A rosin-modified fiber temporary plugging agent and its preparation method and application

Abstract

The invention discloses a rosin-modified fiber temporary plugging agent, a preparation method and an application thereof. The rosin-modified fiber temporary plugging agent comprises: rosin-modified fiber, rosin-modified calcium carbonate powder, and a water-soluble high molecular polymer. The preparation method of the rosin-modified fiber comprises: step S1: firstly sizing and modifying a degradable fiber by a rosin sizing method to improve its strength, inhibit water permeability, and enhance its temporary plugging function; step S2: uniformly mixing rosin powder with the modified degradable fiber obtained in step S1, and then pressurizing, rubbing and kneading to obtain a final modified degradable fiber, so as to achieve coating of rosin dry powder on the fiber surface to increase the friction between the fibers; and mixing the rosin-modified fiber temporary plugging agent with a fracturing fluid thickener, and then adding water to adjust the viscosity to obtain a fiber temporary plugging fracturing fluid. The fracturing fluid has the advantages of excellent plugging performance, easy unblocking, and the like, and has great potential for on-site promotion.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas well fracturing temporary plugging engineering, and in particular to a rosin-modified fiber temporary plugging agent, a preparation method and an application thereof. Background Art

[0002] As oil gradually enters the later stage, the reservoir energy contained in the oil field will naturally show a shrinking trend, which will significantly reduce the oil field production. The use of fracturing methods to increase oil and gas production has become an important means to solve this problem. In addition, for low-permeability and ultra-low-permeability oil and gas reservoirs with relatively complex formation structures, the use of fracturing methods to change the distribution of cracks can significantly help improve the output rate of oil and gas reservoirs. In the fracturing transformation, in order to achieve the best fracturing effect, it is often necessary to perform temporary plugging operations at the corresponding positions in the formation according to construction requirements to seal the original cracks, so as to achieve fracturing at specific positions in the wellbore and reduce the invasion of the working fluid into the formation. After the fracturing work is completed, the temporary plugging agent can also be unplugged to avoid reservoir damage caused by temporary plugging agent residues.

[0003] Chinese patent CN101311243A discloses a temporary plugging agent for fractured oil and gas reservoirs. Its components are: 40-85% 60-1100 mesh ultrafine calcium carbonate, 10-40% plant fiber, and 5-20% oxidized asphalt. After entering the formation along with the drilling fluid, the temporary plugging agent rapidly forms a dense, resilient mud cake near the wellbore wall, rapidly reducing the original permeability of the formation near the wellbore wall to near zero. This temporary plugging agent achieves a temporary plugging rate of over 99% for fractured cores, and over 80% for pressure and acidizing flowback. Its wide temporary plugging range makes it an ideal protective agent for fractured reservoirs.

[0004] Chinese patent CN109554172 A discloses an acid fracturing temporary plugging agent and its application. The formulation of the acid fracturing temporary plugging agent comprises, by weight, 0.1-3% temporary plugging fiber, 0.05-3% non-expandable temporary plugging balls A, 0.1-3% expandable temporary plugging balls B, 0.1-1% support sand, 0.05-1% dispersant, and the balance being carrier fluid. This acid fracturing temporary plugging agent exhibits excellent compatibility with formation fluids, good chemical stability, a high plugging efficiency, and complete dissolution, making it suitable for high-temperature carbonate reservoirs.

[0005] The prior art discloses a variety of temporary plugging agents that can be used in the field of oil production. However, there is still room for improvement in these temporary plugging agents. The main issues are: the degradation rate of materials such as degradable fibers in the prior art is too fast, making it impossible to achieve the effect of properly plugging the target layer; the temporary plugging strength is also low. It is necessary to have excellent plugging strength while avoiding certain types of temporary plugging agents from damaging the formation. Furthermore, in order to achieve the required plugging strength, the temporary plugging agents in the prior art are added in excessive amounts, which can easily damage the formation. Therefore, a new temporary plugging agent is needed that meets the following functions:

[0006] 1. Reduce the water permeability of degradable fibers, so that their water permeability is reduced under high pressure, which helps to form a high-strength filter cake in the formation, thereby reducing the amount of fiber used;

[0007] 2. Increase the strength of the degradable fiber, so that its bridging ability after entering the formation is increased, and the skeleton formed after bridging is stronger (similar to the steel frame structure). At the same time, it works synergistically with particles such as modified calcium carbonate to form a high-strength filter cake and temporary plugging layer through surface modification, so that the temporary plugging agent can form a high-strength temporary plugging layer with longer duration, indirectly reducing the amount of fiber used;

