Coal bed gas reservoir water block removing agent and preparation method thereof

Abstract

The invention provides a water lock removing agent suitable for a coal bed gas reservoir and a preparation method thereof, and the water lock removing agent suitable for the coal bed gas reservoir comprises the following components in percentage by mass: A, 0.05-5% of a fluorine-containing reverse wetting agent, B, 0.05-5% of a fluorine-containing reverse wetting agent, and C, 0.05-5% of a water lock removing agent. B, 0.1 to 30 percent of a surfactant; c, 1-50% of a polar organic solvent; and D, 15 to 98.85 percent of water. The coal bed gas reservoir water block removing agent provided by the invention adopts a full-liquid-phase microemulsion system, so that on one hand, the relatively strong adsorption performance on the coal rock surface and the capability of transporting to a reservoir deep pore throat are ensured, on the other hand, the wetting reversal effect on the coal rock solid surface is ensured, and the inner surface of the pore throat is endowed with relatively strong liquid discharge performance; it is guaranteed that the gas phase can be discharged from the pore throats under the small formation driving pressure, the gas phase permeability and the gas well yield are improved, and the gas reservoir stable production period is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of coalbed methane reservoir development, and particularly relates to a water blockage removing agent for coalbed methane reservoirs and a preparation method thereof. Background Art

[0002] Coalbed methane refers to hydrocarbon gas stored in coal seams, mainly composed of methane, mainly adsorbed on the surface of coal matrix particles, partially free in coal pores or dissolved in coal seam water. It is an associated mineral resource of coal, belonging to unconventional natural gas, and is a clean, high-quality energy and chemical raw material that has emerged internationally in the past decade or two. The development and utilization of coalbed methane has multiple benefits and can generate huge economic benefits.

[0003] Compared with conventional reservoirs, coal rock reservoirs have characteristics such as strong adsorption, poor permeability, small elastic modulus, large Poisson's ratio, small average cohesive force, easy fragmentation and collapse of the physical properties of the coal rock itself, and coal rock gas reservoirs all contain water to varying degrees. Coalbed methane is mainly produced by drainage and pressure reduction. Water has an obvious control effect on the occurrence and migration of coalbed methane. Due to its special geological structure and occurrence state, coalbed methane reservoirs often need to use fracturing stimulation to obtain industrial gas flow. During the fracturing process, a large amount of aqueous fluid enters the reservoir, and only less than 40% of the liquid will flow back out of the wellbore. The liquid phase fluid will cause serious water blockage damage to the coal seam. This water blockage damage is mainly concentrated at the micro-nano pore throats, and capillary force that hinders the gas from flowing towards the wellbore will be generated at the gas-liquid interface. If the formation pressure is not enough to break through this capillary force, a water blockage effect will occur, thus blocking the gas flow channel and resulting in low gas well production and short stable production period of the gas reservoir.

[0004] At present, there is no special water blockage removing agent for coalbed methane gas reservoirs in this field, and the general water blockage removing agent for low-permeability gas reservoirs cannot be well applied to coalbed methane gas wells. The main reasons are as follows: 1. Coalbed methane gas reservoirs belong to tight gas reservoirs, and the pore throats of these gas reservoirs are basically in the micro-nano scale. While the general water blockage removing agent for low-permeability gas reservoirs uses modified nano-silica as the main component, when in use, the solid-phase nano-silica particles will inevitably cause blockage to the pore throats and cause greater damage to the reservoir. In addition, the nano-silica modification process will also increase the cost of the water blockage removing agent. 2. At present, the wetting reversal effect of the general fluorocarbon compound water blockage removing agent for low-permeability gas reservoirs on the coal rock surface is not good, and the contact angle cannot reach the strong gas-wetting wetting reversal of more than 120°. Therefore, there is an urgent need to develop a special water blockage removing agent for coalbed methane gas reservoirs in this field. Summary of the Invention

[0005] In view of the deficiencies in the background art, the present application provides a water blockage removal agent for coalbed methane reservoirs, adopting a microemulsion system in the all-liquid phase. On the one hand, this water blockage removal agent for coalbed methane reservoirs ensures strong adsorption performance on the coal rock surface, and on the other hand, it ensures the wetting reversal effect on the solid surface of the coal rock, endowing the inner surface of pores and throats with strong liquid drainage performance, ensuring that gas can be discharged from the pores and throats under a very small formation driving pressure, and improving 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 coalbed methane reservoirs, the water blockage removal agent for coalbed methane reservoirs adopts a pure liquid-phase microemulsion system, and includes the following components by mass percentage: wetting reversal agent 0.05 - 5%; surfactant 0.1 - 30%; polar organic solvent 1 - 50%; the balance is water;

