CA2584712A1

CA2584712A1 - Methods of improving heavy oil production

Info

Publication number: CA2584712A1
Application number: CA 2584712
Authority: CA
Inventors: Bernard Compton Chung; Mintu Bose; Stewart Allan Morton; Kenneth James Elkow; Ed Erlendson; Francis Lai; David Peter Meeks; Kenneth Myron Oberg; Louis Chiu-Hung Leung; James Nelson Ireland
Original assignee: Nexen Inc
Current assignee: CNOOC Petroleum North America ULC
Priority date: 2007-04-13
Filing date: 2007-04-13
Publication date: 2008-10-13
Anticipated expiration: 2027-04-13
Also published as: CA2584712C

Abstract

The invention provides an improved method for extracting heavy oil or bitumen contained in a reservoir. The invention involves directing the formation of a solvent fluid chamber through the combination of directed solvent fluid injection and production at combinations of horizontal and/or vertical injection wells so as to increase the recovery of heavy oil or bitumen contained in a reservoir. The wells are preferably provided with flow control devices to achieve uniform production.

Description

d II

2 FIELD OF THE INVENTION

3 [0001] The present invention is directed to oil extraction processes used in the recovery of

4 hydrocarbons from hydrocarbon deposits.

BACKGROUND OF THE INVENTION

6 [0002] There exist throughout the world deposits or reservoirs of heavy oils and bitumen 7 which, until recently, have been ignored as sources of petroleum products since the contents 8 thereof were not recoverable using previously known production techniques.
While those 9 deposit;s that occur near the surface may be exploited by surface mining, a significant amount of heavy oil and bitumen reserves may occur in formations that are too deep for surface mining, 11 typicall,y referred to as "in situ" reservoirs or deposits because extraction must occur in situ or 12 from within the reservoir or deposit. The recovery of heavy oil and/or bitumen in these in situ 13 deposits may be hampered by the physical characteristics of the heavy oil and bitumen 14 contained therein, particularly the viscosity of the heavy oil and/or bitumen. While there is no clear diefinition, heavy oil typically has a viscosity of greater than 100 mPas (100 cP), a specific 16 gravity of 10 APE to 17 API and tends to be mobile (e.g. capable of flow under gravity) under 17 reservoir conditions, while bitumen typically has a viscosity of greater than 10,000 mPas 18 (10,000 cP), a specific gravity of 7 API to 10 API and tends to be immobile (e.g. incapable of 19 flow under gravity) under reservoir conditions. The above noted physical characteristics of the heavy oil and bitumen (collectively referred to as heavy oil") typically render these components 21 difficult to recover from in situ deposits and, as such, in situ processes and/or technologies 22 specific to these types of deposits are needed to efficiently exploit these resources.

23 [0003] Several techniques have been developed to recover heavy oil from in situ deposits, 24 such as steam assisted gravity drainage (SAGD), as well as variations thereof using hydrocarbon solvents (e.g. VAPEX), steam flooding, cyclic steam stimulation (CSS) and in-situ 26 combustion. These techniques involve attempts to reduce the viscosity of the heavy oil so that 27 the heavy oil and bitumen can be mobilized toward production wells. One such method, SAGD, 28 provides for steam injection and oil production to be carried out through separate wells. The 29 SAGD configuration provides for an injector well which is substantially parallel to, and situated above a producer well, which lies horizontally near the bottom of the deposit.
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1 communication between the two wells is established, and as oil is mobilized and produced from 2 the producer or production well, a steam chamber develops. Oil at the surface of the enlarging 3 steam chamber is constantly mobilized by contact with steam and drains under the influence of 4 gravity..

[00041 An alternative to SAGD, known as VAPEX, provides for the use of hydrocarbon 6 solvents rather than steam. A hydrocarbon solvent or mixture of solvents such as propane, 7 butane, ethane and the like can be injected into the reservoir or deposit through an injector well.
8 Solvent fluid at the solvent fluid/oil interface dissolves in the heavy oil thereby decreasing its 9 viscosity, causing the reduced or decreased viscosity heavy oil to flow under gravity to the production well. The hydrocarbon vapour forms a solvent fluid chamber, analogous to the steam 11 chamber of SAGD.

12 [0005] It has been recognized, however, that these prior means used for the recovery of 13 heavy oil from subterranean deposits need to be optimized.

[0006] An aspect of the present invention includes a method for extracting hydrocarbons 16 from in a reservoir containing hydrocarbons having an array of wells disposed therein, the 17 methoci comprising: (a) injecting a solvent fluid into the reservoir through a first well in the array;
18 (b) producing reservoir fluid from a second well in the array, the second well offset from the first 19 well, to drive the formation of a solvent fluid chamber between the first and the second well; (c) injecting the solvent fluid into the solvent fluid chamber through at least one of the first and 21 seconcl wells to expand the solvent fluid chamber within the reservoir, and (d) producing 22 reservoir fluid from at least one well in the array to direct the expansion of the solvent fluid 23 chamber within the reservoir.

24 [0007] An aspect of the present invention includes a method for extracting hydrocarbons from a reservoir containing hydrocarbons, the method comprising: (a) injecting a solvent fluid 26 into thf: reservoir through a first well disposed in the reservoir, (b) producing reservoir fluid from 27 a second well disposed in the reservoir and offset from the first well to create a pressure 28 differential between the first and second well, the pressure differential being sufficient to 29 overcome the gravity force of the solvent fluid so as to drive the formation of a solvent fluid chamber towards the second well.

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1 [0008] Another aspect of the present invention includes a method for extracting 2 hydrocarbons from a reservoir containing hydrocarbons, the method comprising: (a) injecting a 3 solvent fluid into the reservoir through a first well disposed in the deposit; (b) producing reservoir 4 fluid frcim a second well disposed in the reservoir and offset from the first well so as to drive the formation of a solvent fluid chamber towards the second well until solvent fluid breakthrough 6 occurs at the second well; (c) injecting the solvent fluid into the solvent fluid chamber through 7 the second well to increase the surface area of the solvent fluid chamber;
and (d) producing 8 reservoir fluid in the solvent fluid chamber from the first well.

9 [0009] Another aspect of the present invention includes a method for extracting hydrocarbons from a reservoir containing hydrocarbons, the method comprising:
(a) injecting a 11 solvent: fluid into the reservoir through a first vertical well disposed in the deposit; (b) producing 12 reservoir fluid from a second vertical well disposed in the reservoir offset from the first vertical 13 well so as to drive the formation of a first solvent fluid chamber towards the second vertical well 14 until solvent fluid breakthrough occurs at the second vertical well; (c) injecting the solvent fluid into the reservoir through a first horizontal well disposed in the deposit and offset from the first 16 and second vertical wells so as to create a second solvent fluid chamber, and (d) producing 17 reservoir fluid from the horizontal well and injecting solvent fluid into the first solvent chamber so 18 as to dirive the first solvent fluid chamber towards the second solvent fluid chamber. In a further 19 aspectõ the horizontal well may include completion and production strings.
In another aspect, the cornpletion string may be provided with flow control devices as described further herein.

21 [0010] Another aspect of the present invention includes a method for extracting 22 hydrocarbons from a reservoir containing hydrocarbons, the method comprising: (a) injecting a 23 solvent: fluid into the reservoir through a first well disposed in the reservoir; (b) producing 24 reservoir fluid from a second well disposed in the reservoir and offset from the first well to create a direct solvent fluid channel between the first and second well; (c) injecting solvent fluid into the 26 reservoir from at least one of the first and second wells and producing reservoir fluid from at 27 least one of the first and second wells to create at least two solvent fluid chambers, each of the 28 solvent fluid chambers having oil/solvent fluid" mixing and "solvent fluid/oil mixing".

29 [0011] In one aspect the present invention provides a method for extracting hydrocarbons from a reservoir having at least one well, the method comprising injecting a solvent fluid into the 31 reservoir through the welt and extracting a reservoir fluid from the at least one well.

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1 [0012] In one aspect the present invention provides a method for extracting hydrocarbons 2 from a reservoir having at least one well, the at least one well having at least one completion 3 string dkisposed therein, the method comprising injecting a solvent fluid into the reservoir through 4 the at least one completion string and extracting a reservoir fluid from the at least one well.

[0013] In one aspect the present invention provides a method for extracting hydrocarbons 6 from a reservoir having at least one well, the at least one well having at least one completion 7 string diisposed therein, the method comprising injecting a solvent fluid into the reservoir through 8 the at least one completion string and extracting a reservoir fluid from the at least one well, 9 wherein the at least one completion string includes two or more flow control devices located on a portion thereof in the reservoir.

11 [0014] In one aspect the present invention provides a method for extracting hydrocarbons 12 from a reservoir having at least one well, the at least one well having at least one completion 13 string aind at least one production string disposed therein, the method comprising injecting a 14 solvent fluid into the reservoir through the at least one completion string and extracting a reservoir fluid from the reservoir through the at least one completion string and extracting the 16 reservoir fluid from the at least one well through the at least one production string.

17 [0015] In one aspect the present invention provides a method for extracting hydrocarbons 18 from a reservoir having at least one well, the at least one well having at least one completion 19 string aind at least one production string disposed therein, the method comprising injecting a solvent fluid into the reservoir through the at least one completion string and extracting a 21 reservoir fluid from the reservoir through the at least one completion string and extracting the 22 reservoir fluid from the at least one well through the at least one production string, wherein the 23 at leasi: one completion string includes two or more flow control devices located on a portion 24 thereof in the reservoir.

[0016] In one aspect the present invention provides a method for extracting hydrocarbons 26 from a reservoir, comprising at least one first well and at least one second well, the method 27 comprising injecting a solvent fluid into the reservoir through the at least one first well and 28 extractiing a reservoir fluid from the at least one second well.

29 [0017] In one aspect the present invention provides a method for extracting hydrocarbons from a reservoir, comprising at least one first well and at least one second well, the at least one 21632082.1 4 .. ....-. ....................... ........ .- .. .. . .............. ......
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1 first well having at least one completion string disposed therein, the method comprising injecting 2 a solvent fluid into the reservoir through the at least one completion string and extracting a 3 reservc-ir fluid from at least one of the wells.

4 [0018] In one aspect the present invention provides a method for extracting hydrocarbons from a reservoir, comprising at least one first well and at least one second well, the at least one 6 first well having at least one completion string disposed therein, the method comprising injecting 7 a solvent fluid into the reservoir through the at least one completion string and extracting a 8 reservoir fluid from at least one of the wells, wherein the at least one completion string includes 9 two or more flow control devices located on a portion thereof in the reservoir.

