A method for storing energy using abandoned oil and gas reservoirs based on capturing CO2 with amine liquid

Abstract

The present invention relates to a method for storing energy by utilizing abandoned oil and gas reservoirs based on capturing CO2 with amine liquid, and belongs to the field of oil and gas development and geothermal energy utilization. The method comprises: (1) using lean amine liquid to capture and absorb CO2 in a ground capture device, and entering a liquid distribution tank to obtain rich amine liquid; (2) during low-peak electricity consumption, opening the wellhead of the injection well, and injecting the rich amine liquid into the abandoned oil and gas reservoir for energy storage; (3) during peak electricity consumption, opening the wellhead of the production well, producing CO2 and lean amine liquid stored underground, performing gas-liquid separation, and driving a gas generator and a liquid generator to generate electricity to solve the problem of power shortage; (4) the lean amine liquid and CO2 after passing through the generator enter the ground capture device respectively, and rich amine liquid is obtained again through the liquid distribution tank; (5) repeating steps (2)-(4) to realize the recycling of CO2 and lean amine liquid. The present invention uses a wide range of working fluid sources, utilizes geothermal energy to improve energy storage efficiency, and reduces carbon emissions, which is green and environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the field of oil and gas development and geothermal energy utilization, and specifically relates to a method for storing energy in abandoned oil and gas reservoirs through a self-generated gas system, and more particularly to a method for storing energy in abandoned oil and gas reservoirs based on capturing CO2 with amine liquid. Background Art

[0002] After years of development and exploitation, there are a large number of abandoned oil and gas reservoirs in China. At present, there are two main ways to utilize abandoned oil and gas reservoirs. One is to inject gas or liquid into underground abandoned oil and gas reservoirs during the time period or season when electricity is abundant, and convert the electrical energy into the internal energy of the liquid. When the electricity is insufficient, the electrical energy is released again to obtain electrical energy. For example, "A method for generating electricity by using pressurized water storage in underground space" (CN114542946A) uses liquid for compressed energy storage. The other is to use air for compressed energy storage, converting the excess electrical energy into the internal energy of the gas, such as "A thermal storage type compressed air energy storage system and control method" (CN114320828A) uses air for compressed energy storage.

[0003] These energy storage methods have limitations on geothermal utilization, meaning they can only store energy in abandoned oil and gas reservoirs, but the geothermal energy in these reservoirs cannot be developed or utilized during the storage process. "A Method for Enhancing Oil Recovery by Self-Generated CO2 Based on CO2 Capture" (CN112761599A) proposes a system for utilizing geothermal energy. If this reaction is applied to energy storage in abandoned oil and gas reservoirs, it can simultaneously store energy and extract some geothermal energy. Compared to conventional thermal storage methods, this method significantly improves energy storage efficiency. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for storing energy in abandoned oil and gas reservoirs based on capturing CO2 with amine liquid. The principle of this method is reliable. Lean amine liquid is used to capture CO2 on the ground and convert it into rich amine liquid. After being injected into the formation as a compressed energy storage working fluid, the reaction of the rich amine liquid converting to lean amine liquid absorbs heat, and a portion of the geothermal energy is recovered during the energy storage process. During extraction, CO2 and lean amine liquid are separated and respectively drive the gas / liquid generator impeller to generate electricity, thereby improving the energy storage efficiency.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions.

[0006] A method for storing energy in abandoned oil and gas reservoirs based on capturing CO2 with amine liquid includes the following steps:

[0007] (1) After CO2 is captured and absorbed by lean amine liquid in the ground CO2 capture device, it enters the liquid distribution tank to obtain rich amine liquid;

[0008] (2) during low-peak electricity consumption, opening the injection wellhead and injecting the rich amine solution obtained in step (1) into the underground abandoned oil and gas reservoir through an injection pump to store energy;

[0009] (3) During peak electricity consumption, the wellhead of the production well is opened to produce CO2 and lean amine liquid stored underground. After gas-liquid separation, the gas generator and liquid generator are driven to generate electricity to solve the problem of power shortage.

[0010] (4) The lean amine liquid and CO2 after the generator enter the ground CO2 capture device respectively, and the rich amine liquid is recovered through the liquid distribution tank;

[0011] (5) Repeat steps (2)-(4) to achieve the recycling of CO2 and lean amine liquid.

[0012] Furthermore, in step (1), the lean amine solution is a primary amine (monoethanolamine MEA), a secondary amine (diethanolamine DEA), a tertiary amine (methyldiethanolamine MDEA) or a mixture thereof.

[0013] Furthermore, in step (2), the pressure of the oil and gas reservoir increased after injection is the energy stored during injection.

[0014] Furthermore, in step (2), after being injected into the abandoned oil and gas reservoir, the rich amine liquid is heated to release the captured CO2 and is converted into a lean amine liquid, and the absorbed geothermal energy is stored in the form of released CO2 gas potential energy.

