CA3011675A1

CA3011675A1 - In situ startup process for mobilizing bitumen in a reservoir

Info

Publication number: CA3011675A1
Application number: CA3011675A
Authority: CA
Inventors: Russell Engelman
Original assignee: Suncor Energy Inc
Current assignee: Suncor Energy Inc
Priority date: 2018-07-18
Filing date: 2018-07-18
Publication date: 2020-01-18
Anticipated expiration: 2038-07-18
Also published as: CA3110928A1; CA3176086A1; CA3110928C; CA3011675C

Abstract

An in situ startup process for mobilizing bitumen between gravity drainage wells located in a bitumen containing reservoir is provided. The well pair includes an injection well and a production well respectively having a horizontal section defining an interwell region therebetween. The process includes the steps of: introducing a predetermined volume of liquid solvent via a solvent startup well selected from the injection and production wells; ceasing introduction of the liquid solvent and allowing the liquid solvent to soak within the reservoir for a soaking period to mobilize bitumen in the interwell region; producing fluids from the solvent startup well to recover a startup production fluid; separating at surface the startup production fluid into a solvent depleted bitumen component and a recovered solvent component which can be reintroduced in a subsequent introduction stage; and cyclically repeating the steps of the process to mobilize bitumen in the interwell region.

Description

IN SITU STARTUP PROCESS FOR MOBILIZING BITUMEN IN A RESERVOIR
TECHNICAL FIELD
[001] The technical field generally relates to startup processes for mobilizing bitumen contained in an underground reservoir, and more particularly to the use of liquid solvent in a cyclic startup process for mobilizing bitumen in a reservoir.
BACKGROUND

[002] There are various techniques for recovering bitumen from subsurface reservoirs.
One technique is called cyclic steam stimulation (CSS), which is a widely implemented technique for recovering oil and bitumen. Another known technique called Steam Assisted Gravity Drainage (SAGD) has become a widespread process of recovering heavy oil and bitumen. Other in situ recovery processes use solvent injection or other mobilizing fluids to help mobilize bitumen in the reservoir. In situ recovery processes can use single wells that operate cyclically through injection and production cycles, or well pairs that include an injection well and a production well.

[003] Once a well pair is drilled and completed, the first phase of operations is the so-called startup phase. In the startup phase, fluid communication is established between the injection and production wells of a given well pair. Prior to startup, the high saturation bitumen interval separating the injection and production wells of each pair has low fluid mobility and the subsequent in situ recovery process relies on initially establishing a mobile interval in between the injection and production wells. It is important for an effective bitumen recovery operation to uniformly reduce the viscosity of the bitumen between injection and production wells prior to producing it. This procedure of establishing fluid communication between two wells at the initial stages can be done by circulating a mobilizing fluid, such as steam, through one or both wells.
Solvent based methods for well pair startup and initialization has been attempted but various challenges remain.
SUMMARY

[004] According to a first aspect, an in situ startup process for mobilizing bitumen between a gravity drainage well pair located in a bitumen containing reservoir is provided.

The well pair includes an injection well having a horizontal injection section and a production well having a horizontal production section located below the horizontal injection section, the horizontal injection section and horizontal production section defining an interwell region therebetween. The process includes, in an introduction stage, introducing a predetermined volume of liquid solvent via a solvent startup well selected from the injection and production wells, at an introduction pressure and introduction temperature configured to maintain the liquid solvent in liquid phase within the solvent startup well and the reservoir, wherein the introduction pressure is at or above an initial reservoir pressure of the interwell region and below a fracturing pressure thereof. The process further includes, in a soaking stage, ceasing introduction of the liquid solvent and allowing the liquid solvent to soak within the reservoir for a soaking period in order to mobilize bitumen in the interwell region. The process still further includes, in a production stage, producing fluids from the solvent startup well to recover a startup production fluid comprising bitumen and liquid solvent. The process further includes, in a surface separation stage, separating at surface the startup production fluid into a solvent depleted bitumen component and a recovered solvent component. Finally, the process includes cyclically repeating the introduction stage, the soaking stage, the production stage and the surface separation stage to mobilize bitumen located in the interwell region.

[005] According to a possible embodiment, the recovered solvent component is reintroduced in the solvent startup well in a subsequent introduction stage.

[006] According to a possible embodiment, the liquid solvent is stored at surface within a solvent supply source, and wherein the liquid solvent is introduced within the solvent startup well via a tubing string.

[007] According to a possible embodiment, the solvent startup well includes a horizontal startup section, and wherein the tubing string is coupled to the solvent supply source and is configured to transfer liquid solvent within the horizontal startup section.

[008] According to a possible embodiment, the solvent startup well includes a vertical section, and wherein once the horizontal startup section is filled with liquid solvent, displacement fluid is introduced within the vertical section to increase pressure on the liquid solvent.

[009] According to a possible embodiment, the solvent startup well includes a liner extending along at least a portion of the horizontal startup section, and wherein the tubing string extends within the liner and defines an annulus region therebetween.

[0010] According to a possible embodiment, the liner is slotted to allow liquid solvent to exit the horizontal startup section and infiltrate the reservoir.

[0011] According to a possible embodiment, the solvent startup well includes a packer assembly mounted within the annulus region, the packer assembly defining an upstream region and a downstream region, the packer assembly being configured to prevent fluid communication between the upstream and downstream regions.

[0012] According to a possible embodiment, the solvent startup well includes a transition section connecting the vertical section and horizontal startup section, and wherein the downstream region includes at least a portion of the horizontal startup section, and the upstream region includes at least the vertical section and the transition section.

[0013] According to a possible embodiment, the packer assembly is removably mounted within the annulus region to adjust a length of the downstream region.

[0014] According to a possible embodiment, the tubing string is configured to extend through the packer assembly to introduce liquid solvent within the downstream region.

[0015] According to a possible embodiment, the solvent startup well includes a pump located within the downstream region, and wherein the production stage is enabled by the pump.

[0016] According to a possible embodiment, the pump is an electrical submersible pump (ESP).

[0017] According to a possible embodiment, during an initial introduction stage, the predetermined volume of liquid solvent exceeds an internal volume of the tubing string extending within the downstream region added to the volume of the annulus region located in the downstream region.

[0018] According to a possible embodiment, during a given introduction stage, the predetermined volume of liquid solvent is greater than the predetermined volume of liquid solvent of a previous cycle by an amount determined based at least in part by monitoring bitumen removal from the reservoir during the previous cycle.

[0019] According to a possible embodiment, the introduction pressure is between about kPa and about 100 kPa above the initial reservoir pressure.

[0020] According to a possible embodiment, the soaking stage is initiated once the predetermined volume of liquid solvent has been introduced.

[0021] According to a possible embodiment, the soaking period substantially corresponds to the amount of time required for the pressure within the solvent startup well to stabilize.

[0022] According to a possible embodiment, the production stage is initiated once the soaking period has elapsed.

[0023] According to a possible embodiment, during the production stage, the startup production fluid is produced to surface via a sub-surface pump.

[0024] According to a possible embodiment, during the surface separation stage, the startup production fluid is separated via a separator.

[0025] According to a possible embodiment, the separator is a flash separator.

[0026] According to a possible embodiment, the separator is a centrifugal separator.

[0027] According to a possible embodiment, during the surface separation stage, only a portion of the startup production fluid is separated into the solvent depleted bitumen component and the recovered solvent component.

[0028] According to a possible embodiment, the recovered solvent component is mixed with substantially pure liquid solvent prior to reintroduction.

[0029] According to a possible embodiment, during the surface separation stage, the startup production fluid is subjected to gas removal, water removal, and/or solvent make-up.

[0030] According to a possible embodiment, the startup production fluid includes a bitumen concentration, and wherein the surface separation stage is initiated if the bitumen concentration is at or above a separation threshold.

[0031] According to a possible embodiment, the liquid solvent infiltrates the reservoir via gravity and/or diffusion-based mechanisms.

