A low-damage fracturing fluid system for preventing core collapse and a preparation method thereof

Abstract

The present invention discloses a low-damage fracturing fluid system for preventing core collapse and a preparation method thereof, which comprises, by weight percentage, 0.05% to 1.5% of an emulsion fracturing fluid thickener, 0.6% to 1.2% of an anti-collapse agent, 0.1% to 0.3% of an emulsion demulsifier, 0.002% to 0.15% of a gel breaker, and the remainder of water. The interface regulator of the present invention can reduce the interfacial tension, and can also reduce the Jamin effect and the water lock effect in the post-pressure backflow oil production process, improve the backflow rate, reduce damage, and also increase production. The reagents in the entire anti-collapse low-damage non-mixing fracturing fluid system are all liquids, and a non-mixing process can be realized on site. At the same time, the dosage is low, and the product production cost, dosage cost, and construction cost are all low. The emulsion fracturing fluid system has low residue, has little damage to such highly water-sensitive, weakly cemented, and easily loose reservoirs, and has a certain salt resistance, and can be prepared using backflow water.

Description

Technical Field

[0001] The invention relates to a core collapse-proof low-damage fracturing fluid system and a preparation method thereof, and belongs to the technical field of oil and gas field development. Background Art

[0002] Fracturing technology is an important measure to improve the recovery rate of tight oil reservoirs. However, if the fracturing fluid is incompatible with the clay minerals in the formation, the permeability of the oil and gas field will be reduced. The present invention is mainly aimed at certain reservoirs that are mainly tuff, have high clay mineral content, are highly water-sensitive, weakly cemented, and easily loose. The entry of the fracturing fluid system will cause the rock skeleton to collapse and block the fracturing cracks, resulting in the post-fracturing liquid production not reaching the expected fracturing effect. There are several specific problems:

[0003] ① The clay content of the reservoir is high, which is very easy to hydrate and expand. For low-permeability reservoirs with very low porosity, it will cause the size of pore throats and cracks to shrink, causing greater water-sensitive damage. In particular, the impact will be greater for reservoirs with obvious micro-crack characteristics and serious micro-pore heterogeneity. In severe cases, micro-cracks and micro-pore throats may be blocked, resulting in low production after fracturing;

[0004] ② The reservoir is weakly cemented and easy to loosen. The self-cementation between the matrix and the skeleton particles is weak, resulting in loose and fragile rocks and strong stress sensitivity. For such special sensitive reservoirs, a small amount of liquid entering will cause the clay to hydrate and expand. Once the clay expands slightly, the weakly cemented reservoir will collapse, produce sand, destroy the fracture network, block the artificial fractures, reduce its conductivity, and thus greatly reduce production.

[0005] The existing technology is basically aimed at the technology of preventing clay swelling in water-based fracturing fluids. There are relatively more studies on clay stabilizers, but there are no literature reports on the technology of fracturing fluids to prevent collapse. There are anti-collapse technologies in the drilling fluid system, but there are currently no literature reports on the research of inhibiting reservoir collapse during fracturing construction.

[0006] Patent CN201410164776.7 "An oil well anti-swelling fracturing fluid and its preparation method", its thickener is plant gum, and the anti-swelling additive is a composite of ammonium chloride, potassium chloride, cationic polymer, small cationic polymer and anti-migration sand consolidation agent. It mainly uses the cation effect to form a good adsorption layer on the surface of the clay crystal layer, effectively isolating the clay minerals from the external fluid, thereby inhibiting the hydration expansion and migration of the clay minerals, and reducing the water-sensitive damage of the external working fluid to the oil layer.

[0007] Articles "Analysis of the anti-collapse mechanism of saturated salt water drilling fluid on high expansion tuff", "Properties of water-sensitive tuff in Lancang lead mine and development of anti-collapse drilling fluid" - Zheng Mingxiong. The anti-collapse drilling fluid system is a drilling fluid with saturated filtrate of tuff + saturated NaCl + soluble starch + NaOH as anti-collapse components. Saturated filtrate of tuff + saturated NaCl + NaOH is a chemical method to prevent salt dissolution, and soluble starch is used for physical water isolation.

