CA3033615A1 - Selective gas separation of produced gas from hydrocarbon recovery from underground reservoirs - Google Patents

Abstract

Produced gas streams from in-situ viscous oil recovery processes may comprise H2S and/or CO 2, which would desirably be removed. One method comprises: a) providing a produced gas stream comprising 20-60 mol.% CO 2, 30-70 mol.% CH 4, 0-0.4 mol.% H2S and 0.1- 2 mol.% C2+ hydrocarbons from an in-situ viscous oil recovery process; b) providing a graphene-based material; and c) passing the produced gas stream through the graphene-based material for selectively adsorbing H2S and/or CO 2 from the produced gas stream with the graphene-based material, and forming a flue gas stream comprising greater than 50 mol.% combined H2S and CO 2 and a treated gas stream comprising 75-95 mol.% CH 4.

Description

SELECTIVE GAS SEPARATION OF PRODUCED GAS FROM HYDROCARBON
RECOVERY FROM UNDERGROUND RESERVOIRS
BACKGROUND
Field of Disclosure [0001] The disclosure relates generally to the field of hydrocarbon recovery from underground reservoirs. More specifically, the disclosure relates to processing of produced gas from such hydrocarbon recovery.
Description of Related Art

[0002] This section is intended to introduce various aspects of the art, which may be associated with the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present disclosure.
Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.

[0003] Modern society is greatly dependent on the use of hydrocarbon resources for fuels and chemical feedstocks. Hydrocarbons are generally found in subsurface formations that can be termed "reservoirs." Removing hydrocarbons from the reservoirs depends on numerous physical properties of the subsurface formations, such as the permeability of the rock containing the hydrocarbons, the ability of the hydrocarbons to flow through the subsurface formations, and the proportion of hydrocarbons present, among other things. Easily harvested sources of hydrocarbons are dwindling, leaving less accessible sources to satisfy future energy needs. As the costs of hydrocarbons increase, the less accessible sources become more economically attractive.

[0004] Recently, the harvesting of oil sand to remove heavy oil has become more economical. Hydrocarbon removal from oil sand may be performed by several techniques. For example, a well can be drilled to an oil sand reservoir and steam, hot air, solvents, or a combination thereof, can be injected to release the hydrocarbons. The released hydrocarbons may be collected by wells and brought to the surface.

[0005] Bitumen and heavy oil (collectively referred to herein as "viscous oil" as further defined below) reserves exist at varying depths beneath the earth's surface.
More shallow reserves are often mined followed by surface extraction. Deeper reserves are often exploited by in-situ processes.

[0006] Diluting agents have been used for both in-situ and surface extraction processes to dilute viscous oil. The term "solvent" is often used in the industry and literature in place of "diluting agent".

[0007] Diluting agents reduce the viscosity of viscous oil by dilution, while steam reduces the viscosity of viscous oil by raising the viscous oil temperature.
Reducing the viscosity of in-situ viscous oil is done to permit or facilitate its production.

[0008] Where deposits lie well below the surface, viscous oil may be extracted using in-situ ("in place") processes. Thermal recovery processes are one category of in-situ processes, where steam is used to reduce the viscosity of the viscous oil. These processes are referred to as steam-based processes. One example of an in-situ thermal process is the steam-assisted gravity drainage method (SAGD). In SAGD, directional drilling is employed to place two horizontal wells in the oil sands ¨ a lower well and an upper well positioned above it. Steam is injected into the upper well to heat the bitumen and lower its viscosity. The bitumen and condensed steam will then drain downward through the reservoir under the action of gravity and flow into the lower production well, whereby these liquids can be pumped to the surface.
At the surface of the well, the condensed steam and bitumen are separated, and the bitumen is diluted with appropriate light hydrocarbons for transport to a refinery or an upgrader. An example of SAGD is described in U.S. Patent No. 4,344,485 (Butler).