[0008] 3. Enhance the friction strength between degradable fibers. When the fibers enter the temporary plugging target position, the friction strength between the fibers increases the friction between the fibers and between the fibers and the formation, which is beneficial for the fibers to stay at the temporary plugging target position and is not easy to enter the formation or be lost. The increased friction helps to keep the bridging skeleton between the fibers, that is, between the fibers and the rock particles more stable under high-pressure water flow (similar to the weaving effect). At the same time, it cooperates with the particulate matter to form a temporary plugging layer with higher temporary plugging strength, indirectly reducing the amount of fiber used, that is, a smaller amount of fiber can achieve a temporary plugging strength equivalent to that in the existing technology, which is beneficial to reservoir protection and rapid unblocking, and also has better economic benefits. Summary of the Invention

[0009] The purpose of the present invention is to provide a rosin modified fiber temporary plugging agent and its preparation method and application, so as to solve the technical problems in the prior art of temporary plugging agents such as rapid degradation, excessive addition, low plugging strength, incomplete plugging and damage to oil layers.

[0010] To achieve the above objectives, the present invention provides the following technical solutions:

[0011] The present invention provides a rosin-modified fiber temporary plugging agent, which comprises the following components in parts by mass: 20-35 parts of rosin-modified fiber, 20-40 parts of rosin-modified calcium carbonate powder, and 5-20 parts of water-soluble high molecular polymer; the fiber is a degradable plant fiber.

[0012] Furthermore, the degradable plant fibers include bamboo, cotton, and wood fibers; the length of the degradable plant fibers is 3-10 mm, and the fiber diameter is 0.1-0.5 mm.

[0013] Furthermore, the rosin-modified fiber temporary plugging agent is suitable for plugging oil reservoirs with a reservoir temperature of 100° C. or above.

[0014] Furthermore, the specific preparation method of the rosin-modified fiber includes the following steps:

[0015] Step S1: First, the biodegradable fiber is modified by sizing with rosin to improve its strength, inhibit water permeability, and enhance its temporary blocking function:

[0016] 1) Prepare rosin alcohol solution: Grind rosin into 100-500 mesh and add to anhydrous ethanol with a mass ratio of anhydrous ethanol to rosin powder of 8-10:2-3. Let stand for 2 days until completely dissolved.

[0017] 2) Sizing and modifying the degradable fiber: soaking the degradable plant fiber in the rosin alcohol solution obtained in step 1), picking it up after it is completely soaked, and volatilizing the ethanol at 40-60° C. to obtain a dry sizing-modified degradable plant fiber, then washing the sizing-modified degradable plant fiber with water to completely remove the residual ethanol in the fiber, heating the washed fiber to 110-145° C. to melt the rosin, maintaining the temperature for 1-3 minutes, and allowing the melted rosin to fill the internal gaps of the plant fiber to improve its strength and inhibit water permeability, and then cooling the fiber to 25° C. to obtain the rosin-sizing-modified degradable plant fiber;

[0018] Step S2: Evenly mix rosin powder with the biodegradable plant fiber modified by rosin sizing obtained in step S1, and then pressurize, rub, and knead to obtain the final rosin-modified fiber. Apply rosin dry powder to the fiber surface to increase the friction between the fibers.

[0019] 1) grinding rosin into a powder of 20-100 mesh, and uniformly mixing the ground rosin powder and the degradable plant fiber modified by rosin sizing obtained in step S1, wherein the volume ratio of rosin to the degradable plant fiber modified by rosin sizing obtained in step S1 is 0.5:1-1:1;

[0020] 2) Place the mixed biodegradable plant fibers between two hard boards with rough surfaces and apply pressure to 5kg / m 2 -30kg / m 2 ; Fix the lower hard plate and rub and knead the upper hard plate back and forth, with a left and right swinging and rubbing frequency of 30-60 times per minute; the rubbing and kneading time is 10-30 minutes, and a small amount of plant fiber is taken out every 5-10 minutes, and rubbed in the hands. If the fiber feels hard and astringent due to friction, the rubbing and kneading is stopped early; separate the rosin modified fiber and the rosin powder to obtain the rosin modified fiber.