[0019] In one aspect the present invention provides a method for extracting hydrocarbons 11 from a reservoir, comprising at least one first well and at least one second well, the at least one 12 first well having at least one completion string and at least one production string disposed 13 therein, the method comprising injecting a solvent fluid into the reservoir through at least one of 14 the connpletion strings and the second wells and extracting a reservoir fluid from at least one of the connpletion strings and the second wells and extracting the reservoir fluid from the at least 16 one first well through the at least one production string.

17 [0020] In one aspect the present invention provides a method for extracting hydrocarbons 18 from a reservoir, comprising at least one first well and at least one second well, the at least one 19 first well having at least one completion string and at least one production string disposed therein, the method comprising injecting a solvent fluid into the reservoir through the at least 21 one first completion string and the at least one second well and extracting a reservoir fluid from 22 the reservoir from at least one of the completion strings and the second wells and extracting the 23 reservoir fluid from the at least one of the at least one production string or second well, wherein 24 at leasi: one of the completion strings includes two or more flow control devices located on a portion thereof in the reservoir.

26 [0021] In one aspect the present invention provides a method for extracting hydrocarbons 27 from a reservoir, comprising at least one first well and at least one second well, the at least one 28 first well having at least one first completion string disposed therein, the at least one second well 29 having at least one second completion string disposed therein, the method comprising injecting a solvent fluid into the reservoir through at least one of the completion strings and extracting a 21632092.1 5 ....... . ..... .................. . . ............. ................. ...

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1 reservoir fluid from at least one of the wells, wherein at least one of the completion strings 2 includes two or more flow control devices located on a portion thereof in the reservoir.

3 10022] In one aspect the present invention provides a method for extracting hydrocarbons 4 from a reservoir, comprising at least one first well and at least one second well, the at least one first well having at least one first completion string and at least one first production string 6 disposiad therein, the at least one second well having at least one second completion string 7 disposed therein, the method comprising injecting a solvent fluid into the reservoir through at 8 least oine of the completion strings and extracting a reservoir fluid from the reservoir from at 9 least one of the first completion strings and the second wells and extracting the reservoir fluid from the at least one first well through the at least one production string or the at least one 11 seconcl well, wherein at least one of the completion strings includes two or more flow control 12 devices located on a portion thereof in the reservoir.

13 [0023] In one aspect the present invention provides a method for extracting hydrocarbons 14 from a reservoir, comprising at least one first well and at least one second well, the at least one first well having at least one first completion string and at least one first production string 16 disposed therein, the at least one second well having at least one second completion string and 17 at leasit one second production string disposed therein, the method comprising injecting a 18 solveni: fluid into the reservoir through at least one of the completion strings and extracting a 19 reservoir fluid from the reservoir from at least one of the completion strings and extracting the reservoir fluid from at least one of the first and second wells through at least one of the first or 21 second production strings, wherein at least one of the completion strings includes two or more 22 flow control devices located on a portion thereof in the reservoir.

23 [0024] In a further aspect, the present invention includes a method for extracting 24 hydrocarbons from a reservoir having at least one first well and at least one second well, the at least oine first well having at least one first completion string and at least one first production 26 string ciisposed therein, and the at least one second well having at least one second completion 27 string and at least one second production string disposed therein, the method comprising: (a) 28 injecting a solvent fluid into the reservoir through at least one of the completion strings; (b) 29 extracting reservoir fluid from the reservoir from at least one of the completion strings, wherein the at least one second well is offset from the at least one first well, to drive the formation of a 31 sotveni: fluid chamber befween the at least one first well and the at least one second well; (c) 32 injecting the solvent fluid into the solvent fluid chamber through at least one of the completion 2183209,21 6 . ....._.... ............. ................ .. ............... .. ..........
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x 4 1 strings to expand the solvent fluid chamber within the reservoir; (d) extracting reservoir fluid 2 from the reservoir from at least one of the completion strings to direct the expansion of the 3 solvent fluid chamber within the reservoir, and (e) extracting the reservoir fluid from at least one 4 of the first and second wells through at least one of the first or second production strings, whereiri at least one of the completion strings includes two or more flow control devices located 6 on a pcirtion thereof in the reservoir.

7 [0025] In a further aspect, the present invention includes a method for extracting 8 hydrocarbons from a reservoir having at least one first well and at least one second well, the at 9 least orie first well having at least one first completion string and at least one first production string disposed therein, and the second well having at least one second completion string and at 11 least orie second production string disposed therein, the method comprising: (a) injecting a 12 solvent fluid into the reservoir through the at least one of the completion strings disposed in the 13 reservair; (b) extracting reservoir fluid from the at least one of the completion strings disposed in 14 the reservoir, the at least one second well being offset from the at least one first well to create a pressure differential between the at least one first and the at least one second well, the pressure 16 differential being sufficient to overcome the gravity force of the solvent fluid so as to drive the 17 formation of a solvent fluid chamber towards the at least one second well;
and (c) extracting the 18 reservoir fluid from at least one of the first and second wells through at least one of the first or 19 second production strings, wherein at least one of the completion strings includes two or more flow control devices located on a portion thereof in the reservoir.

21 [0026] In a further aspect, the present invention includes a method for extracting 22 hydrocarbons from a reservoir having at least one first well and at least one second well, the at 23 least orre first well having at least one first completion string and at least one first production 24 string disposed therein, and the at least one second well having at least one second completion string and at least one second production string disposed therein, the method comprising: (a) 26 injecting a solvent fluid into the reservoir through at least one of the completion strings disposed 27 in the reservoir, (b) extracting reservoir fluid from the reservoir from at least one of the 28 completion strings disposed in the reservoir, the at least one second well being offset from the 29 at least one first well so as to drive the formation of a solvent fluid chamber towards the at least one second well until solvent fluid breakthrough occurs at the at least one second well; (c) 31 injecting the solvent fluid into the solvent fluid chamber through at least one of the completion 32 strings to increase the surface area of the solvent fluid chamber; (d) producing reservoir fluid 21s32o92.1 7 ................. ....... _ ..................... ........... ....
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1 from the solvent fluid chamber in the reservoir using at least one of the completion strings; and 2 (e) extracting the reservoir fluid from at least one of the first and second wells through at least 3 one of ithe first or second production strings, wherein at least one of the completion strings 4 includes two or more flow control devices located on a portion thereof in the reservoir.
[0027] En a further aspect the present invention includes a method for extracting 6 hydrocarbons from a reservoir having at least one first well and at least one second well, the at 7 least one first well having at least one first completion string and at least one first production 8 string dlisposed therein, and the at least one second well having at least one second completion 9 string aind at least one second production string disposed therein, the method comprising: (a) injecting a solvent fluid into the reservoir through at least one of the completion strings disposed 11 in the reservoir; (b) extracting reservoir fluid from the reservoir from at least one of the 12 completion strings disposed in the reservoir, the at least one second well being offset from the 13 at least one first well to create a direct solvent fluid channel between the at least one first and 14 the at least one second well; (c) injecting solvent fluid into the reservoir from at least one of the completion strings; (d) producing reservoir fluid from the reservoir using at least one of the 16 completion strings to create at least two solvent fluid chambers, each of the solvent fluid 17 chambers having "oil/solvent fluid" mixing and "solvent fluid/oil mixing", and (e) extracting the 18 reservoir fluid from at least one of the first and second wells through at least one of the first or 19 second production strings, wherein at least one of the completion strings includes two or more flow control devices located on a portion thereof in the reservoir.

21 [0028] In a further aspect, the present invention includes a method for extracting 22 hydrocarbons from a reservoir having at least one first well and at least one second well, the at 23 least one first well having at least one first completion string and at least one first production 24 string clisposed therein, and the at least one second well having at least one second completion string and at least one second production string disposed therein, the method comprising: (a) 26 injecting a solvent fluid into the reservoir through at least one of the completion strings disposed 27 in the reservoir; (b) extracting reservoir fluid from the reservoir from at least one of the 28 completion strings disposed in the reservoir, the at least one second well being vertically and 29 laterally offset from the at least one first well so as to drive the formation of a solvent fluid chamber towards the at least one second well until solvent fluid breakthrough occurs at the at 31 least one second well; (c) injecting the solvent fluid into the solvent fluid chamber through at 32 least one of the completion strings to increase the surface area of the solvent fluid chamber; (d) 21632092.1 8 ....
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_il w 1, 1 producing reservoir fluid from the solvent fluid chamber in the reservoir using at least one of the 2 completion strings; and (e) extracting the reservoir fluid from at least one of the first and second 3 wells thirough at least one of the first or second production strings, wherein at least one of the 4 completion strings includes two or more flow control devices located on a portion thereof in the reservciir.

6 [0029] In a further aspect the present invention includes a method for extracting 7 hydrocarbons from a reservoir having at least one first well and at least one second well, the at 8 least one first well having at least one first completion string and at least one first production 9 string dlisposed therein, and the at least one second well having at least one second completion string and at least one second production string disposed therein, the method comprising: (a) 11 injecting a solvent fluid into the reservoir through at least one of the completion strings disposed 12 in the reservoir; (b) extracting reservoir fluid from the reservoir from at least one of the 13 completion strings disposed in the reservoir, the at least one second well being vertically and 14 laterally offset from the at least one first well to create a direct solvent fluid channel between the at least one first and the at least one second well; (c) injecting solvent fluid into the reservoir 16 from at least one of the completion strings; (d) producing reservoir fluid from the reservoir using 17 at leasi: one of the completion strings to create at least two solvent fluid chambers, each of the 18 solvent fluid chambers having "oil/solvent fluid" mixing and "solvent fluid/oil mixing", and (e) 19 extracting the reservoir fluid from at least one of the first and second wells through at least one of the first or second production strings, wherein at least one of the completion strings includes 21 two or more flow control devices located on a portion thereof in the reservoir.

23 [0030] Various objects, features and attendant advantages of the present invention will 24 become more fully appreciated and better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts 26 throughout the several views.

27 [0031] Figure 1(a) and (b) are schematic perspective views of an array of horizontal wells;
28 [0032] Figure 2 is a schematic side view of a horizontal well, comprising a completion string 29 with a plurality of flow control devices;

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1 [0033] Figure 3 is a schematic side view of a horizontal well, comprising a production string 2 and a completion string having a plurality of flow control devices;

3 [0034] Figures 4 and 5 are schematic perspective views of horizontal wells for use with 4 embodiments of the present invention; and [0035] Figures 6 and 7 are schematic end views of horizontal wells for use with 6 embodiments of the present invention.

