flow to a production well.
Reservoir thermal stimulation techniques may be enhanced by the use of directional drilling techniques.
Horizontal wells, for example, provide additional reservoir intersection. By thus optimizing the flow geometries, they 5'7 increase the productivi~y and, therefore, the utility of thermal stimulation in association with gravity drainage recovery methods.
Various thermal stimulation methocls have been proposed in the prior art. For example, U.S. Patent 4,344,485 to Butler discloses a thermal method for continuous recovery of viscous hydrocarbons by gravity drainage. Butler's method includes an injection well for injecting a heated fluid to encourage production of ~itumen through a second, production well. Butler suggests that communication between th~ production and injection wells may be initiated by fracturing of the reservoir. In order to achieve communication between the wells, the product;on well and the injection well are drilled along the fracture trend of the formation. Steam is injected via the fractured injection well to form a flow path along the fractures between the two wells. Butler suggests that as the steam condenses and gives up its heat to the formation, the viscous hydrocarbons are mobilized and oil drains continuously, by gravity, to the production well, where it is recovered, Butler also discloses the use of various well configurations and orientations, in combination with thermal stimulation, to improve the level of hydrocarbon recovery.
RepresentatiYe examples of various other thermal stimulation methods are disclosed in U.S. Patent Nt~bers:
4~265,310 to Britton et al; 4,037,658 to Anderson; 3,960,213 to Striegler et al; 4,2489302 to Churchman, 4,535,845 to Brown et al; and 4,390,067 to Willman.
Although thermal stimulation and directional drilling methods represent a substantial contribution to the art of bitumen recovery from tar sand deposits, these methods suffer from certain limitations.
It is well established that the success of these recovery methods depends upon establishing and maintaining a communication channel between the injection and production wells, However, the establishment of hydraulic communication channels between production and injection wells is an uncertain art. While production and injection wells are, usually, in close proximity to each other inside the tar sands, often as close as a few meters, there is generally no hydraulic communicatlon between them in the reservoir.
As suggested in Butler, an existing technique for obtaining communication between production and injection wells in tar sands deposits consist~ of fracturing the reservoir so that a commtmication path may be established along the fractures between the wells.
The success of establishing and maintaining a communication path between injection and producing wells via hydraulic fracturing is highly dependent, however, on the stress profile and fracture orientation of the reservoir. While wells usually are oriented so as to take advantage of the natural fracture orientation of the reservoir, the reservoir's natural fracture orientation is many times unascertainable. This makes the success of this method difficult to predict. Evel~ in reservoirs where the fracture orientation is ascertainable, fractures may occur in such a fashion as to intersect in undesirable patterns or as not to intersec~ at all.
In addition to th~ difficulties mentioned above, fractures from two or more injector wells may intersect each other before either of them has intersected a production well.
In this case, a short-circuit situation is created which leaves little hope of ever linking the injector well(s) to the production well(s).
To further complicate matters, there exists little data regarding the distribution of ~orce and movement in the reservoir sands during fracturing. It is conceivable therefore that, if and when a fracture intersects the production well, mechanical damage to tubulars and/or connectors will occur.
. .
Finally, at shallow depths, fracturing to the surface may occur. When fracturing to the surface occurs, satisfactory pressure cannot be maintained in the reservoir during the suhsequent operations.
In addition to the uncertainties associated with hydraulic fracturing as a method for initiating well to well communication in tar sands, the stress state of the reservoir, upon which this method is dependent, limits the freedom wh;ch may be exercised in the orientation of the productio~ and injection wells. Use of the horizont~l well concept is therefore limited to only those flow geometries which are compatible with the natural fracture orientation of the reservoir.
~ ethods less successful than fracturing have been proposed for establishing communication between injection and production welts. One such method proposes to create communication by using solvents or chemical agents to leach a communication path between wells. A representative e~ample of this method is disclosed in U.S. Patent 3,825,066 to Redford.
