CA3102717A1 - Use of upgrader products for mobilizing bitumen during an in situ startup process - Google Patents

Abstract

A startup process for mobilizing bitumen in an interwell region is provided. The startup process can include introducing a startup fluid into a bitumen-containing reservoir via an injection well to mobilize bitumen in the interwell region, the startup fluid comprising a first and second upgrader products obtained from a vacuum distillation process for upgrading crude oil or a downstream process thereof, the first upgrader product having an aromatic content above 25%, and the second upgrader product having an API gravity below 200 , and recovering mobilized bitumen from the interwell region via a production well to form a bitumen-depleted region that enables fluid communication between the injection well and the production well. The startup fluid can be chosen to enable asphaltenes to remain substantially solubilized in the mobilized bitumen, and can include for instance light vacuum gas oil, and/or coker kerosene, and coker gas oil, and/or heavy vacuum gas oil.

Description

USE OF UPGRADER PRODUCTS FOR MOBILIZING BITUMEN 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.
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 (SAGD), although solvent is injected into the heavy hydrocarbon-bearing reservoir instead or along with steam.

[3] In an example of a 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, can be 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. Overtime, a production fluid including the mobilized hydrocarbons and Date Recue/Date Received 2020-12-15 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 startup procedures for in situ bitumen recovery processes and there is a need for enhanced technologies.
SUMMARY

[6] In accordance with an aspect, there is provided a startup process for mobilizing bitumen in an interwell region 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 into the bitumen-containing reservoir via at least the injection well to mobilize bitumen in the interwell region, the startup fluid comprising first and second upgrader products each obtained from a vacuum distillation process for upgrading crude oil or a downstream process thereof, the first upgrader product having an aromatic content above 25%, and the second upgrader product having an API gravity below 200; and 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;
wherein the startup fluid enables asphaltenes to remain substantially solubilized in the mobilized bitumen.

[7] In some implementations, the first upgrader product comprises light vacuum gas oil.

[8] In some implementations, the first upgrader product comprises coker kerosene.

[9] In some implementations, the second upgrader product comprises coker gas oil.
Date Recue/Date Received 2020-12-15

[10] In some implementations, the second upgrader product comprises heavy vacuum gas oil.

[11] In some implementations, the first upgrader product is provided in a proportion ranging from 80:20 to 20:80 ratio by mass relative to the second upgrader product.

[12] In some implementations, the startup fluid further comprises a third upgrader product obtainable from the vacuum distillation process for upgrading crude oil or the downstream process thereof.

[13] In some implementations, the aromatic content of the third upgrader product is above 25%.

[14] In some implementations, the third upgrader product comprises coker kerosene.

[15] In some implementations, the startup fluid further comprises a third upgrader product obtainable from a vacuum distillation process for upgrading crude oil or a downstream process thereof.

[16] In some implementations, the aromatic content of the third upgrader product is above 25%.

[17] In some implementations, the third upgrader product comprises light vacuum gas oil.

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

[19] In some implementations, the startup process further comprises heating the startup fluid at surface prior to introducing the startup fluid into the bitumen-containing reservoir.

[20] In some implementations, the startup process further comprises heating the startup fluid as the startup fluid travels along the injection well.

[21] In some implementations, heating the startup fluid as the startup fluid travels along the injection well is performed via at least one of radio-frequency (RF) heating, electric heating, and hot fluid closed-loop circulation.
Date Recue/Date Received 2020-12-15

[22] In some implementations, the electric heating comprises providing one or more electric resistive heaters in the injection well.

[23] In some implementations, the heating is performed via radio-frequency (RF) heating.

[24] In some implementations, the heating is performed via hot fluid closed-loop circulation.

[25] In some implementations, the heating is performed via closed-loop circulation.

[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, the startup process further comprises determining an amount of mobilized bitumen produced from the interwell region to assess bitumen de-saturation in the interwell region.

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

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

[31] In some implementations, the compositional characteristic comprises a concentration of the startup fluid in the production fluid.

[32] In some implementations, the compositional characteristic of the production fluid comprises a bitumen concentration of the production fluid.
Date Recue/Date Received 2020-12-15

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

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

[35] In some implementations, the startup process further comprises pre-heating the interwell region.

[36] 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.

[37] In some implementations, pre-heating the interwell region comprises circulating steam through the injection well and/or the production well.

[38] In some implementations, the startup process further comprises separating the production fluid to remove water and solids therefrom to obtain an upgrader product-rich fluid.

[39] In some implementations, the startup process further comprises separating the upgrader product-rich fluid to recover at least a portion of the first upgrader product and obtain a recycled first upgrader product suitable for reuse in the startup fluid, and a mixed bitumen and second upgrader product stream.

[40] In some implementations, the startup process further comprises separating the mixed bitumen and second upgrader product stream to recover at least a portion of the second upgrader product to obtain a recycled second upgrader product suitable for reuse in the startup fluid.

[41] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled first upgrader product as part of the startup fluid.
Date Recue/Date Received 2020-12-15

[42] In some implementations, introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled second upgrader product as part of the startup fluid.

[43] In some implementations, the startup process further comprises soaking a portion of the interwell region with the startup fluid for a period of time before recovering the production fluid.

[44] In accordance with another aspect, there is provided a startup process for mobilizing bitumen contained in a near-wellbore region of a bitumen-containing reservoir, the startup process comprising:
introducing a startup fluid into the bitumen-containing reservoir via a well extending within the bitumen-containing reservoir to mobilize the bitumen in the near-wellbore region, the startup fluid comprising coker gas oil and at least one of coker kerosene and light vacuum gas oil; and recovering mobilized bitumen from the near-wellbore region as a circulated fluid or a production fluid to form a bitumen-depleted region;
wherein the startup fluid enables asphaltenes to remain substantially solubilized in the mobilized bitumen.

[45] In some implementations, the startup fluid comprises coker kerosene and light vacuum gas oil.

[46] In some implementations, the well is an injection well and the recovering of the mobilized bitumen is performed via a production well located below the injection well.

[47] In accordance with another aspect, there is provided a startup fluid for introduction into a bitumen-containing reservoir to mobilize bitumen located in a near-wellbore region of the bitumen-containing reservoir, the startup fluid comprising:
first and second upgrader products each obtained from a vacuum distillation process for upgrading crude oil or a downstream process thereof, the first upgrader Date Recue/Date Received 2020-12-15 product having an aromatic content above 25%, and the second upgrader product having an API gravity below 200;
wherein the first and second upgrader products are selected and proportioned such that following introduction of the startup fluid into the bitumen-containing reservoir, the combination of the startup fluid and bitumen located in the near-wellbore region produces mobilized bitumen recoverable from the bitumen-containing reservoir to form a bitumen-depleted region in the near-wellbore region;
and wherein the startup fluid enables asphaltenes to remain substantially solubilized in the mobilized bitumen.

[48] In some implementations, the first upgrader product has an aromatic content above 30%.

[49] In some implementations, the second upgrader product has an API
gravity below 15 .

[50] In some implementations, the first upgrader product comprises light vacuum gas oil.

[51] In some implementations, the first upgrader product comprises coker kerosene.

[52] In some implementations, the second upgrader product comprises coker gas oil.

[53] In some implementations, the second upgrader product comprises heavy vacuum gas oil.

[54] In some implementations, the first upgrader product is provided in a proportion ranging from 80:20 to 20:80 ratio by mass% relative to the second upgrader product.

[55] In some implementations, the startup fluid further comprises a third upgrader product obtainable from the vacuum distillation process for upgrading crude oil or the downstream process thereof.
Date Recue/Date Received 2020-12-15

[56] In some implementations, the aromatic content of the third upgrader product is above 25%.

[57] In some implementations, the third upgrader product comprises coker kerosene.

[58] In some implementations, the startup fluid further comprises a third upgrader product obtainable from a vacuum distillation process for upgrading crude oil or a downstream process thereof.

[59] In some implementations, the aromatic content of the third upgrader product is above 25%.

[60] In some implementations, the third upgrader product comprises light vacuum gas oil.

[61] In some implementations, the first and third upgrader products are provided as a mixture in a proportion ranging from 80:20 to 20:80 ratio by mass% relative to the second upgrader product.

[62] In some implementations, the first and third upgrader products are provided as a mixture in a proportion ranging from 80:20 to 20:80 ratio by mass% relative to the second upgrader product.

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

[64] In some implementations, the startup fluid is heated at surface prior to being introduced into the bitumen-containing reservoir.

[65] In some implementations, the startup fluid is introducible into the bitumen-containing reservoir via an injection well extending within the bitumen-containing reservoir.

[66] In some implementations, the startup fluid is heated while traveling along the injection well.