[0032] According to a possible embodiment, the liquid solvent comprises at least one of dimethyl ether, methyl ethyl ketone, toluene, )rylene, diesel, butane, pentane, hexane, heptane and naphtha.

[0033] According to a possible embodiment, the solvent startup well is alternated between the injection well and production well after each cycle.

[0034] According to a possible embodiment, the solvent startup well is alternated between the injection well and production well after a plurality of cycles.

[0035] According to a possible embodiment, the subsequent introduction stage for one startup well is initiated during the soaking stage of a previous cycle of the other startup well.

[0036] According to a possible embodiment, the subsequent introduction stage for one startup well is initiated during the production stage of a previous cycle of the other startup well.

[0037] According to a possible embodiment, the subsequent introduction stage for one startup well is initiated during the surface separation stage of a previous cycle of the other startup well.

[0038] According to a possible embodiment, both the injection well and the production well are operated as solvent startup wells simultaneously.

[0039] According to a second aspect, a startup process for mobilizing bitumen surrounding a well positioned in a bitumen containing reservoir is provided.
The process includes, in an introduction stage, introducing liquid solvent within the well, the liquid solvent having introduction parameters configured to maintain the liquid solvent in liquid phase within the well system and the reservoir. The process further includes, in a soaking stage, ceasing introduction of the liquid solvent, and allowing the liquid solvent to soak within the well and the reservoir fora soaking period, and, in a production stage, producing fluids from the solvent startup well to recover a startup production fluid comprising bitumen and liquid solvent. The process still further includes, in a surface separation stage, separating at surface the startup production fluid into a solvent depleted bitumen component and a recovered solvent component, which can be reused in a subsequent cycle. Finally, the process includes cyclically repeating the introduction stage, soaking stage, production stage and the surface separation stage to mobilize the bitumen.

[0040] According to a possible embodiment, the recovered solvent component is reintroduced in the well in a subsequent introduction stage.

[0041] According to a possible embodiment, during each introduction stage, a predetermined volume of liquid solvent is introduced within the well.

[0042] According to a possible embodiment, the well is a solvent startup well, and the liquid solvent is stored at surface within a solvent supply source, and wherein the liquid solvent is introduced within the solvent startup well via a tubing string.

[0043] According to a possible embodiment, the solvent startup well comprises a horizontal startup section, and wherein the tubing string is coupled to the solvent supply source and is configured to transfer liquid solvent within the horizontal startup section.

[0044] According to a possible embodiment, the solvent startup well comprises a vertical section, and wherein once the horizontal startup section is filled with liquid solvent, displacement fluid is introduced within the vertical section to increase pressure on the liquid solvent.

[0045] According to a possible embodiment, the solvent startup well comprises a liner extending along at least a portion of the horizontal startup section, and wherein the tubing string extends within the liner and defines an annulus region therebetween.

[0046] According to a possible embodiment, the liner is slotted to allow liquid solvent to exit the horizontal startup section and infiltrate the reservoir.

[0047] According to a possible embodiment, the solvent startup well comprises a packer assembly mounted within the annulus region and defining an upstream region and a downstream region, the packer assembly being configured to prevent fluid communication between the upstream and downstream regions.

[0048] According to a possible embodiment, the solvent startup well comprises a transition section connecting the vertical section and horizontal startup section, and wherein the downstream region comprises at least a portion of the horizontal startup section, and the upstream region comprises at least the vertical section and the transition section.

[0049] According to a possible embodiment, the packer assembly is movably mounted within the annulus region to adjust a length of the downstream region.

[0050] According to a possible embodiment, the tubing string is configured to extend through the packer assembly to introduce liquid solvent within the downstream region.

[0051] According to a possible embodiment, the solvent startup well comprises a pump located within the downstream region, and wherein the production stage is enabled by the pump.

[0052] According to a possible embodiment, the pump is an electrical submersible pump (ESP).

[0053] According to a possible embodiment, during an initial introduction stage, the predetermined volume of liquid solvent exceeds an internal volume of the tubing string extending within the downstream region added to the volume of the annulus region located in the downstream region.

[0054] According to a possible embodiment, during a given introduction stage, the predetermined volume of liquid solvent is greater than the predetermined volume of liquid solvent of a previous cycle by an amount determined based at least in part by monitoring bitumen removal from the reservoir during the previous cycle.

[0055] According to a possible embodiment, the introduction parameters include an introduction temperature and an introduction pressure provided between about 10 kPa and about 100 kPa above an initial reservoir pressure.

[0056] According to a possible embodiment, the soaking stage is initiated once the predetermined volume of liquid solvent has been introduced.

[0057] According to a possible embodiment, the soaking period substantially corresponds to the amount of time required for the pressure within the well to stabilize.

[0058] According to a possible embodiment, the production stage is initiated once the soaking period has elapsed.

[0059] According to a possible embodiment, during the production stage, the startup production fluid is produced via a surface pump.

[0060] According to a possible embodiment, during the surface separation stage, the startup production fluid is separated via a separator.

[0061] According to a possible embodiment, the separator is a flash separator.

[0062] According to a possible embodiment, the separator is a centrifugal separator.

[0063] According to a possible embodiment, during the surface separation stage, only a portion of the startup production fluid is separated into the solvent depleted bitumen component and the recovered solvent component.

[0064] According to a possible embodiment, the recovered solvent component is mixed with substantially pure liquid solvent prior to reintroduction.

[0065] According to a possible embodiment, during the surface separation stage, the startup production fluid is subjected to gas removal, water removal, and/or solvent make-up.

[0066] According to a possible embodiment, the startup production fluid comprises a bitumen concentration, and wherein the surface separation stage is initiated if the bitumen concentration is at or above a separation threshold.

[0067] According to a possible embodiment, the liquid solvent infiltrates the reservoir via gravity and/or diffusion-based mechanisms.

[0068] According to a possible embodiment, the liquid solvent comprises at least one of dimethyl ether, methyl ethyl ketone, toluene, xylene, diesel, butane, pentane, hexane, heptane and naphtha.

[0069] According to a possible embodiment, the solvent startup well is alternated between an injection well and a production well after each cycle.

[0070] According to a possible embodiment, the solvent startup well is alternated between an injection well and a production well after a plurality of cycles.

[0071] According to a possible embodiment, the subsequent introduction stage for one startup well is initiated during the soaking stage of a previous cycle of the other startup well.

[0072] According to a possible embodiment, the subsequent introduction stage for one startup well is initiated during the production stage of a previous cycle of the other startup well.

[0073] According to a possible embodiment, the subsequent introduction stage for one startup well is initiated during the surface separation stage of a previous cycle of the other startup well.

[0074] According to a possible embodiment, an injection well and a production well are operated as solvent startup wells simultaneously.
BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 is a transverse cut view of a well pair and surface equipment.

[0076] Figure 2 is a transverse cut view of a well pair.

[0077] Figure 3 is a process flow diagram of an example of the startup process.

[0078] Figure 4 is a transverse cut view of a solvent startup well, showing a tubing string and a liner.

[0079] Figure 5 is a transverse cut view of a section of a solvent startup well, showing a tubing string, a packer assembly and subsurface pump.

[0080] Figure 5a is a transverse cut view of a solvent startup well, showing a transition section and a horizontal section, with a subsurface pump positioned downstream of a packer assembly.

[0081] Figure 6 is a perspective view of a section of a well pair, showing an annulus region defined between a liner and a tubing string of one of the wells.

[0082] Figures 7a to 7d are transverse cut views of a well pair illustrating example cyclic solvent injection and production for mobilizing bitumen in the reservoir.

[0083] Figures 8a to 8e are transverse cut views of a well pair illustrating an example cyclic solvent injection and production process for mobilizing bitumen in the reservoir, where two wells are used.

[0084] Figure 9 is a transverse cut views of a well pair and surface equipment illustrating an example system for cyclic startup using both wells of a well pair.