; Redford discloses a method for developing inter-well communication in tar sands by contacting the bituminous sands with ozone to render the bitumen partly soluble. The method of Redford assumes that communication may be readily established between injection and production wells; it thus fails to indicate how initial communication is accomplished.
.
Another method suggested for creating a commlmication path between production and injection wells involves electrical heating. The difficulties associated with setting up the proper electrical pattern in the reservoir make this method impractical.
Other bitumen production methods assume that a communication path may be readily achieved by merely providing heat to the reservoir. One such method has been applied to the particular case of a horizontal well with one or more vertical well bottom hole locations nearby. This method comprises circulating steam through the horizontal well to heat the portion of the reservoir around the horizontal well, thus intending to create a communication path to the vertical well, or wells, by diffusion of heat. The problem with this method is that diffusion of heat from a line source is too slow a process to be practical and the direction of heat transfer is not a ; controllable variable, with the result that communication between the wells remains uncertain.
For the in-situ recovery of bitumen from tar sands, therefore, there exists a need for a method of establishing and maintaining a communication path between injection and production wells which may be practiced with certainty and which is independent of the particular reservoir's physical characteristics.
Summary of the Invention The present disclosure presents a method for establishing and maintaining communications between wells which alleviates the above-mentioned limitations. A method is described for establishing communication between injection and production wells penetrating a bituminous tar sand deposit which includes: excavating a cavity at a point where the injection well is proximate to the production well, opening the injection well to production, and injecting a fluid in the production well at a pressure less than fracture pressure so as to cause the part of the subterranean formation adjacent the production well and near the injection well to give way, forming a com~unication path between the injection and production wells.
It is an advantage of this disclosure that it provides a means for establishing and maintaining communications channels between injection and production wells located in tar sand deposits which is independent of the stress characteristics of the tar sand deposits.
It is a further advantage that it provides a method for establishing, maintaining, and initiating gravity drainage of bit~en in tar sand deposits and provides flexibility in field operations without the limitations and disadvantages of the prior art.
~ar Si7 g More particularly, in accordance with a first aspect of the invent$on there is provided a method for establishing communication be~ween an in~ection well and a production well penetrating tar sand deposits, including the steps of:
(a) excavating a cavity at a position at which said inJection well is proximate to said production well;
(b) opening said injection well to production; and (c) In~ecting a fluid through said production well into said tar sand deposit at a pressure less than fracture pressure and allowing the part of the subterranean formation intermediate said production well and said cavity to give way, creating a highly permeable zone between said injection and production wells, In accordance with a second aspect of the invention there is provided a method for establishing communication between a substantially horizontal well and a substantially vertical well penetrating a tar sand deposit, including the steps of:
(a) excavating a cavity at a position at which said vertical well is proximate to said horizontal well;
(b) opening said vertical well to production; and (c) injecting a fluid in said horizontal well at a pressure less than fracture pressure and allowing the part of ths subterranean formation intermedia~e said horizontal well and said proximate cavity to give way, forming a communication path between said vertical well and said horizontal well.
In accordance with a third aspect of the invention there is provided a method for establishi.ng communication between a first well and a plurality of second wells penetrating a subterranean formation including tar sand deposits, including the steps of:
, (a) excavating a cavity at locations where each second well is proximate to said first well;
(b) opening said second wells to production;
(cj in~ecting a fluid in said first well at pressures less than fracture pressure for said formation;
(d) obtaining flow in at least one of said second wells and then shutting-in said second well while continuing to in~ect fluid in said first well until ~low is obtained in another second well; and (e) repeating step (d) until flow has been obtained in a-desirable number of second wells, thereby indicating that the subterranean formations ad~acent to said first well and proximate said dssirable number of second wells have given way, creating communication paths between said first well and said desirable number of second wells.
