A system for separating, purifying, and recovering associated gas from oil fields and for CO2 recycling.

Abstract

This invention relates to the field of gas purification technology, and more particularly to an oilfield associated gas separation, purification, and CO2 recovery system, comprising a pretreatment system, an associated gas separation and purification system, an oxygen-enriched combustion power generation system, and a water electrolysis system. The associated gas separation and purification system includes a cryogenic separation device, a liquid CO2 purification tower, and a membrane separator. The oxygen-enriched combustion power generation system receives permeate gas from the membrane separator for oxygen-enriched combustion power generation. The water electrolysis system uses the electricity generated by the oxygen-enriched combustion power generation system to electrolyze water, and the generated O2 is supplied to the oxygen-enriched combustion power generation system. This invention combines cryogenic separation technology, oxygen-enriched combustion, and water electrolysis, which can save on the separation and purification costs of associated gas from oilfields with high CO2 content, and can reinject the separated liquid CO2 into the reservoir for reuse in carbon dioxide flooding oil recovery. Furthermore, using oxygen-enriched combustion technology on CO2-containing associated gas improves combustion efficiency and facilitates CO2 capture and utilization. At the same time, the heat energy generated by combustion is converted into electricity for use in the water electrolysis cell, and water electrolysis generates O2 required for oxygen-enriched combustion and clean energy H2 as a byproduct.

Description

Technical Field

[0001] This invention relates to the field of gas purification technology, and in particular to a system for separating, purifying, and recovering associated gas from oil fields and for CO2 recycling. Background Technology

[0002] As domestic oilfield development enters its mid-to-late stages, the difficulty of oilfield extraction is gradually increasing. To improve recovery rates, major oilfields have widely adopted CO2-enhanced tertiary oil recovery technology. However, this technology increases the CO2 content in associated gas, sometimes reaching 80%–90% of the total associated gas, posing new challenges to its separation and purification. Currently, the treatment of this associated gas involves two main methods: first, using cryogenic separation technology to separate most of the CO2; second, further purification of the separated natural gas using chemical absorption or pressure swing adsorption (PSA). However, these methods suffer from high separation and purification costs, increased equipment complexity, and environmental pollution. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: in order to overcome the problems of high separation and purification costs, increased equipment complexity and environmental pollution caused by the existing technology of first using low temperature separation technology to separate most of CO2, and then using chemical absorption or pressure swing adsorption to further purify and refine the separated natural gas, the present invention provides an oilfield associated gas separation, purification and CO2 recovery and utilization system.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: an oilfield associated gas separation, purification, and CO2 recovery and utilization system, comprising:

[0005] A pretreatment system is used to filter, dehydrate, and remove light pollutants from the gas phase from the three-phase separator;

[0006] A associated gas separation and purification system includes a cryogenic separation device, a liquid CO2 purification tower, and a membrane separator. The cryogenic separation device liquefies and separates the associated gas. The liquid CO2 purification tower purifies the liquid CO2 from the cryogenic separation device. The membrane separator purifies the separated gas from the cryogenic separation device. Part of CH4 is separated out as permeate gas, and CO2 and the remaining CH4 permeate through the membrane as permeate gas.

[0007] An oxygen-enriched combustion power generation system that receives permeate gas from a membrane separator and performs oxygen-enriched combustion to generate electricity.

[0008] The water electrolysis system uses electricity generated by the oxygen-enriched combustion power generation system to electrolyze water, and the generated O2 is supplied to the oxygen-enriched combustion power generation system.

[0009] The above technical solution uses oxygen-enriched combustion technology to improve the combustion efficiency of associated gas containing CO2 and facilitate the capture and utilization of CO2. At the same time, the heat energy generated by combustion is converted into electrical energy for use in the electrolysis cell, and water electrolysis produces O2 required for oxygen-enriched combustion and clean energy H2 as a byproduct.

[0010] Furthermore, the pretreatment system includes a filter, a condenser, and an oil-water removal tower connected in sequence.