[0021] Furthermore, the rosin-modified calcium carbonate powder has a mesh size of 100-500 before modification and is crushed to a mesh size of 100-500 after modification;

[0022] The specific steps are:

[0023] The calcium carbonate is crushed into 100-500 mesh and spread on a 200-250°C plate. The rosin is heated and melted, and then sprayed onto the surface of the calcium carbonate powder while maintaining the temperature to make it soak the calcium carbonate powder. The amount of rosin sprayed is 20%-30% of the mass of the calcium carbonate powder. After soaking the calcium carbonate powder, the plate is kept vibrating and the calcium carbonate particles are continuously turned to cool down. The temperature is maintained at 80-140°C for 30-90 minutes, and then cooled to room temperature to allow the rosin to crystallize and solidify on the surface of the calcium carbonate. The solidified rosin-modified calcium carbonate powder is crushed and sieved, and a 100-500 mesh powder is screened to obtain the rosin-modified calcium carbonate powder.

[0024] Furthermore, the water-soluble high molecular polymer is polyacrylamide with a molecular weight of 10 to 25 million.

[0025] Furthermore, the preparation method of the rosin-modified fiber temporary plugging agent is as follows: before use, the rosin-modified fiber, rosin-modified calcium carbonate powder, and water-soluble high molecular polymer are uniformly mixed.

[0026] The application of rosin modified fiber temporary plugging agent includes application in fracturing fluid. The temporary plugging fracturing fluid is suitable for plugging oil reservoirs with a reservoir temperature above 100°C. The fracturing fluid also includes a thickener and water. The thickener is a water-soluble high molecular polymer or guar gum.

[0027] Furthermore, the mass concentration of the rosin modified fiber temporary plugging agent in the fracturing fluid is 0.5-3%.

[0028] Furthermore, the viscosity of the fracturing fluid is 100-300 mPa.s, and the temporary plugging fracturing fluid also includes a pH regulator, a clay stabilizer, a drainage aid, a bactericide, a foaming agent, a defoaming agent, a cross-linking agent, a gel breaker and a demulsifier.

[0029] Based on the above technical solution, the embodiments of the present invention can produce at least the following technical effects:

[0030] (1) By modifying the sizing of biodegradable fibers with rosin, the water permeability of the biodegradable fibers is reduced, so that the water permeability under high pressure is reduced, which helps to form a high-strength filter cake in the formation, increases the temporary plugging strength of the temporary plugging agent, and thus reduces the amount of fiber used;

[0031] (2) By modifying the sizing of degradable fibers with rosin, the strength of the degradable fibers is increased, so that the bridging ability of the fibers after entering the formation is increased, and the skeleton strength formed after bridging is higher (similar to the steel frame structure). At the same time, the fibers work synergistically with particles such as modified calcium carbonate to form a high-strength filter cake and temporary plugging layer by surface modification, so that the temporary plugging agent can form a high-strength temporary plugging layer, the degradation duration is longer, and the fiber usage is indirectly reduced;

[0032] (3) By coating the fiber surface with rosin, the friction strength between the degradable fibers is enhanced. When the fibers enter the temporary plugging target position, the friction strength between the fibers increases the friction between the fibers and between the fibers and the formation, which is conducive to the fibers staying at the temporary plugging target position and not easily entering the formation or being lost. The increased friction helps to keep the bridging skeleton between the fibers and between the fibers and the rock particles more stable under high-pressure water flow (similar to the weaving effect to increase friction). At the same time, it cooperates with the particles to form a temporary plugging layer with higher temporary plugging strength, indirectly reducing the amount of fiber used, that is, a smaller amount of fiber can achieve a temporary plugging strength equivalent to that in the existing technology, which is beneficial to reservoir protection and rapid unblocking, and also has better economic benefits.

[0033] (4) Calcium carbonate powder particles are modified by rosin, and a layer of rosin crystal particles is covered on the surface of the calcium carbonate powder through a special process, which greatly increases the suspension performance and friction performance of the calcium carbonate particles. The synergistic effect of the rosin modified fiber greatly enhances the friction strength between the fiber and the calcium carbonate particles. The synergistic effect of the rosin modified fiber with low permeability, high strength and increased friction force forms a temporary plugging layer with higher temporary plugging strength and controllable degradation rate, so that a higher plugging strength can be achieved with a smaller amount of fiber added. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] Example 1

[0040] The temporary plugging agent in this embodiment is composed of 20 parts by weight of rosin-modified fiber, 20 parts by weight of rosin-modified calcium carbonate powder, and 5 parts by weight of a water-soluble polymer. The degradable plant fiber is a mixture of bamboo, cotton, and wood fibers; the length of the degradable plant fiber is 10 mm and the fiber diameter is 0.5 mm. The water-soluble polymer is polyacrylamide with a molecular weight of 25 million.