[67] In accordance with another aspect, there is provided a startup process for mobilizing bitumen contained in a near-wellbore region of a bitumen-containing reservoir, the startup process comprising:
Date Recue/Date Received 2020-12-15 introducing a startup fluid into the bitumen-containing reservoir via a well extending within the bitumen-containing reservoir to mobilize the bitumen in the near-wellbore region, the startup fluid comprising a first upgrader product obtained from a vacuum distillation unit and a second upgrader product obtained from a coker unit; and recovering mobilized bitumen from the near-wellbore region to form a bitumen-depleted region;
wherein the startup fluid enables asphaltenes to remain substantially solubilized in the mobilized bitumen.

[68] In some implementations, the first upgrader fluid comprises coker kerosene.

[69] In some implementations, the first upgrader fluid comprises coker gas oil.

[70] In some implementations, the second upgrader fluid comprises light vacuum gas oil.

[71] In some implementations, the startup fluid further comprises a third upgrader product.

[72] In some implementations, the third upgrader product is obtained from the vacuum distillation unit or the coker unit.

[73] In some implementations, the first upgrader fluid comprises coker kerosene.

[74] In some implementations, the second upgrader fluid comprises light vacuum gas oil.

[75] In some implementations, the third upgrader product comprises coker gas oil.

[76] In some implementations, the well is an injection well and the recovering of the mobilized bitumen is performed via a production well located below the injection well.
Date Recue/Date Received 2020-12-15

[77] In accordance with another aspect, there is provided a startup process for mobilizing bitumen contained in a near-wellbore region of a bitumen-containing reservoir, the startup process comprising:
introducing a startup fluid into the bitumen-containing reservoir via a well extending within the bitumen-containing reservoir to mobilize the bitumen in the near-wellbore region, the startup fluid comprising first and second upgrader products obtained from a vacuum distillation unit or a downstream process thereof; and recovering mobilized bitumen from the near-wellbore region to form a bitumen-depleted region;
wherein in a first stage of the startup process, the first and second upgrader products are provided in a first stage proportion that enables asphaltenes to remain substantially solubilized in the mobilized bitumen; and wherein in a second stage of the startup process following the recovering of at least a portion of the mobilized bitumen, the first and second upgrader products are provided in a second stage proportion that induces asphaltenes precipitates to form in the mobilized bitumen.

[78] In some implementations, the first upgrader fluid comprises coker kerosene.

[79] In some implementations, the first upgrader fluid comprises light vacuum gas oil.

[80] In some implementations, the second upgrader fluid comprises coker gas oil.

[81] In some implementations, the well is an injection well and the recovering of the mobilized bitumen is performed via a production well located below the injection well.

[82] In accordance with another aspect, there is provided a startup system for mobilizing bitumen contained in a near-wellbore region of a bitumen-containing reservoir, the startup system comprising:
an injection well extending into the bitumen-containing reservoir;
Date Recue/Date Received 2020-12-15 a tubing string inserted into the injection well for introducing a startup fluid into the bitumen-containing reservoir to mobilize bitumen in the interwell region, the startup fluid comprising first and second upgrader products each obtained from a vacuum distillation process for upgrading crude oil or a downstream process thereof, the first upgrader product having an aromatic content above 25%, and the second upgrader product having an API gravity below 200; and a production well extending into the bitumen-containing reservoir and located below the horizontal injection section for recovering mobilized bitumen as a production fluid to form a bitumen-depleted region that enables fluid communication between the injection well and the production well.
BRIEF DESCRIPTION OF THE DRAWINGS

[83] 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.

[84] Figure 2 is a graph showing the aromatic content of five different diluents.

[85] Figure 3 is a graph showing yields of asphaltenes precipitates and toluene insoluble solids for five different diluents and for various concentrations of diluent in corresponding bitumen blends.

[86] Figure 4 is a graph showing the API density for five different diluents.

[87] Figure 5 is a graph showing the kinematic viscosity of five different diluents.

[88] Figure 6 is a graph showing yields of asphaltenes precipitates and toluene insoluble solids for blends of bitumen and diluent at room conditions, for different concentrations of diluent in the bitumen blend.

[89] Figure 7 is a graph showing yields of asphaltenes precipitates and toluene insoluble solids for blends of bitumen, diluent, and toluene at room conditions, for a Date Recue/Date Received 2020-12-15 concentration of 90 wt% of diluent in the bitumen blend and for various concentrations of toluene.

[90] Figure 8 is a graph showing yields of asphaltenes precipitates and toluene insoluble solids for blends of bitumen and diluent, and for bitumen alone, combined with various concentrations of pentane, at room conditions.

[91] Figure 9 is a graph showing yields of asphaltenes precipitates and toluene insoluble solids for blends of bitumen and diluent or combinations of diluents, with the shaded area indicating the range of measurement error from the toluene insoluble content which was 0.66 0.065 wt%.

[92] Figure 10 is a schematic representation of an example of a process for separating a production fluid that includes first and second upgrader fluids to produce a bitumen-rich stream.
DETAILED DESCRIPTION

[93] Techniques described herein relate to startup processes for mobilizing bitumen in a near-wellbore region of a bitumen-bearing reservoir in the context of in situ bitumen recovery operations. The startup process includes injecting a startup fluid into the bitumen-bearing reservoir, the startup fluid comprising one or more diluents obtained from a process for upgrading crude oil, such as a vacuum distillation process or a downstream process thereof. The diluents obtained from the crude oil upgrading process can be referred to as upgrader products. The choice of one or more upgrader products can be determined, for instance, in accordance with their aromatic content, their ability to maintain asphaltenes contained in the bitumen to be mobilized in solution, their viscosity, and/or their density. Examples of suitable diluents obtained from a crude oil upgrading process and that can be used as components of the startup fluid include light vacuum gas oil, coker gas oil, and coker kerosene. In some implementations, the startup fluid can include a first upgrader product and a second upgrader product. The first upgrader product can have for instance an aromatic content above 25%, and the second upgrader product can have for instance an API gravity below 20 . In some implementations, the first upgrader product can be, for example, light vacuum gas oil or coker kerosene, and the second upgrader product can be for example coker gas oil.
Date Recue/Date Received 2020-12-15

[94] A startup process typically includes at least two stages, and the startup fluid for mobilizing bitumen as described herein can be used for performing at least one of these two stages. The initial stage of the startup process generally includes introducing the startup fluid in liquid phase into the reservoir to enable mobilization of bitumen, for instance by reducing the viscosity of the bitumen and exerting a pressure on the bitumen to displace, while avoiding precipitation of asphaltenes contained in the bitumen within the reservoir to prevent clogging in proximity of the wells. In this initial stage of the startup process, which can also be referred to as a displacement stage, the startup fluid described herein is formulated such that the asphaltenes contained in the bitumen remain solubilized. In order to maintain the asphaltenes solubilized during the initial stage of the startup process, the selection and the proportion of the components of the startup fluid can be provided to arrive at desirable characteristics. In the present description, the term "components" refers to the upgrader products that can be used to make up all or part of the startup fluid. The components of the startup fluid and/or their proportion can also be varied over the course of the startup process as different objectives may be sought after.
For instance, at the beginning of the startup process, the composition of the startup fluid can be provided so that asphaltenes remain substantially solubilized in the mobilized bitumen, while later on in the startup process, e.g., when a certain amount of mobilized bitumen has been produced, the composition of the startup fluid can be adjusted so that some asphaltene precipitation occurs.

[95] Although the general concept of using the startup fluid described herein is presented in the context of an injection well overlying a production so as to define an interwell region there between, it is to be understood that the startup process can also be performed according to different well configurations, such as via an infill well that is located between two adjacent well assemblies, or a step-out well located beside an existing well assembly, such that the infill or step-out well may become hydraulically joined to other extraction chambers.

[96] 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 mobilization. The pre-heating step can be performed for a certain period of time until the bitumen has reached a certain temperature, for example, at which point the startup fluid can be injected into the subsurface formation or at which Date Recue/Date Received 2020-12-15 point the bitumen becomes flowable. This pre-heating can be performed by a downhole heater (e.g., electric resistance heater or a closed-loop fluid circulation heater), for example.

[97] After the startup fluid described herein has been introduced into the subsurface formation for a certain period of time corresponding to the initial stage of the startup process, the startup fluid can be modified or changed to another startup fluid to proceed with the second stage of the startup process which is typically aimed at growing a mobilizing fluid chamber. The mobilizing fluid chamber can be a chamber that will include steam, solvent, or both, which can depend on the mobilizing fluid that will be introduced into the subsurface formation during normal operations. Examples of solvents that can be used to grow a chamber can include paraffinic solvents, also referred to as alkanes, such as propane, butane, pentane, and natural gas condensates.

[98] After the second stage, the startup process can gradually be transitioned to normal operations and a production fluid that includes mobilized bitumen, water and solids can be recovered. The normal operations can be performed according to any known techniques, such as gravity drainage or cyclic stimulation techniques using steam, solvent, mixtures thereof, or other mobilizing fluids for injection. Examples of normal operation processes can include SAGD, ES-SAGD, solvent-assisted gravity drainage, solvent-dominated gravity drainage, cyclic steam or solvent stimulation, and so on.
The normal operations can include the injection of a mobilizing fluid, such as steam, solvent, non condensable gas, air, etc. The production process can include the injection of a paraffinic solvent, such as propane, butane, pentane, hexane or heptane, alone or in combination in various proportions, in vapour phase to enable condensation of the solvent within the extraction chamber above the injection well and dissolution into the bitumen to enhance mobilization and recovery via an underlying production well. It is also noted that the production stage can include multiple different recovery processes, e.g., SAGD
followed by solvent-assisted process or in situ combustion.

