A soluble liquid bridge plug, preparation method and horizontal well segmented water plugging method

Abstract

The present invention particularly relates to a soluble liquid bridge plug, a preparation method and a horizontal well segmented water plugging method, and belongs to the field of oil extraction technology. The raw materials of the soluble liquid bridge plug include heat-resistant and salt-resistant monomers, acrylamide monomers, degradable polymer polyester particles, cross-linking agents, retarders, initiators and density regulators. The soluble liquid bridge plug prepared by the above raw materials has viscoelasticity, so that it can effectively plug the horizontal section of the horizontal well, and because it is water-soluble, the soluble bridge plug in the water-producing target section can be replaced by water drive, so as to facilitate the subsequent plugging of the water-producing target section. And the soluble liquid bridge plug has good injectability, heat resistance, salt resistance and mineralization resistance, and meets the requirements of water plugging and profile adjustment of horizontal wells in different types of oil reservoirs such as sandstone and carbonate.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum extraction, and in particular relates to a soluble liquid bridge plug, a preparation method and a horizontal well segmented water plugging method. Background Art

[0002] As a powerful tool that can greatly improve the comprehensive benefits of oilfield exploration and development, horizontal wells are widely used in various oil reservoirs. However, due to the lack of effective water plugging technology, many horizontal wells are forced to produce with problems, produce intermittently, or stop production for a long time after the occurrence of severe water production problems. This has become an urgent problem that plagues the normal production and sustainable development of horizontal wells.

[0003] At present, more than 80% of horizontal well water plugging adopts the treatment method of polymer + general injection, and the treatment effect is not satisfactory. The successful experience of individual single wells is difficult to promote and generalize in other horizontal wells. In addition, the current horizontal well water plugging uses mechanical methods (packers, etc.) to segment in the wellbore, which can only be segmented in the wellbore, and the wellbore is still connected outside, and the horizontal well segmentation cannot be truly realized; in addition, the wellbore safety and reservoir safety in the horizontal well water plugging construction are difficult to guarantee, and the existing well repair technology is difficult to repair the horizontal section. For example, the horizontal well completion in Liaohe Oilfield is mainly open-hole screen completion, accounting for 93.8% of the total number of well completions. Screen completion water plugging is the most difficult, because there is no barrier between the screen and the rock wall, and the fluid can flow radially and horizontally. In practice, it is very difficult to achieve layered and segmented water plugging. At present, there is no effective bridge plug and plugging agent injection method that can achieve segmented water plugging of screen completion horizontal wells, and the water discharge problem of horizontal wells has become one of the main contradictions restricting the production of horizontal wells. Summary of the invention

[0004] The purpose of the present application is to provide a soluble liquid bridge plug to solve the technical problem that the existing bridge plugs cannot effectively achieve segmented water plugging in horizontal wells.

[0005] The embodiment of the present invention provides a soluble liquid bridge plug, the raw materials of which include a temperature-resistant and salt-resistant monomer, an acrylamide monomer, a degradable polymer polyester particle, a cross-linking agent, a retarder, an initiator and a density regulator.

[0006] Optionally, the raw materials include, by mass percentage: 1-5% of temperature-resistant and salt-resistant monomers, 6-10% of acrylamide monomers, 5-15% of degradable polymer polyester particles, 0.02-0.06% of crosslinking agent, 0.02-0.05% of retarder, 0.02-0.05% of initiator and 2-8% of density regulator.

[0007] Optionally, the temperature-resistant and salt-resistant monomer includes any one or more combinations of AMPS-Na, N-vinyl pyrrolidone and N-vinylamide.

[0008] Optionally, the acrylamide monomer includes acrylamide or methacrylamide.

[0009] Optionally, the degradable polymer polyester particles include any one or more combinations of polyurethane, polylactic acid, polyglycolic acid, polylactic acid-glycolic acid copolymer, polycaprolactone, polysuccinate and polyethylene adipate.

[0010] Optionally, the cross-linking agent is N,N'-methylenebisacrylamide.

[0011] Optionally, the retarder is any one or more combinations of potassium ferrocyanide, lignin sulfonate, borax, organic acid and disodium ethylenediamine acetate.

[0012] Optionally, the initiator comprises ammonium persulfate and sodium bisulfite in a mass ratio of 1:1.

[0013] Optionally, the density regulator includes potassium chloride or sodium chloride.

[0014] The embodiment of the present invention further provides a method for preparing any one of the above-mentioned soluble liquid bridge plugs, comprising the following steps:

[0015] The heat-resistant and salt-resistant monomer, the acrylamide monomer, the degradable polymer polyester particles, the cross-linking agent and the retarder are mixed and first stirred to obtain a prefabricated liquid;

[0016] The prefabricated liquid and the initiator are mixed and stirred for a second time to obtain a polymer solution;

[0017] The polymer is mixed with a density regulator and the temperature is adjusted to 20-50° C. to obtain the soluble liquid bridge plug.