[0009] Cyclic Steam Stimulation (CSS) is a thermal recovery process in which the same well is used both for injecting a fluid and for producing oil. In CSS, cycles of steam injection, soak, and oil production are employed. Once the production rate falls to a given level, the well CA 303'3615 2019-02-13 is put through another cycle of injection, soak, and production. An example of CSS is described in U.S. Patent No. 4,280,559 (Best).

[0010] Steam Flooding (SF) is an in-situ thermal process that involves injecting steam into the formation through an injection well. Steam moves through the formation, mobilizing oil as it flows toward the production well. Mobilized oil is swept to the production well by the steam drive. An example of Steam Flooding is described in U.S. Patent No.
3,705,625 (Whitten).

[0011] Other steam-based thermal processes include Solvent-Assisted Steam-Assisted Gravity Drainage (SA-SAGD), an example of which is described in Canadian Patent No.
1,246,993 (Vogel); Liquid Addition to Steam for Enhanced Recovery (LASER), an example of which is described in U.S. Patent No. 6,708,759 (Leaute et al.); Combined Steam and Vapour Extraction Process (SAVEX), an example of which is described in U.S. Patent No. 6,662,872 (Gutek et al.), and derivatives thereof These processes employ a "diluting agent" with steam.

[0012] Solvent-dominated recovery processes (SDRPs) are another category of in-situ processes, where solvent is used to reduce the viscosity of the viscous oil.
At the present time, solvent-dominated recovery processes (SDRPs) are rarely used to produce highly viscous oil.
Vapour Extraction (VAPEX) is an example of SDRP, which is described in U.S.
Patent No.
5,899,274 (Frauenfeld). In certain described SDRPs, the solvent is heated as in, for example, heated-VAPEX (H-VAPEX), which is VAPEX using a heated diluting agent.

[0013] Cyclic solvent-dominated recovery processes (CSDRPs) have also been proposed. CSDRPs are a subset of SDRPs. A CSDRP may be, but is not necessarily, a generally non-thermal recovery method that uses a solvent (or "diluting agent") to mobilize viscous oil by cycles of injection and production. In a CSDRP, a viscosity-reducing solvent is injected through a well into a subterranean viscous-oil reservoir, causing the pressure to increase. Next, the pressure is lowered and reduced-viscosity oil is produced to the surface through the same well through which the solvent was injected. Multiple cycles of injection and production are used. In some instances, a well may not undergo cycles of injection and production, but only cycles of injection or only cycles of production. CSDRPs may be particularly attractive for thinner or lower-oil-saturation reservoirs. In such reservoirs, thermal methods utilizing heat to reduce viscous oil viscosity may be inefficient due to excessive heat loss to the overburden and/or underburden and/or reservoir with low oil content. References describing specific CSDRPs include: Canadian Patent No. 2,349,234 (Lim et al.); Lim et al., "Three-dimensional Scaled Physical Modeling of Solvent Vapour Extraction of Cold Lake Bitumen", The Journal of Canadian Petroleum Technology, 35(4), pp. 32-40, April 1996; Lim et al., "Cyclic Stimulation of Cold Lake Oil Sand with Supercritical Ethane", SPE Paper 30298, 1995; US
Patent No. 3,954,141 (Allen et al.); and Feali et al., "Feasibility Study of the Cyclic VAPEX
Process for Low Permeable Carbonate Systems", International Petroleum Technology Conference Paper 12833, 2008. The family of processes within the Lim et al.
references describes embodiments of a particular SDRP that is also a cyclic solvent-dominated recovery process (CSDRP). These processes relate to the recovery of heavy oil and bitumen from subterranean reservoirs using cyclic injection of a solvent in the liquid state which vapourizes upon production. The family of processes within the Lim et al. references may be referred to as CSPTM processes. Another example of a CSDRP is described in Canadian Patent Document No. 2,688,392 (Lebel et al., published June 9, 2011). CSP may be a non-thermal bitumen recovery process involving the injection of a liquid solvent (for example propane) followed by bitumen/solvent production in a cyclic fashion.
SUMMARY