7 [00361 Figures 8 to 10 are schematic plan views of horizontal and vertical wells for use with 8 embodiments of the present invention;

9 [0037] Figure 11 is a schematic side view of horizontal and vertical wells for use with embodiiments of the present invention;

11 [0038] Figure 12 is a schematic end view of horizontal and vertical wells for use with 12 embodiments of the present invention.

14 [0039] In order that the invention may be more fully understood, it will now be described, by way of example, with reference to the accompanying drawings in which Figures 1 through 7 16 illustrate embodiments of the present invention.

17 [0040] In the description and drawings herein, and unless noted otherwise, the terms 18 "vertical", "lateral" and "horizontal", can be references to a Cartesian co-ordinate system in 19 which tlhe vertical direction generally extends in an "up and down"
orientation from bottom to top while the lateral direc#ion generally extends in a"left to right" or "side to side" orientation. In 21 additiori, the horizontal direction generally extends in an orientation that is extending out from or 22 into the page. Altematively, the terms "horizontal" and "vertical" can be used to describe the 23 orientation of a well within a reservoir or deposit. "Horizontal" wells are generally oriented 24 parallel to or along a horizontal axis of a reservoir or deposit. The horizontal axis and thus the so-called "horizontai wells" may correspond to or be parallel to the horizontal, vertical or lateral 26 direction as represented in the description and drawings. "Vertical" wells are generally oriented 27 perpendicular to horizontal wells and are generally parallel to the vertical axis of the reservoir.
28 As with the horizontal axis, the vertical axis and thus the so-called "vertical wells" may 21632092.1 10 _........._.......... .._........... .................._......
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1 correspond to or be parallel to the horizontal, vertical or lateral direction as represented in the 2 description and drawings. It will be understood that horizontal wells are generally 80 to 105 3 relative to the vertical axis of the reservoir or deposit, while ver4cal wells are generally 4 perpendicular relative to the horizontal axis of the reservoir or deposit.

[0041] Many known methods of heavy oil recovery or production empioy means of reducing 6 the viscosity of the heavy oil located in the deposit so that the heavy oil will more readily flow 7 under reservoir conditions to the production wells. Steam or solvent fluid flooding of the 8 reservoir to produce a steam or solvent fluid chamber in SAGD and VAPEX
processes may be 9 used to reduce the viscosity of the heavy oil within the deposit. While a SAGD process reduces the viscosity of the heavy oil within the deposit through heat transfer, a VAPEX process reduces 11 the viscosity by dissolution of the solvent into the heavy oil. Such techniques show potential for 12 stimulating recovery of heavy oil that would otherwise be essentially unrecoverable. While 13 these processes, particularly VAPEX, may potentially increase heavy oil production, these 14 known processes may not sufficiently maximize recovery of the heavy oil so that the in situ deposit can be produced in an economically or cost efficient or effective manner. The objective 16 of embodiments of the present invention is to improve recovery of heavy oil in these in-situ 17 deposits so as to effectively, efficiently, and economically maximize heavy oil recovery. The 18 embodiiments of the present invention are directed to the use of a solvent fluid, which may 19 consist of a solvent in a liquid or gaseous state or a mixture of gas and liquid, so as to effectively and efficiently maximize oil recovery by increasing the mixing process of the solvent 21 fluid (e.g. either a solvent liquid or solvent fluid) with the heavy oil contained in the formation, 22 thus improving the oil recovery from particular underground hydrocarbon formations.

23 [0042] The present invention is directed to producing a solvent fluid chamber having a 24 desired configuration or geometry between at least two wells. In an aspect of the present invention, a solvent fluid chamber having a desired configuration or geometry is formed between 26 one well that may be vertically, horizontally or laterally offset irom another well so as to 27 maximize the recovery of heavy oil from in-situ deposits. It will be understood by a person 28 skilled in the art that the use of the term "offset" herein refers to wells that can be displaced 29 n:lative to one another within the reservoir or deposit in a lateral, horizontal or vertical orientafi;on. The solvent fluid may comprise steam, methane, butane, ethane, propane, 31 pentanes, hexanes, heptanes, carbon dioxide (C02) or other solvent fluids which are well known 32 in the art, either alone or in combination, as well as these solvent fluids or mixtures thereof 21632092.1 11 .......... ..... ...._...... . ...........

x n, 1 mixed with other non-condensable gases. The solvent fluid (e.g. solvent liquid, gas or mixtures 2 thereoi) chamber configuration of the present invention provides for an increase in the surface 3 area of the solvent fluid chamber that is in contact with heavy oil contained within the deposit.
4 The increased contact between the fluid chamber and the heavy oil leads to increased mixing between the fluid (e.g. solvent liquid, gas or mixtures thereof) and the heavy oil. The increased 6 mixingõ in tum, leads to increased production of the heavy oil from a producing well. The fluid 7 that is "produced" or flows into the producing well, typically in a liquid state, from within the 8 deposiit to the surface or elsewhere where it is collected typically comprises reduced or 9 decreased viscosity heavy oil, solvent fluid, other components or mixtures thereof. This mixture of reduced viscosity heavy oil and other components has a viscosity less than that of heavy oil, 11 namely 1 to 100 cP, and can be referred to as "decreased viscosity heavy oil", "reduced 12 viscosity heavy oil" or "production oil". As noted above, heavy oil, namely heavy oil and bitumen 13 have viscosities of between 100 to 5,000,000 cP.

14 [0043] Figures 1(a) and 1(b) of the present application show an example of a known configuiration of at least one injector well and one production well in a heavy oil deposit 1. As 16 shown in Figure 1(a), two vertically offset horizontal wells 5 and 10 are provided. These can be 17 previously existing horizontal wells that may have been drilled for primary production or newly 18 drilled welis for secondary production processes such as SAGD or VAPEX.
Well 5 can be used 19 to inject a solvent fluid, such as steam, propane, methane, etc., into deposit 1 so as to create a solvent fluid chamber 15 having an outer edge 20. Outer edge 20 has a given surface area that 21 is in contact with the heavy oil of the deposit. The fluid aiong the surface area of the outer edge 22 20 of the fluid chamber 15 interfaces with the heavy oil contained within the deposit. If the fluid 23 is a solvent fluid such as methane, propane, etc., the solvent fluid at the surface area of the 24 solvent fluid chamber will mix with the heavy oil along the surface area of the fluid chamber through known mechanisms such as diffusion, dispersion, capillary mixing, etc.
This "fluid over 26 oil" surlPace area mixing between the solvent fluid and the heavy oil of the deposit will result in a 27 decrease in the viscosity of the heavy oil located near outer edge 20. It will be understood that 28 the terrn "fluid over oil" surface area mixing refers to the type of mixing that occurs when the 29 fluid of the fluid chamber mixes into the heavy oil of the deposit by only diffusion, dispersion, capillary mixing, etc. and is unaided by the effects of gravity, and will be understood in greater 31 detail below. At some point during the "fluid over oil" surface area mixing, the viscosity of the 32 heavy oil along the surface area of the solvent fluid chamber will have been decreased 33 sufficlently to form decreased viscosity heavy oil which will begin to flow to the production well 21632092.1 12 .......... ..........
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1 10 under the influence of gravity as indicated by the arrows provided in Figure 1(a). If steam is 2 used as the solvent fluid, it will be understood that while the steam per se does not mix with the 3 heavy oil along the surface area, the heat of the steam will penetrate the heavy oil so as to 4 decrease the viscosity of the heavy oil so as to begin or increase its flow under gravity. As a result of the mixing (such as, for example, if a solvent fluid is used in a gaseous state) or the 6 heat transfer (such as, for example, if steam is used as the solvent fluid), a volume 25 along the 7 horizontal well length of decreased viscosity oil having an outer edge 26 is formed allowing the 8 improved viscosity heavy oil within area 25 to flow by gravity into production well 10 in the 9 direction provided in the arrows of Figure 1(a). As more solvent fluid or steam is injected into chamber 15 from well 5, fluid chamber 15 will begin to expand in the direction of arrows 26a to 11 mix witti the heavy oil contained in the deposit. As such, the outer edge or border 26 of mixed 12 heavy ciil and solvent fluid or steam will migrate or move through the deposit as the steam or 13 gas mixes with the high viscosity heavy oil. In tum, the lower viscosity heavy oil and solvent fluid 14 mixture will flow via gravity to the production well 10 thus reducing the overall amount of heavy oil in the deposit 1.

16 [0044] Similar to the configuration of Figure 1(a), Figure 1(b) provides three offset horizontal 17 wells, tvvo of which can be considered upper wells 30 and 35, laterally offset from one another, 18 while the remaining well could be considered a lower well 40, laterally and vertically offset from 19 upper wells 30 and 35. Similar to the process discussed in relation to Figure 1(a), Figure 1(b) provides that a solvent fluid is injected into the upper wells 30 and 35 to form a fluid chamber 41 21 such that the heavy oil either mixes with the solvent fluid (e.g. in the case of the methane, etc.) 22 or receives the heat of the solvent fluid thereby decreasing or reducing the viscosity of the 23 heavy olil which then flows under the influence of gravity to producing well 40.

24 [0045] In the prior art examples provided in Figure 1(a) and (b), it will be understood that the productiion of heavy oil from production wells 10 and 40 are limited by (a) the rate at which the 26 decreased viscosity heavy oil or production oil flows under gravity to the production well (the 27 "gravity drainage rate"); or (b) the rate of mixing of the solvent fluid within the solvent fluid 28 chamber and the heavy oil contained within the reservoir or deposit (hereinafter referred to as 29 the "solvent fluid/oil mixing rate"). Provided that the gravity drainage rate is not the rate limiting factor under reservoir conditions, the production of decreased viscosity heavy oil or production 31 oil will generally be determined by the amount of decreased viscosity heavy oil or production oil, 32 that has a viscosity sufficiently low to flow under gravity to the production well. This in turn will 21632092.1 13 . . . ........... ............................._...

