Carbonate rock gas reservoir water block removing agent and preparation method thereof

Abstract

The invention provides a water lock removing agent suitable for carbonate rock gas reservoirs and a preparation method thereof.The water lock removing agent suitable for the carbonate rock gas reservoirs comprises, by mass, 1-5% of a wetting reversal agent, 1-5% of a water lock removing agent, 1-5% of a water lock removing agent, 1-5% of a water lock removing agent, 1-5% of a water lock removing agent, 1-5% of a water lock removing agent, 1-5% of a water lock removing agent and the balance water. 5%-25% of a nonionic surfactant; 10-50% of an auxiliary agent; and the balance of water. The wetting reversal agent is a fluorosilicone cationic compound. According to the carbonate rock gas reservoir water block removing agent provided by the invention, the structures of Rf and M groups in molecules are limited by the fluorosilicone cationic compound, so that on one hand, the relatively strong adsorption performance of the agent on the surface of carbonate rock is ensured, and on the other hand, the wetting reversal effect of the agent on the solid surface of the carbonate rock is ensured; and the inner surface of the pore throat is endowed with relatively strong liquid drainage performance, so that the gas phase can be discharged from the pore throat under very small formation driving pressure, the gas phase permeability and the gas well yield are improved, and the stable production period of a gas reservoir is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of carbonate gas reservoir development, and specifically relates to a water blockage removal agent for carbonate gas reservoirs and a preparation method thereof. Background Art

[0002] Carbonate gas reservoirs are a very important field for natural gas development. In general, the pore throat radius of such gas reservoirs is in the micro-nano level, and the pore channels are intricate. During the development process, any well-injected liquid, including fracturing fluid, kill fluid, acidizing and plugging removal fluid, etc., entering the reservoir will generate capillary force that hinders the outflow of gas at the gas-liquid interface, that is, water blockage damage. Inevitably, it will cause a certain degree of water blockage damage, resulting in a rapid decline in the gas well production. The fundamental idea of removing water blockage in gas reservoirs is to reduce capillary force, which is mainly achieved from two aspects: one is to reduce the surface tension of the system; the other is to change the wettability of the liquid-wet solid surface to gas-wet. A large number of studies have shown that wetting reversal can significantly increase the gas well production, and some water blockage removal methods have also been disclosed in the prior art.

[0003] Chinese Patent CN115637141 discloses a water blockage removal agent for carbonate gas reservoirs and a preparation method thereof. The water blockage removal agent is composed of the following substances in mass percentage: 10-20% of trisiloxane surfactant; 10-20% of zwitterionic fluorocarbon surfactant; 5-10% of co-surfactant; 4-6% of oil; and the rest is water. The preparation method of the water blockage removal agent is to mix the raw materials including trisiloxane surfactant at 55-80°C according to the target mass ratio, add water for constant volume dilution, and obtain an aqueous solution of nanoemulsion through ultrasonic treatment. In the above patent, trisiloxane surfactant is mainly used to effectively reduce the gas-water interfacial tension to achieve water blockage removal, without mentioning wetting reversal. At the same time, ultrasonic dispersion treatment is required during the preparation process, and the preparation process is complex; and the use concentration is high and the dosage is relatively large.

[0004] Therefore, with the development of carbonate gas reservoirs, it is necessary to develop a nano-system with a simple preparation method, low use concentration, high temperature resistance, high salinity resistance, acid resistance and long-term performance stability. This nano-system can not only penetrate deep into the fracture pore throats, but also more easily achieve the effect of wetting reversal by using a higher surface effect. Summary of the Invention

[0005] In view of the deficiencies in the background art, the present application provides a water blockage removal agent for carbonate gas reservoirs, which adopts a nano-microsphere system. The high-efficiency wetting reversal agent contained in the nano-microsphere system is a fluorosilicon-based cationic compound, and the structures of the Rf and M groups in the molecule are defined. On the one hand, it ensures strong adsorption performance on the carbonate rock surface, and on the other hand, it ensures the wetting reversal effect on the solid surface of the carbonate rock, endowing the inner surface of the pore throat with strong liquid drainage performance, ensuring that the gas phase can be discharged from the pore throat under a very small formation driving pressure, and improving the gas-phase permeability and gas well production.

