IN-SITU PROCESS TO PRODUCE SYNTHESIS GAS FROM UNDERGROUND HYDROCARBON RESERVOIRS

Abstract

A petroleum reservoir is treated with heat to induce gasification, water-gas shift, and/or aquathermolysis reactions to generate synthesis gas comprising hydrogen gas. The synthesis gas is produced to the surface using one or more production wells.

Claims

1. A method for treating a petroleum reservoir to recover synthesis gas therefrom, the reservoir containing petroleum and water, the method comprising the steps of: a. providing at least one production well in the reservoir, the at least one production well situated in an upper part of the reservoir; b. providing heat supply in the reservoir, the heat supply situated in a lower part of the reservoir; c. using the heat supply, heating a portion of the reservoir beneath the at least one production well to a temperature sufficient to cause at least one of gasification, water-gas shift and aquathermolysis reactions to occur within the portion of the reservoir, the at least one of the reactions involving at least one of the petroleum and the water; d. allowing the at least one of gasification, water-gas shift and aquathermolysis reactions to produce synthesis gas from the at least one of the petroleum and the water in the portion of the reservoir, the synthesis gas comprising hydrogen gas; e. providing allowing the synthesis gas to rise toward the at least one production well in the reservoir; and f. producing at least a portion of the synthesis gas to surface through the at least one production well.

2. The method of claim 1 wherein the heat supply comprises at least one heating well situated beneath the at least one production well and the heating of the portion of the reservoir comprises injecting an oxidizing agent through the at least one heating well into the reservoir to oxidize at least a portion of the petroleum and thereby heating the portion of the reservoir.

3. The method of claim 1 wherein the heat supply comprises at least one heating well situated beneath the at least one production well and the heating of the reservoir comprises positioning an electromagnetic or radio-frequency antenna in the reservoir at least one heating well and thereby generating electromagnetic or radio-frequency waves and thereby heating the portion of the reservoir.

4. The method of claim 1 wherein the heat supply comprises at least one heating well situated beneath the at least one production well and the heating of the reservoir comprises positioning a resistance-based heating system in the at least one heating well and thereby heating the portion of the reservoir.

5. The method of claim 1 wherein step d. takes place for a period of one week to twelve months.

6. The method of claim 2 wherein at least one of water, steam, combustible fuels and waste products is injected with or separately from the injecting of the oxidizing agent.

7. The method of claim 1 further comprising repeating and alternating the steps of heating the portion of the reservoir and producing the portion of the synthesis gas to the surface.

8. The method of claim 1 wherein heating of the portion of the reservoir generates heated oil from the petroleum, the heated oil accumulating in the lower part of the reservoir, the heat supply comprising at least one heating well situated beneath the at least one production well, the method further comprising the step of operating the at least one heating well as an at least one additional production well to produce a portion of the heated oil to the surface through the at least one additional production well simultaneously with production to the surface of the portion of the synthesis gas through the at least one production well.

9. A system for treating a petroleum reservoir to recover synthesis gas therefrom, the reservoir containing petroleum and water, the synthesis gas comprising hydrogen gas, the system comprising: an apparatus for heating a portion of the reservoir and thereby generating the synthesis gas from at least one of the petroleum and the water by at least one of gasification, water-gas shift and aquathermolysis reactions, the apparatus positioned in a lower part of the reservoir; and at least one well positioned in an upper part of the reservoir to produce a portion of the synthesis gas to surface.

10. The system of claim 9 wherein the apparatus for heating the portion of the reservoir comprises a heat supply selected from the group consisting of an oxidizing-agent injector, an electromagnet, a radio-frequency antenna, and a hot material injector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Features and advantages of embodiments of the present application will become apparent from the following detailed description and the appended drawings, in which:

[0039] FIG. 1A to FIG. 1C are diagrammatic representations of stages of a first exemplary embodiment of the present invention wherein petroleum reservoir is heated by oxidizing a fraction of the petroleum within the reservoir.

[0040] FIG. 2 is a diagrammatic representation of a second exemplary embodiment of the present invention wherein the petroleum reservoir is heated by using an electromagnetic/radio frequency antenna placed within the reservoir.

