A high-efficiency anti-emulsification viscosity reducer and water-based fracturing fluid as well as preparation method and application thereof

Abstract

The present invention belongs to the technical field of reservoir transformation, and specifically relates to a highly efficient anti-emulsification and viscosity-reducing water-based fracturing fluid system and a preparation method thereof. An anti-emulsification and viscosity-reducing agent comprises the following components: triphenylvinylphenol polyoxyethylene or / and propylene block polyether sulfonate, Guerbet alcohol-based polyoxyethylene or / and propylene block polyether sulfonate, an alkyl alcohol amide complex and a solvent. The anti-emulsification and viscosity-reducing agent can be used to prepare a water-based fracturing fluid, and the fracturing fluid comprises the following components: an emulsion thickener, an anti-emulsification and viscosity-reducing agent, a pH regulator, a gel breaker, and water. The prepared fracturing fluid has good anti-emulsification and viscosity-reducing effects, can effectively reduce the emulsification of the injected fluid and crude oil during fracturing construction, and ensures that the viscosity of the emulsion formed by crude oil, fracturing fluid breaking fluid and formation water in the flowback stage is low, thereby enhancing the seepage capacity, and the output fluid is efficiently demulsified, thereby increasing crude oil production.

Description

Technical Field

[0001] The invention belongs to the technical field of reservoir transformation, and particularly relates to a high-efficiency anti-emulsification and viscosity-reducing water-based fracturing fluid system and a preparation method thereof. Background Art

[0002] Continental shale reservoirs are characterized by small distribution, low maturity, high oil density, high wax content, and high viscosity—characteristics of heavy oil. Unlike medium- and high-permeability heavy oil reservoirs, shale reservoirs are characterized by low or ultra-low permeability. These reservoirs are typically developed using a "large cluster horizontal well + multi-stage" hydraulic fracturing process and low-cost water-based fracturing fluid systems. In the actual development of these tight oil reservoirs, severe emulsification occurs within the reservoir, resulting in high emulsion viscosity that significantly reduces flow through the fractures. This makes demulsification of the produced fluid difficult, leading to significant production declines. Currently reported demulsifiers and viscosity reducers are primarily used in heavy oil chemical viscosity reduction, emulsion dehydration, and related fields. Due to the varying composition and physical properties of heavy oil, demulsifiers for these oils are highly specific. Reported agents either possess strong demulsification or viscosity reduction capabilities, rarely both. Even those that do possess these capabilities are costly and cannot meet the requirements for large-scale, cost-effective development of heavy oil in tight reservoirs.

[0003] Chinese patent CN102746470B discloses a highly efficient demulsifier for cycloalkyl heavy oil, which contains a modified polyether demulsifier monomer with a multi-layered, polyaromatic ring stereo network structure. However, the demulsifier is too specialized and has poor demulsification effects on other heavy oils with different physical properties.

[0004] For example, Chinese patent CN112409535A discloses a highly dispersible heavy oil viscosity reducer, whose molecular structure is a copolymer of monomers such as sodium styrene sulfonate, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid. When this type of polymer viscosity reducer is added to a fracturing fluid system, there is a risk of molecular chain degradation and failure due to high formation temperature and the action of persulfate breakers.

[0005] Chinese patent CN 111394080A discloses a formula for an efficient heavy oil viscosity reducer, comprising a composite system of graphene, an alkaline substance, and a surfactant or an oil-soluble polymer. Although the synergistic effect between graphene and the alkaline substance effectively reduces viscosity, the dosage required for water-based fracturing fluids is relatively large (0.05mg / ml-0.15mg / ml), resulting in excessive cost.

[0006] Therefore, in the context of the development of hydraulic fracturing technology for shale oil production, it is of great significance to develop a highly effective, low-cost, water-based fracturing fluid system that can reduce emulsification and viscosity for heavy oil rich in alkaline fused ring compounds and high colloid content (35-40%) to achieve profitable oilfield development. However, a low-cost, high-efficiency, low-cost, and low-efficiency fracturing fluid system for heavy or extra-heavy oil has not yet been reported.