In accordance with a fourth aspect of the invent$on there is provided a method for recovering bitumen from a tar sand formation contain$ng bitumen which comprises:
(a) drilling at least one substantially vertical well and at least one substantially horizontal well into ~aid tar sand Eorlll,ation .~ , (b) excavating a cavity around the base of said substantially vertical well and opening sald substantially vertical well to production;
(c) injecting a fluid in said substantially horizontal well at a pressure less than fracture pressure to cause the part of the subterranean formation intermediate said substantially horizontal well and said proximate cavity to give way, creating a communication path between siaid wells;
(d) injecting hot fluid into the formation, so as to increase the temperature and reduce the viscosity of said bitumen contained in said formation; and (e) allowing gravity drainage of bitumen to said substantially horizontal well and producing bltumen from said formation through said substantially horizontal well.
In accordance with a fifth aspect of the invention there is provided a method for recovering bitumen from a tar sand ~ormation, comprising the steps of:
(a) drilling a first well into said tar sand formation;
(b) drilling a second well into said tar sand formation, said second well being drilled to reach a position proximate said first well;
(c) establishing a cavity surrounding that portion of said second well proximate said first well;
(d) perforating said first well at a position proximate said second well to establish a first perEorated zone in said first well; and (e) in~ecting fluid from said first well through said first perforated zone and into said second well via said cavity, said injection occurring at a pressure below the fracture pressure of said tar sand formation, whereby that portion of said tar sand formation intermediate said first perforated zone and said cavity gives way, establishing a zone of enhanced permeability intermediate said first and second wells.
Embodiments o the invention will now be described with reference to the accompanying drawings wherein:
FIGURE 1 is a schematic cross sectional view of a preferred embodiment of the invention illustrated ~y one vertical well and one horizontal well in communication with each other as accomplished by practicing this invention.
~5 FIGURE 2 ls a schematic cross sectional view of another embodiment of the invention illustrated by several "vertical" inJection wells (which may be deviated with respect to the earth's surface) in con~unction with one horizontal well.
FIGURE 3 is a schematic site illustration of another embodiment of the invention in a field arrangement where several injection wells have been drilled from a common surface drilling pad in combination with two horizontal production wells.
FIGURE 4 is a schematic view of an embodiment of the invention where a deviated or vertical well terminates directly above the horizontal well.
~,, s~
~ IGURES 5 and 6 schematically illustrate a fifth and a sixth embodiment of the invention in situations where the cavity is located close to the horizontal well and said cavity is not necessarily located at the bottom end of the vertical well and directly above the horizontal well.
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 Description of the Preferred Embodiments The embodiments concern methods for establishing communication between injection and production wells penetrating a bituminous tar sands deposit and the recovery of product from tar sands. The principal steps in the preferred embodiment include:
excavating a cavity at a point where the injection well is ~roximate to the production well, opening the injection well to production, and in~ecting a fluid in the production well at a pressure less than fracture pressure so as to cause the part of the subterranean formation ad~acent the production well and near the injection well to give way.
This establishes a zone filled with unconsolidated, expanded, highly permeable tar sands. This zone is referred to herein as a "communication path" between the in~ection and production wells. The communication path greatly enhances the production oi bitumen from the 2S tar sand deposit.
;7 FIGURE 1 schematically illustrates a cross section of a tar sands formation 10 and overburden 20 in the vertical plane through a substantially horizontal well 110. One substantially vertical well 112 is drilled to reach a subterranean tar sand formation 10 near horizontal well 110.
~ orizontal well 110 is representative of and understood to mean by reference herein, any variation of such a well, including a well which is substantially vertical from the surface through the overburden and which deviates to substantially horizontal in the pay zone, which may be a tar sand formation 10.
Uith reference to horizontal well 110 and vertical well 112 in Fl~URE 1, a cavity 122 is excavated proximate the location of horizontal well 110. Such excavation will usually be at or near the base of vertical well 112. Excavated cavity 122 may be spherical or cylindrical or one-sided toward the horizontal well or somewhat irregular in form. Typically, the location of cavity 122 will be in the region where vertical well 112 is closest to horizontal well 110. In a typical field arrangement, the distance between vertical well 112 and horizontal well 110 will be less than about 50 meters in the region where the vertical well is closest to the horizontal well. Cavity 122 is, thus, located within this region. The vt ~
~7 distance between vertical well 112 and horizontal well 110 is lmportant to the extent necessary to determine the size of cavity 122. As will be recognized by those skilled in the art, the optimum distance between vertical well 112 and horizontal well 110 in any field arrangement will depend upon the tar sands characteristics, the desired field well ar~angement which will be used with the particular production method, and any practical aspects associated with the size of the cavity required.