[0006] The technical solution adopted to achieve the above object of the present invention is as follows:

[0007] A water blockage removal agent for carbonate gas reservoirs, which adopts a nano-microsphere system with a microsphere size < 100 nm and comprises the following components by mass percentage: 1-5% of a wetting reversal agent; 5-25% of a non-ionic surfactant; 10-50% of an auxiliary agent; and the balance being water.

[0008] The wetting reversal agent is a fluorosilicon-based cationic compound, and its structural general formula is:

[0009] Wherein R f is a C4-10 perfluoroalkyl group, p and q are integers from 1 to 6 respectively, and M is NH2 or N + (CH3)3·Br - Any one of them.

[0010] Further, the non-ionic surfactant is any one or a mixture of two of polyoxyethylene ether of fluorinated fatty alcohol and polyoxyethylene ether of fluorinated alkylsulfonyl alcohol amine.

[0011] Further, the auxiliary agent is an alcohol.

[0012] Further, the alcohol is any one or a mixture of two or more of n-butanol, ethylene glycol, isobutanol and isopropanol.

[0013] Further, the microsphere size is 30-90 nm.

[0014] Further, the water blockage removal agent for carbonate gas reservoirs is prepared by the following method: according to the mass percentages of the respective components, the components are mixed and stirred evenly at room temperature to obtain the water blockage removal agent for carbonate gas reservoirs in a nano-microsphere system.

[0015] Further, the water blockage removal agent for carbonate gas reservoirs is added at a mass concentration of 0.05%-0.3% during use.

[0016] Furthermore, the applicable temperature range of the water blockage removing agent for carbonate gas reservoirs during use is 20°C to 150°C.

[0017] Compared with the prior art, the water blockage removing agent for carbonate gas reservoirs provided by the present invention has the following advantages: 1. The surface tension of the water blockage removing agent for carbonate gas reservoirs provided by the present invention can be reduced to below 20 mN / m, and its adsorption ability on the rock surface is greatly weakened, thereby weakening its chromatographic adsorption effect in the reservoir and ensuring that the water blockage removing system still has a low surface tension value at positions far from the wellbore. 2. In the present invention, a nano-microsphere system is adopted. After the nano-microsphere system enters the reservoir pore throats, the structures of the Rf and M groups in the fluorosilicon-based cationic compound are defined, and it is adsorbed on the inner surface of the pore throats through electrostatic interaction. The fluorocarbon chains are arranged in an oriented manner facing outwards, reversing the hydrophilic surface into a gas-wetting surface and enhancing the liquid drainage ability. Therefore, on the one hand, it ensures its strong adsorption performance on the carbonate rock surface, and on the other hand, it ensures its wetting reversal effect on the solid surface of the carbonate rock. Driven by the formation pressure, with a little driving pressure for the gas phase, it can be discharged from the pore throats, thereby improving the gas phase permeability and gas well production. Description of the Drawings

[0018] Figure 1 It is the nano-microsphere particle size diagram of the water blockage removing agent for carbonate gas reservoirs provided in Example 1;

[0019] Figure 2 It is the comparison diagram of the water phase contact angles before and after the treatment with the water blockage removing agent for carbonate gas reservoirs provided in Example 1;

[0020] Figure 3 It is the carbonate core permeability recovery curve diagram of the water blockage removing agent for carbonate gas reservoirs provided in Example 1. Detailed Embodiments

[0021] The present invention will be described in detail below in conjunction with the drawings and specific embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0022] Example 1

[0023] This example provides a water blockage removing agent for carbonate rocks. The water blockage removing agent for carbonate rocks is a nano-system, and the mass percentage composition of the nano-system is as follows: C6F 13 —CH2—Si(OH)2—(CH2)3—NH2 2%; CF3(CF2)9O(CH2CH2O) 20 H 10%; ethylene glycol 25%; the rest is water.