[0085] Figure 10 is a top plan view of well pads and multiple well pairs extending from the pads, as well as surface equipment for supplying solvent to and receiving startup production fluid from one or more wells of each pad for cyclic startup of multiple well pairs and multiple pads.
DETAILED DESCRIPTION

[0086] As will be explained below in relation to various example implementations, a startup process is described herein for enabling mobilization of bitumen located in a bitumen containing reservoir (R), for example between a well pair designated for a subsequent in situ bitumen recovery process. The startup process leverages the injection of solvent in liquid phase followed by soaking, producing back fluids including mobilized bitumen and liquid solvent, separating the production fluids at surface to recover solvent, and reinjecting solvent as part of a cyclical pattern. The interwell region between the well pair can thus be mobilized in order to establish fluid communication between the two wells, or to prepare the region by increasing mobility prior to subsequent startup operations, such as steam or solvent circulation.

[0087] It should be noted that the startup process can be adapted to mobilize bitumen for ultimately producing bitumen from the reservoir (R) via any suitable in situ recovery method, which may use solvent, steam, and/or other mobilizing fluids for injection. The startup process includes several steps carried out via a well assembly installed within the reservoir. The well assembly can include a single well, a well pair such as those used in SAGD or solvent assisted gravity drainage processes (e.g., using solvent-steam co-injection or solvent-only injection), or any other suitable well assembly configuration. The startup process uses liquid solvent introduced into the reservoir through one or more wells of the well assembly, referred to as a solvent startup well, in order to mobilize bitumen contained in the reservoir. In some implementations, the liquid solvent is cyclically introduced and produced back from the well assembly, for reuse, until the bitumen has been sufficiently mobilized to allow ramp up of production.

[0088] The startup process includes an initial introduction stage where liquid solvent is introduced within the reservoir via the solvent startup well. Then, the process includes a soaking stage where the liquid solvent is allowed to soak within the reservoir for a period of time in order to diffuse into and mobilize the bitumen located around a section of the solvent startup well. After the soaking time period, the process includes a production stage where fluids are produced from the startup well to recover at least some of the liquid solvent introduced during the introduction stage along with mobilized bitumen.
The process also includes a separation stage where the fluids recovered during the production stage are effectively separated in order to recover bitumen depleted liquid solvent. The introduction stage, the soaking stage, the production stage and the separation stage can be cyclically repeated until certain bitumen mobilization in the interwell region has been achieved, and optionally until fluid communication is established between the well pair.
The liquid solvent introduced in a subsequent introduction stage can be predominantly composed of the recovered liquid solvent from the production and separation stages of a previous cycle.

[0089] A more detailed description of well assemblies and process implementations that can be used in the context of in situ startup operations is provided further below. Various examples of structural features as well as operating strategies and parameters are described.
Well assembly implementations for the startup well

[0090] With reference to Figures 1 and 2, the startup process 10 can be carried out via a well system 20 including a gravity drainage well pair 21. It should be understood that the processes and techniques of the present description can also be implemented using other well assemblies and configurations, such as single wells configured for CSS
operations or single-well SAGD operations. The well pair 21 used in connection with the described startup process 10 can be a traditional SAGD well pair which can have wellheads located at a well pad that is part of an in situ recovery facility.

[0091] More specifically, the well pair 21 can include an injection well 22 having a horizontal injection section 22h and a production well 24 having a horizontal production section 24h. Each horizontal section 22h, 24h is located within the bitumen containing reservoir (R). In the illustrated implementation, the horizontal production section 24h is located vertically below the horizontal injection section 22h, thus defining an interwell region 26 therebetween. However, other arrangements of well pairs or well groups are also possible. It should therefore be appreciated that the startup process 10 can be implemented to mobilize the bitumen located in the interwell region of a well pair, and can be further operated to establish fluid communication between the wells of the well pair.

[0092] Still referring to Figures 1 and 2, the injection well 22 can further include an injection wellhead 22w, a vertical injection section 22v, and an injection transition section 22t fluidly connecting the vertical section 22v and the horizontal injection section 22h.
Similarly, the production well 24 can include a production wellhead 24w, a vertical production section 24v, and a production transition section 24t fluidly connecting the vertical section 24v and the horizontal section 24h. It should be understood that the wellheads 22w, 24w can be positioned on the well pad which is located at the surface. Alternate configurations of the well pair or group can also be used in the context of the techniques described herein.
Solvent introduction stage

[0093] Referring to Figures 3 and 4, in addition to Figures 1 and 2, the startup process can be initiated with an introduction stage 10a where liquid solvent is introduced within the reservoir via a solvent startup well 30. It should be readily understood that, in the context of the present disclosure, the expression "solvent startup well" can refer to the injection well 22 or the production well 24 or both, as will become apparent from the following detailed description. It should be understood that the solvent startup well 30 can include all of the structural features of the injection well 22 and/or the production well 24, as described above. More specifically, the solvent startup well 30 can include a startup wellhead 30w, a horizontal startup section 30h, a vertical startup section 30v, and a startup transition section 30t fluidly connecting the vertical startup section 30v and the horizontal startup section 30h.

[0094] In some implementations, the liquid solvent can be introduced within the reservoir (R) without the use of heat, such as the temperatures at which steam is traditionally introduced during regular SAGD startup and normal operations. Alternatively, the liquid solvent can be pre-heated prior to introduction down the startup well.
Additionally, the liquid solvent can be introduced within the reservoir without the use of high pressures, or pressure gradients compared to reservoir pressures, such as pressures for fracturing operations. In some implementations, the liquid solvent can be introduced within the reservoir via the solvent startup well at predetermined introduction parameters, such as an introduction pressure and an introduction temperature. The introduction parameters can be configured to maintain the liquid solvent in liquid phase throughout the main stages of the startup process and within the startup well and the reservoir. It should be understood that the introduction pressure can be at or above an initial reservoir pressure of the interwell region, but preferably exceeds the reservoir pressure in order to facilitate the introduction of liquid solvent within the reservoir (R). For example, the introduction pressure can be at most 40 kPa, 50 kPa, 70 kPa, 100 kPa, or 150 kPa above the reservoir pressure surrounding the startup well 30. The introduction pressure can be determined based on various reservoir properties, such as water mobility for example. In other words, a reservoir having high water mobility can require a lower introduction pressure (e.g., about 40 kPa) than a reservoir having low water mobility which can require a greater introduction pressure (e.g., about 100kPa to 150kPa). It should also be understood that the introduction pressure can be below a fracturing pressure of the interwell region. The introduction parameters can be determined and/or calculated using various techniques, such as pressure transient analysis (PTA) among other known techniques. The introduction pressure can thus be provided to ensure the solvent is in liquid phase within all sections of the startup well, and also to provide a slight pressure gradient (e.g., within the range of 10 kPa to 100 kPa) compared to the interwell region to encourage penetration of the solvent from the well into the reservoir while avoiding reservoir fracturing.

[0095] With reference to Figures 4 and 5, the liquid solvent can be introduced within the solvent startup well 30 via a tubing string 32. The tubing string 32 can be inserted via the startup wellhead 30w to extend down and within the horizontal section 30h in order to provide liquid solvent within the solvent startup well 30. It should be understood that in order to introduce liquid solvent within the reservoir (R) located in the interwell region, it can be desirable to at least partially or fully fill the horizontal startup section 30h to allow the liquid solvent from the well to penetrate into the reservoir. The liquid solvent can flow from the horizontal startup section for reservoir penetration via gravity and/or diffusion mechanisms of the liquid solvent within the reservoir (R). The liquid solvent can also be forced within the reservoir by substantially filling the horizontal startup section 30h, and exerting a penetration pressure on the liquid solvent which effectively fills the tubing string 32 and annulus surrounding the tubing string within the wellbore. The penetration pressure can be maintained during the introduction stage as well as the subsequent soaking stage.