The excavation of ca~ity 122 may be accomplished in a number of different ways. The methods used to accomplish such excavations are well known in the art. Such methods include: circulating drilling mud at high rates, or utilizing conventional water jets. Many other effective ways of forming a cavity at the bottom of a well may be practiced to obtain the desired effect. These techniques are well established and known to those skilled in the art. The manner of excavating such a cavity 122 is not as important to practice the new methods here described as that a cavity 122 be excavated.
Excavation continues until a cavity 122 of predetermined size has been washed out, as judged, for example, by the volume of sand brought to surface. The siæe of cavity 122 should be such as to leave a zone between vertical well 112 and horizontal well 110 to allow a collapse of the tflr sands proximate to cavlty 122 when fluid is in~ected into the horizontal well 110 as described below.
~' d~
The amount of excavation required is usually small compared to the desired size of the communication path because the bulk volume of tar sands increase when the grain to grain contacts are disrupted. It is estimated that if a commlmication path of 10 cubic meters in volume is desired, some 3 cubic meters of volume needs to be excavated so that the remaining undisturbed 7 cubic meters of sand can expand to 10 cubic meters bulk volume. The expansion is such that the volume which needs to be excavated is about 30% of the expanded volume.
The volume of tar sands to be excavated is determined by the si~e of the communication path desired. If, for example, vertical well 112 is located 5 meters above horizontal well 110 and is laterally offset by 5 meters, the path length would be approximately 7 meters. If the desired diameter for the communication path is one meter, then the tar sands volume would be approximately 5.5 cubic meters. Upon disturbing the tar sands, their bulk volume, as explained above, would expand approximately 1.6 cubic meters. This expansion fills the pre-excavated void, which, lf spherical, would have a radius of approximately 0.7 meters.
Where a vertical well ends directly above the horizontal well, the cavity is made at the location of the bottom hole of the vertical well, or slightly higher, as illustrated in FIGURE 4. In some cases a vertical well is laterally off-set from the horizontal well and may penetrate deeper into the formation. In such cases the cavity may preferably be excavated slightly above the level of the horizontal well or in close proximity to the horizontal well as illustrated in FIGURES 5 and 6.
After cavity 122 i5 excavated, vertical well 112 is temporarily left open to production. Fluid is then iniected in substantially horizontal well 110 at a pressure increasing from hydrostatic to less than the natural fracture pressure of the reservoir. The fluid will prçferably be water. Chemicals and~
heat may be added to the fluid as desirable. At a location along the length of horizontal well 110 where the cavity around vertical well 122 is nearby, the reservoir sands adjacent to the horizontal well lack support and will "give way" to create communication path or zone 132 between horizontal well 110 and vertical well 112. "Give way" is defined herein to mean a collapse of the consolidated tar sands intermediate the excavated cavity and the horizontal or production well caused by the pressure of the fluid in the horizontal or production well and resulting in the zone of unconsolidated, highly permeable tar sands referred to berein as the communication path.
The injection of fluid into the horizontal well will cause the wall of the cavity to crumble. The cavity will fill with disturbed, unconsolidated, expanded tar sands and a highly permeable zone will be created between the hori~ontal well and the vertical well. Sand may be produced by vertical well 112 during the sta~t-up process and during the subsequent period of improving the hydraulic communication to a desired quality.
While the minimum amount of excavation required for forming a communication path is relatively small, there are advantages in excavating more than the minimum volume. If a large volume of tar sands is excavated initially at the vertical well~ the communication zone subsequently created will tend to extend itself upwards around the vertical well. This will create a highly permeable "chimney" which will provide rapid growth of the steam chamber during subsequent production operations utilizing steam stimulation. This will result in a rapid start-up of bitumen recovery via gravity drainage.