[0008] The wetting reversal agent is a fluorosilicon compound, and its structural general formula is R f SO2—N(R)—C n H 2n —CHO—X—C m H 2m —Si—Z, where R f is —C p F 2p+1 , where p is an integer between 2 and 10, R is one of aryl and C1 to C6 alkyl; m and n are each independently an integer between 1 and 20; X is —[C(O)NH] q , q is an integer between 0 and 1; Z is —[O(CH2) w CH3]3, w is an integer between 0 and 3.

[0009] Further, the surfactant is any one or a mixture of two of non-ionic surfactants and anionic surfactants.

[0010] Further, the non-ionic surfactant is any one or a mixture of two or more of polyoxyethylene ethers of fluorinated fatty alcohols, polyoxyethylene ethers of perfluoroalkyl ethanol, and polyoxyethylene ethers of fluorinated alkyl sulfonamide alcohols.

[0011] Further, the anionic surfactant is any one or a mixture of two of sodium fluorinated alkyl sulfonate and sodium fluorinated alkyl benzene sulfonate.

[0012] Further, the polar organic solvent is any one or a mixture of two or more of methanol, ethanol, propanol, isopropanol, n-butanol, acetone, acetonitrile, and dimethylformamide.

[0013] Further, the water blockage removal agent for coalbed methane reservoirs is prepared by the following method: according to the mass percentages of each component, mix the components, and after stirring evenly at room temperature, the water blockage removal agent for coalbed methane reservoirs in the microemulsion system can be obtained.

[0014] Further, the water blockage removal agent for coalbed methane reservoirs comprises the following components by mass percentage: 0.1-1% of wetting reversal agent; 0.1-5% of surfactant; 5-30% of polar organic solvent; and the balance of water.

[0015] Further, the water blockage removal agent for coalbed methane reservoirs is added at a mass concentration of 0.01%-0.5% during use.

[0016] Further, the applicable temperature range of the water blockage removal agent for coalbed methane reservoirs during use is from room temperature to 150°C.

[0017] Further, the mineralization tolerance of the water blockage removal agent for coalbed methane reservoirs is 10,000-210,000 ppm.

[0018] Compared with the prior art, the water blockage removal agent for coalbed methane reservoirs provided by the present invention has the following advantages: 1. The surface tension of the water blockage removal agent for coalbed methane reservoirs provided by the present invention can be reduced to an ultra-low range of 18-22 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 removal system still has a low surface tension value at a position far from the wellbore. 2. In the present invention, a microemulsion system is adopted. After the microemulsion system enters the reservoir pore throats, the structure of the Rf, X, and Z groups in the molecule of the highly efficient wetting reversal agent of the fluorosilicon compound is defined, and chemical modification adsorption on the coal rock is carried out through chemical bond action on the inner surface of the pore throats. The fluorocarbon chains are arranged in an oriented manner facing outwards, turning 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 coal rock surface, and on the other hand, it ensures its wetting reversal effect on the solid surface of the coal rock. Under the drive of the formation pressure, with a little driving pressure on 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

[0019] Figure 1 It is a comparison diagram of the water contact angles before and after the treatment of the water blockage removal agent for coalbed methane reservoirs provided in Example 1 of the present application;

[0020] Figure 2 It is a coal core permeability recovery curve diagram of the water blockage removal agent for coalbed methane reservoirs provided in Example 1 of the present application. Detailed Embodiments

[0021] The present invention will be described in detail below with reference to the accompanying 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 removal agent for coalbed methane reservoirs. The water blockage removal agent for coalbed methane reservoirs is a microemulsion system, and the mass percentage composition of the microemulsion system is as follows:

[0024] C4F9SO2N(CH3)CH2CH2CHOC(O)NHCH2CH2CH2Si(OCH3)3 0.5%; CF3(CF2)9O(CH2CH2O) 20 H0.5%; ethylene glycol 25%; the rest is water.

[0025] After the water blockage removal agent for coalbed methane reservoirs is mixed according to the above mass ratio of each component and stirred at room temperature for 5 min, a thermodynamically stable microemulsion can be obtained.