[0014]
Produced gas streams from in-situ viscous oil recovery processes may comprise H2S and/or CO2, which would desirably be removed. One method comprises: a) providing a produced gas stream comprising 20-60 mol.% CO2, 30-70 mol.% CH4, 0-0.4 mol.%
H2S and 0.1-2 mol.% C2+ hydrocarbons from an in-situ viscous oil recovery process; b) providing a graphene-based material; and c) passing the produced gas stream through the graphene-based material for selectively adsorbing H2S and/or CO2 from the produced gas stream with the graphene-based material, and forming a flue gas stream comprising greater than 50 mol.%
combined H2S and CO2 and a treated gas stream comprising 75-95 mol.% CH4.

[0015] The foregoing has broadly outlined the features of the present disclosure so that the detailed description that follows may be better understood. Additional features will also be described herein.
BRIEF DESCRIPTION OF THE DRAWINGS

[0016] These and other features, aspects and advantages of the disclosure will become apparent from the following description, appending claims and the accompanying drawings, which are briefly described below.

[0017] Figure 1 is a flow chart of a method described herein.

[0018] It should be noted that the figure is merely an example and no limitations on the scope of the present disclosure are intended thereby. Further, the figure is generally not drawn to scale, but is drafted for purposes of convenience and clarity in illustrating various aspects of the disclosure.
DETAILED DESCRIPTION

[0019] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the features illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications, and any further applications of the principles of the disclosure as described herein are contemplated as would normally occur to one skilled in the art to which the disclosure relates.
It will be apparent to those skilled in the relevant art that some features that are not relevant to the present disclosure may not be shown in the drawing for the sake of clarity.

[0020] At the outset, for ease of reference, certain terms used in this application and their meaning as used in this context are set forth below. To the extent a term used herein is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent.
Further, the present processes are not limited by the usage of the terms shown below, as all equivalents, synonyms, new developments and terms or processes that serve the same or a similar purpose are considered to be within the scope of the present disclosure.

[0021] Throughout this disclosure, where a range is used, any number between or inclusive of the range is implied.

