CA3060946C

CA3060946C - Co-injection of aromatic and paraffinic solvents during an in situ startup process

Info

Publication number: CA3060946C
Application number: CA3060946A
Authority: CA
Inventors: Tair Ibatullin; Hossein Aghabarati
Original assignee: Suncor Energy Inc
Current assignee: Suncor Energy Inc
Priority date: 2019-11-05
Filing date: 2019-11-05
Publication date: 2022-08-23
Anticipated expiration: 2039-11-05
Also published as: CA3060946A1

Abstract

ABSTRACT There is provided a startup process for mobilizing bitumen in an interwell region defined between an injection well and a production well located in a bitumen- containing reservoir. The startup process includes introducing a startup fluid that includes a non- = deasphalting mobilizing solvent and a deasphalting mobilizing solvent provided in a first proportion into the bitumen-containing reservoir via the injection well, recovering mobilized bitumen from the interwell region via the production well as a production fluid to form a bitumen-depleted region that enables fluid communication between the = injection well and the production well, and transitioning the startup fluid from the first proPortion to a second proportion, the second proportion having a reduced amount of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the first proportion. The first proportion of the startup fluid advantageously enables asphaltenes to remain substantially solubilized in the mobilized bitumen. CA 3060946 2019-11-05

Description

I
CO-INJECTION OF AROMATIC AND PARAFFINIC SOLVENTS DURING AN IN SITU
STARTUP PROCESS
TECHNICAL FIELD
[1] The technical field generally relates to startup processes for mobilizing bitumen contained in bitumen-bearing reservoirs, and more particularly to the use of startup fluids to enhance startup procedures of solvent-assisted recovery processes.
BACKGROUND

[2] There are various techniques for in situ recovery of heavy hydrocarbons, -such as heavy oil and/or bitumen, from heavy hydrocarbon-bearing reservoirs.
Some techniques are solvent-assisted recovery processes that employ a solvent to help mobilize the bitumen for recovery. Some solvent-assisted recovery processes can have similarities with conventional Steam-Assisted Gravity Drainage (SAG D), although solvent is injected into the heavy hydrocarbon-bearing reservoir instead or along with steam.

[3] In one solvent-assisted recovery process, a pair of horizontal wells including an upper injection well and a lower production well can be provided in the heavy hydrocarbon-bearing reservoir, which can be an oil sands reservoir. The region between the injection well and the production well, i.e., the interwell region, is characterized by various levels of hydrocarbon saturation and fluid mobility, and will generally include a region having a high saturation of hydrocarbons and a limited fluid mobility.
The general goal of the startup process is to increase the mobility of the hydrocarbons in the interwell region, for instance by warming the interwell region using various methods, such as using electric resistive heaters or providing steam circulation, and injecting a mobilizing fluid, such as solvent, into the hydrocarbon-bearing reservoir via the injection well.

[4] Once fluid communication is established in the region between the injection well and the production well, injection of mobilizing fluid can continue in order to promote growth of an extraction chamber in proximity of the injection well. The extraction chamber eventually extends upwardly and outwardly from the injection well within the reservoir as the mobilized hydrocarbons flow toward the production well mainly due to viscous forces and gravity forces. Over time, a production fluid including the mobilized hydrocarbons and a portion of the mobilizing fluid is recovered to the surface. The extraction chamber can be formed using various mobilizing fluids, such as steam, various hydrocarbon solvents, non-condensable gases, and combinations thereof.

[5] Various challenges still exist with regard to solvent-assisted recovery processes and there is a need for enhanced technologies.
SUMMARY

[6] In accordance with one aspect, there is provided a startup process for mobilizing bitumen in an interwell region, the interwell region being defined between a horizontal injection section of an injection well and a horizontal production section of a production well located below the horizontal injection section, the injection well and the production well being located in a bitumen-containing reservoir. The startup process comprises:
introducing a startup fluid comprising a non-deasphalting mobilizing solvent and a deasphalting mobilizing solvent into the bitumen-containing reservoir via the injection well, the non-deasphalting mobilizing solvent and the deasphalting mobilizing solvent being provided in a first stage proportion; recovering mobilized bitumen from the interwell region via the production well as a production fluid to form a bitumen-depleted region that enables fluid communication between the injection well and the production well; and transitioning the startup fluid from the first stage proportion to a second stage proportion, the second stage proportion having a reduced amount of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the first stage proportion; wherein at least the first stage proportion of the startup fluid enables asphaltenes to remain substantially solubilized in the mobilized bitumen.

[7] In some implementations, transitioning the startup fluid from the first stage proportion to the second stage proportion comprises a continuous transition.

[8] In some implementations, transitioning the startup fluid from the first stage proportion to the second stage proportion comprises a step transition.

[9] In some implementations, the second stage proportion enables the asphaltenes to remain substantially solubilized in the mobilized bitumen.

[10] In some implementations, the second stage proportion enables precipitation of at least a portion of the asphaltenes such that asphaltene precipitates are formed.

[11] In some implementations, the process further comprises transitioning the startup up fluid from the second stage proportion to a third stage proportion.

[12]. In some implementations, transitioning the startup fluid from the second stage proportion to the third stage proportion comprises a continuous transition.

[13] In some implementations, transitioning the startup fluid from the second stage proportion to the third stage proportion comprises a step transition.

[14] In some implementations, the third stage proportion has an increased amount of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the second stage proportion.

[15] In some implementations, the third stage proportion is substantially free of the deasphalting mobilizing solvent.

[16] In some implementations, the third stage proportion enables the asphaltenes to remain substantially solubilized in the mobilized bitumen.

[17] In some implementations, the process further comprises maintaining the startup fluid in the third stage proportion for a given period of time to resolubilize the asphaltene precipitates.

[18] In some implementations, the third stage proportion has a reduced amount of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the second stage proportion.

[19] In some implementations, maintaining the startup fluid in the third stage proportion and recovering the mobilized bitumen as the production fluid from the interwell region via the production well is performed substantially simultaneously.

[20] In some implementations, the third stage proportion allows precipitation of at least a portion of the asphaltenes.

[21] In some implementations, the startup fluid further comprises steam.

[22] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises vapourizing at least the non-deasphalting mobilizing solvent at surface to obtain a vapourized non-deasphalting mobilizing solvent; combining the vapourized non-deasphalting mobilizing solvent with the deasphalting mobilizing solvent to obtain a vapourized startup fluid; and injecting the vapourized startup fluid into the interwell region via the injection well.

[23] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises vapourizing the startup fluid at surface to obtain a vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.

[24] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises heating the startup fluid as the startup fluid travels along the injection well to obtain a vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.

[25] In some implementations, heating the startup fluid as the startup fluid travels along the injection well comprises providing electrically heating using one or more electric resistive heaters in the injection well.

[26] In some implementations, introducing the startup fluid into the bitumen-containing reservoir further comprises injecting the startup fluid via the production well prior to recovering the mobilized bitumen from the interwell region via the production well.

[27] In some implementations, introducing the startup fluid into the bitumen-containing reservoir further comprises injecting the startup fluid via the production well cyclically between periods of recovering the mobilized bitumen from the interwell region via the production well.

[28] In some implementations, at least the first stage proportion further enables formation of a startup chamber.

=

[29] In some implementations, recovering the mobilized bitumen via the production well and the formation of the startup chamber are performed substantially simultaneously.

[30] In some implementations, the process further comprises determining startup chamber size.

[31] In some implementations, transitioning the startup fluid from the first stage proportion to the second stage proportion or from the second stage proportion to the third proportion is performed when the startup chamber size has reached a given size.

[32] In some implementations, the process further comprises determining an.
amount of mobilized bitumen produced from the interwell region to assess bitumen de-saturation in the interwell region.

[33] In some implementations, when the amount of mobilized bitumen produced from the interwell region is above a given threshold, the first stage proportion is transitioned to the second stage proportion.

[34] In some implementations, the process further comprises monitoring a production variable related to recovering the production fluid.

[35] In some implementations, the production variable comprises a compositional characteristic of the production fluid.

[36] In some implementations, the compositional characteristic comprises a non-deasphalting mobilizing fluid concentration in the production fluid.

[37] In some implementations, the compositional characteristic of the production fluid cornprises a deasphalting mobilizing fluid concentration in the production fluid.

[38] In some implementations, the compositional characteristic of the production fluid comprises a bitumen concentration of the production fluid.

[39] In some implementations, the compositional characteristic of the production fluid comprises an asphaltene content of the production fluid.

[40] In some implementations, the compositional characteristic of the production fluid comprises an API gravity of the production fluid.

[41] In some implementations, in the first stage proportion, a ratio of non-deasphalting mobilizing solvent to deasphalting mobilizing solvent is above or equal to about 1:1.

[42] In some implementations, in the first stage proportion, a ratio of non-deasphalting mobilizing solvent to deasphalting mobilizing solvent is between 1:1 and 3:1.

[43] In some implementations, in the second stage proportion, the ratio of non-deasphalting mobilizing =solvent to deasphalting mobilizing solvent is below or equal to 1:1.

[44] In some implementations, in the first stage proportion, the ratio of non-deasphalting mobilizing solvent to deasphalting mobilizing solvent is between about 1:1 and about 1:3.

[45] In some implementations, wherein in the first stage proportion, the startup fluid comprises between about 30% and about 50% of the non-deasphalting mobilizing solvent and between about 50% and about 70% deasphalting mobilizing solvent.

[46] In some implementations, the non-deasphalting mobilizing fluid comprises an aromatic solvent.

[47] In some implementations, the aromatic solvent comprises toluene, diesel, xylene, or a combination thereof.

[48] In some implementations, the aromatic solvent comprises toluene.

[49] In some implementations, the aromatic solvent comprises diesel.

[50] In some implementations, the aromatic solvent comprises xylene.

[51] In some implementations, the deasphalting mobilizing fluid comprises an alkane solvent.
=

[52] In some implementations, the alkane solvent comprises propane, butane, pentane, hexane, heptane, condensate, or a mixture thereof.

[53] In some implementations, the alkane solvent comprises propane.
[64] In some implementations, the alkane solvent comprises butane.
[55] In some implementations, the alkane solvent comprises pentane.
[56] In some implementations, the alkane solvent comprises condensate.
[57] In some implementations, the process further comprises pre-heating the interwell region.
[58] In some implementations, pre-heating the interwell region comprises electrically heating using one or more electric resistive heaters in the injection well and/or the production well.
[59] In In some implementations, pre-heating the interwell region comprises circulating steam through the injection well and/or the production well.
[60] In some implementations, the process further comprises separating the production fluid to remove water and solids therefrom to obtain a solvent-rich fluid.
= [61] In some implementations, the process further comprises separating the solvent-rich fluid to recover at least a portion of the deasphalting mobilizing solvent and obtain a recycled deasphalting mobilizing solvent suitable for reuse in the startup fluid, and a mixed bitumen and non-deasphalting mobilizing solvent stream.
[62] In some implementations, the process further comprises separating the mixed bitumen and non-deasphalting mobilizing solvent stream to recover at least a portion of the non-deasphalting mobilizing solvent to obtain a recycled non-deasphalting mobilizing solvent suitable for reuse in the startup fluid.
[63] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled deasphalting mobilizing solvent as part of the startup fluid.

[64] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled non-deasphalting mobilizing solvent as part of the startup fluid.
[65] In accordance with another aspect, there is provided a startup process for mobilizing bitumen in an interwell region, the interwell region being defined between a horizontal injection section of an injection well and a horizontal production section of a production well located below the horizontal injection section, the injection well and the production well being located in a bitumen-containing reservoir. The startup process comprises introducing a startup fluid comprising a non-deasphalting mobilizing solvent and a deasphalting mobilizing solvent into the bitumen-containing reservoir, the startup fluid having a first composition that enables asphaltenes to remain substantially solubilized in mobilized bitumen; recovering the mobilized bitumen from the interwell region as a production fluid to form a bitumen-depleted region that enables fluid communication between the injection well and the production well;
transitioning the startup fluid from the first composition to a second composition, the second composition having a reduced amount of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the first composition.
[66] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises injecting the startup fluid via the injection well.
[67] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises injecting the startup fluid via the production well prior to recovering the mobilized bitumen from the interwell region via the production well.
[68] In some implementations, introducing the startup fluid into the bitumen-containing reservoir further comprises injecting the startup fluid via the production well cyclically between periods of recovering the mobilized bitumen from the interwell region via the production well.
[69] In some implementations, the process further comprises pre-heating the interwell region.

