Surfactant Permeability Enhancer for Stimulating Production in Low-Permeability Reservoirs, Its Preparation Method and Application

Abstract

The present invention provides a surfactant permeability enhancer for enhancing production in low-permeability reservoirs, its preparation method and application. The surfactant permeability enhancer comprises raw materials in the following weight ratio: 15-30 parts of betaine surfactant, 25-40 parts of non-ionic surfactant, 1-5 parts of modified nano-silica, 0.5-3 parts of graphene, and 300-600 parts of water. The surfactant permeability enhancer for enhancing production in low-permeability reservoirs provided by the present invention can improve the imbibition production degree during the spontaneous imbibition production of cores, increasing the oil-phase contact angle from about 33° to about 120° before and after imbibition. When used in the volume fracturing of tight reservoirs, the average stage production increases by more than 30% compared with conventional permeability enhancers. When used in the high-depth profile control and displacement of ultra-low permeability reservoirs, the water cut in the original solution decreases significantly and the oil production increases significantly.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas development, and particularly relates to a surface-active permeability enhancer for enhancing production in low-permeability reservoirs, a preparation method thereof, and an application thereof. Background Art

[0002] Low-permeability unconventional reservoirs represented by tight oil and gas reservoirs have become an important field for oil and gas resource exploration and development in China. The physical properties of the reservoirs in this type of oil reservoir are poor, the matrix is dense, the pore throats of the reservoir are small, the pore structure is complex and the connectivity is poor, and the seepage capacity is low. Such oil reservoirs generally use large-scale volume fracturing for oil testing and production. Under the dual-medium conditions of the dense matrix-complex fractures formed after fracturing, conventional injected water is prone to channeling along the fracture system and difficult to enter the reservoir matrix, resulting in a serious decline in the production of corresponding oil wells.

[0003] In recent years, research on the imbibition mechanism has shown that the pore throats of the matrix in low-permeability reservoirs are small and the capillary force is strong. Using the imbibition effect to realize the displacement of oil and water in fractures and the matrix has become an important development mechanism for tight oil reservoirs, and it plays an important role in production enhancement measures such as fracturing, huff and puff, and water flooding. The wettability of the reservoir and the interfacial tension between oil and water are the key factors affecting the imbibition effect in low-permeability reservoirs. Since natural reservoirs generally exhibit weak hydrophilic and mixed wetting characteristics, and the interfacial tension between oil and water is generally high, the efficiency of directly using the injected medium for imbibition oil production is low, the degree of crude oil recovery in the matrix is low, and the production enhancement benefit is low.

[0004] In the prior art, surfactants are often used as imbibition agents to reduce the interfacial tension between oil and water, thereby reducing the deformation work suffered by oil droplets when passing through narrow pore throats and the resistance of oil droplets or oil films on the rock surface being stripped, and then improving the recovery rate of oil and gas resources. However, in the actual production process, surfactants have the disadvantages of low imbibition capacity and permeability enhancement capacity, and high dosage and loss during use. Summary of the Invention

[0005] The present invention provides a surface-active permeability enhancer for enhancing production in low-permeability reservoirs, a preparation method thereof, and an application thereof, so as to solve the problems of low imbibition capacity and permeability enhancement capacity and large consumption of surfactants in the prior art.

[0006] The present invention provides a surface-active permeability enhancer for enhancing production in low-permeability reservoirs. The surface-active permeability enhancer comprises raw materials in the following weight ratio: 15-30 parts of betaine-type surfactant, 25-40 parts of non-ionic surfactant, 1-5 parts of modified nano-silica, 0.5-3 parts of graphene, and 300-600 parts of water.

[0007] Optionally, the surface active penetration enhancer comprises raw materials in the following parts by weight: 20-25 parts of betaine-type surfactant, 30-35 parts of non-ionic surfactant, 2-3 parts of modified nano-silica, 1.5-2 parts of graphene, and 400-500 parts of water.

[0008] Optionally, the betaine-type surfactant is composed of cocamidopropyl betaine and perfluorohexylethylsulfonamidopropyl ethylcarboxy betaine mixed in a mass ratio of (1-1.5):1.

[0009] Optionally, the non-ionic surfactant is composed of a fluorocarbon chain non-ionic surfactant and ethylenediamine oleate mixed in a mass ratio of (2-3):1.

[0010] Optionally, the fluorocarbon chain non-ionic surfactant is a double-short fluorocarbon chain non-ionic surfactant.

[0011] Optionally, the modification process of the nano-silica includes the following steps:

[0012] S1: Mix ethanol and 3-mercaptopropyltriethoxysilane in a mass ratio of (4.5-5.5):1;

[0013] S2: Add nano-silica with a mass of 1 / 120-1 / 110 of the mixed solution to the mixed solution obtained in S1, and carry out a stirring reaction at 25 °C;

[0014] S3: Centrifuge, wash, recrystallize, and dry the reaction product obtained in S2 in sequence, and obtain an intermediate product after drying;

[0015] S4: Disperse the intermediate product obtained in S3 in dimethylformamide in a mass ratio of 1:(195-205), and carry out ultrasonic dispersion;

[0016] S5: Add an oxygen-containing salt with the same mass as the intermediate product in S3 to the product obtained after ultrasonic dispersion in S4, and use a fluorosurfactant as an initiator to carry out a reaction at 25 °C under an inert gas atmosphere;

[0017] S6: Transfer the product obtained in S5 to cyclohexane, collect the precipitate and dry it to obtain modified nano-silica.

[0018] Optionally, the solvent used for recrystallization in S3 is acetonitrile. The oxygen-containing salt used in S5 is sodium oleate, the fluorosurfactant is perfluorononenyloxybenzenesulfonate. The inert gas is one of nitrogen and helium.