[99] A more detailed description of startup processes that can be part of an in situ bitumen recovery process and the startup fluid for use in such startup processes, as well as associated implementations, is provided below.
Date Recue/Date Received 2020-12-15 Startup process of an in situ bitumen recovery process

[100] As mentioned above, the startup process described herein facilitates mobilization of bitumen contained in a subsurface formation using a startup fluid as a mobilizing fluid, the startup fluid comprising one or more upgrader products obtained from a crude oil upgrading process. It is to be noted that in the context of the present description, the expressions "upgrader fluids" and "diluents" can be used interchangeably. 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. As mentioned above, it should be understood that the startup process described herein can be implemented in the context of various suitable subsequent in situ recovery processes 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 as a mobilizing fluid for introduction in the subsurface formation, sometimes with minor amounts of other fluids, whereas a solvent-assisted gravity drainage operation generally uses a solvent, with or without steam, for introduction into the subsurface formation. A solvent-dominated process uses mainly solvent with sometimes minor amounts of other fluids. Once the startup process is completed, normal recovery operations of the in situ recovery process can follow.

[101] Figure 1 shows an implementation of a startup process in the context of an in situ recovery process that is carried out via a horizontal well pair 10 provided in a 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 shown 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.

[102] 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 Date Recue/Date Received 2020-12-15 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.

[103] 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, to heat the startup fluid 26 prior to exiting from the tubing string 28.
In some implementations, heating the startup fluid as the startup fluid travels along the injection well can also be performed via other means, such as radio-frequency (RF) heating, closed-loop circulation of a hot fluid, or a combination thereof.

[104] In addition to heating the startup fluid 26 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., 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.
Date Recue/Date Received 2020-12-15 Characteristics of the startup fluid

[105] As mentioned above, the startup fluid comprises one or more upgrader products obtained from a crude oil upgrading process. Processes for upgrading, or refining, crude oil can include processes for separating heavier products from lighter ones, often to prepare products that are marketable.

[106] In brief, crude oil is generally initially processed in an atmospheric distillation column to separate components of the crude oil mixture into various fractions, or petrolatum cuts, according to their respective boiling points. Treatment of crude oil in an atmospheric distillation tower produces lighter fractions, including naphtha and refinery gas; medium fractions, including kerosene and diesel oil distillates; and heavier fractions, including atmospheric gas oils; while the heaviest fractions with the highest boiling points settle at the bottom of the atmospheric distillation column.

[107] The heaviest fractions, which are also sometimes referred to as atmospheric bottoms or atmospheric resid, are then typically treated in a vacuum distillation column to produce light fractions such as light vacuum gas oil (LVGO), and vacuum kerosene;
heavier fractions such as heavy vacuum gas oil (sometimes referred to as HVG0); and a vacuum residuum.

[108] The vacuum residuum can then be treated in a coker, such as a delayed coker, for cracking and conversion into lighter products such as coker gas oil (CGO) and coker kerosene (CK), coker distillate, and coker naphtha, while producing a heavy fraction that can include solid petroleum coke.

[109] Crude oil fractions produced from crude oil upgrading can have properties that can make them attractive for use as a startup fluid in the context of an in situ bitumen recovery process. For instance, diesel has been used as a mobilizing fluid in startup processes given that it is generally considered a non-deasphalting fluid and given its ability to dilute bitumen. However, the use of diesel as a mobilizing fluid can have drawbacks, for instance in terms of its cost, which can make it less attractive. Alternatives to diesel as a mobilizing fluid may thus be beneficial for use in startup processes.
Date Recue/Date Received 2020-12-15

[110] In some implementations, selection of potential candidates among the various crude oil fractions can be made according to economical considerations, and according to properties such as its aromatic content, viscosity, API gravity, density, ability to maintain asphaltenes in solution, etc. Fractions that may have a lesser economic value and that can be advantageously used as suitable mobilizing fluids in the context of an in situ bitumen recovery process can include, for instance, lighter fractions from a coker unit, such as coker kerosene and coker gas oil, as well as fractions from a vacuum distillation unit such as light vacuum gas oil and heavy vacuum gas oil.

[111] In some implementations, the startup fluid can include at least two upgrader products chosen from a crude oil upgrading process. When the startup fluid includes two or more upgrader products, the composition of the startup fluid can be varied over time by changing the amount or proportion of the upgrader products to advantageously leverage properties of the components with regard to their effect on bitumen during the startup process. This aspect will be discussed in further detail below.

[112] 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. A startup fluid suitable for use to establish hydraulic communication in the interwell region in the context of an in situ bitumen recovery process can be formulated such that when contacted with bitumen, the asphaltenes contained in the interwell region remain in solution, while enabling mobilization of bitumen in the interwell region via dissolution effects and promoting the flow of mobilized bitumen from the injection well to the production well. In some implementations, when referring to the asphaltenes remaining in solution or remaining substantially solubilized, it can mean that substantially all the asphaltenes remain in solution when contacted with the startup fluid.
In some implementations, when referring to the asphaltenes remaining substantially solubilized, it can mean that the asphaltenes remain in solution when contacted with the startup fluid, although some precipitation of asphaltenes can occur, in a limited amount, for instance in certain portions of the interwell region. When referring to the expression "a limited amount", it can mean that although some asphaltenes precipitation can occur, the extent of asphaltenes precipitation would not cause clogging in proximity of the wells. In Date Recue/Date Received 2020-12-15 other implementations, the startup fluid can be formulated such that a majority of the asphaltenes remain in solution when contacted therewith. In this context, the expression "a majority" can refer to more than 50% of the asphaltenes remaining solubilized. In such scenarios, the startup fluid can be referred to as a non-deasphalting mobilizing fluid or non-deasphalting startup fluid. Maintaining the asphaltenes in solution in the interwell region can be beneficial in the context of a displacement phase of a startup process, as 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.

[113] In the following paragraphs, additional details regarding certain characteristics of suitable components for the startup fluid will be provided.
Aromatic content of components of the startup fluid

[114] As mentioned above, the startup fluid is formulated such that when the startup fluid contacts the bitumen, the asphaltenes contained therein remain in solution. In some implementations, the aromatic content of the one or more diluents forming the startup fluid can be indicative of its associated property of maintaining asphaltenes in solution. The aromatic content of a diluent can also be indicative of its ability to dissolve in bitumen. In general, diluents having a lower aromatic content dissolve in bitumen less readily than those having a higher aromatic content. For instance, in some implementations, toluene can dissolve bitumen more readily than pentane, hexane or heptane. In that respect, it is to be noted that diesel obtained from an atmospheric distillation process of crude oil typically has a lower aromatic content than gas oil or kerosene produced from a coker unit, i.e., coker kerosene and coker gas oil.

[115] On the other hand, the ability of the diluent to dissolve bitumen based on its aromatic content may be balanced according to its ability to maintain asphaltenes in solution, as the two properties may not necessarily be directly proportional.
In other words, an upgrader product can have a high aromatic content but trigger a certain amount of asphaltene precipitation. For instance, a heavy vacuum gas oil may appear attractive Date Recue/Date Received 2020-12-15 given its high aromatic content, but such a heavy fraction can, in turn, potentially induce asphaltene precipitation when contacted with bitumen. Accordingly, finding a desired balance between the ability of the hydrocarbon solvent to dissolve in bitumen and its ability to maintain asphaltenes solubilized in bitumen may be key for a given startup fluid to be considered suitable as a component of the startup fluid.

[116] Crude oil upgrader fractions suitable for the startup fluid described herein can thus have a higher aromatic content than other startup fluids, such as diesel, to provide an enhanced capability to maintain asphaltenes in solution once in contact with bitumen, while still having an ability to dissolve in bitumen that is suitable to achieve the purpose of the startup fluid, i.e., to act as a non-deasphalting mobilizing fluid.
Examples of such suitable crude oil upgrader fractions include coker kerosene, light vacuum gas oil and coker gas oil.

[117] Figure 2 illustrates examples of aromatic content of five different upgrader products, i.e., vacuum kerosene, which can also be referred to as light vacuum gas oil, coker kerosene, heavy vacuum gas oil, coker gas oil and diesel. It can be seen from Figure 2 that vacuum kerosene, coker kerosene, heavy vacuum gas oil, coker gas oil each has a markedly higher aromatic content than diesel. More particularly, the vacuum kerosene sample, the coker kerosene sample, the heavy vacuum gas oil sample, and the coker gas oil sample shown in Figure 2 have an aromatic content of 30.8%, 39.6%, 39.5%
and 88.0%
respectively, whereas diesel the diesel sample has an aromatic content of 13.1%. This property of vacuum kerosene, coker kerosene, heavy vacuum gas oil, and coker gas oil can make these upgrader products attractive candidates for startup fluid given their ability to maintain asphaltenes in solution. It is to be noted that other characteristics of the upgrader product can come into play to influence its ability to perform as a non-deasphalting startup fluid. For instance, although heavy vacuum gas oil may have a higher aromatic content, it may perform less in terms of keeping asphaltenes in solution than other upgrader fluids having a high aromatic content.

