A coiled low-stick plugging gel and a preparation method thereof
By preparing a winding low-viscosity plugging gel, a dual network structure is formed by cross-linking polyacrylamide and polyethyleneimine, which solves the problems of poor plugging performance and uncontrollable gelation time, and achieves high-efficiency plugging and improved pressure resistance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-08
- Publication Date
- 2026-03-27
AI Technical Summary
Existing plugging agents have poor selective plugging properties, affect oil production during the plugging process, are difficult to selectively plug or plug cross-channel sections, have high initial viscosity and uncontrollable gelation time, are prone to backflow, have low strength, and short shelf life.
A low-viscosity sealing gel with a winding structure is adopted. It is formed by cross-linking polyacrylamide and polyethyleneimine aqueous solution to form a dual network structure, combined with N,N'-methylenebisacrylamide as a synergist. Through cross-linking and winding, a polymer blend is formed, optimizing the cross-linked network structure and enhancing the strength and salt resistance of the gel.
It improves the sealing effect, enhances shear resistance and erosion resistance, has low initial viscosity for easy pumping, controllable gelation time, high compressive strength, and wide applicability.
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Figure CN117925203B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of oil and gas field development, and particularly relates to a winding type low-viscosity plugging gel and a preparation method thereof. BACKGROUND
[0002] The conventional plugging method mainly selects cementing, and the cementing method includes ordinary cement, ultra-fine cement and the like. The ultra-fine cement can easily enter the micro-gap space of the formation, has the advantages of high compressive strength and long effective period after setting, and can be used for plugging large pores and high-yield water layers. However, the solidified body of the ultra-fine cement has high brittleness and is easy to shrink, cannot form a firm interfacial cementation with the surrounding medium, has poor adaptability and safety, is easy to return to the wellbore, is easy to cause downhole accidents, and has difficult control of thickening time and high construction risk. The glass water inorganic salt plugging agent can selectively enter the high water absorption layer, and after reacting in the pore of the formation, forms a blockage to the high permeability layer. However, the particle size of the precipitate is large, the precipitate is easy to migrate, and the plugging stability is poor. The polymer gel has certain strength and thermal stability, and the polymer gel plugging agent is the most commonly used and most widely applied plugging agent at present. The particle gel will swell after being contacted with water, and has a certain plugging effect on the pores. However, the selected plugging particles can only have a lasting effect after being highly matched with the pores, and therefore appropriate particle sizes need to be selected according to the formation. The resin type plugging agent is a low molecular condensation material, has high strength and good stability after plugging, but the resin has high price, solidifies too fast at high temperature, is difficult to control, and is difficult to pump.
[0003] At present, the plugging materials at home and abroad mainly have the following technical problems. 1. The plugging agent has poor plugging effect. The plugging agent will reduce the oil production while plugging water, and affect the economic benefits. 2. In the water plugging and channeling operation, the plugging agent is difficult to be selectively plugged or plugged in the channeling section, and a small amount of the plugging agent entering the oil layer can seriously pollute the oil layer. 3. The chemical plugging agent has large initial viscosity, uncontrolled gel time, is not conducive to on-site operation pumping, has low strength, is easy to return, has short effective period. SUMMARY
[0004] The present application aims to provide a winding type low-viscosity plugging gel and a preparation method thereof, so as to solve the above problems.
[0005] To achieve the above-mentioned purposes, the technical solutions adopted by the present application are as follows:
[0006] The present application discloses a winding type low-viscosity plugging gel. The winding type low-viscosity plugging gel comprises the following components in parts by weight:
[0007] Gel main agent 40-45 parts
[0008] Gel synergist 0.1-0.3 parts
[0009] Gel auxiliary agent 3-5 parts.
[0010] As a preferred solution, the gel main agent comprises a polyacrylamide aqueous solution and a polyethylene imine aqueous solution in a mass ratio of 10:(30-35).
[0011] Further preferably, the polyacrylamide aqueous solution has a mass concentration of 0.08%-0.1%, and the polyethylene imine aqueous solution has a mass concentration of 22%-28%.
[0012] Preferably, the polyacrylamide aqueous solution is prepared from polyacrylamide and water in a mass ratio of (0.08-0.1):(99.9-99.92), and the polyacrylamide has a molecular weight of 15-20 million.