[0015] Furthermore, in step (3), CO2 and lean amine liquid respectively drive the gas generator and liquid generator to generate electricity, and the stored energy and the carried geothermal energy are converted into electrical energy.

[0016] Furthermore, the injection well and the production well may be the same well.

[0017] The CO2 capture reaction of primary amine, secondary amine and tertiary amine in step (1) is as follows:

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] This invention uses lean amine liquid to capture CO2. The resulting rich amine liquid is then heated in an abandoned oil and gas reservoir to release the captured CO2. During extraction, the gas and liquid are separated, driving the impellers of a gas generator and a liquid generator, respectively, to generate electricity. The rich amine liquid, which has released CO2 within the abandoned oil and gas reservoir, is converted into lean amine liquid. After passing through the generator, it is transferred to a CO2 capture device and then reconverted into rich amine liquid in a liquid distribution tank, achieving the recycling of CO2 and amine liquid.

[0024] Since the temperature requirement for the reaction of the rich amine liquid absorbing heat and converting into the lean amine liquid after injection into the formation is not high and the reaction can occur above 105°C, the present invention can be applied to most non-high-temperature abandoned oil and gas reservoirs, thereby improving the efficiency of such medium-temperature underground space energy storage.

[0025] Compared with existing energy storage methods, the present invention has the following advantages:

[0026] (1) The working fluids used are ethanolamine and CO2, which are widely available and easy to obtain, while reducing carbon emissions and being environmentally friendly;

[0027] (2) The geothermal energy in abandoned oil and gas reservoirs is utilized in the energy storage process, which improves the energy storage efficiency and economic benefits;

[0028] (3) Both amine solution and CO2 can be recycled, reducing costs;

[0029] (4) The reaction time is short, and injection and production can be carried out simultaneously, so injection at night and production during the day are possible, and the scheme is highly feasible. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structural principle of the present invention.

[0031] In the figure: 1 is the CO2 gas source, 2 is the ground CO2 capture device, 3 is the liquid distribution tank, 4 is the injection wellhead, 5 is the injection well, 6 is the underground abandoned oil and gas reservoir, 7 is the production well, 8 is the production wellhead, 9 is the gas generator, and 10 is the liquid generator. DETAILED DESCRIPTION

[0032] The present invention is further described below with reference to the accompanying drawings and examples to facilitate understanding by those skilled in the art. However, it should be understood that the present invention is not limited to the specific embodiments described herein. It will be apparent to those skilled in the art that any variations within the spirit and scope of the present invention as defined and established by the appended claims are intended to be protected.

[0033] See also Figure 1 The abandoned oil and gas reservoir 6 is used as the energy storage and amine liquid reaction site, the two production wells are the injection well 5 and the production well 7, and the surface facilities include the CO2 capture device 2, the liquid distribution tank 3, etc.

[0034] In the embodiment, the amine solution used is a 1% ethanolamine solution with a relative molecular mass of 61.08 g / mol and a density of 1.02 g / cm 3 The reaction enthalpy of ethanolamine absorbing carbon dioxide is 140KJ / mol (Lu Shijian, Gao Lijuan, Li Xinze, Zhao Dongya, Zhu Quanmin. Experimental study on the heat of reaction of organic amine absorbing CO2[J]. Journal of China University of Petroleum (Natural Science Edition), 2018, 42(04): 164-173). The reaction equation is as follows:

[0035]

[0036] In the embodiment, the energy consumed and stored when injecting amine solution is calculated based on the motor input power. In the embodiment, the injection pump pressure is set to 16.7 MPa, and the unit water injection power consumption is 6.94 KWh / m 3 , assuming that the energy loss during the injection and production process is 25%.

[0037] The injection energy consumption calculation formula is as follows:

[0038] W=H·V (7)

[0039] Where: H is the power consumption per unit water injection volume, KWh / m 3 ;

[0040] V is the volume of injected amine solution, m 3 .

[0041] The reaction endothermic calculation formula is as follows:

[0042] Q=n·H (8)

[0043] Where: n is the amount of ethanolamine, mol;

[0044] H is the reaction enthalpy of carbon dioxide absorption by ethanolamine, KJ / mol.

[0045] The reaction time calculation formula is as follows:

[0046]

[0047] Where: K is the reaction rate constant, min -1 ;

[0048] T is absolute temperature, K;

[0049] A is the exponential factor, min -1 ;

[0050] E a is the reaction activation energy, KJ / mol.

[0051]

[0052] Where: A0 is the initial concentration of amine solution, mol / L;

[0053] t is the reaction time, min.