[118] Figure 3 illustrates corresponding yields of asphaltenes precipitates and toluene insoluble solids for each of the five upgrader products mentioned above, i.e., vacuum kerosene (identified as light vacuum gas oil in the graph), coker kerosene, heavy vacuum gas oil, coker gas oil and diesel. The graph shows that heavy vacuum gas oil and diesel, Date Recue/Date Received 2020-12-15 when present in bitumen in a concentration above 70 wt%, led to an increased precipitation of asphaltenes compared to light vacuum gas oil, coker gas oil and coker kerosene. The asphaltene precipitation with the light vacuum gas oil, coker gas oil and coker kerosene remained lower than with diesel, even at concentrations up to 90 wt%.
Density and viscosity of components of the startup fluid

[119] In some implementations and as mentioned above, the startup fluids described herein can be used in a first phase of a startup process to mobilize bitumen contained in the interwell region. One of the sought-after properties of a startup fluid for mobilizing and displacing the bitumen is to have a viscosity and/or density that is close or similar to the viscosity and/or density of the bitumen to displace. Substantial differences in viscosity between the startup fluid and the bitumen to mobilize can contribute to early breakthrough of the mobilizing fluid from one well to another, which can in turn can lead to various drawbacks including inefficient displacement and/or conformance issues along the wells, which in turn can later on contribute to impair the development of the mobilizing fluid chamber. In that regard, diesel has a low viscosity relative to bitumen, which is another drawback of this conventional startup fluid.

[120] In that respect, upgrader products such as coker gas oil and heavy vacuum gas oil can provide advantages that make them suitable for use as startup fluids while avoiding drawbacks associated with conventional mobilizing fluids, as their respective API
(American Petroleum Institute) density and viscosity is closer to that of bitumen.

[121] Referring to Figure 4, there are shown values of API densities, also referred to as API gravity, for vacuum kerosene, coker kerosene, heavy vacuum gas oil, coker gas oil and diesel. More particularly, the vacuum kerosene sample, the coker kerosene sample, the heavy vacuum gas oil sample, and the coker gas oil sample have an API
density of 26.0 , 25.9 , 15.3 and 12.6 respectively, whereas diesel the diesel sample has an API density of 25.0 .

[122] Referring to Figure 5, there are shown values of kinematic viscosity for vacuum kerosene, coker kerosene, heavy vacuum gas oil, coker gas oil and diesel, with the viscosity of coker gas oil and heavy vacuum gas oil being higher than the viscosity of vacuum kerosene, coker kerosene, and diesel.
Date Recue/Date Received 2020-12-15

[123] These differences in API gravity and kinematic viscosity between various upgrader products and how they can be taken advantage of are discussed below.
Mixture of various up grader products to achieve a desired startup fluid

[124] In some implementations, and in view of the considerations presented above, the startup fluid can include a mixture of upgrader products that are chosen so as to achieve given characteristics of the resulting startup fluid.

[125] For instance, in some implementations, one or more upgrader products having an aromatic content within a given range can be blended, or mixed, with one or more upgrader having a viscosity that is closer to the viscosity of the bitumen to mobilize. This type of combination can take advantage of the properties of each of the upgrader products taken alone to yield a startup fluid having properties of its respective components in terms of maintaining the asphaltenes in solution in the bitumen to mobilize and also having a viscosity similar to the viscosity of bitumen to facilitate bitumen mobilization and conformance of the displacement process along the length of the wells.

[126] An example of a combination of upgrader products that can be blended to obtain a startup fluid for use as a non-deasphalting startup fluid in the context of an in situ recovery process is one that includes coker kerosene, light vacuum gas oil and coker gas oil. In this combination, one of the main purposes of the coker gas oil is to increase the viscosity of the startup fluid, while one of the main purposes of the coker kerosene and the light vacuum gas oil is to maintain the asphaltene in solution, although the aromatic content of the coker gas oil can also contribute to maintaining asphaltenes in solution as well. Of course, the proportion of each of the components of the startup fluid can be varied to achieve desired properties of the startup fluid.

[127] Another example of a combination of upgrader products that can be blended to obtain a startup fluid for use as a non-deasphalting startup fluid in the context of an in situ recovery process is one that includes light vacuum gas oil and coker gas oil.
In this combination, one of the main purposes of the coker gas oil is also to increase the viscosity of the startup fluid, while one of the main purposes of the light vacuum gas oil is to maintain the asphaltene in solution, although as mentioned above, the aromatic content of the coker gas oil can also contribute to maintaining asphaltenes in solution as well.
Date Recue/Date Received 2020-12-15

[128] The composition of the startup fluid can be expressed using various other units to illustrate the proportion of each of the upgrader products, such as units of vol% or mass%. Given units can be chosen for instance depending on the choice of the components in the startup fluid. In some implementations, the proportion of the upgrader products in the startup fluid can be expressed for instance with ratios by mass% expressed as A:B, with A representing a mixture of coker kerosene and light vacuum gas oil, and B
representing coker gas oil. Examples of proportions of upgraders products expressed as such can include proportions of 80:20, 70:30, 50:50, 30:70 and 20:80, to name a few. It is to be noted that these examples of proportions are given for illustrative purposes only, and that a wide range of proportions is possible and within the scope of the present description.
In addition, the proportion of coker kerosene and light vacuum gas oil can also vary as part of the component "A" of the startup fluid. For instance, in some implementations, the proportion of coker kerosene relative to the light vacuum gas oil can be increased or inversely, the proportion of coker kerosene relative to the light vacuum gas oil can be decreased. Alternatively and in accordance with the other example given above, the proportion of the upgrader products in the startup fluid can be expressed with ratios by mass% expressed as A:B, with A representing light vacuum gas oil, and B
representing coker gas oil, with examples of proportions of upgraders products expressed that can range from proportions of 80:20, 70:30, 50:50, 30:70 and 20:80, with of course several other options of proportions being suitable. The proportion of coker kerosene relative to the light vacuum gas oil, the proportions of coker kerosene and light vacuum gas oil relative to coker gas oil, and the proportion of light vacuum gas oil relative to coker gas oil, can depend for instance on the availability of such fractions from the upgrader facility, their cost, and/or on the capability of the resulting startup fluid to maintain asphaltene in solution in the bitumen to mobilize.

[129] In some implementations, the blend of coker kerosene and light vacuum gas oil can be combined with an upgrader product other than coker gas oil for increasing the viscosity of the startup fluid closer to a viscosity of bitumen. For instance, in some implementations, the startup fluid can include heavy gas oil combined with coker kerosene and light vacuum gas oil.

[130] Advantageously, the startup fluid described herein can have a versatile composition that can be adapted according to various factors, such as in accordance with Date Recue/Date Received 2020-12-15 the refinery production schedule. In other words, the proportions of the various upgrader products forming the startup fluid, and the upgrader products themselves, can be varied depending on what the refinery is producing and what is available to allocate to the preparation of the startup fluid.
Introduction of the startup fluid into the subsurface formation

[131] The startup fluid can be introduced into the subsurface formation via at least one well. In some implementations, introducing the startup fluid into the subsurface formation can include circulating the startup fluid down the at least one well such that the startup fluid contacts and dilute the bitumen to mobilize. Circulating the startup fluid can be an option for instance when hydraulic communication between the injection well and the production well has not been established yet, or after hydraulic communication has been established. Following dilution, a mixture of startup fluid and bitumen that has been diluted with the startup fluid flows back up to the surface via the well as circulated fluid and is then reintroduced into the subsurface formation in a circuit fashion. Over time, the content of bitumen diluted in the circulated fluid increases, at which point make-up startup fluid can be added and/or some of the bitumen can be removed to keep circulating the startup fluid.
In some implementations, introducing the startup fluid into the subsurface formation can include injecting the startup fluid into the subsurface formation, for instance by pumping the startup fluid down the at least well and pushing it into the reservoir without startup fluid coming back up the well. Injecting the startup fluid into the subsurface formation can be performed for instance when hydraulic communication has been established between the injection well and the production well.

[132] In some implementations, when the startup fluid includes more than one upgrader products, the upgrader products can be blended at surface to arrive at the desired composition of the startup fluid.

