CA2961312C

CA2961312C - Horizontal fractures in various combinations of infill wells, injection wells, and production wells

Info

Publication number: CA2961312C
Application number: CA2961312A
Authority: CA
Inventors: Mazda Irani; Robert Wayne King
Original assignee: Suncor Energy Inc
Current assignee: Suncor Energy Inc
Priority date: 2017-03-16
Filing date: 2017-03-16
Publication date: 2020-06-16
Anticipated expiration: 2037-03-16
Also published as: CA2961312A1

Abstract

Methods and systems are provided for recovering hydrocarbons from a hydrocarbon-bearing formation. The methods and systems include deliberately initiating fractures from the injection well along a generally horizontal plane from the injection well after fluid communication has been developed between the injection well and the production well. Production wells can be multilateral production wells. Horizontal fractures can also be deliberately initiated from infill wells.

Description

HORIZONTAL FRACTURES IN VARIOUS COMBINATIONS OF INFILL WELLS, INJECTION WELLS, AND PRODUCTION WELLS
TECHNICAL FIELD
[0001] The technical field relates to recovery of hydrocarbons from hydrocarbon formations.
BACKGROUND

[0002] Bitumen or heavy oil is abundant in different parts of the world, including Canada, the United States, Venezuela, and Brazil. However, the oil is highly viscous at reservoir temperatures and does not flow readily. Therefore, bitumen cannot be produced by conventional methods. In a number of cases, the heavy oil is thermally treated to reduce the viscosity and this makes it flow more easily.

[0003] Currently, the most common thermal-recovery processes are steam-based technologies, such as steam-assisted gravity drainage (SAGD) and cyclic-steam stimulation (CSS). In these processes, bitumen reservoirs are heated by steam injection; the bitumen is brought to the surface and later diluted with condensates for pipeline transportation.

[0004] Solvent injection can be used to enhance the performance of SAGD and CSS by introducing hydrocarbon solvent additives to the injected steam. The operating conditions for the solvent co-injection process are similar to SAGD.

[0005] During the start-up phase of a typical SAGD operation, the hydrocarbon-bearing formation is heated by injecting steam into the injection well and/or the production well.
Through convection and conductive heating, the steam reduces the viscosity of the hydrocarbons in the hydrocarbon-bearing formation to establish fluid communication between in the injection well and the production well. The start-up phase of a SAGD
operation would be maintained until the hydrocarbons in the region of the formation between the injection well and the production well become mobile and there is fluid communication between the two wells.

[0006] In addition, some hydrocarbon-bearing formations, including formations having inclined heterolithic stratification (IHS), contain structural baffles which prevent steam chambers from being formed in the desired size and shape.

[0007] While various attempts have been made to enhance hydrocarbon recovery and to reduce the length of the SAGD start-up process, there still exists a need for improved methods and solutions for recovering hydrocarbons from a hydrocarbon-bearing formation.
SUMMARY
100081 In general, the present specification describes methods and systems to produce hydrocarbons from a hydrocarbon-bearing formation.
[0009] In one implementation, there is provided a method for recovering hydrocarbons from a hydrocarbon-bearing reservoir. The method includes: achieving fluid communication between an injection well and a production well in a well pair formed in the reservoir, wherein the injection well injects a mobilizing fluid and the production well produces a production fluid;
deliberately initiating a fracture in the reservoir, the fracture extending from a horizontal portion of the injection well along a generally horizontal plane relative to the horizontal portion of the injection well; and producing hydrocarbons included in the production fluid from the hydrocarbon-bearing reservoir through a portion of the production well from a production chamber induced in the reservoir by the mobilizing fluid, wherein the volume of the production chamber is increased by the fracture.
[0010] In some aspects of the method, the production well includes a multilateral production well. In some aspects of the method, the method includes the additional steps of: providing an infill well in the hydrocarbon-bearing reservoir in proximity to the injection well and the production well; deliberately initiating an infill well fracture, the infill well fracture extending from a horizontal portion of the infill well along a generally horizontal plane relative to the horizontal portion of the infill well; and producing hydrocarbons included in the production fluid from the hydrocarbon-bearing reservoir through a portion of the infill well from the production chamber.
100111 In some aspects of the methods, the injection well is located at a position of the reservoir with a vertical overburden stress greater than a horizontal stress and the methods include the step of increasing the horizontal stress at the position such that it is greater than the vertical overburden stress.
[0012] In some aspects of the methods, the step of increasing the horizontal stress includes injecting the mobilizing fluid at a pressure at or near the reservoir's maximum operating pressure and at a high temperature.
100131 In some aspects of the methods, the position is about 300 meters below a topmost surface of the reservoir. In some aspects of the methods, the mobilizing fluid includes steam. In some aspects of the methods, the mobilizing fluid is injected at a rate of about 400 tonnes/day.
[0014] In another implementation, there is provided a method for recovering hydrocarbons from a hydrocarbon-bearing reservoir. The method includes: achieving fluid communication between a first and a second injection well and a production well in well pairs formed in the reservoir, wherein the first and second injection wells inject a mobilizing fluid and the production well produces a production fluid; deliberately initiating a first fracture in the reservoir, the first fracture extending from a horizontal portion of the first injection well along a first generally horizontal plane relative to the horizontal portion of the first injection well;
deliberately initiating a second fracture in the reservoir, the second fracture extending from a horizontal portion of the second injection well along a second generally horizontal plane relative to the horizontal portion of the second injection well; and producing hydrocarbons included in the production fluid from the hydrocarbon-bearing reservoir through a portion of the production well from production chambers induced in the reservoir by the mobilizing fluid, wherein the volume of the production chambers are increased by the first and second fractures.
100151 In some aspects of the methods, the production well includes a multilateral production well. In some aspects of the methods, the production well is heated with an electrical heater, by RF, or other heating methods without steam.
[00161 In some aspects of the methods, the first injection well is laterally offset from the second injection well. In some aspects of the methods, the production well is laterally offset from the first production well or the second production well. In some aspects of the methods, the lateral offset avoids an inclined heterolithic stratification (IHS) baffle in the hydrocarbon-bearing reservoir. In some aspects of the methods, the production well continues to be heated after fluid communication is achieved between the injection well and the production well.
[0017] In some aspects of the methods, initiating the fracture includes injecting a high pressure fluid. In some aspects of the methods, the fluid is steam. In some aspects of the methods, the mobilizing fluid includes solvent without steam. In some aspects of the methods, the mobilizing fluid includes solvent co-injected with steam. In some aspects of the methods, the mobilizing fluid includes steam. In some aspects of the methods, the methods include recovering the hydrocarbons. In some aspects of the methods, producing the hydrocarbons includes draining the hydrocarbons by gravity into the production well. In some aspects of the methods, producing the hydrocarbons includes operating a steam assisted in-situ hydrocarbon recovery process. In some aspects of the methods, the steam assisted in-situ hydrocarbon recovery process includes a steam assisted gravity drainage system.
[0018] In some aspects of the methods, producing the hydrocarbons includes using at least one of electrical heating, electromagnetic heating, radio frequency heating, solvent injection, carbon dioxide flooding, non-condensable gas injection, flue gas flooding, surfactants injection, alkaline chemicals injection, and microbial enhanced recovery.
100191 In some aspects of the methods, the first or the second injection well is located at a position of the reservoir with a vertical overburden stress greater than a horizontal stress and includes the step of increasing the horizontal stress at the position such that it is greater than the vertical overburden stress.
100201 In some aspects of the methods, the step of increasing the horizontal stress includes injecting the mobilizing fluid at a pressure at or near the reservoir's maximum operating pressure and at a high temperature.
100211 In another implementation, there is provided a method for recovering bitumen from a bitumen-bearing reservoir. The method includes: achieving fluid communication between an injection well and a multilateral production well in a well pair formed in the reservoir, wherein the injection well injects a mobilizing fluid and the production well produces a production fluid;
deliberating initiating a fracture in the reservoir, the fracture extending from a horizontal portion of the injection well along a generally horizontal plane relative to the horizontal portion of the injection well; and producing the bitumen included in the production fluid from the bitumen-bearing reservoir through a portion of the multilateral production well from a production chamber induced in the reservoir by the mobilizing fluid, wherein the volume of the production chamber is increased by the fracture.
[0022] In another implementation, there is provided a method for recovering bitumen from a bitumen-bearing reservoir. The method includes: achieving fluid communication between an injection well and a multilateral production well in well pair formed in the reservoir, wherein the injection well injects a mobilizing fluid and the multilateral production well produces a production fluid; deliberately initiating a fracture extending from a horizontal portion of the injection well along a generally horizontal plane relative to the horizontal portion of the injection well; producing bitumen included in the production fluid from the bitumen-bearing reservoir through a portion of the multilateral production well from a production chamber induced in the reservoir by the mobilizing fluid, wherein the volume of the production chamber is increased by the fracture; providing the infill well in the hydrocarbon-bearing reservoir in proximity to the injection well and the production well; deliberately initiating an infill well fracture extending from a horizontal portion of an infill well along a further generally horizontal plane from the horizontal portion of the infill well, the infill well in proximity to the injection well and the multi-lateral production well; and producing bitumen included in the production fluid from the bitumen-bearing reservoir through a portion of the multilateral production well from an infill well production chamber induced in the reservoir by the mobilizing fluid.
[0023] In another implementation, there is provided a method for recovering bitumen from a bitumen-bearing reservoir. The method includes achieving fluid communication between a first injection well and a production well and a second injection well and the production well in well pairs formed in the reservoir, wherein the first injection well is spaced apart from the second injection well, the production well is located below the first and second injection wells, and the injection wells inject a mobilizing fluid and the production well produces a production fluid;
deliberately initiating a first fracture in the reservoir, the first fracture extending from a horizontal portion of the first injection well along a first generally horizontal plane relative to the horizontal portion of the first injection well; deliberately initiating a second fracture in the reservoir, the second fracture extending from a horizontal portion of the second injection well along a second generally horizontal plane relative to the horizontal portion of the second injection well; and producing the hydrocarbons included in the production fluid from the bitumen-bearing reservoir through a portion of the multilateral production well from production chambers induced in the reservoir by the mobilizing fluid, wherein the volume of each of the production chambers is increased by the fracture.
[0024] In another implementation, there is provided a method for recovering bitumen from a hydrocarbon-bearing reservoir. The method includes: achieving fluid communication between the injection well and the production well in a well pair formed in the reservoir, wherein the injection well injects steam, the production well produces a production fluid, and the injection well is at a position in the reservoir with a vertical overburden stress greater than a horizontal stress; injecting steam into the injection well at a pressure close to a maximum operation pressure of the reservoir and a high temperature to modify a stress regime at the position to increase the horizontal stress until it is greater than the vertical overburden at the position;
deliberately initiating a fracture in the reservoir, the fracture extending from a horizontal portion of the injection well along a generally horizontal plane relative to the horizontal portion of the injection well; and producing hydrocarbons included in the production fluid from the hydrocarbon-bearing reservoir through a portion of the production well from a production chamber induced in the reservoir by the mobilizing fluid, wherein the volume of the production chamber is increased by the fracture.
[0025] In another implementation, there is provided a system for recovering hydrocarbons from a hydrocarbon-bearing reservoir. The system includes: at least one injection well and at least one multilateral production well, the at least one injection well injects a mobilizing fluid; at least one fracture deliberately initiated in the reservoir, the at least one fracture extending from a horizontal portion of the at least one injection well along a generally horizontal plane relative to the horizontal portion of the at least one injection well and the at least one fracture initiated after fluid communication has been established between the at least one injection well and the at least one multilateral production well; and a production chamber induced by the mobilizing fluid, the production chamber having an increased volume due to the fracture.