[70] In some implementations, pre-heating the interwell region comprises electrically heating using one or more electric resistive heaters in the injection well and/or the production well.
[71] In some implementations, pre-heating the interwell region comprises circulating steam through the injection well and/or the production well.
[72] In some implementations, transitioning the startup fluid from the first composition to the second composition comprises a continuous transition.
[73] In some implementations, transitioning the startup fluid from the first composition to the second composition comprises a step transition.
[74] In some implementations, in the second composition, the non-deasphalting mobilizing solvent is changed to a second non-deasphalting mobilizing solvent.
[75] In some implementations, in the second composition, the deasphalting mobilizing solvent is changed to a second deasphalting mobilizing solvent.
[76] In some implementations, the second composition enables the asphaltenes to remain substantially solubilized in the mobilized bitumen.
[77] In some implementations, the second composition allows precipitation of at least a portion of the asphaltenes such that asphaltene precipitates are formed.
[78] In some implementations, the process further comprises transitioning the startup up fluid from the second composition to a third composition.
[79] In some implementations, transitioning the startup fluid from the second composition to the third composition comprises a continuous transition.
[80] In some implementations, transitioning the startup fluid from the second composition to the third composition comprises a step transition.
[81] In some implementations, the third composition has an increased amount of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the second composition.

[82] In some implementations, the third composition is substantially free of the deasphalting mobilizing solvent.
[83] In some implementations, the third composition enables the asphaltenes to remain substantially solubilized in the mobilized bitumen.
[84] In some implementations, the process further comprises maintaining the startup fluid in the third composition for a given period of time to resolubilize the asphaltene precipitates.
[85] In some implementations, the third composition has a reduced amount of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the second composition.
[86] In some implementations, maintaining the startup fluid in the third composition and recovering the mobilized bitumen as the production fluid from the interwell region via the production well is performed substantially simultaneously.
[87] In some implementations, the third composition allows precipitation of at least a portion of the asphaltenes.
[88] In some implementations, the startup fluid further comprises steam.
[89] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises vapourizing at least the non-deasphalting mobilizing solvent at surface to obtain a vapourized non-deasphalting mobilizing solvent; combining the vapourized non-deasphalting mobilizing solvent with the deasphalting mobilizing solvent to obtain a vapourized startup fluid; and injecting the vapourized startup fluid into the interwell region via the injection well.
[90] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises vapourizing the startup fluid at surface to obtain the vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.

=
[91] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises heating the startup fluid as the startup fluid travels along the injection well to obtain a vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.
[92] In some implementations, heating the startup fluid as the startup fluid travels along the injection well comprises providing electrically heating using one or more electric resistive heaters in the injection well.
[93] In some implementations, at least the first composition further enables formation of a startup chamber.
[94] In some implementations, recovering the mobilized bitumen via the production well and the formation of the startup chamber are performed substantially simultaneously.
[95] In some implementations, the process further comprises determining startup chamber size.
[96] In some implementations, transitioning the startup fluid from the first composition to the second composition or from the second composition to the third composition is performed when the startup chamber size has reached a pre-determined given size.
[97] In some implementations, the process further comprises determining an amount of mobilized bitumen produced from the interwell region to assess bitumen de-saturation in the interwell region.
[98] In some implementations, when the amount of mobilized bitumen produced from the interwell region is above a given threshold, the first composition is transitioned to the second composition.
[99] In some implementations, the process further comprises monitoring a production variable related to recovering the production fluid.
[100] In some implementations, the production variable comprises a compositional characteristic of the production fluid.

[101] In some implementations, the compositional characteristic comprises a non-deasphalting mobilizing fluid concentration in the production fluid.
[102] In some implementations, the compositional characteristic of the production fluid comprises a deasphalting mobilizing fluid concentration in the production fluid.
[103] In some implementations, the compositional characteristic of the production fluid comprises a bitumen concentration of the production fluid.
[104] In some implementations, the compositional characteristic of the production fluid comprises an asphaltene content of the production fluid.
[105] In some implementations, the compositional characteristic of the production fluid comprises an API gravity of the production fluid.
[106] In some implementations, the non-deasphalting mobilizing fluid comprises an aromatic solvent.
[107] In some implementations, the aromatic solvent comprises toluene, diesel, xylene, or a combination thereof.
[108] In some implementations, the aromatic solvent comprises toluene.
[109] In some implementations, the aromatic solvent comprises diesel.
[110] In some implementations, the aromatic solvent comprises xylene.
[111] In some implementations, the deasphalting mobilizing fluid comprises an alkane solvent.
[112] In some implementations, the alkane solvent comprises propane, butane, pentane, hexane, heptane, condensate, or a mixture thereof.
[113] In some implementations, the alkane solvent comprises propane.
[114] In some implementations, the alkane solvent comprises butane.
[115] In some implementations, the alkane solvent comprises pentane.

[116] In some implementations, the alkane solvent comprises condensate.
[117] In some implementations, the process further comprises separating the production fluid to remove water and solids therefrom to obtain a solvent-rich fluid.
[118] In some implementations, the process further comprises separating the solvent-rich fluid to recover at least a portion of the deasphalting mobilizing solvent and obtain a recycled deasphalting mobilizing solvent suitable for reuse in the startup fluid, and a mixed bitumen and non-deasphalting mobilizing solvent stream.
[119] In some implementations, the process further comprises separating the mixed bitumen and non-deasphalting mobilizing solvent stream to recover at least a portion of the non-deasphalting mobilizing solvent to obtain a recycled non-deasphalting mobilizing solvent suitable for reuse in the startup fluid.
[120] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled deasphalting mobilizing solvent as part of the stailup fluid.
[121] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled non-deasphalting mobilizing solvent as part of the startup fluid.
[122] In accordance with another aspect, there is provided a startup process for mobilizing bitumen in an interwell region, the interwell region being defined between a horizontal injection section of an injection well and a horizontal production section of a production well located below the horizontal injection section, the injection well and the production well being located in a bitumen-containing reservoir. The startup process comprises introducing a startup fluid comprising a non-deasphalting mobilizing solvent and a deasphalting mobilizing solvent into the bitumen-containing reservoir, the startup fluid being provided with a proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent such that the startup fluid has a first functionality, the first functionality comprising enabling asphaltenes to remain substantially solubilized in mobilized bitumen; reducing the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent until the startup fluid reaches a second functionality; and recovering the mobilized bitumen from the interwell region as a production fluid to form a bitumen-depleted region that enables fluid communication between the injection well and the production well.
[123] In some implementations, the second functionality is a decreased solubility of asphaltenes in the mobilized bitumen.
[124] In some implementations, the decreased solubility of asphaltenes in the mobilized bitumen allows precipitation of at least a portion of the asphaltenes such that asphaltene precipitates are formed.
[125] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises injecting the startup fluid via the injection well.
[126] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises injecting the startup fluid via the production well prior to recovering the mobilized bitumen from the interwell region via the production well.
[127] In some implementations, introducing the startup fluid into the bitumen-containing reservoir further comprises injecting the startup fluid via the production well cyclically between periods of recovering the mobilized bitumen from the interwell region via the production well.
[128] In some implementations, the process further comprises pre-heating the interwell region.
[129] In some implementations, pre-heating the interwell region comprises electrically heating using one or more electric resistive heaters in the injection well and/or the production well.
[130] In some implementations, pre-heating the interwell region comprises circulating steam through the injection well and/or the production well.
[131] In some implementations, reducing the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent comprises a continuous transition.

[132] In some implementations, reducing the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent comprises a step transition.
[133] In some implementations, the startup fluid further comprises steam.
[134] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises vapourizing at least the non-deasphalting mobilizing solvent at surface to obtain a vapourized non-deasphalting mobilizing solvent; combining the vapourized non-deasphalting mobilizing solvent with the deasphalting mobilizing solvent to obtain a vapourized startup fluid; and injecting the vapourized startup fluid into the interwell region via the injection well.
[135] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises vapourizing the startup fluid at surface to obtain the vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.
[136] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises heating the startup fluid as the startup fluid travels along the injection well to obtain a vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.
[137] In some implementations, heating the startup fluid as the startup fluid travels along the injection well comprises , providing electrically heating using one or more electric resistive heaters in the injection well.
[138] In some implementations, at least the first functionality further comprises enabling formation of a startup chamber.
[139] In some implementations, recovering the mobilized bitumen via the production well and the formation of the startup chamber are performed substantially simultaneously.
[140] In some implementations, the process further comprises determining startup chamber size.

[141] In some implementations, the process further comprises determining an amount of mobilized bitumen produced from the interwell region to assess bitumen de-saturation in the interwell region.
[142] In some implementations, the process further comprises monitoring a production variable related to recovering the production fluid.
[143] In some implementations, the production variable comprises a compositional characteristic of the production fluid.
[144] In some implementations, the compositional characteristic comprises a non-deasphalting mobilizing fluid concentration in the production fluid.
[145] In some implementations, the compositional characteristic of the production fluid comprises a deasphalting mobilizing fluid concentration in the production fluid.
[146] In some implementations, the compositional characteristic of the production fluid comprises a bitumen concentration of the production fluid.
[147] In some implementations, the compositional characteristic of the production fluid comprises an asphaltene content of the production fluid.
[148] In some implementations, the compositional characteristic of the production fluid comprises an API gravity of the production fluid.
[149] In some implementations, the non-deasphalting mobilizing fluid comprises an aromatic solvent.
[150] In some implementations, the aromatic solvent comprises toluene, diesel, xylene, or a combination thereof.
[151] In some implementations, the aromatic solvent comprises toluene.
[152] In some implementations, the aromatic solvent comprises diesel.
[153] In some implementations, the aromatic solvent comprises xylene.

[154] In some implementations, the deasphalting mobilizing solvent comprises an alkane solvent.
[155] In some implementations, the alkane solvent comprises propane, butane, pentane, hexane, heptane, condensate, or a mixture thereof.
[156] In some implementations, the alkane solvent comprises propane.
[157] In some implementations, the alkane solvent comprises butane.
[158] In some implementations, the alkane solvent comprises pentane.
[159] In some implementations, the alkane solvent comprises condensate.
[160] In some implementations, the process further comprises separating the production fluid to remove water and solids therefrom to obtain a solvent-rich fluid.
[161] In some implementations, the process further comprises separating the solvent-rich fluid to recover at least a portion of the deasphalting mobilizing solvent and obtain a recycled deasphalting mobilizing solvent suitable for reuse in the startup fluid, and a mixed bitumen and non-deasphalting mobilizing solvent stream.
[162] In some implementations, the process further comprises separating the mixed bitumen and non-deasphalting mobilizing solvent stream to recover at least a portion of the non-deasphalting mobilizing solvent to obtain a recycled non-deasphalting mobilizing solvent suitable for reuse in the startup fluid.
[163] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled deasphalting mobilizing solvent as part of the startup fluid.
[164] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled non-deasphalting mobilizing solvent as part of the startup fluid.
[165] In accordance with another aspect, there is provided a startup process for mobilizing bitumen in an interwell region, the interwell region being defined between a horizontal injection section of an injection well and a horizontal production section of a production well located below the horizontal injection section, the injection well and the production well being located in a bitumen-containing reservoir. The startup process comprises introducing a startup fluid comprising at least a non-deasphalting mobilizing solvent in vapour phase into the bitumen-containing reservoir, the startup fluid having a first functionality; recovering mobilized bitumen from the interwell region as a production fluid to form a bitumen-depleted region that enables fluid communication between the injection well and the production well; and transitioning the startup fluid from the first functionality to a second functionality, comprising combining the non-deasphalting mobilizing solvent with a deasphalting mobilizing solvent; wherein the first functionality of the startup fluid comprises a formation of a startup chamber around the injection well.
[166] In some implementations, transitioning the startup fluid from the first functionality to the second functionality comprises a continuous transition.
[167] In some implementations, transitioning the startup fluid from the first functionality to the second functionality comprises a step transition.
[168] In some implementations, the second functionality is a decreased solubility of asphaltenes in the mobilized bitumen.
[169] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises injecting the startup fluid via the injection well.
[170] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises injecting the startup fluid via the production well prior to recovering the mobilized bitumen from the interwell region via the production well.
[171] In some implementations, introducing the startup fluid into the bitumen-containing reservoir further comprises injecting the startup fluid via the production well cyclically between periods of recovering the mobilized bitumen from the interwell region via the production well.
[172] In some implementations, the process further comprises pre-heating the interwell region.

[173] In some implementations, pre-heating the interwell region comprises electrically heating using one or more electric resistive heaters in the injection well and/or the production well.
[174] In some implementations, pre-heating the interwell region comprises circulating steam through the injection well and/or the production well.
[175] In some implementations, the startup fluid further comprises steam.
[176] In some implementations, introducing the startup fluid having the first functionality into the bitumen-containing reservoir in vapour phase comprises vapourizing the at least the non-deasphalting mobilizing solvent at surface to obtain a vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.
[177] In some implementations, introducing the startup fluid having the first functionality into the bitumen-containing reservoir comprises heating the startup fluid as the startup fluid travels along the injection well to obtain a vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.
[178] In some implementations, heating the startup fluid as the startup fluid travels along the injection well comprises providing electrically heating using one or more electric resistive heaters in the injection well.
[179] In some implementations, recovering the mobilized bitumen via the production ' well and the formation of the startup chamber are performed substantially simultaneously.
[180] In some implementations, the process further comprises transitioning the startup fluid from the second functionality to a third functionality, wherein the startup fluid having the third functionality has a reduced amount of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the startup fluid having the second functionality.
[181] In some implementations, the process further comprises determining startup chamber size.

