Gel breaker for well completion, preparation method and application

Abstract

The invention provides a gel breaker for well completion as well as a preparation method and application of the gel breaker. The invention provides a gel breaker for well completion. The gel breaker is prepared from the following raw materials: a polylactic acid activator, lactase and a pre-gel-breaking solution, the pre-gel breaking liquid comprises amylase, cellulase, pectinase, xylanase, catalase and polylactic acid particles. The preparation method of the gel breaker comprises the following step: mixing the polylactic acid activator, the lactase and the pre-gel-breaking liquid to obtain the gel breaker. According to the gel breaker for well completion, multiple biological enzymes such as amylase, cellulase, pectinase, xylanase and catalase are used in cooperation, the degradation effect of a natural polymer, a synthetic polymer and in-situ crude oil is greatly improved, and particularly, catalase has the combined effect of enzymolysis and oxidative degradation at the same time; due to the addition of the additive, the degradation rate of natural polymers, the degradation rate of synthetic polymers and the degradation rate of in-situ crude oil are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of completion fluid in oilfield development, and particularly relates to a gel breaker for completion, a preparation method and application. BACKGROUND

[0002] In the process of oil and gas exploration and development, especially in the process of entering into the oil and gas reservoir, the solid particles and polymers in the drilling fluid will enter into the pores near the wellbore, thereby causing the plugging of pore throat in the later development process, and making it difficult for the oil in the formation to enter into the wellbore. Therefore, after drilling, it is generally necessary to drill into the completion fluid to slow down the plugging. The general completion fluid is any liquid contacting the production layer used due to the operation needs from the drilling of the new well to the formal production. The conventional completion fluid is the fluid involved in the preliminary unblocking of the plugging caused by the drilling between the drilling and the completion. The conventional completion fluid is clean brine, such as the brine prepared by using inorganic salts such as NaCl, KCl, CaCl2, or the organic brine prepared by using NaCOOH, KCOOH, CsCOOH, etc. Since 2000, people have begun to introduce biological enzymes into the completion fluid. Li Haibin et al. (Drilling Fluid and Completion Fluid, 2009, 26(4): 1-3.) studied the degradation process of biological enzymes on starch. Subsequently, Lan Qiang et al. (Drilling Fluid and Completion Fluid, 2010, 27(1): 11-13.) began to use amylase F, cellulase C, saccharifying enzyme and complex enzyme in 2010, which can promote the degradation of the commonly used polymer polyacrylamide. Yang Qianyun et al. (Patent document application No. 201110449989.0) proposed a biological enzyme solid-free completion fluid in 2011. The system contains oil biological enzyme degradable drilling fluid filtrate reducer, biological enzyme degradable tackifier and biological enzyme. This system is more accurately defined as a reservoir drilling fluid, wherein the biological enzyme includes cellulase, amylase and complex enzyme. Subsequently, Qu Zhan et al. (Patent document application No. 201010118986.4) formally proposed a biological enzyme completion fluid in 2013. The biological enzyme used includes protease, hemicellulase, NOWEE complex enzyme, trehalose lipid and BOVEE biological active substance, which is combined with biological acid, acetic acid and metal chelating agent to form a biological enzyme completion fluid system. The system can partially remove organic scale and inorganic precipitate and degrade polymers.

[0003] In summary, the commonly used completion fluid at present is simple inorganic brine and organic brine. The biological completion fluid proposed later adds conventional biological enzymes, which can remove part of the plugging in combination with part of the acid liquid. However, such enzymes are only suitable for removing cellulose and protein polymers, and have poor effect on synthetic polymers. Moreover, the biological acid and acetic acid have weak acidity, and the chelating agent has poor effect on the difficultly soluble barite. Therefore, it is necessary to develop a new completion fluid system with temperature resistance and high solid phase corrosion. SUMMARY

[0004] To solve the above problems in the prior art, the present application provides a breaker for well completion, a preparation method and application thereof.

[0005] In a first aspect, the present application provides a breaker for well completion, raw materials of the breaker comprising: polylactic acid activator, lactase and pre-breaker solution; the pre-breaker solution comprising: amylase, cellulase, pectinase, xylanase, catalase, polylactic acid particles and organic acid chelating agent.

[0006] As a specific embodiment of the present application, the raw materials of the breaker for well completion comprise, in terms of mass fraction: 1-3 parts of polylactic acid activator and 30-50 parts of lactase; the mass-volume ratio of the polylactic acid activator to the pre-breaker solution is 0.05-0.3 kg / m 3 , preferably 0.1-0.15 kg / m 3 ; the mass-volume ratio of the lactase to the pre-breaker solution is 1.5-5 kg / m 3 , preferably 2.5-3 kg / m 3 .

[0007] As a specific embodiment of the present application, the pre-breaker solution comprises, in terms of mass fraction: 200-500 parts of amylase, 200-500 parts of cellulase, 100-300 parts of pectinase, 100-300 parts of xylanase, 500-800 parts of catalase, 300-500 parts of polylactic acid particles, 100-300 parts of organic acid chelating agent and 6000-8000 parts of solvent. The solvent is preferably water or alcohol.

[0008] As a specific embodiment of the present application, the polylactic acid activator is lipase.

[0009] Preferably, the polylactic acid activator is one or both of phosphodiesterase and sterolase.

[0010] As a specific embodiment of the present application, the lactase is β-galactosidase.

[0011] As a specific embodiment of the present application, the amylase is α-amylase.

[0012] As a specific embodiment of the present application, the cellulase is β-1,4-glucan-4-glucan hydrolase.

[0013] As a specific embodiment of the present application, the pectinase is pectinesterase.

[0014] As a specific embodiment of the present application, the xylanase is heteropolysaccharide.

[0015] As a specific embodiment of the present application, the catalase is hemoglobinase.