100261 In some aspects of the systems, the system includes at least one infill well in the hydrocarbon-bearing reservoir in proximity to the at least one injection well and the at least one multilateral production well; and at least one infill well fracture, the at least one infill well fracture extending from a horizontal portion of the at least one infill well along a further generally horizontal plane relative to the horizontal portion of the at least one infill well.
100271 In another implementation, there is provided a system for recovering hydrocarbons from a hydrocarbon-bearing reservoir. The system includes: a first injection well and a second injection well in the hydrocarbon-bearing reservoir, the second injection well spaced apart from the first injection well, the first and second injection wells inject a mobilizing fluid; a multilateral production well, the multilateral production well having a horizontal portion located below the first injection well and the second injection well; at least one fracture deliberately initiated in the reservoir, the at least one fracture extending from a horizontal portion of each of the first injection well and the second injection well along a generally horizontal plane relative to the horizontal portions of the first injection well and the second injection well and the at least one fractures initiated after fluid communication has been established between each of the first and second injection wells and the multilateral production well; and at least one production chamber induced by the mobilizing fluid having an increased volume due to the at least one fracture.
100281 In some aspects of the systems, the system includes an electric heater for heating the production well. In some aspects of the systems, the first injection well is laterally offset from the second injection well. In some aspects of the systems, the production well is laterally offset from the first injection well or the second injection well. In some aspects of the systems, the lateral offset avoids an inclined heterolithic stratification (IHF) baffle in the hydrocarbon-bearing reservoir. In some aspects of the systems, the injection well is adapted for injecting a heated fluid or viscosity-reducing agent.
[0029] In some aspects of the systems, the heated fluid includes steam. In some aspects of the systems, the fractures are formed by injection of a high pressure fluid. In some aspects of the system, the high pressure fluid is steam.

[0030] In some aspects of the systems, the system includes production equipment for producing the hydrocarbons from the hydrocarbon-bearing formation through the production well. In some aspects of the systems, the production equipment includes a steam assisted gravity drainage system. In some aspects of the systems, the production equipment includes a cyclic steam stimulation system. In some aspects of the systems, the production equipment is configured to mobilize the hydrocarbons using at least one of electrical heating, electromagnetic heating, radio frequency heating, solvent injection, carbon dioxide flooding, non-condensable gas injection, flue gas flooding, surfactants injection, alkaline chemicals injection, and microbial enhanced recovery.
[0031] In some aspects of the systems, the multilateral production well includes a plurality of lateral production wells. In some aspects of the systems, the multilateral production well is forked.
[0032] In some aspects of the systems, the at least one fracture is formed after the reservoir's stress regime proximate the injection well has been modified. In some aspects of the systems, the stress regime is modified by increasing the horizontal stress such that it is greater than the vertical overburden stress. In some aspects of the methods, the stress regime is modified by injection of a high pressure fluid into the injection well. In some aspects of the methods, the fluid includes steam.
[0033] In another implementation, there is provided a system for recovering bitumen from a bitumen-bearing reservoir. The system includes: at least one injection well and at least one multilateral production well, the at least one injection well injects a mobilizing fluid; at least one fracture deliberately initiated in the reservoir, the at least one fracture extending from a horizontal portion of the at least one injection well along a generally horizontal plane relative to the horizontal portion of the at least one injection well and the at least one fracture initiated by injection of steam into the at least one injection well after fluid communication has been established between the at least one injection well and the at least one multilateral production well; and a production chamber induced by the mobilizing fluid, the production chamber having an increased volume due to the fracture.