[0007] The present invention aims to provide a low-cost water-based fracturing fluid system with efficient anti-emulsification and viscosity reduction functions for heavy oil and its preparation method, so as to solve the technical problems of severe emulsification between existing fracturing fluid systems and heavy oil in tight reservoirs (high emulsion viscosity and difficulty in demulsification) and high cost of large-scale development. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a low-cost water-based fracturing fluid system with efficient anti-emulsification and viscosity reduction functions for heavy oil. The fracturing fluid has a simple preparation method and good anti-emulsification and viscosity reduction effects. It can effectively reduce the emulsification of the injection fluid and crude oil during fracturing construction, and ensure that the emulsion formed by crude oil, fracturing fluid breaker and formation water in the backflow stage has low viscosity, thereby enhancing the seepage capacity, and the produced fluid can be efficiently demulsified, thereby increasing crude oil production.

[0009] To achieve the above objectives, the technical solutions provided by the present invention are as follows:

[0010] An anti-emulsification viscosity reducer comprises the following components: triphenyl vinyl phenol polyoxyethylene and / or propylene block polyether sulfonate, Guerbet alcohol-based polyoxyethylene and / or propylene block polyether sulfonate, an alkyl alcohol amide complex and a solvent.

[0011] Preferably, the solvent is any one or more of water, ethanol, ethylene glycol or glycerol;

[0012] More preferably, the solvent is a mixture of water and ethylene glycol; the mass ratio is water:ethylene glycol=8:2.

[0013] Preferably, the triphenylvinylphenol polyoxyethylene / propylene block polyether sulfonate sodium has a molecular structure as shown in formula (I):

[0014]

[0015] In the structure of formula (I), the number of ethylene oxide EO is m=1-30, and the number of propylene oxide PO is n=1-30; more preferably, m=12-18, and n=5-10.

[0016] The molecular structure of the Guerbet alcohol-based polyoxyethylene / propylene block polyether sulfonate is shown in Formula (II):

[0017]

[0018] In the structure of formula (II), R1 and R2 are long carbon chain alkyl groups, the carbon chain length is: the number of carbon atoms in the main chain of R1 is 5-20, the number of carbon atoms in the main chain of R2 is 5-20, the number of ethylene oxide groups is: m=1-50, and the number of propylene oxide groups is: n=1-50;

[0019] More preferably, the number of carbon atoms in the main chain of R1 is 12-18, the number of carbon atoms in the main chain of R2 is 8-18, m=15-25, and n=15-20.

[0020] Preferably, the alkylolamide complex is composed of 85-90% long-chain alkylolamide, 2-5% alkylamide ester / alkylamine ester by-product, 2-5% diethanolamine, and the balance water, wherein the molecular structure of the long-chain alkylolamide is as shown in formula (III):

[0021]

[0022] In the structure of formula (III), R is a long carbon chain alkyl group, and the number of carbon atoms in the main chain of R is 4-20; more preferably, the number of carbon atoms in the main chain of R is 12-18.

[0023] Another object of the present invention is to provide a method for preparing the anti-emulsification viscosity reducer, comprising the following steps:

[0024] The triphenylvinylphenol polyoxyethylene and / or propylene block polyether sulfonate, Guerbet alcohol-based polyoxyethylene and / or propylene block polyether sulfonate, alkyl alcohol amide complex and solvent are mixed.

[0025] The present invention also aims to provide the use of the anti-emulsification viscosity reducer in fracturing fluid.

[0026] The present invention also aims to provide a water-based fracturing fluid comprising the following components: an emulsion thickener, an anti-emulsification viscosity reducer, a pH regulator, a gel breaker, and water.

[0027] Preferably, the salinity of the water is 0-30000 mg / L.

[0028] Preferably, the fracturing fluid system comprises, by weight percentage, 0.01-1.5% of an emulsion thickener, 0.1-0.5% of an anti-emulsification viscosity reducer, 0.002-0.3% of a pH regulator, and 0.01-0.3% of a gel breaker.

[0029] Preferably, the fracturing fluid system further comprises, by weight percentage: 0.2-1.5% of a fracturing fluid additive;

[0030] Preferably, the fracturing fluid system further comprises, by weight percentage, 0.5-1.2% of a fracturing fluid additive.

[0031] Preferably, the emulsion thickener comprises, by weight percentage: 40-55% thickener, 40-45% mineral oil, 2-5% nonionic surfactant emulsifier, 0.5-1% suspension stabilizer and 5-10% low-carbon alcohol nonionic wetting agent.

[0032] Preferably, the thickener is selected from any one or more of ultra-high molecular weight polyacrylamide, copolymers of acrylamide and temperature-resistant and salt-resistant monomers, hydrophobic associating polymers, and novel structural polyacrylamide copolymers (comb-shaped, star-shaped, and slightly branched types, etc.).

[0033] More preferably, the thickener is a salt-resistant hydrophobic associating polymer.