[0011] Furthermore, the cryogenic separation device includes a compressor, a cooler, a gas-liquid separator, and a heat exchanger. The compressor inlet is connected to the outlet of the oil-water removal tower, the compressor outlet is connected to the cooler inlet, the cooler outlet is connected to the gas-liquid separator inlet, the bottom liquid phase outlet of the gas-liquid separator is connected to the liquid CO2 purification tower, the top gas phase outlet of the gas-liquid separator is connected to the cryogenic inlet of the heat exchanger, the high temperature outlet of the heat exchanger is connected to the membrane separator, the bottom liquid phase outlet of the liquid CO2 purification tower is connected to a pressure injection pump, and the top gas phase outlet of the liquid CO2 purification tower is connected to the cryogenic inlet of the heat exchanger. The pretreated tail gas from the three-phase separator enters the compressor for pressurization, and then enters the cooler to liquefy most of the tail gas. The gas-liquid mixture generated in the cooler enters the gas-liquid separator for gas-liquid separation. Liquid CO2 exits from the bottom of the gas-liquid separator and enters the liquid CO2 purification tower for purification, removing impurities. The high-purity liquid CO2 exits from the bottom of the liquid CO2 purification tower and is reinjected into the oil reservoir via a pressure pump for further oil displacement. The gas exiting from the top of the gas-liquid separator merges with the gas exiting from the top of the liquid CO2 purification tower and enters the low-temperature inlet of the heat exchanger. After being heated, it enters the membrane separator. Heating can increase the membrane separation effect. Since this device only uses single-stage membrane separation, it can remove a large amount of CO2 (50%-60%), but the hydrocarbon loss is relatively large (8%-15%). That is, this part of methane and CO2 permeates through the membrane as permeate gas, and the remaining CH4 is separated out as residual gas.

[0012] Furthermore, the oxygen-enriched combustion power generation system includes an oxygen-enriched combustion chamber, a steam turbine, and a generator connected in sequence. A steam coil is installed inside the oxygen-enriched combustion chamber and is connected to the steam turbine. A permeate gas pipe connects the permeate gas outlet of the membrane separator to the oxygen-enriched combustion chamber. The exhaust port of the oxygen-enriched combustion chamber is connected to the high-temperature inlet of the heat exchanger, and the low-temperature outlet of the heat exchanger is connected to the compressor inlet. The permeate gas from the membrane separator, i.e., CO2 and a portion of CH4, enters the oxygen-enriched combustion chamber through the permeate gas pipe for combustion. CH4 reacts with pure oxygen in the oxygen-enriched combustion chamber to generate CO2. The heat generated from the combustion heats the steam in the steam coil. The steam enters the steam turbine, driving it to rotate and thus powering the generator. The generated CO2 enters the heat exchanger from the exhaust port of the oxygen-enriched combustion chamber, exchanging heat with the gas exiting from the top of the gas-liquid separator and the top of the liquid CO2 purification tower. This increases the temperature of the gas exiting from the top of the gas-liquid separator and the top of the liquid CO2 purification tower, thereby increasing the membrane separation effect and reducing the temperature of the gas from the oxygen-enriched combustion chamber.

[0013] Furthermore, the water electrolysis system includes an electrolyzer, an oxygen supply pipe connecting the positive electrode side of the electrolyzer to the oxygen-enriched combustion chamber, a blower being installed on the oxygen supply pipe, and the negative electrode side of the electrolyzer being connected to the residual gas pipe of the membrane separator. The water electrolysis system uses the electrical energy generated by the oxygen-enriched combustion power generation system to electrolyze water, generating O2 at the positive electrode which is supplied to the oxygen-enriched combustion chamber via the blower, and generating clean energy H2 at the negative electrode of the electrolyzer which is mixed with the natural gas separated by the membrane and then co-contaminated with hydrogen for transportation.

[0014] Furthermore, a gas flow meter V1 is installed on the permeate gas pipeline, and an electromagnetic regulating valve V2 is installed on the oxygen supply pipeline. The gas flow meter V1 records the pipeline flow in real time and transmits it to the electromagnetic regulating valve V2 via a wired device. The electromagnetic regulating valve V2 receives the data and adjusts the oxygen supply to ensure complete combustion of the fuel.