[0016] As a specific embodiment of the present application, the molecular weight of the polylactic acid particles is 30000-50000, and the particle size is 300-500 μm. The polylactic acid particles are formed by dehydration polymerization of multiple lactic acid molecules, and are also referred to as polylactide.

[0017] As a specific embodiment of the present application, the organic acid chelating agent is one or more of sugar acid, amino phosphoric acid, citric acid, ethylenediaminetetraacetic acid, aminotriacetic acid, and diethylenetriamine pentaacetic acid.

[0018] As a specific embodiment of the present application, the alcohol has 2-5 carbon atoms; preferably, the alcohol is one or more of propanol, propylene glycol, glycerol, and ethylene glycol.

[0019] As a specific embodiment of the present application, the water is deionized water.

[0020] In a second aspect, the present application provides a preparation method of the breaker provided in the first aspect of the present application. The preparation method comprises the following steps: mixing a polylactic acid activator, lactase, and a pre-breaker solution I to obtain the breaker.

[0021] As a specific embodiment of the present application, the mixing I is stirring mixing, the stirring speed is 100 rpm-300 rpm, and the stirring time is 60-120 min.

[0022] As a specific embodiment of the present application, the preparation method of the pre-breaker solution comprises the following steps:

[0023] Mixing II of a solvent, amylase, cellulase, pectinase, xylanase, catalase, and polylactic acid particles to obtain the pre-breaker solution; preferably, the solvent is water and / or alcohol.

[0024] Preferably, the mixing II comprises: (1) stirring mixing a of alcohol and water to obtain a mixing solution A;

[0025] Preferably, the stirring speed of the mixing a is 100-300 rpm, and the time is 30-60 min;

[0026] (2) stirring mixing b of the mixing solution A with amylase, cellulase, pectinase, and xylanase to obtain a mixing solution B;

[0027] Preferably, the stirring speed of the mixing b is 300 rpm-600 rpm, the time is 30-60 min, and the temperature is 40-60°C;

[0028] (3) stirring mixing c of the mixing solution B with catalase to obtain a mixing solution C;

[0029] Preferably, the stirring speed of the mixing c is 300 rpm-600 rpm, the time is 30-60 min, and the temperature is 40-60°C;

[0030] (4) mixing the mixed solution C with polylactic acid particles to obtain a mixed solution D;

[0031] Preferably, the mixing d is at a stirring speed of 300 rpm to 600 rpm, a temperature of 40 to 60°C, and a time of 30 to 50 min.

[0032] (5) mixing the mixed solution D with an organic acid chelating agent to obtain a mixed solution E, adjusting the pH value of the mixed solution E to 3.0 to 5.0 to obtain a pre-gel breaking solution;

[0033] Preferably, the mixing e is at a stirring speed of 300 rpm to 600 rpm, a temperature of 40 to 60°C, and a time of 30 to 50 min.

[0034] Specifically, the pH of the mixed solution E is adjusted by a buffer solution, and the buffer solution is HAc-NaAc buffer solution composed of 0.1 mol / l HAc and 0.1 mol / l NaAc.

[0035] As a specific embodiment of the present application, the polylactic acid activator is lipase.

[0036] Preferably, the polylactic acid activator is one or both of phosphodiesterase and sterolase.

[0037] As a specific embodiment of the present application, the lactase is β-galactosidase.

[0038] As a specific embodiment of the present application, the amylase is α-amylase.

[0039] As a specific embodiment of the present application, the cellulase is β-1, 4-glucan-4-glucan hydrolase.

[0040] As a specific embodiment of the present application, the pectinase is pectinesterase.

[0041] As a specific embodiment of the present application, the xylanase is heteroglycan.

[0042] As a specific embodiment of the present application, the catalase is hemoglobinase.

[0043] As a specific embodiment of the present application, the polylactic acid particles have a molecular weight of 30,000 to 50,000 and a particle size of 300 to 500 μm. The polylactic acid particles are formed by dehydration and polymerization of multiple lactic acid molecules, and are also called polylactide.

[0044] As a specific embodiment of the present application, the organic acid chelating agent is one or more of sugar acid, amino phosphoric acid, citric acid, ethylenediaminetetraacetic acid, aminotriacetic acid, and diethylenetriamine pentaacetic acid.

[0045] As a specific embodiment of the present application, the number of carbon atoms of the alcohol is 2-5; preferably, the alcohol is selected from one or more of propanol, propylene glycol, glycerol, and ethylene glycol.

[0046] As a specific embodiment of the present application, the water is deionized water.

[0047] As a specific embodiment of the present application, the concentration of amylase in the pre-gel breaking solution is 27-72 g / L;

[0048] As a specific embodiment of the present application, the concentration of cellulase in the pre-gel breaking solution is 27-72 g / L;

[0049] As a specific embodiment of the present application, the concentration of pectinase in the pre-gel breaking solution is 14-43 g / L;

[0050] As a specific embodiment of the present application, the concentration of xylanase in the pre-gel breaking solution is 14-43 g / L;

[0051] As a specific embodiment of the present application, the concentration of catalase in the pre-gel breaking solution is 71-115 g / L;

[0052] As a specific embodiment of the present application, the concentration of polylactic acid particles in the pre-gel breaking solution is 42-72 g / L;

[0053] As a specific embodiment of the present application, the concentration of organic acid chelating agent in the pre-gel breaking solution is 14-43 g / L.

[0054] In a third aspect, the present application provides a use method of the gel breaker provided in the first aspect of the present application or the gel breaker prepared by the preparation method provided in the second aspect of the present application, wherein, after the drilling string is pulled out and the well is washed, clean brine is pumped into the well, and then the gel breaker is sent to the reservoir section to perform a shut-in reaction.