[0041] The specific preparation method of rosin modified fiber comprises the following steps:

[0042] Step S1: First, the biodegradable fiber is modified by sizing with rosin to improve its strength, inhibit water permeability, and enhance its temporary blocking function:

[0043] 1) Prepare rosin alcohol solution: Grind rosin into 100 mesh and add to anhydrous ethanol with a mass ratio of anhydrous ethanol to rosin powder of 8:3. Let stand for 2 days until completely dissolved.

[0044] 2) Sizing and modifying the degradable fiber: soaking the degradable plant fiber in the rosin alcohol solution obtained in step 1), picking it up after it is completely soaked, and volatilizing the ethanol at 40° C. to obtain a dry sizing-modified degradable plant fiber, then washing the sizing-modified degradable plant fiber with water to completely remove the residual ethanol in the fiber, heating the washed fiber to 110-145° C. to melt the rosin, maintaining the temperature for 1 minute, and allowing the melted rosin to fill the internal gaps of the plant fiber to improve its strength and inhibit water permeability, and then cooling it to 25° C. to obtain the rosin-sizing-modified degradable plant fiber;

[0045] Step S2: Evenly mix rosin powder with the biodegradable plant fiber modified by rosin sizing obtained in step S1, and then pressurize, rub, and knead to obtain the final rosin-modified fiber. Apply rosin dry powder to the fiber surface to increase the friction between the fibers.

[0046] 1) grinding rosin into 20-mesh powder, and uniformly mixing the ground rosin powder and the degradable plant fiber modified by rosin sizing obtained in step S1, wherein the volume ratio of rosin to the degradable plant fiber modified by rosin sizing obtained in step S1 is 0.5:1;

[0047] 2) placing the evenly mixed degradable plant fibers between two hard plates with rough surfaces and applying a pressure of 30 kg / m2; fixing the lower hard plate and rubbing the upper hard plate back and forth at a frequency of 30 times per minute; rubbing and kneading for 30 minutes to separate the rosin-modified fibers and the rosin powder; thereby obtaining the rosin-modified fibers.

[0048] The rosin modified calcium carbonate powder was 100 mesh before modification and was crushed to 100 mesh after modification;

[0049] The specific steps are:

[0050] Calcium carbonate is crushed into 100 mesh and spread on a 200°C plate. Rosin is heated and melted, and then sprayed onto the surface of the calcium carbonate powder while maintaining the temperature to allow it to soak the calcium carbonate powder. The amount of rosin sprayed is 20% of the mass of the calcium carbonate powder. After soaking the calcium carbonate powder, the plate is kept vibrating and the calcium carbonate particles are continuously turned to cool down. The temperature is maintained at 80-140°C for 90 minutes, and then cooled to room temperature to allow the rosin to crystallize and solidify on the surface of the calcium carbonate. The solidified rosin-modified calcium carbonate powder is crushed and sieved, and a 100-mesh powder is screened to obtain the rosin-modified calcium carbonate powder.

[0051] Before use, the prepared rosin-modified fiber, rosin-modified calcium carbonate powder and water-soluble high molecular polymer are uniformly mixed to obtain the rosin-modified fiber temporary plugging agent.

[0052] Preparation of temporary plugging fracturing fluid: The thickener in the temporary plugging fracturing fluid is guar gum. After dilution with water, the viscosity is approximately 100 mPa.s. Functional additives such as pH adjusters, clay stabilizers, drainage aids, fungicides, foaming agents, defoamers, crosslinking agents, gel breakers, and demulsifiers may also be added as needed. The prepared rosin-modified fiber temporary plugging agent is then added to a concentration of 0.5% by mass in the fracturing fluid. After slight stirring and dispersing, temporary plugging fracturing fluid 1 is obtained.

[0053] Example 2

[0054] The temporary plugging agent in this embodiment is composed of 35 parts by mass of rosin-modified fiber, 40 parts by mass of rosin-modified calcium carbonate powder, and 20 parts by mass of a water-soluble polymer. The degradable plant fiber is a mixture of bamboo, cotton, and wood fibers; the length of the degradable plant fiber is 3 mm and the fiber diameter is 0.1 mm. The water-soluble polymer is polyacrylamide with a molecular weight of 11 million.