[182] In some implementations, the process further comprises determining an amount of mobilized bitumen produced from the interwell region to assess bitumen de-saturation in the interwell region.
[183] In some implementations, the process further comprises monitoring a production variable related to recovering the production fluid.
[184] In some implementations, the production variable comprises a compositional characteristic of the production fluid.
[185] In some implementations, the compositional characteristic comprises a non-deasphalting mobilizing fluid concentration in the production fluid.
[186] In some implementations, the compositional characteristic of the production fluid comprises a deasphalting mobilizing fluid concentration in the production fluid.
[187] In some implementations, the compositional characteristic of the production fluid comprises a bitumen concentration of the production fluid.
[188] In some implementations, the compositional characteristic of the production fluid comprises an asphaltene content of the production fluid.
[189] In some implementations, the compositional characteristic of the production fluid comprises an API gravity of the production fluid.
[190] In some implementations, the non-deasphalting mobilizing solvent comprises an aromatic solvent.
[191] In some implementations, the aromatic solvent comprises toluene, diesel, xylene, or a combination thereof.
[192] In some implementations, the aromatic solvent comprises toluene.
[193] In some implementations, the aromatic solvent comprises xylene.
[194] In some implementations, the deasphalting mobilizing fluid comprises an alkane solvent.

[195] In some implementations, the alkane solvent comprises propane, butane, pentane, hexane, heptane, condensate, or a mixture thereof.
[196] In some implementations, the alkane solvent comprises propane.
[197] In some implementations, the alkane solvent comprises butane.
[198] In some implementations, the alkane solvent comprises pentane.
[199] In some implementations, the alkane solvent comprises condensate.
[200] In some implementations, the process further comprises separating the production fluid to remove water and solids therefrom to obtain a solvent-rich fluid.
[201] In some implementations, the process further comprises separating the solvent-rich fluid to recover at least a portion of the deasphalting mobilizing solvent and obtain a recycled deasphalting mobilizing solvent suitable for reuse in the startup fluid, and a mixed bitumen and non-deasphalting mobilizing solvent stream.
[202] In some implementations, the process further comprises separating the mixed bitumen and non-deasphalting mobilizing solvent stream to recover at least a portion of the non-deasphalting mobilizing solvent to obtain a recycled non-deasphalting mobilizing solvent suitable for reuse in the startup fluid.
[203] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled non-deasphalting mobilizing solvent as part of the startup fluid.
[204] In accordance with another aspect, there is provided a startup process for mobilizing bitumen in an interwell region, the interwell region being defined between a horizontal injection section of an injection well and a horizontal production section of a production well located below the horizontal injection section, the injection well and the =
production well being located in a bitumen-containing reservoir. The startup process comprises introducing a startup fluid comprising a non-deasphalting mobilizing solvent and a deasphalting mobilizing solvent into the bitumen-containing reservoir via the injection well, the non-deasphalting mobilizing solvent and the deasphalting mobilizing =CA 3060946 2019-11-05 solvent being provided in a first stage proportion; recovering mobilized bitumen from the interwell region via the production well to form a bitumen-depleted region that enables fluid communication between the injection well and the production well; and transitioning the startup fluid from the first stage proportion to a second stage proportion, the second stage proportion having a reduced amount of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the first stage proportion.
[205] In some implementations, transitioning the startup fluid from the first stage proportion to the second stage proportion comprises a continuous transition.
[206] In some implementations, transitioning the startup fluid from the first stage proportion to the second stage proportion comprises a step transition.
[207] In some implementations, the second stage proportion enables precipitation of at least a portion of the asphaltenes such that asphaltene precipitates are formed.
[208] In some implementations, the process further comprises, following the transitioning of the startup fluid to the second stage proportion: halting injection of the deasphalting mobilizing solvent; injecting the non-deasphalting solvent; and shutting in the well for a given period of time to solubilize the asphaltene precipitates.
BRIEF DESCRIPTION OF THE DRAWINGS
[209] Figure 1 is a schematic representation of a well pair during a startup process, the well pair including an injection well and a production well located in a hydrocarbon-bearing reservoir, wherein a startup fluid is injected into the hydrocarbon-bearing reservoir via the injection well, including a representation of a zone comprising mobilized bitumen.
[210] Figure 2 is a schematic graph showing example proportions of a two-component startup fluid for use during a startup process and in transition to normal recovery operations.
[211] Figure 3 is a schematic graph showing example proportions of a two-component startup fluid for use during a startup process and in transition to a normal recovery operations.

[212] Figure 4 is a schematic graph showing example concentrations of a non-deasphalting mobilizing solvent and deasphalting mobilizing solvent as part of a multicomponent startup fluid that has at least two components for use during a startup process.
[213] Figure 5 is another schematic graph showing example concentrations of a non-deasphalting mobilizing solvent as part of an at least two-component startup fluid for use during a startup process.
[214] Figure 6 is another schematic graph showing example concentrations of a non-deasphalting mobilizing solvent as part of an at least two-component startup fluid for use during a startup process.
[215] Figure 7 is another schematic graph showing example concentrations of a non-deasphalting mobilizing solvent as part of an at least two-component startup fluid for use during a startup process.
= [216] Figure 8 is a flow diagram of a process for treating a production fluid recovered from a solvent-assisted recovery process using a startup fluid that includes a non-deasphalting mobilizing solvent and a deasphalting mobilizing solvent.
DETAILED DESCRIPTION
[217] Techniques described herein relate to startup processes for mobilizing bitumen contained in a bitumen-bearing reservoir, and concomitant development of a startup chamber, in the context of in situ bitumen recovery operations. The startup process includes at least two stages during which a startup fluid is injected into the reservoir, the startup fluid having a variable composition, for instance depending of the stage of the startup process.
[218] = The initial stage of the startup process includes introducing the startup fluid in vapour phase into the reservoir, where the startup fluid is initially formulated as a non-deasphalting composition that can include a non-deasphalting mobilizing solvent and a deasphalting mobilizing solvent in a first stage proportion. The first stage proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent in =CA 3060946 2019-11-05 the startup fluid enables mobilization of bitumen while avoiding precipitation of asphaltenes contained in the bitumen within the reservoir. In a subsequent stage, the first stage proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent is transitioned to a second proportion. The transition from the first stage proportion to the second stage proportion can be achieved, for instance, by reducing or ramping-down the proportion or amount of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent. For example, the ratio or volume percentage of the non-deasphalting mobilizing solvent can be decreased in the startup fluid either continuously or using one or more step changes. Using such a staged approach with an initial composition that does not precipitate asphaltenes, followed by a transition to compositions that can induce asphaltene precipitation can advantageously promote startup chamber growth during the startup process while .
mobilizing bitumen. The staged approach can also include stage(s) wherein either one of the non-deasphalting mobilizing solvent or the deasphalting mobilizing solvent is introduced into the subsurface formation.
[219] Optionally, the initial stage of the startup process can be preceded by at least one pre-heating step to subject the bitumen contained in the subsurface formation to various levels of pre-heating and facilitate its mobilization. The pre-heating can be performed for a certain period of time until the bitumen has reached a certain temperature, for example, at which point the first stage solvent fluid can be injected into the subsurface formation.
[220] In some implementations, the startup fluid injection phase of the startup process can be continued until the startup fluid is substantially free of non-deasphalting mobilizing solvent and the injected solvent vapour is substantially a deasphalting solvent. In other implementations, the startup process can include a stage when the non-deasphalting mobilizing solvent is no longer a component of the startup fluid.
As the startup process gradually transitions to normal operations, the startup chamber will evolve to become a mobilizing fluid chamber, and recovery of a production fluid that includes mobilized bitumen, water and solids will be continued. The mobilizing fluid chamber can be a chamber that includes steam, solvent or both, depending on the mobilizing fluid that is introduced into the subsurface formation during normal operations.