[0055] As a specific embodiment of the present application, the conditions of the shut-in reaction include a time of 24-36 h and a pressure of 3.0-6.0 MPa.

[0056] Specifically, the use method of the gel breaker for well completion is as follows:

[0057] 1) After the drilling string is pulled out and the well is washed at a large flow rate, 5 m 3 The clean brine is pumped into the well as a preflush;

[0058] 2) The prepared gel breaker for well completion is pumped into the reservoir section;

[0059] 3) The well is shut in, the ground is pressurized to 3.0 MPa, and the action lasts for 24 h;

[0060] 4) Circulation is restored, and the well bottom is flushed at a large flow rate with fine-filtered formation water until the returned fluid is no longer turbid.

[0061] 5) Proceed to next step for other completion operation.

[0062] The clean brine is a brine containing 2.0wt% NaCl and 1.0wt% KCl.

[0063] The fine-filtered formation water is a liquid obtained after oil and impurities are removed from the oil well return fluid and the liquid is filtered multiple times, wherein the solid content is less than 0.5% and the solid particle size is less than 1.0um.

[0064] Compared with the prior art, the application has the following beneficial effects.

[0065] (1) In the completion breaker of the application, multiple biological enzymes such as amylase, cellulase, pectinase, xylanase and catalase are used in combination, which greatly improves the degradation of natural polymers, synthetic polymers and formation crude oil. In particular, catalase has both enzymatic degradation and oxidative degradation, and its addition greatly improves the degradation rates of natural polymers, synthetic polymers and formation crude oil.

[0066] (2) In the completion breaker of the application, polylactic acid particles are introduced, which dissociate hydrogen ions during degradation under high temperature conditions at the bottom of the well, thereby improving the dissolution of inorganic solids. In addition, organic acid chelating agents are also introduced, which further improve the dissolution of barite and other insoluble solids. The combination of polylactic acid particles and organic acid chelating agents improves the dissolution of barite by 26%.

[0067] (3) The completion breaker of the application also includes polylactic acid activators and lactase, which significantly promote the degradation of polylactic acid, thereby further improving the ability of the breaker to remove inorganic solids.

[0068] (4) The temperature resistance of the completion breaker of the application can reach 150℃, and the overall plugging removal rate is improved by more than 30%. DETAILED DESCRIPTION

[0069] The application will be further described below in conjunction with specific examples, but it does not constitute any limitation on the application.

[0070] The raw materials used in each embodiment of the application are all commercially available.

[0071] The alpha-amylase and beta-1,4-glucan-4-glucan hydrolase are purchased from Hunan Yunbang Biology;

[0072] The pectinesterase is purchased from Hunan Yunbang Biology;

[0073] The heteropolysaccharide is purchased from Hunan Yunbang Biology;

[0074] Hemoglobinase was purchased from Xiasheng (Beijing) Biotechnology Development Co., Ltd.;

[0075] Polylactic acid particles were purchased from Shanghai Chaoqi Plasticizing Co., Ltd., with a molecular weight of 30,000-50,000 and a particle size of 300-500 μm;

[0076] Phosphodiesterase was purchased from Shanghai Kepuori Biotechnology Co., Ltd.;

[0077] Sterolase was purchased from Xi'an Darwen Biotechnology Co., Ltd.;

[0078] β-galactosidase was purchased from Sichuan Huatang Juerui Biotechnology Co., Ltd.;

[0079] Sugar acid was purchased from Sichuan Huanyuan Shengtai Biotechnology Co., Ltd.;

[0080] Amino phosphoric acid was purchased from Jinan Xingchen Biotechnology Co., Ltd.;

[0081] Citric acid was purchased from Wujiang Chengyue Fine Chemical Co., Ltd.;

[0082] Ethylene diamine tetraacetic acid was purchased from Jinan Delan Chemical Co., Ltd.;

[0083] Amino triacetic acid was purchased from Shanghai Yuli Industry Co., Ltd.;

[0084] Diethylene triamine pentaacetic acid was purchased from Guangzhou Yin Chang Trade Co., Ltd.

[0085] Example 1

[0086] Preparation of pre-gel breaking liquid: 1) 2 L of propanol and 5 L of deionized water were sequentially added to a 10 L reactor, the stirring speed was set to 100 rpm, and the mutual solubilization reaction was performed for 30 min; 2) 200 g of α-amylase, 200 g of β-1, 4-glucan-4-glucan hydrolase, 100 g of pectin esterase, and 100 g of heterogeneous polysaccharide were sequentially added to the above reactor, the stirring speed was increased to 300 rpm, the temperature was increased to 40℃, and stirring was performed for 30 min; 3) 500 g of hemoglobinase was added to the above reactor, the stirring speed was maintained at 300 rpm, the temperature was maintained at 40℃, and stirring was performed for 30 min; 4) 300 g of polylactic acid particles were added to the above reactor, the reaction temperature and stirring speed were maintained, and the reaction was continued for 30 min; 5) 100 g of sugar acid was added to the above reactor, the reaction temperature and stirring speed were maintained, and the reaction was continued for 30 min; 6) HAc-NaAc buffer was added to the above reactor, the reaction temperature and stirring speed were maintained, the pH of the system was controlled at 3.0, and the system was the pre-gel breaking liquid.

[0087] Preparation of gel breaking agent for well completion: 1) a 30 m3 a 10 m 3 pre-gel breaking solution; 2) 1 kg of phosphodiesterase and 30 kg of β-galactosidase were added to the above preparation tank, and the system was stirred at a low speed of 100 rpm for 60 min, and the obtained system was a gel breaker for well completion.