[0022] A "hydrocarbon" is an organic compound that primarily includes the elements of hydrogen and carbon, although nitrogen, sulfur, oxygen, metals, or any number of other elements may be present in small amounts. Hydrocarbons generally refer to components found in heavy oil or in oil sand. However, the techniques described are not limited to heavy oils but may also be used with any number of other reservoirs to improve gravity drainage of liquids.
Hydrocarbon compounds may be aliphatic or aromatic, and may be straight chained, branched, or partially or fully cyclic.
100231 "Bitumen" is a naturally occurring heavy oil material. Generally, it is the hydrocarbon component found in oil sand. Bitumen can vary in composition depending upon the degree of loss of more volatile components. It can vary from a very viscous, tar-like, semi-solid material to solid forms. The hydrocarbon types found in bitumen can include aliphatics, aromatics, resins, and asphaltenes. A typical bitumen might be composed of:
19 weight (wt.) % aliphatics (which can range from 5 wt. % - 30 wt. %, or higher);
19 wt. % asphaltenes (which can range from 5 wt. % - 30 wt. %, or higher);
30 wt. % aromatics (which can range from 15 wt. % - 50 wt. %, or higher);
32 wt. % resins (which can range from 15 wt. % - 50 wt. %, or higher); and some amount of sulfur (which can range in excess of 7 wt. %).
In addition, bitumen can contain some water and nitrogen compounds ranging from less than 0.4 wt. % to in excess of 0.7 wt. %. The percentage of the hydrocarbon found in bitumen can vary. The term "heavy oil" includes bitumen as well as lighter materials that may be found in a sand or carbonate reservoir.
[0024] "Heavy oil" includes oils which are classified by the American Petroleum Institute ("API"), as heavy oils, extra heavy oils, or bitumens. The term "heavy oil" includes bitumen. Heavy oil may have a viscosity of about 1,000 centipoise (cP) or more, 10,000 cP or more, 100,000 cP or more, or 1,000,000 cP or more. In general, a heavy oil has an API gravity between 22.3 API (density of 920 kilograms per meter cubed (kg/m3) or 0.920 grams per centimeter cubed (g/cm3)) and 10.00 API (density of 1,000 kg/m3 or 1 g/cm3).
An extra heavy oil, in general, has an API gravity of less than 10.00 API (density greater than 1,000 kg/m3 or 1 g/cm3). For example, a source of heavy oil includes oil sand or bituminous sand, which is a combination of clay, sand, water and bitumen. The recovery of heavy oils is based on the viscosity decrease of fluids with increasing temperature or solvent concentration. Once the viscosity is reduced, the mobilization of fluid by steam, hot water flooding, or gravity is possible. The reduced viscosity makes the drainage or dissolution quicker and therefore directly contributes to the recovery rate.
[0025] The term "viscous oil" as used herein means a hydrocarbon, or mixture of hydrocarbons, that occurs naturally and that has a viscosity of at least 10 cP
(centipoise) at initial reservoir conditions. Viscous oil includes oils generally defined as "heavy oil" or "bitumen". Bitumen is classified as an extra heavy oil, with an API gravity of about 100 or less, referring to its gravity as measured in degrees on the American Petroleum Institute (API) Scale.
Heavy oil has an API gravity in the range of about 22.3 to about 100. The terms viscous oil, heavy oil, and bitumen are used interchangeably herein since they may be extracted using similar processes.
100261 In-situ is a Latin phrase for "in the place" and, in the context of hydrocarbon recovery, refers generally to a subsurface hydrocarbon-bearing reservoir. For example, in-situ temperature means the temperature within the reservoir. In another usage, an in-situ oil recovery technique is one that recovers oil from a reservoir below the earth's surface.
[0027] The term "subterranean formation" refers to the material existing below the earth's surface. The subterranean formation may comprise a range of components, e.g. minerals such as quartz, siliceous materials such as sand and clays, as well as the oil and/or gas that is extracted. The subterranean formation may be a subterranean body of rock that is distinct and continuous. The terms "reservoir" and "formation" may be used interchangeably.