[221] A more detailed description of the startup process for use in the context of a solvent-assisted recovery process and associated implementations is provided below.
Startup process of an in situ bitumen recovery process [222] As mentioned above, the startup process described herein facilitates mobilization of bitumen contained in a subsurface formation and growth of a startup chamber by using a startup fluid as a mobilizing fluid , the startup fluid being formulated differently depending on the stage of the startup procedure during which it is injected, i.e., over the course of the startup procedure. The bitumen within the formation includes various hydrocarbon components, including heavier asphaltenes and lighter maltenes.
Mobilized bitumen can then be produced as production fluid from the subsurface formation during normal recovery operations that follow the startup process.
It should be understood that the startup process described herein can be implemented in the context of any suitable in situ recovery process adapted to produce mobilize bitumen from a subsurface formation, such as a Steam Assisted Gravity Drainage (SAGD) process or a solvent-assisted gravity drainage operation. A SAGD process uses steam alone as a mobilizing fluid for introduction in the subsurface formation, whereas a solvent-assisted gravity drainage operation generally uses a solvent, with or without steam, for introduction into the subsurface formation. Once the startup process is completed, normal recovery operations of the in situ recovery process can follow.
[2231 Figure 1 shows an implementation of the startup process in the context of an in situ recovery process that is carried out via a horizontal well pair 10 provided in the subsurface formation. The horizontal well pair 10 includes an injection well 12 overlying a production well 14. The injection well 12 and the production well 14 are generally parallel and separated by an interwell region 16. The injection well 10 includes a vertical portion 18 and a horizontal portion 20 extending from the vertical portion 14, and the production well 14 includes a vertical portion 22 and a horizontal portion 24 extending from the vertical portion 22.
[224] Still referring to Figure 1, the startup process includes injecting a startup fluid 26 as a mobilizing fluid into the subsurface formation. In the illustrated implementation, the startup fluid 26 is injected into the subsurface formation via a tubing string 28 inserted into the injection well 12. The injection well 12 generally includes a casing in its vertical portion 18, and a liner in its horizontal portion 20. The liner extends within the wellbore and can include injection ports such that, when the startup fluid 26 exits the tubing string 28, the startup fluid 26 can fill the horizontal portion 20 of the injection well 12 and penetrate into the subsurface formation through the injection ports.
Alternatively, the liner can also include a slotted portion or a screen portion that allows the startup fluid 26 to exit the injection well 12 and penetrate into the subsurface formation.
In some implementations, devices that can include straddle packers, inflatable packers, sleeves and/or coiled tubing can be used to influence the interval at which the startup fluid 26 is injected into the subsurface formation. The startup fluid 26 can also be injected via the production well 14. In some implementations, when the startup fluid 26 is injected via the production well 14, it can be done for instance at the beginning of the startup process when recovery of mobilized bitumen has not started yet, i.e., in implementations where the production well 14 is not yet used to recover mobilized bitumen. In other implementations, injection of the startup fluid 26 can also be done for given periods of time in between which mobilized bitumen recovery through the production well 14 can resume to sustain formation of a bitumen-depleted region and of the startup chamber. In yet other implementations, the startup fluid can be injected into the subsurface formation via a single well configuration that is operated in a cyclic mode.
[225] The startup fluid 26 can be injected into the subsurface formation as vapour.
The vaporization of the startup fluid 26 can occur at surface using conventional heating means. A heater string 30 can also be inserted in the injection well 12 to provide heat to the startup fluid 26 as it is being carried through the injection well 12 via the tubing string 28, either to vapourize the startup fluid 26 prior to exiting from the tubing string 28, or to maintain the startup fluid 26 in vapour phase prior to exiting from the tubing string 28 so that upon exiting the injection well 12, the startup fluid 26 is in vapour phase.
[226] In addition to vapourizing and/or maintaining the startup fluid 26 in vapour phase while the startup fluid 26 travels along the injection well 12, the heater string 30 can also provide heat to the interwell region 16, for instance to pre-heat the bitumen prior to the injection of the startup fluid 26 into the subsurface formation.
In some implementations, a heater (e.g., through electric resistive heaters, RF
heaters or other heating means) can also be provided in the production well 14 to provide additional heat to the interwell region 16. More details regarding heating of the interwell region 16 are provided below.
Characteristics of the startup fluid [227] The startup fluid can include at least two components, and have a variable composition or a variable functionality over time to advantageously leverage the properties of each of its components with regard to their effect on bitumen and startup chamber growth during the startup process. The startup fluid can include a non-deasphalting mobilizing solvent and a deasphalting mobilizing solvent, the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent varying over the course of the startup process to obtain various effects on the bitumen.
The startup process can also include stage(s) during which the startup fluid includes either one of a non-deasphalting mobilizing solvent or a deasphalting mobilizing solvent.
[228] A non-deasphalting mobilizing solvent refers to a solvent that does not induce asphaltene precipitation when in contact with bitumen, while being able to mobilize bitumen via dissolution effects. Examples of non-deasphalting mobilizing solvents can include aromatic solvents, such as toluene, )rylene and diesel as well as higher carbon number solvents or other refining products. Another example of a non-deasphalting solvent is dimethyl ether. As the startup fluid is injected into the subsurface formation as vapour, i.e., the startup fluid exits the injection well and/or the production well as vapour, the non-deasphalting mobilizing solvent can be chosen such that vaporization is enabled in a temperature range at which the startup process is operated. The temperature range can be determined in part based on the requirement that the startup fluid be injected in the subsurface formation at a sufficiently high temperature such that the startup fluid =
remains in vapour phase until it contacts the bitumen. The temperature range can also be determined in part based on the requirement that the startup fluid be injected in the subsurface formation at a sufficiently low temperature that the deasphalting mobilizing solvent condenses once in the subsurface formation, especially on the surfaces of the startup chamber when the startup chamber has grown sufficiently.
[229] The interwell region is characterized by various levels of oil or bitumen saturation and various levels of fluid mobility. In some implementations, prior to the startup process the interwell region can include a high saturation interval having low fluid mobility. For instance, an oil or bitumen saturation between the range of 50%
to 100%
can be considered a high saturation interval. The use of a non-deasphalting mobilizing solvent early in the startup process, for instance as the first mobilizing fluid introduced in the subsurface formation, can facilitate establishing fluid communication between the injection and production wells by promoting the flow of mobilized bitumen from the injection well to the production well. The use of a non-deasphalting mobilizing solvent can also facilitate avoiding precipitation of asphaltenes in proximity to the injection well and/or the production well, either early in the startup process or at any other time during the startup process. Precipitation of asphaltenes in proximity of the wells can impair the flow of solvent and of the mobilized bitumen in the interwell region and can also increase the risk of clogging of the wells. It is to be noted that in some implementations, a chase fluid, such as water, either as steam or as an aqueous liquid stream, can be injected into the reservoir to aid in establishing fluid communication in the interwell region.
[230] A deasphalting mobilizing solvent refers to a solvent that has the property of promoting the precipitation of asphaltenes under certain conditions. Certain paraffinic solvents, also referred to as alkanes, such as propane, butane, pentane, and condensates are examples of deasphalting mobilizing solvents. The solubility of asphaltenes in such paraffinic solvents is relatively low particularly at higher solvent concentrations. The introduction of paraffinic solvent into a subsurface formation is generally avoided during a startup process because of their impact on the precipitation of asphaltenes. As mentioned above, if asphaltenes are precipitated too early in the startup process, when the bitumen saturation in the interwell region is still high, the flow of mobilized bitumen can be impaired, and pore space and/or the wells can become clogged. On the other hand, a paraffinic solvent can advantageously contribute to growing a startup chamber around the injection well. The startup chamber can be developed as mobilized bitumen is being produced via the production well and thus form a bitumen-depleted region, thereby creating a space around the injection well, which will eventually grow to occupy the?interwell region and a region above the injection well as injection of the deasphalting mobilizing solvent continues.
[231] In accordance with the techniques described herein, in some implementations, the startup fluid can initially be provided in a first stage proportion for introduction into the subsurface formation. The first stage proportion of the startup fluid refers to a startup fluid having a given proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent, the given proportion being such that asphaltenes remain substantially in solution when the startup fluid contacts the bitumen in the subsurface formation. In other words, the first stage proportion of the startup fluid is formulated to avoid asphaltene precipitation at the injection conditions, and thus generally has a lower concentration of the deasphalting mobilizing solvent compared to the concentration of the non-deasphalting mobilizing solvent. It is to be understood that the first stage proportion,can be achieved when other components are present in the startup fluid, for instance water or steam, but will generally be expressed using the proportion between the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent, this given proportion being such that overall, asphaltenes remain substantially in solution when contacted with the startup fluid. In some implementations, the amount of non-deasphalting mobilizing solvent in the first stage proportion can be lower than the amount of deasphalting mobilizing solvent in the startup fluid, as long as this proportion of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent results in a startup fluid that reduces asphaltene precipitation at the injection conditions.
[232]
Figures 2 and 3 illustrate possible implementations related to the composition of the startup fluid, with varying proportions of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent as the startup process evolves over time. Figures 4 to 7 illustrate other possible implementations of the startup fluid, showing the concentration of non-deasphalting mobilizing solvent as a function of time. Figures 2 and 3 show that at the beginning of the startup process, the non-deasphalting mobilizing solvent is provided in a first stage proportion 32 relative to the deasphalting mobilizing solvent, the first stage proportion being exemplified at approximately 2:1. A 2:1 proportion means that the startup fluid comprises twice as much non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent, which can be expressed for instance in terms of volume. The first stage proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent is chosen such that asphaltenes remain in solution in the bitumen while enabling mobilization of the bitumen in the interwell region. It is to be understood that the approximative 2:1 proportion is given as an example only, and that depending on factors such as the respective non-deasphalting mobilizing solvent and deasphalting mobilizing solvent used, the chosen proportion can vary substantially.
[233] The composition of the startup fluid can be expressed using various other units to illustrate the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent, for instance vol%, mass % or mol%. Given units can be chosen for instance depending on the choice of components in the startup fluid, including the choice of non-deasphalting mobilizing solvent and deasphalting mobilizing solvent. Examples of first stage proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent can be about 30 wt% toluene as non-deasphalting mobilizing solvent and about 70 wt% butane as deasphalting mobilizing solvent, or about 50 wt% toluene and about 50 wt% butane. In some implementations, an example of a second stage proportion can be between about 5 wt% to 10 wt%
of toluene as non-deasphalting mobilizing solvent, and between about 90 wt% and 95 wt%
of butane as deasphalting mobilizing solvent.
[234] The choice of the first stage proportion can depend on various factors such as bitumen saturation in the interwell region, nature of non-deasphalting and deasphalting mobilizing solvents and reservoir geology. Determining the first stage proportion can be done such that each one of the non-deasphalting mobilizing solvent and the deasphalting mobilizing solvent can have an impact on the startup process with regard to bitumen mobilization and startup chamber growth. In other words, the first stage proportion of the startup fluid can include a sufficiently high amount of non-deasphalting mobilizing" solvent such that asphaltene precipitation is avoided and formation of a startup chamber is facilitated, and a sufficiently high amount of deasphalting mobilizing solvent to contribute to startup chamber growth. In some implementations, allowing concomitant mobilization of bitumen and startup chamber growth can thus be advantageous in terms of reducing the duration of startup process.
[235] Still referring to Figures 2 and 3, the startup fluid eventually transitions from the first stage proportion 32 to a second stage proportion 34. By "transitioning", it is meant that the proportion of non-deasphalting mobilizing solvent relative to deasphalting mobilizing solvent changes. Figure 2 shows the transition from the first,stage proportion 32 to the second stage proportion 34 as a step change 36, whereas Figure 3 shows the transition from the first stage proportion 32 to the second stage proportion 34 as a =
continuous change 38. In both cases, the second stage proportion 34 has a reduced amount of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the first stage proportion 32. In some implementations, the startup process described herein includes at least introducing the startup fluid into the subsurface formation in the first stage proportion for a given period of time, and in the second stage proportion for another given period on time. With reference to Figure 2, this means that the startup process includes at least the first stage proportion 32, the step change 36 and the second stage proportion 34. With reference to Figure 3, the startup process includes at least the first stage proportion 32, the decreasing continuous change 38 and the second stage proportion 34. Further reduction(s) of the proportion of the non-deasphalting mobilizing solvent relative to deasphalting mobilizing solvent can occur, which will be considered as extending the second stage of the startup process. In some implementations, reservoir parameters such as initial reservoir pressure and phase behavior of mobilizing solvent can influence when to transition from the first stage proportion to the second stage proportion, or when one or more subsequent stage proportions are to be implemented.
[236] In some implementations and as shown in Figure 4, the startup fluid can have a substantially continuous reduction of the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent over time.
In such implementations, the startup fluid is injected into the subsurface formation as a first stage startup fluid having a first functionality. The first functionality can be, for instance that asphaltenes remain in solution, i.e., to ensure that asphaltene deposition does not occur or is minimized in proximity of the wells, and/or that startup chamber growth is enabled. In other words, the first stage startup fluid can refer to a stage of the startup fluid that includes a continuous reduction, or continuous decline, in the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent. The reduction, or ramp-down, of the non-deasphalting mobilizing fluid relative to the deasphalting mobilizing solvent can be continued for a given period of time, until a change in functionality of the startup fluid is desired, such that the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent allows benefiting from a second functionality of the startup fluid. For instance, the first stage startup fluid having a first functionality can be transitioned to a second stage startup fluid having a second functionality, the second functionality being enabling accelerated startup chamber growth, or allowing precipitation of asphaltenes. Of note, the startup process can also include a stage during which the startup fluid initially includes a non-deasphalting mobilizing solvent injected into the subsurface formation in vapour phase without a deasphalting mobilizing solvent to achieve the first functionality, for instance enabling the formation of a startup chamber, as exemplified in Figure 7.
[237] For instance, Figure 4 shows a first stage proportion 32 where the non-deasphalting mobilizing solvent has a given concentration in the startup fluid, and that concentration of the non-deasphalting mobilizing solvent decreases continuously 38 until the second stage proportion 34 is reached, while the concentration of deasphalting mobilizing solvent continuously increases. In the exemplified implementation shown in Figure 4, the first stage startup fluid corresponds to the combination of the startup fluid having a first stage proportion 32 at a given moment followed by the continuous decrease 38, the first stage startup fluid having a first functionality. Still in the exemplified implementation shown in Figure 4, the second stage startup fluid corresponds to the combination of the startup fluid having a second stage proportion 34 at a given moment followed by the continuous decrease 38, the second stage startup fluid having a second functionality.
[238] In some implementations, the startup process can also include subsequent reduction(s) of the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent. For instance, with reference to Figure 2, the startup fluid in the second stage proportion 34 can be further transitioned to a third stage proportion 40 with a step change 36 and so on. With reference to Figure 3, the startup fluid can also be further transitioned to a third stage proportion 40 with a decreasing continuous change 38 and so on. Of course, numerous paths can lead to the transition from the first stage proportion to the second stage proportion and optionally to subsequent stage proportions. It should thus be understood that the embodiments shown in Figures 2 to 7 are examples only and that the reduction of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent could occur in many other ways, including constant proportions of the non-deasphalting mobilizing fluid relative to the deasphalting mobilizing fluid and/or continuous declines of the proportion of the non-deasphalting mobilizing fluid relative to the deasphalting mobilizing fluid.
[239] In some implementations, decreasing the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent can allow accelerated growth of the startup chamber. Decreasing the proportion of the non-deasphalting mobilizing fluid relative to the deasphalting mobilizing fluid can eventually reach a proportion that, according to the characteristics of the bitumen and reservoir, may lead to precipitation of asphaltenes, for instance late in the startup process (i.e., close to the beginning of normal recovery operations). It is important to note that allowing precipitation of asphaltenes in situ, i.e., in the reservoir, is preferably done close to the end of the startup process, when the interwell region has been cleaned and bitumen saturation has been substantially reduced. Thus, it is to be noted that the second stage proportion and optionally the subsequent stage proportions, as well as the second composition, are not one that will necessarily cause asphaltenes to precipitate, even if the non-deasphalting mobilizing solvent is reduced, as it is generally not desirable in the early phase of a bitumen recovery process to cause asphaltenes precipitation in proximity of a well pair. The second stage proportion and the second composition can be rather chosen such that startup chamber growth is enabled and/or accelerated.
[240] In some implementations, the reduction of the amount of non-deasphalting mobilizing solvent in the startup fluid can be such that eventually, the startup fluid can be substantially free of non-deasphalting mobilizing solvent, at which point in time normal recovery operations could be considered to begin. Other indicators can also contribute to determine when normal recovery operations can be considered to begin. For instance, in some implementations, normal recovery operations can be considered to begin when the startup chamber has reached a given size. The given size can be one where the startup chamber at least reaches the production well or is reasonably close to the production well. The given size can also be one where the startup chamber reaches the production well and rises above the injection well. Various techniques can be used to assess startup chamber growth and thus progression of startup process towards the beginning of normal recovery operations. For example, chamber growth and size can be inferred using observation wells, seismic analysis, as well as through analysis of the production fluid. For instance, components of the production fluid can be analyzed, and it can be expected that in the beginning of the startup process, the production fluid can include mostly bitumen with connate water. On the other hand, near the end of the startup process, it can be expected that there will be a higher fraction of mobilizing solvents in the production fluid, compared to at the beginning of the startup process. In some implementations, growth of the startup chamber during the startup process can facilitate the initiation of the normal recovery operations.
[241] In some implementations, a reduction of the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent can be made possible because a certain portion of the non-deasphalting mobilizing solvent has accumulated at the interface between the startup chamber and bitumen. In such implementations, the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent is reduced as the asphaltene solubilizing effect of the non-deasphalting mobilizing solvent can be achieved relying on the presence of non-deasphalting mobilizing solvent already present and accumulated in the reservoir.
Whether such scenario can occur can depend for instance on specific reservoir conditions and recovery scheme, and is likely to occur near the end of the startup process.
[242] In some implementations, there can be scenarios where at some point in time in the startup process, the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent is increased, for instance if undesired effects of the startup fluid on bitumen mobilization and/or chamber growth are observed.
Such undesired effects can include recovery of a production fluid having a significant degree of bitumen upgrading early in the startup process, which can suggest that asphaltene precipitation has been occurring in the reservoir, an effect that is generally to be avoided. Another factor that can suggest whether it can be advantageous to increase the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent is when an excessive pressure differential between the injection well and the production well is detected, which can be indicative of asphaltene precipitation in the interwell region. In such scenarios and with reference to Figure 6, a corrective action can thus be to adjust the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent, and in particular to increase the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent so as CA 3060946 2019-11-05 =