[0019] Optionally, when the stirring reaction is carried out in S2, the stirring speed is 500 - 600 r / min, and the stirring time is 25 - 30 min. The ultrasonic dispersion time in S4 is 25 - 30 min, the dispersion power is 1000 - 1100 W, and the dispersion frequency is 20 - 25 KHz.

[0020] The present invention also provides a preparation method of a surfactant permeability enhancer for enhancing production in low - permeability reservoirs, comprising the following steps:

[0021] Weigh the following raw materials by weight parts: 15 - 30 parts of betaine - type surfactant, 25 - 40 parts of non - ionic surfactant, 1 - 5 parts of modified nano - silica, 0.5 - 3 parts of graphene, and 300 - 600 parts of water;

[0022] Mix the betaine - type surfactant, non - ionic surfactant and 90% of the water evenly to obtain a surfactant base liquid;

[0023] Mix the modified nano - silica with the remaining 10% of the water evenly to obtain a silica base liquid;

[0024] Under the conditions of ultrasonic dispersion and mechanical stirring, add graphene and the silica base liquid to the surfactant base liquid to obtain the surfactant permeability enhancer.

[0025] The present invention also provides an application of the surfactant permeability enhancer for enhancing production in low - permeability reservoirs. The surfactant permeability enhancer is used as a chemical agent in the process of low - permeability reservoir exploitation.

[0026] The beneficial effects of the surfactant permeability enhancer for enhancing production in low - permeability reservoirs provided by the present invention include: 1. When used for spontaneous imbibition production of cores, the room - temperature imbibition production degree (total recovery rate) can reach more than 30%, and the high - temperature imbibition production degree (total recovery rate) can reach more than 55%.

[0027] 2. The oil - phase contact angle increases from about 33° to about 120° before and after imbibition.

[0028] 3. When used for volume fracturing in tight reservoirs, the average stage production increases by more than 30% compared with conventional permeability enhancers.

[0029] 4. When used for deep profile control and displacement in ultra - low - permeability reservoirs, the water cut in the original liquid decreases significantly, and the oil production increases significantly. Detailed implementation manners

[0030] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts also belong to the scope of protection of the present invention.

[0031] The present invention provides a surfactant permeability enhancer for enhancing production in low-permeability reservoirs. The surfactant permeability enhancer comprises raw materials in the following weight ratio: 15-30 parts of betaine surfactant, 25-40 parts of non-ionic surfactant, 1-5 parts of modified nano-silica, 0.5-3 parts of graphene, and 300-600 parts of water.

[0032] The surfactant permeability enhancer includes a betaine surfactant, a non-ionic surfactant, modified nano-silica, graphene, and water. Among them, the modified nano-silica can enhance the adhesion to the exposed surface of the rock, thereby generating a strong structural separation pressure in the oil film wedge region to erode the oil film and enhance the hydrophilicity of the reservoir. The betaine surfactant and the non-ionic surfactant can adjust the oil-water interfacial tension, solubilize and disperse the shed oil film, reduce the oil droplet size, and enhance the imbibition oil drainage capacity. Graphene is selected as graphene oxide, and graphene oxide can change the rock wettability and reduce the interfacial tension.

[0033] When a single nano-silica, surfactant, or graphene oxide is used in the exploitation of low-permeability reservoirs, although they all have a certain effect of improving the recovery rate, the effect is not as good as the system composed of the three in combination. The surfactant permeability enhancer provided in the present invention combines nano-silica, surfactant, and graphene oxide, enabling the three to act synergistically, not only improving the efficiency of producing from low-permeability reservoirs but also reducing the dosage of the permeability enhancer under the same conditions.

[0034] Graphene oxide can effectively reduce the oil-water interfacial tension and change the rock wettability. When graphene oxide is combined with a surfactant, the two act synergistically, not only accelerating the imbibition rate but also increasing the final imbibition recovery degree of the core. When modified nano-silica is combined with a surfactant, the modified nano-silica can increase the hydrophilicity of the core surface through adsorption on the core surface and the "wedge separation pressure" effect. The two act synergistically to effectively improve the imbibition recovery degree. At the same time, the hydrophilic group of the surfactant can combine with the surface of the modified nano-silica particles, exposing the hydrophobic chain of the surfactant on the surface of the modified nano-silica particles, thereby making the surface of the modified nano-silica particles partially hydrophobic, which helps to reduce the interfacial tension.

[0035] Further, the surface-active permeability enhancer comprises raw materials in the following parts by weight: 20-25 parts of betaine-type surfactant, 30-35 parts of non-ionic surfactant, 2-3 parts of modified nano-silica, 1.5-2 parts of graphene, and 400-500 parts of water.

[0036] Further, the betaine-type surfactant is formed by mixing cocamidopropyl betaine and perfluorohexylethylsulfonamidopropyl ethylcarboxybetaine in a mass ratio of (1-1.5):1. Further, the non-ionic surfactant is formed by mixing a fluorocarbon chain non-ionic surfactant and ethylenediamine oleate in a mass ratio of (2-3):1. Further, the fluorocarbon chain non-ionic surfactant is a double-short fluorocarbon chain non-ionic surfactant.

[0037] The compounded surfactant is of great significance for cost reduction and efficiency improvement. The compounding of multiple surfactants can not only play a synergistic role but also achieve cost reduction and efficiency improvement, and at the same time can significantly enhance the imbibition effect and improve the oil and gas recovery rate.