[0028] The terms "approximately," "about," "substantially," and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numeral ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and are considered to be within the scope of the disclosure.
[0029] The articles "the", "a" and "an" are not necessarily limited to mean only one, but rather are inclusive and open ended so as to include, optionally, multiple such elements.
[0030] Produced gas streams from in-situ viscous oil recovery processes may comprise H2S and/or CO2, which would desirably be removed.
[0031] One embodiment herein is a method comprising: a) providing a produced gas stream comprising 20-60 mol.% CO2, 30-70 mol.% CH4, 0-0.4 mol.% H2S and 0.1-2 mol.%
C2+ hydrocarbons from an in-situ viscous oil recovery process; b) providing a graphene-based material; and c) passing the produced gas stream through the graphene-based material for selectively adsorbing H2S and/or CO2 from the produced gas stream with the graphene-based material, and forming a flue gas stream comprising greater than 50 mol.% (or greater than 70 mol. %) combined H2S and CO2 and a treated gas stream comprising 75-95 mol.%
CH4.
[0032] With reference to Fig. 1, a produced gas stream (102) comprising CO2, CH4, H2S and C2+ hydrocarbons may be provided from an in-situ viscous oil recovery process. To arrive at the produced gas stream (102), a cooling step may be used, and produced water and produced viscous oil/bitumen may be removed, such cooling and removal methods being known in the art. A graphene-based material (104) may be provided, such as in the form of an adsorbent bed, for instance inside a separation vessel or pipe. The produced gas stream (102) may be passed through the graphene-based material (104) for selectively adsorbing H2S and/or CO2 from the produced gas stream (102) with the graphene-based material (104), and forming a flue gas stream (106) comprising H2S/CO2 and a treated gas stream (108) comprising CH4 The treated gas stream (108) may also comprise C2+ hydrocarbons. The process may comprise a temperature swing adsorption process using steam comprising: i) adsorption at a relatively low temperature (e.g. 30-50 C); ii) regeneration or desorption at a relatively high temperature (e.g. 90-110 C); and iii) cooling to an initial low temperature (e.g. about 30 C). In this way, the process may comprise desorbing H2S and/or CO2 from the graphene-based material using steam, and regenerating the graphene-based material for a subsequent adsorption cycle.
Carbon/sulfur compounds may be formed from desorbed H2S, for instance using low temperature processing.
[0033] The in-situ viscous oil recovery process may be any suitable in-situ viscous oil recovery process, and may be CSS, SAGD, SA-SAGD, SDRP, CSDRP, LASER, VAPEX, H-VAPEX, CSP or steam flooding, as described in the background section above.
100341 The graphene-based material may be a derivative of a graphene nanomaterial, which is an allotrope of carbon with a hexagonal crystal lattice structure and 2-dimensional.
The graphene-based material may have a lateral size of 5 nm to 20 microns and a thickness of 1 nm to 100 nm. The graphene-based material may be in a form of a sheet, a ribbon, a cap, a quantum dot, a solid powder, a film, a flake, a gel-like material, or a porous structure.
[0035] The graphene-based material may be derived from a carbon source with a degree of graphite-like crystallinity. The graphene-based material may be derived from a carbon source with 100% crystallinity, such as graphite or carbon nano-tubes.
Alternatively or additionally, the graphene-based material may be derived from a carbon source with 10-20%
crystallinity, such as coal, asphaltene, or biomass. The degree of crystallinity is the percentage of the atomic structure that has graphitic crystallinity. The graphitic structure is defined as sp2 hexagonal orientation of carbon atoms, and it can be characterized via X-ray diffraction and Raman spectroscopy techniques.

[0036] The graphene-based material may be derived from a gaseous source such as CH4, CO2, C2H6 or a solid source such as carbon nano-tubes, graphite, coke, coal, asphalt, asphaltene, woody biomass, or a combination thereof [0037] The graphene-based material may be chemically doped with adatoms, functionalized with metallic or non-metallic functional groups, and/or mixed with other active materials to increase surface adsorption properties and gas selectivity. The graphene-based material may be used as a bed with a concentration of 0.01 ¨ 1 g / cm3 of the produced gas stream. The graphene-based material may comprise graphene oxide. The graphene-based material may be mixed with a polymer to form a composite that has higher mechanical and thermal stability.
[0038] With reference to Fig. 1, the method may further comprise passing the produced gas stream (102) through a liquid (e.g. amine-based solutions) or solid-based (e.g. zinc oxide) H2S scrubber (110) to reduce an amount of H2S in the produced gas stream (102).
[0039] The method may further comprise using the treated gas stream as a fuel to generate steam and producing a flue gas, the flue gas comprising H20, CO2 and N2. The step of using the treated gas stream as the fuel to generate steam is effected using a Once Through Heat Recovery Steam Generator (OTSG). The method may further comprise sequestering the treated gas stream and/or the flue gas stream in an underground formation. The flue gas stream may be introduced to a primary separation cell (PSC) beneath a froth layer, a middlings stream, or a flotation process, within a froth treatment bitumen extraction process (details for an example of a froth treatment bitumen extraction process are provided in Canadian Patent Application No.
3,010,081). The treated gas stream or the flue gas stream may be injected into a hydrocarbon reservoir as a non-condensable gas for hydrocarbon recovery.
[0040] It should be understood that numerous changes, modifications, and alternatives to the preceding disclosure can be made without departing from the scope of the disclosure.
The preceding description, therefore, is not meant to limit the scope of the disclosure. Rather, the scope of the disclosure is to be determined only by the appended claims and their equivalents. It is also contemplated that structures and features in the present examples can be altered, rearranged, substituted, deleted, duplicated, combined, or added to each other. The scope of the claims should not be limited by particular embodiments set forth herein, but should be construed in a manner consistent with the specification as a whole.