[0055] The specific preparation method of rosin modified fiber comprises the following steps:

[0056] Step S1: First, the biodegradable fiber is modified by sizing with rosin to improve its strength, inhibit water permeability, and enhance its temporary blocking function:

[0057] 1) Prepare rosin alcohol solution: Grind rosin into 500 mesh and add to anhydrous ethanol with a mass ratio of anhydrous ethanol to rosin powder of 10:2. Let stand for 2 days until completely dissolved.

[0058] 2) Sizing and modifying the degradable fiber: soaking the degradable plant fiber in the rosin alcohol solution obtained in step 1), picking it up after it is completely soaked, and volatilizing the ethanol at 60° C. to obtain a dry sizing-modified degradable plant fiber, then washing the sizing-modified degradable plant fiber with water to completely remove the residual ethanol in the fiber, heating the washed fiber to 110-145° C. to melt the rosin, maintaining the temperature for 3 minutes, and allowing the melted rosin to fill the internal gaps of the plant fiber to improve its strength and inhibit water permeability, and then cooling it to 25° C. to obtain the rosin-sizing-modified degradable plant fiber;

[0059] Step S2: Evenly mix rosin powder with the biodegradable plant fiber modified by rosin sizing obtained in step S1, and then pressurize, rub, and knead to obtain the final rosin-modified fiber. Apply rosin dry powder to the fiber surface to increase the friction between the fibers.

[0060] 1) grinding rosin into 100-mesh powder, and uniformly mixing the ground rosin powder and the degradable plant fiber modified by rosin sizing obtained in step S1, wherein the volume ratio of rosin to the degradable plant fiber modified by rosin sizing obtained in step S1 is 1:1;

[0061] 2) placing the evenly mixed biodegradable plant fibers between two hard plates with rough surfaces and applying a pressure of 5 kg / m2; fixing the lower hard plate and rubbing the upper hard plate back and forth at a frequency of 60 times per minute; rubbing and kneading for 10 minutes to separate the rosin-modified fibers and the rosin powder; thereby obtaining the rosin-modified fibers.

[0062] The rosin modified calcium carbonate powder was 500 mesh before modification and was crushed to 500 mesh after modification;

[0063] The specific steps are:

[0064] Calcium carbonate is crushed into 500 mesh and spread on a 250°C plate. Rosin is heated and melted, and then sprayed onto the surface of the calcium carbonate powder while maintaining the temperature to allow it to soak the calcium carbonate powder. The amount of rosin sprayed is 30% of the mass of the calcium carbonate powder. After soaking the calcium carbonate powder, the plate is kept vibrating and the calcium carbonate particles are continuously turned over to cool down. The temperature is maintained at 80-140°C for 30 minutes, and then cooled to room temperature to allow the rosin to crystallize and solidify on the surface of the calcium carbonate. The solidified rosin-modified calcium carbonate powder is crushed and sieved, and a 500-mesh powder is screened to obtain the rosin-modified calcium carbonate powder.

[0065] Before use, the prepared rosin-modified fiber, rosin-modified calcium carbonate powder and water-soluble high molecular polymer are uniformly mixed to obtain the rosin-modified fiber temporary plugging agent.

[0066] Preparation of temporary plugging fracturing fluid: The thickener in the temporary plugging fracturing fluid is guar gum. After dilution with water, the viscosity is approximately 300 mPa·s. Functional additives such as pH adjusters, clay stabilizers, drainage aids, fungicides, foaming agents, defoamers, crosslinkers, gel breakers, and demulsifiers may also be added as needed. The prepared rosin-modified fiber temporary plugging agent is then added to a concentration of 3% by mass in the fracturing fluid. After slight stirring and suspension, temporary plugging fracturing fluid 2 is obtained.

[0067] Comparative Example 1

[0068] This comparative example has the same technical solution as that in Example 1, except that the sizing modification of the degradable fiber by the rosin sizing method in step S1 is omitted. The degradable plant fiber is directly mixed with the rosin powder and then pressurized, rubbed and kneaded to obtain the final rosin-modified fiber. The preparation methods of the remaining components are the same as those in Example 1. The method for preparing the temporary plugging fracturing fluid is the same as that in Example 1, and temporary plugging fracturing fluid 3 is obtained.