[133] In other implementations, the upgrader products can be introduced into the subsurface formation as distinct streams and be substantially mixed as the upgrader products travel down the well and/or upon introduction into the subsurface formation. In other implementations, still when the startup fluid includes more than one upgrader products, components of the startup fluid can be introduced into the subsurface formation Date Recue/Date Received 2020-12-15 in a staged fashion. For instance, components of the startup fluid that are known to maintain asphaltenes in solution, or solubilized, may be introduced in a first stage to prevent asphaltenes precipitation in proximity of the wells. Then, in a second stage, another component of the startup fluid may be additionally introduced into the subsurface formation. The second stage can be implemented for example once a given portion of bitumen has been produced to the surface to partially clear the interwell region. In some scenarios, the additional upgrader product can be one that induces a limited amount of asphaltenes precipitation, that has an increased viscosity, or any other characteristic that may make the additional upgrader product suitable for injection during a subsequent second stage.

[134] As mentioned above, the startup fluid can be introduced into the subsurface formation in liquid phase, i.e., exiting the injection well and/or the production well in liquid phase. The startup fluid can be heated at surface using various heating means (e.g., a direct fired heater or an indirect heat exchanger). The startup fluid can also be heated as it travels along the injection well by using electric heating such as one or more electric resistive heaters provided along the well.

[135] In some implementations, prior to the startup fluid being introduced 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 introduced into the subsurface formation while the heaters continue to impart heat to the reservoir.

[136] In some implementations, the start-up process can include controlling the startup temperature and/or a startup pressure of the startup fluid such that it is introduced into the subsurface formation within a given range of temperature and/or pressure.
Various devices and methods can be used to measure temperature and pressure at surface or downhole, such as gages, bubble tubes, thermocouples, fibers, etc. In some Date Recue/Date Received 2020-12-15 implementations, the temperature of the startup fluid can be selected to condition the region in proximity of the wells or the interwell region, by introducing the startup fluid as a heated startup fluid, to reach a desired production temperature tailored to a subsequent production process or stage.

[137] In some implementations, the startup fluid can be introduced into the subsurface formation intermittently to include a period when the injection of the startup fluid is stopped, so as to enable the startup fluid to soak within the subsurface formation for a given soaking period. In such implementations, the soaking period can be initiated for instance once a predetermined volume of the startup fluid has been introduced into the subsurface formation. Once the soaking period is terminated, the startup fluid can be recovered at surface and then introduced again into the subsurface formation and so on.
Various operating strategies can be implemented with the liquid startup composition.
Monitoring variables related to startup process

[138] Various variables can be monitored to determine when the startup fluid can be transitioned to another startup fluid aimed at growing a mobilizing fluid chamber during a second stage of the startup process, 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.

[139] Once the startup fluid has been introduced 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 startup fluid in the produced mobilized bitumen, the asphaltene content of the mobilized bitumen, and/or the API gravity of the mobilized bitumen.

[140] 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 Date Recue/Date Received 2020-12-15 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 subsequent growth of the mobilizing fluid chamber described herein. Sufficient bitumen de-saturation of the interwell region can be said to be achieved for instance when the startup fluid is found in high concentration in the production fluid (in which case the startup fluid 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.

[141] The asphaltene content of the produced mobilized bitumen can be assessed to determine whether the composition of 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.

[142]
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 Date Recue/Date Received 2020-12-15 threshold, the proportion or choice of upgrader product in the startup fluid can be modified to favor the solubilization of the asphaltenes.

[143] 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.

[144] 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. Monitoring the concentration of the startup fluid in the produced mobilized bitumen can be used to determine the timing of when the space can be considered clean enough that the startup fluid can be transitioned to a second startup fluid. 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 asphaltenes precipitates forming and impairing the flow of mobilized bitumen or clogging the wells is decreased.
Accordingly, the startup fluid can be transitioned for instance to another startup fluid that includes a paraffinic solvent such as propane, butane, pentane, and condensates, because it is no longer as relevant to keep asphaltenes in solution and the startup fluid can rather be optimized to further grow the mobilizing fluid chamber efficiently.

[145] Another option to determine when it can be appropriate to transition the startup fluid used to a second startup fluid 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.

[146] 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.
Date Recue/Date Received 2020-12-15

[147] 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 one or more upgrader products that enables the asphaltenes to remain solubilized in the mobilized bitumen. As the startup process evolves over time and the interwell region becomes cleaner, the startup fluid can be transitioned to include one or more upgrader products that induce a limited amount of asphaltene precipitation, as there is a lesser risk to clog the wells in this later stage of the startup process. For instance, in some implementations, the startup fluid can include at least two upgrader products that are provided in a first stage proportion that enables asphaltenes to remain substantially solubilized in the mobilized bitumen.
After a certain period of time, in a second stage of the startup process which can be for instance once at least a portion of mobilized bitumen has been recovered at surface as a circulated fluid or production fluid, the proportion of the upgrader products in the startup fluid can be transitioned to a second stage proportion that induces a limited amount of asphaltene precipitation in the mobilized bitumen.
Implementations related to separation of startup fluid from mobilized bitumen

[148] As mentioned above, the startup fluid is introduced into the subsurface formation, for instance via an injection well, to dilute and heat bitumen to produce mobilized bitumen.
When the startup fluid is introduced into the subsurface formation for circulation, a mixture of startup fluid and bitumen diluted therein, that can be referred to as circulated fluid, can be recovered at surface via the injection well, or the well via which it was introduced. When the startup fluid is introduced into the subsurface formation for injection via the injection well, mobilized bitumen can then drain into the production well and be recovered to the surface as a production fluid. Both techniques can eventually create a space around the injection well. The mixture of startup fluid and bitumen obtained following circulation, or the production fluid recovered from the production well following injection, can have a variable composition depending on the stage of the startup process. Depending on different factors, such as the composition of the circulated fluid or of the production fluid, the proportion of the startup fluid in the circulated fluid or the production fluid, as well as economic considerations, it may be desirable to subject the mixture of startup fluid and bitumen or the production fluid to a separation step to recover at least a portion of the startup fluid therefrom. The recovered startup fluid can then be used as a recycled startup Date Recue/Date Received 2020-12-15 fluid. In implementations where more than one upgrader products are present in the startup fluid, the difference between their respective vaporization temperatures can mean that different separation steps can be put in place to recover a given upgrader product.

[149] It is to be noted that in other implementations, it may be desirable to leave the startup fluid as part of the production fluid, for instance to achieve a desired viscosity and density and obtain a pipelinable production fluid because the presence of the upgrader fluid may act as a diluent. The mixture of the startup fluid and bitumen forming the production fluid can also represent a valuable standalone marketable product.

[150] With reference to Figure 10, a circulated fluid of a production fluid 42 is recovered during the startup process. The production fluid includes mobilized bitumen, water, solids and at least a portion 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 an upgrader product-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 upgrader product-rich fluid 48 is then subjected to a second separation 50. The second separation 50 can be configured to recover at least one of the upgrader products forming the startup fluid, or to recover more than one upgrader product if present. For instance, if the startup fluid includes coker kerosene and coker gas oil, the difference in their respective vaporization temperature may be sufficiently large for implementing the second separation step 50 to selectively separate the coker gas oil, which has a lower vaporization temperature than the vaporization temperature of coker kerosene, as a first upgrader product from a mixture of bitumen and coker kerosene, and to recover a first upgrader product stream 52 comprising the coker gas oil and the mixture of bitumen and coker kerosene stream 54. In this scenario, the coker kerosene would thus be considered a second upgrader product. It is to be understood that coker kerosene and coker gas oil are given as examples only to illustrate the general principle of separation steps that can be implemented to recover a recycled startup fluid and a bitumen-rich stream. Other upgrader products can of course be used and separated in accordance with the general principle described herein.

[151] The second separation 50 can be performed for instance in a flash vessel through evaporation mechanisms to flash the first upgrader product from the upgrader product-Date Recue/Date Received 2020-12-15 rich fluid 48. As mentioned above, this separation technique can advantageously leverage the difference in vaporization temperature between the first and second upgrader products that may be present in the startup fluid, such that the first upgrader product can be selectively separated. The recovered first upgrader product can be reused as a component of the startup fluid for reintroduction into the subsurface formation.

[152] In other implementations, when the startup fluid includes a first and second upgrader products that have a respective vaporization temperature within a close range, such as a closer range than for coker kerosene and coker gas oil for example, the second separation 50 may be implemented to separate both the first and second upgrader products at the same time according to the lowest vaporization temperature of the first and second upgrader products to recover a first upgrader product stream 52 comprising the first and second upgrader products and a bitumen stream 54. In such scenario, the startup fluid could include for instance light vacuum gas oil and coker kerosene, or any other upgrader products having a vaporization temperature within a close range.

[153] In yet other implementations, the startup fluid can include three upgrader products. The second separation 50 may be implemented to separate a first and second upgrader products having a respective vaporization temperature within a certain range, from a mixture of bitumen and a third upgrader product having a vaporization temperature that if different enough from the first and second upgrader products. For example, in some implementations, the first and second upgrader products can be coker kerosene and light vacuum gas oil, and the third upgrader can be coker gas oil or heavy vacuum gas oil.

[154] When an additional separation step is desired, the mixture of bitumen and second upgrader product 54 (or third upgrader product) can be separated in a third separation 56 to recover the second or third upgrader product 58 and a bitumen-rich stream 60. In some implementations, the bitumen-rich stream 60 can then be further processed to obtain a suitable bitumen product.