[0088] Example 2

[0089] Preparation of the pre-gel breaking solution: 1) 2 L of propylene glycol and 5 L of deionized water were sequentially added to a 10 L reactor, and the stirring speed was set to 200 rpm, and the mutual solubilization reaction was performed for 30 min; 2) 300 g of α-amylase, 300 g of β-1, 4-glucan-4-glucan hydrolase, 200 g of pectinesterase, and 200 g of heteropolysaccharide were sequentially added to the above reactor, the stirring speed was increased to 400 rpm, and the temperature was increased to 50 °C, and the system was stirred for 40 min; 3) 600 g of hemoglobinase was added to the above reactor, and the stirring speed and temperature were maintained at 400 rpm and 50 °C, respectively, and the system was stirred for 40 min; 4) 400 g of polylactic acid particles were added to the above reactor, and the stirring speed and temperature were maintained, and the system was continuously reacted for 40 min; 5) 100 g of amino phosphoric acid was added to the above reactor, and the stirring speed and temperature were maintained, and the system was continuously reacted for 40 min; 6) HAc-NaAc buffer was added to the above reactor, the stirring speed and temperature were maintained, the pH of the system was controlled at 4.0, and the system was a pre-gel breaking solution.

[0090] Preparation of the gel breaker for well completion: 1) a 30 m 3 preparation tank was prepared at the well site, and 20 m 3 of the pre-gel breaking solution was added to the preparation tank; 2) 2 kg of sterolase and 30 kg of β-galactosidase were added to the above preparation tank, and the system was stirred at a low speed of 200 rpm for 60 min, and the obtained system was a gel breaker for well completion.

[0091] Example 3

[0092] Preparation of the pre-gel breaking liquid: 1) 2 L of glycerol and 5 L of deionized water were sequentially added into a 10 L reactor, and the stirring speed was set to 300 rpm, and the mutual solubilization reaction was performed for 30 min; 2) 400 g of α-amylase, 300 g of β-1, 4-glucan-4-glucan hydrolase, 300 g of pectinesterase, and 300 g of heteropolysaccharide were sequentially added into the above reactor, the stirring speed was increased to 500 rpm, the temperature was increased to 60 ℃, and stirring was performed for 50 min; 3) 700 g of hemoglobinase was added into the above reactor, the stirring speed was continuously maintained at 500 rpm, the temperature was continuously maintained at 60 ℃, and stirring was continuously performed for 50 min; 4) 500 g of polylactic acid particles were added into the above reactor, the reaction temperature and the stirring speed were maintained unchanged, and the reaction was continuously performed for 50 min; 5) 100 g of citric acid was added into the above reactor, the reaction temperature and the stirring speed were maintained unchanged, and the reaction was continuously performed for 50 min; 6) HAc-NaAc buffer was added into the above reactor, the reaction temperature and the stirring speed were maintained unchanged, and the pH of the system was controlled to be 5.0, and the system was the pre-gel breaking liquid.

[0093] Preparation of the gel breaking agent for well completion: 1) a 30 m 3 L preparation tank was prepared at a well site, 20 m 3 L of the pre-gel breaking liquid was added into the preparation tank, 3 kg of phosphodiesterase and 50 kg of β-galactosidase were added into the above preparation tank, low-speed stirring was performed at a stirring speed of 300 rpm, and stirring was performed for 60 min, and the system obtained at this time was the gel breaking agent for well completion.

[0094] Example 4

[0095] Preparation of the pre-gel breaking liquid: 1) 2 L of ethylene glycol and 5 L of deionized water were sequentially added into a 10 L reactor, and the stirring speed was set to 300 rpm, and the mutual solubilization reaction was performed for 30 min; 2) 500 g of α-amylase, 500 g of β-1, 4-glucan-4-glucan hydrolase, 300 g of pectinesterase, and 300 g of heteropolysaccharide were sequentially added into the above reactor, the stirring speed was increased to 600 rpm, the temperature was increased to 60 ℃, and stirring was performed for 60 min; 3) 800 g of hemoglobinase was added into the above reactor, the stirring speed was continuously maintained at 600 rpm, the temperature was continuously maintained at 60 ℃, and stirring was continuously performed for 60 min; 4) 500 g of polylactic acid particles were added into the above reactor, the reaction temperature and the stirring speed were maintained unchanged, and the reaction was continuously performed for 50 min; 5) 100 g of ethylenediaminetetraacetic acid was added into the above reactor, the reaction temperature and the stirring speed were maintained unchanged, and the reaction was continuously performed for 50 min; 6) HAc-NaAc buffer was added into the above reactor, the reaction temperature and the stirring speed were maintained unchanged, and the pH of the system was controlled to be 5.0, and the system was the pre-gel breaking liquid.

[0096] Preparation of the gel breaking agent for well completion: 1) a 30 m 3pre-gel breaking solution; 2) 3 kg of phosphodiesterase and 50 kg of β-galactosidase were added into the above preparation tank, and the stirring speed was set to 300 rpm, and the stirring was continued for 60 min. The system obtained at this time was the gel breaker for well completion. 3 pre-gel breaking solution; 2) 3 kg of phosphodiesterase and 50 kg of β-galactosidase were added into the above preparation tank, and the stirring speed was set to 300 rpm, and the stirring was continued for 60 min. The system obtained at this time was the gel breaker for well completion.

[0097] Example 5

[0098] pre-gel breaking solution; 2) 3 kg of phosphodiesterase and 50 kg of β-galactosidase were added into the above preparation tank, and the stirring speed was set to 300 rpm, and the stirring was continued for 60 min. The system obtained at this time was the gel breaker for well completion.