[0026] Perform performance verification on the water blockage removal agent for coalbed methane reservoirs prepared in this example. The mass concentration of the above water blockage removal agent for coalbed methane reservoirs is 0.3%; measure the surface tension value of the above carbonate rock water blockage removal agent to be 20 mN / m; after measuring the initial contact angle of the coal core, the results are as Figure 1 shown in the left figure in the middle. The contact angle is 50.8°. After soaking in the above water blockage removal agent solution for coalbed methane reservoirs at room temperature of 20°C for 6 h and drying, measure the contact angle after treatment to be 123.4°. The results are as Figure 1 shown in the right figure in the middle.

[0027] After further testing and calculation, the initial gas permeability of the coal core is 0.017439 mD, the gas permeability after water blockage damage is 0.002737 mD, and the water blockage damage rate is 84.31%. After injecting the above water blockage removal agent for coalbed methane reservoirs and standing at room temperature of 20°C for 6 h, after positive gas flooding reaches equilibrium, the gas permeability is 0.01201 mD, and the permeability recovery rate is 68.87%, achieving a good water blockage removal effect. The results are as Figure 2 shown.

[0028] Example 2

[0029] This example provides a water blockage removal agent for coalbed methane reservoirs. The water blockage removal agent for coalbed methane reservoirs is a microemulsion system, and the mass percentage composition of the microemulsion system is as follows:

[0030] C7F 15 SO2N(CH2CH2CH3)CH2CH2CH2CHOCH2CH2CH2Si(OCH3)3 0.4%; CF3CF2CF2CF2CF2CF2CH2CH2O(CH2CH2O)8H1.2%; methanol 5%; the rest is water.

[0031] After the water block remover for coalbed methane reservoirs is mixed according to the above mass ratios of each component and stirred at room temperature for 5 minutes, a thermodynamically stable microemulsion can be obtained;

[0032] The mass concentration of the above water block remover for coalbed methane reservoirs used is 0.3%;

[0033] The surface tension value of the above water block remover for carbonate rocks is measured to be 21 mN / m;

[0034] After measuring the initial contact angle of the coal core, the core is immersed in the water block remover with the above concentration at 150 °C for 30 minutes, 1 hour, 5 hours, 12 hours, 24 hours, 7 days, and 30 days respectively, and after drying, the contact angle of the treated coal rock is measured. The contact angles are shown in the following table:

[0035] Time 30 min 1h 5h 12h 24h 7d 30d Before treatment 23.5 43.3 31.4 53.3 47.8 67.0 58.5 Contact angle after treatment / ° 129.5 124.8 132.4 135.3 131.7 132.5 133.5

[0036] It can be seen from the above table that the water block remover shows good performance stability under high temperature conditions and can modify the contact angle of coal rock from hydrophilicity to strong gas wettability.

[0037] Example 3

[0038] This example provides a water block remover for coalbed methane reservoirs. The water block remover for coalbed methane reservoirs is a microemulsion system, and the mass percentage composition of the microemulsion system is as follows: C9F 19 SO2N(CH3)CH2CH2CH2CHO C(O)NH CH2CH2Si(OCH2CH3)3 0.8%; CF3(CF2)8CH2O(CH2CH2O) 12 H1.6%; ethanol 6%; the rest is water.

[0039] After the water block remover for coalbed methane reservoirs is mixed according to the above mass ratios of each component and stirred at room temperature for 5 minutes, a thermodynamically stable microemulsion can be obtained;

[0040] The mass concentration of the above water block remover for coalbed methane reservoirs used is 0.2%;

[0041] The surface tension value of the above water block remover for carbonate rocks is measured to be 18 mN / m;

[0042] When preparing the water block remover with the above 0.2% mass concentration, the solvent used is simulated formation water with a concentration of 150000 ppm;

[0043] After measuring the initial contact angle of the coal core, the core is immersed in the water block remover with the above concentration at 80 °C for 12 hours, and after drying, the contact angle of the treated coal rock is measured. The contact angles are shown in the following table:

[0044] No. Contact angle before treatment / ° Contact angle after treatment / ° 1 43.5 128.3 2 56.6 122.5 3 28.1 132.5 4 73.6 130.5 5 35.5 128.7 6 38.4 127.8 7 45.0 131.8

[0045] As can be seen from the above table, under the condition of high salinity, the water-blocking agent can still modify the coal rock from hydrophilic to strongly gas-wetting, with contact angles all greater than 120°, showing good high-salinity resistance performance.