to mitigate asphaltenes precipitation, for instance through an increasing continuous change 41. In Figure 6, the increasing continuous change 41 leads to the third stage proportion 40, which is then followed by a decreasing continuous change 38.
Another scenario to consider can be that when monitoring the concentration of non-deasphalting solvent in the production fluid, it is observed that a low portion of non-deasphalting mobilizing solvent is being produced with the recovery of the production fluid. Such scenario can mean that a portion of the non-deasphalting mobilizing solvent has migrated within the reservoir such that the non-deasphalting mobilizing solvent is less effective at performing the maintaining in solution of the asphaltenes. This scenario can thus trigger an increase in the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent, to mitigate this effect. In the scenarios discussed above, it is to be noted that the increase in the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent can be such that the non-deasphalting mobilizing solvent is injected without any of the deasphalting mobilizing solvent, depending for instance on the extent of asphaltene precipitation that needs to be dealt with.
[243] As mentioned above, the startup fluid can be introduced into the subsurface formation in vapour phase, i.e., exit the injection well and/or the production well in vapour phase. When the startup fluid includes an aromatic solvent as the non-deasphalting mobilizing solvent and a paraffinic solvent as the deasphalting mobilizing solvent, the higher vaporization temperature of aromatic solvents can advantageously provide sufficient heat for the paraffinic solvent to vapourize when the two solvents are combined. One approach to vapourize the startup fluid is thus to vapourize the deasphalting mobilizing solvent at surface using conventional heating means (e.g., a direct fired heater or an indirect heat exchanger), such that when the non-deasphalting mobilizing solvent is then combined with the vapourized deasphalting mobilizing solvent, the non-deasphalting mobilizing solvent also vapourizes as it is carried with the vapourized deasphalting mobilizing solvent. In this scenario, the non-deasphalting mobilizing solvent can be simply fed as a liquid via a pipe intersection or quill into the pipeline carrying the vapourized deasphalting mobilizing solvent. In other implementations, both the non-deasphalting mobilizing solvent and the deasphalting mobilizing solvent are already in vapour phase when they are combined, and thus are combined as two vapour streams.
[244] This difference in vaporization temperature between the non-deasphalting mobilizing solvent and the deasphalting mobilizing solvent can also advantageously allow preferential condensation of the non-deasphalting mobilizing solvent in the startup chamber. Condensation of the non-deasphalting mobilizing solvent can enable condensed non-deasphalting mobilizing solvent to drain by gravity towards the production well and form a pool of non-deasphalting mobilizing solvent and bitumen around the production well, thereby facilitating eventual recovery of mobilized bitumen.
On the other hand, the deasphalting mobilizing solvent can advantageously remain as vapour in the startup chamber for a longer period of time given its lower vaporization temperature, and preferably until it comes in contact with the surfaces of the startup chamber at which point it can condense, thereby contributing to the mobilization of bitumen by releasing latent heat of condensation and diluting the bitumen.
[245] In addition, as mentioned above, the startup process can include stage(s) during which either one of the non-deasphalting mobilizing solvent or the deasphalting mobilizing solvent can be introduced into the subsurface formation. These scenarios can occur at any time during the startup process, i.e., at the beginning of the startup process, during the startup process, or as the last stage of the startup process. The injection of a non-deasphalting mobilizing solvent without a deasphalting mobilizing solvent, or the injection of a deasphalting mobilizing solvent without a non-deasphalting mobilizing solvent, can be done according to the functionality of the startup fluid that is desired to be achieved.
[246] In some implementations, a non-deasphalting mobilizing solvent can be introduced into the subsurface formation as vapour, without being combined with a deasphalting mobilizing solvent, to enable startup chamber growth. The use of a vaporized non-deasphalting mobilizing solvent can be advantageous, for instance at the beginning of the startup process, to enable formation of a startup chamber while avoiding precipitation of asphaltenes. In such implementations, the first stage proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent would be considered to be 1:0, since the non-deasphalting mobilizing solvent is injected without the deasphalting mobilizing solvent. Accordingly, in some implementations, a stage during which the startup fluid includes a non-deasphalting mobilizing solvent that is introduced into the subsurface formation in vapour phase without a deasphalting mobilizing solvent can correspond to the first stage of the startup process, or to a startup fluid having a first functionality. Examples of non-deasphalting mobilizing solvents that can be advantageous to use at the beginning of the startup process to grow the startup chamber are toluene and xylene, among others. A deasphalting mobilizing solvent is then subsequently combined with the non-deasphalting mobilizing solvent to reach a second stage proportion of the startup fluid, or to be transitioned to the startup fluid having a second functionality, in accordance with the implementations described herein.
[247] In some implementations, a non-deasphalting mobilizing solvent can also be injected without a deasphalting mobilizing solvent at any stage during the startup process, for instance to remediate to asphaltene precipitation in the interwell region or in the wellbore. Such implementations are similar to those described above with regard to the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent being increased during the startup process if undesired effects of the startup fluid on bitumen mobilization and/or chamber growth are observed, although in this case the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent is increased up to a point where the non-deasphalting mobilizing solvent is injected without a deasphalting mobilizing solvent. This includes implementations wherein the non-deasphalting mobilizing solvent is injected without the deasphalting mobilizing solvent for a given period of time, until satisfactory conditions of the startup process are reached again, such as the composition of the production fluid, the pressure differential between the wells, etc. In some scenarios, the non-deasphalting mobilizing solvent can be injected without the deasphalting mobilizing solvent and the injection well can be shut in for a given period of time, for instance to allow dissolution of asphaltene precipitates that have formed. In other scenarios, a non-deasphalting mobilizing solvent can also be injected without the deasphalting mobilizing solvent during the recovery of production fluid to reduce the risk of asphaltene precipitation.
[248] As mentioned above, in some implementations, the amount of non-deasphalting mobilizing solvent in the startup fluid can be decreased such that eventually, the startup fluid can be substantially free of non-deasphalting mobilizing solvent, which can be for instance near the end of the startup process. These implementations are examples of scenarios where the injection of a deasphalting mobilizing solvent can be performed without a non-deasphalting mobilizing solvent.
Again, depending on the functionality of the startup fluid that is to be achieved, stage(s) where the injection of the deasphalting mobilizing solvent is performed without the non-deasphalting mobilizing solvent can occur during the startup process, and not just at the end of the startup process, for instance to accelerate startup chamber growth.
[249] In some implementations, prior to the startup fluid being injected into the subsurface formation, a step of pre-heating can be performed to pre-heat the bitumen present in the interwell region to contribute to its mobilization. The pre-heating step can be performed by heating the injection well and optionally the production well using heater strings such as those described above, or through electric resistive heaters, RF
heaters or other heating means. Alternatively, the pre-heating step can be performed by circulating steam in the injection well or any other pre-heating technique. In some cases, the heaters can continue operating during subsequent stages of the startup processes, such that the startup fluid is injected while the heaters continue to impart heat to the reservoir.
Monitoring variables related to startup process [250] Various variables can be monitored to determine suitable second stage proportions of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent in the startup fluid (and optionally of third stage proportions and so on), the timing of the change from one stage proportion to another, and also to assess, whether the startup procedure can be considered to be terminated such that transition into the normal recovery operations can be initiated.
[251] Once the startup fluid has been injected into the subsurface formation for a given period of time, bitumen that has been mobilized by the presence of the startup fluid and optionally the heat provided during the pre-heating step, can drain into the production well by gravity and can be recovered to the surface using artificial lift or a pump (e.g., electric submersible pump or ESP) deployed in the production well.
A
compositional characteristic of the produced mobilized bitumen during the startup process is an example of a variable that can be monitored. A compositional characteristic of the produced mobilized bitumen can be, for instance, the concentration of the non-deasphalting mobilizing solvent, the concentration of the deasphalting mobilizing solvent in the produced mobilized bitumen, the asphaltene content of the mobilized bitumen, and/or the API gravity of the mobilized bitumen.
[262] In particular, the compositional characteristic of the produced mobilized bitumen can be indicative of the extent of cleanup, or bitumen de-saturation, that has occurred between the injection well and the production well. Bitumen de-saturation between the injection well and production well refers to the process of substantially reducing bitumen saturation in the interwell region, which can be achieved at least in part by the mobilization of bitumen and production of mobilized bitumen to the surface.
De-saturation of the interwell region from bitumen thus can create a space between the injection well and the production well which can facilitate growth of the startup chamber described herein. Sufficient bitumen de-saturation of the interwell region can be said to be achieved for instance when solvent from the startup fluid is found in high concentration in the production fluid (in which case the solvent can be said to be back produced). Other techniques that can be used to serve as indicators of bitumen de-saturation in the interwell region and thus the degree of interaction between the injection well and the production well can include analysis of pressure interaction between the wells, seismic analysis, use of observation well temperature readings, and repeat saturation logging.
[263] The asphaltene content of the produced mobilized bitumen can be assessed to determine whether the amount of non-deasphalting mobilizing solvent in the startup fluid is sufficient for asphaltenes to remain in solution, i.e., to ensure that asphaltene deposition does not occur or is minimized in proximity of the wells. For instance, if the asphaltene content of the produced mobilized bitumen is low, it could be hypothesized that asphaltenes are left in the subsurface formation as precipitates, which is to be avoided. On the other hand, if the asphaltene content in the produced mobilized bitumen is high, then it could be hypothesized that asphaltenes are solubilized in the startup fluid and are being removed from the subsurface formation with the produced mobilized bitumen.