8 [0034] The details of one or more implementations are set forth in the description below. Other features and advantages will be apparent from the specification and the claims.
BRIEF DESCRIPTION OF THE DRAWING
[0035] Features and advantages of embodiments of the present application will become apparent from the following detailed description and the appended drawing, in which:
[0036] FIGs. IA to 1C are schematic cross-sectional views of a hydrocarbon-bearing formation showing a typical configuration of a SAGD well pair in which FIG. 1A
illustrates the SAGD
well pair, FIG. 1B illustrates the heat affected zone around the SAGD well pair, and FIG. 1C
illustrates an exemplary steam chamber that is formed over time after fluid communication has been established between the SAGD well pair.
[0037] FIGs. 2A to 2C are schematic cross-sectional views of a hydrocarbon-bearing formation showing a SAGD configuration with horizontal fractures extending from the injection well in which FIG. 2A shows a SAGD well pair, FIG. 2B shows horizontal fractures in the hydrocarbon-bearing formation extending from the injection well, and FIG. 2C
shows the resulting steam chamber formed over time.
[00381 FIG. 3A is a schematic cross-sectional view of the steam chamber of FIG. 2C where the production well has a single wellbore and a top plan view of a portion of the production well.
[00391 FIG. 3B is a schematic cross-sectional view of the steam chamber of FIG. 2C where the production well is a multilateral production well and a top plan view of a portion of the multilateral production well.
[00401 FIG. 4A is a schematic cross-sectional view of a hydrocarbon-bearing formation having two injection wells, two production wells, two steam chambers, and an infill well.
[00411 FIG. 4B is a schematic cross-sectional view of the hydrocarbon-bearing formation of FIG. 4A showing horizontal fractures extending from the injection wells and the infill well.
[0042] FIGs. 5A to 5C are schematic cross-sectional views of a hydrocarbon-bearing formation having a SAGD well pair and baffles in which FIG. 5A illustrates the SAGD well pair, FIG. 5B

9 illustrates the heat affected zone around the SAGD well pair, and FIG. 5C
illustrates the resulting steam chamber as constrained by the baffles.
[0043] FIGs. 6A and 6B are cross-sectional views of a hydrocarbon-bearing formation having two injection wells laterally offset from each other, a heated production well, and horizontal fractures extending from the injection wells and through the clay baffle.
[0044] FIG. 6C is a cross-sectional view of the hydrocarbon-bearing formation of FIG. 6B
showing production of hydrocarbons through a production well having a single wellbore.
[0045] FIG. 6D is a cross-sectional view of the hydrocarbon-bearing formation of FIG. 6B
where the production well is a multilateral production well and a top plan view of a portion of the multilateral production well.
DETAILED DESCRIPTION
100461 The present description relates to methods and systems for recovering hydrocarbons from hydrocarbon-bearing formations. Generally, in these methods and systems, the hydrocarbon-bearing formation contains a SAGD well pair and fractures in the hydrocarbon-bearing formation are deliberately initiated from the injection well and the fractures extend along a generally horizontal plane from the injection well after fluid communication has been established between the injection well and the production well. Hydrocarbons can then be collected from the formation through the production well and recovered to surface.
[0047] Throughout this specification, numerous terms and expressions are used in accordance with their ordinary meanings. Provided below are definitions of some additional terms and expressions that are used in the description that follows.
[0048] A "formation" or "geological formation" is a fundamental unit of lithostratigraphic classification. A formation includes rock strata that have comparable lithologies, facies, or other similar properties. Formations can be defined on the basis of the thickness of the rock strata of which they consist, and the thickness of different formations can vary widely.
A given stratigraphic column can include a number of formations. In the oil sands area of Northeastern Alberta, for example, the stratigraphic column consists of the following major formations (from basement to surface): Pre-Cambrian (basement), Devonian carbonates, McMurray oil sands, Wabiskaw sands and mudstones, Clearwater shales, Grand Rapids sandstones, and Quaternary sediments.
[0049] The "McMurray formation" or "McMurray sands" is a stratigaphic unit of Early Cretaceous age in the Western Canada Sedimentary Basin of Northeastern Alberta. It lies unconformably on Pre-Cretaceous erosion surfaces that generally comprise Devonian limestone, which is mainly carbonate rock. The McMurray sands are largely unconsolidated and the sand grains that form the formation are mostly held together by very viscous crude oil. The McMurray formation holds most of the vast hydrocarbon resources of the Athabasca bituminous sand deposit.
[0050] "Reservoir" refers to a subsurface formation containing one or more natural accumulations of hydrocarbons, which are generally confined by relatively impermeable rock or other geological layers of materials, including subsurface formations that are primarily composed of a matrix of unconsolidated sand, with hydrocarbons occurring in the porous matrix.
[0051] "Hydrocarbons" refer to a combination of different hydrocarbons or a combination of various types of molecules that contain carbon atoms and attached hydrogen atoms.
Hydrocarbons include a large number of different molecules in gaseous, liquid, or solid phase having a wide range of molecular weights, and can include bitumen, heavy oil, lighter grades of oil, and natural gas. Elements (e.g., sulphur, nitrogen, oxygen), metals (e.g., iron, nickel, vanadium), and compounds (e.g., carbon dioxide, hydrogen sulphide) are sometimes present in the form of impurities in a desired hydrocarbon mixture.
[0052] "Fracturing" includes a process for structurally degrading a geological formation around a wellbore by applying thermal and/or mechanical stress and includes processes that result in fractures being present in the hydrocarbon-bearing formation, especially in formations having soft rocks and loose sedimentary material such as the McMurray formation. Such structural degradation generally enhances the permeability of the formation to fluids.
Examples of hydraulic fracturing for use in the present methods and systems include, without limitation, hydraulic fracturing and acid fracturing.
[00531 "Hydraulic fracturing" refers to a method of using pump rate and hydraulic pressure of a hydraulic fracturing fluid, which can be a liquid or gas or a combination thereof, to fracture or crack a subterranean formation, thereby creating relatively large flow channels through which hydrocarbons can move into a well.
[0054] "Proppant" or "propping agent" refers to sized particles mixed with fracturing fluid to hold fractures open after a hydraulic fracturing treatment. In addition to naturally occurring sand grains, man-made or specially engineered proppants, such as resin-coated sand and ceramic beads, can also be used. Proppant materials are carefully sorted for size and sphericity to provide an efficient conduit for production of fluid from a reservoir to a wellbore.
[0055] The term "drilling" refers to the creation of a borehole in a formation by rotating a drill bit and simultaneously applying an axial load to the bit.
[00561 An "injection well" includes a well into which a fluid is injected into a formation.
[00571 A "production well" or "producer" includes any well or wellbore from which hydrocarbons can be produced, regardless of its configuration or arrangement.
The production well can be configured vertically, horizontally, or at any angle from vertical to horizontal or beyond horizontal, in any portion thereof [0058] "Bitumen" and "heavy oil" are normally distinguished from other petroleums based on their relative densities and/or viscosities, which often depend on context.
Commonly-accepted definitions classify "heavy oil" as petroleum (the density of which is between 920 and 1,000 kg/m3) and "bitumen" as oil produced from bituminous sand formations (the density of which is greater than 1,000 kg/m3). For purposes of this specification, the terms "bitumen" and "heavy oil" are used interchangeably such that each one includes the other. For example, where the term "bitumen" is used alone, it includes within its scope "heavy oil".
[0059] The "natural reservoir temperature" or "reservoir temperature" is an ambient temperature of a cold or unheated reservoir.