[0038] Fluorocarbon surfactants have the prominent characteristics of "three highs and two aversions", namely high chemical stability, high surface activity, high heat resistance and water repellency, oil repellency. Although fluorocarbon surfactants can be stably present and used in strong acid, strong base, strong oxidation and even high-temperature systems, due to their water and oil repellency and poor affinity with water and oil, the interfacial tension is generally high, which is not conducive to direct use at the interface. In order to give full play to the characteristics of fluorocarbon surfactants and at the same time improve the performance of conventional surfactants, fluorocarbon surfactants are used in combination with conventional surfactants (hydrocarbon surfactants).

[0039] Compared with hydrocarbon surfactants, the molecules of perfluorohexylethylsulfonamidopropyl ethylcarboxybetaine are more likely to entangle with each other to form micelles. The combination of perfluorohexylethylsulfonamidopropyl ethylcarboxybetaine, double-short fluorocarbon chain non-ionic surfactant and cocamidopropyl betaine can achieve synergistic adsorption at the interface, and has a stronger ability to reduce the interfacial tension than a single surfactant system, thus better meeting the spreading conditions.

[0040] When conducting the exploitation of an oil reservoir, at the oil-water interface, ionic surfactants and amphoteric surfactants have a relatively high interfacial efficiency, while non-ionic surfactants have a relatively high interfacial density. The amphoteric surfactant perfluorohexylethylsulfonamidopropyl ethylcarboxybetaine, coconut oil amide propyl betaine and the non-ionic surfactants double-short fluorocarbon chain non-ionic surfactant and ethylenediamine oleate are formulated. The multi-component system after formulation will form a mixed adsorption layer at the oil-water interface. And due to the mutual repellency between the hydrocarbon chain and the fluorocarbon chain, the molecular arrangement on the adsorption layer at the oil-water interface will present a bilayer structure. The fluorocarbon chains are closely arranged in an oriented manner on the upper layer, and the hydrocarbon chains are arranged crosswise under the fluorocarbon chains. The hydrophilic groups of the non-ionic surfactants face the water end, and the dense hydrocarbon chain adsorption layer formed at the interface is on the oil end side, thus significantly reducing the oil-water interfacial tension. And the fluorocarbon bond is more stable than the hydrocarbon bond. Therefore, the presence of the carbon-fluorine bond improves the stability of the multi-component compounding system. In addition, there are also hydrophilic head groups connected by chemical bonds in the amphoteric fluorinated surfactant molecules. Under the action of the chemical bonds, the repulsion between the hydrophilic head groups is greatly weakened, which further promotes the molecules to be arranged more closely on the surface of the medium, thereby further reducing the surface tension of the oil-water interface. Ethylenediamine oleate also belongs to a non-ionic surfactant, has good compatibility with other surfactants, has strong wetting, penetration and dissolution capabilities, and has a long-lasting effect time.

[0041] In addition, there is almost no electrostatic repulsion between the hydrophilic groups of the non-ionic surfactant molecules in the multi-component compounding system, which makes the surfactant molecules arrange more closely at the oil-water interface, and thus makes the surface tension lower.

[0042] Preferably, the preparation process of the double-short fluorocarbon chain non-ionic surfactant is as follows:

[0043] 1) Mix 1H,1H,2H,2H-perfluorohexan-1-ol and isophorone diisocyanate evenly according to a molar ratio of 1:1, and heat up to 80 °C;

[0044] 2) Add bismuth neodecanoate to the heated reaction solution, and react at a constant temperature for 5 h.

[0045] 3) Continuously add an excessive amount of polyethylene glycol to the reaction solution, and continue to react at a constant temperature for 7 h.

[0046] 4) Filter the crude product, dialyze and purify the filtered product in deionized water for 12 h, and freeze-dry the purified product to obtain the double-short fluorocarbon chain non-ionic surfactant.

[0047] In the molecular structure of the double short fluorocarbon chain nonionic surfactant, the polyethylene glycol hydrophilic chain connects two short fluorocarbon chains together, making the arrangement of the fluorocarbon chains at the oil-water interface more compact, thereby effectively reducing the surface tension. Moreover, whether it is perfluorohexylethylsulfonamide propyl ethyl carboxybetaine or the double short fluorocarbon chain nonionic surfactant, the number of fluorinated carbon atoms is relatively small, resulting in less environmental pollution and not belonging to the organic pollutants prohibited or restricted by the Stockholm Convention.

[0048] Furthermore, the modification process of nano-silica includes the following steps:

[0049] S1: Mix ethanol and 3-mercaptopropyltriethoxysilane according to a mass ratio of (4.5 - 5.5):1;

[0050] S2: Add nano-silica with a mass of 1 / 120 - 1 / 110 of the mixed solution to the mixed solution obtained in S1, and carry out a stirring reaction at 25°C;

[0051] S3: Centrifuge, wash, recrystallize, and dry the reaction product obtained in S2 in sequence, and obtain an intermediate product after drying;

[0052] S4: Disperse the intermediate product obtained in S3 in dimethylformamide according to a mass ratio of 1:(195 - 205), and carry out ultrasonic dispersion;

[0053] S5: Add an oxygen-containing salt with the same mass as the intermediate product in S3 to the product obtained after ultrasonic dispersion in S4, and use a fluorosurfactant as an initiator to carry out a reaction at 25°C under an inert gas atmosphere;

[0054] S6: Transfer the product obtained in S5 to cyclohexane, collect the precipitate and dry it to obtain modified nano-silica.

[0055] Furthermore, the solvent used for recrystallization in S3 is acetonitrile. The oxygen-containing salt used in S5 is sodium oleate, the fluorosurfactant is sodium perfluorononenyloxybenzenesulfonate. The inert gas is one of nitrogen and helium.

[0056] Furthermore, when carrying out the stirring reaction in S2, the stirring speed is 500 - 600 r / min, and the stirring time is 25 - 30 min. The ultrasonic dispersion time in S4 is 25 - 30 min, the dispersion power is 1000 - 1100 W, and the dispersion frequency is 20 - 25 KHz.