[254] Simulations can be performed to help predict which level of asphaltene content is to be expected for a given subsurface formation and/or given combination and proportion of non-deasphalting mobilizing solvent and deasphalting mobilizing solvent as components of the startup fluid. Thus, when such simulations are available, one can assess whether the asphaltene content of the produced mobilized bitumen is below a predetermined asphaltene content threshold. If the asphaltene content is above the predetermined asphaltene content threshold, then the composition of the startup fluid could be considered effective at least for the purpose of keeping the asphaltenes in solution such that the space between the injection well and the production well can be cleaned up. If the asphaltene content is below the predetermined asphaltene content threshold, then the amount of the deasphalting mobilizing solvent in the startup fluid could be reduced relative to the non-deasphalting mobilizing solvent, or the amount of the non-deasphalting mobilizing solvent in the startup fluid could be increased relative to the deasphalting mobilizing solvent to favor the solubilization of the asphaltenes.
[255] In some implementations, the amount of non-deasphalting mobilizing solvent can be determined such that it is sufficient to keep the asphaltenes in solution and to facilitate the formation of a startup chamber, while being combined with a sufficient amount of deasphalting mobilizing solvent to also contribute to the growth of the startup chamber. Keeping the right balance between the amount of non-deasphalting mobilizing solvent and the amount of deasphalting mobilizing solvent in the startup fluid can be relevant to achieving concomitant mobilization of bitumen and startup chamber growth.
This right balance can change as the startup process progresses and the interwell space becomes cleaner over time.
[256] The API gravity of the produced mobilized bitumen can also be evaluated in a similar fashion as the asphaltene content itself, as the API gravity can be considered indicative of the asphaltene content of the produced mobilized bitumen.
[257] As the startup process progresses and the interwell space becomes cleaner, the concentration of bitumen in the mobilized bitumen that is produced to the surface can decrease and include an increasing proportion of the startup fluid solvents.
Monitoring the concentration of the non-deasphalting mobilizing solvent and/or of the deasphalting mobilizing solvent in the produced mobilized bitumen can be used to determine the timing of when the space can be considered clean enough that the proportion of the non-deasphalting mobilizing solvent can be reduced or ramped-down.
In other words, because the space around the injection well and the production well is now cleaned up, i.e., mobilized bitumen has been removed from the interwell space, the risk of asphaltene precipitates .forming and impairing the flow of mobilized bitumen or, clogging the wells is decreased. Accordingly, the startup fluid can include a decreased amount of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent, because it is no longer as relevant to keep asphaltenes in solution and the startup fluid can rather be optimized to further grow the startup chamber efficiently, for instance to reduce operation costs. Over the course of the startup process, the composition of the produced mobilized bitumen can thus progressively evolve from a composition having a high bitumen content, to a composition having a moderate bitumen content with a low concentration of non-deasphalting mobilizing solvent, to a composition having a low bitumen content and a high concentration of non-deasphalting mobilizing solvent. As mentioned above, the non-deasphalting mobilizing solvent condenses preferably in the startup chamber and can, produced with mobilized bitumen, while the deasphalting mobilizing solvent preferably remains as vapour in the startup chamber. Although the terms "high" and "low" are relative terms, they can still show how the composition of the production fluid can approximately evolve during the startup process.
[258] Another option to determine when it can be appropriate to reduce the amount of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent is to use volumetric simulations. Such volumetric simulations can provide an estimate of a given volume between the injection well and the production well, and once a corresponding volume of mobilized bitumen has been produced to the surface, it can be expected that this volume of interwell region has been cleaned up. Once again, when the interwell region has been cleaned up, the startup fluid can include a decreased amount of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent at least because the interwell region has been substantially cleaned from the asphaltenes that could have potentially precipitated.
[259] Other types of simulations to determine the extent of cleanup around the wells include 4D seismic reservoir analysis to monitor changes in fluid location and saturation, pressure and temperature by evaluating the changes in the acoustic and elastic properties of the geological formation. Relevant data can also be obtained from strategically positioned observation wells.
[260] In some implementations, it may be advantageous that one or more components of the startup fluid be changed over the course of the startup process. In such implementations, the startup fluid can include, in a first stage of the startup process, a first non-deasphalting mobilizing solvent and a first deasphalting mobilizing solvent provided in a first stage proportion that enables asphaltenes to remain in solution. When transitioning to a second stage of the startup process, the first non-deasphalting mobilizing solvent and the first deasphalting mobilizing solvent of the startup fluid are provided in a second stage proportion, such that the amount of the first non-deasphalting mobilizing solvent relative to the first deasphalting mobilizing solvent is reduced. Following the change to the second stage proportion, the first non-deasphalting mobilizing solvent can be changed to a second non-deasphalting mobilizing solvent, and/or the first deasphalting mobilizing solvent can be changed to a second deasphalting mobilizing solvent to achieve given results on the mobilization of the bitumen and/or the startup chamber growth. For instance, in the first stage of the startup process, the startup fluid can include diesel as the first nonAeasphalting mobilizing solvent and butane as the first deasphalting mobilizing solvent in a first stage proportion that enables asphaltenes to remain in solution. In the second stage of the startup process, the amount of diesel can be ramped down relative to the amount of butane, such that the diesel and butane are provided in the second stage proportion.
Then, for example, the diesel can be changed to toluene and/or the butane can be changed to propane. In some implementations, the new combination of non-deasphalting mobilizing solvent and deasphalting mobilizing solvent can facilitate achieving certain characteristics of the startup chamber and/or preparing the reservoir for effective recovery during the normal operations.
[261] In other implementations, the startup fluid can be formulated as a first composition and include, in a first stage of the startup process, a first non-deasphalting mobilizing solvent and a first deasphalting mobilizing solvent provided such that asphaltenes remain in solution. When transitioning to a second stage of the startup process, the startup fluid can be transitioned to a second composition. In the second composition, the first non-deasphalting mobilizing solvent can be changed to a second non-deasphalting mobilizing solvent and/or the first deasphalting mobilizing solvent can be changed to a second deasphalting mobilizing solvent. The second composition can be chosen so as to facilitate achieving certain characteristics of the startup chamber and/or preparing the reservoir for effective recovery during the normal operations.
Implementations related to recovery of mobilized bitumen as production fluid [262] As mentioned above, the startup fluid is introduced into the subsurface , formation to dilute and heat bitumen and produce mobilized bitumen. The mobilized bitumen can then drain into the production well and be recovered to the surface as a production fluid, which creates the space around the injection well. The production fluid thus recovered can have a variable composition depending on the stage of the startup process. Depending on different factors, such as the composition of the production fluid and economic considerations, it may be desirable to subject the production fluid to one or more separation steps, for instance to recover one or both of the non-deasphalting mobilizing solvent and the deasphalting mobilizing solvent. The recovered mobilizing solvents can then be used as recycled solvents in the startup fluid. In implementations where the non-deasphalting mobilizing solvent is an aromatic solvent and the deasphalting mobilizing solvent is a paraffinic solvent, the difference between their respective vaporization temperatures can mean that different separation steps are put in place to recover each mobilizing solvent.
[263] With reference to Figure 8, a production fluid 42 is recovered during the startup process. The production fluid includes mobilized bitumen, water, solids and at least a portion of both solvents of the startup fluid. The production fluid 42 is subjected to a first separation 44 to remove water and solids 46 as an underflow, and to recover a solvent-rich fluid 48 comprising mobilized bitumen and a portion of the startup fluid as an overflow. In some implementations, the first separation 44 can be performed for instance through gravity separation mechanisms. The composition of the solvent-rich fluid 48 can vary in accordance with the composition of the production fluid 42, in terms of the bitumen content and the respective concentrations of the non-deasphalting mobilizing solvent and the deasphalting mobilizing solvent. The solvent-rich fluid 48 is then subjected to a second separation 50 to recover a deasphalting mobilizing solvent-rich stream 52 and a mixed bitumen and non-deasphalting mobilizing solvent stream

54. The second separation 50 can be performed for instance in a flash vessel through evaporation mechanisms to flash the deasphalting mobilizing solvent from the solvent-rich fluid 48. This separation technique can advantageously leverage the difference in vaporization temperature between the deasphalting mobilizing solvent and the non-deasphalting mobilizing solvent, such that the deasphalting mobilizing solvent can be selectively separated. The deasphalting mobilizing solvent-rich stream 52 can be reused as a component of the startup fluid for reintroduction into the subsurface formation.
[264] In some implementations, the mixed bitumen and non-deasphalting mobilizing solvent stream 54 can be further separated in a third separation step 56 to recover a non-deasphalting mobilizing solvent-rich stream 58 and a bitumen-rich stream 60. In other implementations, it may be advantageous to keep the mixed bitumen and non-deasphalting mobilizing solvent stream 54 as a combined fluid, for instance because the presence of the non-deasphalting mobilizing solvent may act as a diluent, such that the mixed bitumen and non-deasphalting mobilizing solvent stream 54 may have valuable characteristics in itself. In other implementations, the bitumen-rich stream 60 can then be further processed to obtain a suitable bitumen product.
[265] Of note, although the first separation 44, the second separation 50 and the third separation 56 are illustrated as a single step, each one of the first separation 44, the second separation 50 and the third separation 56 can include more than one separation stage in order to achieve the desired separation.

Claims

45

1. A startup process for mobilizing bitumen in an interwell region, the interwell region being defined between a horizontal injection section of an injection well and a horizontal production section of a production well located below the horizontal injection section, the injection well and the production well being located in a bitumen-containing reservoir, the startup process comprising:
introducing a startup fluid comprising a non-deasphalting mobilizing solvent and a deasphalting mobilizing solvent into the bitumen-containing reservoir via the injection well, the non-deasphalting mobilizing solvent and the deasphalting mobilizing solvent being provided in a first stage proportion;
recovering mobilized bitumen from the interwell region via the production well as a production fluid to form a bitumen-depleted region that enables fluid communication between the injection well and the production well; and transitioning the startup fluid from the first stage proportion to a second stage proportion, the second stage proportion having a reduced amount of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the first stage proportion;
wherein at least the first stage proportion of the startup fluid enables asphaltenes to remain substantially solubilized in the mobilized bitumen.

2. The startup process of claim 1, wherein transitioning the startup fluid from the first stage proportion to the second stage proportion comprises a continuous transition.

3. The startup process of claim 1, wherein transitioning the startup fluid from the first stage proportion to the second stage proportion comprises a step transition.

4. The startup process of any one of claims 1 to 3, wherein the second stage proportion enables the asphaltenes to remain substantially solubilized in the mobilized bitumen.

5. The startup process of any one of claims 1 to 3, wherein the second stage proportion enables precipitation of at least a portion of the asphaltenes such that asphaltene precipitates are formed.

6. The process of claim 5, further comprising transitioning the startup up fluid from the second stage proportion to a third stage proportion.

7. The startup process of claim 6, wherein transitioning the startup fluid from the second stage proportion to the third stage proportion comprises a continuous transition.

8. The startup process of claim 6, wherein transitioning the startup fluid from the second stage proportion to the third stage proportion comprises a step transition.

9. The startup process of any one of claims 6 to 8, wherein the third stage proportion has an increased amount of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the second stage proportion.

10. The startup process of any one of claims 6 to 9, wherein the third stage proportion is substantially free of the deasphalting mobilizing solvent.

11. The startup process of claim 9 or 10, wherein the third stage proportion enables the asphaltenes to remain substantially solubilized in the mobilized bitumen.

12. The startup process of claim 11, further comprising maintaining the startup fluid in the third stage proportion for a given period of time to resolubilize the asphaltene precipitates.

13. The startup process of any one of claims 6 to 8, wherein the third stage proportion has a reduced amount of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the second stage proportion.

14. The startup process of claim 12 or 13, wherein maintaining the startup fluid in the third stage proportion and recovering the mobilized bitumen as the production fluid from the interwell region via the production well is performed substantially simultaneously.

15. The startup process of claim 13 or 14, wherein the third stage proportion allows precipitation of at least a portion of the asphaltenes.

16. The startup fluid of any one of claims 1 to 15, wherein the startup fluid further comprises steam.

17. The startup process of claim 1 to 16, wherein introducing the startup fluid into the bitumen-containing reservoir comprises:
vapourizing at least the non-deasphalting mobilizing solvent at surface to obtain a vapourized non-deasphalting mobilizing solvent;
combining the vapourized non-deasphalting mobilizing solvent with the deasphalting mobilizing solvent to obtain a vapourized startup fluid; and injecting the vapourized startup fluid into the interwell region via the injection well.

18. The startup process of any one of claims 1 to 16, wherein introducing the startup fluid into the bitumen-containing reservoir comprises vapourizing the startup fluid at surface to obtain a vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.

19. The startup process of any one of claims 1 to 16, wherein introducing the startup fluid into the bitumen-containing reservoir comprises heating the startup fluid as the startup fluid travels along the injection well to obtain a vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.

20. The startup process of claim 19, wherein heating the startup fluid as the startup fluid travels along the injection well comprises providing electrically heating using one or more electric resistive heaters in the injection well.

21. The startup process of any one of claims 1 to 20, wherein introducing the startup fluid into the bitumen-containing reservoir further comprises injecting the startup fluid via the production well prior to recovering the mobilized bitumen from the interwell region via the production well.

22. The startup process of any one of claims 1 to 21, wherein introducing the startup fluid into the bitumen-containing reservoir further comprises injecting the startup fluid via the production well cyclically between periods of recovering the mobilized bitumen from the interwell region via the production well.

23. The startup process of any one of claims 17 to 22, wherein at least the first stage proportion further enables formation of a startup chamber.

24. The startup process of claim 23, wherein recovering the mobilized bitumen via the production well and the formation of the startup chamber are performed substantially simultaneously.

25. The startup process of claim 23 or 24, further comprising determining startup chamber size.

26. The startup process of claim 25, wherein transitioning the startup fluid from the first stage proportion to the second stage proportion is performed when the startup chamber size has reached a given size.

27. The startup process of any one of claims 6 to 15, wherein the startup fluid is introduced into the bitumen-containing reservoir as a vapourized startup fluid.

28. The startup process of claim 27, wherein at least the first stage proportion further enables formation of a startup chamber.

29. The startup process of claim 28, further comprising determining startup chamber size.

30. The startup process of claim 29, wherein transitioning the startup fluid from the second stage proportion to the third stage proportion is performed when the startup chamber size has reached a given size.

31. The startup process of any one of claims 1 to 30, further comprising determining an amount of mobilized bitumen produced from the interwell region to assess bitumen de-saturation in the interwell region.

32. The startup process of claim 31, wherein when the amount of mobilized bitumen produced from the interwell region is above a given threshold, the first stage proportion is transitioned to the second stage proportion.

33. The startup process of any one of claims 1 to 32, further comprising monitoring a production variable related to recovering the production fluid.

34. The startup process of claim 33 wherein the production variable comprises a compositional characteristic of the production fluid.

35. The startup process of claim 34, wherein the compositional characteristic comprises a non-deasphalting mobilizing fluid concentration in the production fluid.

36. The startup process of claim 34 or 35, wherein the compositional characteristic of the production fluid comprises a deasphalting mobilizing fluid concentration in the production fluid.

37. The startup process of any one of claims 34 to 36, wherein the compositional characteristic of the production fluid comprises a bitumen concentration of the production fluid.

38. The startup process of any one of claims 34 to 37, wherein the compositional characteristic of the production fluid comprises an asphaltene content of the production fluid.

39. The startup process of any one of claims 34 to 38, wherein the compositional characteristic of the production fluid comprises an API gravity of the production fluid.

40. The startup process of any one of claims 1 to 39, wherein in the first stage proportion, a ratio of non-deasphalting mobilizing solvent to deasphalting mobilizing solvent is above or equal to about 1:1.

41. The startup process of any one of claims 1 to 39, wherein in the first stage proportion, a ratio of non-deasphalting mobilizing solvent to deasphalting mobilizing solvent is between 1:1 and 3:1.