[0060] The reference to "horizontal" includes substantially horizontal and generally horizontal.
[0061] "Infill region" or "bypassed region" refers to an area formed between at least two production wells in a reservoir, in which a significant quantity of hydrocarbons, in the form of bitumen, heavy oil, or otherwise, remains unrecovered by normal recovery operations.
[0062] A "chamber" within a reservoir or formation includes a region that is in fluid communication with a particular well or wells, such as an injection or production well. For example, in a SAGD process, a steam chamber is the region of the reservoir in fluid communication with a steam injection well; this is also the region that is subject to depletion, primarily by gravity drainage, into a production well. Thus, a chamber can be a depleted region.
100631 Specific examples of the present methods and systems are described below with reference to the drawings. Details are provided for the purpose of illustration, and the methods and systems can be practiced without some or all of the features discussed herein. For clarity, technical materials that are known in the fields relevant to the present methods and systems are not discussed in detail.
100641 Some of the drawings and implementations described herein refer to a SAGD operation.
However, it should be understood that other configurations can be used that may or may not involve the use of steam. For example, an injection well can be used to inject a solvent or other chemical that can be used to modify the viscosity of the hydrocarbons in the formation, so that the hydrocarbons can be produced by gravity to flow to the production well. In other configurations, a source of thermal energy other than steam, such as in-situ combustion, electric heat, radio frequency energy, and the like, or a combination of any of the foregoing, can be used to heat the formation and again modify the viscosity of the hydrocarbons to cause production of hydrocarbons by gravity drainage. The implementations described below in the context of SAGD are not intended to be limited to SAGD applications.
100651 FIGs. IA to 1C illustrates the basic principles of a SAGD operation in a hydrocarbon-bearing formation (10). Referring to FIG. 1A, an injection well (20) is drilled into the formation and positioned above a production well (30) in the same geological formation