[0057] Furthermore, the preparation method of the surfactant permeability enhancer for enhancing production in low-permeability reservoirs is as follows:

[0058] Weigh the following raw materials by weight parts: 15-30 parts of betaine-type surfactant, 25-40 parts of non-ionic surfactant, 1-5 parts of modified nano-silica, 0.5-3 parts of graphene, and 300-600 parts of water;

[0059] Mix the betaine-type surfactant, non-ionic surfactant and 90% of the water evenly to obtain a surfactant base liquid;

[0060] Mix the modified nano-silica with the remaining 10% of the water evenly to obtain a silica base liquid;

[0061] Under the conditions of ultrasonic dispersion and mechanical stirring, add graphene and silica base liquid to the surfactant base liquid to obtain a surface-active permeability enhancer.

[0062] Furthermore, the surface-active permeability enhancer for enhancing production in low-permeability reservoirs is used as a chemical agent in the process of exploiting low-permeability reservoirs.

[0063] The following further elaborates on the present invention in conjunction with specific embodiments.

[0064] Example 1

[0065] A surface-active permeability enhancer for enhancing production in low-permeability reservoirs, comprising raw materials with the following weight part ratios: 15 parts of betaine-type surfactant, 25 parts of non-ionic surfactant, 1 part of modified nano-silica, 0.5 part of graphene, and 300 parts of water. Among them, 7.5 parts of coconut oil amide propyl betaine and 7.5 parts of perfluorohexyl ethyl sulfonamide propyl ethyl carboxyl betaine are in the betaine-type surfactant, and the ratio is 1:1. Among the non-ionic surfactants, 16.7 parts of double-short fluorocarbon chain non-ionic surfactant and 8.3 parts of ethylenediamine oleate are in the ratio of 2:1.

[0066] Among them, the preparation process of the double-short fluorocarbon chain non-ionic surfactant is as follows:

[0067] 1) Mix 1H, 1H, 2H, 2H-perfluorohex-1-ol and isophorone diisocyanate evenly according to a molar ratio of 1:1, and heat up to 80 °C;

[0068] 2) Add bismuth neodecanoate to the heated reaction solution and react at a constant temperature for 5 h.

[0069] 3) Continue to add an excessive amount of polyethylene glycol to the reaction solution and continue to react at a constant temperature for 7 h.

[0070] 4) Filter the crude product, dialyze and purify the filtered product in deionized water for 12 h, and freeze-dry the purified product to obtain the double-short fluorocarbon chain non-ionic surfactant.

[0071] The modification process of the modified nano-silica includes the following steps:

[0072] S1: Mix ethanol and 3-mercaptopropyltriethoxysilane in a mass ratio of 4.5:1;

[0073] S2: Add nano-silica with a mass of 1 / 120 of the mixed solution to the mixed solution obtained in S1, and stir and react at 25 °C at a speed of 500 r / min for 25 min;

[0074] S3: Centrifuge and wash the reaction product obtained in S2 in sequence, and recrystallize it in acetonitrile and then dry it to obtain the intermediate product;

[0075] S4: Disperse the intermediate product obtained in S3 in dimethylformamide in a mass ratio of 1:195, and ultrasonically disperse it for 20 min under the conditions of 1000 w and 20 KHz;

[0076] S5: Add sodium oleate with the same mass as the intermediate product in S3 to the product obtained by ultrasonic dispersion in S4, and use sodium perfluorononenyloxybenzenesulfonate as an initiator to react at 25 °C under a nitrogen atmosphere;

[0077] S6: Transfer the product obtained in S5 to cyclohexane, collect the precipitate and dry it to obtain modified nano-silica.

[0078] A preparation method of a surface active infiltration enhancer, comprising the following steps:

[0079] 1) After weighing and preparing the raw materials, mix the betaine-type surfactant, non-ionic surfactant and 90% of water evenly to obtain the surfactant base liquid;

[0080] 2) Mix the modified nano-silica with the remaining 10% of water evenly to obtain the silica base liquid;

[0081] 3) Add graphene and the silica base liquid to the surfactant base liquid under the conditions of ultrasonic dispersion and mechanical stirring to obtain the surface active infiltration enhancer.

[0082] Use the surface active infiltration enhancer prepared above for the spontaneous imbibition experiment, and measure the degree of oil production by spontaneous imbibition of the core and the oil phase contact angle before and after spontaneous imbibition.

[0083] Example 2

[0084] It is completely the same as the raw material weight, ratio and preparation process parameters of the surface active infiltration enhancer in Example 1. Use the surface active infiltration enhancer for volume fracturing of tight reservoirs, and record its effect on volume fracturing of tight reservoirs.

[0085] For Example 3

[0086] It is exactly the same as the raw material weight, ratio, and preparation process parameters of the surfactant permeability enhancer in Example 1. The surfactant permeability enhancer is used for deep profile control in extra-low permeability reservoirs, and its profile control effect is recorded.

[0087] Example 4

[0088] A surfactant permeability enhancer for enhancing production in low-permeability reservoirs, comprising raw materials in the following weight ratio: 30 parts of betaine-type surfactant, 40 parts of non-ionic surfactant, 5 parts of modified nano-silica, 3 parts of graphene, and 600 parts of water. Among them, in the betaine-type surfactant, 18 parts of cocamidopropyl betaine and 12 parts of perfluorohexylethylsulfonamidopropyl ethylcarboxy betaine, with a ratio of 1.5:1. In the non-ionic surfactant, 30 parts of double-short fluorocarbon chain non-ionic surfactant and 10 parts of ethylenediamine oleate, with a ratio of 3:1.