[0008] Article "Application of anti-collapse drilling fluid in the third opening of Jinlongjing area" - Wang Xinyu, its anti-collapse system is white asphalt + sulfomethyl phenolic resin SMP-1 + silicone FMS-1. The main function of white asphalt is to form a plugging film, the main function of sulfomethyl phenolic resin SMP-1 is to increase the aggregation stability of clay particles and reduce filtration, and the main function of silicone FMS-1 is to use chemical reaction polycondensation to form an adsorption layer, slow down hydration, and reduce the interaction between clays.

[0009] There is no related supporting technology in the existing fracturing system to solve this problem. There are related technologies in the drilling fluid system, but they cannot be applied to the fracturing fluid system. The main problems are as follows:

[0010] ① The supersaturated brine used in the prior art has a high salt concentration and a large amount of salt, resulting in high costs. Secondly, the high salt concentration requires the fracturing fluid thickener to have stronger salt resistance, and the amount of thickener added also needs to be increased, which further increases the cost of the fracturing fluid. In addition, inorganic salts are solids, and the mixing-free process cannot be used on site.

[0011] ②Soluble starch, as a physical plug, will cause new damage to the reservoir.

[0012] ③ White asphalt, sulfomethylphenolic resin SMP-1, and silicone FMS-1. There are problems with the compatibility of this system of additives with the fracturing fluid system. The cost of silicone is relatively high, and SMP-1 filtration loss reduction may also cause new damage to the reservoir. Summary of the invention

[0013] In order to solve the problems in the prior art that when a reservoir composed mainly of tuff with a high clay mineral content, strong water sensitivity, weak cementation and easy looseness comes into contact with a fracturing fluid system, clay hydration expansion, rock skeleton collapse and blockage of fracturing cracks, the purpose is to provide a high-efficiency core collapse-proof and low-damage fracturing fluid system and a preparation method. The fracturing fluid can now reduce the damage of the fracturing fluid to the reservoir and increase the post-fracturing production.

[0014] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0015] A highly efficient core collapse prevention and low-damage fracturing fluid system, comprising, by weight percentage:

[0016] 0.05% to 1.5% of emulsion fracturing fluid thickener, 0.6% to 1.2% of anti-collapse agent, 0.1% to 0.3% of demulsifier, 0.002% to 0.15% of gel breaker, and the balance of water.

[0017] A further improvement of the present invention is that the thickener of the emulsion fracturing fluid is modified polyacrylamide.

[0018] A further improvement of the present invention is that the anti-collapse agent is prepared by the following process: by weight percentage, 10-20% of a quaternary ammonium clay stabilizer, 45-55% of an amino clay stabilizer, and 30-40% of an interface regulator are stirred uniformly.

[0019] A further improvement of the present invention is that the quaternary ammonium clay stabilizer is dimethylallyl ammonium chloride, epoxypropyl trimethyl ammonium chloride, 2-chloroethyl trimethyl ammonium chloride or benzyl trimethyl ammonium chloride;

[0020] A further improvement of the present invention is that the quaternary ammonium clay stabilizer is benzyltrimethylammonium chloride;

[0021] A further improvement of the present invention is that the amino clay stabilizer is 2-hydroxyethyltrimethylamine chloride, diethylenetriamine salt or tetraethylenepentaamine salt;

[0022] A further improvement of the present invention is that the amino clay stabilizer is 2-hydroxyethyltrimethylamine chloride;

[0023] A further improvement of the present invention is that the interface regulator is one or more of alkylbenzene sulfonate, alkyl sulfate, petroleum sulfonate, alkyl hydroxypropyl sulfobetaine, mixed carbon chain isomeric alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, modified alkanolamide and alkyl glycoside.

[0024] A further improvement of the present invention is that the interface regulator is one or more of mixed carbon chain isomeric alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether and modified alkanolamide;

[0025] A further improvement of the present invention is that the alkylbenzene sulfonate is dodecylbenzene sulfonate;

[0026] The alkyl sulfate is lauryl sulfate;

[0027] Petroleum sulfonates are petroleum sulfonates;

[0028] The alkyl hydroxypropyl sulfobetaine is tetradecyl hydroxypropyl sulfobetaine;

[0029] The mixed carbon chain isomeric alcohol polyoxyethylene ether is a mixed carbon chain isomeric alcohol polyoxyethylene ether;

[0030] The fatty alcohol polyoxyethylene ether is lauryl fatty alcohol polyoxyethylene ether;

[0031] The alkylphenol polyoxyethylene ether is nonylphenol polyoxyethylene ether;

[0032] The modified alkanolamide is sodium lauric acid diethanolamide sulfate;

[0033] The alkyl glycoside is a C10-C14 alkyl glycoside.