[0024] After the water blockage removing agent for carbonate rocks is mixed according to the above mass ratios of each component and stirred at room temperature for 5 minutes, a nano-microemulsion with a particle size of 38 nm can be obtained, as Figure 1as shown

[0025] The carbonate rock water-blocking remover prepared in this embodiment. The above carbonate water-blocking remover is a thermodynamically stable system. Next, its performance is tested experimentally: When using the above carbonate rock water-blocking remover, add the carbonate rock water-blocking remover according to a mass concentration of 0.2%; After measurement, the surface tension value of the above carbonate rock water-blocking remover is 21 mN / m; After measuring the initial contact angle of the carbonate rock core, as Figure 2 shown in the upper figure above, its contact angle is 15°. After soaking in the above carbonate rock water-blocking remover solution for 6 h and drying, the contact angle after treatment is measured to be 120°, as Figure 2 shown in the lower figure below

[0026] After further experimental tests, the initial permeability of the carbonate rock gas reservoir core is 0.3117 mD. After establishing irreducible water, the gas-measured permeability is 0.1576 mD, and the damage rate after water blocking is 49.45%. After injecting the above carbonate rock water-blocking remover and standing at a constant temperature of 150 °C for 6 h, and then gas flooding in the forward direction to the irreducible water state, at this time the gas-measured permeability is 0.2507 mD, and the permeability recovery rate is 80.43%. It shows that the gas-phase permeability has been greatly improved in a short time, achieving the water-blocking removal effect. The test results are as Figure 3 shown

[0027] Example 2

[0028] This embodiment provides a carbonate rock water-blocking remover. The carbonate rock water-blocking remover is a nano system. The mass percentage composition of the nano system is as follows: C8F 17 —(CH2)2—Si(OH)2—(CH2)6—N + (CH3)3Br - 1%; C8F 13 (CH2)2SO2N(CH3)CH2CH2OH 10%; n-butanol 40%; the rest is water

[0029] After the above carbonate rock water-blocking remover is mixed according to the mass ratio of each component, stir at room temperature for 5 min to obtain a nano microemulsion with a particle size of 85 nm

[0030] The carbonate rock water-blocking remover prepared in this embodiment. The above carbonate water-blocking remover is a thermodynamically stable system. Next, its performance is tested experimentally: When using the above carbonate rock water-blocking remover, add the carbonate rock water-blocking remover according to a mass concentration of 0.1%; After measurement, the surface tension value of the above carbonate rock water-blocking remover is 19 mN / m; After measuring the initial contact angle of the carbonate rock core, its contact angle is 16°. After soaking in the above carbonate rock water-blocking remover solution for 24 h and drying, the contact angle after treatment is measured to be 131°

[0031] After further experimental tests, the initial permeability of the carbonate gas reservoir core was 0.0372 mD. After establishing irreducible water, the gas-measured permeability was 0.011 mD, and the damage rate after water locking was 70.43%. After injecting the above-mentioned carbonate water-blocking agent remover, after standing at a constant temperature of 100 °C for 6 h and then gas flooding in the forward direction to the irreducible water state, the gas-measured permeability was 0.0298 mD at this time, and the permeability recovery rate was 80.11%, indicating that the gas-phase permeability was greatly improved in a short time, achieving the effect of removing water lock.

[0032] Example 3

[0033] This example provides a carbonate water-blocking agent remover. The carbonate water-blocking agent remover is a nano-system, and the mass percentage composition of the nano-system is as follows: C 10 F 21 —CH2—Si(OH)2—CH2—NH2 5%; CF3(CF2)8CH2O(CH2CH2O) 23 H 15%; isopropanol 10%; the rest is water.

[0034] After the carbonate water-blocking agent remover is mixed according to the above mass ratios of each component, it is stirred at room temperature for 5 min to obtain a microemulsion with a particle size of 62 nm.

[0035] The carbonate water-blocking agent remover prepared in this example is a thermodynamically stable system. The following is an experimental test of its performance: When using the above-mentioned carbonate water-blocking agent remover, it is added at a mass concentration of 0.3%; the measured surface tension value of the above-mentioned carbonate water-blocking agent remover is 18 mN / m; after measuring the initial contact angle of the carbonate rock core, the contact angle is 21°. After soaking it in the above-mentioned carbonate water-blocking agent solution for 24 h and then drying it, the contact angle after treatment is measured to be 128°.

[0036] After further experimental tests, the initial permeability of the carbonate gas reservoir core was 0.0404 mD. After establishing irreducible water, the gas-measured permeability was 0.011 mD, and the damage rate after water locking was 72.77%. After injecting the above-mentioned carbonate water-blocking agent remover, after standing at a constant temperature of 60 °C for 12 h and then gas flooding in the forward direction to the irreducible water state, the gas-measured permeability was 0.0358 mD at this time, and the permeability recovery rate was 88.61%, indicating that the gas-phase permeability was greatly improved, achieving the effect of removing water lock.