[0099] pre-gel breaking solution; 2) 3 kg of phosphodiesterase and 50 kg of β-galactosidase were added into the above preparation tank, and the stirring speed was set to 300 rpm, and the stirring was continued for 60 min. The system obtained at this time was the gel breaker for well completion. 3 pre-gel breaking solution; 2) 3 kg of phosphodiesterase and 50 kg of β-galactosidase were added into the above preparation tank, and the stirring speed was set to 300 rpm, and the stirring was continued for 60 min. The system obtained at this time was the gel breaker for well completion. 3 pre-gel breaking solution; 2) 3 kg of phosphodiesterase and 50 kg of β-galactosidase were added into the above preparation tank, and the stirring speed was set to 300 rpm, and the stirring was continued for 60 min. The system obtained at this time was the gel breaker for well completion.

[0100] Example 6

[0101] Preparation of the pre-gel breaking liquid: 1) 2 L of propylene glycol and 5 L of deionized water were sequentially added to a 10 L reactor, the stirring speed was set to 300 rpm, and mutual solubilization reaction was performed for 30 min; 2) 500 g of α-amylase, 500 g of β-1, 4-glucan-4-glucan hydrolase, 300 g of pectinesterase, and 300 g of heteropolysaccharide were sequentially added to the above reactor, the stirring speed was increased to 600 rpm, the temperature was increased to 60 °C, and stirring was performed for 40 min; 3) 800 g of hemoglobinase was added to the above reactor, the stirring speed was continuously maintained at 600 rpm, the temperature was continuously maintained at 60 °C, and stirring was continuously performed for 40 min; 4) 500 g of polylactic acid particles were added to the above reactor, the reaction temperature and the stirring speed were continuously maintained, and the reaction was continuously performed for 50 min; 5) 300 g of amino triacetate was added to the above reactor, the reaction temperature and the stirring speed were continuously maintained, and the reaction was continuously performed for 50 min; 6) HAc-NaAc buffer was added to the above reactor, the reaction temperature and the stirring speed were continuously maintained, and the pH of the system was controlled to be between 5.0, and the system was the pre-gel breaking liquid.

[0102] Preparation of the gel breaker for well completion: 1) a 30 m 3 L preparation tank was prepared at a well site, 20 m 3 L of the pre-gel breaking liquid was added to the preparation tank, 3 kg of phosphodiesterase and 50 kg of β-galactosidase were added to the above preparation tank, low-speed stirring was performed at a stirring speed of 300 rpm, and stirring was performed for 60 min, and the system obtained at this time was the gel breaker for well completion.

[0103] Example 7

[0104] Preparation of the pre-gel breaking liquid: 1) 2 L of propylene glycol and 5 L of deionized water were sequentially added to a 10 L reactor, the stirring speed was set to 300 rpm, and mutual solubilization reaction was performed for 30 min; 2) 500 g of α-amylase, 500 g of β-1, 4-glucan-4-glucan hydrolase, 300 g of pectinesterase, and 300 g of heteropolysaccharide were sequentially added to the above reactor, the stirring speed was increased to 600 rpm, the temperature was increased to 60 °C, and stirring was performed for 50 min; 3) 800 g of hemoglobinase was added to the above reactor, the stirring speed was continuously maintained at 600 rpm, the temperature was continuously maintained at 60 °C, and stirring was continuously performed for 50 min; 4) 500 g of polylactic acid particles were added to the above reactor, the reaction temperature and the stirring speed were continuously maintained, and the reaction was continuously performed for 50 min; 5) 100 g of diethylene triamine pentaacetic acid was added to the above reactor, the reaction temperature and the stirring speed were continuously maintained, and the reaction was continuously performed for 50 min; 6) HAc-NaAc buffer was added to the above reactor, the reaction temperature and the stirring speed were continuously maintained, and the pH of the system was controlled to be between 5.0, and the system was the pre-gel breaking liquid.

[0105] Preparation of the gel breaker for well completion: 1) a 30 m 3a 20 m 3 pre-gel breaking solution; 2) 3 kg of phosphodiesterase and 50 kg of β-galactosidase were added to the above preparation tank, and low-speed stirring was carried out at a stirring speed of 300 rpm for 60 min, and the obtained system was a gel breaker for well completion.

[0106] Example 8

[0107] Preparation of the pre-gel breaking solution: 1) 2 L of ethylene glycol and 5 L of deionized water were sequentially added to a 10 L reactor, a stirring speed of 300 rpm was set, and mutual solubilization reaction was carried out for 30 min; 2) 500 g of α-amylase, 500 g of β-1, 4-glucan-4-glucan hydrolase, 300 g of pectinesterase and 300 g of heteropolysaccharide were sequentially added to the above reactor, the stirring speed was increased to 600 rpm, the temperature was increased to 60°C, and stirring was carried out for 60 min; 3) 800 g of hemoglobin enzyme was added to the above reactor, the stirring speed was maintained at 600 rpm and the temperature was maintained at 60°C, and stirring was carried out for 60 min; 4) 500 g of polylactic acid particles were added to the above reactor, the reaction temperature and stirring speed were maintained, and the reaction was continued for 50 min; 5) 200 g of diethylene triamine pentaacetic acid was added to the above reactor, the reaction temperature and stirring speed were maintained, and the reaction was continued for 50 min; 6) HAc-NaAc buffer was added to the above reactor, the reaction temperature and stirring speed were maintained, the pH of the system was controlled to be between 5.0, and the system was a pre-gel breaking solution.

[0108] Preparation of the gel breaker for well completion: 1) a 30 m 3 preparation tank was prepared at the well site, 20 m 3 of the pre-gel breaking solution was added to the preparation tank; 2) 3 kg of phosphodiesterase and 50 kg of β-galactosidase were added to the above preparation tank, and low-speed stirring was carried out at a stirring speed of 300 rpm for 60 min, and the obtained system was a gel breaker for well completion.