1 be dependent upon the solvent fluid/oil mixing rate. The solvent fluid/oil mixing rate is 2 influenced by the surface area of the solvent fluid chamber through which the heavy oil and the 3 solvent fluid of the solvent fluid chamber can interact and by any mechanisms which lead to 4 mixing of the heavy oil and the solvent fluid. In other words, if there is an increase in the surface area of the solvent fluid chamber so as to increase the solvent fluid/oil contact area, the 6 solveni: fluid/oil mixing rate will increase. In addition, any mechanisms which can lead to 7 increased oil and solvent fluid mixing will increase the solvent fluid/oil mixing rate which in tum 8 leads to an increase in the production of decreased viscosity heavy oil (i.e. production oil) from 9 the reservoir. In order to maximize production from the producing well, it is desirable, therefore, to maximize the solvent fluid/oil mixing rate.

11 [0046] The present invention is directed, therefore, to maximizing the solvent fluid/oil mixing 12 rate by increasing the surface area mixing of the solvent fluid in the solvent fluid chamber with 13 the heaivy oil of the deposit through directing the creation and maintenance of a solvent fluid 14 chamber having a desired conflguration or geometry. The solvent fluid chamber of the present invention has an increased surface area over solvent fluid chambers created using previously 16 known imethods of heavy oil production such as SAGD and VAPEX. Embodiments of the 17 present invention provide for the use of horizontal or vertical production/injection wells as well 18 as combinations thereof to direct and/or maintain the formation of a solvent fluid chamber 19 having a geometry or configuration so as to maximize the solvent fluid/oil mixing rate by increasing the surface area mixing of the solvent fluid in the solvent fluid chamber with the 21 heavy oil. The embodiments of the present invention involve directing and maintaining the 22 creatiori or development of a solvent fluid chamber having a desired geometry or configuration 23 between offset horizontal or vertical injection and production wells through the use of 24 simultaneous solvent fluid injection and reservoir fluid production between the offset wells and alternating injection and production between them.

26 [0047] In accordance with the present invention, a solvent fluid chamber having the desired 27 geometry or configuration can be formed between two vertically, horizontally or laterally offset 28 wells so as to provide for increased mixing of the solvent fluid and heavy oil. The wells of the 29 present invention could be either generally vertical or generally horizontal wells or combinations thereof. The solvent fluid chamber of the present invention increases the mixing of the solvent 31 fluid within the solvent fluid chamber and the heavy oil of the deposit by providing increased 32 surface area of the solvent fluid chamber, which provides for both "fluid over oil" mixing and "oil 21632092.1 14 .... . ... ......... _... ...,,........ . .................... ...........
............... ............ .................. ............ ..... . ...
........ .... .... ..... . ....... ..... _.,..
, ., ~ IJ

1 over fluid" mixing. "Fluid over oil" mixing is discussed above in relation to Figures 1(a) and 1(b).
2 It will be understood that "oil over fluid" mixing refers to the mixing that occurs when the solvent 3 fluid of the solvent fluid chamber lies underneath the heavy oil of the deposit. In other words, it 4 will be understood that at least a portion of the surface area of the solvent fluid chamber is disposE:d vertically below the heavy oil in the deposit. As a result of this configuration, the 6 mixing of the heavy oil and the solvent fluid within the solvent fluid chamber will be increased 7 relative to those chambers which provide predominately "fluid over oil"
mixing. In "fluid over oil"
8 mixing, the solvent fluid mixes with the heavy oil under known mechanisms such as diffusion, 9 dispersion, capillary mixing, etc. However, with "oil over fluid" surface area mixing there is an additiorial mixing force at work, namely gravity. As the solvent fluid of the solvent fluid chamber 11 typically has a lower density or is "lighter" than the heavy oil within the deposit, the fluid will tend 12 to be influenced to migrate into the heavy oil due to its buoyancy. This method of mixing could 13 be described as gravity induced counter-flow mixing of upper heavier oil with a lower lighter 14 solvent fluid. Also, the heavy oil above the solvent fluid will also be influenced to migrate into the fluicl chamber due to its higher density. In effect, the mixing of the solvent fluid and the 16 heavy oil is increased due to the effect of the migration tendency of the solvent fluid into the 17 heavy oil and vice versa. As a result, the solvent fluid chamber of the present invention 18 increases the fluid/oil mixing rate due to the increases in surface area and the increases in 19 overall imixing rate due to the additional mixing of oil over fluid mixing not present in prior art methods of heavy oil production.

21 Solvent Fluid Chamber Creation Using Horizontal Wells 22 [0048] In one embodiment, a solvent fluid is injected into the well via the annulus. In a 23 preferred embodiment, the solvent fluid is injected into the reservoir via a completion string.

24 [0049] In one embodiment, the wells may comprise one or more completion strings, wherein the one or more completion strings may include two or more flow control devices, located on a 26 portion of the completion strings in the reservoir, for a uniform injection of the solvent fluid into 27 the reservoir and uniform production of reservoir fluid from the reservoir.

28 [0050] Referring to Figure 2, a capped well 200 is shown comprising an annulus 300 29 defined by a well casing 400. The well 200 is provided with an annulus dividing means 500 that separat.es a portion of a completion string 202 located in the reservoir from a portion of the 31 completion string located outside of the reservoir and of the casing annulus 300. The portion of .... ........ ............. . ..................... ....._.......... .. . ...
.. . .. ....... .................... ..... ........
, II

1 I 1 M 1 M+

1 the completion string located in the reservoir is provided with at least two flow control devices 2 203. Annular isolation means 210, 211, 214 and 215 are also provided for the zonal isolation of 3 a portion of the completion string located in the reservoir. The annular isolation means are 4 located internally of the horizontal well casing 700. Preferably, the annular isolation means are aligned with packers 216, 217, 218 and 219 located extemally of the horizontal well casing 700.
6 [0051] Preferably the horizontal well casing is provided with a reticulated liner to prevent the 7 ingress of particulate matter from the reservoir. The reticulated liner may be a slotted liner or a 8 sand screen of the type known to those of skill in the art.

9 [0052] In use, solvent fluid is injected through the completion string into the reservoir. The solvent fluid passes through the at least two flow control devices 203. The solvent fluid enters 11 the reservoir by flowing through the reticulated liner to initiate and develop a solvent fluid 12 chamber in the reservoir.

13 [0053] The completion string in accordance with the present invention is also suitable for 14 extracting reservoir fluid from a reservoir. Reservoir fluid flows into the completion string 202, through the reticulated liner and at least two flow control devices 203. The reservoir fluid is then 16 pumped out of the well through the completion string.

17 [0054] Referring to Figure 3, a preferred embodiment of the present invention is shown.
18 The well 200 further comprises a production string 201. The completion string further comprises 19 flow means 600 to permit fluid communication between the completion string 202, the annulus 300 and the production string 201.

21 [0055] Optionally, the production string may be provided with a pump 301.

22 [0056] In one embodiment, solvent fluid may be injected into the reservoir through the 23 completion string. During this injection some of the solvent fluid may escape from the 24 completion string 202 into the annulus 300 via the flow means 600. However, as the well may be capped and may be under pressure, such fluid escape may be limited. The solvent fluid then 26 passes through the flow control devices 203. The solvent fluid enters the reservoir by flowing 27 through the reticulated liner to initiate and develop a solvent fluid chamber in the reservoir.

28 [0057] In another embodiment, solvent fluid may be injected through the annulus 300 of the 29 well 200. When the well 200 is capped, solvent will flow from the annulus 300 into the injection 21632092.1 16 ., , I~

1 4 A , 1 string 2:02 via flow means 600. The solvent fluid then passes through the flow control devices 2 203. Tlhe solvent fluid enters the reservoir by flowing through the reticulated liner to initiate and 3 develop a solvent fluid chamber in the reservoir.

4 [0058] The completion string in accordance with the present invention is also suitable for extracting reservoir fluid from a reservoir. Reservoir fluid flows into the completion string 202, 6 through the reticulated liner and flow control devices 203. The reservoir fluid then flows through 7 the portion of the completion string located in the reservoir. The reservoir fluid then exits the 8 completion string through the flow means 600 into the annulus of the well.
The annulus dividing 9 means prevents the reservoir fluid from re-entering the portion of the well located in the reservoir. The reservoir fluid in the annulus in then extracted from the well through the 11 production string, using pump 301, if required.

12 [0059] This arrangement is advantageous as it permits the uniform injection of solvent fluid 13 into a nBservoir and the uniform production of reservoir fluid from a reservoir.

14 [0060] As will be understood by persons skilled in the art, the arrangement in accordance with the present invention is advantageous as, during fluid injection, when the injection fluid is 16 flowing through the injection string, the fluid may be subjected to flow friction, which results in a 17 frictional pressure loss, particulariy when flowing through a horizontal section of an injection 18 string.

19 [0061] This pressure loss normally exhibits a non-linear and increasing pressure loss along the injection string. Thus, the outflow rate of the solvent fluid into the reservoir will also be non-21 linear and may decrease in the downstream direction of the injection string. At any position 22 along a horizontal injection string, for example, the driving pressure difference (differential 23 pressure) between the fluid pressure within the injection string and the fluid pressure within the 24 reservoir rock may exhibit a non-linear and greatiy decreasing pressure progression. Thereby, the radial outflow rate of the injection fluid per unit of horizontal length will be substantially 26 greater at the upstream "heel" portion of the horizontal section than that of the downstream "toe"
27 portion of the well. Thus, the fluid injection rate along the injection string thereby becomes 28 irregular. This causes substantially larger amounts of fluid to be pumped into the reservoir at 29 the "heel" portion of the well than that the "toe" portion of the well.

21632092.1 17 __.. ............. ..... ........ ........ .... ......... ......
, ; ~I

1 [0062] Accordingly, the solvent fluid will flow out of the horizontal section of the well and 2 spread out within the reservoir as an irregular, non-uniform (inhomogeneous) and partly 3 unpredictable injection front, inasmuch as the injection front drives reservoir fluids towards one 4 or more production wells.

[0063] An uneven injection rate may also occur as a result of non-homogeneity wlthin the 6 reservciir. That part of the reservoir having the highest permeability will receive most fluid. This 7 may also create an irregular flood front, and the fluid injection thus becomes non-optimal with 8 respect: to downstream recovery from production wells.

9 [0064] Thus, the present arrangement of two or more flow control devices enables a uniform and relatively straight-line injection front to be achieved, moving through the reservoir and 11 pushing the reservoir fluid in front of it.

12 [0065] Advantageously, the arrangement of the present invention also provides for the 13 uniform production of reservoir fluid along the length of a horizontal well.