[0034] Preferably, the pH adjuster is an organic base or an inorganic base;

[0035] Preferably, the organic base includes any one or more of ethanolamine, diethanolamine, triethanolamine, sodium methoxide, sodium ethoxide and potassium ethoxide;

[0036] Preferably, the inorganic base includes any one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate and sodium silicate;

[0037] More preferably, the organic base is diethanolamine;

[0038] Preferably, the inorganic base is sodium hydroxide.

[0039] Preferably, the breaker includes any one or more of ammonium persulfate, potassium persulfate, sodium persulfate, capsule breaker and redox breaker.

[0040] More preferably, the selected breaker is sodium persulfate.

[0041] Preferably, the fracturing fluid additive is selected from any one or more of a long-chain alkyl quaternary ammonium salt type clay stabilizer and a polyepoxysuccinic acid (sodium) alkaline scale inhibitor.

[0042] The purpose of adding the scale inhibitor to the system is to prevent the fracturing fluid system from breaking the gel and becoming weakly alkaline and forming scale in the wellbore.

[0043] Another object of the present invention is to provide a method for preparing a water-based fracturing fluid indoors, comprising the following steps:

[0044] (1) Add water, emulsion thickener, and pH adjuster in proportion and stir;

[0045] (2) Add the anti-emulsifier and fracturing fluid additive at the same time and stir to obtain the anti-emulsification polymer fracturing fluid system.

[0046] Preferably, the pH regulator is first prepared into a 1-10% solution before use, preferably a 5% solution.

[0047] Another object of the present invention is to provide an on-site preparation method of a water-based fracturing fluid, comprising the following steps:

[0048] According to the proportion, water, emulsion thickener, pH regulator, anti-emulsifier and fracturing fluid additive are pumped into the sand mixing tank at the same time for mixing to obtain the anti-emulsification polymer fracturing fluid system.

[0049] Compared with the prior art, the technical advantages of the present invention are:

[0050] (1) The anti-emulsification viscosity reducer of the present invention is a composite multifunctional additive. Through the synergistic effect (hydrogen bonding, interface self-assembly and alkaline effect) between special molecular structure surfactants, small molecule additives and alkaline substances readily available on the market, it effectively improves the dehydration effect of heavy oil, especially the demulsification effect of heavy oil produced fluid rich in alkaline polycyclic compounds and high colloid content (35-40%).

[0051] (2) The anti-emulsification and viscosity-reducing composite agent provided by the present invention has good interfacial activity, and no additional drainage agent is required to be added to the fracturing fluid system, thereby ensuring smooth flowback of the fracturing fluid.

[0052] (3) The present invention provides a set of low-cost water-based fracturing fluid systems with high-efficiency and anti-emulsification functions. This system is suitable for heavy oil with a viscosity of 10,000 mPa·s or more, high in colloid and alkaline nitrogen compounds. Its technical characteristics are as follows: demulsification effect: demulsification rate (3 min, 80°C): ≥85%, demulsification rate (24 h, 80°C): ≥98%; viscosity reduction rate: ≥80%. Other performance indicators meet the general standards of water-based fracturing fluid technology. It can effectively reduce the occurrence of emulsification between the injection fluid and crude oil during fracturing construction, and ensure that the emulsion formed by crude oil, fracturing fluid degelation fluid and formation water in the return stage has low viscosity, thereby enhancing the seepage capacity, and the output fluid is efficiently demulsified, thereby increasing crude oil production.

[0053] (4) The present invention provides a method for preparing an anti-emulsification and viscosity-reducing fracturing fluid system, which eliminates mixing, simplifies the on-site fluid preparation process, reduces overall costs, and achieves efficient development.

[0054] (5) The surfactants described in the present invention have unique surface activity, wettability, permeability and emulsification properties, are green and environmentally friendly, and according to the characteristics of crude oil or heavy oil, the combination of several surfactants has good synergistic effects, which can achieve rapid demulsification, viscosity reduction and reduction of oil-water interfacial tension in the process of heavy oil extraction.

[0055] (6) The micelle structure in heavy oil is relatively loose. Under polar conditions, the overlapping and stacked aggregates of colloid and asphaltene sheet molecules are formed by hydrogen bonding, resulting in high viscosity and resistance to demulsification. Surfactants can reduce surface tension and interfacial tension between oil and water, promoting the emulsification and dispersion of crude oil, and are therefore widely used in heavy oil chemical viscosity reduction. The present invention uses an anionic nonionic surfactant that is heat-resistant and salt-resistant and does not undergo chromatographic separation, which can meet both high temperature resistance and salt resistance requirements.