(10). In one implementation, the injection well (20) includes a horizontal portion that is positioned about 5 metres above a horizontal portion of the production well (30). In the illustrated implementation, injection well (20) and production well (30) are drilled vertically into the hydrocarbon-bearing formation and they become oriented horizontal.
[0066] Referring to FIG. 1B, during the start-up phase of the SAGD operation, steam is injected into the injection well (20) and the production well (30) to heat the formation surrounding the injection well (20) to form a heat affected zone (34) and to establish fluid communication between the injection well (20) and the production well (30).
The steam reduces the viscosity of the hydrocarbons in the hydrocarbon-bearing formation (10).
100671 At the end of the start-up phase, fluid communication is achieved between the injection well (20) and the production well (30), and a production fluid (50) (e.g., including mobilized hydrocarbons and hot water, such as hot water from condensed steam) is collected in the production well (30) with the assistance of gravity and produced to surface.
The steam chamber (40) develops vertically to reach the cap rock and then expands horizontally.
Over time, a steam chamber (40) will form above the SAGD well pair. FIG. 1C illustrates one implementation of the steam chamber (40) once it has been fully formed. In the illustrated implementation, the steam injection well (20) and the production well (30) are both located within the steam chamber (40). There is a steam/liquid interface between the steam injection well (20) and the production well (30). In some implementations, the production well (30) is not in direct contact with gaseous steam. In such implementations, the liquid below the steam/liquid interface is a mixture of hydrocarbons and condensed steam (hot water). The gas/liquid interface between the injection well (20) and the production well (30) is also present in other implementations that involve the injection of a gaseous solvent, such as butane and the like, a gaseous chemical, such as carbon dioxide and the like, or air for combustion.
100681 While the SAGD process allows hydrocarbons to be extracted from hydrocarbon-bearing formations, the start-up period of a SAGD operation can be 6 months or longer because the formation has to be heated to a sufficient degree before fluid communication can be established between the injection well and the production well and the viscosity of the hydrocarbons have been sufficiently modified. During the start-up period, hydrocarbons generally are not produced from the hydrocarbon-bearing formation and steam is to be circulated to heat the interwell region between the injection well (20) and the production well (30) and areas of the formation (10) around the SAGD well pair.
100691 FIGs. 2A-2C illustrates an implementation of the method and system for recovering hydrocarbons using SAGD. As with FIG. 1A, an injection well (20) and a production well (30) are drilled into the hydrocarbon-bearing formation (10). As with the typical SAGD operation, steam is circulated in both the injection well (20) and the production well (30) to heat the hydrocarbon-bearing formation (10), and more particularly the interwell region between the injection well (20) and the production well (30).
[0070] As illustrated in FIG. 2B, this implementation includes the step of deliberately initiating a fracture (22) in the hydrocarbon-bearing formation (10) along a horizontal plane from the injection well (20). Methods for initiating fractures in the hydrocarbon-bearing formation (10) from the injection well (20) are known in the art. The orientation of the fracture depends on the stress characteristics and the composition of the hydrocarbon-bearing formation (10). A fracture will occur in a plane perpendicular to the direction of the minimum stress. In shallow reservoirs, horizontal fractures can be formed by hydraulic fracturing processes where the horizontal stress is greater than the vertical overburden stress.
[0071] Based on the stress characteristics of the formation (10) (which can change depending on the temperature of the portion of the formation being heated) and the composition of the formation (10), the person skilled in the art can select the appropriate method for inducing fractures in the formation (10) from the injection wells (20). The person skilled in the art will also consider the depth of the SAGD well pair (since stress orientation is a function of depth) when determining the method for inducing the horizontal fractures (22). In one implementation, the horizontal portion of the injection well (20) from which fractures (22) are initiated is located in reservoirs shallower than 150 metres below the surface of formation (10) metres.
[0072] In deeper formations for which initial mini-frac results suggested vertical fractures would be formed from the injection well (20), the stress regime of formation (10) can be modified (called "stress distribution") due to injection pressure and thermal expansion (i.e., heaving) resulting from injection of high temperature steam (i.e., jacking effect in the context of SAGD operation). Modifying the stress regime of the formation (10) to increase the horizontal stress until it is greater than the vertical overburden stress allows horizontal fractures (22) to be initiated from the injection well (20) instead of vertical fractures, since fractures (22) will occur in the plane perpendicular to the direction of the minimum stress.
[0073] In one implementation, the method used to create horizontal fractures (22) in the formation (10) in SAGD operation is to inject steam at a pressure close to the maximum operation pressure (MOP). The pressure and temperature of the injected steam modify the stress regime of formation (10) and lowers the fracture gradient of formation (10) around the injection well (20), allowing horizontal fractures (22) to be formed. The horizontal fractures (22) will be created at lower pressures than that of MOP at the level of the injection well (20). This method can be used in deeper reservoirs which are at the boundary of changing the direction of the fracture from vertical to horizontal. The fractures propagating from the injection well (20) horizontally can help the steam chamber (40) propagate horizontally and ramp up the completion of the start-up phase. The resulting steam chamber will have a larger volume as a result.
[0074] The size of the fractures (22) can depend on a number of factors, including the nature of the fracturing fluid, the amount of fluid returned to surface after injection, the injection rate of the fracturing fluid, the pressure at which the fluid is driven into the formation (10), and the flow rate of the fracturing fluid.
[0075] In the implementation shown in FIGs. 2A to 2C, steam is used to initiate the horizontal fractures (22) in the hydrocarbon-bearing formation (10). In one implementation, the steam is injected into the injection well (20) at a pressure close to the MOP of the reservoir, which is highly dependent on stress regime and depth of the reservoir. Steam injection rates highly depend on injectivity of the reservoir. In one implementation, the steam injection rate is about 400 tonnes/day. In some implementations, the steam injection rate is less than 400 tonnes/day.
[0076] In one implementation, cold water is used as to initiate the horizontal fractures (22). In some implementations, nitrogen fracking can be used to initiate the horizontal fractures (22). In some implementations, other fracking fluids known to a person skilled in the art are used to initiate the horizontal fractures (22). In some implementations, proppants can be included in the fracturing fluid.
100771 In one implementation, at least one of the horizontal fractures (22), as measured from the injection well (10), has a length of about 10 metres. In some implementations, the length of the horizontal fractures (22) as measured from the injection well (10) is less than 10 metres.
100781 In the implementation illustrated in FIGs. 2A to 2C, the heat affected zone (34) and the resulting steam chamber (40) are larger when compared to the steam chamber of SAGD
operations without the horizontal fractures (22) in the hydrocarbon-bearing formation (10) (as shown in FIG. IC). The larger steam chambers provide fluid communication between the injection well (20) and the production well (30) over a greater lateral distance, and can increase the overall width (including the volume of the steam chamber), thereby increasing the volume of hydrocarbon recovered from the formation. Accordingly, greater production of production fluid (50), including hydrocarbons, can be achieved by mobilizing a larger amount of hydrocarbons in the hydrocarbon-bearing formation (10) and providing better an increased area of fluid communication between the injection well (20) and the production well (30).
[0079] After horizontal fractures (22) are introduced into formation (10), as a result of the increased area of fluid communication and the larger steam chambers that form, in some implementations, after horizontal fractures (22) are formed, bitumen production rates from the production well (30) at the ramp-up phase can be as high as the bitumen production rates from a formation (10) with a fully formed steam chamber (40) without horizontal fractures. In some implementations, after horizontal fractures (22) are formed, bitumen production rates from the production well (30) can be commensurate with that of a reservoir that has been in production for at least 2 years.
100801 In the implementation illustrated in FIGs. 2A to 2C, the production well (30) has a single bore. In another implementation, as illustrated in FIGs. 3A and 3B, the production well (30) is a multilateral production well (32).
[0081] FIG. 3A includes a cross-sectional view of the hydrocarbon-bearing reservoir as illustrated in FIG. 2C and a top plan view of production well (30). In this implementation, there is a risk of premature breakthrough of steam (38) from the injection well (20) into production well (30). Premature breakthrough of steam (38) is undesirable because it can stop production of the production fluid (50) from production well (30).
100821 To reduce the risk of premature breakthrough of steam (38), the implementation illustrated in FIG. 3B can be used. This implementation is substantially similar to that illustrated in FIG. 3A, except that the production well is a multilateral production well (32). Multilateral wells, including multilateral production wells, are well known to a person skilled in the art.
Multilateral production well (32) includes a plurality of multilateral injunctions (36) which provides for a plurality of lateral production wells (38). The use of a multilateral production well (32) further creates a longer production path and allow increased fluid communication between the multilateral production well (32) and the injection well (22).
[0083] In typical SAGD operations, the heels of production well (30) and injection well (20) can be quite close together. With steam temperature being higher at the heel, steam coning can occur at the heel of the production well (30), leading to premature steam breakthrough. The risk of premature breakthrough of steam (14) is limited when a multilateral production well (32) is used because the distances between the injection well (20) and the multilateral production well (32) and the lateral production wells (38) are varying, which can decrease the likelihood of steam coning.
100841 The drilling of multilateral wells, including multilateral production well, is known to a person skilled in the art. In the implementation illustrated in FIG. 3B, the multilateral production well (32) includes at least two lateral production wells (38) at each multilateral junction (36). In other implementations, the multilateral production well (32) can include more than two lateral production wells (38) at each multilateral junction (34). In one implementation, the lateral production wells (38) are substantially in the same plane as the multilateral production well (32). In some implementations, the multilateral production well (32) includes forked lateral production wells.
100851 Horizontal fractures in the hydrocarbon-bearing reservoir can also be used in improving the production of hydrocarbons from an infill well. In SAGD operations, steam chambers around each SAGD well expands with time and there can be unproduced hydrocarbons within the hydrocarbon-bearing formation, including in bypassed regions, that are not produced between adjacent SAGD well pairs. Infill wells can be used to access the unproduced hydrocarbons. Infill wells are typically a single well having a horizontal portion drilled at approximately the center-line between the two target adjacent SAGD well pairs.
100861 One implementation of the methods and systems to produce hydrocarbons using infill wells is illustrated in FIGs. 4A and 4B. Referring to FIG. 4A, two SAGD well pairs (injection well 20a and 20b) and production well (30a and 30b) are present in the hydrocarbon-bearing reservoir (10) prior to horizontal fractures being induced from the injection well. In this implementation, infill well (70) has a horizontal portion located at or near the middle of the bypassed region (16) that is between the two steam chambers (40a and 40b) formed around the two SAGD well pairs. In some implementations, infill well (70) is not located at the middle of the bypassed region.
100871 As shown in FIG. 4B, fracturing is deliberately initiated from each of the injection wells (20a and 20b) using techniques known to a person skilled in the art and as outlined above. The resulting fractures (22a and 22b) in the hydrocarbon-bearing formation (10) extend substantially in a horizontal plane from the injection wells (20a and 20b). Fracturing is also deliberately initiated from the infill well (70) using techniques known to a person skilled in the art and as outlined above. The resulting infill well fractures (72) in the hydrocarbon-bearing formation (10) extend substantially in a horizontal plane from the infill well (70). In this implementation, the horizontal fractures (22b) extend beyond the boundaries of steam chamber (40b) and into bypassed region (16) of the hydrocarbon-bearing formation (10) between the two adjacent SAGD well pairs. The steam (60) injected into the formation (10) through the injection wells (20a and 20b) and/or production wells (30a and 30b) mobilizes the hydrocarbons in bypassed region (16) and the mobilized hydrocarbons (in the form of production fluid (80)) is collected into the infill well (70) by gravity and is produced to surface. The amount of production fluid (80) recovered from the hydrocarbon-bearing formation (10) can, therefore, be higher when using the implementation shown in FIG. 4B, as compared to one where fractures are not initiated from the injection wells (20a and 20b) and the infill well (70).