14 [0066] As will be appreciated by those of skill in the art, when reservoir fluid flows downstiream and onwards in the horizontal section of a completion string, said fluid is subjected 16 to flow lfriction in the form of a frictional pressure drop. In the downstream direction, this 17 frictional pressure drop normally exhibits a non-linear and strongly increasing pressure drop 18 gradient, particularly where this pressure drop gradient occurs largely as a result of the 19 continual draining of new volumes of reservoir fluid into and along the production tubing downstream of said horizontal section. Thus, the flow rate of the fluids increases in the 21 downstream direction. As a result of said pressure drop gradient, the intemal fluid flow in the 22 compleition string will therefore exhibit a non-linear and greatly decreasing fluid pressure 23 gradient in the downstream direction. When reservoir fluid extraction from a reservoir is started, 24 the fluicl pressure in the surrounding reservoir rock will often be retatively homogenous and change very little along the horizontal section. At the same time, the frictional pressure drop of 26 the fluicis when flowing from the reservoir rock and radially into the completion string is small in 27 comparison with the frictional pressure drop of the fluids in and along the horizontal section of 28 the well. At any position along this horizontal section, the pressure difference (differential 29 pressure) that arises between the fluid pressure in the reservoir rock and the corresponding fluid pressure inside the production tubing wilf therefore exhibit a non-linear and strongly increasing 31 differential pressure gradient. In practice, such a differential pressure gradient allows the radial 21632092.1 18 ......... .. . . .......... . ............ ........... ................... ...
.........._. ......... . ... ... ............................ .

I I INa 1 inflow rate of the fluid per unit length of the horizontal section to be significantly greater at the 2 downstream side (the "heel" portion of the well) than at the upstream side (the "toe" portion of 3 the well) of the horizontal section.

4 [0067] When producing hydrocarbons via a horizontal well, the radial inflow rate per unit length of the horizontal section is significantly greater in some reservoir zones than in other 6 zones of the same reservoir, and that said former zones are drained significantiy faster than the 7 [atter zones. For most horizontal wells, this means that most of the hydrocarbon production is 8 produced from the reservoir zones at the downstream side of the horizontal section, i.e. at the 9 "heel" portion of the well, while reiatively small voiumes of hydrocarbons are produced from zones along the remaining part of the horizontal section, and in particular from the upstream 11 side of the horizontai section, i.e. the "toe" portion of the well. This leads to some reservoir 12 zones being produced faster than other zones of the reservoir. Fluid flow produced from the fast 13 draining zones may, at an eariier point than is desired, contain large unwanted amounts of 14 solvent fluid. This variable production rate from the various zones of the reservoir also cause differences in fluid pressure between the reservoir zones, which may also lead to the formation 16 fluids flowing among other things into and along an annulus between the outside of the 17 compietion string and the borehole wall of the well, instead of flowing inside said completion 18 string.

19 [0068] Thus, the present arrangement of two or more flow control devices, together with annular isolation means advantageously enables a uniform production of reservoir fluid along 21 the length of the completion string located in the reservoir in addition to the uniform injection of 22 solvent fluid.

23 [0069] Of course, it will be further appreciated by those of skill in the art that, in connection 24 with a horizontal well, it may also be desirable to create an injection front having a geometric shape that is, for example, curvilinear, arched or askew. Thereby, it is possible, using the 26 arrangement of the present invention to better adjust, control or shape the injection front relative 27 to the specific reservoir conditions and to the positions of other wells.

28 [0070] In one embodiment, the two or more flow control devices may be disposed in a 29 housingi enclosing the completion string.

21632092.1 19 ._......... ............ ............... ................ ...............
................. _....... ............ ...........
I !I

1 [0071] in one embodiment, the two or more flow control devices may have a diameter 2 greater than 1 mm. In a further embodiment, the two or more flow control devices may have a 3 diameter of about 2 to 5mm. It wili be appreciated by those of skill in the art that such diameters 4 are not Intended to be construed as limiting the invention in any way.
Various other diameters may be used depending upon various process and equipment configurations.

6 [0072] In yet a further embodiment, the two or more flow control devices may be located at 7 varying distances along the along the portion of the injection string 202 located in the reservoir.
8 It will be appreciated by those of skill in the art that the location of the flow control devices will 9 vary considerably from well to well depending on such factors as local geology and the like. In another= embodiment, the two or more flow control devices may be located at regular intervals 11 along the portion of the injection string located in the reservoir. In stiil a further embodiment, 12 high densities of flow control devices may be located at certain intervals along the injection 13 string to maximise injection and extraction of fluid into and out of the well. In still a further 14 embodiment, a flow control device may be provided at every joint of the injection string.
Preferably, this may be every 13.5 metres. It will be appreciated by those of skill in the art that 16 such distances are not intended to be construed as limiting the invention in any way. Various 17 other distances may be used depending upon various process and equipment configurations.
18 [0073] in another embodiment, the two or more flow control devices may be arranged to 19 have varying diameters along the length of the well, as is generally known to those of skill in the art, in order to provide a uniform distribution of the solvent fluid into the reservoir. in another 21 embodiment, the two or more flow control devices may be arranged such that flow control 22 devices of smaller diameter are found upstream of the well, whilst flow control devices of larger 23 diameter are found downstream of the well. This arrangement provides a gradient of varying 24 flow coritrot device diameters along the length of the well. In another embodiment, the density of the tvvo or more flow control devices may be increased, while at the same time maintaining a 26 constant diameter of the two or more flow control devices. It will be appreciated by those skilled 27 in the art that other arrangements of flow control devices are not excluded from the present 28 invenfion.

29 [0074] In one embodiment, the flow control devices may be inserts that are inserted into bores located in the completion string, that are of complementary conffguration to the inserts.
31 Altematively, In another embodiment, the flow control devices may comprise an adjustable 21632092.11 20 ........... ....... ........... ......_ ...... ..... .. ... ........... ...
................ ......... ........ ........._.._....... ....
................... ...... ........................._. .............
i ~I

x x 1 sleeve or ball valve. The sleeves or ball valves may be adjusted electrically, hydraulically or 2 electro-hydraulically.

3 [00751 In one embodiment, the annulus isolation means may be provided by packers that 4 are generally known to those of skill in the art. In a further embodiment, these packers may be expanclable packers. The expandable packers may expand in the presence of liquid 6 hydrocarbons or water and provide zonal isolation of oil producing zones in the wells. It will be 7 appreciated, by those of skill in the art, that although four packers are shown, fewer or greater 8 numbers of these packers may be used. It will be further appreciated that other packers, 9 generally known to those of skill in the art, may be used.

10076] It is a further advantage of the present invention that the use of annulus isolation 11 means enables discrete inflow and outflow zones of solvent fluid from the completion string.
12 This may prevent unwanted cross- or transverse flows of solvent fluid in the annulus during 13 injection. Preferably, each outflow zone may be provided with a configuration of flow control 14 devices; immediately prior to lowering and installing the completion string in the well. This is advantageous, as much of the reservoir and well information is often acquired immediately prior 16 to installing a completion string. Thus, an optimal pressure profile for the solvent fluid along the 17 completion string may be calculated immediately prior to installing the string in the well. The 18 arrangement of annular isolation means together with the two or more flow control devices 19 enables uniform injection and production profiles to be obtained.

[0077j Preferably, the completion string may also be used as a logging string for the 21 collection of data from the well relating to, for example, temperature, pressure and flow rates.
22 [00781 In a preferred embodiment, the arrangement of the present invention is parbcularly 23 useful for extracting reservoir fluid from reservoirs comprising angled or diagonal solvent fluid 24 chambers, where at least one first well is vertically and laterally offset from at least one second well.

26 [0079] As shown in Figures 4 to 7, wells 50 and 51 may comprise a well arrangement 27 generally known to those of skill in the art. Preferably, wells 50 and 51 may comprise a well 28 arrangement as set forth in Figure 2. Most preferably, wells 50 and 51 may comprise a well 29 arrangement as set forth in Figure 3. Well 52 may comprise an arrangement as set forth in Figure 3 described above. One embodiment of the present invention provides for the creation 2163zosz.l 21 ; .'f .

i I 14 N.

1 of a solvent fluid chamber between horizontal wells vertically and laterally offset from one 2 another. As provided in figures 6 and 7, horizontal wells 50 and 51 can be drilled generally 3 parallel to one another and generally parallel to the longitudinal axis of reservoir or deposit 49 in 4 an upper portion of in situ reservoir or deposit 49 having heavy oil contained therein. In Figures 4 to 7, the longitudinal axis of deposit 49 would be extending outwardly from the page, e.g. in a 6 horizorital orientation, towards the viewer. Horizontal well 52 can also be infill drilled so as to be 7 offset vertically and laterally from horizontal wells 50 and 51. It will be understood that existing 8 wells from previous production of in situ deposit 49, which may have been previously drilied, 9 may also be used. For example, horizontal wells 50, 51 or 52 may have been used in primary production of deposit 49.

11 [0080] As shown in Figure 5, solvent fluid (such as methane, propane, etc.) can be injected 12 into hoiizontal well 52 while "reservoir fluid", which can consist of one or more of decreased 13 viscosit.y heavy oil (e.g. production oil), water, pre-existing formation gas (e.g. natural gas) or 14 solvent fluid is produced from horizontal wells 50 and 51. Production at horizontal wells 50 and 51 continues until a significant amount (i.e. greater than 50%) of the reservoir fluid produced at 16 wells 50 and 51 is solvent fluid. In other words, as production proceeds at wells 50 and 51, the 17 percentage of solvent fluid of the total reservoir fluid produced will increase, while the 18 percentage of the other components of the reservoir fluid produced will decrease. When the 19 percentage of the solvent fluid is generally greater than 50% of the solvent fluid produced relative to the total reservoir fluid produced, significant solvent fluid "breakthrough" has 21 occurred. As production proceeds at well 50 while solvent fluid is simultaneously injected into 22 deposit 49 via well 52, a solvent fluid chamber 53a will be created (see Figure 5) that is oriented 23 away from well 52 towards well 50. In general, and as shown in Figure 5, the solvent fluid 24 chamber is delimited by upper and lower upwardly inclined boundaries. The upper and lower upwardly inclined boundaries converge towards well 50. Solvent fluid chamber 53a may, for the 26 purposes of illustration in Figure 5 and not to be considered limiting, have a generally elongated 27 wedge ishape with the apex generally oriented towards well 50 and the elongated base oriented 28 towards and extending along the horizontal length of well 52. The volume of the elongated 29 wedge base is generally largest nearest the injection well (e.g. well 50 in Figure 5) as this area tends to have the highest volume of solvent fluid. As the process described herein proceeds, 31 the solvent fluid chamber will continue to expand as more solvent fluid is injected. It will be 32 understood however, that the specific configuration or geometry of solvent fluid chamber 53a 33 wili be dictated by reservoir conditions and by the injection and production procedures as 21632092_1 22 _. ........ . .. ..... .. ....... .............. ........ ..... .. ..........
.. . .......... .....
, ,.