[0015] The beneficial effects of the present invention are: (1) The present invention combines low temperature separation technology, oxygen-enriched combustion and water electrolysis, which can save the separation and purification cost of associated gas in oil fields with high CO2 content, and can reinject the separated liquid CO2 into the reservoir for reuse in carbon dioxide flooding oil production; (2) Using oxygen-enriched combustion technology to treat associated gas containing CO2 not only improves combustion efficiency, but also facilitates the capture and utilization of CO2. At the same time, the heat energy generated by combustion is converted into electrical energy for use in the electrolysis cell, and water electrolysis generates O2 required for oxygen-enriched combustion and clean energy H2 as a by-product. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Figure 1 This is a schematic diagram of the process of the present invention;

[0018] In the picture:

[0019] 1. Pretreatment system; 1-1 Filter; 1-2 Condenser; 1-3 Oil-water separation tower;

[0020] 2. Associated gas separation and purification system; 2-1 Compressor; 2-2 Cooler; 2-3 Gas-liquid separator; 2-4 Liquid CO2 purification tower; 2-5 Heat exchanger; 2-6 Membrane separator; 2-7 Injection pump;

[0021] 3. Oxygen-enriched combustion power generation system; 3-1 Oxygen-enriched combustion chamber; 3-2 Steam coil; 3-3 Steam turbine; 3-4 Generator;

[0022] 4. Water electrolysis system; 4-1 Electrolytic cell; 4-2 Blower. Detailed Implementation

[0023] The invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention in a schematic manner. Therefore, they only show the components relevant to the invention, and the orientations and references (e.g., up, down, left, right, etc.) are only used to aid in the description of the features in the drawings. Therefore, the following specific embodiments are not intended to be limiting, and the scope of the claimed subject matter is defined solely by the appended claims and their equivalents.

[0024] Example 1:

[0025] like Figure 1 As shown, this invention is an oilfield associated gas separation, purification, and CO2 recovery system, comprising:

[0026] Pretreatment system 1 is used to filter, dehydrate and remove light pollutants from the gas phase from the three-phase separator, including filter 1-1, condenser 1-2 and oil-water removal tower 1-3 connected in sequence;

[0027] Associated gas separation and purification system 2 includes a low-temperature separation device, a liquid CO2 purification tower 2-4 and a membrane separator 2-6;

[0028] The cryogenic separation device liquefies and separates associated gas. The cryogenic separation device includes a compressor 2-1, a cooler 2-2, a gas-liquid separator 2-3, and a heat exchanger 2-5. The inlet of the compressor 2-1 is connected to the outlet of the oil-water removal tower 1-3. The outlet of the compressor 2-1 is connected to the inlet of the cooler 2-2. The outlet of the cooler 2-2 is connected to the inlet of the gas-liquid separator 2-3. The top gas phase outlet of the gas-liquid separator 2-3 is connected to the cryogenic inlet of the heat exchanger 2-5.

[0029] The liquid CO2 purification tower 2-4 purifies the liquid CO2 from the low-temperature separation unit. The bottom liquid phase outlet of the gas-liquid separator 2-3 is connected to the liquid CO2 purification tower 2-4. The bottom liquid phase outlet of the liquid CO2 purification tower 2-4 is connected to a pressure injection pump 2-7. The top gas phase outlet of the liquid CO2 purification tower 2-4 is connected to the low-temperature inlet of the heat exchanger 2-5.

[0030] The membrane separator 2-6 purifies the separated gas from the low-temperature separation device. The high-temperature outlet of the heat exchanger 2-5 is connected to the membrane separator 2-6. Part of CH4 is separated out as permeate gas, while CO2 and the remaining CH4 permeate through the membrane as permeate gas.