[0013] Preferably, the polyethylene imine aqueous solution is prepared from polyethylene imine and water in a mass ratio of (22-28):(72-78), and the polyethylene imine has a molecular weight of 60-80 thousand.
[0014] As a further preferred solution of the present application, the gel synergist is one of N,N'-methylene bisacrylamide and organic chromium.
[0015] As another preferred solution of the present application, the gel auxiliary agent comprises, by weight, 1-2 parts of acrylamide monomer, 98-99 parts of water, and 0.005-0.03 parts of initiator.
[0016] Preferably, the initiator is one of potassium persulfate and ammonium persulfate.
[0017] The present application further discloses a preparation method of the winding low-viscosity plugging gel.
[0018] S1. Preparing a gel main agent
[0019] Mix the polyacrylamide aqueous solution and the polyethylene imine aqueous solution in a mass ratio of 10:(30-35) to form the gel main agent.
[0020] S2. Preparing a gel auxiliary agent
[0021] Dissolve 1-2 parts of acrylamide monomer in 98-99 parts of water, and after the water bath temperature is raised to 70℃, add the initiator in portions, wherein the mass ratio of the acrylamide monomer to the initiator is 100:(0.5-1.5), and react for 6-7 hours to form the gel auxiliary agent.
[0022] S3. Preparing a winding low-viscosity plugging gel
[0023] Take the gel main agent 40~45 parts prepared in step S1, the gel auxiliary agent 3~5 parts prepared in step S2, completely mix, then add 0.1~0.3 parts of gel synergist, heat in water bath under the condition of 60~70 DEG C for 3~9 h, the winding type low viscosity plugging gel is obtained.
[0024] As a further preferred scheme, the initiator is slowly added at a speed of 20~30 drops per minute.
[0025] The reaction mechanism of the present application is as follows:
[0026] The acrylamide is used as the reaction monomer, the potassium persulfate is used as the initiator, and the N,N'-methylene bisacrylamide / polyethyleneimine is used as the crosslinking agent, and a double crosslinking interpenetrating network polymer is formed by initiating polymerization and crosslinking in the aqueous solution containing polyacrylamide.
[0027] By adopting the technical scheme, the present application has the following beneficial effects:
[0028] 1.The present application adopts two or more polymers to form a network interpenetrating or winding structure, and the winding polymer network is a polymer blend composed of two or more crosslinked and interpenetrating polymer networks.
[0029] 2.In the present application, the use of cationic acrylamide and acrylamide monomers enhances the bonding degree with the bottom rock while retaining the hydrophilicity of the acrylamide molecules, improves the salt resistance and temperature resistance, and the introduction of the double crosslinking network can optimize the crosslinking network structure and improve the strength of the gel.
[0030] 3.Compared with the traditional polymer gel, the winding type low viscosity plugging gel has stronger shear resistance, plugging capacity and erosion resistance, and the flexibility of the system is more easily entered into the lost circulation channel of the pore level, which makes up for the defects of the cementing ring and greatly improves the plugging effect.
[0031] 4.The carbonium ion released after the opening of the olefin double bond under the action of the initiator attacks the gel synergist, and a network core framework can be formed between the monomers, so that the polyacrylamide molecules form a winding structure around the framework, and then a relatively close network structure is formed, thereby enhancing the compressive strength of the gel.
[0032] 5. The present application adopts a mixture of monomers and polymers as the main component of the gel, which can effectively reduce the initial clay of the gel and is beneficial to the delivery of the gel.
[0033] 6. The prepared winding low-viscosity sealing gel has low initial viscosity, which is convenient for pumping in the operation site; the gel has a compression resistance of 65 MPa, good compression resistance; and the gel formation time is controllable within 3-9 h, which greatly widens the adaptability of the gel.
[0034] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, and to implement the content of the specification, the following will describe the preferred embodiments of the present application in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS
[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.
[0036] Figure 1 The infrared spectrum of the winding low-viscosity sealing gel;
[0037] Figure 2 The SEM graph of the ordinary gel;
[0038] Figure 3 The SEM graph of the winding low-viscosity sealing gel.