[0069] Comparative Example 2

[0070] This comparative example has the same technical solution as that in Example 1, except that the step S2 of uniformly mixing rosin powder with the degradable plant fiber modified by rosin sizing obtained in step S1 and then pressurizing, rubbing and kneading is omitted. The degradable plant fiber modified by rosin sizing obtained in step S1 is directly used as the final rosin-modified fiber. The preparation methods of the remaining components are the same as those in Example 1, and the method for preparing the temporary plugging fracturing fluid is the same as that in Example 1, to obtain temporary plugging fracturing fluid 4.

[0071] Comparative Example 3

[0072] This comparative example has the same technical solution as that in Example 1, except that the fiber modification processes of steps S1 and S2 are removed, and degradable plant fibers are directly used as the final temporary plugging fibers. The preparation methods of the remaining components are the same as those in Example 1, and the method for preparing the temporary plugging fracturing fluid is the same as that in Example 1, to obtain temporary plugging fracturing fluid 5.

[0073] Comparative Example 4

[0074] This comparative example has the same technical solution as that in Example 1, except that the rosin modification process of calcium carbonate powder is eliminated, and unmodified calcium carbonate powder is directly used as the temporary plugging agent component. The preparation methods of the remaining components are the same as those in Example 1, and the method for preparing the temporary plugging fracturing fluid is the same as that in Example 1, to obtain temporary plugging fracturing fluid 6.

[0075] Comparative Example 5

[0076] This comparative example is the same as the technical solution in Example 1, except that the preparation method of rosin-modified calcium carbonate powder is as follows:

[0077] The rosin modified calcium carbonate powder was 100 mesh before modification and was crushed to 100 mesh after modification;

[0078] The specific steps are:

[0079] The calcium carbonate is crushed into 100 mesh and spread on a 200° C. flat plate. The rosin is heated and melted, and then the temperature is maintained and sprayed on the surface of the calcium carbonate powder to make it soak the calcium carbonate powder. The amount of rosin sprayed is 20% of the mass of the calcium carbonate powder. After soaking the calcium carbonate powder, the flat plate is kept stable and not vibrated. The calcium carbonate particles are directly cooled. The cooling process quickly passes through the range of 80-140° C. (within 1 minute) and then is also cooled to room temperature. The rosin does not solidify in a crystallized state on the surface of the calcium carbonate, but forms a smooth rosin coating. The solidified rosin-modified calcium carbonate powder is crushed and sieved, and a 100-mesh powder is screened to obtain the rosin-modified calcium carbonate powder.

[0080] The preparation methods of the remaining components are the same as those in Example 1. The method for preparing the temporary plugging fracturing fluid is the same as that in Example 1, and a temporary plugging fracturing fluid 7 is obtained.

[0081] Comparative Example 6

[0082] This comparative example employs the same technical scheme as Example 1, except that the rosin-modified fiber in the rosin-modified fiber temporary plugging agent component is replaced with conventional biodegradable plant fiber, i.e., no modification step is performed. The rosin-modified calcium carbonate powder is replaced with calcium carbonate powder, i.e., no calcium carbonate powder modification is performed. The remaining components are prepared using the same methods as in Example 1, and the temporary plugging fracturing fluid is prepared using the same method as in Example 1, yielding Temporary Plugging Fracturing Fluid 8.

[0083] Temporary plugging performance evaluation of the above fracturing fluids 1-8:

[0084] 1. Sealing performance:

[0085] Prepare 8 sand-filled tubes, each of which is filled with 120-140 mesh quartz sand. The pure liquid obtained by filtering the solids in the above-mentioned fracturing fluids 1-8 multiple times is injected into the sand-filled tubes using a constant pressure mode (pressure of 20 MPa) to obtain a stable liquid flow rate K1 of the sand-filled tubes. The experimental temperature is 115°C.

[0086] Eight sand-filled tubes were prepared again, and each tube was filled with 120-140 mesh quartz sand. The experimental temperature was 115°C, and the above-mentioned full-component fracturing fluids 1-8 were respectively injected into the sand-filled tubes under constant pressure conditions (pressure was 20 MPa). The fluid flow rates of the sand-filled tubes were recorded over time, and the time T1 required for the flow rates of different sand-filled tubes to drop to 10% of the stable fluid flow rate K1 of the sand-filled tubes, that is, the time T1 required for the plugging rate to reach 90%, and the final stable fluid flow rate Q1 were observed.