[0034] A further improvement of the present invention is that the demulsifier is a polyether surfactant.

[0035] A further improvement of the present invention is that the breaker is selected from ammonium persulfate, potassium persulfate, sodium persulfate and capsule breaker.

[0036] A method for preparing the high-efficiency core collapse prevention and low-damage fracturing fluid system as described above comprises adding an emulsion fracturing fluid thickener, an anti-collapse agent, a demulsifier and a gel breaker into water, stirring the mixture evenly, and obtaining the high-efficiency core collapse prevention and low-damage fracturing fluid system.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The interface control agent of the present invention can reduce the interfacial tension, and can also reduce the Jamin effect and the water lock effect in the process of post-pressure backflow oil production, improve the backflow rate, reduce damage, and also increase production. The reagents in the entire anti-collapse low-damage non-mixing fracturing fluid system are all liquids, and the non-mixing process can be realized on site. At the same time, the dosage is low, and the product production cost, dosage cost, and construction cost are all low. The emulsion fracturing fluid system has low residue and has little damage to such highly water-sensitive, weakly cemented, and easily loose reservoirs. At the same time, it has a certain salt resistance and can be prepared using backflow water. The fracturing fluid system itself is a clean fracturing fluid. The gel breaking determination shows that the residue content of the gel breaking fluid is less than 30 mg / L, which reduces the damage caused by the residue in the gel breaking fluid and avoids water sensitivity and residue coupling superposition damage to the reservoir.

[0039] Furthermore, by compounding the quaternary ammonium clay stabilizer with the amino clay stabilizer, the clay anti-swelling rate is ensured to be greater than 95%. When the reservoir clay minerals come into contact with the working fluid, the hydration expansion of the clay minerals can be inhibited, thereby inhibiting the collapse of the reservoir rock skeleton. At the same time, the organic anti-swelling agent has a long effective period.

[0040] Furthermore, the interface modifier in the present invention is one or more of alkylbenzene sulfonate, alkyl sulfate, petroleum sulfonate, alkyl hydroxypropyl sulfobetaine, mixed carbon chain isomeric alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, modified alkanolamide and alkyl polyglycoside, which can reduce the oil-water interfacial tension to 10 -3 mN / m, and the surface tension is lower than 28mN / m, which greatly reduces the capillary suction force and reduces the infiltration of the working fluid into the reservoir through the surface of the reservoir micropores, thereby inhibiting the collapse of the reservoir.

[0041]

[0042] Where:

[0043] P c —capillary forces;

[0044] σ—oil-water interfacial tension;

[0045] θ—wetting contact angle;

[0046] r—capillary radius. DETAILED DESCRIPTION

[0047] The present invention is described in detail below by way of examples.

[0048] A highly efficient core collapse prevention and low-damage fracturing fluid system, comprising the following components in percentage by weight:

[0049] 0.05% to 1.5% of emulsion fracturing fluid thickener, 0.6% to 1.2% of anti-collapse agent, 0.1% to 0.3% of demulsifier, 0.002% to 0.15% of gel breaker, and the balance of water;

[0050] The emulsion fracturing fluid thickener is selected from an emulsion thickener prepared from partially hydrolyzed modified polyacrylamide.

[0051] The anti-collapse agent is composed of the following components by weight percentage: 10-20% of a quaternary ammonium salt clay stabilizer, 45-55% of an amine-based clay stabilizer, and 30-40% of an interface regulator; the preparation method is: in a stirring container, the quaternary ammonium salt clay stabilizer, the amine-based clay stabilizer and the interface regulator are added and stirred evenly.

[0052] Wherein, the quaternary ammonium salt clay stabilizer is selected from dimethyl allyl ammonium chloride, epoxypropyl trimethyl ammonium chloride, 2-chloroethyl trimethyl ammonium chloride or benzyl trimethyl ammonium chloride, preferably benzyl trimethyl ammonium chloride;

[0053] The amine-based clay stabilizer is selected from 2-hydroxyethyltrimethylammonium chloride, diethylenetriamine salt or tetraethylenepentaamine salt, preferably 2-hydroxyethyltrimethylammonium chloride;

[0054] The interface regulator is selected from one or more of alkylbenzene sulfonate, alkyl sulfate, petroleum sulfonate, alkyl hydroxypropyl sulfobetaine, mixed carbon chain isomeric alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, modified alkanolamide and alkyl glycoside, preferably one or more of mixed carbon chain isomeric alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether and modified alkanolamide;

[0055] The alkylbenzene sulfonate is specifically dodecylbenzene sulfonate.