[155] 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.
Date Recue/Date Received 2020-12-15 EXPERIMENTATION

[156] Various experiments were conducted to illustrate some characteristics of the startup fluid described herein. Description of experiments performed, and corresponding results are presented below.

[157] Experiments were conducted to assess asphaltene precipitation yield measurements for bitumen diluted with five diluents at ambient temperature and atmospheric pressure. As used in the context of the experiments performed and described below, the term "diluent" refers to upgrader products that have been used to dilute bitumen samples to evaluate asphaltene precipitation. These five diluents are diesel, distillate kerosene (DK), which can also be referred to as coker kerosene, light vacuum gas oil (LVGO), distillate gas oil (DGO), which can also be referred to as coker gas oil, and heavy vacuum gas oil (HVGO). Four types of experiments were conducted.

[158] In a first set of experiments, the yields of asphaltenes precipitates were measured at five different diluent contents, or concentration. The bitumen samples diluted with the various diluents were also assessed for their toluene insoluble content.

[159] In a second set of experiments, for experiments where asphaltene precipitation was observed for a given combination of bitumen samples a diluent, the onset of precipitation was determined. For four diluents, Le., DK, LVGO, DGO and HVGO, the onset of asphaltene precipitation was measured for mixtures of 10 wt% bitumen and 90 wt% diesel with toluene at ambient temperature and atmospheric pressure for different toluene contents to determine the amount of toluene required to prevent precipitation.

[160] In a third set of experiments, yields of asphaltenes precipitates were measured for blends of 50 wt% bitumen and 50 wt% diluent diluted with n-pentane at ambient temperature and atmospheric pressure. Three diluents were assessed, i.e., diesel, and DK, DGO, and tests were also performed on undiluted bitumen. Yields of asphaltenes precipitates were measured at a minimum of 5 different n-pentane contents.

[161] In a fourth set of experiments, yields of asphaltenes precipitates were measured for bitumen diluted with mixtures of DK and DGO diluents at 70:30, 50:50, and 30:70 ratios Date Recue/Date Received 2020-12-15 by mass at ambient temperature and atmospheric pressure. Yields of asphaltenes precipitates were measured at a minimum of 5 different diluent contents.

[162] The water content of the bitumen sample was measured with the Karl Fischer method and was determined to be 2.34 wt%. The toluene insoluble (TI) content on a dry basis was determined to be 0.66 wt%.

[163] To measure the yields of asphaltenes precipitates and solids content of the samples evaluated, a known mass of bitumen (approximately 1.5 g) was placed in a centrifuge tube and diluted with the selected solvent to arrive at the target diluent content.
The mixture was sonicated for 45 minutes and left to settle for 24 hours.
After the settling period, the tube was centrifuged for 6 minutes at 6000 rpm. The supernatant was then decanted to leave a mass of asphaltenes and solids with some residual maltenes. This mass was washed with pentane, sonicated, and centrifuged twice as described above, leaving the asphaltenes, solids, and some pentane. At this point the tube and contents are dried in a vacuum oven and weighed to obtain the total mass of asphaltenes and solids in the sample.

[164] The solids content of the bitumen was determined starting from 10 g of bitumen diluted to toluene and washed until the toluene is colorless. Then, the tube and solids were dried in a vacuum oven and weighed to obtain the solids content.

[165] The "solids" are thus defined as the toluene insolubles obtained from an asphaltene and solids precipitate. The asphaltene content is simply the asphaltene-solids content less the solids content. The repeatability of the contents is usually +1- 0.15 wt%.

[166] The diluents are more viscous than pure hydrocarbon solvents and it is more challenging to mix the bitumen with the diluent and to separate the precipitated asphaltenes. Thus, to measure the yields of asphaltenes precipitates when blended with a given diluent, sonication times were increased for each diluent as required to ensure complete mixing. The centrifuge times were increased to 8 minutes except for HVGO (the most viscous sample) which was increased to 12 minutes.

[167] The diluents also contain non-volatile material that does not evaporate during the drying procedure and artificially adds to the apparent asphaltene yield.
Therefore, a pure Date Recue/Date Received 2020-12-15 hydrocarbon solvent was used for the washing step. If the diluent did not contain asphaltenes, the standard procedure was followed except that the precipitate was washed with n-pentane instead of the diluent. If the diluent contained asphaltenes, the standard procedure was followed except that the precipitate was washed with cyclohexane instead of the diluent. The yields from the diluted bitumen were corrected to account for the amount of precipitation expected from the diluent itself.
Results ¨ First and second sets of experiments

[168] The yields of asphaltenes precipitates for the mixtures of bitumen and the five diluents, i.e., diesel, DK, LVGO, DGO and HVGO, are shown in Figure 6, and the yields of asphaltenes precipitates from the mixtures of bitumen and toluene/diluent blend are shown in Figure 7. The yields of asphaltenes precipitates are reported on a dry basis and their repeatability was 0.065 wt%. The results shown in Figures 6 and 7 are summarized in Table 1 below, which shows the required mixing time, the onset of precipitation, and the minimum amount of toluene in the diluent blend required to prevent precipitation (2 g bitumen at 90 wt% diluent blend).
Table 1: Required mixing time, diluent content at the onset of precipitations, and minimum amount of toluene in diluent blend required to prevent precipitation, all at room conditions. The uncertainties of the onset and toluene content are 3 and wt%, respectively.
Mixing Time Onset Minimum Toluene Diluent hr wt% Content, wt%
Diesel 4 70 13 DK 2.5 none LVGO 3.5 90 -DGO 7.5 72 16 Date Recue/Date Received 2020-12-15 Results ¨ Third set of experiments

[169] Figure 8 compares the yields of asphaltenes precipitates for blends of 50 wt%
bitumen and 50 wt% diluent, each diluted with n-pentane. In such experiments, when less n-pentane was required to precipitate asphaltenes, it was considered that the blends were less efficient at solubilizing asphaltenes. Figure 8 shows that the blend of bitumen and DGO, and the blend of bitumen and DK were slightly poorer solvents for maintaining asphaltenes in solution, or solubilized, compared to a sample of bitumen that was not diluted with a diluent. In addition, Figure 8 also shows that the blend of bitumen and diesel was a significantly poorer solvent compared to the blend of bitumen and DGO
and the blend of bitumen and DK. The data shown in Figure 8 illustrates a solubility trend among the diluents that is consistent with Figure 6 where the yields of asphaltenes precipitates were higher in samples of bitumen diluted with diesel than in samples of bitumen diluted with either DGO or DK.
Results ¨ Fourth set of experiments

[170] Turning now to Figure 9, the graph shows yields of asphaltenes precipitates from bitumen diluted with DGO and DK over dilutions ranging from 50 wt% to 90 wt%.
The two diluents were used alone, and also combined together at different ratios. The different ratios used were a blend of 70 wt% of DK combined with 30 wt% of DGO (referred to as 70:30 DK:DGO), a blend of 50 wt% of DK combined with 50 wt% of DGO (referred to as 50:50 DK:DGO), and a blend of 30 wt% of DK combined with 70 wt% of DGO
(referred to as 30:70 DK:DGO). No asphaltenes precipitation was observed when DK was used alone and for the 70:30 DK:DGO blend, across the dilution range studied. A limited amount of precipitation was observed with the DGO, the 50:50 DK:DGO, and the 70:30 DK:DGO
blend. However, the amount of asphaltenes precipitation was barely above the error of the measurements and the onsets of precipitation, which can be seen as the change in slope of the respective fitted lines. The shaded area represents the range of measurement error from the toluene insoluble content which was 0.66 0.065 wt%. Figure 9 thus shows that DK can be mixed with DGO at different ratios and be a suitable mixture that can be used as a startup fluid to dilute bitumen while avoiding precipitation of asphaltenes in the mixture, i.e., maintaining asphaltenes substantially solubilized in the bitumen, the mixture having a viscosity that is closer to bitumen than when DK would be used alone.
Date Recue/Date Received 2020-12-15

[171] Tables 2 to 9 provided below illustrate raw data obtained from experiments that were conducted.