[0041] FIG. 3 is a diagrammatic representation of a third exemplary embodiment of the present invention comprising multiple production wells.

[0042] FIG. 4 is a diagrammatic representation of a fourth exemplary embodiment of the present invention wherein an oxidizing agent is continuously injected into the oil or gas reservoir to produce hydrogen.

[0043] FIG. 5 is a diagrammatic representation of a fifth exemplary embodiment of the present invention wherein one of the wells has a resistance-heating cartridge within the well which is used to heat the reservoir to produce synthesis gas.

[0044] FIG.6 is a diagram illustrating some of the reactions that may occur in the methods described herein which occur within the reservoir to produce synthesis gas.

[0045] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0046] Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. The following description is not intended to be exhaustive or to limit the invention to the precise form of any exemplary embodiment. Accordingly, the description and drawings are to be regarded and interpreted in an illustrative, rather than a restrictive, sense.

[0047] The present invention relates to treatment of an oil or gas reservoir for production of synthesis gas from the petroleum and water within the reservoir. The treatment includes heating the reservoir to enable gasification and water-gas shift reactions to produce synthesis gas within the reservoir and then using a production well to produce hydrogen from the reservoir.

[0048] High water content in oil and gas reservoirs is typically thought to be disadvantageous for oil or gas production. The methods described herein show that high water content is a benefit for the production of synthesis gas since water supplies hydrogen. Many of the reactions that produce synthesis gas source the hydrogen from the water in the reservoirunder the temperatures of the reactions, the formation water is converted to steam which then participates through steam reforming reactions with the hydrocarbons in the reservoir.

[0049] High H.sub.2S content in oil and gas reservoirs is typically thought to be disadvantageous for oil and gas production. The methods described herein show that hydrogen can be separated from the H.sub.2S and provide the benefit of carbonless energy and/or petrochemical feedstock.

[0050] Existing in-situ energy production processes from oil and gas reservoirs produce either oil or gas or both to the surface.

[0051] In some embodiments, the present methods take a different approach with respect to the following factors: timing of heating of the reservoir, timing of in-situ gasification and water-gas shift reactions, and production of synthesis gas from the reservoir. All of the methods here have several common steps.

[0052] First, the reservoir is heatedone exemplary method would be oxygen injection where in-situ combustion occurs in the reservoir for a period of time; another exemplary method would be to use electromagnetic or radio frequency radiation; another exemplary method would be to inject high pressure, high temperature steam or another high temperature material into the reservoir; another exemplary method would be to use electrical resistance heating.

[0053] If an oxidizing agent is injected into the reservoir, the gasification and water-gas shift reactions are permitted to continue after oxygen injection is stopped.

[0054] Synthesis gas production is enabled through production wells. Thus, the process produces energy and chemical feedstock in the form of synthesis gas from the reservoir; a relatively clean fuel and useful and valuable chemical feedstock that can be used to generate heat and power or valuable chemicals, respectively.

[0055] Throughout this specification, numerous terms and expressions are used in accordance with their ordinary meanings. Provided below are definitions of some additional terms and expressions that are used in the description that follows.

[0056] Oil is a naturally occurring, unrefined petroleum product comprising hydrocarbon components. Bitumen and heavy oil are normally distinguished from other petroleum products based on their densities and viscosities. Heavy oil is typically classified with density which is between 920 and 1000 kg/m.sup.3. Bitumen typically has density greater than 1000 kg/m.sup.3. For purposes of this specification, the terms oil, bitumen and heavy oil are used interchangeably such that each one includes the other. For example, where the term bitumen is used alone, it includes within its scope heavy oil. Non-hydrocarbon elements entrained in the oil either through suspension, sorption, emulsion, molecular bonding, or other means, which can be co-produced or mobilized by or with the oil, are included within this definition.

[0057] As used herein, petroleum reservoir refers to a subsurface formation that is primarily composed of a porous matrix which contains petroleum products, namely oil and gas. As used herein, heavy oil reservoir refers to a petroleum reservoir that is primarily composed of porous rock containing heavy oil. As used herein, oil sands reservoir refers to a petroleum reservoir that is primarily composed of porous rock containing bitumen. The water phase in a reservoir rock is the interstitial water present in the porous reservoir rock.