[0039] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the following will further describe the present application in detail with reference to the drawings and specific embodiments. DETAILED DESCRIPTION
[0040] The content of the present application can be further understood by combining the following detailed description of the preferred implementation method of the present application and the included embodiments. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs. If the definition of a specific term disclosed in the prior art is inconsistent with any definition provided in the present application, the definition of the term provided in the present application shall prevail.
[0041] In a typical embodiment of the present application, a winding low-viscosity sealing gel is provided, which includes the following components in parts by weight:
[0042] Gel main agent 40-45 parts
[0043] Gel synergist 0.1-0.3 parts
[0044] Gel auxiliary agent 3-5 parts.
[0045] As a preferred embodiment, the gel main agent comprises 10: (30-35) of polyacrylamide aqueous solution and polyethylene imine aqueous solution by weight percentage.
[0046] Further, the mass concentration of the polyacrylamide aqueous solution is 0.08%-0.1%, and the mass concentration of the polyethylene imine aqueous solution is 22%-28%.
[0047] As a preferred embodiment, the polyacrylamide aqueous solution is prepared from polyacrylamide and water in a mass ratio of (0.08-0.1):(99.9-99.92), and the molecular weight of the polyacrylamide is 15-20 million.
[0048] As a preferred embodiment, the polyethylene imine aqueous solution is prepared from polyethylene imine and water in a mass ratio of (22-28):(72-78), and the molecular weight of the polyethylene imine is 60-80 thousand.
[0049] As another preferred embodiment of the present application, the gel synergist is one of N,N'-methylene bisacrylamide and organic chromium. After the gel synergist is attacked by carbonium ion, a network core framework is formed between monomers, so that the polyacrylamide molecules form a winding structure around the framework, and then form a relatively close network structure, thus enhancing the compression strength of the gel.
[0050] As another preferred embodiment of the present application, the gel auxiliary agent comprises 1-2 parts of acrylamide monomer, 98-99 parts of water, and 0.005-0.03 parts of initiator by weight percentage.
[0051] As a preferred embodiment, the initiator is one of potassium persulfate and ammonium persulfate.
[0052] The present application forms a winding gel with low initial viscosity, controllable gel time of 3-9 hours, and high compression resistance by screening the molecular weight of polyacrylamide and polyethylene imine in the gel main agent, optimizing the ratio of acrylamide monomer and initiator in the gel auxiliary agent, and optimizing the gel synergist.
[0053] In addition, the present application forms a network of mutual penetration or winding structure by using two or more polymers, and the winding polymer network is a polymer blend composed of two or more crosslinked and mutually penetrating polymer networks. Different polymer molecules are intertwined to form a whole and cannot be separated, so the gel strength is relatively high.
[0054] In the second typical embodiment of the present application, a preparation method of the winding low-viscosity plugging gel is provided, comprising the following steps:
[0055] S1. Preparing a gel main agent
[0056] The polyacrylamide aqueous solution and the polyethylene imine aqueous solution are mixed according to a mass ratio of 10:(30-35) to form the gel main agent.
[0057] S2. Preparing a gel auxiliary agent
[0058] 1-2 parts of acrylamide monomers are dissolved in 98-99 parts of water, and after the water bath temperature is raised to 70℃, the initiator is added in batches, wherein the mass ratio of the acrylamide monomers to the initiator is 100:(0.5-1.5), and the reaction is carried out for 6-7 hours to form the gel auxiliary agent.
[0059] S3. Preparing a winding low-viscosity plugging gel
[0060] After 40-45 parts of the gel main agent prepared in step S1 and 3-5 parts of the gel auxiliary agent prepared in step S2 are completely mixed, 0.1-0.3 parts of a gel synergist is added, and the mixture is heated in a water bath at 60-70℃ for 3-9 hours to obtain the winding low-viscosity plugging gel.
[0061] As a further preferred scheme, the initiator is slowly added at a speed of 20-30 drops per minute.
[0062] The winding low-viscosity plugging gel prepared by the present application has a low initial viscosity, which is convenient for pumping at the operation site; the gel has a compression resistance of 65 MPa, and has a good compression resistance performance; and the gel formation time is controllable within 3-9 hours, which greatly widens the adaptability of the gel.