[0031] The oxygen-enriched combustion power generation system 3 receives permeate gas from the membrane separator 2-6 for oxygen-enriched combustion power generation. It includes an oxygen-enriched combustion chamber 3-1, a steam turbine 3-3, and a generator 3-4 connected in sequence. A steam coil 3-2 is installed inside the oxygen-enriched combustion chamber 3-1 and is connected to the steam turbine 3-3. A permeate gas pipe is connected between the permeate gas outlet of the membrane separator 2-6 and the oxygen-enriched combustion chamber 3-1. The exhaust port of the oxygen-enriched combustion chamber 3-1 is connected to the high-temperature inlet of the heat exchanger 2-5, and the low-temperature outlet of the heat exchanger 2-5 is connected to the inlet of the compressor 2-1.

[0032] The water electrolysis system 4 uses the electricity generated by the oxygen-enriched combustion power generation system 3 to electrolyze water. The generated O2 is supplied to the oxygen-enriched combustion power generation system 3. The water electrolysis system 4 includes an electrolysis cell 4-1. An oxygen supply pipe is connected between the positive electrode side of the electrolysis cell 4-1 and the oxygen-enriched combustion chamber 3-1. A blower 4-2 is installed on the oxygen supply pipe. The negative electrode side of the electrolysis cell 4-1 is connected to the permeate gas pipe of the membrane separator 2-6. A gas flow meter V1 is installed on the permeate gas pipe. An electromagnetic regulating valve V2 is installed on the oxygen supply pipe. The gas flow meter V1 records the pipe flow in real time and transmits it to the electromagnetic regulating valve V2 through a wired device. The electromagnetic regulating valve V2 receives the data and adjusts the oxygen supply to ensure complete combustion of fuel.

[0033] Workflow:

[0034] Associated gas from the oilfield enters the pretreatment system 1 after passing through the three-phase separator. It then passes through filter 1-1, condenser 1-2, and oil-water separation tower 1-3 in sequence to remove impurities, dehydrate, and remove heavy hydrocarbons from the tail gas of the three-phase separator, preventing damage to the separation equipment or affecting the separation effect.

[0035] The pretreated tail gas from the three-phase separator enters the compressor 2-1 for pressurization, and then enters the cooler 2-2 to cool and liquefy most of the CO2 in the tail gas. The gas-liquid mixture generated in the cooler 2-2 enters the gas-liquid separator 2-3 for gas-liquid separation. The liquid CO2 exits from the bottom of the gas-liquid separator 2-3 and enters the liquid CO2 purification tower 2-4 for purification to remove impurities. The high-purity liquid CO2 exits from the bottom of the liquid CO2 purification tower 2-4 and is then reinjected into the oil reservoir through the injection pump 2-7 for further oil displacement. The gas exiting from the top of gas-liquid separator 2-3 and the top of liquid CO2 purification tower 2-4 merge and enter heat exchanger 2-5 to exchange heat with the high-temperature gas from oxygen-enriched combustion chamber 3-1. This heat exchange raises the temperature of the gas exiting from the tops of gas-liquid separator 2-3 and liquid CO2 purification tower 2-4, increasing the membrane separation efficiency. Simultaneously, it lowers the temperature of the gas from oxygen-enriched combustion chamber 3-1. The gas then merges with the tail gas from the three-phase separator, is pressurized by compressor 2-1, liquefied by cooler 2-2, and then separated for reinjection into the oil reservoir for oil displacement. The heated gas enters membrane separator 2-6, where some CH4 is separated as permeate gas, while CO2 and remaining CH4 permeate through the membrane and enter oxygen-enriched combustion chamber 3-1 for combustion. According to literature research, natural gas with a CO2 content not exceeding 60% is combustible. A gas flow meter V1 is installed on the permeate gas pipeline, and an electromagnetic regulating valve V2 is installed on the oxygen supply pipeline. The gas flow meter V1 records the pipeline flow in real time and transmits it to the electromagnetic regulating valve V2 via wired equipment. The electromagnetic regulating valve V2 receives the data and adjusts the oxygen supply to ensure complete fuel combustion. Methane and other hydrocarbons burn with pure oxygen in the oxygen-enriched combustion chamber 3-1 to produce CO2. The heat generated by combustion heats the steam in the steam coil 3-2 within the oxygen-enriched combustion chamber 3-1. The steam enters the steam turbine 3-3, driving it to rotate and subsequently powering the generator 3-4 to generate electricity. The electricity generated by the generator 3-4 is supplied to the electrolyzer 4-1 via a line. The electrolyzer 4-1 electrolyzes water, generating O2 at the positive electrode, which is then supplied to the oxygen-enriched combustion chamber 3-1 by the blower 4-2. The clean energy H2 generated at the negative electrode of the electrolyzer 4-1 is mixed with the natural gas separated by the membrane and then co-contaminated with hydrogen for transportation.