[0058] The natural reservoir temperature is an ambient temperature of a cold or unheated reservoir. The reservoir temperature may refer to natural reservoir temperature, or the temperature of a heated reservoir.

[0059] Cracking refers to splitting larger hydrocarbon chains into smaller-chained compounds. Hydrogenation refers to an addition of hydrogen to a hydrocarbon or refers to a substitution reaction where hydrogen is consumed.

[0060] The term in situ can refer to the environment of a subsurface oil sand reservoir. In-situ means in position or in its original place.

[0061] FIG. 1A to FIG. 1C illustrate an exemplary embodiment of the present invention for treating an oil reservoir in which oil and water within the reservoir are converted to synthesis gas.

[0062] In the embodiment illustrated in FIG. 1A to FIG. 1C, the technology is using an inverted Steam-Assisted Gravity Drainage well configuration. The exemplary embodiment in FIG. 1A to FIG. 1C includes three stages per cycle. In Stage 1 (FIG. 1A), oxygen is injected into the reservoir where a portion of the bitumen is combusted to generate the temperatures (for example, >700 C.) required for the gasification, water-gas shift, and/or aquathermolysis reactions. In Stage 2 (FIG. 1B), oxygen injection is stopped and the remaining oxygen in the reservoir is consumed. Since the reservoir in the near well region is hot, gasification, water-gas shift, and aquathermolysis reactions continue. The gas products from the reactions accumulate in the reservoir. Thereafter, Stage 3 (FIG. 1C) is initiated, when the production well is opened which then produces synthesis gas to surface. After the synthesis gas production has dropped to non-commercial rates, the process may be re-started with Stage 1. The method is not limited to horizontal wells but also can be done with vertical and deviated and multilateral wells. The method can be equally applied in a gas reservoir. The injection of an oxidizing agent can continue even during production of the synthesis gas, as illustrated in FIG. 4.

[0063] Another embodiment of the method is shown in FIG. 2. In this implementation, heat provided to the reservoir is done by using electromagnetic/radio frequency antenna. The hot reservoir undergoes gasification, water-gas shift, and aquathermolysis reactions which generate hydrogen, carbon oxides, and other gases within the reservoir. The generated synthesis gas is produced to the surface through the production well. The method is not limited to horizontal wells but also can be done with vertical and deviated and multilateral wells. The method can be equally applied in a gas reservoir.

[0064] Another embodiment is illustrated in FIG. 3, shown in the cross-well direction, illustrates electromagnetic/radio frequency heaters positioned between a plurality of hydrogen production wells. The method is not limited to horizontal wells but also can be done with vertical and deviated and multilateral wells. The method can be equally applied in a gas reservoir.

[0065] The reactions generate gas which then enables gravity drainage (due to density difference) of hot mobilized oil and steam condensate towards the base of the gasification reaction chamber. Thus, the process sustains itself by moving mobilized oil towards the reactive zone above and around the injection well. This helps with gasification reactions and maintains the high temperature (for example 700+ C.) zone near the well pair.

[0066] In another implementation, a single well can be used where oxygen is injected along one part of the well and synthesis gas production occurs along another part of the well. The well can be vertical, deviated, or horizontal.

[0067] In a further implementation, heating of the reservoir can be done by electromagnetic or radio frequency waves.

[0068] In a further implementation, heating of the reservoir can be done by using high pressure, high temperature steam.

A. Heating the Reservoir

[0069] The exemplary methods in a first step heat the reservoir to a temperature where gasification and/or water-gas shift reactions can take place between the oil and water within the reservoir.

[0070] The heat can be delivered to the reservoir through a variety of methods commonly known in the art. Commercially available methods include oxygen injection, and in some exemplary methods the combustion step has oxygen injected into the reservoir for a period of time where a fraction of the petroleum is combusted to generate heat within the reservoir to achieve temperatures on the order of 400-700 C. Other modes of heating known in the art include electromagnetic or radio frequency based heating. Other modes of heating include injecting hot materials into the reservoir.