[0018] Optionally, the stirring frequency of the first stirring is 6-30 r / min, and the stirring time of the first stirring is 30 min.

[0019] Optionally, the stirring frequency of the second stirring is 6-30 r / min, and the stirring time of the second stirring is 5 min.

[0020] The embodiment of the present invention also provides a horizontal well segmented water plugging method, comprising the following steps:

[0021] Divide the horizontal section of the horizontal well into sections to obtain multiple test production sections;

[0022] Conducting trial production on each of the trial production sections in turn to obtain a water-yielding target section;

[0023] Inject any one of the above-mentioned soluble liquid bridge plugs into the horizontal section to fill the horizontal section;

[0024] Using water drive to replace the soluble liquid bridge plug in the water production target section and waiting for solidification;

[0025] Injecting a water plugging agent into the target water outlet section for plugging;

[0026] Steam or a gel breaker is injected into the horizontal section to remove the soluble gel plug.

[0027] Optionally, the degelling agent includes hydrogen peroxide solution or potassium permanganate solution.

[0028] Optionally, the concentration of the breaker is 5-10%, and the dosage of the breaker is 20-60m 3 / m.

[0029] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0030] The embodiment of the present invention provides a soluble liquid bridge plug, the raw materials of which include heat-resistant and salt-resistant monomers, acrylamide monomers, degradable polymer polyester particles, cross-linking agents, retarders, initiators and density regulators. The soluble liquid bridge plug prepared by the above raw materials has viscoelasticity, so that it can effectively block the horizontal section of the horizontal well, and because it is water-soluble, the soluble bridge plug in the water-producing target section can be replaced by water drive, so as to facilitate the subsequent blocking of the water-producing target section. In addition, the soluble liquid bridge plug has good injectability, heat resistance, salt resistance and mineralization resistance, and meets the requirements of water plugging and profile control of horizontal wells in different types of oil reservoirs such as sandstone and carbonate.

[0031] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 It is a flow chart of a horizontal well segmented water plugging method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below in conjunction with specific implementations and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific implementations and examples are used to illustrate the present invention, rather than to limit the present invention.

[0035] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. If there is a conflict, the present specification takes precedence. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. For example, room temperature can refer to a temperature within the range of 10 to 35°C.

[0036] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0037] The technical solution of the embodiment of the present application is to solve the above technical problems, and the overall idea is as follows:

[0038] According to a typical embodiment of the present invention, a soluble liquid bridge plug is provided, the raw materials of which include temperature-resistant and salt-resistant monomers, acrylamide monomers, degradable polymer polyester particles, a cross-linking agent, a retarder, an initiator and a density regulator.

[0039] In this scheme, the detailed description of the functions of the above raw materials is as follows:

[0040] Heat-resistant and salt-resistant monomers: The introduction of heat-resistant and salt-resistant monomers makes the product formed after synthesis not easily degraded in high-temperature and high-mineralization media, increases the rigidity of the polymer molecular chain and the regularity of the molecular structure, makes it difficult for the polymer molecular chain to curl, and improves the viscosity-increasing, salt-resistant and temperature-resistant capabilities.

[0041] Acrylamide monomers: They are the gel-forming skeleton of soluble bridge plugs produced by the reaction of acrylamide monomers and cross-linking agents and exist as the basic formula system.

[0042] Degradable polymer polyester particles: They serve the purpose of blocking large channels or gas channeling channels, while ensuring that they slowly degrade or hydrate under the action of high temperature steam injection, so as to achieve the purpose of blocking part of the water outlet channel while blocking the oil outlet channel without killing it.

[0043] Cross-linking agent: It plays the role of cross-linking reaction with the main agent acrylamide to produce the basic skeleton of soluble bridge plug.

[0044] Retarder: Delays the gelation reaction time and controls the gelation time, which is beneficial for the gelation of soluble bridge plugs in the formation, prevents gelation in the wellbore, and avoids underground accidents.

[0045] Initiator: It catalyzes the reaction.

[0046] Density regulator: adjusts the density of the soluble bridge plug, causing the colloid to be deposited in the wellbore and bury the perforated well section or oil layer due to excessive density.

[0047] Preferably, the raw materials include by mass percentage:

[0048] The heat-resistant and salt-resistant monomer is 1-5%, the acrylamide monomer is 6-10%, the degradable high molecular polyester particles are 5-15%, the cross-linking agent is 0.02-0.06%, the retarder is 0.02-0.05%, the initiator is 0.02-0.05% and the density regulator is 2-8%.