[0089] Among them, the preparation process of the double-short fluorocarbon chain non-ionic surfactant is as follows:

[0090] 1) Mix 1H,1H,2H,2H-perfluorohexan-1-ol and isophorone diisocyanate evenly according to a molar ratio of 1:1, and heat up to 80 °C;

[0091] 2) Add bismuth neodecanoate to the heated reaction solution and react at a constant temperature for 5 h.

[0092] 3) Continue to add an excess of polyethylene glycol to the reaction solution and continue to react at a constant temperature for 7 h.

[0093] 4) Filter the crude product, dialyze and purify the filtered product in deionized water for 12 h, and freeze-dry the purified product to obtain the double-short fluorocarbon chain non-ionic surfactant.

[0094] The modification process of the modified nano-silica includes the following steps:

[0095] S1: Mix ethanol and 3-mercaptopropyltriethoxysilane according to a mass ratio of 5.5:1;

[0096] S2: Add nano-silica with a mass of 1 / 110 of the mixed solution to the mixed solution obtained in S1, and stir and react at 25 °C at a speed of 600 r / min for 30 min;

[0097] S3: Centrifuge and wash the reaction product obtained in S2 in sequence, and recrystallize and dry it in acetonitrile to obtain the intermediate product;

[0098] S4: Disperse the intermediate product obtained in S3 in dimethylformamide according to a mass ratio of 1:205, and ultrasonically disperse it for 30 min under the conditions of 1100 w and 25 KHz;

[0099] S5: Add sodium oleate with the same mass as the intermediate product in S3 to the product obtained after ultrasonic dispersion in S4, and use sodium perfluorononenyloxybenzenesulfonate as an initiator to carry out the reaction at 25 °C under a helium atmosphere;

[0100] S6: Transfer the product obtained in S5 to cyclohexane, collect the precipitate and dry it to obtain modified nano-silica.

[0101] A preparation method of a surface-active permeability enhancer includes the following steps:

[0102] 1) After weighing and preparing the raw materials, mix the betaine-type surfactant, non-ionic surfactant and 90% of water evenly to obtain a surfactant base liquid;

[0103] 2) Mix the modified nano-silica with the remaining 10% of water evenly to obtain a silica base liquid;

[0104] 3) Add graphene and the silica base liquid to the surfactant base liquid under the conditions of ultrasonic dispersion and mechanical stirring to obtain a surface-active permeability enhancer.

[0105] Use the above-prepared surface-active permeability enhancer for the spontaneous imbibition experiment, and measure the degree of oil production by spontaneous imbibition of the core and the oil-phase contact angle before and after spontaneous imbibition.

[0106] Example 5

[0107] It is completely the same as the raw material weight, ratio and preparation process parameters of the surface-active permeability enhancer in Example 4. Use the surface-active permeability enhancer for volume fracturing in a tight oil reservoir, and record its effect on volume fracturing in a tight oil reservoir.

[0108] Example 6

[0109] It is completely the same as the raw material weight, ratio and preparation process parameters of the surface-active permeability enhancer in Example 4. Use the surface-active permeability enhancer for deep profile control in an extra-low permeability oil reservoir, and record its profile control effect.

[0110] Example 7

[0111] A surface-active permeability enhancer for enhancing production in a low-permeability oil reservoir includes raw materials with the following weight ratio: 23 parts of betaine-type surfactant, 35 parts of non-ionic surfactant, 2.5 parts of modified nano-silica, 1.8 parts of graphene, and 450 parts of water. Among them, in the betaine-type surfactant, there are 13 parts of cocamidopropyl betaine and 10 parts of perfluorohexylethylsulfonamidopropyl ethylcarboxy betaine, and the ratio is 1.3:1. In the non-ionic surfactant, there are 25 parts of double-short fluorocarbon chain non-ionic surfactant and 10 parts of ethylenediamine oleate, and the ratio is 2.5:1.

[0112] Among them, the preparation process of the double-short fluorocarbon chain nonionic surfactant is as follows:

[0113] 1) Mix 1H,1H,2H,2H-perfluorohexan-1-ol and isophorone diisocyanate evenly according to a molar ratio of 1:1, and heat up to 80 °C.

[0114] 2) Add bismuth neodecanoate to the heated reaction solution and react at a constant temperature for 5 h.

[0115] 3) Continue to add an excessive amount of polyethylene glycol to the reaction solution and continue to react at a constant temperature for 7 h.

[0116] 4) Filter the crude product, dialyze and purify the filtered product in deionized water for 12 h, and freeze-dry the purified product to obtain the double-short fluorocarbon chain nonionic surfactant.

[0117] The modification process of the modified nano-silica includes the following steps:

[0118] S1: Mix ethanol and 3-mercaptopropyltriethoxysilane according to a mass ratio of 5:1.

[0119] S2: Add nano-silica with a mass of 1 / 115 of the mixed solution to the mixed solution obtained in S1, and stir and react at a speed of 550 r / min at 25 °C for 27 min.

[0120] S3: Centrifuge and wash the reaction product obtained in S2 in sequence, and recrystallize and dry it in acetonitrile to obtain an intermediate product.

[0121] S4: Disperse the intermediate product obtained in S3 in dimethylformamide according to a mass ratio of 1:200, and ultrasonically disperse it for 27 min under the conditions of 1050 w and 23 KHz.

[0122] S5: Add sodium oleate with the same mass as the intermediate product in S3 to the product obtained by ultrasonic dispersion in S4, and use perfluorononenyloxybenzenesulfonate as an initiator to react at 25 °C under a nitrogen atmosphere.

[0123] S6: Transfer the product obtained in S5 to cyclohexane, collect the precipitate and dry it to obtain the modified nano-silica.