Claims (18)

CLAIMS:

1. A method comprising:
a) providing a produced gas stream comprising 20-60 mol.% CO 2, 30-70 mol.%

CH 4, 0-0.4 mol.% H2S and 0.1-2 mol.% C2+ hydrocarbons from an in-situ viscous oil recovery process;
b) providing a graphene-based material; and c) passing the produced gas stream through the graphene-based material for selectively adsorbing H2S and/or CO 2 from the produced gas stream with the graphene-based material, and forming a flue gas stream comprising greater than 50 mol.% combined H2S and CO 2 and a treated gas stream comprising 75-95 mol.% CH 4.

2. The method of claim 1, wherein the in-situ viscous oil recovery process is CSS, SAGD, SA-SAGD, SDRP, CSDRP, LASER, VAPEX, H-VAPEX, CSP, or Steam Flooding.

3. The method of claim 1 or 2, wherein the graphene-based material is a derivative of a graphene nanomaterial.

4. The method of any one of claims 1 to 3, wherein the graphene-based material has a lateral size of 5 nm to 20 microns and a thickness of 1 nm to 100 nm.

5. The method of any one of claims 1 to 4, wherein the graphene-based material is in a form of a sheet, a ribbon, a cap, a quantum dot, a solid powder, a film, a flake, a gel-like material, or a porous structure.

6. The method of any one of claims 1 to 5, wherein the graphene-based material is derived from a carbon source with 100% crystallinity.

7. The method of any one of claims 1 to 5, wherein the graphene-based material is derived from a carbon source with 10-20% crystallinity.

8. The use of any one of claims 1 to 5, wherein the graphene-based material is derived from carbon nano-tubes, graphite, coke, coal, asphalt, asphaltene, woody biomass, or a combination thereof.

9. The method of any one of claims 1 to 8, wherein the graphene-based material is chemically doped with adatoms or functionalized with metallic or non-metallic functional groups to increase surface adsorption properties and selectivity.

10. The method of any one of claims 1 to 9, wherein the graphene-based material is used as a bed with a total mass of 0.01 ¨ 1 g per 1 cm3 of the produced gas stream.

11. The method of any one of claims 1 to 10, wherein the graphene-based material comprises graphene oxide.

12. The method of any one of claims 1 to 11, further comprising passing the produced gas stream through an H2S scrubber to reduce an amount of H2S in the produced gas stream.

13. The method of any one of claims 1 to 12, further comprising using the treated gas stream as a fuel to generate steam and producing a flue gas, the flue gas comprising H20, CO 2 and N2.

14. The method of claim 13, wherein the step of using the treated gas stream as the fuel to generate steam is effected using a Once Through Heat Recovery Steam Generator (OTSG).

15. The method of claim 13 or 14, further comprising sequestering the flue gas in an underground formation.

16. The method of claim 13 or 14, further comprising introducing the flue gas stream to a primary separation cell (PSC) beneath a froth layer, a middlings stream, or a flotation process, within a froth treatment bitumen extraction process.

17. The method of claim 13 or 14, further comprising injecting the treated gas stream or the flue gas stream into a hydrocarbon reservoir as a non-condensable gas for enhanced hydrocarbon recovery in an in-situ viscous oil recovery process.

18. The method of any one of claims 1 to 17, further comprising desorbing H2S and/or CO 2 from the graphene-based material using steam, and regenerating the graphene-based material for a subsequent adsorption cycle.