[0056] The alkyl sulfate is specifically lauryl sulfate.

[0057] The petroleum sulfonate is specifically petroleum sulfonate (KPS, boiling range: 400-600° C.).

[0058] The alkyl hydroxypropyl sulfobetaine is specifically tetradecyl hydroxypropyl sulfobetaine.

[0059] The mixed carbon chain isomeric alcohol polyoxyethylene ether is specifically mixed carbon chain isomeric alcohol (C12-14) polyoxyethylene ether.

[0060] The fatty alcohol polyoxyethylene ether is lauryl fatty alcohol polyoxyethylene ether (EO=3-6).

[0061] The alkylphenol polyoxyethylene ether is specifically nonylphenol polyoxyethylene ether (EO=3-6).

[0062] The modified alkanolamide is specifically sodium lauric acid diethanolamide sulfate.

[0063] The alkyl glycoside is specifically a C10-C14 alkyl glycoside.

[0064] The demulsifier is a polyether surfactant, and the specific model is GAF-7.

[0065] The breaker is selected from ammonium persulfate, potassium persulfate, sodium persulfate and capsule breaker;

[0066] The non-mixing fracturing fluid system is suitable for water with a mineralization of 0 to 30,000 mg / L.

[0067] Preparation method of fracturing fluid system:

[0068] 500 mL of preparation water was measured and poured into a 1 L beaker. The stirring speed was set to 500 rpm. The corresponding amount of thickener and other additives were weighed. The thickener and various additives were quickly added to the water and stirred for 1 min to prepare the non-mixing fracturing fluid system of this formula.

[0069] The interface modifier in the present invention is one or more of alkylbenzene sulfonate, alkyl sulfate, petroleum sulfonate, alkyl hydroxypropyl sulfobetaine, mixed carbon chain isomeric alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, modified alkanolamide and alkyl polyglycoside, which can reduce the oil-water interfacial tension to 10 -3 mN / m, and the surface tension is lower than 28mN / m, which greatly reduces the capillary suction force and reduces the infiltration of the working fluid into the reservoir through the surface of the reservoir micropores, thereby inhibiting the collapse of the reservoir.

[0070]

[0071] Where:

[0072] P c —capillary forces;

[0073] σ—oil-water interfacial tension;

[0074] θ—wetting contact angle;

[0075] r—capillary radius.

[0076] Example 1

[0077] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 0.6% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.8% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.15% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.05% of a breaker (ammonium persulfate, PJ-2, Chengdu Kelon Chemical Reagent Factory) and the remainder of water.

[0078] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-2, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0079] The preparation method of the anti-collapse agent:

[0080] In a stirring container, add 20% benzyltrimethylammonium chloride, 45% 2-hydroxyethyltrimethylammonium chloride, and 35% mixed carbon chain isomeric alcohol polyoxyethylene ether in the following proportions and stir evenly.

[0081] Comparative Example 1

[0082] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 0.6% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.15% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.05% of a breaker (ammonium persulfate, PJ-2, Chengdu Kelon Chemical Reagent Factory) and the remainder of water.

[0083] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, demulsifier GAF-7, and gel breaker PJ-2, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0084] Comparative Example 2

[0085] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 0.6% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.8% of a clay stabilizer (benzyltrimethylammonium chloride), 0.15% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.05% of a gel breaker (ammonium persulfate, PJ-2, Chengdu Kelon Chemical Reagent Factory) and the remainder of water.

[0086] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, clay stabilizer, demulsifier GAF-7, and gel breaker PJ-2, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0087] Comparative Example 3

[0088] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 0.6% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.8% of a clay stabilizer (2-hydroxyethyltrimethylammonium chloride), 0.15% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.05% of a gel breaker (ammonium persulfate, PJ-2, Chengdu Kelon Chemical Reagent Factory) and the remainder of water.

[0089] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, clay stabilizer, demulsifier GAF-7, and gel breaker PJ-2, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0090] Comparative Example 4

[0091] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 0.6% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.8% of an interface regulator (mixed carbon chain isomeric alcohol polyoxyethylene ether), 0.15% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.05% of a breaker (ammonium persulfate, PJ-2, Chengdu Kelon Chemical Reagent Factory) and the remainder of water.