[0056] The polyaromatic ring block polyether sulfonate and the double-tail chain alcohol block polyether sulfonate provided by the present invention have good wettability and permeability. Under the action of a small molecule solvent, they can quickly reach the oil-water interface and self-assemble or form a relatively thin three-dimensional network structure through hydrogen bonding and molecular interface self-assembly, thereby preventing colloid or asphalt molecules from connecting into a relatively strong network structure through hydrogen bonding, breaking up aggregates formed by overlapping and stacking of colloid and asphalt sheet molecules, and transforming the supramolecular structure in the heavy oil from a higher level to a lower level, forming a relatively stable oil-water isolation performance and making it easier to break emulsions and dehydrate.

[0057] (7) When the alkali and alkylolamide compound system is added in the present invention, the surface tension of the emulsion is lower, which indicates that the two have a good synergistic effect. From the analysis of the molecular structure of crude oil components, the nitrogen-containing substances in crude oil are relatively high, and are mainly acidic or alkaline condensed ring compounds. Generally speaking, the addition of alkaline substances has a promoting effect on the viscosity reduction of heavy oil, because alkaline substances can react with polar components in crude oil to produce in-situ surfactant substances, thereby enhancing surface activity. Alkaline substances react with polar components in heavy oil to produce ionized surfactants, which reduce surface tension. Alkaline substances accelerate the dispersion of ionized surfactants from the surface to the interior of the solid, so that the polar components are exposed to the alkaline substances, further reducing the surface tension and further shrinking the oil droplets, thereby achieving the purpose of viscosity reduction. DETAILED DESCRIPTION

[0058] The present invention is described below by way of specific examples to make the technical solution of the present invention easier to understand and grasp, but the present invention is not limited thereto. The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0059] The sources of some reagents in the examples of the present invention are as follows:

[0060] Sodium triphenylvinylphenol polyoxyethylene / propylene block polyether sulfonate (TSP, produced by Nantong Chenrun Chemical Co., Ltd.);

[0061] Guerbet alcohol-based polyoxyethylene / propylene block polyether sulfonate sodium (EG, Sasol (China) Chemical Co., Ltd.);

[0062] Alkyl alcohol amide complex (NAS, Sichuan Guangya Polymer Chemical Co., Ltd.).

[0063] Comparative Example:

[0064] A fracturing fluid was prepared using tap water: 0.8 parts of an emulsion thickener (salt-resistant polyacrylamide FPY, Sichuan Guangya Polymer Chemical Co., Ltd.), 1 part of a fracturing fluid additive (50 wt% long-chain quaternary ammonium salt organoclay stabilizer GAF-16, Sichuan Guangya Polymer Chemical Co., Ltd. + 20 wt% fluorocarbon drainage aid OBS, Shanghai Futian Chemical Technology Co., Ltd. + 30 wt% sodium polyepoxysuccinate scale inhibitor PESA, Hebei Collaborative Chemical Co., Ltd.), 0.1 part of a breaker (sodium persulfate), and 98.1 parts of tap water. The prepared fracturing fluid was placed in a 90°C water bath for 4 hours to obtain a completely broken fluid.

[0065] Example 1:

[0066] Compared with the comparative example, the difference is that an alkaline pH regulator is added to the fracturing fluid system.

[0067] A fracturing fluid was prepared using tap water: 0.8 parts of an emulsion thickener (salt-resistant polyacrylamide FPY, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.2 parts of a pH adjuster (sodium hydroxide), 1 part of a fracturing fluid additive (50 wt% long-chain quaternary ammonium salt organoclay stabilizer GAF-16, Sichuan Guangya Polymer Chemical Co., Ltd. + 20 wt% of a fluorocarbon drainage aid OBS, Shanghai Futian Chemical Technology Co., Ltd. + 30 wt% of a polyepoxysuccinate sodium scale inhibitor PESA, Hebei Collaborative Chemical Co., Ltd.), 0.1 parts of a breaker (sodium persulfate), and 97.9 parts of tap water. The prepared fracturing fluid was placed in a 90°C waterbath for 4 hours to produce a thoroughly broken fluid.

[0068] Example 2:

[0069] Compared with the comparative example, the difference is that an anti-emulsification viscosity reducer is added to the fracturing fluid system.