[0109] Example 9

[0110] Preparation of the pre-gel breaking liquid: 1) 2 L of ethylene glycol and 5 L of deionized water were sequentially added to a 10 L reactor, and the stirring speed was set to 300 rpm, and the mutual solubilization reaction was performed for 30 min; 2) 500 g of α-amylase, 500 g of β-1, 4-glucan-4-glucan hydrolase, 300 g of pectin esterase, and 200 g of heteropolysaccharide were sequentially added to the above reactor, the stirring speed was increased to 600 rpm, the temperature was increased to 60 °C, and stirring was performed for 40 min; 3) 800 g of hemoglobinase was added to the above reactor, the stirring speed was maintained at 600 rpm, the temperature was maintained at 60 °C, and stirring was performed for 40 min; 4) 500 g of polylactic acid particles were added to the above reactor, the reaction temperature and stirring speed were maintained, and the reaction was continued for 50 min; 5) 200 g of amino triacetate was added to the above reactor, the reaction temperature and stirring speed were maintained, and the reaction was continued for 50 min; 6) HAc-NaAc buffer was added to the above reactor, the reaction temperature and stirring speed were maintained, the pH of the system was controlled to be between 5.0, and the system was the pre-gel breaking liquid.

[0111] Preparation of the gel breaking agent for well completion: 1) a 30 m 3 preparation tank was prepared at the well site, 20 m 3 of the pre-gel breaking liquid was added to the preparation tank, 3 kg of phosphodiesterase and 50 kg of β-galactosidase were added to the above preparation tank, low-speed stirring was performed at a stirring speed of 300 rpm, and stirring was performed for 60 min, and the system obtained at this time was the gel breaking agent for well completion.

[0112] Comparative Example 1

[0113] Preparation of the pre-gel breaking liquid: 1) 2 L of ethylene glycol and 5 L of deionized water were sequentially added to a 10 L reactor, and the stirring speed was set to 300 rpm, and the mutual solubilization reaction was performed for 30 min; 2) 500 g of α-amylase, 500 g of β-1, 4-glucan-4-glucan hydrolase, 300 g of pectin esterase, and 200 g of heteropolysaccharide were sequentially added to the above reactor, the stirring speed was increased to 600 rpm, the temperature was increased to 60 °C, and stirring was performed for 40 min; 3) 500 g of polylactic acid particles were added to the above reactor, the reaction temperature and stirring speed were maintained, and the reaction was continued for 50 min; 4) 100 g of amino triacetate was added to the above reactor, the reaction temperature and stirring speed were maintained, and the reaction was continued for 50 min; 5) HAc-NaAc buffer was added to the above reactor, the reaction temperature and stirring speed were maintained, the pH of the system was controlled to be between 5.0, and the system was the pre-gel breaking liquid.

[0114] Preparation of the gel breaking agent for well completion: 1) a 30 m 3 preparation tank was prepared at the well site, 20 m 3Pre-gel breaking liquid; 2) 3 kg phosphodiesterase and 50 kg β-galactosidase were added into the above preparation tank, and stirred at a low speed of 300 rpm for 60 min, and the obtained system was the gel breaker for well completion.

[0115] Comparative Example 2

[0116] Preparation of pre-gel breaking liquid: 1) 2 L ethylene glycol and 5 L deionized water were sequentially added into a 10 L reactor, and the stirring speed was set to 300 rpm, and the mutual solubilization reaction was performed for 30 min; 2) 500 g α-amylase, 500 g β-1, 4-glucan-4-glucan hydrolase, 300 g pectinesterase and 200 g heteropolysaccharide were sequentially added into the above reactor, the stirring speed was increased to 600 rpm, the temperature was increased to 60 ℃, and the stirring was performed for 50 min; 3) 800 g hemoglobin enzyme was added into the above reactor, the stirring speed was maintained at 600 rpm, the temperature was maintained at 60 ℃, and the stirring was performed for 50 min; 4) 500 g polylactic acid particles were added into the above reactor, the reaction temperature and the stirring speed were maintained, and the reaction was continued for 50 min; 5) 200 g amino triacetate was added into the above reactor, the reaction temperature and the stirring speed were maintained, and the reaction was continued for 50 min; 6) HAc-NaAc buffer was added into the above reactor, the reaction temperature and the stirring speed were maintained, the pH of the system was controlled to be between 5.0, and the system was the pre-gel breaking liquid.

[0117] Preparation of gel breaker for well completion: 1) a 30 m 3 L preparation tank was prepared at a well site, 20 m 3 L pre-gel breaking liquid was added into the preparation tank; 2) 50 kg β-galactosidase was added into the above preparation tank, and stirred at a low speed of 300 rpm for 60 min, and the obtained system was the gel breaker for well completion.

[0118] Comparative Example 3

[0119] Pre-gel breaking liquid preparation: 1) in a 10L reactor, add 2L ethylene glycol and 5L deionized water in turn, set the stirring speed to 300rpm, and mix for 30min; 2) in the above reactor, add 500g α-amylase, 500g β-1, 4-glucan-4-glucan hydrolase, 300g pectinesterase and 200g heteropolysaccharide in turn, increase the stirring speed to 600rpm, increase the temperature to 60℃, and stir for 60min; 3) in the above reactor, add 800g hemoglobinase, continue to maintain the stirring speed of 600rpm and the temperature of 60℃, and stir for 60min; 4) in the above reactor, add 500g polylactic acid particles, maintain the reaction temperature and stirring speed, and continue to react for 50min; 5) in the above reactor, add 300g amino triacetate, maintain the reaction temperature and stirring speed, and continue to react for 50min; 6) in the above reactor, add HAc-NaAc buffer, maintain the reaction temperature and stirring speed, control the pH of the system between 5.0, and the system is the pre-gel breaking liquid.