[0063] The present application is further described below in combination with examples:
[0064] Example 1
[0065] A preparation process of a winding low-viscosity plugging gel is as follows:
[0066] Under stirring, polyacrylamide is uniformly added into water to prepare a polyacrylamide aqueous solution with a mass concentration of 0.1%.
[0067] 100g of 30% polyethylene imine is measured and added into 20g of water to prepare a polyethylene imine aqueous solution with a mass concentration of 25%.
[0068] The above polyacrylamide aqueous solution and the polyethylene imine aqueous solution are mixed according to a mass ratio of 10:33 to form the gel main agent.
[0069] After 2 g of acrylamide monomer is dissolved in 98 g of water, it is added to a four-necked flask. After the water bath is heated to 70°C, an aqueous solution of potassium persulfate is slowly added to the four-necked flask at a rate of 2-3 seconds per drop using a dropping funnel. The mass ratio of acrylamide monomer to potassium persulfate is 1:0.01. The reaction is carried out for 6.5 hours to form a gel adjuvant.
[0070] After the prepared gel main agent 43 mL and the gel adjuvant 4 g are thoroughly mixed, 0.2 g of a gel synergist N,N'-methylenebisacrylamide is added. The mixture is heated in a water bath at 70°C for 6.5 hours to obtain a winding low-viscosity sealing gel.
[0071] The winding low-viscosity sealing gel is subjected to infrared analysis. The infrared spectrum is shown in Figure 1 .
[0072] The infrared analysis shows that the absorption peaks at 3000-3500 cm -1 correspond to the stretching vibration of N-H; the two absorption peaks at 2880-2970 cm -1 correspond to the anti-symmetrical stretching vibration and symmetrical stretching vibration of CH3; the absorption peak at 1780 cm -1 corresponds to the stretching vibration of C=0; the absorption peak at 1390 cm -1 corresponds to the stretching vibration of CH2; and the absorption peak at 1370 cm -1 corresponds to the stretching vibration of C-N. The infrared spectrum shows that the gel contains various polymer groups.
[0073] The ordinary gel and the winding low-viscosity sealing gel are subjected to scanning electron microscope analysis. The SEM scanning electron micrographs of the ordinary gel and the winding low-viscosity sealing gel are shown in Figure 2 and Figure 3 .
[0074] The electron microscope analysis shows that the ordinary gel has larger pores and is relatively loose, while the winding gel has smaller pores and is relatively dense, and the reticular structure is obviously enhanced.
[0075] Example 2
[0076] A method for preparing a winding low-viscosity sealing gel is as follows:
[0077] An aqueous solution of polyacrylamide with a mass concentration of 0.1% and an aqueous solution of polyethyleneimine with a mass concentration of 28% are prepared.
[0078] The prepared aqueous solution of polyacrylamide with a mass concentration of 0.1% and the aqueous solution of polyethyleneimine with a mass concentration of 28% are mixed in a ratio of 10:32 to form a gel main agent, which is ready for use.
[0079] After 2 g of acrylamide monomer is dissolved in 98 g of water and added to a four-necked flask, the water bath is heated to 70°C. Then, an aqueous solution of ammonium persulfate is slowly added to the four-necked flask at a rate of 2-3 seconds per drop. The mass ratio of acrylamide monomer to ammonium persulfate is 1:0.015. The reaction is carried out for 6 hours to form a gel adjuvant.
[0080] After the prepared gel main agent 40 mL and gel adjuvant 3 g are thoroughly mixed, 0.15 g of a gel synergist is added. The mixture is heated in a water bath at 70°C for 3.5 hours to obtain a winding low-viscosity sealing gel.
[0081] The obtained winding low-viscosity sealing gel is tested in a digital viscometer, and the initial concentration is measured to be 35.1 mPa.s.
[0082] The winding low-viscosity sealing gel is injected into a sand filling pipe at a rate of 0.5 mL / min. After 30 mL is injected, the mixture is allowed to set at 80°C for 8 hours. After setting, water is injected at a rate of 0.1-0.5 mL / min for water flooding until water flows out of the sand filling pipe. The maximum pressure is recorded, and the system pressure resistance is measured to be 36.89 MPa.
[0083] Example 3
[0084] A method for preparing a winding low-viscosity sealing gel comprises the following steps:
[0085] A 0.09% polyacrylamide aqueous solution and a 26% polyethyleneimine aqueous solution are prepared.