[172] Tables 2 to 6 show yields of asphaltenes precipitates and toluene insoluble fraction for samples of bitumen and diesel, DK, DGO, LVGO or HVGO that were blended in concentrations ranging from 50 wt% to 90 wt%. These results are also shown in Figure 6. As discussed previously, these raw data show that diesel and HVGO are less suitable to maintain asphaltenes in solution, whereas DK, DGO and LVGO maintained asphaltenes in solution at least up to a dilution range of 90 wt% for DK and LVGO, and 80 wt% for DGO.
Table 2. Yield of asphaltenes and toluene insoluble from mixtures of bitumen and diesel at room conditions.
Diluent Content in Feed Yield, wt%
wt% Run 1 Run 2 50 0.63 -60 0.67 -70 0.64 0.67 80 0.76 0.82 90 0.91 0.94 Table 3. Yield of asphaltenes and toluene insoluble from mixtures of bitumen and kerosene at room conditions.
Diluent Content in Feed Yield, wt%
wt% Run 1 Run 2 50 0.62 -61 0.64 -70 0.65 0.62 80 0.65 0.67 90 0.66 0.64 Date Recue/Date Received 2020-12-15 Table 4. Yield of asphaltenes and toluene insoluble from mixtures of bitumen and light vacuum gas oil (LVGO) at room conditions.
Diluent Content in Feed Yield, wt%
wt% Run 1 Run 2 50 0.61 -61 0.63 -70 0.62 0.62 80 0.66 0.67 90 0.69 0.69 Table 5. Yield of asphaltenes and toluene insoluble from mixtures of bitumen and distillate gas oil (DGO) at room conditions.
Diluent Content in Feed Yield, wt%
wt% Run 1 Run 2 50 0.62 -60 0.62 -70 0.65 0.65 80 0.72 0.70 90 0.77 0.79 Table 6. Yield of asphaltenes and toluene insoluble from mixtures of bitumen and heavy vacuum gas oil (HVGO) at room conditions.
Diluent Content in Feed Yield, wt%
wt% Run 1 Run 2 50 0.62 -60 0.72 -70 0.64 0.62 80 1.33 1.38 90 2.08 2.10

[173] Table 7 shows the yields of asphaltene precipitation and toluene insoluble fraction for mixtures of bitumen and either diesel, DGO or HVGO, each provided at a concentration Date Recue/Date Received 2020-12-15 of 90 wt%. The concentration of toluene was increased from 0 wt% to 20 wt%. As described above for Figure 7, these results show that when no toluene was present, the yields of asphaltene precipitation was lower for DGO than for the other diluents diesel and HVGO. As the toluene concentration increased, the yields of asphaltene precipitation remained lower for DGO until at 15 wt%, when it became similar between diesel and DGO
while it remained higher for HVGO. At a concentration of 20 wt%, the three diluents diesel, DGO and HVGO were similar at preventing asphaltenes precipitation. These results show that DGO can advantageously prevent asphaltenes precipitation even when no toluene is present. Thus, in some implementation, DGO can perform better than diesel as a startup fluid aimed at preventing asphaltene precipitation in proximity of the wells.
Table 7. Yield of asphaltenes and toluene insoluble from mixtures of bitumen and three diluents (diesel, DGO, and HVGO) each diluted with toluene at room conditions. The mixtures were prepared with 90 wt% blend in the feed in all cases.
Toluene Content in Yield, wt%
Diluent Blend, wt% Diesel DGO HVGO
0 0.92 0.78 2.09 0.80 0.74 1.68 0.74 0.71 1.33 0.64 0.63 0.95 0.63 0.69 0.69

[174] In Table 8, the experiments were performed to assess the onset of asphaltene precipitation when increasing amounts of pentane were added to bitumen and diluent blends. In these experiments, DK, DGO and diesel were used, as well as bitumen that was not mixed with any diluent. These results are also shown in Figure 8.
According to the results shown in Table 8, the blends of bitumen and DGO or DK performed better than diesel at maintaining asphaltenes in solution up to a concentration of 60 wt%
of pentane, whereas asphaltene precipitation was significantly increased at a concentration of 45 wt%
of pentane for the blend of bitumen and diesel. Similar results were obtained for diesel, DGO and bitumen alone at concentrations of pentane above 60wt%, while the blend of bitumen and DK showed a lower level of asphaltene precipitation even at concentrations higher than 60 wt% of pentane.
Date Recue/Date Received 2020-12-15 Table 8. Yield of asphaltenes and toluene insoluble from bitumen or blends of wt% bitumen and 50 wt% diluent each diluted with n-pentane at room conditions.
n-Pentane Content Yield, wt%
wt% Bitumen DGO Diesel 35 - 1.0 1.0 1.4 40 - 1.1 1.0 1.9 45 0.8 1.1 1.1 4.8 50 1.3 2.5 2.5 7.1 55 5.0 - - 9.3 60 9.9 10.7 8.3 11.5 70 16.0 15.0 12.8 15.1 80 17.8 17.0 15.7 17.0 90 18.7 17.3 16.9 18.2 90 18.6 17.5 16.9 -

[175] Table 9 shows yields of asphaltenes precipitation for blends of bitumen mixed with a combination of two diluents, i.e., DK and DGO, provided at different ratios defined above in reference to Figure 9. As also seen in Figure 9, the blend comprising bitumen and a ratio of 70:30 DK:DGO enabled maintaining asphaltene substantially solubilized over the range of concentrations of the mixture of diluents in the bitumen.
The other ratios of 50:50 DK:DGO and 30:70 DK:DGO appeared to have performed similarly in maintaining the asphaltenes in solution, and appeared to perform better than DGO alone.
Table 9. Yield of asphaltenes and toluene insoluble from mixtures of bitumen with blends of DK and DGO at room conditions.
Blend Content in Feed Yield, wt%
wt% 70:30 DK:DGO 50:50 DK:DGO 30:70 DK:DGO
50 0.69 0.61 0.63 60 0.68 0.65 0.55 70 0.64 0.63 0.57 80 0.70 0.65 0.63 90 0.68 0.75 0.78 Date Recue/Date Received 2020-12-15

Claims (77)

40

1. A startup process for mobilizing bitumen in an interwell region 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 into the bitumen-containing reservoir via at least the injection well to mobilize bitumen in the interwell region, the startup fluid comprising first and second upgrader products each obtained from a vacuum distillation process for upgrading crude oil or a downstream process thereof, the first upgrader product having an aromatic content above 25%, and the second upgrader product having an API gravity below 20 ; and 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;
wherein the startup fluid enables asphaltenes to remain substantially solubilized in the mobilized bitumen.

2. The startup process of claim 1, wherein the first upgrader product comprises light vacuum gas oil.

3. The startup process of claim 1, wherein the first upgrader product comprises coker kerosene.

4. The startup process of any one of claims 1 to 3, wherein the second upgrader product comprises coker gas oil.

5. The startup process of any one of claims 1 to 3, wherein the second upgrader product comprises heavy vacuum gas oil.
Date Recue/Date Received 2020-12-15

6. The startup fluid of any one of claims 1 to 5, wherein the first upgrader product is provided in a proportion ranging from 80:20 to 20:80 ratio by mass relative to the second upgrader product.

7. The startup process of claim 2, wherein the startup fluid further comprises a third upgrader product obtainable from the vacuum distillation process for upgrading crude oil or the downstream process thereof.

8. The startup process of claim 7, wherein the aromatic content of the third upgrader product is above 25%.

9. The startup process of claim 8, wherein the third upgrader product comprises coker kerosene.

10. The startup process of claim 3, wherein the startup fluid further comprises a third upgrader product obtainable from a vacuum distillation process for upgrading crude oil or a downstream process thereof.

11. The startup process of claim 10, wherein the aromatic content of the third upgrader product is above 25%.

12. The startup process of claim 11, wherein the third upgrader product comprises light vacuum gas oil.

13. The startup process of any one of claims 1 to 12, wherein the startup fluid further comprises steam.

14. The startup process of any one of claims 1 to 13, further comprising heating the startup fluid at surface prior to introducing the startup fluid into the bitumen-containing reservoir.

15. The startup process of any one of claims 1 to 14, further comprising heating the startup fluid as the startup fluid travels along the injection well.

16. The startup process of claim 15, wherein heating the startup fluid as the startup fluid travels along the injection well is performed via at least one of radio-frequency (RF) heating, electric heating, and hot fluid closed-loop circulation.
Date Recue/Date Received 2020-12-15

17. The startup process of claim 16, wherein the electric heating comprises providing one or more electric resistive heaters in the injection well.

18. The startup process of claim 16, wherein the heating is performed via radio-frequency (RF) heating.

19. The startup process of claim 16, wherein the heating is performed via hot fluid closed-loop circulation.

20. The startup process of claim 16, wherein the heating is performed via closed-loop circulation.

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 1 to 22, further comprising determining an amount of mobilized bitumen produced from the interwell region to assess bitumen de-saturation in the interwell region.

24. The startup process of any one of claims 1 to 23, further comprising monitoring a production variable related to recovering the production fluid.

25. The startup process of claim 24 wherein the production variable comprises a compositional characteristic of the production fluid.

26. The startup process of claim 25, wherein the compositional characteristic comprises a concentration of the startup fluid in the production fluid.

27. The startup process of claim 25 or 26, wherein the compositional characteristic of the production fluid comprises a bitumen concentration of the production fluid.
Date Recue/Date Received 2020-12-15

28. The startup process of any one of claims 25 to 27, wherein the compositional characteristic of the production fluid comprises an asphaltene content of the production fluid.

29. The startup process of any one of claims 25 to 28, wherein the compositional characteristic of the production fluid comprises an API gravity of the production fluid.