[0096] In an alternative implementation, once the liquid solvent has substantially filled the horizontal startup section 30h, a displacement fluid can be introduced in an upstream portion of the well, e.g., the vertical startup section 30v, in order to exert pressure on the solvent in the downstream portion of the well, e.g., the horizontal startup section 30h. It should be understood that the displacement fluid can be different than the liquid solvent, and could be liquid or gas phase, for example water and/or nitrogen gas can be used as displacement fluids. It should be understood that introducing a displacement fluid in an upstream portion of the well can reduce the volume of liquid solvent required during the startup process.

[0097] In some implementations, the tubing string 32 can extend within the solvent startup well 30 in order to introduce liquid solvent directly within the horizontal startup section 30h and can be operated in combination with various other well features, as will be described in greater details hereinbelow.
Completions of solvent startup well

[0098] Referring to Figure 6, in addition to Figures 4 and 5, the solvent startup well 30 can include a liner 34 extending within a wellbore thereof. The liner 34 can be configured to extend from an upstream part of the horizontal section of the well, along a length of the horizontal startup section 30h and can terminate near its end. It should thus be understood that the horizontal portion of the tubing string 32 can extend within the liner 34 of the solvent startup well in order to introduce liquid solvent therein. In some implementations, the liner 34 can be slotted or include other types of apertures along a length thereof in order to allow the liquid solvent contained within the liner to infiltrate the reservoir and also to eventually allow production of reservoir fluids.

[0099] Still referring to Figures 4 to 6, in some implementations, the tubing string 32 and liner 34 define an annulus region 36 therebetween. Furthermore, the solvent startup well 30 can include a packer assembly 40 (see Figures 5 and 5a) mounted within the annulus region 36. The packer assembly 40 can define a downstream region 42 and an upstream region 44 within the solvent startup well 30, and can be configured to substantially prevent fluid communication between the upstream and downstream regions. More specifically, the packer assembly 40 can substantially block the cross-sectional area of the annulus region 36, therefore sealing the downstream region 42 from the upstream region 44. In some implementations, the packer assembly 40 can be positioned at a first end of the horizontal startup section 30h to prevent fluid communication between the vertical startup section 30v and the horizontal startup section 30h. It should be understood that preventing fluid communication between the vertical and horizontal startup sections can reduce the volume of liquid solvent required during the introduction stage. It should be further understood that the tubing string 32 can be configured to extend through the packer assembly 40 in order to introduce liquid solvent in the downstream region of the well 42.

[00100] As the liquid solvent is introduced into the horizontal startup section 30h, the packer assembly 40 prevents the liquid solvent from entering and filling the upstream region (i.e., the vertical startup section 30v and the transition section 30t). Additionally, the packer assembly 40 can reduce the desirability to introduce displacement fluid, or any other fluid, within the vertical startup section 30v in order to increase pressure on the solvent within the horizontal startup section 30h. It should be understood that the packer assembly can be positioned at any suitable location along the transition or horizontal startup section, and that positioning the packer assembly 40 further along the horizontal startup section 30h can reduce the required volume of liquid solvent needed to substantially fill the downstream region 42 and infiltrate the reservoir (R).
The packer assembly 40 can also be displaced during the startup process, e.g., changing locations between cycles.

[00101] In one implementation, the packer assembly 40 is located relatively upstream and close to the transition section of the startup well 30t, thereby defining an annulus volume. The tubing string 32 can extend the length of the liner 34 and can have an outlet 32a at its end for expelling the liquid solvent into the liner annulus 36. The volume of the annulus region defined between the packer assembly 40 and the end of the well, as well as the volume defined by the tubing string 32, can be used to determine the overall solvent volume that is introduced. For cycles later in the startup process, the solvent volume can also be determined based on a determined depletion volume of the reservoir itself due to preceding cycles of the startup process. It should be noted that depending on the completion of the well, different solvent volume determinations can be made in order to determine the solvent volume to be introduced into the startup well for a given cycle.

[00102] In addition, it should be noted that the solvent that is introduced can be relatively fresh solvent obtained from a solvent source, recovered solvent obtained from the separation stage, or in some cases production fluid that is predominantly solvent and not subjected to separation to remove bitumen. This latter case would mainly occur at early stages or cycles of the startup process, e.g., after the first and second cycles, since smaller amounts of bitumen may have been mobilized and produced back along with the solvent. In this case, the predominantly solvent production fluid could be produced back to the surface in its entirety and then reintroduced. Alternatively, only a portion of the predominantly solvent production fluid could be produced back to ensure that some of the diluted bitumen has been displaced out of the reservoir, and then the produced fluid could be reintroduced back into the startup well.

[00103] It should also be noted that part of the introduction stage can include a preliminary operations where fluids, such as drilling mud and the like, can be removed from the wellbore volume. In some implementations, the liquid solvent can displace/push out residual fluids (e.g., drilling mud) or slurries from within the wellbore to the surface, substantially cleaning the wellbore prior to regular operations. It should be understood that removing the residual fluids from the wellbore prior to regular startup operations can advantageously prevent these fluids from being produced during subsequent production stages.
Soaking stage

[00104] Following the initial introduction stage 10a (Figure 3), the startup process includes a soaking stage 10b. During the soaking stage, some of the liquid solvent located within the horizontal startup section 30h can infiltrate into the reservoir (R) in the interwell region to contact and locally reduce the viscosity of the bitumen in the reservoir.
Solvent penetration into the reservoir can mobilize a portion of the bitumen sufficiently to be producible, while some of the solvent will penetrate in lower concentrations to reduce viscosity but not enable production after that particular soaking cycle. In that sense, a portion of the solvent remains in the reservoir after soaking.

[00105] In some implementations, the soaking stage can be initiated once the horizontal startup section 30h, or downstream region 42, has been substantially filled with liquid solvent. Alternatively, the soaking stage of any given cycle can be initiated once a predetermined volume of liquid solvent has been introduced during the introduction stage of that cycle.

[00106] It should be understood that during the soaking stage, the liquid solvent is allowed to effectively soak into and within the reservoir for a certain amount of time defined as a soaking period. The soaking period can be predetermined, determined based on active monitoring, or determined based on other factors of the overall process. In some implementations, the soaking period can be a determined amount of time, such as approximately a day (i.e., 24 hours), a week, or any other suitable amount of time which would allow the liquid solvent to penetrate and at least partially mobilize bitumen contained within the reservoir. The soaking period can alternatively be the amount of time required for the pressure within the horizontal startup section 30h, or downstream region 42, to stabilize once the introduction stage has concluded. It should be understood that the pressure within the horizontal startup section 30h can be greater than the pressure within the reservoir, and will therefore decrease over time as the liquid solvent infiltrates the reservoir.

[00107] In some scenarios, the liquid solvent can penetrate the reservoir and encounter a thief or high mobility zone, resulting in loss of at least some liquid solvent.
This can be detected by monitoring pressure during the soaking phase. Once the high mobility zone has been detected, the process can be adapted accordingly, e.g., one or more additional packer assemblies can be mounted within the solvent startup well or the existing packer can be moved to isolate the thief zone. In addition, pressures exerted on the solvent can be modified to reduce solvent loss via the high mobility zone or the cyclic process terminated to mitigate further solvent loss.
Production stage

[00108] Once the soaking period has elapsed, the startup process 10 can proceed to the production stage 10c (Figure 3). The production stage can include producing fluids from the solvent startup well 30 to recover a startup production fluid which can include liquid solvent and mobilized bitumen. It should be understood that the startup production fluid can have a bitumen concentration that can increase after each cycle due to the mobilization of the bitumen within the reservoir and the increased access to reservoir bitumen as the solvent treatment zone expands around the startup well. As bitumen is mobilized after each cycle of the startup process, the production stage can produce startup production fluid including greater amounts of bitumen mixed in with the liquid solvent. In some implementations, the production stage can be enabled by a pump, such as an electrical submersible pump (ESP) deployed in the well and configured to lift the startup production fluid from within the solvent startup well 30, and direct the fluid toward the surface. Other production methods such as gas lift and the like are also possible, depending on the reservoir properties.