[0086] The prepared 0.09% polyacrylamide aqueous solution and 26% polyethyleneimine aqueous solution are mixed in a ratio of 10:34 and are ready for use.
[0087] After 1.5 g of acrylamide monomer is dissolved in 98.5 g of water and added to a four-necked flask, the water bath is heated to 70°C. Then, an aqueous solution of potassium persulfate is slowly added to the four-necked flask at a rate of 2-3 seconds per drop. The mass ratio of acrylamide monomer to potassium persulfate is 1:0.005. The reaction is carried out for 7 hours to form a gel adjuvant.
[0088] After the prepared gel main agent 43 mL and gel adjuvant 3.5 g are thoroughly mixed, 0.25 g of a gel synergist is added. The mixture is heated in a water bath at 70°C for 4 hours to obtain a winding low-viscosity sealing gel.
[0089] The obtained winding low-viscosity sealing gel is tested in a digital viscometer, and the initial concentration of the winding low-viscosity sealing gel is measured to be 36.8 mPa.s.
[0090] The spiral-wound low-viscosity sealing gel was injected into the sand-filled tube at a rate of 0.5 mL / min. After 30 mL was injected, the tube was allowed to solidify at 80℃ for 8 hours. After solidification, water was injected at a rate of 0.1-0.5 mL / min for water drive until water flowed out of the sand. The maximum pressure was recorded, and the compressive strength of the system was measured to be 42.16 MPa.
[0091] Example 4
[0092] A method for preparing a wound-type low-viscosity plugging gel is as follows:
[0093] Prepare an aqueous solution of polyacrylamide with a mass concentration of 0.08% and an aqueous solution of polyethyleneimine with a mass concentration of 24%;
[0094] Mix the prepared 0.08% polyacrylamide aqueous solution with the 24% polyethyleneimine aqueous solution at a ratio of 10:35 and set aside for later use.
[0095] Dissolve 2g of acrylamide monomer in 98g of water and add it to a four-necked flask. After the water bath is heated to 70°C, slowly add potassium persulfate aqueous solution to the four-necked flask at a rate of 2-3 drops per second. The mass ratio of acrylamide monomer to potassium persulfate is 1:0.009. React for 6.5 hours to form a gel excipient.
[0096] After thoroughly mixing 45 mL of the prepared gel main agent and 5 g of the gel excipient, 0.3 g of gel synergist was added, and the mixture was heated in a water bath at 70°C for 5 hours to obtain the winding low-viscosity sealing gel.
[0097] The obtained spiral-wound low-viscosity plugging gel was tested in a digital viscometer, and the initial concentration of the spiral-wound low-viscosity plugging gel was measured to be 42.1 mPa·s.
[0098] The spiral-wound low-viscosity sealing gel was injected into the sand-filled tube at a rate of 0.5 mL / min. After 30 mL was injected, the tube was allowed to solidify at 80℃ for 8 hours. After solidification, water was injected at a rate of 0.1-0.5 mL / min for water drive until water flowed out of the sand. The maximum pressure was recorded, and the compressive strength of the system was measured to be 46.7 MPa.
[0099] Example 5
[0100] A method for preparing a wound-type low-viscosity plugging gel is as follows:
[0101] Prepare an aqueous solution of polyacrylamide with a mass concentration of 0.08% and an aqueous solution of polyethyleneimine with a mass concentration of 25%;
[0102] Mix the prepared 0.08% polyacrylamide aqueous solution with the 25% polyethyleneimine aqueous solution at a ratio of 10:33 and set aside for later use.
[0103] Dissolve 1.5g of acrylamide monomer in 98.5g of water and add it to a four-necked flask. After the water bath is heated to 70°C, slowly add potassium persulfate aqueous solution to the four-necked flask at a rate of 2-3 drops per second. The mass ratio of acrylamide monomer to potassium persulfate is 1:0.008. React for 6.5 hours to form a gel excipient.
[0104] After thoroughly mixing 45 mL of the prepared gel main agent and 5 g of the gel excipient, 0.3 g of gel synergist was added, and the mixture was heated in a water bath at 70°C for 9 hours to obtain the winding low-viscosity sealing gel.