[0124] A preparation method of a surface active permeation enhancer includes the following steps:

[0125] 1) After weighing and preparing the raw materials, mix the betaine-type surfactant, nonionic surfactant and 90% water evenly to obtain a surfactant base liquid.

[0126] 2) Mix the modified nano-silica with the remaining 10% water evenly to obtain a silica base liquid.

[0127] 3) Under the conditions of ultrasonic dispersion and mechanical stirring, graphene and silica-based liquid are added to the surfactant-based liquid to obtain a surfactant-based permeability enhancer.

[0128] The above-prepared surfactant-based permeability enhancer is used in the spontaneous imbibition experiment, and the degree of oil production by spontaneous imbibition of the core and the oil-phase contact angle before and after spontaneous imbibition are measured.

[0129] Example 8

[0130] It is completely the same as the raw material weight, ratio and preparation process parameters of the surfactant-based permeability enhancer in Example 7. The surfactant-based permeability enhancer is used for volume fracturing of tight oil reservoirs, and its effect on volume fracturing of tight oil reservoirs is recorded.

[0131] Example 9

[0132] It is completely the same as the raw material weight, ratio and preparation process parameters of the surfactant-based permeability enhancer in Example 7. The surfactant-based permeability enhancer is used for deep profile control of ultra-low permeability oil reservoirs, and its profile control effect is recorded.

[0133] Example 10

[0134] A surfactant-based permeability enhancer for enhancing production in low-permeability oil reservoirs, comprising raw materials with the following weight ratio: 15 parts of betaine-type surfactant, 40 parts of non-ionic surfactant, 5 parts of modified nano-silica, 0.5 part of graphene, and 600 parts of water. Among them, in the betaine-type surfactant, 9 parts of cocamidopropyl betaine and 6 parts of perfluorohexylethylsulfonamidopropyl ethylcarboxy betaine, with a ratio of 1.5:1. In the non-ionic surfactant, 26.7 parts of double-short fluorocarbon chain non-ionic surfactant and 13.3 parts of ethylenediamine oleate, with a ratio of 2:1.

[0135] Among them, the preparation process of the double-short fluorocarbon chain non-ionic surfactant is as follows:

[0136] 1) Mix 1H, 1H, 2H, 2H-perfluorohexan-1-ol and isophorone diisocyanate evenly according to a molar ratio of 1:1, and heat up to 80 °C;

[0137] 2) Add bismuth neodecanoate to the heated reaction solution and react at a constant temperature for 5 h.

[0138] 3) Continue to add an excessive amount of polyethylene glycol to the reaction solution and continue to react at a constant temperature for 7 h.

[0139] 4) Filter the crude product, dialyze and purify the filtered product in deionized water for 12 h, and freeze-dry the purified product to obtain the double-short fluorocarbon chain non-ionic surfactant.

[0140] The modification process of the modified nano-silica includes the following steps:

[0141] S1: Mix ethanol and 3-mercaptopropyltriethoxysilane in a mass ratio of 4.5:1;

[0142] S2: Add nano-silica with a mass of 1 / 115 of the mixed solution to the mixed solution obtained in S1, and stir and react at 25 °C at a speed of 500 r / min for 30 min;

[0143] S3: Centrifuge and wash the reaction product obtained in S2 in sequence, and recrystallize and dry it in acetonitrile to obtain the intermediate product;

[0144] S4: Disperse the intermediate product obtained in S3 in dimethylformamide in a mass ratio of 1:195, and ultrasonically disperse it for 25 min under the conditions of 1100 w and 20 KHz;

[0145] S5: Add sodium oleate with the same mass as the intermediate product in S3 to the product obtained by ultrasonic dispersion in S4, and use sodium perfluorononenyloxybenzenesulfonate as an initiator to react at 25 °C under a helium atmosphere;

[0146] S6: Transfer the product obtained in S5 to cyclohexane, collect the precipitate and dry it to obtain modified nano-silica.

[0147] A preparation method of a surface-active permeability enhancer, comprising the following steps:

[0148] 1) After weighing and preparing the raw materials, mix the betaine-type surfactant, non-ionic surfactant and 90% water evenly to obtain the surfactant base liquid;

[0149] 2) Mix the modified nano-silica and the remaining 10% water evenly to obtain the silica base liquid;

[0150] 3) Add graphene and the silica base liquid to the surfactant base liquid under the conditions of ultrasonic dispersion and mechanical stirring to obtain the surface-active permeability enhancer.

[0151] Use the above-prepared surface-active permeability enhancer for the spontaneous imbibition experiment, and measure the degree of oil production by spontaneous imbibition of the core and the oil-phase contact angle before and after spontaneous imbibition.

[0152] Example 11

[0153] It is completely the same as the raw material weight, ratio and preparation process parameters of the surface-active permeability enhancer in Example 10. Use the surface-active permeability enhancer for volume fracturing of tight reservoirs, and record its effect on volume fracturing of tight reservoirs.

[0154] Example 12

[0155] The weight, ratio, and preparation process parameters of the surfactant permeability enhancer raw material are exactly the same as those in Example 10. The surfactant permeability enhancer is used for deep profile control in extra-low permeability reservoirs, and its profile control effect is recorded.