[0092] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, interface regulator, demulsifier GAF-7 and gel breaker PJ-2, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0093] Comparative Example 5

[0094] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 0.6% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.8% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.15% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.05% of a breaker (ammonium persulfate, PJ-2, Chengdu Kelon Chemical Reagent Factory) and the remainder of water.

[0095] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-2, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0096] The preparation method of the anti-collapse agent:

[0097] In a stirring container, add 30% benzyltrimethylammonium chloride and 70% 2-hydroxyethyltrimethylammonium chloride in the following proportions and stir evenly.

[0098] Comparative Example 6

[0099] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 0.6% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.8% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.15% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.05% of a breaker (ammonium persulfate, PJ-2, Chengdu Kelon Chemical Reagent Factory) and the remainder of water.

[0100] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-2, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0101] The preparation method of the anti-collapse agent:

[0102] In a stirring container, add 56% of 2-hydroxyethyltrimethylamine chloride and mixed carbon chain isomeric alcohol polyoxyethylene ether in the following proportions and stir evenly.

[0103] According to the testing standard SY / T 5107-2005 "Water-based fracturing fluid performance evaluation method", the fracturing fluid system prepared in the above examples and comparative examples and the residue content test, surface / interfacial tension and anti-swelling rate test of the fracturing fluid degelling liquid were tested.

[0104] Weakly cemented core collapse prevention test:

[0105] The fracturing fluid system prepared in the above examples and comparative examples was degelled at high temperature to obtain degelled fluid.

[0106] Take a 250mL wide-mouth flask, add 60g of debonding liquid into the wide-mouth flask, preheat it to 80℃ in a water bath, then put about 20g of weakly cemented rock into the wide-mouth flask, observe the changes of rock state (peeling, collapse, etc.) over time at 80℃, and end the experiment when the core collapses completely or is soaked for 48h.

[0107] The specific results are shown in Table 1 below.

[0108] Table 1 Comparative Example Weakly Cemented Core Collapse Prevention Test Results

[0109]

[0110]

[0111] It can be seen from the above comparative tests that, under the conditions of determined reservoir temperature, mineralization of preparation water, and fixed concentration of the emulsion fracturing fluid thickener, with the addition of the composite anti-collapse agent, the high-efficiency anti-collapse fracturing fluid system can inhibit the collapse of weakly cemented cores, while the single agent in the composite anti-collapse agent has a certain inhibitory effect on the weakly cemented cores, but it eventually collapsed. Only when the three agents are compounded in a certain proportion will they have good anti-collapse performance and meet various indicators of the fracturing fluid to ensure post-fracturing production.

[0112] Example 2

[0113] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 0.05% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.6% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.1% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.002% of a breaker (sodium persulfate, PJ-1, Chengdu Kelon Chemical Reagent Factory) and the remainder of water.

[0114] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-1, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0115] Wherein, the preparation method of the anti-collapse agent is:

[0116] In a stirring container, add 15% benzyltrimethylammonium chloride, 45% 2-hydroxyethyltrimethylammonium chloride, and 40% fatty alcohol polyoxyethylene ether according to the following weight percentages and stir evenly.

[0117] Example 3

[0118] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 0.6% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.8% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.15% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.05% of a breaker (ammonium persulfate, PJ-2, Chengdu Kelon Chemical Reagent Factory) and the remainder of water.

[0119] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-2, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0120] The preparation method of the anti-collapse agent:

[0121] In a stirring container, add 20% of benzyltrimethylammonium chloride, 45% of 2-hydroxyethyltrimethylammonium chloride, and 35% of mixed carbon chain isomeric alcohol polyoxyethylene ether according to the following weight percentages and stir evenly.

[0122] Example 4

[0123] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 1.0% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 1.0% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.2% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.1% of a breaker (potassium persulfate, PJ-3, Chengdu Kelon Chemical Reagent Factory) and the remainder of water.

[0124] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-3, quickly add the thickener and various additives into the water, stir for 1 minute, and the mixing-free fracturing fluid system of this formula is prepared.

[0125] The preparation method of the anti-collapse agent:

[0126] In a stirring container, add 15% of benzyltrimethylammonium chloride, 55% of 2-hydroxyethyltrimethylammonium chloride, and 30% of mixed carbon chain isomeric alcohol polyoxyethylene ether according to the following weight percentages and stir evenly.