[0036] The above description, based on the preferred embodiments of the present invention, provides inspiration. Those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification but must be determined according to the claims.

Claims

1. An oilfield associated gas separation and purification and CO2 recovery system, characterized in that: include: Pretreatment system (1) is used to filter, dehydrate and remove light pollutants from the gas phase from the three-phase separator; The associated gas separation and purification system (2) includes a low-temperature separation device, a liquid CO2 purification tower (2-4), and a membrane separator (2-6). The low-temperature separation device liquefies and separates the associated gas, the liquid CO2 purification tower (2-4) purifies the liquid CO2 from the low-temperature separation device, and the membrane separator (2-6) purifies the separated gas from the low-temperature separation device. The oxygen-enriched combustion power generation system (3) receives permeate gas from the membrane separator (2-6) for oxygen-enriched combustion power generation and transfers part of the heat to the associated gas separation and purification system (2) to increase the gas temperature and enhance the membrane separation effect. The water electrolysis system (4) uses the electrical energy generated by the oxygen-enriched combustion power generation system (3) to electrolyze water, and the generated O2 is supplied to the oxygen-enriched combustion power generation system (3). The cryogenic separation device includes a compressor (2-1), a cooler (2-2), a gas-liquid separator (2-3), and a heat exchanger (2-5). The inlet of the compressor (2-1) is connected to the outlet of the oil-water removal tower (1-3). The outlet of the compressor (2-1) is connected to the inlet of the cooler (2-2). The outlet of the cooler (2-2) is connected to the inlet of the gas-liquid separator (2-3). The bottom liquid phase outlet of the gas-liquid separator (2-3) is connected to the liquid CO2 purification tower (2-4). The top gas phase outlet of the gas-liquid separator (2-3) is connected to the cryogenic inlet of the heat exchanger (2-5). The high temperature outlet of the heat exchanger (2-5) is connected to the membrane separator (2-6). The bottom liquid phase outlet of the liquid CO2 purification tower (2-4) is connected to a pressure injection pump (2-7). The top gas phase outlet of the liquid CO2 purification tower (2-4) is connected to the cryogenic inlet of the heat exchanger (2-5). The oxygen-enriched combustion power generation system (3) includes an oxygen-enriched combustion chamber (3-1), a steam turbine (3-3), and a generator (3-4) connected in sequence. A steam coil (3-2) is installed inside the oxygen-enriched combustion chamber (3-1), and the steam coil (3-2) is connected to the steam turbine (3-3). A permeate pipe is connected between the permeate outlet of the membrane separator (2-6) and the oxygen-enriched combustion chamber (3-1). The exhaust port of the oxygen-enriched combustion chamber (3-1) is connected to the high-temperature inlet of the heat exchanger (2-5), and the low-temperature outlet of the heat exchanger (2-5) is connected to the inlet of the compressor (2-1). The water electrolysis system (4) includes an electrolysis cell (4-1), an oxygen supply pipe is connected between the positive electrode side of the electrolysis cell (4-1) and the oxygen-enriched combustion chamber (3-1), a blower (4-2) is provided on the oxygen supply pipe, and the negative electrode side of the electrolysis cell (4-1) is connected to the residual gas pipe of the membrane separator (2-6).

2. The oilfield associated gas separation and purification and CO2 recycling system according to claim 1, characterized in that: The pretreatment system (1) includes a filter (1-1), a condenser (1-2), and an oil-water removal tower (1-3) connected in sequence.

3. The oilfield associated gas separation and purification and CO2 recycling system according to claim 1, characterized in that: A gas flow meter V1 is installed on the permeate gas pipeline, and an electromagnetic regulating valve V2 is installed on the oxygen delivery pipeline.

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