[0105] The obtained spiral-wound low-viscosity plugging gel was tested in a digital viscometer, and the initial concentration of the spiral-wound low-viscosity plugging gel was measured to be 54.2 mPa·s.
[0106] The spiral-wound low-viscosity sealing gel was injected into the sand-filled tube at a rate of 0.5 mL / min. After 30 mL was injected, the tube was allowed to solidify at 80℃ for 8 hours. After solidification, water was injected at a rate of 0.1-0.5 mL / min for water drive until water flowed out of the sand. The maximum pressure was recorded, and the compressive strength of the system was measured to be 65 MPa.
[0107] Example 6
[0108] A method for preparing a wound-type low-viscosity plugging gel is as follows:
[0109] Prepare an aqueous solution of polyacrylamide with a mass concentration of 0.09% and an aqueous solution of polyethyleneimine with a mass concentration of 22%;
[0110] Mix the prepared 0.09% polyacrylamide aqueous solution with the 22% polyethyleneimine aqueous solution at a ratio of 10:33 and set aside for later use.
[0111] Dissolve 1.8g of acrylamide monomer in 98.2g of water and add it to a four-necked flask. After the water bath is heated to 70°C, slowly add potassium persulfate aqueous solution to the four-necked flask at a rate of 2-3 drops per second. The mass ratio of acrylamide monomer to potassium persulfate is 1:0.007. React for 6 hours to form a gel excipient.
[0112] After thoroughly mixing 43.5 mL of the prepared gel main agent and 4.5 g of the gel excipient, 0.25 g of gel synergist was added, and the mixture was heated in a water bath at 70°C for 8 hours to obtain the winding low-viscosity sealing gel.
[0113] The obtained spiral-wound low-viscosity plugging gel was tested in a digital viscometer, and the initial concentration of the spiral-wound low-viscosity plugging gel was measured to be 52.1 mPa·s.
[0114] The spiral-wound low-viscosity sealing gel was injected into the sand-filled tube at a rate of 0.5 mL / min. After 30 mL was injected, the tube was allowed to solidify at 80℃ for 8 hours. After solidification, water was injected at a rate of 0.1-0.5 mL / min for water drive until water flowed out of the sand. The maximum pressure was recorded, and the compressive strength of the system was measured to be 58 MPa.
[0115] Example 7
[0116] A method for preparing a wound-type low-viscosity plugging gel is as follows:
[0117] Prepare an aqueous solution of polyacrylamide with a mass concentration of 0.1% and an aqueous solution of polyethyleneimine with a mass concentration of 30%;
[0118] Mix the prepared 0.1% polyacrylamide aqueous solution with the 30% polyethyleneimine aqueous solution at a ratio of 10:32 and set aside for later use.
[0119] Dissolve 2g of acrylamide monomer in 98g of water and add it to a four-necked flask. After the water bath is heated to 70°C, slowly add potassium persulfate aqueous solution to the four-necked flask at a rate of 2-3 drops per second. The mass ratio of acrylamide monomer to potassium persulfate is 1:0.01. React for 6.5 hours to form a gel excipient.
[0120] After thoroughly mixing 43 mL of the prepared gel main agent and 4 g of the gel excipient, 0.2 g of gel synergist was added, and the mixture was heated in a water bath at 70°C for 7.5 h to obtain the winding low-viscosity sealing gel.
[0121] The obtained spiral-wound low-viscosity plugging gel was tested in a digital viscometer, and the initial concentration of the spiral-wound low-viscosity plugging gel was measured to be 50.2 mPa·s.
[0122] The spiral-wound low-viscosity sealing gel was injected into the sand-filled tube at a rate of 0.5 mL / min. After 30 mL was injected, the tube was allowed to solidify at 80℃ for 8 hours. After solidification, water was injected at a rate of 0.1-0.5 mL / min for water drive until water flowed out of the sand. The maximum pressure was recorded, and the compressive strength of the system was measured to be 55.37 MPa.
[0123] Example 8
[0124] A method for preparing a wound-type low-viscosity plugging gel is as follows:
[0125] Prepare an aqueous solution of polyacrylamide with a mass concentration of 0.09% and an aqueous solution of polyethyleneimine with a mass concentration of 27%;
[0126] Mix the prepared 0.09% polyacrylamide aqueous solution with the 27% polyethyleneimine aqueous solution at a ratio of 10:33 and set aside for later use.