[00109] Referring to Figures 5 and 5a, the ESP 46 can be mounted within the wellbore of the solvent startup well 30 in order to perform the production stage. It should be understood that the ESP 46 can be mounted upstream of the packer assembly 40 in the transition section of the startup well, and would thus not be within the downstream section 42 filled with liquid solvent. In some implementations, the ESP 46 can be mounted within the transition section 30t proximate to or generally part of the horizontal startup section 30h. Other pump arrangements and locations are also possible.

[00110] The ESP 46 can be positioned in the upstream region 44 (Figure 5) or in the downstream region 42 (Figure 5a). Referring more specifically to Figure 5, the packer assembly 40 can be configured to be operated in order to selectively allow fluid communication between the upstream and downstream regions. It should be understood that the packer assembly 40 can be operated once the soaking period has elapsed for any given soaking stage, to allow startup production fluid to be produced via the ESP 46 and other corresponding equipment, such as a production line 33. With reference to Figure 5a, the packer assembly 40 can be a passive packer assembly (i.e., the packer assembly does not need to be operated dynamically) provided upstream of the ESP 46 within the wellbore. It should be understood that the ESP 46 is therefore within the liquid solvent once the downstream region 42 is filled and can be operated therefrom to initiate the production stage.

[00111] In some implementations, as illustrated in Figure 1, the startup production fluid can be produced via a surface pump 47, and transferred to a production fluid holding tank 48 for storage, prior to a subsequent separation stage, as will be described below.
Alternatively, the surface pump 47 can be configured to produce the startup production fluid, and transfer said fluid directly to a separator 49. The surface pump 47 can be coupled to the tubing string 32 in the event production is to occur via the same conduit as solvent injection. A combination of pumping arrangements and systems can also be provided, and different pumps can be used for different cycles of the startup process (e.g., surface pump for initial cycles; ESP for later cycles).
Surface separation stage

[00112] Referring back to Figure 3, in addition to Figure 1, the startup process 10 can include various implementations of a surface separation stage 10d. As mentioned above, the bitumen located within the reservoir (R) is progressively mobilized after the cycles of the startup process 10, and can therefore be produced back during the production stages. As the bitumen concentration within the startup production fluid increases, the bitumen containing liquid solvent would become increasingly inefficient at mobilizing the bitumen in subsequent cycles of the startup process. Therefore, it can be desirable to include the separation stage 10d for separating the startup production fluid into a solvent depleted bitumen component, and a recovered solvent component, which can be reintroduced in subsequent cycles.

[00113] In some implementations, the separator 49 can be configured to effectively separate the startup production fluid to recover a bitumen depleted liquid solvent, which can be a substantially bitumen free liquid solvent or can include a notable yet acceptable bitumen content. The separator 49 can be coupled to the production fluid holding tank 48 so as to receive the production fluid therefrom in the event separation is required. Non-limiting examples of the separator 49 can include a flash separator, a centrifugal separator, or any other suitable separator and/or separating method. It is nevertheless noted that relatively simple separation equipment can be used to separate a suitable quantity of the bitumen from the startup production fluid, since high purity recovered solvent is not necessary for continued solvent cycling in the startup process.

[00114] In some implementations, the initial cycles of the startup process 10 can avoid the surface separation stage altogether, as the concentration of bitumen in the startup production fluid may be substantially low and acceptable for direct reintroduction.
The produced startup fluid can be reused in subsequent cycles of the startup process without having to be transferred to the separator, reducing downtime between cycles and operating costs.

[00115] The startup production fluid can be analyzed in order to determine various properties, such as the bitumen concentration thereof. In some implementations, the startup production fluid can be analyzed during the production stage, either simultaneously while the fluid is being produced via the pump, or from the production fluid holding tank 48 after having been produced. It should thus be understood that the separation stage can be initiated once the bitumen concentration is at or above a separation threshold. In some implementations, the separation threshold can be approximately 5 wt%, 10 wt%
or 15 wt%
bitumen, for example. Therefore, when the bitumen concentration of the startup production fluid is below 10 wt%, the startup production fluid can be reintroduced via the solvent startup well as part of the subsequent cycle. However, when the bitumen concentration is above 10 wt%, the cycle can include the separation stage to separate the startup production fluid to recover a bitumen component and reusable bitumen depleted liquid solvent.

[00116] In addition, the separation stage can be operated to treat all or a portion of the startup production fluid in order to produce a recovered solvent having certain properties, e.g., bitumen content. For example, if the solvent for introduction has a target maximum bitumen threshold (e.g., 10 wt%) and the startup production fluid has a bitumen content exceeding the threshold (e.g., 12 wt%), then a portion of the production fluid can be subjected to separation and then the recovered solvent can be combined back with the remaining production fluid to provide an overall bitumen content below the threshold. In addition, since the production fluid that is produced during a given cycle may have a variable concentration (e.g., low bitumen content initially and high bitumen content near the end of production), the low bitumen production fluid can be put aside, and the high bitumen production fluid can be subjected to separation prior to combining the solvent streams for reintroduction. Thus, various management techniques can be employed in terms of selecting certain portions of the production fluid for separation or not.

[00117] It is also noted that the startup production fluid can be subjected to other surface treatments, such as gas removal, water removal, and solvent make-up.
These additional treatments can be used for certain cycles in certain cases. For example, in later startup cycles, it is possible that the startup production fluid include water from the reservoir, in which case the fluid can be supplied to a water separator (e.g., free water knockout drum) to remove most of the water. Solvent loss to the reservoir and the increasing volume of reservoir to be filled with solvent in later cycles can require adding solvent make-up to the recovered solvent prior to reintroduction.

[00118] Referring to Figures 9 and 10, the surface separation equipment can be configured to facilitate cyclic solvent startup in multiple wells and also for multiple well pads. For example, Figure 9 illustrates that a same separation unit 50 can be used for separation of startup production fluid retrieved from both the injection well 22 and the production well 24 that form a well pair, and same surface pumps 47 can be used for producing and injecting. Alternatively, each startup well could have its own dedicated production pump and injection pump (which could be the same or different pumps), and could also have its own dedicated separator 49 and associated piping and tankage, such as a recovered solvent holding tank 51. The recovered solvent holding tank 51 can be fluidly connected to the separator 49 for receiving bitumen depleted production fluid therefrom prior to reintroduction. In addition, the recovered solvent holding tank 51 can be further connected to a solvent supply source 54 when additional solvent is required for a given introduction stage for example. The production lines of the startup wells can also have monitoring devices for monitoring various parameters, such as composition, pressure, temperature, and the like. Figure 10 illustrates two well pads 52, each having multiple well pairs 21, which are serviced by a single integrated system for solvent injection, production and separation. By associating a surface system with multiple wells, which can be part of several well pads 52, the surface equipment can be leveraged for multiple cyclic startup processes that may be occurring at the same time.
Liquid solvent implementations

[00119] In some implementations, the liquid solvent introduced during the introduction stage can have a predetermined volume based on various factors.
The predetermined volume can be determined and/or calculated by analyzing the volume of the various sections of the solvent startup well and relevant volumes of the bitumen reservoir. Non-limiting examples of the predetermined volume can be the volume required to substantially fill the horizontal startup section, or the volume required to substantially fill the downstream region when the packer assembly is mounted within the solvent startup well. The predetermined volume can take into consideration the wellbore dimensions, the volume of the solid components in the wellbore, as well as solvent properties in terms of volume dependence on temperature, pressure, and composition. The predetermined volume can also include the bitumen depleted volume in the reservoir, particularly for later cycles, and can be determined based on measurements and monitoring of bitumen content of the startup production fluid. The depleted volume in the surrounding reservoir can be determined and tracked for each cycle to aim in the determination of the solvent volume of a subsequent cycle.