[0071] After the heat is injected to the reservoir, then if done by combustion, oxygen injection may be stopped and the reservoir left to soak at the elevated temperature achieved by the combustion step. If heated by electromagnetic heating, then this heating can continue to keep the reservoir hot at the desired temperature.

B. Gasification, Water-Gas Shift, and Aquathermolysis Reactions Period

[0072] During the period of time at which the reservoir is at elevated temperature, gasification and water-gas shift and aquathermolysis reactions may occur with consequent generation of hydrogen, hydrogen sulphide, carbon monoxide, carbon dioxide, and steam (water vapour). As the reactions occur in the reservoir, the gas components collect within the reservoir space.

[0073] FIG. 6 illustrates some of the reactions that may occur in the reservoir. In FIG. 6, fuel for oxidation and gasification is the bitumen and coke that forms from reactions that occur during the process. Bitumen can be represented as a mixture of maltenes (saturates, aromatics, and resins) and asphaltenes (large cyclic compounds with large viscosity). During oxidation, maltenes can be converted into asphaltenes. Asphaltenes can be converted, via both low and high temperature oxidation as well as thermal cracking, into a variety of gas products including methane, hydrogen, carbon monoxide, carbon dioxide, hydrogen sulphide, and high molecular weight gases (e.g., propane, etc.) and coke. The coke can then be converted, through oxidation and gasification reactions, to products including but not limited to methane, water (vapour), carbon monoxide, carbon dioxide, and hydrogen. Also, methane can be converted, via gasification reactions, to hydrogen and carbon dioxide and carbon monoxide. Carbon monoxide and water (vapour) can be converted, via the water-gas shift reaction, to hydrogen and carbon dioxide. In general, fuel components in the system, e.g., oil, coke, methane, can be gasified to produce mixtures of carbon monoxide, carbon dioxide, hydrogen sulphide, and hydrogen.

C. Production of Synthesis Gas

[0074] After enough time has elapsed for the generation of synthesis gas, then the gas is produced from the reservoir through the production well. Since synthesis gas is removed from the reservoir, this promotes the reactions to generate more synthesis gas. During some embodiments, oil accumulated in the vicinity of the lower oxygen injection well may be produced through the same oxygen injection well, or a separate well, and sold commercially, at the same time that synthesis gas is produced through the upper injection well. This oil can be produced either continuously, or at the same time as the synthesis gas production, or oxygen ports can inject oxygen from within the same well that oil is continuously or intermittently produced from. It may be advantageous to alter the production approach depending on properties such as the synthesis gas chamber evolution, oil mobility, reservoir pressure, or other factors. If done within the same wellbore there may be additional benefits such as downhole partial oxidation and partial upgrading/hydrogenation of the oil within the reservoir or pipe, combustion-gas expansion lift effects (controlled creation of some synthesis gas within the rising oil column drives fluid to surface like a geyser and creates simultaneous high volume vacuum/siphon), sand isolation or expulsion from the well within the reservoir or to surface by related pressure and mobilization effects, and heating of the oil/emulsion as it rises to surface. Some of the hydrogen may come from water which is co-produced with the oil. This can be done by adding small amounts of the down-going oxygen to the rising fluids at pyrophoric concentration/temperature conditions.

[0075] Those skilled in the art will know that various synthesis gas components may be separated through a wide variety of well-known processes including cryogenic distillation, pressure-swing absorption/adsorption, temperature-swing absorption/adsorption, membranes, molecular sieves, centrifuges, magnetic fields, gravity/buoyancy stratification/distillation, chemical reactions, thermal break-down, resonant fields, irradiation, electrical fields, acoustical destruction, acoustical segregation, and other methods.

D. New Cycle

[0076] If the heating is done in a cyclic manner, for example, from in situ combustion using oxygen injection as illustrated in FIGS. 1A to 1C, then after the temperature of the reservoir has dropped such that the gasification, water-gas shift, and aquathermolysis reaction rates have dropped so that synthesis gas production drops below a threshold value, then a new cycle of oxygen injection and consequent in situ combustion will start leading to heating of the reservoir. Thereafter, Steps A to C are repeated. If continuous heating is done by oxidization agent injection or electromagnetic or radio frequency or resistive heating methods, then continuous synthesis gas production can occur from the reservoir.