100881 The implementation illustrated in FIG. 4B can also be implemented in hydrocarbon-bearing formation (10) having baffles and shale drapes between steam chambers formed around SAGD well-pairs. Initiating horizontal fractures in the hydrocarbon-bearing formation (10) will increase the amount of hydrocarbons extracted from the formation (10) by recovering hydrocarbons from bypassed region (16) that is otherwise not accessible due to presence of baffles, such as clay baffles and the like.
[0089] In this implementation, the infill well (70) has a single bore. In some implementations, the infill well (70) can be a multilateral infill well. In the implementation illustrated in FIG. 4B, one infill well is drilled into the hydrocarbon-bearing formation (10). In other implementations, more than one infill well is drilled into the hydrocarbon-bearing formation (10).
[0090] In one implementation, the infill well (70) is operated as a constant producer as part of the SAGD operation. In other implementations, the infill well (70) is operated in CSS.
[0091] Fractures deliberately initiated from injection wells and extending in the hydrocarbon-bearing formation from injection wells in a horizontal plane can also be used for production of hydrocarbons in hydrocarbon-bearing formations (10) that contain clay baffles or other baffles.
In one implementation, the hydrocarbon-bearing formation (10) includes inclined heterolithic stratification (IHS).
[0092] FIGs. 5A-5C illustrates a SAGD operation in a hydrocarbon-bearing formation (10) having baffles (100). In one implementation, baffles (100) include clay baffles and the like.
Similar to other SAGD operations (including, for example, as illustrated in FIG. 1A), referring to FIG. 5A, the hydrocarbon-bearing formation (10) includes an injection well (20) and a production well (30), which are positioned between two baffles (100).
Referring to FIG. 5B, as steam is circulated through the injection well (20) and the production well (30), the heat affected zone (34) is created within the hydrocarbon-bearing formation (10) around the SAGD
well pair. While the steam chamber is designed to have the shape and size of steam chamber (46), the baffles (100) restricts the size and shape of the actual steam chamber (44) =formed around the SAGD well pair. Baffles (100) can impede the steam from permeating into areas of formation (10) beyond the baffles (100). The smaller steam chamber (44) leads to less hydrocarbons being produced from hydrocarbon-bearing formation (10) and lower production rates from the SAGD operation.
100931 FIGs. 6A-6C illustrate an implementation of the systems and methods of hydrocarbon recovery that involves fractures in the formation (10) extending from the injection wells and the hydrocarbon-bearing formation (10) having baffles (100). In the illustrated implementation, two injection wells (20a and 20b) are drilled into the hydrocarbon-bearing formation (10). A
mobilizing fluid, such as steam, is circulated in injection wells (20a and 20b) to heat the hydrocarbon-bearing formation (10) to form heated zones (34a and 34b). In this implementation, the injection wells (20a and 20b) are laterally offset to avoid drilling into baffles (100). In other implementations, the injection wells (20a and 20b) are positioned in substantially the same horizontal plane.
100941 In this implementation, steam is not circulated within production well (30). Rather, the production well (30) is heated using other methods not using steam. In some implementations, the production well (30) is heated using an electrical heater, geothermal energy, electromagnetic energy, radio frequency based heating, or a combination of any of the foregoing. Heat affected zone (34c) is established around production well (30).
100951 After the heat affected zones (34a, 34b, and 34c) are established and fluid communication is established between the injection wells (20a and 20b) and production well (30), fractures (22a and 22b) are deliberately initiated from the injection wells (20a and 20b) and fractures (22a and 22b) extend along a generally horizontal plane from the injection wells (20a and 20b) in the formation (10). The horizontal fractures (22a and 22b) are initiated using the methods known to a person skilled in the art and as outlined above.
100961 The fractures (22a and 22b) extend across baffles (100) and allows steam to reach portions of the hydrocarbon-bearing formation (10) between baffles (100) that is otherwise stranded and not recoverable. Heating of these portions of the hydrocarbon-bearing formation (10) mobilizes the hydrocarbons and production fluid (80) between baffles (100) is collected in the production well (30) by gravity and produced to surface.
100971 In the implementation illustrated in FIG. 6C, the production well (30) has a single bore.

Production of hydrocarbons in the form of production fluid (80) can be increased by using a multilateral production well (32).
100981 FIG. 6D illustrates an alternative implementation of the methods and systems for recovering hydrocarbons from the hydrocarbon-bearing formation (10) of FIG. 6c in which the hydrocarbon-bearing formation (10) has a multilateral production well (32) having lateral production wells (38). In this implementation, multilateral production well (32) includes two lateral production well (38) at each multilateral junction (36). In other implementations, the multilateral production well (32) can include more than 2 lateral production wells (38) at each multilateral junction (34). In one implementation, the lateral production wells (38) are substantially in the same plane as the multilateral production well (32).
[0099] In the implementation illustrated in FIG. 6D, the horizontal fractures (22) can allow increased fluid communication between the injection wells (20a and 20b) and multilateral production well (32). Increased circulation of steam in hydrocarbon-bearing formation (10) through horizontal fractures (22) can also allow increased rate of growth of steam chambers (40a, 40b, and 40c). In addition, the boundaries of the steam chambers (40a, 40b, and 40c) can expand beyond the restrictions or baffles created by the baffles (100). The multilateral production well (32) and its lateral production wells (38) can collect additional production fluid from both of the steam chambers (40a, 40b, and 40c).
[00100] While baffles (100) are illustrated as being parallel to the injection and production wells in FIGs. 5A-6D, in some implementations, the injection and production wells are drilled perpendicular to the clay baffles and not parallel to the baffles.
1001011The configuration of injection wells and production wells can vary based on the characteristics of a given reservoir and a given adjacent location and the recovery process chosen. Each of the injection well and production well can be vertical, inclined, curved, horizontal, past horizontal, or at any angle between vertical and horizontal, partially or in its entirety, and can be positioned in various arrangements with respect to other wells, if any. For a given set of geological and operational parameters, the skilled person is able to devise suitable configurations, shapes, and arrangements of production wells in order to maximize recovery.