[0049] The reason why the soluble liquid bridge plug provided by the present invention has viscoelasticity and water solubility is that viscoelasticity and water solubility are the characteristics of the soluble bridge plug colloid. The mesh structure formed by the cross-linking reaction between the acrylamide monomer and the cross-linking agent encapsulates water in the lattice structure to form a viscoelastic jelly colloid. The jelly colloid slowly crawls forward like an earthworm under the displacement pressure. It is water-soluble because its lattice structure contains a large amount of water. At the same time, the jelly colloid contains a large amount of hydrogen bonds, which can be adsorbed with water, thereby producing a water plugging effect.

[0050] The reason for having good injectivity, temperature resistance, salt resistance and mineralization resistance is that the soluble bridge plug must have good injectivity when gelling so that it can be smoothly injected into the formation without being deposited in the wellbore. The requirement of temperature resistance and salt resistance is because the soluble bridge plug is easy to fail to gel or has low gel strength under high temperature and high salt conditions, and the plugging effect cannot be achieved.

[0051] In some embodiments, the temperature-resistant and salt-resistant monomer includes any one or more combinations of AMPS-Na, N-vinyl pyrrolidone and N-vinylamide.

[0052] In some embodiments, the acrylamide monomer includes acrylamide or methacrylamide.

[0053] In some embodiments, the degradable polymer polyester particles include any one or more combinations of polyurethane, polylactic acid, polyglycolic acid, polylactic acid-glycolic acid copolymer, polycaprolactone, polysuccinate and polyethylene adipate.

[0054] In some embodiments, the cross-linking agent is N,N'-methylenebisacrylamide.

[0055] In some embodiments, the retarder is any one or more combinations of potassium ferrocyanide, lignin sulfonate, borax, organic acid and disodium ethylenediamine acetate.

[0056] In some embodiments, the initiator includes ammonium persulfate and sodium bisulfite in a mass ratio of 1:1.

[0057] The reason for selecting the above two substances and specific ratio as initiators is that the system has low activation energy, can initiate polymerization reaction under low temperature conditions, and has a faster polymerization rate.

[0058] In some embodiments, the density modifier comprises potassium chloride or sodium chloride.

[0059] The mechanism of selecting any one of the above two substances as the density regulator is that adding potassium chloride or sodium chloride can make the density of the soluble liquid bridge plug consistent with that of the formation water, thereby preventing the liquid bridge plug from stratifying and migrating.

[0060] According to another typical embodiment of the present invention, a method for preparing the above-mentioned soluble liquid bridge plug is also provided, comprising the following steps:

[0061] S1. Mixing and first stirring the temperature-resistant and salt-resistant monomer, acrylamide monomer, degradable polymer polyester particles, a cross-linking agent and a retarder to obtain a prefabricated liquid.

[0062] S2, mixing the prefabricated liquid and the initiator and stirring for a second time to obtain a polymer solution.

[0063] S3, mixing the polymer with a density regulator, and adjusting the temperature to 20-50° C. to obtain the soluble liquid bridge plug.

[0064] The preparation method provided by the present invention can quickly and effectively prepare a soluble liquid bridge plug with viscoelasticity and water solubility through the above steps S1-S3. Specifically, first, acrylamide monomers react preliminarily with a crosslinking agent and a retarder to form acrylamide pre-crosslinked polymers, which wrap degradable polymer polyester particles. Then, under the action of an initiator, the pre-crosslinked polymers copolymerize with the temperature-resistant and salt-resistant monomers to form a copolymer soluble bridge plug.

[0065] In step S3, the mechanism for controlling the temperature to be 20-50°C is that if the temperature is too low, the reaction speed is slow, and the reaction time is too long, the soluble bridge plug will be affected by the adverse conditions of the formation after entering the formation, and it is easy to fail to gel or the gel strength is low; if the temperature is too high and the reaction speed is too fast, the soluble bridge plug will gel in the wellbore, blocking the wellbore and causing an underground accident.

[0066] In some embodiments, the stirring frequency of the first stirring is 6-30 r / min, and the stirring time of the first stirring is 30 min.

[0067] In some embodiments, the stirring frequency of the second stirring is 6-30 r / min, and the stirring time of the second stirring is 5 min.

[0068] The reason for controlling the above stirring frequency and stirring time is that if the stirring frequency is too fast or the time is too long, the shearing effect on the polymer molecular chain is too great, resulting in molecular chain breakage.

[0069] According to another typical embodiment of the present invention, a horizontal well segmented water plugging method is also provided, comprising the following steps:

[0070] S1. Divide the horizontal section of the horizontal well into sections to obtain multiple test production sections.

[0071] S2. Conduct trial production on each of the trial production sections in turn to obtain a water-yielding target section.

[0072] S3. Inject any one of the above-mentioned soluble liquid bridge plugs into the horizontal section to fill the horizontal section.