The minimum volume of excavation may be estimated from an assumption as to the size desired for the communication path. Suppose a 30-meter high chimney of 2-meter diameter is desired. The estimated tar sands volume is thus lO0 cubic meters. Again, assuming that a 30~ volume expansion must be accommodated, the inltial excavation mu6t remove approximately 30 cubic meter8 of undisturbed reservoir volume. At the surface, loose pack material would measure approximately 40 cubic meters.
After the communication path between the vertical well and the horizontal well is created, field production operations may begin. The horizontal well then becomes a producing well, while the vertical well is used to inject hot water, steam, solvents, chemical solutions or any material which will reduce the viscosity of the heavy oil in situ. Steam, for example, is injected into the vertical well to encourage the drainage of bitumen within the reservoir. In the reservoir the steam condenses giving up its heat to the surrounding oil sands. The condensed steam and heated oil flow by gravity to the horizontal production well at the bottom of the communication zone.
Bitumen is produced to the surface via the horizontal well.
Bitumen production to surface may be accomplished via a number of known artificial lift methods. FIGURE 1 illustrates a commonly used sucker rod surface pumping unit 40, which may be emplDyed to pump to the surface the bi~umen which has drained into the horizontal well.
FIGURE 2 illustrates the case of multiple vertical wells 212, 213, and 214 being used in conjunction with one ; horizontal well 210. The different bottom hole cavities 222~
223, and 224 associated with the respective vertical wells will each probably have different volumes of native reservoir sand separating their respective bo~mdaries from horizontal well 210. These differing volumes of undisturb0d sand offer differing resistances to breakdown by fluid pressure in the horizontal well.
Fluid is injected in horizontal well 210 and the vertical well with the weakest resistance to hydraulic communication with the horizontal well, say for example vertical 3~
well 212, will begin to flow first. This first-flowing vertical well is then allowed to flow until a satisfactory in-situ communication path 232 is established. Once satisfactory in-situ communication is established, the vert;cal well is 5 shut-in. The fluid pressure in the horizontal well is then increased gradually until the occurence of fluid breakthrough to a second vertical well, for example 213. ~fter satisfactory flow is established, this second vertical well is shut-in. The sequence is repeated until all vertical wells have been made to 10 achieve hydraulic communication with the horizontal w~ll.
Subsequently, if desired, the resistance to communication between the horizontal well and each vertical well will be fine-tuned to make the resistance for each vertical well equal to that for each of the other vertical wells. This can be done by selectively flowing and shutting-in the vertical wells to achieve a hydraulically balanced system.
;
Once hydraulic balance is established, the wells are ready for production enhancement operations. Such operations may include injectlng steam or another fluid through the vertical injection wells to stimulate gravity drainage of bitumen in the reservoir toward the production well via the previously established communication paths, 232, 233, and 234.
Bitumen may then be produced from the horizontal well utilizing techniques well known in the art.
q~
; FIGURE 3 illustrates a field arrangement comprising several injection wells 312-317 in combination with two horizontal wells 310 and 311 where the vertical wells were drilled from one common surface drilling pad 300. The arrangement illustrated in FIGURE 3 may be part of a larger field pattern including other drilling pads.
Cavities 322-327 are excavated thru injection wells 312-317 at points proximate the location of a horizontal well. While injection wells 312-317 are open to production, a fluid is injected in each horiæontal well at a pressure below fracture pressure. As in the earlier example, the injection well with the weakest resistance to hydraulic communication with its associated horizontal well will begi~ to flow first. Upon reaching satisfactory communication, this well will be shut-in.
The fluid pressure in the horizontal well will then be increased until satisfactory communication is obtained in a second well.
The procedure is then repeated until communication is established between each horizontal well and its associated injection wells. After hydraulic communication is fine-tuned by selectively flowlng and shutting-in the vertical wel]s, the field is ready for gravity drainage production operations.