[0087] 2. Sealing strength:

[0088] Eight sand-filled tubes were prepared, each filled with 120-140 mesh quartz sand. The experimental temperature was 115°C. Fracturing fluids 1-8 were injected into the sand-filled tubes at a constant pressure of 20 MPa. After the fluid flow rate from each sand-filled tube stabilized, the pressure was increased by 5 MPa every 30 minutes. The fluid flow rate at the sand-filled tube outlet was observed. When the fluid flow rate reached 50% of the sand-filled tube outlet flow rate K1, the plugging was considered broken, and the plugging pressure P1 at this time was recorded.

[0089] 3. Blockage removal performance:

[0090] In addition, 8 sand-filled pipes were prepared, and each sand-filled pipe was filled with 120-140 mesh quartz sand. The above-mentioned fracturing fluids 1-8 were respectively injected into the sand-filled pipes under constant pressure (pressure of 20 MPa), and the experimental temperature was 115°C. After the liquid flow rate of different sand-filled pipes stabilized, the pressure was maintained for 24 hours, and then acid was injected from the inlet of the sand-filled pipe under maintained pressure to replace the fracturing fluid at the inlet of the sand-filled pipe. The fracturing fluid at the inlet of the sand-filled pipe was discharged from another drain valve at the inlet of the sand-filled pipe. After the acid was soaked for 24 hours, the pure liquid after multiple filtration of the solids in the above-mentioned fracturing fluids 1-8 was re-injected. During this period, the liquid flow rate at the outlet of the sand-filled pipe was observed, and the final stable liquid flow rate of the sand-filled pipe was recorded. The ratio of the final stable liquid flow rate of the sand-filled pipe to the liquid flow rate K1 of the sand-filled pipe was the deblocking rate F1.

[0091] The experimental results are:

[0092] 1. Sealing performance

[0093]

[0094] The experimental results show that since the fiber treatment and calcium carbonate particle treatment of fracturing fluid 1 and fracturing fluid 2 are carried out in accordance with the technical solution of the present invention, the time taken to reach a plugging rate of 90% is significantly shorter than that of other fracturing fluids not treated in accordance with the technical solution disclosed in the present invention, and the final stable flow rate is also significantly lower than that of other fracturing fluids, indicating that there is a synergistic effect between their components. The rosin-modified fiber has low permeability and high strength, and the friction between fibers, between fibers and rock skeletons, and between fibers and modified calcium carbonate particles is greater, so that less fiber is needed to completely plug the formation, ensuring complete plugging of the target layer. Since the time to achieve plugging is shorter, the amount of fracturing fluid entering the plugged formation is smaller, and the damage to the target layer after complete plugging is less, and the plugging performance is more excellent.

[0095] 2. Sealing strength

[0096]

[0097] The experimental results show that since the fiber treatment and calcium carbonate particle treatment of fracturing fluid 1 and fracturing fluid 2 are carried out in accordance with the technical solution of the present invention, their plugging strength is significantly higher than that of other fracturing fluids. Due to the significant improvement in the water permeability, fiber strength and fiber friction strength of the rosin-modified fibers, the formed filter cake has a higher plugging strength under the synergy of the fiber skeleton and the rosin-modified calcium carbonate particles, which helps to keep the bridging skeleton between fibers and between fibers and rock particles more stable under high-pressure water flow (similar to the weaving effect to increase friction). At the same time, it cooperates with the particulate matter to form a filter cake temporary plugging layer with higher temporary plugging strength, thereby increasing the temporary plugging strength, thereby significantly reducing the amount of fiber, etc., and the plugging emphasis is high and has a wider application.

[0098] 3. Blockage-releasing performance

[0099] Fracturing fluid 1 Fracturing fluid 2 Fracturing fluid 3 Fracturing fluid 4 Fracturing fluid 5 Fracturing fluid 6 Fracturing fluid 7 Fracturing fluid 8 F1 98.4 98.7 98.6 97.9 98.3 98.9 97.1 99.2

[0100] The experimental results show that since the fiber treatment and calcium carbonate particle treatment of fracturing fluid 1 and fracturing fluid 2 are carried out in accordance with the technical solution of the present invention, their plugging removal performance is basically no different from that of other fracturing fluids, indicating that they have higher plugging strength and better plugging performance while also having excellent degradation and unblocking properties, which is conducive to on-site promotion and use.

[0101] All of the above-mentioned fracturing fluids may further include pH regulators, clay stabilizers, drainage aids, fungicides, foaming agents, defoamers, crosslinking agents, gel breakers and demulsifiers, which may be added according to the needs of those skilled in the art.