[0073] Specifically, the steps include:

[0074] S3.1 inserting the oil pipe down to the toe of the horizontal well;

[0075] S3.2 Inject any of the above-mentioned soluble liquid bridge plugs into the horizontal well by means of positive displacement injection to fill the horizontal section.

[0076] S4. Use water drive to replace the soluble liquid bridge plug in the water-producing target section and wait for solidification.

[0077] Specifically, the oil pipe is lifted up so that the outlet of the oil pipe is located in the water-yielding target section, and the soluble liquid bridge plug in the water-yielding target section is replaced by water drive, and then waited for its solidification.

[0078] S5. Inject a water plugging agent into the target water outlet section for plugging.

[0079] Specifically, the water plugging agent is injected into the target water-producing section through the oil pipe to effectively seal the water-producing section. Other well sections are effectively protected because solidified soluble liquid bridge plugs are injected in advance, effectively blocking the water plugging agent from entering.

[0080] S6. Inject steam or a breaker into the horizontal section to remove the soluble liquid bridge plug.

[0081] Specifically, steam or a breaker is injected into the horizontal well through an oil pipe to completely break the soluble liquid bridge plug and convert it into a low-viscosity aqueous solution to facilitate its effective discharge. The oil pipe is then lifted out of the horizontal well to complete the entire water plugging construction process.

[0082] The horizontal well segmented water plugging method provided by the present invention effectively locates the specific position of the water-yielding target section through steps S1 and S2, providing a prerequisite for accurate segmented water plugging. Through step S3, the soluble liquid bridge plug is first completely filled in the horizontal section by using the positive replacement spraying method, so that the protection of the entire horizontal section is realized in a simple, fast and feasible manner. Then, through step S4, the soluble liquid bridge plug is effectively replaced in the water-yielding target section by water displacement due to the solubility of the soluble liquid bridge plug, and the arrangement of the water plugging construction environment is completed. Then, through step S5, the water-yielding target section is plugged. The entire implementation process is convenient, accurate and feasible, and can effectively realize the segmented water plugging of the horizontal well.

[0083] In some embodiments, the breaker includes hydrogen peroxide solution or potassium permanganate solution.

[0084] After the degumming agent is injected, the soluble liquid bridge plug can be oxidized and decomposed into a low-viscosity aqueous solution, which is easy to discharge.

[0085] In some embodiments, the concentration of the breaker is 5-10%, and the amount of the breaker is 20-60m 3 / m.

[0086] The scheme of the present application will be described in detail below with reference to embodiments, comparative examples and experimental data.

[0087] Example 1

[0088] This embodiment provides a soluble liquid bridge plug, the raw materials of which include, by mass percentage:

[0089] (1) Temperature-resistant and salt-resistant monomer: AMPS-Na, 1%;

[0090] (2) Acrylamide monomers: acrylamide, 6%;

[0091] (3) Cross-linking agent: N,N'-methylenebisacrylamide, 0.02%;

[0092] (4) Retarder: potassium ferrocyanide, 0.02%;

[0093] (5) Initiator: ammonium persulfate, 0.01% and sodium bisulfite, 0.01%;

[0094] (6) Density regulator: potassium chloride, 2%;

[0095] (7) Degradable polymer polyester particles: polyurethane, 5%;

[0096] (8) The balance is water.

[0097] This embodiment also provides a method for preparing the above-mentioned soluble liquid bridge plug, comprising the following steps:

[0098] S1, mixing and first stirring the temperature-resistant and salt-resistant monomer, acrylamide monomer, degradable polymer polyester particles, a cross-linking agent and a retarder to obtain a prefabricated liquid;

[0099] S2, mixing the prefabricated liquid and the initiator, and stirring the mixture to obtain a polymer solution;

[0100] S3, mixing the polymer with a density regulator, and adjusting the temperature to 20° C. to obtain the soluble liquid bridge plug.

[0101] Wherein: the stirring frequency of the first stirring is 6 r / min, and the stirring time of the first stirring is 30 min. The stirring frequency of the second stirring is 6 r / min, and the stirring time of the second stirring is 5 min.

[0102] Example 2

[0103] This embodiment provides a soluble liquid bridge plug, the raw materials of which include, by mass percentage:

[0104] (1) Temperature-resistant and salt-resistant monomer: N-vinyl pyrrolidone, 5%;

[0105] (2) Acrylamide monomer: methacrylamide, 10%;

[0106] (3) Cross-linking agent: N,N'-methylenebisacrylamide, 0.06%;

[0107] (4) Retarder: disodium ethylenediamine acetate, 0.05%;

[0108] (5) Initiator: ammonium persulfate, 0.025% and sodium bisulfite, 0.025%;

[0109] (6) Density regulator: sodium chloride, 8%;

[0110] (7) Degradable polymer polyester particles: polyethylene adipate, 15%;

[0111] (8) The balance is water.