[0070] A fracturing fluid was prepared using tap water: 0.8 parts of an emulsion thickener (salt-resistant polyacrylamide FPY, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.3 parts of an anti-emulsification viscosity reducer (30% triphenyl vinylphenol polyether (m=12, n=5) + 10% didodecyl polyether sulfonate (m=15, n=20) + 15% oleic acid diethanolamide + 5% ethylene glycol + 50% pure water), 1 part of a fracturing fluid additive (50 wt% long-chain quaternary ammonium salt organic clay stabilizer GAF-16, Sichuan Guangya Polymer Chemical Co., Ltd. + 50 wt% sodium polyepoxysuccinate scale inhibitor PESA, Hebei Collaborative Chemical Co., Ltd.), 0.1 parts of a gel breaker (sodium persulfate), and 97.8 parts of tap water. The prepared fracturing fluid was placed in a 90°C water bath for 4 hours to obtain a completely broken gel fluid.

[0071] Example 3:

[0072] Compared with the comparative example, the difference is that an alkaline pH regulator and an anti-emulsification viscosity reducer are added to the fracturing fluid system.

[0073] A fracturing fluid was prepared using tap water: 0.8 parts of an emulsion thickener (salt-resistant polyacrylamide FPY, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.15 parts of a pH adjuster (sodium hydroxide), 0.3 parts of an anti-emulsification and viscosity reducer (30% triphenyl vinylphenol polyether (m=12, n=5) + 10% didodecanol polyether sulfonate (m=15, n=20) + 15% oleic acid diethanolamide + 5% ethylene glycol + 40% pure water), 1 part of a fracturing fluid additive (50 wt% of a long-chain quaternary ammonium salt organic clay stabilizer GAF-16, Sichuan Guangya Polymer Chemical Co., Ltd. + 50 wt% of a polyepoxysuccinate sodium scale inhibitor PESA, Hebei Collaborative Chemical Co., Ltd.), 0.1 parts of a gel breaker (sodium persulfate), and 96.5 parts of tap water. The prepared fracturing fluid was placed in a 90°C water bath for 4 hours to obtain a completely broken gel fluid.

[0074] Example 4:

[0075] Compared with the comparative example, the difference is that an alkaline pH regulator and an anti-emulsification and viscosity reducing agent are added to the fracturing fluid system. Compared with Example 3, the composition of the anti-emulsification and viscosity reducing agent is different.

[0076] A fracturing fluid was prepared using tap water: 0.8 parts of an emulsion thickener (salt-resistant polyacrylamide FPY, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.15 parts of a pH adjuster (sodium hydroxide), 0.3 parts of an anti-emulsification and viscosity reducer (40% triphenyl vinylphenol polyether (m=12, n=5) + 15% oleic acid diethanolamide + 5% ethylene glycol + 40% pure water), 1 part of a fracturing fluid additive (50 wt% of a long-chain quaternary ammonium salt organic clay stabilizer GAF-16, Sichuan Guangya Polymer Chemical Co., Ltd. + 50 wt% of a polyepoxysuccinate sodium scale inhibitor PESA, Hebei Collaborative Chemical Co., Ltd.), 0.1 parts of a gel breaker (sodium persulfate), and 96.5 parts of tap water. The prepared fracturing fluid was placed in a 90°C waterbath for 4 hours to obtain a thoroughly broken fluid.

[0077] Example 5:

[0078] Compared with the comparative example, the difference is that an alkaline pH regulator and an anti-emulsification and viscosity reducer are added to the fracturing fluid system. Compared with Example 3, the composition and amount of the anti-emulsification and viscosity reducer are different.

[0079] A fracturing fluid was prepared using tap water: 0.8 parts of an emulsion thickener (salt-resistant polyacrylamide FPY, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.15 parts of a pH adjuster (sodium hydroxide), 0.25 parts of an anti-emulsification and viscosity reducer (40% triphenyl vinylphenol polyether (m=12, n=5) + 15% didodecanol polyether sulfonate (m=15, n=20) + 5% ethylene glycol + 40% pure water), 1 part of a fracturing fluid additive (50 wt% of a long-chain quaternary ammonium salt organic clay stabilizer GAF-16, Sichuan Guangya Polymer Chemical Co., Ltd. + 50 wt% of a polyepoxysuccinate sodium scale inhibitor PESA, Hebei Collaborative Chemical Co., Ltd.), 0.1 parts of a gel breaker (sodium persulfate), and 97.7 parts of tap water. The prepared fracturing fluid was placed in a 90°C water bath for 4 hours to obtain a completely broken gel fluid.