[0102] Finally, it should be noted that:

[0103] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rosin modified fiber temporary plugging agent, characterized in that: The rosin-modified fiber temporary plugging agent comprises the following components by mass: 20-35 parts of rosin-modified fiber, 20-40 parts of rosin-modified calcium carbonate powder, and 5-20 parts of water-soluble high molecular polymer; the fiber is degradable plant fiber, and the water-soluble high molecular polymer is polyacrylamide with a molecular weight of 10-25 million.

2. The rosin modified fiber temporary plugging agent according to claim 1, characterized in that: The degradable plant fibers include bamboo, cotton, and wood fibers; the length of the degradable plant fibers is 3-10 mm, and the fiber diameter is 0.1-0.5 mm.

3. The rosin modified fiber temporary plugging agent according to claim 1, characterized in that: The preparation of the rosin modified fiber comprises the following steps: S1. Mixing rosin powder of 100-500 mesh with anhydrous ethanol in a mass ratio of 8-10:2-3 until the rosin powder is completely dissolved to obtain a rosin alcohol solution; soaking the degradable plant fiber in the rosin alcohol solution, and after complete soaking, volatilizing the ethanol at 40-60° C., washing with water to remove residual ethanol, heating to melt the rosin after washing, keeping the temperature for 1-3 minutes, and then cooling to obtain the degradable plant fiber modified by rosin sizing; S2. Evenly mix the rosin powder with the degradable plant fiber modified by rosin sizing obtained in S1, and then pressurize, rub and knead the mixture to obtain the final rosin-modified fiber.

4. The rosin modified fiber temporary plugging agent according to claim 3, characterized in that: The heating temperature is 110-145°C, and the temperature after cooling is 25°C; the rosin powder in S2 is 20-100 mesh, and the volume ratio of the rosin powder to the degradable plant fiber modified by rosin sizing is 0.5:1-1:1; the pressurized friction kneading is specifically as follows: the mixed degradable plant fiber is placed between two hard boards with rough surfaces, and the pressure is applied to 5kg / m 2 -30 kg / m 2 The lower hard plate is fixed and the upper hard plate is rubbed back and forth at a frequency of 30-60 times per minute. The rubbing and kneading time is 10-30 minutes. Every 5-10 minutes, a small amount of plant fiber is taken out and rubbed in the hands. If the fiber feels hard and astringent due to friction, the rubbing and kneading is stopped in advance. The rosin-modified fiber and the rosin powder are separated to obtain the rosin-modified fiber.

5. The rosin modified fiber temporary plugging agent according to claim 1, characterized in that: The preparation of the rosin-modified calcium carbonate powder comprises the following steps: Calcium carbonate powder of 100-500 mesh is spread on a 200-250°C flat plate, and melted rosin is sprayed on the surface of the calcium carbonate powder. The amount of rosin sprayed is 20%-30% of the mass of the calcium carbonate powder. After soaking the calcium carbonate powder, the flat plate is kept vibrating and the calcium carbonate particles are continuously turned to cool down. The temperature is maintained at 80-140°C for 30-90 minutes, and then cooled to room temperature to allow the rosin to crystallize and solidify on the surface of the calcium carbonate. The solidified rosin-modified calcium carbonate powder is crushed and sieved, and 100-500 mesh powder is screened to obtain rosin-modified calcium carbonate powder.

6. The method for preparing the rosin-modified fiber temporary plugging agent according to any one of claims 1 to 5, characterized in that: Before use, mix the rosin modified fiber, rosin modified calcium carbonate powder and water-soluble high molecular polymer evenly.

7. The use of the rosin-modified fiber temporary plugging agent according to any one of claims 1 to 5, characterized in that: The invention includes application in fracturing fluid, wherein the fracturing fluid is suitable for plugging oil reservoirs with a reservoir temperature of 100°C or above. The fracturing fluid also includes a thickener and water, wherein the thickener is a water-soluble high molecular polymer or guar gum.

8. The use of the rosin modified fiber temporary plugging agent according to claim 7, characterized in that: The mass concentration of the rosin modified fiber temporary plugging agent in the fracturing fluid is 0.5-3%.

9. The use of the rosin modified fiber temporary plugging agent according to claim 7, characterized in that: The viscosity of the fracturing fluid is 100-300 mPa·s. The fracturing fluid further comprises a pH regulator, a clay stabilizer, a drainage aid, a bactericide, a foaming agent, a defoaming agent, a cross-linking agent, a gel breaker and a demulsifier.

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