[0120] Preparation of gel breaker for well completion: 1) prepare a 30m 3 L preparation tank at the well site, add 20m 3 L pre-gel breaking liquid in the preparation tank, 2) add 3kg phosphodiesterase in the above preparation tank, stir at a low speed of 300rpm, and stir for 60min, and the system obtained at this time is the gel breaker for well completion.

[0121] Comparative Example 4

[0122] According to the example 7 of the Chinese patent application document with the inventor being Yang Qianyun et al. and the patent application number being 201110449989.0, a biological enzyme solid-free well completion fluid is prepared.

[0123] Comparative Example 5

[0124] According to the example 11 of the Chinese patent with the inventor being Qu Zhan et al. and the patent application number being 201010118986.4, a biological enzyme well completion fluid is prepared.

[0125] Test the performance of the gel breakers / well completion fluids prepared in examples 1-9 and comparative examples 1-5 of the present application.

[0126] (1) Natural polymer degradation rate test:

[0127] Prepare a dispersion system of 2.0wt% starch + 2.0wt% cellulose and water 500g, test the initial viscosity, then add 50mL well completion fluid / gel breaker, test the viscosity after 24h static compression at 150℃ / 3.5MPa, and compare with the initial viscosity, which is the natural polymer degradation rate.

[0128] (2) Synthetic polymer degradation rate test:

[0129] Formulate 500g of a dispersion system of 2.0wt% polyacrylamide + 2.0wt% sulfonated phenol-aldehyde resin and water, test the initial viscosity, then add 50mL of completion fluid / gel breaker, test the viscosity after 24h of static pressure at 150°C / 3.5MPa, and compare with the initial viscosity, which is the natural polymer degradation rate.

[0130] (3) Formation crude oil degradation rate test:

[0131] Select crude oil with initial viscosity of 1000mPa.s (20°C / 101.325kPa), test the initial viscosity, then add completion fluid / gel breaker, test the viscosity after 24h of static pressure at 150°C / 3.5MPa, and compare with the initial viscosity, which is the natural polymer degradation rate.

[0132] (4) Barite degradation rate test:

[0133] Select barite with density of 4.3g / cm 3 , BaSO4 content greater than 99%, 400g, test the initial mass, then add 50mL of completion fluid / gel breaker, test the mass after 24h of static pressure at 150°C / 3.5MPa, and compare with the initial mass, which is the natural polymer degradation rate.

[0134] (5) Mud cake removal rate test:

[0135] Formulate a conventional sulfonated drilling fluid: 400g tap water + 3.0wt% bentonite + 0.2wt% KPAM + 2.0wt% SMP-3 + 2.0wt% SPNH + 4.0wt% liquid solid compounded asphalt + 0.5wt% amine-based polyol + 1.0wt% high-temperature resistant filtration reducer + 2.0wt% XY-1 + 7wt% KCl + 130g barite. Test the drilling fluid performance before and after 150°C / 16h aging, and the results are shown in Table 1.

[0136] Table 1 Performance of conventional sulfonated drilling fluid

[0137]

[0138] The sulfonated drilling fluid is subjected to high temperature and high pressure filtration experiment at 150℃ / 3.5MPa, and filtration is performed for 30min. After completion, pressure is released and temperature is reduced. The mud in the tank is poured out, and the surface of the mud cake is cleaned with clean water. A plurality of sulfonated drilling fluid mud cakes with a mass of 65g are prepared by repeating the above process. The plurality of mud cakes are taken out and placed into corresponding high temperature and high pressure filtration rate testers. Then, 50mL of completion fluid / breaking agent is added to the test tank, which is set to 150℃ / 3.5MPa. The upper and lower valve rods are closed, and the pressure is maintained for 24h. The mud cake is taken out, and the remaining mud cake mass is detected and divided by the initial mud cake mass, which is the mud cake removal rate.

[0139] The test results of examples 1-9 and comparative examples 1-5 are shown in Table 2.

[0140] Table 2: Comparison of test performance of examples 1-9 and comparative examples 1-5

[0141]

[0142]

[0143] As can be seen from the results, the degradation rates of all natural polymers in the examples are above 80%, with the highest reaching 92%. The degradation rates of synthetic polymers are above 65%, with the highest reaching 75%. The degradation rates of formation crude oil are above 30%, with the highest being 53%. The degradation rates of barite are the lowest, with the lowest being 31% and the highest being 41%. The comprehensive mud cake removal rates are all above 62%, with the highest being 95%.

[0144] Compared with conventional biological completion fluids (comparative examples 4-5), the performance of the conventional biological completion fluids is poorer. The degradation rates of synthetic polymers, crude oil and barite in the conventional biological completion fluids are relatively low, and the highest comprehensive mud cake removal rate is 54%. The main reason is that the catalase in the breaking agent of the present application has both enzymatic degradation and oxidative degradation, and its addition greatly improves the degradation rates of natural polymers, synthetic polymers and formation crude oil. The introduction of polylactic acid particles in the breaking agent of the present application dissociates hydrogen ions during degradation under high temperature conditions at the bottom of the well, thereby improving the corrosion of inorganic solids. The introduction of organic acid chelating agents further improves the corrosion of barite and other insoluble solids. During the preparation of the breaking agent of the present application, the addition of polylactic acid activator and lactase when entering the wellbore significantly promotes the degradation of polylactic acid, thereby further improving the ability of the system to remove inorganic solids.

[0145] It should be noted that the foregoing examples have been provided merely for the purposes of illustration and are not intended to limit the application in any way. Descriptions and examples of materials and processes of the application are intended to be illustrative not limiting. Any modifications of the application and other applications of the application will occur to those skilled in the art to which the application pertains and many options for modification of the application will suggest themselves. The application lies in the broadest aspects of the technological concepts involved. Descriptions and examples of specific chemical materials and processes are intended to be illustrative of the application and it is intended that requests for patent protection be limited to one of the specific embodiments described above, described in the following claims, and any equivalents thereof.