[0080] Example 6:

[0081] Compared with the comparative example, the difference is that an alkaline pH regulator and an anti-emulsification and viscosity reducer are added to the fracturing fluid system. Compared with Example 3, the composition and amount of the anti-emulsification and viscosity reducer are different.

[0082] A fracturing fluid was prepared using tap water: 0.8 parts of an emulsion thickener (salt-resistant polyacrylamide FPY, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.15 parts of a pH adjuster (sodium hydroxide), 0.25 parts of an anti-emulsification and viscosity reducer (35% triphenyl vinylphenol polyether (m=15, n=8) + 5% ditetradecyl polyether sulfonate (m=18, n=15) + 15% palmitic acid diethanolamide + 5% ethylene glycol + 40% pure water), 1 part of a fracturing fluid additive (50 wt% of a long-chain quaternary ammonium salt organic clay stabilizer GAF-16, Sichuan Guangya Polymer Chemical Co., Ltd. + 50 wt% of a polyepoxysuccinate sodium scale inhibitor PESA, Hebei Collaborative Chemical Co., Ltd.), 0.1 parts of a gel breaker (sodium persulfate), and 97.7 parts of tap water. The prepared fracturing fluid was placed in a 90°C water bath for 4 hours to obtain a completely broken fluid.

[0083] Example 7:

[0084] Compared with the comparative example, the difference is that an alkaline pH regulator and an anti-emulsification and viscosity reducer are added to the fracturing fluid system. Compared with Example 3, the composition and amount of the anti-emulsification and viscosity reducer are different.

[0085] A fracturing fluid was prepared using tap water: 0.8 parts of an emulsion thickener (salt-resistant polyacrylamide FPY, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.2 parts of a pH adjuster (sodium hydroxide), 0.3 parts of an anti-emulsification and viscosity reducer (25% triphenyl vinylphenol polyether (m=18, n=10) + 15% distearyl polyether sulfonate (m=5, n=20) + 15% lauric acid diethanolamide + 5% ethylene glycol + 40% pure water), 1 part of a fracturing fluid additive (50 wt% of a long-chain quaternary ammonium salt organic clay stabilizer GAF-16, Sichuan Guangya Polymer Chemical Co., Ltd. + 50 wt% of a polyepoxysuccinate sodium scale inhibitor PESA, Hebei Collaborative Chemical Co., Ltd.), 0.1 parts of a gel breaker (sodium persulfate), and 97.6 parts of tap water. The prepared fracturing fluid was placed in a 90°C water bath for 4 hours to obtain a completely broken gel fluid.

[0086] Example 8:

[0087] Compared with Example 7, the water quality of the preparation liquid is different, which is 10000 mg / L sodium chloride.

[0088] A fracturing fluid was prepared using 10,000 mg / L sodium chloride: 1 part emulsion thickener (salt-resistant polyacrylamide FPY, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.25 part pH adjuster (sodium hydroxide), 0.35 part anti-emulsification and viscosity reducer (30% triphenyl vinylphenol polyether (m=18, n=10) + 15% didodecanol polyether sulfonate (m=5, n=20) + 15% coconut oil diethanolamide + 5% ethylene glycol + 35% pure water), 1 part fracturing fluid additive (50 wt% long-chain quaternary ammonium salt organic clay stabilizer GAF-16, Sichuan Guangya Polymer Chemical Co., Ltd. + 50 wt% polyepoxy succinate sodium scale inhibitor PESA, Hebei Collaborative Chemical Co., Ltd.), 0.12 part gel breaker (sodium persulfate), and 97.8 parts tap water. The prepared fracturing fluid was placed in a 90°C water bath for 4 hours to obtain a completely broken gel fluid.

[0089] Example 9:

[0090] Compared with Example 7, the water quality of the preparation liquid is different, which is 30000 mg / L sodium chloride.

[0091] A fracturing fluid was prepared using 30,000 mg / L sodium chloride: 1.2 parts of an emulsion thickener (salt-resistant polyacrylamide FPY, Sichuan Guangya Polymer Chemical Co., Ltd.), 0.2 parts of a pH adjuster (sodium hydroxide), 0.3 parts of an anti-emulsification and viscosity reducer (35% triphenyl vinylphenol polyether (m=18, n=10) + 10% distearyl polyether sulfonate (m=5, n=20) + 20% lauric acid diethanolamide + 5% ethylene glycol + 40% pure water), 1 part of a fracturing fluid additive (50 wt% long-chain quaternary ammonium salt organic clay stabilizer GAF-16, Sichuan Guangya Polymer Chemical Co., Ltd. + 50 wt% sodium polyepoxysuccinate scale inhibitor PESA, Hebei Collaborative Chemical Co., Ltd.), 0.12 parts of a gel breaker (sodium persulfate), and 97.18 parts of tap water. The prepared fracturing fluid was placed in a 90°C water bath for 4 hours to obtain a completely broken gel fluid.