[00120] It should be understood that the introduction of a predetermined volume of liquid solvent can increase effectiveness and efficiency of the startup process and reduce unnecessary loss of liquid solvent. In addition, the soaking stage of any given cycle can begin once the predetermined volume of liquid solvent has been introduced during the introduction stage of that cycle. Solvent inventory can also be efficiently managed by using determined volumes of solvent.

[00121] Referring to Figures 1, 9 and 10 the liquid solvent can be stored at surface within a solvent supply source 54, such as a container, a tank or a tanker for example, prior to the introduction stage of a given cycle. It should be understood that the tubing string 32 or other piping can be fluidly connected to the solvent supply source 54 to provide liquid solvent from the supply source 54 to within the solvent startup well.
It is appreciated that following a separation stage, the recovered liquid solvent can be transferred to the solvent supply source 54 prior to initiating a subsequent cycle. The recovered bitumen component can be stored within a bitumen holding tank 56 (Figures 1 and 10) or directly supplied by pipeline for additional processing (Figure 9).

[00122] In some implementations, the liquid solvent can have a low density to facilitate infiltration within the reservoir and reduce the viscosity of the bitumen contained therein. The low solvent density can cause the liquid solvent to tend to move upwardly relative to the bitumen, which has a greater density and would mobilize and flow downwardly by gravity. Due to the tendency of low density solvent to displace upwardly within the reservoir, introduction of the solvent via the underlying production well of the well pair may be advantageous to mobilizing the interwell region. In addition, solvent selection can be coordinated with the well that is used as the startup well.
For example, a lower density solvent can be preferred for introduction via the production well to leverage density and gravity effects, while a higher density solvent may be preferred for introduction via the injection well. In one possible implementation, multiple different solvents can be used, and different solvents can be used in different wells of a given pair.
The upward flow of the low density liquid solvent can also influence the separation stage of the startup process in a manner that will be further described below.

[00123] The solvent is maintained in liquid phase during introduction, soaking, and production. During separation, the solvent can be flashed as part of the separation method, in which case the solvent would be cooled so as to be liquid prior to reintroduction in a following cycle. Regarding the liquid phase of the solvent, it should be noted that there can be relatively small amounts of solvent vapour present depending on the operating conditions and the vapour pressure of the solvent used in the process.
However, the operating conditions are selected so as to be well below the solvent's boiling point, for example, the solvent can be subcooled by about 10-20 C below flashing conditions so as to ensure having the solvent in liquid phase, preferably during each stage of the process.
Furthermore, the solvent can be selected by analyzing the parameters of the reservoir. In some embodiments, the reservoir pressure can be between about 500 kPa and about 800 kPa, and the reservoir can have a temperature substantially around 7-8 C.
Therefore, the solvent can be selected so as to be in liquid phase in the aforementioned conditions.

[00124] Various different types of solvents can be used. Non-limiting examples of the liquid solvent can comprise dimethyl ether (DME), methyl ethyl ketone (MEK), toluene, xylene, diesel, hexane, heptane and/or naphtha. Other ethers and ketones with relatively low density, high bitumen solubility, and good separability from bitumen can also be used.

Cyclic patterns and operations & end of startup process

[00125] The startup process can include various implementations of cyclic patterns for mobilizing bitumen within the interwell region, some of which were touched on above.
The solvent startup well can be selected from the injection and/or production wells that form the well pair. During some implementations of the startup process, both wells in the pair can be used as solvent startup wells, and they can be alternated or synchronized in terms of the stages and cycles of operation. In other words, a first cycle can be initiated via the injection well, and a second cycle can be initiated via the production well, either during or after the first cycle is completed, as will be explained below. In other implementations, the solvent startup well can be a single well, either the injection or production well, for the entire startup process.

[00126] Referring to Figures 7 through 7d, the solvent startup well 30 can be the injection well 22 for each cycle of the startup process. It should be understood that the injection well 22 can include the packer assembly 40, the ESP 46 (Figure 5) or other production pump, the tubing string, and/or any other component related to the bitumen mobilization operation of the startup process. It should also be understood that the interwell region 26 is located below the horizontal injection section 22h, and that the liquid solvent thus penetrates that region of the reservoir from above (i.e. from the horizontal injection section).

[00127] During the startup process, a first introduction stage can be initiated within the injection well 22, followed by the soaking stage (Figure 7a). Once the soaking period has elapsed, the production stage is initiated, and the liquid solvent is recovered from the injection well 22, and a portion of the bitumen is mobilized (Figure7b). If necessary, the liquid solvent is separated at surface and reintroduced in a subsequent introduction stage (Figure 7c), followed yet again by soaking and production stages, effectively mobilizing a greater portion of bitumen until a flow of bitumen reaches the production well 24 (Figure 7d). It should be understood that the cycle is thus repeated until a desired mobilization or bitumen depletion or that fluid communication has been established between the injection and production wells 22, 24.

[00128] Referring to Figures 8a to 8e, the solvent startup well 30 can be alternated between the injection well 22 and the production well 24 during the startup process. For example, a first cycle can be completed via the injection well 22 (Figure 8a), and a second cycle can be completed via the production well 24 (Figure 8b), and so on until fluid communication is established between the wells (Figure 8e). Thus, once the solvent is recovered from one well and ready for reintroduction, it is introduced via the other well.
This alternating cyclic pattern can then be reproduced a number of iterations.
It is noted that more than one cycle in a row can be completed via one of the wells before alternating to the other well of the well pair. Additionally, the startup process equipment (e.g., packer assembly, pumps, tubing string, piping, etc.) can be provided in both wells of the pair to facilitate such operations.

[00129] In some implementations, both wells in a pair can be operated as solvent startup wells and the cycles of the two wells can be offset and thus the same stages are not necessarily operated at the same time for the two wells. For example, the introduction stage of any given cycle for one well can be initiated during the soaking stage of a previous first cycle of the other well. The cycles can be coordinated such that the separator only has to handle production fluid from one of the well at a time, which can facilitate efficient equipment utilization. As another example, the introduction stage of a cycle for one well can be initiated during the production or separation stage of a previous cycle for the other well. In some alternative implementations, cycles, and/or the same stages, of the startup process can be conducted via both wells simultaneously.

[00130] As described above, the liquid solvent can have low density, especially when compared to the bitumen contained within the reservoir, and can infiltrate the reservoir via gravity and/or diffusion based mechanisms. In some implementations, the liquid solvent can be generally clear (i.e., without dark coloration) when introduced within the solvent startup well to initiate a cycle of the startup process. As the liquid solvent penetrates the reservoir, the bitumen is diluted/solubilised into the liquid solvent, which reduces the viscosity of the bitumen.

[00131] It should be noted that, during the initial cycles of the startup process (e.g., the first and second cycles), solvent penetration within the reservoir can be limited due to the high density and low initial mobility of the bitumen. This can result in the startup production fluid having low bitumen concentrations during these cycles, as described above. However, in later cycles, solvent penetration within the reservoir can be facilitated because of the mobilization and/or partial removal of the bitumen. It should also be noted that some of the liquid solvent can remain within the reservoir after a given cycle (i.e., the solvent was not produced back during the production stage of that cycle), and can thus maintain treatment of the bitumen while soaking in the reservoir. Therefore, during a subsequent cycle, solvent penetration can be facilitated as a result of the "pre-treatment"
of bitumen due to leftover liquid solvent from a previous cycle. Therefore, later cycles can require greater volumes of liquid solvent during the introduction stage since the bitumen is mobilized and/or removed, thus leaving pockets needing to be filled (e.g., pore space between solid minerals) within the reservoir to reach the remaining bitumen.
In some implementations, the startup process can be deemed completed once the volume of liquid solvent required during a given introduction stage is at or above an introduction threshold.
For example, when the volume of liquid solvent required for introduction has doubled since the first introduction cycle, the introduction threshold has been reached, and the startup process is completed. It should be understood that other methods of determining the introduction threshold can be implemented.