[0127] Dissolve 1.5g of acrylamide monomer in 98.5g of water and add it to a four-necked flask. After the water bath is heated to 70°C, slowly add potassium persulfate aqueous solution to the four-necked flask at a rate of 2-3 drops per second. The mass ratio of acrylamide monomer to potassium persulfate is 1:0.006. React for 6 hours to form a gel excipient.
[0128] After thoroughly mixing 41.5 mL of the prepared gel main agent and 3.5 g of the gel excipient, 0.15 g of gel synergist was added, and the mixture was heated in a water bath at 70°C for 8 hours to obtain the winding low-viscosity sealing gel.
[0129] The obtained spiral-wound low-viscosity plugging gel was tested in a digital viscometer, and the initial concentration of the spiral-wound low-viscosity plugging gel was measured to be 48.6 mPa·s.
[0130] The spiral-wound low-viscosity sealing gel was injected into the sand-filled tube at a rate of 0.5 mL / min. After 30 mL was injected, the tube was allowed to solidify at 80℃ for 8 hours. After solidification, water was injected at a rate of 0.1-0.5 mL / min for water drive until water flowed out of the sand. The maximum pressure was recorded, and the compressive strength of the system was measured to be 61 MPa.
[0131] The above description is merely a preferred embodiment of the present invention and is illustrative in nature, not intended to limit the scope of the invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims.
Claims
1. A wound-type low-viscosity sealing gel, characterized in that, This wound-type low-viscosity sealing gel comprises the following components by weight: 40-45 parts of gel main agent; 0.1-0.3 parts of gelling agent; 3-5 parts of gelling agent; The gelling agent comprises an aqueous solution of polyacrylamide and an aqueous solution of polyethyleneimine in a weight percentage ratio of 10:(30~35); The gel synergist is one of N,N'-methylenebisacrylamide and organic chromium; The gelling agent, by weight, comprises 1-2 parts acrylamide monomer, 98-99 parts water, and 0.005-0.03 parts initiator.
2. The spiral-wound low-viscosity sealing gel as described in claim 1, characterized in that: The mass concentration of the polyacrylamide aqueous solution is 0.08%~0.1%, and the mass concentration of the polyethyleneimine aqueous solution is 22%~28%.
3. The winding low-viscosity sealing gel as described in claim 1, characterized in that: The polyacrylamide aqueous solution is prepared by mixing polyacrylamide and water in a mass ratio of (0.08~0.1):(99.9~99.92), and the molecular weight of the polyacrylamide is 15 million to 20 million.
4. The wound-type low-viscosity sealing gel as described in claim 1, characterized in that: The polyethyleneimine aqueous solution is prepared by mixing polyethyleneimine and water in a mass ratio of (22~28):(72~78), and the molecular weight of the polyethyleneimine is 60,000 to 80,000.
5. The spiral-wound low-viscosity sealing gel as described in claim 1, characterized in that: The initiator is one of potassium persulfate or ammonium persulfate.
6. A method for preparing the spiral-wound low-viscosity sealing gel according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Preparation of gel main agent Aqueous solutions of polyacrylamide and polyethyleneimine are mixed at a mass ratio of 10:(30~35) to form a gelling agent; S2. Preparation of gelation adjuvants Dissolve 1-2 parts of acrylamide monomer in 98-99 parts of water. After the water bath temperature rises to 70°C, add the initiator in portions, wherein the mass ratio of acrylamide monomer to initiator is 100:(0.5-1.5). React for 6-7 hours to form a gelling agent. S3. Preparation of spiral-wound low-viscosity plugging gel Take 40-45 parts of the gel main agent obtained in step S1 and 3-5 parts of the gel excipient obtained in step S2, mix them completely, add 0.1-0.3 parts of gel synergist, and heat in a water bath at 60-70℃ for 3-9 hours to obtain the winding low-viscosity sealing gel.
7. The method for preparing the spiral-wound low-viscosity plugging gel as described in claim 6, characterized in that: The initiator is added slowly at a rate of 20-30 drops per minute.