[0077] FIG. 5 illustrates an implementation of the present methods for treating an oil reservoir in which oil and water within the reservoir are converted to synthesis gas.

[0078] Some exemplary methods heat the reservoir to a temperature where gasification and water-gas shift reactions take place involving the oil and/or water within the reservoir by continuously injecting oxygen into the reservoir (as shown in FIG. 4) to cause in situ combustion reactions to occur that heat the reservoir to the preferred temperature between 400 and 700 C. This temperature range may be transiently reached or exceeded at interstitial scale or within regions of a reservoir and does not necessitate the entire average reservoir temperature to be within this range.

[0079] While the reservoir is being heated and is at elevated temperature, gasification and water-gas shift and aquathermolysis reactions occur with consequent production of hydrogen, hydrogen sulphide, carbon monoxide, carbon dioxide, and steam (water vapour). As the reactions occur in the reservoir, the gas components collect within the reservoir space but tend to rise due to buoyancy effects in the reservoir where the mobilized oil collects around the injection well sustaining the reactions there and the gases rise upwards towards the production well above and collect in the reservoir. The synthesis gas is produced from the reservoir through the production well.

[0080] As oxygen is injected into the reservoir, a reactive zone is created within the reservoir. The reactive zone is characterized by the zone with temperature that is higher than the original reservoir temperature. In the reactive zone, the temperature rises above 450 C. and at the reaction front, the temperature can exceed 900 C. With temperatures more than 400 C., gasification reactions occur within the hot zone which generate hydrogen which is exclusively produced by the upper production well to the surface. Within the hot zone around the injection well, heated oil drains and accumulates around the injection well thus supplying more fuel for the reactions that occur around the injection well.

[0081] The synthesis gas generated from the methods taught here can be used to generate power, heat, combusted to produce steam which can be used to generate power, or steam for other in situ oil recovery processes, or as a feedstock material for producing other chemicals including fuel, plastic, methanol, urea, hydrogen, sulphur, etc.

[0082] Unless the context clearly requires otherwise, throughout the description and the claims: [0083] comprise, comprising, and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of including, but not limited to. [0084] connected, coupled, or any variant thereof, means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, or a combination thereof. [0085] herein, above, below, and words of similar import, when used to describe this specification shall refer to this specification as a whole and not to any particular portions of this specification. [0086] or, in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.5 [0087] the singular forms a, an and the also include the meaning of any appropriate plural forms

[0088] Words that indicate directions such as vertical, transverse, horizontal, upward, downward, forward, backward, inward, outward, vertical, transverse, left, right, front, back, top, bottom, below, above, under, and the like, used in this description and any accompanying claims (where present) depend on the specific orientation of the apparatus described and illustrated. The subject matter described herein may assume various alternative orientations. Accordingly, these directional terms are not strictly defined and should not be interpreted narrowly.

[0089] Where a component (e.g. a circuit, module, assembly, device, etc.) is referred to herein, unless otherwise indicated, reference to that component (including a reference to a means) should be interpreted as including as equivalents of that component any component which performs the function of the described component (i.e., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments of the invention.

[0090] Specific examples of methods and apparatus have been described herein for purposes of illustration. These are only examples. The technology provided herein can be applied to contexts other than the exemplary contexts described above. Many alterations, modifications, additions, omissions and permutations are possible within the practice of this invention. This invention includes variations on described embodiments that would be apparent to the skilled person, including variations obtained by: replacing features, elements and/or acts with equivalent features, elements and/or acts; mixing and matching of features, elements and/or acts from different embodiments; combining features, elements and/or acts from embodiments as described herein with features, elements and/or acts of other technology; and/or omitting combining features, elements and/or acts from described embodiments.

[0091] The foregoing is considered as illustrative only of the principles of the invention. The scope of the claims should not be limited by the exemplary embodiments set forth in the foregoing, but should be given the broadest interpretation consistent with the specification as a whole.