[0112] This embodiment also provides a method for preparing the above-mentioned soluble liquid bridge plug, comprising the following steps:

[0113] S1, mixing and first stirring the temperature-resistant and salt-resistant monomer, acrylamide monomer, degradable polymer polyester particles, a cross-linking agent and a retarder to obtain a prefabricated liquid;

[0114] S2, mixing the prefabricated liquid and the initiator, and stirring the mixture to obtain a polymer solution;

[0115] S3, mixing the polymer with a density regulator, and adjusting the temperature to 50° C. to obtain the soluble liquid bridge plug.

[0116] Wherein: the stirring frequency of the first stirring is 30 r / min, and the stirring time of the first stirring is 30 min. The stirring frequency of the second stirring is 30 r / min, and the stirring time of the second stirring is 5 min.

[0117] Example 3

[0118] This embodiment provides a soluble liquid bridge plug, the raw materials of which include, by mass percentage:

[0119] (1) Temperature-resistant and salt-resistant monomer: N-vinylamide, 3%;

[0120] (2) Acrylamide monomers: acrylamide, 8%;

[0121] (3) Cross-linking agent: N,N'-methylenebisacrylamide, 0.04%;

[0122] (4) Retarder: lignin sulfonate, 0.03%;

[0123] (5) Initiator: ammonium persulfate, 0.015% and sodium bisulfite, 0.015%;

[0124] (6) Density regulator: potassium chloride, 6%;

[0125] (7) Degradable polymer polyester particles: polylactic acid-glycolic acid copolymer, 10%;

[0126] (8) The balance is water.

[0127] This embodiment also provides a method for preparing the above-mentioned soluble liquid bridge plug, comprising the following steps:

[0128] S1, mixing and first stirring the temperature-resistant and salt-resistant monomer, acrylamide monomer, degradable polymer polyester particles, a cross-linking agent and a retarder to obtain a prefabricated liquid;

[0129] S2, mixing the prefabricated liquid and the initiator, and stirring the mixture to obtain a polymer solution;

[0130] S3, mixing the polymer with a density regulator and adjusting the temperature to 25° C. to obtain the soluble liquid bridge plug.

[0131] Wherein: the stirring frequency of the first stirring is 10 r / min, and the stirring time of the first stirring is 30 min. The stirring frequency of the second stirring is 10 r / min, and the stirring time of the second stirring is 5 min.

[0132] Example 4

[0133] This embodiment provides a soluble liquid bridge plug, the raw materials of which include, by mass percentage:

[0134] (1) Temperature-resistant and salt-resistant monomer: AMPS-Na, 4%;

[0135] (2) Acrylamide monomers: methacrylamide, 7%;

[0136] (3) Cross-linking agent: N,N'-methylenebisacrylamide, 0.04%;

[0137] (4) Retarder: borax, 0.04%;

[0138] (5) Initiator: ammonium persulfate, 0.02% and sodium bisulfite, 0.02%;

[0139] (6) Density regulator: potassium chloride, 5%;

[0140] (7) Degradable polymer polyester particles: polyglycolic acid, 8%;

[0141] (8) The balance is water.

[0142] This embodiment also provides a method for preparing the above-mentioned soluble liquid bridge plug, comprising the following steps:

[0143] S1, mixing and first stirring the temperature-resistant and salt-resistant monomer, acrylamide monomer, degradable polymer polyester particles, a cross-linking agent and a retarder to obtain a prefabricated liquid;

[0144] S2, mixing the prefabricated liquid and the initiator, and stirring the mixture to obtain a polymer solution;

[0145] S3, mixing the polymer with a density regulator, and adjusting the temperature to 25° C. to obtain the soluble liquid bridge plug.

[0146] Wherein: the stirring frequency of the first stirring is 20 r / min, and the stirring time of the first stirring is 30 min. The stirring frequency of the second stirring is 20 r / min, and the stirring time of the second stirring is 5 min.

[0147] Example 5

[0148] This embodiment provides a soluble liquid bridge plug, the raw materials of which include, by mass percentage:

[0149] (1) Temperature-resistant and salt-resistant monomer: AMPS-Na, 2%;

[0150] (2) Acrylamide monomer: methacrylamide, 6%;

[0151] (3) Cross-linking agent: N,N'-methylenebisacrylamide, 0.03%;

[0152] (4) Retarder: organic acid, 0.03%;

[0153] (5) Initiator: ammonium persulfate, 0.015% and sodium bisulfite, 0.015%;

[0154] (6) Density regulator: potassium chloride, 6%;

[0155] (7) Degradable polymer polyester particles: polylactic acid, 7%;

[0156] (8) The balance is water.