[0092] Effect example:

[0093] Crude oil from a block of the Jimsar Oilfield was used as the oil for this experiment (viscosity 132.4 mPa·s at 80°C). The mixture-free fracturing fluid was prepared according to the method for preparing the fracturing fluid provided by the present invention. The emulsification rate and demulsification rate test methods described in the petroleum and natural gas industry standard SY / T5107-2005 "Method for evaluating the performance of water-based fracturing fluids" of the People's Republic of China were then used to conduct the test and the viscosity of the emulsion was tested.

[0094] The specific steps are as follows:

[0095] (1) Demulsification test: First, mix the crude oil and fracturing fluid degelling liquid in a volume ratio of 3:1, put them into a container and place it in a constant temperature water bath, and heat it to 80℃. Place the constant temperature mixed liquid in a mixer, adjust the speed to an appropriate level, stir for 5 minutes, then pour the emulsion into a stoppered graduated colorimetric tube and record the actual volume of the emulsion. Place the stoppered graduated colorimetric tube containing the emulsion in an 80℃ oven, and record the volume of the degelling liquid separated at 3min, 5min, 10min, 15min, 30min, 60min, 2h, 4h, 10h, and 24h, respectively, to calculate the demulsification rate.

[0096] (2) Viscosity test: The viscosity of the crude oil emulsion was tested using a Brookfield DV-III viscometer (0# rotor, 6RPM, 80°C). First, 4 mL of the above-mentioned fracturing fluid system debonding liquid was weighed and placed into the viscometer measuring cup. Then, 12 mL of crude oil was weighed and placed into the measuring cup. After preheating for 30 minutes, a handheld emulsifier was used to emulsify and disperse the oil for 10 minutes to test the viscosity of the emulsion.

[0097] The specific experimental results are shown in Table 1 and Table 2:

[0098] Table 1 Comparison of demulsification performance in different implementation cases

[0099]

[0100] As can be seen from the comparative results of the embodiments in Table 1, the comparative example (without adding an anti-emulsification viscosity reducer) and Example 1 (adding alkali, without an anti-emulsification viscosity reducer) do not demulsify; in the anti-emulsification systems of Examples 4 and 5, no Guerbet alcohol polyether sulfonate and alkylolamide surfactant were added, respectively, and their demulsification effects were compared with those of Examples 3 and 6-9, with a demulsification rate of less than 80%, and a low demulsification rate. As can be seen from Examples 3 and 6-9, by appropriately adding an alkaline substance and the composite anti-emulsification viscosity reducer to the fracturing fluid system, under the combined action of the alkali effect and the anti-emulsification viscosity reduction to form and regulate the new oil-water interface, an anti-emulsification viscosity reduction and mixing-free fracturing fluid system is constructed, which has good demulsification performance in tap water to 30,000 mg / L brine (24h demulsification rate reaches 100%, 3min demulsification rate is greater than 85%), achieving anti-emulsification function and meeting oilfield production needs.

[0101] Table 2 Comparison of viscosity reduction performance of different implementation cases (80°C, crude oil viscosity: 132.4 mPa.s)

[0102]

[0103] As can be seen from the comparison in Table 2, the crude oil viscosity increased by about 2.3 times in the control example without the addition of the anti-emulsification viscosity reducer, while the anti-emulsification viscosity reducing water-based fracturing fluid system (Implementation Case 6-Example 9) can reduce the crude oil viscosity to about 20 mPa.s, with a viscosity reduction rate of more than 80%.

[0104] The above detailed description is a specific description of one feasible embodiment of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. An anti-emulsification viscosity reducer, characterized in that: The invention comprises the following components: sodium triphenyl vinyl phenol polyoxyethylene / propylene block polyether sulfonate, sodium Guerbet alcohol polyoxyethylene / propylene block polyether sulfonate, long-chain alkyl alcohol amide and solvent; The triphenylvinylphenol polyoxyethylene / propylene block polyether sulfonate has a molecular structure as shown in formula (I): Wherein, in the structure of formula (I), the number of ethylene oxide EO is m=12-18, and the number of propylene oxide PO is n=5-10; The molecular structure of the Guerbet alcohol-based polyoxyethylene / propylene block polyether sulfonate is shown in Formula (II): Wherein, in the structure of formula (II), R1 and R2 are long carbon chain alkyl groups, the number of carbon atoms in the main chain of R1 is 12-18, the number of carbon atoms in the main chain of R2 is 12-18, the number of ethylene oxide groups is: m=5-18, and the number of propylene oxide groups is: n=15-20; The molecular structure of the long-chain alkyl alcohol amide is shown in formula (III): Wherein, in the structure of formula (III), R is a long carbon chain alkyl group, and the number of carbon atoms in the main chain of R is 4-20.