[0046] Example 4

[0047] This example provides a carbonate water-blocking agent, and the carbonate water-blocking agent is a nano-system. The mass percentage composition of the nano-system is as follows:

[0048] C5F 11 SO2N(CH2CH3)CH2CH2CH2CH2CHOC(O)NHCH2CH2CH2CH2Si(OCH3)3 0.8%; C9F 17 OC6H4SO3Na 1.2%; n-butanol 20%; the balance is water.

[0049] After the carbonate water-blocking agent is mixed according to the above mass ratios of each component and stirred at room temperature for 5 min, a microemulsion with a particle size of 78 nm can be obtained;

[0050] The above carbonate water-blocking agent is a thermodynamically stable system; the mass concentration of the above carbonate water-blocking agent used is 0.2%; the measured surface tension value of the above carbonate water-blocking agent is 19 mN / m; after measuring the initial contact angle of the carbonate core, the contact angle is 18°. After soaking in the above carbonate water-blocking agent solution for 24 h and drying, the treated contact angle is measured to be 116°; the initial permeability of the gas reservoir core is 0.04180 mD. After establishing water-blocking damage, the gas-measured permeability is 0.008030 mD, and the water-blocking damage rate is 80.79%. After injecting the above coalbed methane reservoir water-blocking agent and standing at a constant temperature of 40 °C for 10 h, and then gas flooding in the forward direction to equilibrium, the gas-measured permeability at this time is 0.03611 mD, and the permeability recovery rate is 86.36%, indicating that the gas-phase permeability has been greatly improved, achieving a good water-blocking removal effect.

Claims

1. A coalbed methane reservoir water-locking agent, characterized in that: The coalbed methane reservoir water lock agent adopts a pure liquid phase microemulsion system, which includes the following components by mass percentage: 0.05-5% of a wettability reversal agent; 0.1-30% of a surfactant; and 1-50% of a polar organic solvent. Water balance; The wettability reversal agent is a fluorine-silicon compound, and its general structural formula is R f SO2—N(R)—C n H 2n —CHO—X—C m H 2m —Si—Z, where R f For—C p F 2p+1 , wherein p is an integer between 2 and 10, R is one of an aryl group and a C1 to C6 alkyl group; m and n are each independently an integer between 1 and 20; X is —[C(O)NH] q , q is an integer between 0 and 1; Z is —[O(CH2) w CH3]3, w is an integer between 0 and 3.

2. The coalbed methane reservoir water-locking agent according to claim 1, characterized in that: The surfactant is any one of a nonionic surfactant and an anionic surfactant or a mixture of both.

3. The coalbed methane reservoir water-locking agent according to claim 2, characterized in that: The nonionic surfactant is any one of polyoxyethylene ether of fluorinated fatty alcohol, polyoxyethylene perfluoroalkyl ethanol, and polyoxyethylene ether of fluorinated alkyl sulfonyl alcohol amine, or a mixture of two or more thereof.

4. The coalbed methane reservoir water-locking agent according to claim 2, characterized in that: The anionic surfactant is any one of sodium fluorinated alkyl sulfonate and sodium fluorinated alkyl benzene sulfonate or a mixture of the two.

5. The coalbed methane reservoir water-locking agent according to claim 1, characterized in that: The polar organic solvent is any one of methanol, ethanol, propanol, isopropanol, n-butanol, acetone, acetonitrile and dimethylformamide, or a mixture of two or more thereof.

6. The coalbed methane reservoir water-locking agent according to claim 1, characterized in that: The coalbed methane 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 coalbed methane reservoir water-locking agent of a microemulsion system.

7. The coalbed methane reservoir water-locking agent according to claim 1, characterized in that: The coalbed methane reservoir water lock-in agent comprises the following components by mass percentage: 0.1-1% of a wettability reversal agent; 0.1-5% of a surfactant; 5-30% of a polar organic solvent; and the balance of water.

8. The coalbed methane reservoir water-locking agent according to claim 1, characterized in that: The coalbed methane reservoir water-locking agent is added at a mass concentration of 0.01% to 0.5% when used.

9. The coalbed methane reservoir water-locking agent according to claim 1, characterized in that: The applicable temperature range of the coalbed methane reservoir water-locking agent when in use is room temperature to 150°C.

10. The coalbed methane reservoir water-locking agent according to claim 1, characterized in that: The mineralization resistance of the coalbed methane reservoir water-locking agent is 10000-210000 ppm.

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