[00132] As the bitumen mobilizes, the startup production fluid can include a certain bitumen concentration, and is thus produced as a colored fluid, such as dark brown or black for example. Moreover, the bitumen can flow downwardly toward the horizontal production section under the effect of gravity. Referring back to Figure 3, the startup production fluid can include a bitumen concentration having a startup completion threshold. The completion threshold can mark the end of the startup process 10e or the end of the solvent assisted process, as the bitumen within the reservoir has been sufficiently mobilized to be produced back consistently and in non-negligible concentrations. Therefore, once the startup production fluid is at or above the production threshold, the startup process can be replaced by regular bitumen recovery operations.
Alternatively, the startup process can be deemed completed once a predetermined volume of the reservoir has been extracted (i.e., depleted of bitumen). For example, the predetermined volume can be the volume substantially corresponding to the interwell region, or the volume defined by a distance around the injection and production wells such as 0.5m, 0.75m, lm, 1.5m, 2m or 2.5m, among other possibilities. The distance from the startup well can define a radius of a generally cylindrical volume around the well. The volume can also be determined by subtracting the volume within the well itself so that the volume is a cylinder with a hollow small cylinder along its center axis. Other more complex volume determinations are also possible, where certain reservoir and fluid dynamics factors are taken into consideration to determine the volume. In some implementations, the predetermined volume can be determined/monitored via analysis of the wellbore and surrounding reservoir. The depletion volume may be determined before initiating the startup process or may be determined at some point during startup operations.

[00133] In some scenarios, the startup process can be implemented to reduce viscosity of the bitumen, while fluid communication between the wells of a given pair can be established using a subsequent method. In other words, the liquid-based startup process can be a conditioning or pre-treating phase which can be followed and/or completed using other startup methods or techniques, such as steam circulation for example. Transitioning from the startup process to conventional/normal startup operations can require the introduction of a mobilizing fluid (e.g., steam, solvent, steam-solvent co-injection) via the injection well, and the initialization of traditional production operations via the production well.

[00134] It should be noted that the solvent based techniques described herein can be used as the sole or primary startup process prior to ramping up to normal production, or can be combined simultaneously or serially with other startup methods. For example, the cyclic solvent startup process can be performed after an earlier pre-treatment of the reservoir that may use the injection of chemical compounds that can facilitate bitumen mobilization. The cyclic solvent startup process can be performed in conjunction with a radiofrequency (RF) based startup technique where RF energy is used to heat and mobilize bitumen in the reservoir; an RF generating device could be deployed in the solvent startup well or in an adjacent or proximate well and can be used simultaneously or serially with the cyclic solvent startup process. The cyclic solvent startup process could also be followed by a further startup method that employs other mobilizing fluids and/or heating techniques (e.g., steam circulation, bullheading, use of different solvents using different injection, circulation and/or soaking strategies, and so on).

Claims

1. An in situ startup process for mobilizing bitumen between a gravity drainage well pair located in a bitumen containing reservoir, the well pair comprising an injection well having a horizontal injection section and a production well having a horizontal production section located below the horizontal injection section, the horizontal injection section and horizontal production section defining an interwell region therebetween, the process comprising:
in an introduction stage, introducing a predetermined volume of liquid solvent via a solvent startup well selected from the injection and production wells, at an introduction pressure and introduction temperature configured to maintain the liquid solvent in liquid phase within the solvent startup well and the reservoir, wherein the introduction pressure is at or above an initial reservoir pressure of the interwell region and below a fracturing pressure thereof;
in a soaking stage, ceasing introduction of the liquid solvent and allowing the liquid solvent to soak within the reservoir for a soaking period in order to mobilize bitumen in the interwell region;
in a production stage, producing fluids from the solvent startup well to recover a startup production fluid comprising bitumen and liquid solvent;
in a surface separation stage, separating at surface the startup production fluid into a solvent depleted bitumen component and a recovered solvent component; and cyclically repeating the introduction stage, the soaking stage, the production stage and the surface separation stage to mobilize bitumen located in the interwell region.

2. The startup process according to claim 1, wherein the recovered solvent component is reintroduced in the solvent startup well in a subsequent introduction stage.

3. The startup process according to claim 1 or 2, wherein the liquid solvent is stored at surface within a solvent supply source, and wherein the liquid solvent is introduced within the solvent startup well via a tubing string.

4. The startup process according to claim 3, wherein the solvent startup well comprises a horizontal startup section, and wherein the tubing string is coupled to the solvent supply source and is configured to transfer liquid solvent within the horizontal startup section.

5. The startup process according to claim 4, wherein the solvent startup well comprises a vertical section, and wherein once the horizontal startup section is filled with liquid solvent, displacement fluid is introduced within the vertical section to increase pressure on the liquid solvent.

6. The startup process according to claim 4 or 5, wherein the solvent startup well comprises a liner extending along at least a portion of the horizontal startup section, and wherein the tubing string extends within the liner and defines an annulus region therebetween.

7. The startup process according to claim 6, wherein the liner is slotted to allow liquid solvent to exit the horizontal startup section and infiltrate the reservoir.

8. The startup process according to claim 6 or 7, wherein the solvent startup well comprises a packer assembly mounted within the annulus region and defining an upstream region and a downstream region, the packer assembly being configured to prevent fluid communication between the upstream and downstream regions.

9. The startup process according to claim 8, wherein the solvent startup well comprises a transition section connecting the vertical section and horizontal startup section, and wherein the downstream region comprises at least a portion of the horizontal startup section, and the upstream region comprises at least the vertical section and the transition section.

10. The startup process according to claim 8 or 9, wherein the packer assembly is movably mounted within the annulus region to adjust a length of the downstream region.

11. The startup process according to any one of claims 8 to 10, wherein the tubing string is configured to extend through the packer assembly to introduce liquid solvent within the downstream region.

12. The startup process according to any one of claims 8 to 11, wherein the solvent startup well comprises a pump located within the downstream region, and wherein the production stage is enabled by the pump.

13. The startup process according to claim 12, wherein the pump is an electrical submersible pump (ESP).

14. The startup process according to any one of claims 8 to 13, wherein during an initial introduction stage, the predetermined volume of liquid solvent exceeds an internal volume of the tubing string extending within the downstream region added to the volume of the annulus region located in the downstream region.

15. The startup process according to any one of claims 1 to 14, wherein during a given introduction stage, the predetermined volume of liquid solvent is greater than the predetermined volume of liquid solvent of a previous cycle by an amount determined based at least in part by monitoring bitumen removal from the reservoir during the previous cycle.

16. The startup process according to any one of claims 1 to 15, wherein the introduction pressure is between about 10 kPa and about 100 kPa above the initial reservoir pressure.

17. The startup process according to any one of claims 1 to 16, wherein the soaking stage is initiated once the predetermined volume of liquid solvent has been introduced.

18. The startup process according to any one of claims 1 to 17, wherein the soaking period substantially corresponds to the amount of time required for the pressure within the solvent startup well to stabilize.

19. The startup process according to any one of claims 1 to 18, wherein the production stage is initiated once the soaking period has elapsed.

20. The startup process according to any one of claims 1 to 19, wherein during the production stage, the startup production fluid is produced via a sub-surface pump.

21. The startup process according to any one of claims 1 to 20, wherein during the surface separation stage, the startup production fluid is separated via a separator.

22. The startup process according to claim 21, wherein the separator is a flash separator.

23. The startup process according to claim 21, wherein the separator is a centrifugal separator.

24. The startup process according to any one of claims 1 to 23, wherein during the surface separation stage, only a portion of the startup production fluid is separated into the solvent depleted bitumen component and the recovered solvent component.

25. The startup process according to claim 24, wherein the recovered solvent component is mixed with substantially pure liquid solvent prior to reintroduction.

26. The startup process according to any one of claims 1 to 25, wherein during the surface separation stage, the startup production fluid is subjected to gas removal, water removal, and/or solvent make-up.