42. The startup process of any one of claims 1 to 39, wherein in the second stage proportion, the ratio of non-deasphalting mobilizing solvent to deasphalting mobilizing solvent is below or equal to 1:1.

43. The startup process of any one of claims 1 to 39, wherein in the first stage proportion, the ratio of non-deasphalting mobilizing solvent to deasphalting mobilizing solvent is between about 1:1 and about 1:3.

44. The startup process of any one of claims 1 to 39, wherein in the first stage proportion, the startup fluid comprises between about 30% and about 50% of the non-deasphalting mobilizing solvent and between about 50% and about 70%
deasphalting mobilizing solvent.

45. The startup process of any one of claims 1 to 44, wherein the non-deasphalting mobilizing fluid comprises an aromatic solvent.

46. The startup process of claim 45, wherein the aromatic solvent comprises toluene, diesel, xylene, or a combination thereof.

47. The startup process of claim 45 or 46, wherein the aromatic solvent comprises toluene.

48. The startup process of claim 45 or 46, wherein the aromatic solvent comprises diesel.

49. The startup process of claim 45 or 46, wherein the aromatic solvent comprises xylene.

50. The startup process of any one of claims 1 to 49, wherein the deasphalting mobilizing fluid comprises an alkane solvent.

51. The startup process of claim 50, wherein the alkane solvent comprises propane, butane, pentane, hexane, heptane, condensate, or a mixture thereof.

52. The startup process of claim 50 or 51, wherein the alkane solvent comprises propane.

53. The startup process of claim 50 or 51, wherein the alkane solvent comprises butane.

54. The startup process of claim 50 or 51, wherein the alkane solvent comprises pentane.

55. The startup process of claim 50 or 51, wherein the alkane solvent comprises condensate.

56. The startup process of any one of claims 1 to 55, further comprising pre-heating the interwell region.

57. The startup process of claim 56, wherein pre-heating the interwell region comprises electrically heating using one or more electric resistive heaters in the injection well and/or the production well.

58. The startup process of claim 56 or 57, wherein pre-heating the interwell region comprises circulating steam through the injection well and/or the production well.

59. The startup process of any one of claims 1 to 58, further comprising separating the production fluid to remove water and solids therefrom to obtain a solvent-rich fluid.

60. The startup process of claim 59, further comprising separating the solvent-rich fluid to recover at least a portion of the deasphalting mobilizing solvent and obtain a recycled deasphalting mobilizing solvent suitable for reuse in the startup fluid, and a mixed bitumen and non-deasphalting mobilizing solvent stream.

61. The startup process of claim 60, further comprising separating the mixed bitumen and non-deasphalting mobilizing solvent stream to recover at least a portion of the non-deasphalting mobilizing solvent to obtain a recycled non-deasphalting mobilizing solvent suitable for reuse in the startup fluid.

62. The startup process of claim 60 or 61, wherein introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled deasphalting mobilizing solvent as part of the startup fluid.

63. The startup process of claims 61 or 62, wherein introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled non-deasphalting mobilizing solvent as part of the startup fluid.

64. A startup process for mobilizing bitumen in an interwell region, the interwell region being defined between a horizontal injection section of an injection well and a horizontal production section of a production well located below the horizontal injection section, the injection well and the production well being located in a bitumen-containing reservoir, the startup process comprising:
introducing a startup fluid comprising a non-deasphalting mobilizing solvent and a deasphalting mobilizing solvent into the bitumen-containing reservoir, the startup fluid having a first composition that enables asphaltenes to remain substantially solubilized in mobilized bitumen;
recovering the mobilized bitumen from the interwell region as a production fluid to form a bitumen-depleted region that enables fluid communication between the injection well and the production well; and transitioning the startup fluid from the first composition to a second composition, the second composition having a reduced amount of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the first composition.

65. The startup process of claim 64, wherein introducing the startup fluid into the bitumen-containing reservoir comprises injecting the startup fluid via the injection well.

66. The startup process of claim 64 or 65, wherein introducing the startup fluid into the bitumen-containing reservoir comprises injecting the startup fluid via the production well prior to recovering the mobilized bitumen from the interwell region via the production well.

67. The startup process of any one of claims 64 to 66, wherein introducing the startup fluid into the bitumen-containing reservoir further comprises injecting the startup fluid via the production well cyclically between periods of recovering the mobilized bitumen from the interwell region via the production well.

68. The startup process of any one of claims 64 to 67, further comprising pre-heating the interwell region.

69. The startup process of claim 68, wherein pre-heating the interwell region comprises electrically heating using one or more electric resistive heaters in the injection well and/or the production well.

70. The startup process of claim 68 or 69, wherein pre-heating the interwell region comprises circulating steam through the injection well and/or the production well.

71. The startup process of any one of claims 64 to 70, wherein transitioning the startup fluid from the first composition to the second composition comprises a continuous transition.

72. The startup process of any one of claims 64 to 70, wherein transitioning the startup fluid from the first composition to the second composition comprises a step transition.

73. The startup process of any one of claims 64 to 72, wherein in the second composition, the non-deasphalting mobilizing solvent is changed to a second non-deasphalting mobilizing solvent.

74. The startup process of any one of claims 64 to 73, wherein in the second composition, the deasphalting mobilizing solvent is changed to a second deasphalting mobilizing solvent.

75. The startup process of any one of claims 64 to 74, wherein the second composition enables the asphaltenes to remain substantially solubilized in the mobilized bitumen.

76. The startup process of any one of claims 64 to 74, wherein the second composition allows precipitation of at least a portion of the asphaltenes such that asphaltene precipitates are formed.

77. The process of claim 76, further comprising transitioning the startup up fluid from the second composition to a third composition.

78. The startup process of claim 77, wherein transitioning the startup fluid from the second composition to the third composition comprises a continuous transition.

79. The startup process of claim 77, wherein transitioning the startup fluid from the second composition to the third composition comprises a step transition.

80. The startup process of any one of claims 77 to 79, wherein the third composition has an increased amount of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the second composition.

81. The startup process of any one of claims 77 to 80, wherein the third composition is substantially free of the deasphalting mobilizing solvent.

82. The startup process of claim 80 or 81, wherein the third composition enables the asphaltenes to remain substantially solubilized in the mobilized bitumen.

83. The startup process of claim 82, further comprising maintaining the startup fluid in the third composition for a given period of time to resolubilize the asphaltene precipitates.

84. The startup process of any one of claims 77 to 79, wherein the third composition has a reduced amount of non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the second composition.

85. The startup process of claim 83 or 84, wherein maintaining the startup fluid in the third composition and recovering the mobilized bitumen as the production fluid from the interwell region via the production well is performed substantially simultaneously.

86. The startup process of claim 84 or 85, wherein the third composition allows precipitation of at least a portion of the asphaltenes.

87. The startup fluid of any one of claims 64 to 86, wherein the startup fluid further comprises steam.

88. The startup process of claim 64 to 87, wherein introducing the startup fluid into the bitumen-containing reservoir comprises:
vapourizing at least the non-deasphalting mobilizing solvent at surface to obtain a vapourized non-deasphalting mobilizing solvent;
combining the vapourized non-deasphalting mobilizing solvent with the deasphalting mobilizing solvent to obtain a vapourized startup fluid; and injecting the vapourized startup fluid into the interwell region via the injection well.

89. The startup process of any one of claims 64 to 87, wherein introducing the startup fluid into the bitumen-containing reservoir comprises vapourizing the startup fluid at surface to obtain the vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.

90. The startup process of any one of claims 64 to 87, wherein introducing the startup fluid into the bitumen-containing reservoir comprises heating the startup fluid as the startup fluid travels along the injection well to obtain a vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.

91. The startup process of claim 90, wherein heating the startup fluid as the startup fluid travels along the injection well comprises providing electrically heating using one or more electric resistive heaters in the injection well.

92. The startup process of any one of claims 88 to 91, wherein at least the first composition further enables formation of a startup chamber.

93. The startup process of claim 92, wherein recovering the mobilized bitumen via the production well and the formation of the startup chamber are performed substantially simultaneously.

94. The startup process of claim 92 or 93, further comprising determining startup chamber size.

95. The startup process of claim 94, wherein transitioning the startup fluid from the first composition to the second composition is performed when the startup chamber size has reached a pre-determined given size.

96. The startup process of any one of claims 77 to 86, wherein the startup fluid is introduced into the bitumen-containing reservoir as a vapourized startup fluid.

97. The startup process of claim 96, wherein at least the first composition further enables formation of a startup chamber.

98. The startup process of claim 97, further comprising determining startup chamber size.

99. The startup process of claim 98, wherein transitioning the startup fluid from the second composition to the third composition is performed when the startup chamber size has reached a given size.

100. The startup process of any one of claims 64 to 99, further comprising determining an amount of mobilized bitumen produced from the interwell region to assess bitumen de-saturation in the interwell region.

101. The startup process of claims 100, wherein when the amount of mobilized bitumen produced from the interwell region is above a given threshold, the first composition is transitioned to the second composition.

102. The startup process of any one of claims 64 to 101, further comprising monitoring a production variable related to recovering the production fluid.

103. The startup process of claim 102, wherein the production variable comprises a compositional characteristic of the production fluid.

104. The startup process of claim 103, wherein the compositional characteristic comprises a non-deasphalting mobilizing fluid concentration in the production fluid.

105. The startup process of claim 103 or 104, wherein the compositional characteristic of the production fluid comprises a deasphalting mobilizing fluid concentration in the production fluid.

106. The startup process of any one of claims 103 to 105, wherein the compositional characteristic of the production fluid comprises a bitumen concentration of the production fluid.

107. The startup process of any one of claims 103 to 106, wherein the compositional characteristic of the production fluid comprises an asphaltene content of the production fluid.

108. The startup process of any one of claims 103 to 107, wherein the compositional characteristic of the production fluid comprises an API gravity of the production fluid.

109. The startup process of any one of claims 64 to 108, wherein the non-deasphalting mobilizing fluid comprises an aromatic solvent.

110. The startup process of claim 109, wherein the aromatic solvent comprises toluene, diesel, xylene, or a combination thereof.

111. The startup process of claim 109 or 110, wherein the aromatic solvent comprises toluene.

112. The startup process of claim 109 or 110, wherein the aromatic solvent comprises diesel.

113. The startup process of claim 109 or 110, wherein the aromatic solvent comprises xylene.

114. The startup process of any one of claims 64 to 113, wherein the deasphalting mobilizing fluid comprises an alkane solvent.

115. The startup process of claim 114, wherein the alkane solvent comprises propane, butane, pentane, hexane, heptane, condensate, or a mixture thereof.

116. The startup process of claim 114 or 115, wherein the alkane solvent comprises propane.

117. The startup process of claim 114 or 115, wherein the alkane solvent comprises butane.

118. The startup process of claim 114 or 115, wherein the alkane solvent comprises pentane.

119. The startup process of claim 114 or 115, wherein the alkane solvent comprises condensate.

120. The startup process of any one of claims 64 to 119, further comprising separating the production fluid to remove water and solids therefrom to obtain a solvent-rich fluid.

121. The process of claim 120, further comprising separating the solvent-rich fluid to recover at least a portion of the deasphalting mobilizing solvent and obtain a recycled deasphalting mobilizing solvent suitable for reuse in the startup fluid, and a mixed bitumen and non-deasphalting mobilizing solvent stream.

122. The process of claim 121, further comprising separating the mixed bitumen and non-deasphalting mobilizing solvent stream to recover at least a portion of the non-deasphalting mobilizing solvent to obtain a recycled non-deasphalting mobilizing solvent suitable for reuse in the startup fluid.

123. The startup process of claim 121 or 122, wherein introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled deasphalting mobilizing solvent as part of the startup fluid.

124. The startup process of claim 122 or 123, wherein introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled non-deasphalting mobilizing solvent as part of the startup fluid.

125. A startup process for mobilizing bitumen in an interwell region, the interwell region being defined between a horizontal injection section of an injection well and a horizontal production section of a production well located below the horizontal injection section, the injection well and the production well being located in a bitumen-containing reservoir, the startup process comprising:
introducing a startup fluid comprising a non-deasphalting mobilizing solvent and a deasphalting mobilizing solvent into the bitumen-containing reservoir, the startup fluid being provided with a proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent such that the startup fluid has a first functionality, the first functionality comprising enabling asphaltenes to remain substantially solubilized in mobilized bitumen;
reducing the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent until the startup fluid reaches a second functionality; and recovering the mobilized bitumen from the interwell region as a production fluid to form a bitumen-depleted region that enables fluid communication between the injection well and the production well.

126. The startup process of claim 125, wherein the second functionality is a decreased solubility of asphaltenes in the mobilized bitumen.

127. The startup process of claim 126, wherein the decreased solubility of asphaltenes in the mobilized bitumen allows precipitation of at least a portion of the asphaltenes such that asphaltene precipitates are formed.

128. The startup process of any one of claims 125 to 127, wherein introducing the startup fluid into the bitumen-containing reservoir comprises injecting the startup fluid via the injection well.