Steam or other fluid is injected through the injection wells to initiate bitumen flow by gravity drainage towards the horizontal wells, where the bitumen is produced to surface.
FIGURES 4-69 illustrate different configurations which may be encountered during field operations.
FIGURE 4, illustrates the situation where injection ~-well 412 is directly above horizontal well 410. A cavity 422 is excavated at the bottom hole location of injection well 412 to form co~nunication path 432.
In FIGURE 5, horizontal well 510 is located to the side of injection well 512. Cavity 522 is excavated at a point where injection well 512 is proximate the horizontal well in order to form communication path 532.
FIGURE 6 illustrates the situation where horizontal well 610 is located to the side of injection well 612 near the injection well's bottom hole locations. Cavity 622 is excavated at the bottom hole location of injection well 612 in order to create communication path 632.
Changes and modifications to the specifically described embodiments can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the claims which follow.
Claims (19)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for establishing communication between an injection well and a production well penetrating tar sand deposits, including the steps of:
(a) excavating a cavity at a position at which said injection well is proximate to said production well;
(b) opening said injection well to production; and (c) injecting a fluid through said production well into said tar sand deposit at a pressure less than fracture pressure and allowing the part of the subterranean formation intermediate said production well and said cavity to give way, creating a highly permeable zone between said injection and production wells.
(a) excavating a cavity at a position at which said injection well is proximate to said production well;
(b) opening said injection well to production; and (c) injecting a fluid through said production well into said tar sand deposit at a pressure less than fracture pressure and allowing the part of the subterranean formation intermediate said production well and said cavity to give way, creating a highly permeable zone between said injection and production wells.
2. The method of claim 1 wherein said injected fluid is water.
3. The method of claim 1, further including the step of:
(d) following the creation of said highly permeable zone, injecting a hot fluid through said injection well to encourage gravity drainage of bitumen toward said production well.
(d) following the creation of said highly permeable zone, injecting a hot fluid through said injection well to encourage gravity drainage of bitumen toward said production well.
4. The method of claim 3, further including the step of:
(e) recovering bitumen via said production well.
(e) recovering bitumen via said production well.
5. The method of claim 1 wherein said production well is directionally drilled so as to have a substantially horizontal orientation with respect to the earth's surface.
S. The method of claim 1 wherein said production well is extended substantially horizontally through said deposit and said injection well extends substantially vertically into said deposit and to a point near the horizontal portion of said production well.
7. The method of claim 1 wherein said excavation step is accomplished by circulating mud through said injection well.
8. The method of claim 1 wherein said fluid contains additives.
9. A method for establishing communication between a substantially horizontal well and a substantially vertical well penetrating a tar sand deposit, including the steps of:
(a) excavating a cavity at a position at which said vertical well is proximate to said horizontal well;
(b) opening said vertical well to production; and (c) injecting a fluid in said horizontal well at a pressure less than fracture pressure and allowing the part of the subterranean formation intermediate said horizontal well and said proximate cavity to give way, forming a communication path between said vertical well and said horizontal well.
(a) excavating a cavity at a position at which said vertical well is proximate to said horizontal well;
(b) opening said vertical well to production; and (c) injecting a fluid in said horizontal well at a pressure less than fracture pressure and allowing the part of the subterranean formation intermediate said horizontal well and said proximate cavity to give way, forming a communication path between said vertical well and said horizontal well.
10. The method of claim 9, further including the step of:
(d) following the formation of said communication path, injecting a fluid into said tar sand deposit through said vertical well to encourage gravity drainage of bitumen toward said horizontal well.
(d) following the formation of said communication path, injecting a fluid into said tar sand deposit through said vertical well to encourage gravity drainage of bitumen toward said horizontal well.