[0127] Example 5

[0128] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 1.5% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 1.2% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.3% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.15% of a gel breaker (capsule gel breaker, PJ-4, Shaanxi Senrui Petroleum Technology Development Co., Ltd.) and the remainder of water.

[0129] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-4, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0130] The preparation method of the anti-collapse agent:

[0131] In a stirring container, add 10% benzyltrimethylammonium chloride, 50% 2-hydroxyethyltrimethylammonium chloride, and 40% modified alkanolamide (sodium lauric acid diethanolamide sulfate) according to the following weight percentages, and stir evenly.

[0132] According to the testing standard SY / T 5107-2005 "Water-based fracturing fluid performance evaluation method", the fracturing fluid system prepared in the above embodiment and the residue content test, surface / interfacial tension and anti-swelling rate test of the fracturing fluid degelling liquid were tested.

[0133] Weakly cemented core collapse prevention test:

[0134] The fracturing fluid system prepared in the above example is degelled at high temperature to obtain degelled fluid.

[0135] Take a 250mL wide-mouth flask, add 60g of debonding liquid into the wide-mouth flask, preheat it to 80℃ in a water bath, then put about 20g of weakly cemented rock into the wide-mouth flask, observe the changes of rock state (peeling, collapse, etc.) over time at 80℃, and end the experiment when the core collapses completely or is soaked for 48h.

[0136] The specific results are shown in Table 2 below.

[0137] Table 2 Example weakly cemented core anti-collapse test results

[0138]

[0139]

[0140] It can be seen from the comparative tests in Tables 1 and 2 above that, under the conditions of a certain reservoir temperature, salinity of the preparation water, and a fixed concentration of the emulsion fracturing fluid thickener, the high-efficiency anti-collapse fracturing fluid system can inhibit the collapse of weakly cemented cores, meet various indicators of the fracturing fluid, and ensure the post-fracturing production.

[0141] Example 6

[0142] A high-efficiency anti-core collapse low-damage fracturing fluid system, with its total weight as 100%, comprises: 0.8% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.6% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.1% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.007% of a gel breaker (capsule gel breaker, PJ-4, Shaanxi Senrui Petroleum Technology Development Co., Ltd.) and the remainder of water.

[0143] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-4, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0144] The preparation method of the anti-collapse agent:

[0145] In a stirring container, add 10% of dimethylallylammonium chloride, 55% of 2-hydroxyethyltrimethylammonium chloride, 35% of a mixture of sodium lauric acid diethanolamide sulfate and nonylphenol polyoxyethylene ether (EO=3-6) according to the following weight percentages, and stir evenly.

[0146] Example 7

[0147] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 1.2% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.7% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.2% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.1% of a gel breaker (capsule gel breaker, PJ-4, Shaanxi Senrui Petroleum Technology Development Co., Ltd.) and the remainder of water.

[0148] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-4, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0149] The preparation method of the anti-collapse agent:

[0150] In a stirring container, add 20% of glycidyltrimethylammonium chloride, 45% of 2-hydroxyethyltrimethylammonium chloride, and 35% of tetradecylhydroxypropylsulfobetaine according to the following weight percentages and stir evenly.

[0151] Example 8

[0152] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 0.1% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 1.1% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.15% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.12% of a gel breaker (capsule gel breaker, PJ-4, Shaanxi Senrui Petroleum Technology Development Co., Ltd.) and the remainder of water.

[0153] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-4, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0154] The preparation method of the anti-collapse agent:

[0155] In a stirring container, add 15% of 2-chloroethyltrimethylammonium chloride, 50% of 2-hydroxyethyltrimethylammonium chloride, and 35% of petroleum sulfonate (KPS, boiling range: 400-600°C) according to the following weight percentages, and stir evenly.

[0156] Example 9

[0157] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 0.3% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 1% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.25% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.005% of a gel breaker (capsule gel breaker, PJ-4, Shaanxi Senrui Petroleum Technology Development Co., Ltd.) and the balance of water.

[0158] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-4, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0159] The preparation method of the anti-collapse agent:

[0160] In a stirring container, add 18% benzyltrimethylammonium chloride, 52% tetraethylenepentaamine salt, and 30% dodecyl sulfate according to the following weight percentages and stir evenly.

[0161] Example 10

[0162] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 1.3% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 1.2% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.25% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.13% of a gel breaker (capsule gel breaker, PJ-4, Shaanxi Senrui Petroleum Technology Development Co., Ltd.) and the balance of water.