129. The startup process of any one of claims 125 to 128, wherein introducing the startup fluid into the bitumen-containing reservoir comprises injecting the startup fluid via the production well prior to recovering the mobilized bitumen from the interwell region via the production well.

130. The startup process of any one of claims 125 to 129, wherein introducing the startup fluid into the bitumen-containing reservoir further comprises injecting the startup fluid via the production well cyclically between periods of recovering the mobilized bitumen from the interwell region via the production well.

131. The startup process of any one of claims 125 to 130, further comprising pre-heating the interwell region.

132. The startup process of claim 131, wherein pre-heating the interwell region comprises electrically heating using one or more electric resistive heaters in the injection well and/or the production well.

133. The startup process of claim 131 or 132, wherein pre-heating the interwell region comprises circulating steam through the injection well and/or the production well.

134. The startup process of any one of claims 125 to 132, wherein reducing the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent comprises a continuous transition.

135. The startup process of any one of claims 125 to 132, wherein reducing the proportion of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent comprises a step transition.

136. The startup fluid of any one of claims 125 to 135, wherein the startup fluid further comprises steam.

137. The startup process of claim 125 to 136, wherein introducing the startup fluid into the bitumen-containing reservoir comprises:
vapourizing at least the non-deasphalting mobilizing solvent at surface to obtain a vapourized non-deasphalting mobilizing solvent;
combining the vapourized non-deasphalting mobilizing solvent with the deasphalting mobilizing solvent to obtain a vapourized startup fluid; and injecting the vapourized startup fluid into the interwell region via the injection well.

138. The startup process of any one of claims 125 to 136, wherein introducing the startup fluid into the bitumen-containing reservoir comprises vapourizing the startup fluid at surface to obtain the vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.

139. The startup process of any one of claims 125 to 136, wherein introducing the startup fluid into the bitumen-containing reservoir comprises heating the startup fluid as the startup fluid travels along the injection well to obtain a vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.

140. The startup process of claim 139, wherein heating the startup fluid as the startup fluid travels along the injection well comprises providing electrically heating using one or more electric resistive heaters in the injection well.

141. The startup process of any one of claims 137 to 140, wherein at least the first functionality further comprises enabling formation of a startup chamber.

142. The startup process of claim 141, wherein recovering the mobilized bitumen via the production well and the formation of the startup chamber are performed substantially simultaneously.

143. The startup process of claim 141 or 142, further comprising determining startup chamber size.

144. The startup process of any one of claims 137 to 143, further comprising determining an amount of mobilized bitumen produced from the interwell region to assess bitumen de-saturation in the interwell region.

145. The startup process of any one of claims 137 to 144, further comprising monitoring a production variable related to recovering the production fluid.

146. The startup process of claim 145 wherein the production variable comprises a compositional characteristic of the production fluid.

147. The startup process of claim 146, wherein the compositional characteristic comprises a non-deasphalting mobilizing fluid concentration in the production fluid.

148. The startup process of claim 146 or 147, wherein the compositional characteristic of the production fluid comprises a deasphalting mobilizing fluid concentration in the production fluid.

149. The startup process of any one of claims 146 to 148, wherein the compositional characteristic of the production fluid comprises a bitumen concentration of the production fluid.

150. The startup process of any one of claims 146 to 149, wherein the compositional characteristic of the production fluid comprises an asphaltene content of the production fluid.

151. The startup process of any one of claims 146 to 150, wherein the compositional characteristic of the production fluid comprises an API gravity of the production fluid.

152. The startup process of any one of claims 137 to 151, wherein the non-deasphalting mobilizing fluid comprises an aromatic solvent.

153. The startup process of claim 152, wherein the aromatic solvent comprises toluene, diesel, xylene, or a combination thereof.

154. The startup process of claim 152 or 153, wherein the aromatic solvent comprises toluene.

155. The startup process of claim 152 or 153, wherein the aromatic solvent comprises diesel.

156. The startup process of claim 152 or 153, wherein the aromatic solvent comprises xylene.

157. The startup process of any one of claims 137 to 156, wherein the deasphalting mobilizing solvent comprises an alkane solvent.

158. The startup process of claim 157, wherein the alkane solvent comprises propane, butane, pentane, hexane, heptane, condensate, or a mixture thereof.

159. The startup process of claim 157 or 158, wherein the alkane solvent comprises propane.

160. The startup process of claim 157 or 158, wherein the alkane solvent comprises butane.

161. The startup process of claim 157 or 158, wherein the alkane solvent comprises pentane.

162. The startup process of claim 157 or 158, wherein the alkane solvent comprises condensate.

163. The startup process of any one of claims 137 to 162, further comprising separating the production fluid to remove water and solids therefrom to obtain a solvent-rich fluid.

164. The process of claim 163, further comprising separating the solvent-rich fluid to recover at least a portion of the deasphalting mobilizing solvent and obtain a recycled deasphalting mobilizing solvent suitable for reuse in the startup fluid, and a mixed bitumen and non-deasphalting mobilizing solvent stream.

165. The process of claim 164, further comprising separating the mixed bitumen and non-deasphalting mobilizing solvent stream to recover at least a portion of the non-deasphalting mobilizing solvent to obtain a recycled non-deasphalting mobilizing solvent suitable for reuse in the startup fluid.

166. The startup process of claim 164 or 165, wherein introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled deasphalting mobilizing solvent as part of the startup fluid.

167. The startup process of claim 165 or 166, wherein introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled non-deasphalting mobilizing solvent as part of the startup fluid.

168. A startup process for mobilizing bitumen in an interwell region, the interwell region being defined between a horizontal injection section of an injection well and a horizontal production section of a production well located below the horizontal injection section, the injection well and the production well being located in a bitumen-containing reservoir, the startup process comprising:

introducing a startup fluid comprising at least a non-deasphalting mobilizing solvent in vapour phase into the bitumen-containing reservoir, the startup fluid having a first functionality;
recovering mobilized bitumen from the interwell region as a production fluid to form a bitumen-depleted region that enables fluid communication between the injection well and the production well; and transitioning the startup fluid from the first functionality to a second functionality, comprising combining the non-deasphalting mobilizing solvent with a deasphalting mobilizing solvent;
wherein the first functionality of the startup fluid comprises a formation of a startup chamber around the injection well.

169. The startup process of claim 168, wherein transitioning the startup fluid from the first functionality to the second functionality comprises a continuous transition.

170. The startup process of claim 168, wherein transitioning the startup fluid from the first functionality to the second functionality comprises a step transition.

171. The startup process of any one of claims 168 to 170, wherein the second functionality is a decreased solubility of asphaltenes in the mobilized bitumen.

172. The startup process of any one of claims 168 to 171, wherein introducing the startup fluid into the bitumen-containing reservoir comprises injecting the startup fluid via the injection well.

173. The startup process of any one of claims 168 to 172, wherein introducing the startup fluid into the bitumen-containing reservoir comprises injecting the startup fluid via the production well prior to recovering the mobilized bitumen from the interwell region via the production well.

174. The startup process of any one of claims 168 to 173, wherein introducing the startup fluid into the bitumen-containing reservoir further comprises injecting the startup fluid via the production well cyclically between periods of recovering the mobilized bitumen from the interwell region via the production well.

175. The startup process of any one of claims 168 to 174, further comprising pre-heating the interwell region.

176. The startup process of claim 175, wherein pre-heating the interwell region comprises electrically heating using one or more electric resistive heaters in the injection well and/or the production well.

177. The startup process of claim 175 or 176, wherein pre-heating the interwell region comprises circulating steam through the injection well and/or the production well.

178. The startup fluid of any one of claims 168 to 177, wherein the startup fluid further comprises steam.

179. The startup process of claim 168 to 178, wherein introducing the startup fluid having the first functionality into the bitumen-containing reservoir in vapour phase comprises vapourizing the at least the non-deasphalting mobilizing solvent at surface to obtain a vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.

180. The startup process of any one of claims 168 to 178, wherein introducing the startup fluid having the first functionality into the bitumen-containing reservoir comprises heating the startup fluid as the startup fluid travels along the injection well to obtain a vapourized startup fluid and injecting the vapourized startup fluid into the interwell region via the injection well.

181. The startup process of claim 180, wherein heating the startup fluid as the startup fluid travels along the injection well comprises providing electrically heating using one or more electric resistive heaters in the injection well.

182. The startup process of any one of claims 168 to 181, wherein recovering the mobilized bitumen via the production well and the formation of the startup chamber are performed substantially simultaneously.

183. The startup process of any one of claims 168 to 182, further comprising transitioning the startup fluid from the second functionality to a third functionality, wherein the startup fluid having the third functionality has a reduced amount of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the startup fluid having the second functionality.

184. The startup process of any one of claims 168 to 183, further comprising determining startup chamber size.

185. The startup process of any one of claims 168 to 184, further comprising determining an amount of mobilized bitumen produced from the interwell region to assess bitumen de-saturation in the interwell region.

186. The startup process of any one of claims 168 to 185, further comprising monitoring a production variable related to recovering the production fluid.

187. The startup process of claim 186, wherein the production variable comprises a compositional characteristic of the production fluid.

188. The startup process of claim 187, wherein the compositional characteristic comprises a non-deasphalting mobilizing fluid concentration in the production fluid.

189. The startup process of claim 187 or 188, wherein the compositional characteristic of the production fluid comprises a deasphalting mobilizing fluid concentration in the production fluid.

190. The startup process of any one of claims 187 or 188, wherein the compositional characteristic of the production fluid comprises a bitumen concentration of the production fluid.

191. The startup process of any one of claims 187 or 188, wherein the compositional characteristic of the production fluid comprises an asphaltene content of the production fluid.

192. The startup process of any one of claims 187 or 188, wherein the compositional characteristic of the production fluid comprises an API gravity of the production fluid.

193. The startup process of any one of claims 168 to 182, wherein the non-deasphalting mobilizing solvent comprises an aromatic solvent.

194. The startup process of claim 193, wherein the aromatic solvent comprises toluene, diesel, xylene, or a combination thereof.

195. The startup process of claim 193 or 194, wherein the aromatic solvent comprises toluene.

196. The startup process of claim 193 or 194, wherein the aromatic solvent comprises xylene.

197. The startup process of any one of claims 168 to 196, wherein the deasphalting mobilizing fluid comprises an alkane solvent.

198. The startup process of claim 197, wherein the alkane solvent comprises propane, butane, pentane, hexane, heptane, condensate, or a mixture thereof.

199. The startup process of claim 197 or 198, wherein the alkane solvent comprises propane.

200. The startup process of claim 197 or 198, wherein the alkane solvent comprises butane.

201. The startup process of claim 197 or 198, wherein the alkane solvent comprises pentane.

202. The startup process of claim 197 or 198, wherein the alkane solvent comprises condensate.

203. The startup process of any one of claims 168 to 202, further comprising separating the production fluid to remove water and solids therefrom to obtain a solvent-rich fluid.

204. The process of claim 203, further comprising separating the solvent-rich fluid to recover at least a portion of the deasphalting mobilizing solvent and obtain a recycled deasphalting mobilizing solvent suitable for reuse in the startup fluid, and a mixed bitumen and non-deasphalting mobilizing solvent stream.

205. The process of claim 204, further comprising separating the mixed bitumen and non-deasphalting mobilizing solvent stream to recover at least a portion of the non-deasphalting mobilizing solvent to obtain a recycled non-deasphalting mobilizing solvent suitable for reuse in the startup fluid.

206. The startup process of claim 205, wherein introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled non-deasphalting mobilizing solvent as part of the startup fluid.

207. A startup process for mobilizing bitumen in an interwell region, the interwell region being defined between a horizontal injection section of an injection well and a horizontal production section of a production well located below the horizontal injection section, the injection well and the production well being located in a bitumen-containing reservoir, the startup process comprising:
introducing a startup fluid comprising a non-deasphalting mobilizing solvent and a deasphalting mobilizing solvent into the bitumen-containing reservoir via the injection well, the non-deasphalting mobilizing solvent and the deasphalting mobilizing solvent being provided in a first stage proportion;
recovering mobilized bitumen from the interwell region via the production well to form a bitumen-depleted region that enables fluid communication between the injection well and the production well; and transitioning the startup fluid from the first stage proportion to a second stage proportion, the second stage proportion having a reduced amount of the non-deasphalting mobilizing solvent relative to the deasphalting mobilizing solvent compared to the first stage proportion.

208. The startup process of claim 207, wherein transitioning the startup fluid from the first stage proportion to the second stage proportion comprises a continuous transition.

209. The startup process of claim 207, wherein transitioning the startup fluid from the first stage proportion to the second stage proportion comprises a step transition.

210. The startup process of any one of claims 207 to 209, wherein the second stage proportion enables precipitation of at least a portion of the asphaltenes such that asphaltene precipitates are formed.

211. The startup process of any one of claims 207 to 210, further comprising, following the transitioning of the startup fluid to the second stage proportion:
halting injection of the deasphalting mobilizing solvent;
injecting the non-deasphalting solvent; and shutting in the well for a given period of time to solubilize the asphaltene precipitates.