11. The method of claim 9, further including the step (e) recovering bitumen via said horizontal well.
12. The method of claim 9 wherein said fluid contains additives.
13. A method for establishing communication between a first well and a plurality of second wells penetrating a subterranean formation including tar sand deposits, including the steps of:
(a) excavating a cavity at locations where each second well is proximate to said first well;
(b) opening said second wells to production;
(c) injecting a fluid in said first well at pressures less than fracture pressure for said formation;:
(d) obtaining flow in at least one of said second wells and then shutting-in said second well while continuing to inject fluid in said first well until flow is obtained in another second well; and (e) repeating step (d) until flow has been obtained in a desirable number of second wells, thereby indicating that the subterranean formations adjacent to said first well and proximate said desirable number of second wells have given way, creating communication paths between said first well and said desirable number of second wells.
(a) excavating a cavity at locations where each second well is proximate to said first well;
(b) opening said second wells to production;
(c) injecting a fluid in said first well at pressures less than fracture pressure for said formation;:
(d) obtaining flow in at least one of said second wells and then shutting-in said second well while continuing to inject fluid in said first well until flow is obtained in another second well; and (e) repeating step (d) until flow has been obtained in a desirable number of second wells, thereby indicating that the subterranean formations adjacent to said first well and proximate said desirable number of second wells have given way, creating communication paths between said first well and said desirable number of second wells.
14. The method of claim 13, further including the step of:
(f) selectively shutting-in said second wells while injecting fluid in said first well to equalize the flow of fluid flowing through said second wells.
(f) selectively shutting-in said second wells while injecting fluid in said first well to equalize the flow of fluid flowing through said second wells.
15. The method of claim 13, further including the step of:
(g) injecting hot fluid into the formation through selected second wells to encourage the flow of bitumen toward said first well for subsequent bitumen production to surface via said first well.
(g) injecting hot fluid into the formation through selected second wells to encourage the flow of bitumen toward said first well for subsequent bitumen production to surface via said first well.
16. A method for recovering bitumen from a tar sand formation containing bitumen which comprises:
(a) drilling at least one substantially vertical well and at least one substantially horizontal well into said tar sand formation;
(b) excavating a cavity around the base of said substantially vertical well and opening said substantially vertical well to production;
(c) injecting a fluid in said substantially horizontal well at a pressure less than fracture pressure to cause the part of the subterranean formation intermediate said substantially horizontal well and said proximate cavity to give way, creating a communication path between said wells;
(d) injecting hot fluid into the formation, so as to increase the temperature and reduce the viscosity of said bitumen contained in said formation; and (e) allowing gravity drainage of bitumen to said substantially horizontal well and producing bitumen from said formation through said substantially horizontal well.
(a) drilling at least one substantially vertical well and at least one substantially horizontal well into said tar sand formation;
(b) excavating a cavity around the base of said substantially vertical well and opening said substantially vertical well to production;
(c) injecting a fluid in said substantially horizontal well at a pressure less than fracture pressure to cause the part of the subterranean formation intermediate said substantially horizontal well and said proximate cavity to give way, creating a communication path between said wells;
(d) injecting hot fluid into the formation, so as to increase the temperature and reduce the viscosity of said bitumen contained in said formation; and (e) allowing gravity drainage of bitumen to said substantially horizontal well and producing bitumen from said formation through said substantially horizontal well.
17. The method of claim 16 wherein there are two substantially vertical wells, one for injection of hot fluid and one for production of bitumen.
18. The method of claim 16 wherein said hot fluid comprises water.
19. A method for recovering bitumen from a tar sand formation, comprising the steps of:
(a) drilling a first well into said tar sand formation;
(b) drilling a second well into said tar sand formation, said second well being drilled to reach a position proximate said first well;
(c) establishing a cavity surrounding that portion of said second well proximate said first well (d) perforating said first well at a position proximate said second well to establish a first perforated zone in said first well; and (e) injecting fluid from said first well through said first perforated zone and into said second well via said cavity, said injection occurring at a pressure below the fracture pressure of said tar sand formation, whereby that portion of said tar sand formation intermediate said first perforated zone and said cavity gives way, establishing a zone of enhanced permeability intermediate said first and second wells.