Claims

1. A well completion breaker, characterized in that, The raw materials of the de-icing agent include: polylactic acid activator, lactase and pre-de-icing solution; the pre-de-icing solution includes: amylase, cellulase, pectinase, xylanase, catalase, polylactic acid particles and organic acid chelating agent.

2. The breaker according to claim 1, characterized in that, The raw materials of the de-icing agent, by weight, include: 1-3 parts polylactic acid activator and 30-50 parts lactase; the mass-to-volume ratio of the polylactic acid activator to the pre-de-icing solution is 0.05-0.3 kg / m³. 3 The preferred value is 0.1–0.15 kg / m³. 3 The mass-to-volume ratio of the lactase to the pre-broken gel solution is 1.5–5 kg / m³. 3 The preferred value is 2.5–3 kg / m³. 3 .

3. The de-gelling agent according to claim 1 or 2, characterized in that, The pre-breakage solution comprises, by weight parts: 200-500 parts amylase, 200-500 parts cellulase, 100-300 parts pectinase, 100-300 parts xylanase, 500-800 parts catalase, 300-500 parts polylactic acid granules, 100-300 parts organic acid chelating agent, and 6000-8000 parts solvent, wherein the solvent is preferably water / or alcohol.

4. The breaker according to any one of claims 1 to 3, characterized in that, The polylactic acid activator is a lipase; preferably, the polylactic acid activator is one or two of phosphodiesterase and sterolase. And / or, the lactase is β-galactosidase; And / or, the polylactic acid particles have a molecular weight of 30,000 to 50,000 and a particle size of 300 to 500 μm; And / or, the organic acid chelating agent is selected from one or more of saccharic acid, aminophosphate, citric acid, ethylenediaminetetraacetic acid, aminotriacetic acid, and diethylenetriaminepentaacetic acid; And / or, the alcohol has 2 to 5 carbon atoms; preferably, the alcohol is selected from one or more of propanol, propylene glycol, glycerol, and ethylene glycol; And / or, the water is deionized water.

5. A method for preparing the breaker according to any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: mixing polylactic acid activator, lactase and pre-breaking solution I to obtain the breaking agent.

6. The preparation method according to claim 5, characterized in that, The mixing method I is stirring, with a stirring speed of 100 rpm to 300 rpm and a stirring time of 60 to 120 min.

7. The preparation method according to claim 5 or 6, characterized in that, The preparation method of the pre-break adhesive includes the following steps: A pre-broken gel solution is obtained by mixing a solvent, amylase, cellulase, pectinase, xylanase, catalase, and polylactic acid particles; preferably, the solvent is water / or alcohol. Preferably, the mixture II comprises: (1) Mix alcohol and water by stirring to obtain mixture A; Preferably, the stirring speed for mixing a is 100-300 rpm and the time is 30-60 min; (2) Mix mixture A with amylase, cellulase, pectinase and xylanase to obtain mixture B; Preferably, the stirring speed of mixture b is 300 rpm to 600 rpm, the time is 30 to 60 min, and the temperature is 40 to 60℃; (3) Mix mixture B with catalase c to obtain mixture C; Preferably, the stirring speed of mixing c is 300 rpm to 600 rpm, the time is 30 to 60 min, and the temperature is 40 to 60℃; (4) Mix the mixture C with polylactic acid particles by stirring for d to obtain the mixture D; Preferably, the stirring speed of mixture c is 300 rpm to 600 rpm, the temperature is 40 to 60°C, and the time is 30 to 50 min; (5) Mix the mixture D with the organic acid chelating agent to obtain the mixture E. Adjust the pH of the mixture E to 3.0-5.0 to obtain the pre-broken gel solution. Preferably, the stirring speed of mixture e is 300 rpm to 600 rpm, the temperature is 40 to 60°C, and the time is 30 to 50 min.

8. The preparation method according to claim 7, characterized in that, The polylactic acid activator is a lipase; preferably, the polylactic acid activator is one or two of phosphodiesterase and sterolase. And / or, the lactase is β-galactosidase; And / or, the polylactic acid particles have a molecular weight of 30,000 to 50,000 and a particle size of 300 to 500 μm; And / or, the organic acid chelating agent is selected from one or more of saccharic acid, aminophosphate, citric acid, ethylenediaminetetraacetic acid, aminotriacetic acid, and diethylenetriaminepentaacetic acid; And / or, the alcohol has 2 to 5 carbon atoms; preferably, the alcohol is selected from one or more of propanol, propylene glycol, glycerol, and ethylene glycol; And / or, the water is deionized water; And / or, the concentration of amylase in the pre-broken gel solution is 27–72 g / L; And / or, the concentration of cellulase in the pre-broken gel solution is 27–72 g / L; And / or, the concentration of pectinase in the pre-broken pectin solution is 14–43 g / L; And / or, the concentration of xylanase in the pre-broken gel solution is 14–43 g / L; And / or, the concentration of catalase in the pre-broken adhesive solution is 71–115 g / L; And / or, the concentration of polylactic acid particles in the pre-broken adhesive solution is 42-72 g / L; And / or, the concentration of the organic acid chelating agent in the pre-broken adhesive solution is 14–43 g / L.

9. A method of using the breaker according to any one of claims 1 to 4 or the breaker prepared by the preparation method according to any one of claims 5 to 8, characterized in that, After drilling is completed and the drill string is pulled out, and the well is flushed, clean brine is injected into the well, and then a breaker is sent into the reservoir section to carry out the well sealing reaction.

10. The method of use according to claim 9, characterized in that, The conditions for the well sealing reaction include: a time of 24–36 hours and a pressure of 3.0–6.0 MPa.

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