[0157] This embodiment also provides a method for preparing the above-mentioned soluble liquid bridge plug, comprising the following steps:

[0158] S1, mixing and first stirring the temperature-resistant and salt-resistant monomer, acrylamide monomer, degradable polymer polyester particles, a cross-linking agent and a retarder to obtain a prefabricated liquid;

[0159] S2, mixing the prefabricated liquid and the initiator, and stirring the mixture to obtain a polymer solution;

[0160] S3, mixing the polymer with a density regulator and adjusting the temperature to 25° C. to obtain the soluble liquid bridge plug.

[0161] Wherein: the stirring frequency of the first stirring is 18 r / min, and the stirring time of the first stirring is 30 min. The stirring frequency of the second stirring is 18 r / min, and the stirring time of the second stirring is 5 min.

[0162] Example 6

[0163] This embodiment provides a soluble liquid bridge plug, the raw materials of which include, by mass percentage:

[0164] (1) Temperature-resistant and salt-resistant monomer: AMPS-Na, 3%;

[0165] (2) Acrylamide monomers: methacrylamide, 7%;

[0166] (3) Cross-linking agent: N,N'-methylenebisacrylamide, 0.03%;

[0167] (4) Retarder: potassium ferrocyanide, 0.04%;

[0168] (5) Initiator: ammonium persulfate, 0.01% and sodium bisulfite, 0.01%;

[0169] (6) Density regulator: sodium chloride, 7%;

[0170] (7) Degradable polymer polyester particles: polycaprolactone, 10%;

[0171] (8) The balance is water.

[0172] This embodiment also provides a method for preparing the above-mentioned soluble liquid bridge plug, comprising the following steps:

[0173] S1, mixing and first stirring the temperature-resistant and salt-resistant monomer, acrylamide monomer, degradable polymer polyester particles, a cross-linking agent and a retarder to obtain a prefabricated liquid;

[0174] S2, mixing the prefabricated liquid and the initiator, and stirring the mixture to obtain a polymer solution;

[0175] S3, mixing the polymer with a density regulator, and adjusting the temperature to 25° C. to obtain the soluble liquid bridge plug.

[0176] Wherein: the stirring frequency of the first stirring is 6 r / min, and the stirring time of the first stirring is 30 min. The stirring frequency of the second stirring is 30 r / min, and the stirring time of the second stirring is 5 min.

[0177] Example 7

[0178] This embodiment provides a soluble liquid bridge plug, the raw materials of which include, by mass percentage:

[0179] (1) Temperature-resistant and salt-resistant monomer: N-vinyl pyrrolidone, 4%;

[0180] (2) Acrylamide monomers: acrylamide, 8%;

[0181] (3) Cross-linking agent: N,N'-methylenebisacrylamide, 0.04%;

[0182] (4) Retarder: organic acid, 0.04%;

[0183] (5) Initiator: ammonium persulfate, 0.02% and sodium bisulfite, 0.02%;

[0184] (6) Density regulator: sodium chloride, 10%;

[0185] (7) Degradable polymer polyester particles: polysuccinate, 8%;

[0186] (8) The balance is water.

[0187] This embodiment also provides a method for preparing the above-mentioned soluble liquid bridge plug, comprising the following steps:

[0188] S1, mixing and first stirring the temperature-resistant and salt-resistant monomer, acrylamide monomer, degradable polymer polyester particles, a cross-linking agent and a retarder to obtain a prefabricated liquid;

[0189] S2, mixing the prefabricated liquid and the initiator, and stirring the mixture to obtain a polymer solution;

[0190] S3, mixing the polymer with a density regulator and adjusting the temperature to 25° C. to obtain the soluble liquid bridge plug.

[0191] Wherein: the stirring frequency of the first stirring is 30 r / min, and the stirring time of the first stirring is 30 min. The stirring frequency of the second stirring is 6 r / min, and the stirring time of the second stirring is 5 min.

[0192] Example 8

[0193] This embodiment provides a soluble liquid bridge plug, the raw materials of which include, by mass percentage:

[0194] (1) Temperature-resistant and salt-resistant monomer: N-vinylamide, 2%;

[0195] (2) Acrylamide monomer: methacrylamide, 6%;

[0196] (3) Cross-linking agent: N,N'-methylenebisacrylamide, 0.03%;

[0197] (4) Retarder: disodium ethylenediamine acetate, 0.03%;

[0198] (5) Initiator: ammonium persulfate, 0.015% and sodium bisulfite, 0.015%;

[0199] (6) Density regulator: potassium chloride, 10%;

[0200] (7) Degradable polymer polyester particles: polylactic acid-glycolic acid copolymer, 9%;

[0201] (8) The balance is water.