[0037] Example 4

[0038] This example provides a carbonate water-blocking agent remover. The carbonate water-blocking agent remover is a nano-system, and the mass percentage composition of the nano-system is as follows: C7F 15—(CH2)2—Si(OH)2—(CH2)2—NH2 3%; CF3(CF2)8CH2O(CH2CH2O) 23 H 20%; n-butanol 18%; the balance is water.

[0039] After mixing the carbonate rock water-blocking remover according to the mass ratio of each component above, stir at room temperature for 5 min to obtain a microemulsion with a particle size of 78 nm.

[0040] The carbonate rock water-blocking remover prepared in this example is a thermodynamically stable system. The performance of the carbonate rock water-blocking remover is tested as follows: When using the above carbonate rock water-blocking remover, add the carbonate rock water-blocking remover at a mass concentration of 0.2%; after measurement, the surface tension value of the above carbonate rock water-blocking remover is 20 mN / m; after measuring the initial contact angle of the carbonate rock core, the contact angle is 18°. After soaking in the above carbonate rock water-blocking remover solution for 24 h and drying, the contact angle after treatment is measured to be 116°.

[0041] After further experimental tests, the initial permeability of the carbonate rock gas reservoir core is 0.518 mD. After establishing irreducible water, the gas-measured permeability is 0.103 mD, and the damage rate after water blockage is 80.12%. After injecting the above carbonate rock water-blocking remover and standing at a constant temperature of 40 °C for 10 h, gas flooding is carried out in the forward direction until the irreducible water state is reached. At this time, the gas-measured permeability is 0.452 mD, and the permeability recovery rate is 87.26%. It shows that the gas-phase permeability has been greatly improved, achieving the effect of removing water blockage.

[0042] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0043] In addition, it should be noted that, in the case of no contradiction, the various specific technical features described in the above specific embodiments can be combined in any appropriate manner. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0044] In addition, any combination can be made between different embodiments of the present invention, as long as it does not violate the idea of the present invention, it should also be regarded as the content disclosed by the present invention.

Claims

1. A carbonate gas reservoir water-locking agent, characterized in that: The carbonate gas reservoir water lock agent adopts a nano-microsphere system, the microsphere size is less than 100nm, and includes the following components by mass percentage: 1-5% of a wettability reversal agent; 5-25% of a nonionic surfactant; 10-50% of an auxiliary agent; and the balance of water; The wettability reversal agent is a fluorine-silicon cationic compound, and its general structural formula is: Where R f is a C4-10 perfluoroalkyl group, p and q are integers of 1 to 6, M is NH2 or N + (CH3)3·Br - Any one of .

2. The carbonate gas reservoir water-locking agent according to claim 1, characterized in that: The nonionic surfactant is any one of polyoxyethylene ether of fluorinated fatty alcohol and polyoxyethylene ether of fluorinated alkyl sulfonyl alcohol amine, or a mixture of both.

3. The carbonate gas reservoir water-locking agent according to claim 1, characterized in that: The auxiliary agent is alcohol.

4. The carbonate gas reservoir water-locking agent according to claim 3, characterized in that: The alcohol is any one of n-butanol, ethylene glycol, isobutanol and isopropanol, or a mixture of two or more thereof.

5. The carbonate gas reservoir water-locking agent according to claim 1, characterized in that: The size of the microspheres is 30 to 90 nm.

6. The carbonate gas reservoir water-locking agent according to claim 1, characterized in that: The carbonate gas reservoir water-locking agent is prepared by the following method: the components are mixed according to the mass percentage of each component, and stirred evenly at room temperature to obtain the carbonate gas reservoir water-locking agent of the nano-microsphere system.

7. The carbonate gas reservoir water-locking agent according to claim 1, characterized in that: The carbonate gas reservoir water-locking agent is added at a mass concentration of 0.05% to 0.3% when used.

8. The carbonate gas reservoir water-locking agent according to claim 1, characterized in that: The carbonate gas reservoir water-locking agent is suitable for use in a temperature range of 20°C to 150°C.

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