, il IWY. .

1 described herein. Similarly, as production proceeds at well 51 while solvent fluid is injected into 2 deposii: 49 via well 52, a second solvent fluid chamber 53b, similar in configuration and 3 geometry to solvent fluid chamber 53a as noted above, will be created.

4 [0081] As shown in Figure 5, each of solvent chambers 53a and 53b are angled or formed diagonally between injection well 52 and each of wells 50 or 51. An aspect of the present 6 invention is to create an upwardly indined solvent fluid chamber for each pair of injection and 7 production wells (e.g. 50 and 52 or 51 and 52), the upwardly inclined solvent fluid chambers 8 each delimited by upper and lower upwardly inclined boundaries which tend to converge 9 towards the upper well (e.g. 50).

[0082] The conditions under which this angled or diagonal solvent fluid chamber is formed 11 between each pair of injection and production wells will depend on the specific reservoir 12 conditions, such as horizontal and vertical permeability as well as the viscosity of the heavy oil 13 in the deposit or reservoir. In other words, the reservoir conditions will determine or dictate the 14 injection or production pressures and rates as well as pressure gradients through which the solvent fluid chambers of the present invention are formed and maintained. The conditions that 16 will likely determine the formation of the solvent fluid chamber in accordance with the present 17 invention Include the rates and pressures at which a solvent fluid may be injected into a deposit, 18 the horizontal and vertical permeability of a deposit, the rate or pressure of production at the 19 producing wells and the pressure d'ifFerential between the injection and production wells. The flow rata of fluid through a permeable matrix is proportionate to the permeability and inversely 21 proporaonate to the viscosity of the fluid. Hence, high permeability and low viscosity oil will 22 result ini and require high injection and production rates. In order to direct the creation, 23 formation or maintenance of the upwardly indined diagonal fluid chamber, the injected fluid 24 must be forced or driven towards the production well and should not be allowed to rise or gravity override to the top of the reservoir as shown in Figure 1(b). In other words, the viscous forces 26 created by pressure differentials and high flow rates should overcome or dominate the gravity or 27 buoyancy force of the lighter injected solvent fluid. It will be understood that as the horizontal 28 and vertical permeability of the deposit increases and/or the viscosity of the heavy oil located 29 therein decreases, the ability of the solvent fluid to transverse the deposit will increase. To avoid a gravity overriding solvent chamber, as described herein, the creation, formation or 31 maintenance of the solvent fluid chamber should be directed by increasing or maximizing the 21632092.1 23 ............. . .................. .... ........ ..... ........._...
......................... ............ ..................._............. ....
........ ................ ................................. ...........
...........
III

1 injection rate at the injection well and increasing or maximizing the production rate at the 2 production wells to accommodate the permeability and viscosity conditions of the deposit.

3 [00831 In general, the solvent fluid injection rate should be as much or as fast as possibie 4 given the horizontal and vertical permeability of the deposit as well as the viscosity of the heavy oil (i.e. heavy oil and bitumen) deposited therein. Injection rates will generally be high if the 6 horizorital or vertical permeability is high andlor the viscosity of the heavy oil is low and vice 7 versa. In other words, the higher the permeability, the higher the injection rate; conversely, 8 solvent fluid injection rates tend to be lower the higher the viscosity of the heavy oil in the 9 deposit or reservoir. !f the horizontal and vertical permeability of the deposit is high (e.g.
generally exceeding 500 millidarcies (mD)), the injection rate should be correspondingly high.
11 Similarly, the production rate at the producing wells should be as high as possible given a 12 particular horizontal and vertical permeability of a given deposit and the viscosity of the heavy 13 oil deposited therein.

14 [00841 By injecting the solvent fluid at a sufficientiy high rate as noted herein and producing the reservoir fluid at a sufficiently high rate as noted herein, a pressure gradient is created so as 16 to direct flow of the solvent fluid towards the production wells away from the injection wells to 17 create an angled or diagonal solvent fluid chamber of the type or geometry as described herein.
18 This directed flow arises because the solvent fluid channels through deposit 49 to create the 19 solvent fluid chamber of the disclosed configuration or geometry. The solvent fluid channelling or preference direct flow arises because the solvent fluid, parflcularly when it is a gas, will tend 21 to move or "channel" through the deposit due to the pressure differential created between the 22 injection and production wells.

23 [00851 It will be understood that the actual or specific injection and production rates may not 24 be a siqnificant factor as each will likely depend on the reservoir conditions. The directed formation of the solvent fluid chamber of the desired configuration or geometry may be more 26 influenced by the creation of a pressure gradient or pressure difference between the injection 27 and production wells. Subject to equipment tolerances, the injection rates andlar production 28 rates shiould be as high as possible under specific reservoir conditions.

29 [0086j As shown in Figures 5 to 7, the solvent fluid injected into the deposit 49 via well 52 will tend to channel towards wells 51 and 50 to form two angled or diagonal solvent fluid 31 chambers 53a and 53b. As noted above, the specific conditions under which the angled or 21632092.1 24 , , ~i~

0 ~ A ..

1 diagonal solvent fluid chambers can be created will vary for each reservoir depending on the 2 reservoir conditions as noted above. In order to form diagonal solvent fluid chambers, such as 3 chamber 53a between wells 50 and 52, as well as chamber 53b between wells 51 and 52, the 4 rate at which the solvent fluid can be injected into well 52 should preferably be as high as possible so that injected solvent fluid directly channels through the heavy oil to wells 50 and 51, 6 respectively. Injection of the solvent fluid into well 52 must be at rates sufficiently high to induce 7 solvent fluid channelling of the injected solvent fluid. Such injection rates may be greater than 8 14,000 standard cubic meters per day (500,000 standard cubic feet per day).
It is also 9 important to produce wells 50 and 51 at the highest rates as possible so as to produce the desired pressure gradient. As such, an embodiment of the present invention provides for a 11 pressure gradient exceeding 100 kPa up to a maximum not exceeding the fracture pressure of 12 the fomiation (e.g. when the deposit or reservoir breaks apart) for heavy oil. It may even be 13 necessary to exceed the fracture pressure if the viscosity is particu3arly high, such as for 14 bitumeri.

[0087] If injection rates, production rates and pressure gradients are not sufficiently high for 16 a given reservoir, the injected solvent fluid will preferenflaily rise to the top of the reservoir due 17 to its natural buoyancy and form a solvent fluid chamber as shown in Figures 1 (a) and 1(b).
18 Such a solvent fluid chamber is known as a gravity overriding solvent chamber. An additional 19 benefit of sufi'iciently high solvent fluid injection rates, high production rates and high pressure gradients between the wells is that solvent fluid injection and the diagonal solvent fluid chamber 21 should occur along most of the length of the horizontal well. At low rates and low pressure 22 gradients between the wells, the solvent fluid injection and chamber formation may only occur 23 along leiss than 50% of the length of the horizontal well resulting in low rates of oil production.
24 However, the present invention provides for solvent fluid chamber fomnation in greater than 50%
the length of the horizontal well.

26 [0088] As shown in Figure 5, solvent fluid chambers 53a and 53b having the desired 27 configuration and geometry can be fomtied between injection well 52 and production wells 50 28 and 51 upon solvent fluid breakthrough at wells 50 and 51. As such, well 52 is in solvent fluid 29 contact with wells 50 and 51. Once the solvent fluid has reached wells 50 and 51 so as to establish the angled or diagonal fluid chambers 53a and 53b, wells 50 and 51 are switched from 31 production of reservoir fluid to injection of solvent fluid into deposit 49. Upon solvent fluid 32 breakthrough, well 52 can be simultaneously switched from injection of solvent fluid to 21682o92.1 25 11 ; f x u, 1 production of reservoir fluid, including improved viscosity heavy oil and solvent fluid. As shown 2 in Figures 6 and 7, solvent fluid can be injected into deposit 49 via wells 50 and 51 while 3 reservoir fluid is produced at well 52. In doing so, additional solvent fluid chambers 55 and 54 4 are forrned. Reservoir fluid, including decreased viscosity heavy oil or production oil and solvent fluid is then produced from well 52. As shown in Figures 6 and 7, solvent fluid is 6 continuously injected into wells 50 and 51 such that solvent fluid chambers 53a, 53b, 54 and 55 7 expandÃ in the directions of arrows 54a,b,c and 55a,b,c (see Figure 12), such that reservoir fluid 8 can be produced from well 52. Eventually, continuous solvent fluid injection into wells 50 and 51 9 and continuous production from well 52 can occur until the deposit has had a significant portion, such as 20-80%, of the heavy oil extracted.

11 [0089] It will be understood that some or all these steps can then be repeated if, for 12 example, (a) if the solvent chamber configuration or geometry is not achieved or is lost (e.g.
13 converi:s to a gravity overriding solvent chamber) due to equipment failure or the process 14 stopped for whatever reason and the solvent fluid chamber needs to be re-created; or (b) the configuration, geometry or size of the solvent fluid chamber need to be optimized (e.g. not 16 extending greater than 50% the length of the horizontal well). It will be understood that prior to 17 production at wells 50 and 51, solvent fluid injection into these wells can be done, particulariy in 18 the presence of reservoirs with high bitumen content.

19 [0090] Unlike prior art methods, such as those shown in Figures 1(a) and 1(b), the above noted embodiment of the present invention provides for an increase in the recovery of heavy oil 21 contained in deposit 49. As noted above, the rate of heavy oil recovery will be dependent on 22 the mixing of the solvent fluid within the solvent fluid chamber and the heavy oil, namely the 23 "fluid/oil mixing rate". Unlike the prior art methods noted in Figures 1(a) and 1(b), this 24 embodiment of the present invention provides for both "fluid over oil"
surface area mixing as well as "oil over fluid" surface area mixing. Gravity overriding solvent fluid chambers 15 and 41 of 26 Figures 1(a) and 1(b) provide only "fluid over oil" surface area mixing.
This is in contrast to 27 solvent fluid chambers having the desired configuration or geometry taught herein as shown in 28 Figures 5 to 7. As shown in Figure 7, the diagonal solvent fluid chambers have two areas of 29 solvent fluid and oil surface area mixing, namely upper surfaces 60, 61 and lower surfaces 62, 63 of solvent fluid chambers 53a and 53b. "Fluid over oil" mixing will occur at lower surfaces 62 31 and 63 of solvent fluid chambers 53a and 53b, respectively. Similariy, there will be "fluid over 32 oil" surface area mixing along the lower surfaces 62 and 63 of solvent fluid chambers 54 and 55.