[0202] This embodiment also provides a method for preparing the above-mentioned soluble liquid bridge plug, comprising the following steps:

[0203] S1, mixing and first stirring the temperature-resistant and salt-resistant monomer, acrylamide monomer, degradable polymer polyester particles, a cross-linking agent and a retarder to obtain a prefabricated liquid;

[0204] S2, mixing the prefabricated liquid and the initiator, and stirring the mixture to obtain a polymer solution;

[0205] S3, mixing the polymer with a density regulator and adjusting the temperature to 25° C. to obtain the soluble liquid bridge plug.

[0206] Wherein: the stirring frequency of the first stirring is 6 r / min, and the stirring time of the first stirring is 30 min. The stirring frequency of the second stirring is 6 r / min, and the stirring time of the second stirring is 5 min.

[0207] Comparative Example 1

[0208] This comparative example provides a soluble liquid bridge plug, the raw materials of which include, by mass percentage:

[0209] (1) Temperature-resistant and salt-resistant monomer: N-vinylamide, 0.5%;

[0210] (2) Acrylamide monomer: methacrylamide, 5%;

[0211] (3) Cross-linking agent: N,N'-methylenebisacrylamide, 0.05%;

[0212] (4) Retarder: disodium ethylenediamine acetate, 0.01%;

[0213] (5) Initiator: ammonium persulfate, 0.015% and sodium bisulfite, 0.015%;

[0214] (6) Density regulator: potassium chloride, 6%;

[0215] (7) Degradable polymer polyester particles: polylactic acid-glycolic acid copolymer, 15%;

[0216] (8) The balance is water.

[0217] Experimental Example 1

[0218] The dehydration performance of the soluble liquid bridge plugs of Example 3 and Comparative Example 1 was tested at different salinities. The test results are shown in Table 1.

[0219] The detection method is: add oilfield reinjection wastewater with different mineralizations into the soluble liquid bridge plug to prepare a mixed solution with a water content of 60% and a concentration of 10%, so that the mineralization of the system is 3000mg / L, 6000mg / L, 10000mg / L, 15000mg / L, 50000mg / L, 100000mg / L, 200000mg / L, and 250000mg / L, respectively, observe the dehydration rate after 48 hours, and examine the mineralization resistance performance.

[0220] Table 1 Dehydration of soluble liquid bridge plugs at different salinities at 90℃

[0221]

[0222] It can be seen from Table 1 that, according to the comparison between Example 3 and Comparative Example 1, the soluble liquid bridge plug of Example 3 has obvious advantages in salt resistance compared with the bridge plug of Comparative Example 1, and its maximum mineralization resistance is up to 20000 mg / L, which can meet the needs of on-site profile control, water plugging and drive adjustment in high-salinity oil reservoirs.

[0223] Experimental Example 2

[0224] The thermal stability of the soluble liquid bridge plugs of Example 4 and Comparative Example 1 was tested, and the test results are shown in Table 2.

[0225] The detection method is: add oilfield reinjection wastewater with different mineralization degrees into the soluble liquid bridge plug to prepare a mixed solution with 60% water content and 10% concentration, and observe the state after one week in a constant temperature box under different temperature conditions.

[0226] Table 2 Thermal stability of soluble liquid bridge plugs under different temperature conditions

[0227]

[0228] It can be seen from Table 2 that, according to the comparison between Example 4 and Comparative Example 1, the soluble liquid bridge plug of Example 4 has obvious advantages in temperature resistance compared with the bridge plug of Comparative Example 1, and the maximum temperature resistance can reach 150°C, which can adapt to domestic high-temperature oil reservoir conditions.

[0229] Experimental Example 3

[0230] By using the core simulation displacement experiment, the permeability of the core was tested before and after plugging with the soluble liquid bridge plugs of Example 5 and Comparative Example 1, and the plugging strength of the soluble liquid bridge plug was investigated. The test results are shown in Table 3.

[0231] Table 3 Plugging strength performance of soluble liquid bridge plug

[0232]

[0233] It can be seen from Table 3 that, according to the comparison between Example 5 and Comparative Example 1, the soluble liquid bridge plug of Example 5 has obvious advantages in plugging performance compared with the bridge plug of Comparative Example 1, and the breakthrough pressure gradient reaches 22 MPa / m, which can meet the water plugging requirements of horizontal wells.

[0234] Experimental Example 4

[0235] The thermal stability of the soluble liquid bridge plugs of Example 6 and Comparative Example 1 was tested, and the test results are shown in Table 4.

[0236] The detection method is: add different concentrations of different breakers into the soluble liquid bridge plug, soak it for 48 hours, and then observe its dehydration.

[0237] Table 4 Degelling properties of soluble liquid bridge plugs at different concentrations

[0238]

[0239] It can be seen from Table 4 that, according to the comparison between Example 6 and Comparative Example 1, the soluble liquid bridge plug of Example 6 has obvious advantages in gel breaking performance compared with the bridge plug of Comparative Example 1. It is easily oxidized and degraded to become a low-viscosity aqueous solution, which can meet the subsequent production and timely flowback requirements of horizontal well water plugging operations.