[0163] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-4, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0164] The preparation method of the anti-collapse agent:

[0165] In a stirring container, add 12% benzyltrimethylammonium chloride, 28% diethylenetriamine salt, and 40% dodecylbenzene sulfonate according to the following weight percentages and stir evenly.

[0166] Embodiment 11

[0167] The invention discloses a high-efficiency core collapse prevention and low-damage fracturing fluid system, which comprises, with its total weight as 100%, 1.5% of an emulsion fracturing fluid thickener (modified polyacrylamide, GAF-RE, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.8% of an anti-collapse agent (Sichuan Guangya Polymer Chemical Co., Ltd.), 0.2% of a demulsifier (polyether surfactant, GAF-7, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.1% of a gel breaker (capsule gel breaker, PJ-4, Shaanxi Senrui Petroleum Technology Development Co., Ltd.) and the remainder of water.

[0168] Preparation method: Measure 500 mL of preparation water and pour it into a 1 L beaker, set the stirring speed to 500 rpm, weigh the corresponding amount of emulsion thickener GAF-RE, anti-collapse agent, demulsifier GAF-7, and gel breaker PJ-4, quickly add the thickener and various additives into the water, stir for 1 minute, and the non-mixing fracturing fluid system of this formula is prepared.

[0169] The preparation method of the anti-collapse agent:

[0170] In a stirring container, add 12% benzyltrimethylammonium chloride, 28% diethylenetriamine salt, and 40% alkyl glycoside, specifically C10 alkyl glycoside, according to the following weight percentages, and stir evenly.

[0171] The clay anti-swelling rate of the high-efficiency core collapse prevention and low-damage fracturing fluid system of the present invention is greater than 95%. When the reservoir clay minerals come into contact with the working fluid, the hydration expansion of the clay minerals and the collapse of the reservoir rock skeleton can be effectively inhibited. At the same time, it has the advantages of small reservoir damage, low cost and simple preparation.

Claims

1. A highly efficient and low-damage fracturing fluid system for preventing core collapse, characterized in that: In terms of weight percentage, it includes: 0.05% to 1.5% of emulsion fracturing fluid thickener, 0.6% to 1.2% of anti-collapse agent, 0.1% to 0.3% of demulsifier, 0.002% to 0.15% of gel breaker, and the balance of water; The emulsion fracturing fluid thickener is an emulsion thickener prepared from modified polyacrylamide; The anti-collapse agent is prepared by the following process: by weight percentage, 10-20% of a quaternary ammonium clay stabilizer, 45-55% of an amino clay stabilizer, and 30-40% of an interface regulator are stirred uniformly; The quaternary ammonium salt clay stabilizer is dimethylallyl ammonium chloride, epoxypropyl trimethyl ammonium chloride, 2-chloroethyl trimethyl ammonium chloride or benzyl trimethyl ammonium chloride; The amino clay stabilizer is 2-hydroxyethyltrimethylamine chloride, diethylenetriamine salt or tetraethylenepentaamine salt; The interface regulator is one or more of alkylbenzene sulfonate, alkyl sulfate, petroleum sulfonate, alkyl hydroxypropyl sulfobetaine, alkylphenol polyoxyethylene ether and alkyl polyglycoside; The alkylbenzene sulfonate is dodecylbenzene sulfonate; The alkyl sulfate is lauryl sulfate; Petroleum sulfonate is a petroleum sulfonate, boiling range: 400-600°C; The alkyl hydroxypropyl sulfobetaine is tetradecyl hydroxypropyl sulfobetaine; Alkylphenol polyoxyethylene ether is nonylphenol polyoxyethylene ether, EO=3-6; The alkyl glycoside is a C10-C14 alkyl glycoside.

2. The high-efficiency and low-damage fracturing fluid system for preventing core collapse according to claim 1, characterized in that: The demulsifier is a polyether surfactant.

3. The high-efficiency and low-damage fracturing fluid system for preventing core collapse according to claim 1, characterized in that: The breaker is selected from ammonium persulfate, potassium persulfate, sodium persulfate and capsule breaker.

4. A method for preparing a high-efficiency anti-core collapse low-damage fracturing fluid system according to any one of claims 1 to 3, characterized in that: Add emulsion fracturing fluid thickener, anti-collapse agent, demulsifier and gel breaker into water and stir evenly to obtain a high-efficiency anti-core collapse and low-damage fracturing fluid system.

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