21632092.1 26 ...... ............. .... ................. ...................
..................... . .. . ......... . ...... .. ............. .....
...................... . .......

I I I N IIY r 1 In addition to the "fluid over oil" mixing occurring at those surfaces, there will also be "oil over 2 fluid" surface area mixing at the upper surfaces 60 and 61 of solvent chambers 53a and 53b. As 3 such there will be increased mixing in the "diagonal" solvent fluid chambers of the present 4 invention over the methods known in the prior art. The increased solvent fluid and oil mixing will result in a higher production at well 52.

6 [0091] Eventually, continuous solvent fluid injection into horizontal wells 50 and 51 and 7 continuous production from horizontal well 52 can occur until deposit or reservoir 49 has had a 8 significant portion, such as 20 to 80% of the heavy oil extracted. Likewise, injection rates into 9 the horizontal wells can be adjusted to maximize the recovery of heavy oil.
If injection and production rates are too low, a gravity overriding chamber could form, reducing the recovery of 11 heavy oil. Injection and production rates must be sufficiently high to maintain the diagonal or 12 directed chamber. If injection rate is too high, more solvent may break through and may need to 13 be re-injected and re-cycled. It will be understood that as heavy oil is being extracted from the 14 area surrounding wells 50, 51 and 52, then extracting using the process noted above can concurrently or subsequently be implemented to other existing or infill drilled horizontal wells 16 (not shown) within reservoir 49.

17 [0092] As the present invention provides for the creation of an angled or diagonal solvent 18 fluid chamber between an injection horizontal well and an offset producing horizontal well, it will 19 be understood that factors that may impact the solvent fluid channelling through the deposit may have ain impact on the pmcess of the invention. For example, in formations where bottom water 21 is present, the presence of bottom water may assist in the formation of the diagonal solvent fluid 22 chamber due to the increased mobility of the solvent fluid through the water at the top of the oil-23 water tnansition zone.

24 Solvent Fluid Chamber Creation Using Horizontal and Vertical Wells [0093] As shown in Figures 8 to 12, another embodiment of the present invention provides 26 for the use of horizontal and vertical production and injection wells to direct the formation of 27 solvent fluid chambers having a desired geometry or configuration. Instead of using horizontal 28 wells only, this embodiment involves recovery using vertical injection/production wells as well as 29 horizonital injectionlproduction wells. This embodiment involves directing and maintaining the creation or development of a solvent fluid chamber having a desired geometry or configuration 31 between offset vertical injection and production wells with horizontal production and injection .... ............ ........._._..._................._..............
.............. ............_.................... ...... ..........
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1 wells ttirough the use of simultaneous solvent fluid injection and reservoir fluid production 2 between the offset vertical and horizontal wells and alternating the injection and production 3 between them.

4 [0094] As with the other embodiment of the present invention, the objective of this embodiment is to obtain improved mixing of solvent fluid with heavy oil so as to reduce the 6 viscosity of an increased amount of heavy oil allowing decreased viscosity heavy oil or 7 production oil to be produced. Instead of using horizontal wells only, this embodiment involves 8 recoveiy or production using vertical injection or production wells. This embodiment involves 9 the creation of a solvent fluid chamber between vertical injection and production wells and with offset horizontal production and injection wells.

11 [0095] In the heavy oil reservoir with or without existing vertical wells, the configuration or 12 geomeiLry of the solvent fluid chamber is determined by use of altemating the injection of solvent 13 fluid and the production of reservoir fluid, containing production oil, through the use of vertical 14 and hoiizontal wells. For example, vertical wells can be drilled (if no existing vertical wells) and, offset to these vertical wells, parallel horizontal producing wells can be drilled (if no pre-existing 16 wells) close to the bottom of the formation (e.g. within 1 meter). In this embodiment, a solvent 17 fluid chamber is first established between the vertical injection wells.
This is accomplished by 18 injecting solvent fluid and producing reservoir fluid simultaneously between paired vertical welis.
19 For example, solvent fluid can be injected into a first vertical well while producing a second vertical well until significant solvent fluid breakthrough occurs. Solvent fluid can also be injected 21 next into the first and second vertical well while producing from an offset third vertical well for a 22 desired time. This process is continued until a solvent fluid chamber has the desired geometry 23 or configuration. Solvent fluid can then be injected into a horizontal well at pressures higher 24 than at the vertical wells so as create a second solvent fluid chamber, thus reducing the viscosity of the surrounding heavy oil. Solvent fluid can be injected into the vertical wells and 26 reservoir fluid, and then production oil, can be produced from the horizontal wells until depletion 27 of the reservoir.

28 [0096] As shown in Figures 8 to 12, there are existing or infili driiled vertical wells 100, 102, 29 104, 106, 108 and 110 in a typical spatial arrangement of vertical production and injection wells within reservoir or deposit 90. It will be understood that the injection pattem can be selected 31 based on the location of existing wells, reservoir size and shape, cost of new wells and the 32 recovery increase associated with the various possible injection or production patterns.
21632092.1 28 .. .......... .......... _..... __._ ............... . ... ......
I I

1 Common injection patterns are direct line drive, staggered line drive, two-spot, three-spot, four-2 spot, five-spot, seven-spot and nine-spot.

3 [0097] Solvent fluid can be first injected into deposit 90 through vertical well 108.
4 Simultaneously, reservoir fluid is produced at vertical well 106. For reasons noted above, this will induce the formation of solvent fluid chamber 118a, as shown in Figure 8.
As the solvent 6 fluid is injected into reservoir 90 through well 108 while reservoir fluid is produced at well 106, 7 solvent fluid chamber 11 8a wiil expand to 11 8b and eventually 118c, at which point solvent fluid 8 breakthrough can occur. As a result, a continuous solvent fluid chamber 118c is created 9 between wells 108 and 106. As noted above with respect to solvent fluid chamber 53a, solvent fluid chamber 118c has a generally conical shape preferentially distorted in the direction of well 11 106. The generally conical shape of solvent fluid chamber 118c is oriented in the vertical 12 directioin with its longitudinal axis parallel to the vertical axis of well 108. The conical apex of 13 solvent fluid chamber 118c is generally oriented away from the upper portion of vertical well 108 14 and deposit 90 and points towards the lower portion of vertical well 108 and deposit 90, while the conical base is generally oriented towards the upper portion of well 108 and deposit 90. The 16 conical base is generally widest nearest the upper portion of injection well 108 as this area 17 tends to have the highest concentration of solvent fluid. As the process described herein 18 proceeds, solvent fluid chamber 118c wili expand both at the conical base and the conical apex 19 outwardly from vertical welt 108 as more solvent fluid Is injected. It will be understood however, that the specifc configuration or geometry of solvent fluid chamber 11 8c will be dictated by 21 reservoiir conditions.

22 [00981 As noted previously, the solvent fluid injection rate at 108 and reservoir fluid 23 production rate at welt 106 must be sufficiently high for the solvent fluid to channel as directly as 24 possible from well 108 towards well 106 possibly at solvent fluid injection rates exceeding 3,000 standani cubic meters per day (100,000 standard cubic feet per day). It is also important that 26 the pressure gradient between 108 and 106 be very high as possible, possibly exceeding 100 27 kPa pressure. The solvent fluid breakthrough and flow between these vertical wells must be 28 enough in volume and time to create a stable and reasonable sized solvent fluid chamber 118c.
29 The solhrent fluid breakthrough and cyding time between these wells should be one or more months long. The reservoir conditions (e.g. net oil pay, porosity and permeability) and field 31 applicatwn (e.g. distance between wells and injection and productions rates) will determine the 32 solvent fluid injection rate, volume and time.

21632092.1 29 ..... ..._ .. . ............ ... .. ....... ...... .. ............. .
................. .......................... . .. ........ . ............ .
I~I

1 [0099] If solvent fluid breakthrough does not occur then one or more infiil vertical wells 2 between wells 106 and 108 can be drilled (not shown). It will be understood that several 3 reasons could account fior the failure of the solvent fluid to break through, such as reservoir 4 discontinuity, geological barriers, poor permeability or the inter-well distance is too great due to the high viscosity of the heavy oil. For example, if an infill vertical well was made between wells 6 106 and 108, solvent fluid injection could continue at well 108 with simultaneous reservoir fluid 7 production from newly infill drilled adjacent vertical well until significant solvent fluid 8 breakttirough occurs at the newly infill drilied adjacent vertical well.
Once solvent breakthrough 9 occurs at the newiy infill drilled adjacent vertical well, solvent fluid injection can cease at vertical well 108 while the newly infill drilled adjacent verticai well switches from production to injection 11 of solvent fluid. The solvent fluid can then be injected into the newly infill drilled adjacent 12 vertical well while producing from next adjacent well such as vertical well 106 until solvent fluid 13 breakthrough occurs at well 106.