[0240] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0241] (1) A soluble liquid bridge plug provided in an embodiment of the present invention is an excellent plugging agent that is environmentally friendly, low-cost, has little pollution to the formation, is non-toxic, and has a simple preparation process. Compared with existing plugging agents, it has good injectability and temperature and salt resistance, a temperature resistance of up to 150°C, a mineralization resistance of up to 200,000 mg / l, and a breakthrough pressure gradient of 22 MPa / m, which meets the requirements of water plugging and profile control for horizontal wells in different types of oil reservoirs such as sandstone and carbonate rock; and it uses less raw materials on site, has low cost, is non-flammable, is safe to operate, is suitable for industrial production, has no stringent requirements on water quality, and is non-toxic and non-volatile when used on site.

[0242] (2) The horizontal well segmented water plugging method provided in the embodiment of the present invention utilizes soluble liquid bridge plugs for segmentation, and utilizes the gelling and degelling properties of the soluble liquid bridge plugs to achieve segmentation at any position inside or outside the horizontal well pipe through positioning injection, quantitative injection and other means, thereby achieving segmented water plugging of the horizontal well; this method is not only suitable for casing perforation completion or open hole perforation completion, but is particularly suitable for screen tube completion horizontal wells that are difficult to implement segmented water plugging; utilizing the temporary plugging performance of the soluble liquid bridge plug, the oil layer is protected during the water plugging process, greatly reducing the construction risk.

[0243] Finally, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article, or apparatus.

[0244] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0245] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A soluble liquid bridge plug, characterized in that: The raw material composition is as follows: by mass percentage: 1-5% of heat-resistant and salt-resistant monomer, 6-10% of acrylamide monomer, 5-15% of degradable polymer polyester particles, 0.02-0.06% of cross-linking agent, 0.02-0.05% of retarder, 0.02-0.05% of initiator and 2-8% of density regulator, and the balance is water; The temperature-resistant and salt-resistant monomers include any one or more combinations of AMPS-Na, N-vinyl pyrrolidone and N-vinylamide; The acrylamide monomers include acrylamide or methacrylamide; The degradable polymer polyester particles include any one or more combinations of polyurethane, polylactic acid, polyglycolic acid, polylactic acid-glycolic acid copolymer, polycaprolactone, polysuccinate and polyethylene adipate; The initiator includes ammonium persulfate and sodium bisulfite in a mass ratio of 1:1; The density regulator includes potassium chloride or sodium chloride.

2. The soluble liquid bridge plug according to claim 1, characterized in that: The cross-linking agent is N,N'-methylenebisacrylamide.

3. The soluble liquid bridge plug according to claim 1, characterized in that: The retarder is any one or more combinations of potassium ferrocyanide, lignin sulfonate, borax, organic acid and disodium ethylenediamine acetate.

4. A method for preparing a soluble liquid bridge plug according to any one of claims 1 to 3, characterized in that: The steps include: The heat-resistant and salt-resistant monomer, the acrylamide monomer, the degradable polymer polyester particles, the cross-linking agent and the retarder are mixed and first stirred to obtain a prefabricated liquid; The prefabricated liquid and the initiator are mixed and stirred for a second time to obtain a polymer solution; The polymer is mixed with a density regulator and the temperature is adjusted to 20-50° C. to obtain the soluble liquid bridge plug.

5. The preparation method according to claim 4, characterized in that: The stirring frequency of the first stirring is 6-30 r / min, and the stirring time of the first stirring is 30 min.

6. The preparation method according to claim 4, characterized in that: The stirring frequency of the second stirring is 6-30 r / min, and the stirring time of the second stirring is 5 min.

7. A horizontal well segmented water plugging method, characterized in that: The steps include: Divide the horizontal section of the horizontal well into sections to obtain multiple test production sections; Conducting trial production on each of the trial production sections in turn to obtain a water-yielding target section; Injecting the soluble liquid bridge plug as described in any one of claims 1 to 3 into the horizontal section to fill the horizontal section; Using water drive to replace the soluble liquid bridge plug in the water production target section and waiting for solidification; Injecting a water plugging agent into the target water outlet section for plugging; Steam or a breaker is injected into the horizontal section to remove the soluble liquid bridge plug.

8. The horizontal well segmented water plugging method according to claim 7, characterized in that: The debonding agent includes hydrogen peroxide solution or potassium permanganate solution.

9. The horizontal well segmented water plugging method according to claim 7, characterized in that: The concentration of the breaker is 5-10%, and the dosage of the breaker is 20-60m 3 / m.

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