[0156] The experimental results of the spontaneous imbibition recovery degree and the oil-phase contact angle before and after spontaneous imbibition of the cores in Example 1, Example 4, Example 7, and Example 10 are shown in Table 1:

[0157] Table 1

[0158] Example 1 Example 4 Example 7 Example 10 Small pore recovery rate (25°C) 41％ 53％ 45％ 46％ Small pore recovery rate (65°C) 50％ 59％ 53％ 54％ Large pore recovery rate (25°C) 19％ 30％ 24％ 26％ Large pore recovery rate (65°C) 70％ 79％ 74％ 75％ Total recovery rate (25°C) 30％ 43％ 35％ 37％ Total recovery rate (65°C) 55％ 67％ 62％ 60％ Oil phase contact angle before imbibition 31.2° 33.2° 37.2° 34.3° Oil phase contact angle after imbibition 118.9° 131.5° 125.2° 121.7°

[0159] From Example 1, Example 4, Example 7, Example 10, and the data in Table 1, it can be seen that when the surfactant permeability enhancer for enhancing production in low-permeability reservoirs provided by the present invention is used for spontaneous imbibition recovery of cores, the normal-temperature imbibition recovery degree (total recovery rate) can reach more than 30%, and the high-temperature imbibition recovery degree (total recovery rate) can reach more than 55%. The oil-phase contact angle before and after imbibition increases from about 33° to about 120°.

[0160] The experimental results of Example 2, Example 5, Example 8, and Example 11 for volume fracturing in tight reservoirs are shown in Table 2:

[0161] Table 2

[0162]

[0163]

[0164] From Example 2, Example 5, Example 8, Example 11, and the data in Table 1, it can be seen that when the surfactant permeability enhancer for enhancing production in low-permeability reservoirs provided by the present invention is used for volume fracturing in tight reservoirs, the production of multiple test wells after 6 months of production is all above 2700t. Compared with the average stage production of the comparison wells without using the surfactant permeability enhancer, it increases by more than 30% (the total production of the 3 blank test wells in the 6-month stage during the experiment is 2154t, 2191t, and 1591t respectively).

[0165] Example 3, Example 6, Example 9, and Example 12 are used for deep profile control in extra-low permeability reservoirs, and the recorded profile control effect is shown in Table 3:

[0166] Table 3

[0167] Example 3 Example 6 Example 9 Example 12 <![CDATA[Nissan liquid (m 3 )]]> 15.7 17.1 16.1 16.5 Water cut (%) 45 37 39 42 <![CDATA[Daily oil production (m 3 )]]> 8.6 10.7 9.8 9.6 Flowing fluid level (m) 1570 1630 1580 1600

[0168] It can be seen from the data of Example 3, Example 6, Example 9 and Example 12, as well as Table 1 that when the surfactant permeability enhancer for enhancing production in low-permeability reservoirs provided by the present invention is used for deep profile control in ultra-low permeability reservoirs, the water content in the stock solution drops significantly, and the oil production increases remarkably (in the blank experiment, the average daily liquid production was 35.7 m 3 , the water content was 100%, the daily oil production was 0, and the flowing fluid level was below 950 m).

[0169] Comparative Example 1

[0170] The difference between Comparative Example 1 and Example 7 is only that: no non-ionic surfactant was added.

[0171] Comparative Example 2

[0172] The difference between Comparative Example 2 and Example 7 is only that: perfluorohexylethylsulfonamidopropyl ethylcarboxybetaine was not added to the betaine-type surfactant.

[0173] Comparative Example 3

[0174] The difference between Comparative Example 3 and Example 7 is only that: no graphene was added.

[0175] The experimental results of the core spontaneous imbibition recovery degree and the oil-phase contact angle before and after spontaneous imbibition of Comparative Examples 1-3 are shown in Table 4

[0176] Table 4

[0177] Comparative example 1 Comparative example 2 Comparative example 3 Small pore recovery rate (25°C) 26％ 33％ 36％ Small pore recovery rate (65°C) 34％ 42％ 45％ Large pore recovery rate (25°C) 11％ 17％ 19％ Large pore recovery rate (65°C) 41％ 59％ 65％ Total recovery rate (25°C) 15％ 27％ 31％ Total recovery rate (65°C) 32％ 48％ 52％ Oil phase contact angle before imbibition 36.7° 37.3° 37.6° Oil phase contact angle after imbibition 105.2° 109.7° 114.2°

[0178] Comparative Example 4

[0179] The difference between Comparative Example 4 and Example 8 is only that: no non-ionic surfactant was added.

[0180] Comparative Example 5

[0181] The difference between Comparative Example 5 and Example 8 is only that: perfluorohexylethylsulfonamidopropyl ethylcarboxybetaine was not added to the betaine-type surfactant.

[0182] Comparative Example 6

[0183] The difference between Comparative Example 6 and Example 8 is only that: no graphene was added.

[0184] The experimental results of Comparative Examples 4-6 for volume fracturing of tight oil reservoirs are shown in Table 5:

[0185] Table 5:

[0186] Comparative example 4 Comparative example 5 Comparative example 6 Monthly production of the test well in the first month after production 381t 398t 405t Monthly production of the test well in the second month after production 396t 404t 401t Monthly production of the test well in the third month after production 402t 410t 409t Monthly production of the test well in the fourth month after production 411t 416t 414t Monthly production of the test well in the fifth month after production 417t 401t 407t Monthly production of the test well in the sixth month after production 410t 405t 412t Total production of the test well after production 2401t 2434t 2448t

[0187] Comparative Example 7

[0188] The difference between Comparative Example 7 and Example 9 is only that no non-ionic surfactant is added.

[0189] Comparative Example 8

[0190] The difference between Comparative Example 8 and Example 9 is only that perfluorohexylethylsulfonamidopropyl ethyl carboxybetaine is not added to the betaine-type surfactant.

[0191] Comparative Example 9

[0192] The difference between Comparative Example 9 and Example 9 is only that graphene is not added.