[0054] The exponential factor A is 4.61×10 9 min -1 , the reaction activation energy E a The reaction time is 36.68 kJ / mol (Vaidya PD, Kenig E Y. CO2-Alkanolamine Reaction Kinetics: A Review of Recent Studies [J]. Chemical Engineering & Technology: Industrial Chemistry-Plant Equipment-Process Engineering-Biotechnology, 2007 (11): 30). From equations (9) and (10), it can be calculated that the time required for 90% of the reaction to complete in the reservoir after the injection of the amine solution is within one hour, and injection and production can be carried out simultaneously.

[0055] Example

[0056] (1) Two wells were selected as injection well A and production well B in the abandoned oil reservoir. The depth of well A ranged from 4000 to 4120 m, and that of well B from 4100 to 4160 m. The geothermal gradient was 28 °C / km (reservoir temperature was 114 °C), the underground space volume was 40,000 cubic meters, and the well had good sealing conditions.

[0057] (2) Φ339.7 mm airtight casings were run into Wells A and B, respectively. The Φ339.7 mm casing opening depth of Well A was 4100 m, and the Φ339.7 mm casing opening depth of Well B was 4120 m.

[0058] (3) Combining the previous development data of the reservoir and analyzing the results of the in-situ stress test, the formation pressure of this abandoned reservoir is 35.28 MPa and the fracture pressure is 49.98 MPa;

[0059] (4) When there is excess electricity at night, 2000 cubic meters of rich amine liquid is injected into the underground abandoned oil reservoir through injection well A by an injection pump. All the liquid can be injected within 12 hours. After injection, the formation pressure is increased to 37 MPa. The pressure of the oil reservoir is the energy stored during injection.

[0060] (5) After injection into the reservoir, the rich amine liquid utilizes the temperature of the abandoned reservoir itself to release the captured CO2 and convert it into lean amine liquid. The absorbed geothermal energy is stored in the form of the released CO2 gas potential energy. Under the condition of 114°C formation temperature, it is estimated that the time required for 90% of the reaction to be completed is within 1 hour;

[0061] (6) When power is scarce, the wellhead of the production well is opened. The CO2 and lean amine liquid stored underground are separated by gas and liquid and then passed through a gas generator and a liquid generator respectively. The stored energy is converted back into electrical energy. The pressure energy utilization rate is set to 80%, and the geothermal energy utilization rate is 80%. According to formulas (7) and (8), the total power generation is about 20.59MWh, of which 10.41MWh is released by compressed liquid and 10.18MWh is absorbed by geothermal energy.

[0062] (7) The CO2 and lean amine liquid after passing through the generator are re-injected into the capture device and liquid distribution tank to achieve the recycling of CO2 and amine liquid.

Claims

1. A method for storing energy in abandoned oil and gas reservoirs based on CO2 capture using amine liquid, comprising the following steps: (1) After CO2 is captured and absorbed by lean amine liquid in the ground CO2 capture device, it enters the liquid distribution tank to obtain rich amine liquid; (2) When electricity consumption is low, the injection wellhead is opened and the rich amine solution obtained in step (1) is injected into the underground abandoned oil and gas reservoir through an injection pump to store energy; (3) During peak electricity consumption, the wellhead of the production well is opened to produce CO2 and lean amine liquid stored underground. After gas-liquid separation, the gas generator and liquid generator are driven to generate electricity to solve the problem of power shortage. (4) The lean amine liquid and CO2 after the generator enter the ground CO2 capture device respectively, and the rich amine liquid is recovered through the liquid distribution tank; (5) Repeat steps (2) to (4) to achieve the recycling of CO2 and lean amine liquid.

2. The method for storing energy by utilizing abandoned oil and gas reservoirs based on capturing CO2 with amine solution according to claim 1, characterized in that: In the step (1), the lean amine solution is monoethanolamine, diethanolamine, methyldiethanolamine or a mixture thereof.

3. The method for storing energy by utilizing abandoned oil and gas reservoirs based on capturing CO2 with amine solution according to claim 1, characterized in that: In step (2), the pressure of the oil and gas reservoir increased after injection is the energy stored during injection.

4. The method for storing energy by utilizing abandoned oil and gas reservoirs based on capturing CO2 with amine solution according to claim 1, characterized in that: In step (2), after being injected into the abandoned oil and gas reservoir, the rich amine liquid releases the captured CO2 under heat and is converted into lean amine liquid, and the absorbed geothermal energy is stored in the form of released CO2 gas potential energy.

5. The method for storing energy by utilizing abandoned oil and gas reservoirs based on capturing CO2 with amine solution according to claim 1, characterized in that: In step (3), CO2 and lean amine liquid drive the gas generator and liquid generator respectively to generate electricity, and the stored energy and the carried geothermal energy are converted into electrical energy.

6. The method for storing energy by utilizing abandoned oil and gas reservoirs based on capturing CO2 with amine solution according to claim 1, characterized in that: The injection well and the production well are the same well.

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