30. The startup process of any one of claims 1 to 29, further comprising pre-heating the interwell region.

31. The startup process of claim 30, 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.

32. The startup process of claim 30 or 31, wherein pre-heating the interwell region comprises circulating steam through the injection well and/or the production well.

33. The startup process of any one of claims 1 to 32, further comprising separating the production fluid to remove water and solids therefrom to obtain an upgrader product-rich fluid.

34. The startup process of claim 33, further comprising separating the upgrader product-rich fluid to recover at least a portion of the first upgrader product and obtain a recycled first upgrader product suitable for reuse in the startup fluid, and a mixed bitumen and second upgrader product stream.

35. The startup process of claim 34, further comprising separating the mixed bitumen and second upgrader product stream to recover at least a portion of the second upgrader product to obtain a recycled second upgrader product suitable for reuse in the startup fluid.

36. The startup process of claim 34 or 35, wherein introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled first upgrader product as part of the startup fluid.
Date Recue/Date Received 2020-12-15

37. The startup process of claims 35 or 36, wherein introducing the startup fluid into the bitumen-containing reservoir comprises introducing at least a portion of the recycled second upgrader product as part of the startup fluid.

38. The startup process of any one of claims 1 to 37, further comprising soaking a portion of the interwell region with the startup fluid for a period of time before recovering the production fluid.

39. A startup process for mobilizing bitumen contained in a near-wellbore region of a bitumen-containing reservoir, the startup process comprising:
introducing a startup fluid into the bitumen-containing reservoir via a well extending within the bitumen-containing reservoir to mobilize the bitumen in the near-wellbore region, the startup fluid comprising coker gas oil and at least one of coker kerosene and light vacuum gas oil; and recovering mobilized bitumen from the near-wellbore region as a circulated fluid or a production fluid to form a bitumen-depleted region;
wherein the startup fluid enables asphaltenes to remain substantially solubilized in the mobilized bitumen.

40. The startup process of claim 39, wherein the startup fluid comprises coker kerosene and light vacuum gas oil.

41. The startup process of claim 39 or 40, wherein the well is an injection well and the recovering of the mobilized bitumen is performed via a production well located below the injection well.

42. A startup fluid for introduction into a bitumen-containing reservoir to mobilize bitumen located in a near-wellbore region of the bitumen-containing reservoir, the startup fluid comprising:
first and second upgrader products each obtained from a vacuum distillation process for upgrading crude oil or a downstream process thereof, the first upgrader product having an aromatic content above 25%, and the second upgrader product having an API gravity below 20 ;
Date Recue/Date Received 2020-12-15 wherein the first and second upgrader products are selected and proportioned such that following introduction of the startup fluid into the bitumen-containing reservoir, the combination of the startup fluid and bitumen located in the near-wellbore region produces mobilized bitumen recoverable from the bitumen-containing reservoir to form a bitumen-depleted region in the near-wellbore region; and wherein the startup fluid enables asphaltenes to remain substantially solubilized in the mobilized bitumen.

43. The startup fluid of claim 42, wherein the first upgrader product has an aromatic content above 30%.

44. The startup fluid of claim 42 or 43, wherein the second upgrader product has an API
gravity below 15 .

45. The startup fluid of any one of claims 42 to 44, wherein the first upgrader product comprises light vacuum gas oil.

46. The startup fluid of any one of claims 42 to 44, wherein the first upgrader product comprises coker kerosene.

47. The startup fluid of any one of claims 42 to 46, wherein the second upgrader product comprises coker gas oil.

48. The startup fluid of any one of claims 42 to 46, wherein the second upgrader product comprises heavy vacuum gas oil.

49. The startup fluid of any one of claims 42 to 48, wherein the first upgrader product is provided in a proportion ranging from 80:20 to 20:80 ratio by mass% relative to the second upgrader product.

50. The startup fluid of claim 45, wherein the startup fluid further comprises a third upgrader product obtainable from the vacuum distillation process for upgrading crude oil or the downstream process thereof.
Date Recue/Date Received 2020-12-15

51. The startup fluid of claim 50, wherein the aromatic content of the third upgrader product is above 25%.

52. The startup fluid of claim 51, wherein the third upgrader product comprises coker kerosene.

53. The startup fluid of claim 46, wherein the startup fluid further comprises a third upgrader product obtainable from a vacuum distillation process for upgrading crude oil or a downstream process thereof.

54. The startup fluid of claim 53, wherein the aromatic content of the third upgrader product is above 25%.

55. The startup fluid of claim 54, wherein the third upgrader product comprises light vacuum gas oil.

56. The startup fluid of any one of claims 50 to 52, wherein the first and third upgrader products are provided as a mixture in a proportion ranging from 80:20 to 20:80 ratio by mass% relative to the second upgrader product.

57. The startup fluid of any one of claims 53 to 55, wherein the first and third upgrader products are provided as a mixture in a proportion ranging from 80:20 to 20:80 ratio by mass% relative to the second upgrader product.

58. The startup fluid of any one of claims 42 to 57, wherein the startup fluid further comprises steam.

59. The startup fluid of any one of claims 42 to 58, wherein the startup fluid is heated at surface prior to being introduced into the bitumen-containing reservoir.

60. The startup fluid of any one of claims 42 to 59, wherein the startup fluid is introducible into the bitumen-containing reservoir via an injection well extending within the bitumen-containing reservoir.

61. The startup fluid of claim 60, wherein the startup fluid is heated while traveling along the injection well.
Date Recue/Date Received 2020-12-15

62. A startup process for mobilizing bitumen contained in a near-wellbore region of a bitumen-containing reservoir, the startup process comprising:
introducing a startup fluid into the bitumen-containing reservoir via a well extending within the bitumen-containing reservoir to mobilize the bitumen in the near-wellbore region, the startup fluid comprising a first upgrader product obtained from a vacuum distillation unit and a second upgrader product obtained from a coker unit; and recovering mobilized bitumen from the near-wellbore region to form a bitumen-depleted region;
wherein the startup fluid enables asphaltenes to remain substantially solubilized in the mobilized bitumen.

63. The startup process of claim 62, wherein the first upgrader fluid comprises coker kerosene.

64. The startup process of claim 62, wherein the first upgrader fluid comprises coker gas oil.

65. The startup process of any one of claims 62 to 64, wherein the second upgrader fluid comprises light vacuum gas oil.

66. The startup process of claim 62, wherein the startup fluid further comprises a third upgrader product.

67. The startup process of claim 66, wherein the third upgrader product is obtained from the vacuum distillation unit or the coker unit.

68. The startup process of claim 66 or 67, wherein the first upgrader fluid comprises coker kerosene.

69. The startup process of any one of claims 66 to 68, wherein the second upgrader fluid comprises light vacuum gas oil.
Date Recue/Date Received 2020-12-15

70. The startup process of any one of claims 66 to 69, wherein the third upgrader product comprises coker gas oil.

71. The startup process of any one of claims 62 to 70, wherein the well is an injection well and the recovering of the mobilized bitumen is performed via a production well located below the injection well.

72. A startup process for mobilizing bitumen contained in a near-wellbore region of a bitumen-containing reservoir, the startup process comprising:
introducing a startup fluid into the bitumen-containing reservoir via a well extending within the bitumen-containing reservoir to mobilize the bitumen in the near-wellbore region, the startup fluid comprising first and second upgrader products obtained from a vacuum distillation unit or a downstream process thereof; and recovering mobilized bitumen from the near-wellbore region to form a bitumen-depleted region;
wherein in a first stage of the startup process, the first and second upgrader products are provided in a first stage proportion that enables asphaltenes to remain substantially solubilized in the mobilized bitumen; and wherein in a second stage of the startup process following the recovering of at least a portion of the mobilized bitumen, the first and second upgrader products are provided in a second stage proportion that induces asphaltenes precipitates to form in the mobilized bitumen.

73. The startup process of claim 72, wherein the first upgrader fluid comprises coker kerosene.

74. The startup process of claim 72, wherein the first upgrader fluid comprises light vacuum gas oil.

75. The startup process of any one of claims 72 to 74, wherein the second upgrader fluid comprises coker gas oil.
Date Recue/Date Received 2020-12-15

76. The startup process of any one of claims 72 to 75, wherein the well is an injection well and the recovering of the mobilized bitumen is performed via a production well located below the injection well.

77. A startup system for mobilizing bitumen contained in a near-wellbore region of a bitumen-containing reservoir, the startup system comprising:
an injection well extending into the bitumen-containing reservoir;
a tubing string inserted into the injection well for introducing a startup fluid into the bitumen-containing reservoir to mobilize bitumen in the interwell region, the startup fluid comprising first and second upgrader products each obtained from a vacuum distillation process for upgrading crude oil or a downstream process thereof, the first upgrader product having an aromatic content above 25%, and the second upgrader product having an API gravity below 200; and a production well extending into the bitumen-containing reservoir and located below the horizontal injection section for recovering mobilized bitumen as a production fluid to form a bitumen-depleted region that enables fluid communication between the injection well and the production well.
Date Recue/Date Received 2020-12-15