[0193] The experimental results of Comparative Examples 7-9 for volume fracturing in tight reservoirs are shown in Table 6:

[0194] Table 6

[0195] Comparative example 7 Comparative example 8 Comparative example 9 <![CDATA[Nissan liquid (m 3 )]]> 14.7 16.2 15.5 Water cut (%) 62 67 49 <![CDATA[Daily oil production (m 3 )]]> 5.6 5.3 7.6 Flowing fluid level (m) 1560 1660 1570

[0196] From the experimental data of Comparative Examples 1-9 and Tables 4-6, it can be seen that when no non-ionic surfactant is added, all indicators of the surface-active permeability enhancer for enhancing production in low-permeability reservoirs decrease significantly. On the one hand, the reason is that after losing the non-ionic surfactant, the remaining betaine-type surfactant is an amphoteric surfactant, and there is a certain electrostatic repulsion between the amphoteric surfactants, which makes the arrangement of surfactant molecules less compact than before, so the effect of reducing the surface tension is poor. On the other hand, after losing the double-short fluorocarbon chain non-ionic surfactant, there is no connecting effect of polyethylene glycol, which further makes the arrangement of surfactants at the oil-water interface loose.

[0197] When perfluorohexylethylsulfonamidopropyl ethyl carboxybetaine is not added, the synergistic adsorption effect of the surface-active permeability enhancer at the oil-water interface decreases, which will further reduce the production enhancement effect.

[0198] The influence effect of graphene oxide on reservoir production enhancement is small, but compared with the addition amount and the effect of enhancing production, it still achieves the result of cost reduction and efficiency improvement.

[0199] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A surfactant permeability enhancer for enhancing production in low-permeability reservoirs, characterized in that, The surfactant penetration enhancer comprises raw materials in the following parts by weight: 15-30 parts of betaine surfactant, 25-40 parts of nonionic surfactant, 1-5 parts of modified nano-silica, 0.5-3 parts of graphene, and 300-600 parts of water; The betaine surfactant is composed of cocamidopropyl betaine and perfluorohexylethylsulfonamidopropyl ethyl carboxybetaine mixed in a mass ratio of (1-1.5):1; The nonionic surfactant is composed of a fluorocarbon chain nonionic surfactant and ethylenediamine oleate mixed in a mass ratio of (2-3):1; The fluorocarbon chain nonionic surfactant is a double-short fluorocarbon chain nonionic surfactant, and the preparation process of the double-short fluorocarbon chain nonionic surfactant is as follows: 1) Mix 1H,1H,2H,2H-perfluorohexan-1-ol and isophorone diisocyanate evenly according to a molar ratio of 1:1, and heat up to 80 °C; 2) Add bismuth neodecanoate to the heated reaction solution and react at a constant temperature for 5 h; 3) Continuously add an excessive amount of polyethylene glycol to the reaction solution and continue to react at a constant temperature for 7 h; 4) Filter the crude product, dialyze and purify the filtered product in deionized water for 12 h, and freeze-dry the purified product to obtain the double-short fluorocarbon chain nonionic surfactant; The modification process of the nano-silica includes the following steps: S1: Mix ethanol and 3-mercaptopropyltriethoxysilane according to a mass ratio of (4.5-5.5):1; S2: Add nano-silica with a mass of 1 / 120-1 / 110 of the mixed solution obtained in S1 to the mixed solution obtained in S1, and carry out a stirring reaction at 25 °C; S3: Centrifuge, wash, recrystallize, and dry the reaction product obtained in S2 in sequence, and obtain an intermediate product after drying; S4: Disperse the intermediate product obtained in S3 in dimethylformamide according to a mass ratio of 1:(195-205), and carry out ultrasonic dispersion; S5: Add an oxygen-containing salt with the same mass as the intermediate product in S3 to the product obtained by ultrasonic dispersion in S4, and use a fluorosurfactant as an initiator to carry out a reaction at 25 °C under an inert gas atmosphere; S6: Transfer the product obtained in S5 to cyclohexane, collect the precipitate and dry it to obtain the modified nano-silica.

2. The surfactant permeability enhancer for enhancing production in low-permeability reservoirs according to claim 1, wherein The surfactant penetration enhancer comprises raw materials in the following parts by weight: 20-25 parts of betaine surfactant, 30-35 parts of nonionic surfactant, 2-3 parts of modified nano-silica, 1.5-2 parts of graphene, and 400-500 parts of water.

3. The surfactant permeability enhancer for enhancing production in low-permeability reservoirs according to claim 1, wherein The solvent used for recrystallization in S3 is acetonitrile; The oxygen-containing salt used in S5 is sodium oleate, and the fluorosurfactant is sodium perfluorononenyloxybenzenesulfonate; The inert gas is one of nitrogen and helium; 4. The surfactant permeability enhancer for enhancing production in low-permeability reservoirs according to claim 1, wherein When carrying out the stirring reaction in S2, the stirring speed is 500-600 r / min, and the stirring time is 25-30 min; The ultrasonic dispersion time in S4 is 25-30 min, the dispersion power is 1000-1100 W, and the dispersion frequency is 20-25 KHz.

5. A preparation method of a surfactant permeability enhancer for enhancing production in a low-permeability reservoir according to any one of claims 1-4, characterized in that, Comprising the following steps: Weigh the following raw materials by weight parts: 15-30 parts of betaine-type surfactant, 25-40 parts of non-ionic surfactant, 1-5 parts of modified nano-silica, 0.5-3 parts of graphene, and 300-600 parts of water; Mix the betaine-type surfactant, non-ionic surfactant and 90% of water evenly to obtain a surfactant base liquid; Mix the modified nano-silica with the remaining 10% of water evenly to obtain a silica base liquid; Add graphene and silica base liquid to the surfactant base liquid under the conditions of ultrasonic dispersion and mechanical stirring to obtain the surface active permeability enhancer; 6. Use of a surfactant permeability enhancer for enhancing production in a low-permeability reservoir according to any one of claims 1-4, characterized in that, The surface active permeability enhancer is used as a chemical agent in the exploitation process of low-permeability oil reservoirs.

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