(a) drilling a first well into said tar sand formation;
(b) drilling a second well into said tar sand formation, said second well being drilled to reach a position proximate said first well;
(c) establishing a cavity surrounding that portion of said second well proximate said first well (d) perforating said first well at a position proximate said second well to establish a first perforated zone in said first well; and (e) injecting fluid from said first well through said first perforated zone and into said second well via said cavity, said injection occurring at a pressure below the fracture pressure of said tar sand formation, whereby that portion of said tar sand formation intermediate said first perforated zone and said cavity gives way, establishing a zone of enhanced permeability intermediate said first and second wells.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000533056A CA1289057C (en) | 1987-03-26 | 1987-03-26 | Method for achieving communication between injection and production wells in tar sand deposits |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000533056A CA1289057C (en) | 1987-03-26 | 1987-03-26 | Method for achieving communication between injection and production wells in tar sand deposits |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1289057C true CA1289057C (en) | 1991-09-17 |
Family
ID=4135287
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000533056A Expired - Lifetime CA1289057C (en) | 1987-03-26 | 1987-03-26 | Method for achieving communication between injection and production wells in tar sand deposits |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1289057C (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8127865B2 (en) | 2006-04-21 | 2012-03-06 | Osum Oil Sands Corp. | Method of drilling from a shaft for underground recovery of hydrocarbons |
| US8287050B2 (en) | 2005-07-18 | 2012-10-16 | Osum Oil Sands Corp. | Method of increasing reservoir permeability |
| US8313152B2 (en) | 2006-11-22 | 2012-11-20 | Osum Oil Sands Corp. | Recovery of bitumen by hydraulic excavation |
| US10012064B2 (en) | 2015-04-09 | 2018-07-03 | Highlands Natural Resources, Plc | Gas diverter for well and reservoir stimulation |
| CN109653717A (en) * | 2019-01-23 | 2019-04-19 | 中国石油化工股份有限公司 | Combination, which is handled up, after individual well steam stimulation wells selects well decision-making technique |
| US10344204B2 (en) | 2015-04-09 | 2019-07-09 | Diversion Technologies, LLC | Gas diverter for well and reservoir stimulation |
| CN111764871A (en) * | 2020-07-08 | 2020-10-13 | 广州海洋地质调查局 | Natural gas hydrate reservoir direct-increasing horizontal mining method |
| US10982520B2 (en) | 2016-04-27 | 2021-04-20 | Highland Natural Resources, PLC | Gas diverter for well and reservoir stimulation |
| CN114075964A (en) * | 2020-08-11 | 2022-02-22 | 中国石油天然气股份有限公司 | Well pattern system and construction process thereof |
-
1987
- 1987-03-26 CA CA000533056A patent/CA1289057C/en not_active Expired - Lifetime
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8287050B2 (en) | 2005-07-18 | 2012-10-16 | Osum Oil Sands Corp. | Method of increasing reservoir permeability |
| US8127865B2 (en) | 2006-04-21 | 2012-03-06 | Osum Oil Sands Corp. | Method of drilling from a shaft for underground recovery of hydrocarbons |
| US8313152B2 (en) | 2006-11-22 | 2012-11-20 | Osum Oil Sands Corp. | Recovery of bitumen by hydraulic excavation |
| 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 |
| US10385257B2 (en) | 2015-04-09 | 2019-08-20 | Highands Natural Resources, PLC | 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 |
| US10982520B2 (en) | 2016-04-27 | 2021-04-20 | Highland Natural Resources, PLC | Gas diverter for well and reservoir stimulation |
| CN109653717A (en) * | 2019-01-23 | 2019-04-19 | 中国石油化工股份有限公司 | Combination, which is handled up, after individual well steam stimulation wells selects well decision-making technique |
| CN111764871A (en) * | 2020-07-08 | 2020-10-13 | 广州海洋地质调查局 | Natural gas hydrate reservoir direct-increasing horizontal mining method |
| CN114075964A (en) * | 2020-08-11 | 2022-02-22 | 中国石油天然气股份有限公司 | Well pattern system and construction process thereof |
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