1001021In some implementations, the production well can be configured with an incline or can be curved. For example, a production well can have vertical, curved, and horizontal sections, as in typical SAGD well pairs, or can be arranged vertically or at an incline, as in a typical cyclic steam stimulation (CSS) process. In some implementations, at least a portion of the production well is oriented at an angle from vertical to horizontal or beyond horizontal, so as to collect the hydrocarbons from the hydrocarbon-bearing formation. In some implementations, at least a portion of the production well is positioned substantially horizontal.
[001031 In the implementations discussed in FIGs. 2A-6C, fracturing is initiated from the injection well and/or infill well to develop fractures along a generally horizontal plane in the hydrocarbon-bearing formation after completion of the start-up phase. In some implementations, the horizontal fractures can be initiated from the injection wells after production has commenced from the SAGD well pair. In some implementations, fracturing is initiated from the injection well and/or infill well when the ramp-up phase begins.
1001041ln the implementations discussed in FIGs. 2A-6C, fracturing is initiated after fluid communication has been established between the SAGD well pair. This permits the steam chamber to grow across the length of the horizontal fractures, as well as above the SAGD well pair and can increase the size of the resulting steam chamber and increase the production rate of bitumen from the formation (10). If fracturing is initiated too early during the start-up phase, additional steam may be needed to heat the interwell region sufficiently to achieve fluid communication between the SAGD well pair, as the steam would be distributed across the horizontal fractures as well.
[00105] Many techniques for mobilizing hydrocarbons are known to the skilled person, including injection of hot fluids (e.g., steam), injection of air for in-situ combustion, electrical-resistive heating, electromagnetic heating, injection of polymers for mobility control, injection of viscosity-reducing agents or solvents, microbial treatment, and other similar methods. These methods can be used with the methods and systems discussed herein to increase mobilization of the hydrocarbons.
[00106J While the implementations illustrated in FIGs. 2A-6D use one to two production wells and one to two injection wells, any number of production wells and injection wells can be used.
1001071 Although the implementations illustrated in FIGs. 2A-6D include fractures extending from injection wells and/or infill wells, fractures can also be initiated from one or more of the production wells located in the hydrocarbon bearing formation. Techniques used for initiating fractures from the injection wells and/or infill wells as described herein can be used for initiating fractures from the one or more production wells.
[00108] While a number of exemplary aspects and implementations have been discussed above, those skilled in the art will recognize certain modifications, permutations, additions, sub-combinations thereof.
[00109] Although the present specification has described particular embodiments and examples of the methods and treatments discussed herein, it will be apparent to persons skilled in the art that modifications can be made to the embodiments without departing from the scope of the appended claims.

Claims

1. A method for recovering hydrocarbons from an oil sands reservoir, comprising:
achieving fluid communication between an injection well and a production well in a well pair formed in the reservoir, wherein a horizontal portion of the production well is provided below a horizontal portion of the injection well and wherein the injection well injects a mobilizing fluid and the production well produces a production fluid;
deliberately initiating a fracture in the reservoir, the fracture extending from the horizontal portion of the injection well along a generally horizontal plane relative to the horizontal portion of the injection well; and producing hydrocarbons included in the production fluid from the reservoir through the horizontal portion of the production well from a production chamber induced in the reservoir by the mobilizing fluid, wherein the volume of the production chamber is increased by the fracture.

2. The method according to claim 1, wherein the production well comprises a multilateral production well.

3. The method according to claim 1, comprising the additional steps of:
providing an infill well in the reservoir in proximity to the injection well and the production well;
deliberately initiating an infill well fracture, the infill well fracture extending from a horizontal portion of the infill well along a generally horizontal plane relative to the horizontal portion of the infill well; and producing hydrocarbons included in the production fluid from the reservoir through the horizontal portion of the infill well from the production chamber.

4. The method of any one of claims 1-3, wherein the injection well is located at a position of the reservoir with a vertical overburden stress greater than a horizontal stress and comprising the step of increasing the horizontal stress at the position such that it is greater than the vertical overburden stress.

5. The method of claim 4 wherein the step of increasing the horizontal stress comprises injecting the mobilizing fluid at a pressure at or near the reservoir's maximum operating pressure and at a high temperature.

6. The method of claim 4 or claim 5, wherein the position is about 300 meters below a topmost surface of the reservoir.

7. The method of any one of claims 4-6, wherein the mobilizing fluid comprises steam.

8. The method of any one of claims 4-7, wherein the mobilizing fluid is injected at a rate of about 400 tonnes/day.

9. A method for recovering hydrocarbons from an oil sands reservoir, comprising:
achieving fluid communication between a first and a second injection well and a production well in well pairs formed in the reservoir, wherein a horizontal portion of the production well is provided below the horizontal portions of the first and second injection wells and wherein the first and second injection wells inject a mobilizing fluid and the production well produces a production fluid;
deliberately initiating a first fracture in the reservoir, the first fracture extending from the horizontal portion of the first injection well along a first generally horizontal plane relative to the horizontal portion of the first injection well;
deliberately initiating a second fracture in the reservoir, the second fracture extending from the horizontal portion of the second injection well along a second generally horizontal plane relative to the horizontal portion of the second injection well; and producing hydrocarbons included in the production fluid from the reservoir through the horizontal portion of the production well from production chambers induced in the reservoir by the mobilizing fluid, wherein the volume of the production chambers are increased by the first and second fractures.

10. The method of claim 9, wherein the production well comprises a multilateral production well.

11. The method of claim 9 or claim 10, wherein the production well is heated with an electrical heater, by RF, or other heating methods without steam.

12. The method of claim 9, wherein the first injection well is laterally offset from the second injection well.

13. The method of claim 12, wherein the production well is laterally offset from the first injection well or the second injection well.

14. The method of claim 12 or claim 13, wherein the lateral offset avoids an inclined heterolithic stratification (IHS) baffle in the reservoir.

15. The method of any one of claims 1-14, wherein the production well continues to be heated after fluid communication is achieved between the injection well and the production well.

16. The method of any one of claims 1-15, wherein initiating the fracture comprises injecting a high pressure fluid.

17. The method of claim 16, wherein the high pressure fluid is steam.

18. The method of any one of claims 1-17, wherein the mobilizing fluid comprises solvent without steam.

19. The method of any one of claims 1-18, wherein the mobilizing fluid comprises solvent co-injected with steam.

20. The method of any one of claims 1-19, wherein the mobilizing fluid comprises steam.

21. The method of any one of claims 1-20, further comprising recovering the hydrocarbons.

22. The method of any one of claims 1-21, wherein producing the hydrocarbons comprises draining the hydrocarbons by gravity into the production well.

23. The method of claim 1, wherein producing the hydrocarbons comprises operating a steam assisted in-situ hydrocarbon recovery process.

24. The method of claim 23, wherein the steam assisted in-situ hydrocarbon recovery process comprises a steam assisted gravity drainage system.

25. The method of claim 1, wherein producing the hydrocarbons comprises using at least one of electrical heating, electromagnetic heating, radio frequency heating, solvent injection, carbon dioxide flooding, non-condensable gas injection, flue gas flooding, surfactants injection, alkaline chemicals injection, and microbial enhanced recovery.

26. The method of any one of claims 9-25, wherein the first or the second injection well is located at a position of the reservoir with a vertical overburden stress greater than a horizontal stress and comprising the step of increasing the horizontal stress at the position such that it is greater than the vertical overburden stress.

27. The method of claim 26, wherein the step of increasing the horizontal stress comprises injecting the mobilizing fluid at a pressure at or near the reservoir's maximum operating pressure and at a high temperature.

28. A method for recovering bitumen from a bituminous sand reservoir, comprising:
achieving fluid communication between an injection well and a multilateral production well in a well pair formed in the reservoir, wherein a horizontal portion of the multilateral production well is provided below a horizontal portion of the injection well and wherein the injection well injects a mobilizing fluid and the production well produces a production fluid;
deliberating initiating a fracture in the reservoir, the fracture extending from the horizontal portion of the injection well along a generally horizontal plane relative to the horizontal portion of the injection well; and producing the bitumen included in the production fluid from the reservoir through the horizontal portion of the multilateral production well from a production chamber induced in the reservoir by the mobilizing fluid, wherein the volume of the production chamber is increased by the fracture.