2. The anti-emulsification viscosity reducer according to claim 1, characterized in that The solvent is any one or more of water, ethanol, ethylene glycol and glycerol.

3. The anti-emulsification viscosity reducer according to claim 1, characterized in that The number of carbon atoms in the R main chain of the long-chain alkyl alcohol amide is 12-18.

4. A method for preparing the anti-emulsification viscosity reducer according to any one of claims 1 to 3, comprising the following steps: The method comprises mixing triphenyl vinyl phenol polyoxyethylene / propylene block polyether sulfonate sodium, Guerbet alcohol polyoxyethylene / propylene block polyether sulfonate sodium, long-chain alkyl alcohol amide and solvent.

5. Use of the anti-emulsification viscosity reducer according to any one of claims 1 to 3 in fracturing fluid.

6. A water-based fracturing fluid comprising the following components: an emulsion thickener, the anti-emulsification viscosity reducer according to any one of claims 1 to 3, a pH regulator, a gel breaker, and water.

7. The water-based fracturing fluid according to claim 6, wherein The mineralization of water is 0-30000 mg / L.

8. The water-based fracturing fluid according to claim 6, wherein Calculated by weight percentage, the fracturing fluid system includes: 0.01-1.5% emulsion thickener, 0.1-0.5% anti-emulsification viscosity reducer, 0.002-0.3% pH regulator, and 0.01-0.3% gel breaker.

9. The water-based fracturing fluid according to claim 6, wherein Calculated by weight percentage, the fracturing fluid system further comprises: 0.2-1.5% of a fracturing fluid additive.

10. The water-based fracturing fluid according to claim 6, wherein Calculated by weight percentage, the fracturing fluid system further comprises: 0.5-1.2% of a fracturing fluid additive.

11. The water-based fracturing fluid according to claim 6, wherein Calculated by weight percentage, the emulsion thickener comprises: 40-55% thickener, 40-45% mineral oil, 2-5% nonionic surfactant emulsifier, 0.5-1% suspension stabilizer and 5-10% low-carbon alcohol nonionic wetting agent.

12. The water-based fracturing fluid according to claim 11, wherein The thickener is selected from any one or more of ultra-high molecular weight polyacrylamide, copolymers of acrylamide and temperature-resistant and salt-resistant monomers, hydrophobic associating polymers, comb-type polyacrylamide copolymers, star-type polyacrylamide copolymers and micro-branched polyacrylamide copolymers.

13. The water-based fracturing fluid according to claim 6, wherein The pH regulator is an organic base or an inorganic base; the organic base includes any one or more of ethanolamine, diethanolamine, triethanolamine, sodium methoxide, sodium ethoxide and potassium ethoxide; The inorganic base includes any one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate and sodium silicate.

14. The water-based fracturing fluid according to claim 6, wherein The breaker includes any one or more of ammonium persulfate, potassium persulfate, sodium persulfate, capsule breaker and oxidation-reduction breaker.

15. The water-based fracturing fluid according to claim 9 or 10, characterized in that: The fracturing fluid additive is selected from any one or more of a long-chain alkyl quaternary ammonium salt type clay stabilizer, polyepoxysuccinic acid and polyepoxy sodium succinate alkaline scale inhibitor.

16. A method for preparing a water-based fracturing fluid indoors according to any one of claims 6 to 15, comprising the following steps: (1) Add water, emulsion thickener, and pH adjuster in proportion and stir; (2) Adding an anti-emulsifier and a fracturing fluid additive at the same time and stirring, thereby obtaining an anti-emulsification polymer fracturing fluid system.

17. A method for preparing a water-based fracturing fluid on site according to any one of claims 6 to 15, comprising the following steps: According to the proportion, water, emulsion thickener, pH regulator, anti-emulsifier and fracturing fluid additive are pumped into the sand mixing tank at the same time for mixing to obtain the anti-emulsification polymer fracturing fluid system.

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