27. The startup process according to any one of claims 1 to 26, wherein the startup production fluid comprises a bitumen concentration, and wherein the surface separation stage is initiated if the bitumen concentration is at or above a separation threshold.

28. The startup process according to any one of claims 1 to 27, wherein the liquid solvent infiltrates the reservoir via gravity and/or diffusion-based mechanisms.

29. The startup process according to any one of claims 1 to 28, wherein the liquid solvent comprises at least one of dimethyl ether, methyl ethyl ketone, toluene, xylene, diesel, butane, pentane, hexane, heptane and naphtha.

30. The startup process according to any one of claims 1 to 29, wherein the solvent startup well is alternated between the injection well and production well after each cycle.

31. The startup process according to any one of claims 1 to 30, wherein the solvent startup well is alternated between the injection well and production well after a plurality of cycles.

32. The startup process according to claim 30 or 31, wherein the subsequent introduction stage for one startup well is initiated during the soaking stage of a previous cycle of the other startup well.

33. The startup process according to claim 30 or 31, wherein the subsequent introduction stage for one startup well is initiated during the production stage of a previous cycle of the other startup well.

34. The startup process according to claim 30 or 31, wherein the subsequent introduction stage for one startup well is initiated during the surface separation stage of a previous cycle of the other startup well.

35. The startup process according to any one of claims 1 to 29, wherein both the injection well and the production well are operated as solvent startup wells simultaneously.

36. A startup process for mobilizing bitumen surrounding a well positioned in a bitumen containing reservoir, the process comprising:
in an introduction stage, introducing liquid solvent within the well, the liquid solvent having introduction parameters configured to maintain the liquid solvent in liquid phase within the well system and the reservoir;
in a soaking stage, ceasing introduction of the liquid solvent, and allowing the liquid solvent to soak within the well and the reservoir for a soaking period;
in a production stage, producing fluids from the solvent startup well to recover a startup production fluid comprising bitumen and liquid solvent;
in a surface separation stage, separating at surface the startup production fluid into a solvent depleted bitumen component and a recovered solvent component; and cyclically repeating the introduction stage, soaking stage, production stage and surface separation stage to mobilize the bitumen.

37. The startup process according to claim 36, wherein the recovered solvent component is reintroduced in the well in a subsequent introduction stage.

38. The startup process according to claim 36 or 37, wherein during each introduction stage, a predetermined volume of liquid solvent is introduced within the well.

39. The startup process according to anyone of claims 36 to 38, wherein the well is a solvent startup well, and the liquid solvent is stored at surface within a solvent supply source, and wherein the liquid solvent is introduced within the solvent startup well via a tubing string.

40. The startup process according to claim 39, wherein the solvent startup well comprises a horizontal startup section, and wherein the tubing string is coupled to the solvent supply source and is configured to transfer liquid solvent within the horizontal startup section.

41. The startup process according to claim 40, wherein the solvent startup well comprises a vertical section, and wherein once the horizontal startup section is filled with liquid solvent, displacement fluid is introduced within the vertical section to increase pressure on the liquid solvent.

42. The startup process according to claim 40 or 41, wherein the solvent startup well comprises a liner extending along at least a portion of the horizontal startup section, and wherein the tubing string extends within the liner and defines an annulus region therebetween.

43. The startup process according to claim 42, wherein the liner is slotted to allow liquid solvent to exit the horizontal startup section and infiltrate the reservoir.

44. The startup process according to claim 42 or 43, wherein the solvent startup well comprises a packer assembly mounted within the annulus region and defining an upstream region and a downstream region, the packer assembly being configured to prevent fluid communication between the upstream and downstream regions.

45. The startup process according to claim 44, wherein the solvent startup well comprises a transition section connecting the vertical section and horizontal startup section, and wherein the downstream region comprises at least a portion of the horizontal startup section, and the upstream region comprises at least the vertical section and the transition section.

46. The startup process according to claim 44 or 45, wherein the packer assembly is movably mounted within the annulus region to adjust a length of the downstream region.

47. The startup process according to any one of claims 44 to 46, wherein the tubing string is configured to extend through the packer assembly to introduce liquid solvent within the downstream region.

48. The startup process according to claim any one of claims 44 to 47 wherein the solvent startup well comprises a pump located within the downstream region, and wherein the production stage is enabled by the pump.

49. The startup process according to claim 48, wherein the pump is an electrical submersible pump (ESP).

50. The startup process according to claim 49, wherein during an initial introduction stage, the predetermined volume of liquid solvent exceeds an internal volume of the tubing string extending within the downstream region added to the volume of the annulus region located in the downstream region.

51. The startup process according to any one of claims 38 to 50, wherein during a given introduction stage, the predetermined volume of liquid solvent is greater than the predetermined volume of liquid solvent of a previous cycle by an amount determined based at least in part by monitoring bitumen removal from the reservoir during the previous cycle.

52. The startup process according to any one of claims 36 to 51, wherein the introduction parameters include an introduction temperature and an introduction pressure provided between about 10 kPa and about 100 kPa above an initial reservoir pressure.

53. The startup process according to any one of claims 38 to 52, wherein the soaking stage is initiated once the predetermined volume of liquid solvent has been introduced.

54. The startup process according to any one of claims 36 to 53, wherein the soaking period substantially corresponds to the amount of time required for the pressure within the well to stabilize.

55. The startup process according to any one of claims 36 to 54, wherein the production stage is initiated once the soaking period has elapsed.

56. The startup process according to any one of claims 36 to 55, wherein during the production stage, the startup production fluid is produced via a surface pump.

57. The startup process according to any one of claims 36 to 56, wherein during the surface separation stage, the startup production fluid is separated via a separator.

58. The startup process according to claim 57, wherein the separator is a flash separator.

59. The startup process according to claim 57, wherein the separator is a centrifugal separator.

60. The startup process according to any one of claims 36 to 59, wherein during the surface separation stage, only a portion of the startup production fluid is separated into the solvent depleted bitumen component and the recovered solvent component.

61. The startup process according to claim 60, wherein the recovered solvent component is mixed with substantially pure liquid solvent prior to reintroduction.

62. The startup process according to any one of claims 36 to 61, wherein during the surface separation stage, the startup production fluid is subjected to gas removal, water removal, and/or solvent make-up.

63. The startup process according to any one of claims 36 to 62, wherein the startup production fluid comprises a bitumen concentration, and wherein the surface separation stage is initiated if the bitumen concentration is at or above a separation threshold.

64. The startup process according to any one of claims 36 to 63, wherein the liquid solvent infiltrates the reservoir via gravity and/or diffusion-based mechanisms.

65. The startup process according to any one of claims 36 to 64, wherein the liquid solvent comprises at least one of dimethyl ether, methyl ethyl ketone, toluene, xylene, diesel, butane, pentane, hexane, heptane and naphtha.

66. The startup process according to any one of claims 39 to 65, wherein the solvent startup well is alternated between an injection well and a production well after each cycle.

67. The startup process according to any one of claims 39 to 65, wherein the solvent startup well is alternated between an injection well and a production well after a plurality of cycles.

68. The startup process according to claim 66 or 67, wherein the subsequent introduction stage for one startup well is initiated during the soaking stage of a previous cycle of the other startup well.

69. The startup process according to claim 66 or 67, wherein the subsequent introduction stage for one startup well is initiated during the production stage of a previous cycle of the other startup well.

70. The startup process according to claim 66 or 67, wherein the subsequent introduction stage for one startup well is initiated during the surface separation stage of a previous cycle of the other startup well.

71. The startup process according to any one of claims 39 to 65, wherein an injection well and a production well are operated as solvent startup wells simultaneously.

72. The startup process according to any one of claims 1 to 71, wherein the liquid solvent is maintained in liquid phase throughout the introduction stage, the soaking stage and the production stage for at least one cycle.

73. The startup process according to any one of claims 1 to 71, wherein the liquid solvent is maintained in liquid phase throughout the introduction stage, the soaking stage and the production stage for all cycles.