29. A method for recovering bitumen from a bituminous sand reservoir, comprising:
achieving fluid communication between an injection well and a multilateral production well in well pair formed in the reservoir, wherein a horizontal portion of the multilateral production well is provided below a horizontal portion of the injection well and wherein the injection well injects a mobilizing fluid and the multilateral production well produces a production fluid;
deliberately initiating a fracture extending from the horizontal portion of the injection well along a generally horizontal plane relative to the horizontal portion of the injection well;
producing bitumen included in the production fluid from the reservoir through the horizontal portion of the multilateral production well from a production chamber induced in the reservoir by the mobilizing fluid, wherein the volume of the production chamber is increased by the fracture;
providing an infill well in the reservoir in proximity to the injection well and the production well;
deliberately initiating an infill well fracture extending from a horizontal portion of an infill well along a further generally horizontal plane from the horizontal portion of the infill well, the infill well in proximity to the injection well and the multi-lateral production well; and producing bitumen included in the production fluid from the reservoir through the horizontal portion of the multilateral production well from an infill well production chamber induced in the reservoir by the mobilizing fluid.

30. A method for recovering bitumen from a bituminous sand reservoir, comprising:
achieving fluid communication between a first injection well and a production well and between a second injection well and the production well in well pairs formed in the reservoir, wherein a horizontal portion of the first injection well is spaced apart from a horizontal portion of the second injection well, and a horizontal portion of the production well is located below the horizontal portions of the first and second injection wells and wherein the first and second injection wells inject a mobilizing fluid and the production well produces a production fluid;

deliberately initiating a first fracture in the reservoir, the first fracture extending from the horizontal portion of the first injection well along a first generally horizontal plane relative to the horizontal portion of the first injection well;
deliberately initiating a second fracture in the reservoir, the second fracture extending from the horizontal portion of the second injection well along a second generally horizontal plane relative to the horizontal portion of the second injection well; and producing the hydrocarbons included in the production fluid from the reservoir through the horizontal portion of the production well from production chambers induced in the reservoir by the mobilizing fluid, wherein the volume of each of the production chambers is increased by the fracture.

31. A method for recovering bitumen from a bituminous sand reservoir, comprising:
achieving fluid communication between the injection well and the production well in a well pair formed in the reservoir, wherein a horizontal portion of the production well is provided below a horizontal portion of the injection well and wherein the injection well injects steam, the production well produces a production fluid, and the injection well is at a position in the reservoir with a vertical overburden stress greater than a horizontal stress;
injecting steam into the injection well at a pressure close to a maximum operation pressure of the reservoir and a high temperature to modify a stress regime at the position to increase the horizontal stress until it is greater than the vertical overburden at the position;
deliberately initiating a fracture in the reservoir, the fracture extending from the horizontal portion of the injection well along a generally horizontal plane relative to the horizontal portion of the injection well; and producing hydrocarbons included in the production fluid from the reservoir through the horizontal portion of the production well from a production chamber induced in the reservoir by the mobilizing fluid, wherein the volume of the production chamber is increased by the fracture.

32. A system for recovering hydrocarbons from an oil sands reservoir, comprising:
at least one injection well and at least one multilateral production well, wherein a horizontal portion of the at least one multilateral production well is provided below a horizontal portion of the at least one injection well and wherein the at least one injection well injects a mobilizing fluid;

at least one fracture deliberately initiated in the reservoir, the at least one fracture extending from the horizontal portion of the at least one injection well along a generally horizontal plane relative to the horizontal portion of the at least one injection well and the at least one fracture initiated after fluid communication has been established between the at least one injection well and the at least one multilateral production well; and a production chamber induced by the mobilizing fluid, the production chamber having an increased volume due to the fracture.

33. The system of claim 32, comprising at least one infill well in the reservoir in proximity to the at least one injection well and the at least one multilateral production well; and at least one infill well fracture, the at least one infill well fracture extending from a horizontal portion of the at least one infill well along a further generally horizontal plane relative to the horizontal portion of the at least one infill well.

34. A system for recovering hydrocarbons from an oil sands reservoir, comprising:
a first injection well and a second injection well in the reservoir, a horizontal portion of the second injection well spaced apart from a horizontal portion of the first injection well, wherein the first and second injection wells inject a mobilizing fluid;
a multilateral production well, the multilateral production well having a horizontal portion located below the horizontal portions of the first injection well and the second injection well;
at least one fracture deliberately initiated in the reservoir, the at least one fracture extending from the horizontal portion of each of the first injection well and the second injection well along a generally horizontal plane relative to the horizontal portions of the first injection well and the second injection well and the at least one fracture initiated after fluid communication has been established between each of the first and second injection wells and the multilateral production well; and at least one production chamber induced by the mobilizing fluid having an increased volume due to the at least one fracture.

35. The system of claim 34, comprising an electric heater for heating the production well.

36. The system of claim 34, wherein the first injection well is laterally offset from the second injection well.

37. The system of claim 34, wherein the production well is laterally offset from the first injection well or the second injection well.

38. The system of claim 36 or 37, wherein the lateral offset avoids an 1HF
baffle in the reservoir.

39. The system of any one of claims 32-38, wherein the injection well is adapted for injecting a heated fluid or viscosity-reducing agent.

40. The system of claim 39, wherein the heated fluid comprises steam.

41. The system of any one of claims 32-40, wherein the at least one fracture is formed by injection of a high pressure fluid.

42. The system of claim 41, wherein the high pressure fluid is steam.

43. The system of any one of claims 32-42 comprising production equipment for producing the hydrocarbons from the reservoir through the horizontal portion of the production well.

44. The system of claim 43, wherein the production equipment comprises a steam assisted gravity drainage system.

45. The system of claim 44, wherein the production equipment comprises a cyclic steam stimulation system.

46. The system of claim 45, wherein the production equipment is configured to mobilize the hydrocarbons using at least one of electrical heating, electromagnetic heating, radio frequency heating, solvent injection, carbon dioxide flooding, non-condensable gas injection, flue gas flooding, surfactants injection, alkaline chemicals injection, and microbial enhanced recovery.

47. The system of any one of claims 32 to 46, wherein the multilateral production well comprises a plurality of lateral production wells.

48. The system of any one of claims 32 to 46, wherein the multilateral production well is forked.

49. The system of any one of claims 32 to 48, wherein the at least one fracture is formed after a stress regime proximate the injection well has been modified.

50. The system of claim 49, wherein the stress regime is modified by increasing the horizontal stress such that it is greater than the vertical overburden stress.

51. The system of claim 49 or 50, wherein the stress regime is modified by injection of a high pressure fluid into the injection well.

52. The system of claim 51, wherein the high pressure fluid comprises steam.

53. A system for recovering bitumen from a bituminous sand reservoir, comprising:
at least one injection well and at least one multilateral production well, wherein a horizontal portion of the at least one multilateral production well is provided below a horizontal portion of the at least one injection well and wherein the at least one injection well injects a mobilizing fluid;
at least one fracture deliberately initiated in the reservoir, the at least one fracture extending from the horizontal portion of the at least one injection well along a generally horizontal plane relative to the horizontal portion of the at least one injection well and the at least one fracture initiated by injection of steam into the at least one injection well after fluid communication has been established between the at least one injection well and the at least one multilateral production well;
and a production chamber induced by the mobilizing fluid, the production chamber having an increased volume due to the fracture.