14 [00100] Following solvent fluid breakthrough at well 106, solvent fluid injection at well 108 continues while well 106 is converted from producflon to solvent fluid injection. In other words, 16 vertical well 106 is used to inject solvent fluid into fluid chamber 118c.
Production is switched to 17 vertical wells 104 and 110. For the reasons noted above, a pressure gradient will be created 18 through which the solvent fluid chamber 118c will expand towards wells 110 and 104. As with 19 the soivent fluid chamber development between 106 and 108, solvent fluid injection rates, reservoir fluid production rates and the pressure gradient between the injection and production 21 wells must be sufficiently high for the solvent fluid to channel from 106 towards 104 and from 22 108 towards 110. As shown in Figure 8. solvent fluid chamber 121 a is created by the 23 simultaineous production of reservoir fluid at well 110 and the injection of solvent fluid at well 24 108. As this simultaneous production and injection proceeds, solvent chamber 121a expands to 121 b. Similarly, solvent fluid chamber 120a is created by the simultaneous production of 26 reservoir fluid at well 104 and the injection of solvent fluid at well 106.
As this simultaneous 27 production and injection proceeds, solvent chamber 120a expands to 120b. It is not necessary 28 for solvent fluid chambers 121 b and 120b to extend to the point of solvent breakthrough at wells 29 110 and 104 respectively. Typically, the elongated gas chambers around the vertical wells should be slightly greater in length than the adjacent horizontal wells.
However, it will be 31 understood that the process could proceed until solvent fluid breakthrough occurs at wells 110 32 or 104. As shown in Figure 8, simultaneous injection and producflon at wells 104, 106, 108 and 33 110 as inoted above results in the formation of solvent fluid chamber 122.
21632092.1 30 . .... _............ ..................................... ...._..
_._......................_..... ...........
....._.._._......_................... ......_........... ...........
_............ ........ . __............... ...... .........._....... .... .
.......... .....
il 1 [00101] Once the solvent fluid chamber 122 has between established, injection of solvent 2 fluid into these wells and into the solvent fluid channels and chamber is similar to injecting 3 solvent fluid into a hypothetical horizontal well extending between these wells and along the 4 solvent fluid channel. Simply, the vertical wells in conjunction with the solvent fluid channel and chambier should act like a horizontal well. Unlike horizontal well injection, the injection and 6 production rates can be adjusted between the vertical wells providing some control over the 7 injection profile into the solvent fluid chamber and its composition. When solvent is injected into 8 a horizontal well, most of the solvent could preferentially enter the reservoir in certain parts of 9 the horizontal well bore resulting in a poor uneven Injection profile. If 2-4 ver6cal wells act as a horizontal well, having control over the injection of each verticat well provides some controi over 11 the injection profile into the solvent chamber.

12 [00142] Upon fomnation of solvent fluid chamber 122 as shown in Figure 9, solvent fluid can 13 then be injected into new or previously existing horizontal wells 112 and 114 either 14 simultaneously or altemately (e.g. inject solvent into 112 and shut in or produce 114 then inject into 114 and shut in or produce 112) at injection pressures higher than the reservoir pressures 16 at verb(al wells 106 and 108, and the reservoir pressure of solvent fluid chamber 122 between 17 106 and 108, as it will be understood that the reservoir pressures at wells 106 and 108 or in 18 chamber 122 may not be the same. As described above in reference to Figure 3, it will be 19 understood that the horizontal wells 112 and 114 may include completion and production strings. In addition, the completion strings may be provided with flow control devices as 21 discussed above. The injection pressures and/or rates at horizontal wells 112 and 114 should 22 be as high as possible as noted above in order to direct the injected solvent fluid to channel 23 laterally outwards from horizontal wells 112 and 114 towards vertical wells 106 and 108, 24 respectively and solvent fluid chamber 122, as shown in Figure 9. If there is no production at wells 108 and 106, the only pressure forcing the solvent fluid chamber to expand is the injection 26 pressure from wells 112 and 114. However, there can be injection or production at wells 106 27 and 108, if needed, depending on reservoir conditions to create the solvent fluid chamber 28 having the desired configuration. In addition to the pressure or rates being sufficiently high to 29 direct the formation of horizontal solvent fluid chambers 126 and 127 laterally towards verticai fluid chamber 122, the solvent fluid injection pressures or rates must also be sufficient to create 31 these solvent fluid chambers along most (e.g. greater than 50%) of the longitudinal length of 32 each of horizontal wells 112 and 114. As shown in Figure 9, horizontal wells 112 and 114 inject 33 solvent fluid into reservoir or deposit 90 to create horizontal sotvent fluid chambers 126 and 127.
29632092.1 31 ...............................................................................
...............................................................................
....... ............ . ... .
.j II

I d IY.

1 Solvent fluid chambers 126 and 127 are generally fusiformed or spindle shaped but distorted 2 laterally and upwards along the horizontal axis of wells 112 and 114.

3 [00103] Horizontal wells 112 and 114 are then converted to production of reservoir fluid, 4 while vertical wells 106 and 108 continue to inject solvent fluid into solvent fluid chamber 122.
For the reasons noted herein, a pressure gradient will be created through which the solvent fluid 6 chamber 122 will expand laterally towards wells 112 and 114, as shown in Figures 8 and 9. As 7 with the solvent fluid chamber development between the vertical wells, fluid injection rates, 8 reservoir fluid production rates and the pressure gradient between the vertical injection wells 9 106 an{d 108 as well as the horizontal production wells 114 and 112 must be sufficiently high for the solvent fluid to channel from existing solvent fluid chamber 122 towards horizontal solvent 11 fluid chambers 126 and 127. As shown in Figure 9, solvent fluid chamber 122 expands laterally 12 into 122a due to the simultaneous production of reservoir fluid at wells 112 and 114 and the 13 injection of solvent fluid at wells 106 and 108. As this simultaneous production and injection 14 proceeds, solvent chambers 122a, 126 and 127 expand to 122b, 126a and 127a, respectively.
This process continues until the expanding solvent fluid chamber 122, 122a and 122b converge 16 with the expanding solvent fluid chambers 126, 126a, 127 and 127a. As shown in Figure 10, 17 solvent fluid chamber 128 is in solvent fluid connection with fluid chambers 126 and 127.

18 [00104:1 Figures 11 and 12 provide cross-sectional views of the configuration or geometry of 19 the solvent fluid chambers 127 and 128. It will be understood that a cross-sectionai view of fluid chamber 126 and 128 would be the same as seen in Figure 11; therefore only the solvent fluid 21 chamber at 127 and 128 will be described. As seen in Figure 11, elongated solvent fluid 22 chambers in fluid connection are formed at each of vertical wells 106 and 108. While it will be 23 understood that the specific configuration or geometry of solvent fluid chamber 128 will be 24 dictateci by reservoir conditions, it is seen in Figure 11 as two generally conical shaped solvent fluid chambers as described above. As noted above, solvent fluid chamber 127 is generally 26 fusifomied or spindle shaped along the horizontal axis of well 112. As seen in Figure 12, two 27 angled or diagonal solvent fluid chambers in fluid connection are formed at each of horizontal 28 wells 112 and 114.

29 [00105] It will be understood that some or all these steps can then be repeated if, for example, (a) the solvent chamber configuration or geometry is not achieved or is lost (e.g.
31 converts to a gravity overriding solvent chamber) due to equipment failure or process stoppage 32 for any reason and the solvent fluid chamber needs to be re-created; or (b) the configuration, ............. ....._.._.. __..__...,......._.........._.....................
.............. ..............._......... _--- ................ ..............
..... ......._............... ....... .. .... ..
.................................... .......... ..... .

I l I I 1 N 1II e 1 geometry or size of the solvent fluid chamber need to be optimized (e.g.
create more solvent 2 fluid chamber along the horizontal well, creating more of a solvent fluid chamber between the 3 vertical wells or changing the composition of the solvent).

4 [001061 Eventually, continuous solvent fluid injection into vertical wells 106 and 108 and continuous production from horizontal wells 112 and 114 can occur until deposit or reservoir 90 6 has had a significant portion, such as 20-80%, of the heavy oil extracted.
Likewise, injection 7 rates inito the vertical welis can be adjusted to maximize the recovery of heavy oil and bitumen.
8 It wiil be understood that as the heavy oil is being extracted from the area surrounding vertical 9 wells 106 and 108 as well as horizontal wells 112 and 114, then extracting using the process noted above can concurrently or subsequently be implemented to wells 100 and 102 or others 11 within the area of reservoir 90.

12 [00107'1 Although the invention has been described with reference to certain specific 13 embodiments, various modifications thereof will be apparent to those skilled in the art without 14 departing from the purpose and scope of the invention as outlined in the claims appended hereto. Any examples provided herein are included solely for the purpose of illustrating the 16 invention and are not intended to limit the invention in any way. Any drawings provided herein 17 are solely for the purpose of illustrating various aspects of the invention and are not intended to 18 be dravrn to scale or to limit the invention in any way. The disclosures of all prior art recited 19 herein are incorporated herein by reference in their entirety.

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Claims

1. A method for extracting hydrocarbons from a reservoir having at least one first well and at least one second well, the at least one first well having at least one first completion string and at least one first production string disposed therein, and the at least one second well having at least one second completion string and at least one second production string disposed therein, the method comprising:

(a) injecting a solvent fluid into the reservoir through at least one of the completion strings disposed in the reservoir;

(b) extracting reservoir fluid from the reservoir from at least one of the completion strings disposed in the reservoir, the at least one second well being vertically and laterally offset from the at least one first well to create a direct solvent fluid channel between the at least one first and the at least one second well;

(c) injecting solvent fluid into the reservoir from at least one of the completion strings;

(d) producing reservoir fluid from the reservoir using at least one of the completion strings to create at least two solvent fluid chambers, each of the solvent fluid chambers having "oil/solvent fluid" mixing and "solvent fluid/oil mixing", and (e) extracting the reservoir fluid from at least one of the first and second wells through at least one of the first or second production strings, wherein at least one of the completion strings includes two or more flow control devices located on a portion thereof in the reservoir.

2. The method of claim 1, wherein the at least one first well and the at least one second well is horizontal.

3. The method of claim 1, wherein the two or more flow control devices have a diameter of greater than 1 mm.

4. The method of claim 1, wherein the solvent fluid chamber is delimited by vertically inclined upper and lower boundaries.

5. The method of claim 4, wherein the upper and lower boundaries converge towards the at least one second well.

6. The method of claim 1, wherein the solvent fluid is a liquid, gas or a mixture thereof and the liquid or gas is selected from the group consisting of steam, methane, butane, ethane, propane, pentanes, hexanes, heptanes, and CO2 and mixtures thereof.

7. The method of claim 6, wherein the solvent fluid further comprises a non-condensable gas.

8. The method of claim 1, wherein the hydrocarbons comprise heavy oil and/or bitumen.

9. The method of claim 1, wherein an oil/solvent fluid rate is increased in step (c) by increasing gravity induced counter-flow mixing of the solvent fluid and the hydrocarbons.

10. The method of claim 1, wherein the producing of reservoir fluid in step (b) is done concurrently with the solvent fluid injection of step (a).

11. The method of claim 1, wherein the extracting of reservoir fluid in step (d) is done concurrently with the solvent fluid injection of step (c).

12. The method of claim 1, wherein the solvent fluid injection of step (a) or step (c) may be greater than 14,000 standard cubic meters per day.

13. The method of claim 1, wherein a pressure gradient is established between the at least one first and the at least one second well in step (b) that is greater than 100 kPa.

14. The method of claim 1, wherein the steps (a) to (d) are repeated at least once.

15. The method of claim 1, wherein steps (c) and (d) are repeated at least once.

16. The method of claim 1, wherein the reservoir fluid comprises production oil.