Temporary plugging particle for environment-adaptive diversion fracturing as well as preparation method and application of temporary plugging particle

Abstract

The invention discloses an environment-adaptive temporary plugging particle for turning fracturing as well as a preparation method and application thereof, and belongs to the technical field of oil and gas field fracturing temporary plugging. The environment-adaptive temporary plugging particles for turning fracturing are SiO2 inorganic solid particles of which the surfaces are coated with starch, and the temporary plugging particles are adhered to form a filter cake under the formation condition. The temporary plugging agent is used for solving the technical problems that in the temporary plugging fracturing steering construction process of an existing particle temporary plugging agent, plugging is not compact enough, the plugging effect on tiny holes among particles is poor, and consequently fracturing fluid is filtered out in target reservoirs such as a high-permeability layer and fractured cracks, and the technical problem needs to be solved urgently.

Description

Technical Field

[0001] The invention belongs to the technical field of temporary plugging for oil and gas field fracturing, and in particular relates to temporary plugging particles for environmentally adaptable steering fracturing, and a preparation method and application thereof. Background Art

[0002] Granular temporary plugging agent is the most commonly used temporary plugging agent. It is mainly a substance with larger particles, which can form a plugging layer by filling the formation cracks or pores around the wellhead. Although it has strong plugging strength, good temperature and salt resistance, and excellent economic efficiency, the plugging efficiency is average because there may be gaps in the plugging layer, which leads to fluid penetration. This is because most granular temporary plugging agents rely on rigid particles to fill cracks to complete the plugging. They have high compressive strength, but the plugging is not dense enough, and the plugging effect on the tiny pores between the particles is poor. During fracturing construction, it is necessary to use particles of various sizes in combination to reduce the particle plugging gaps, and the existence of tiny pores between rigid particles makes it difficult for temporary plugging particles to meet the plugging performance requirements in actual operation.

[0003] Therefore, the existing particle temporary plugging agents are not dense enough during the temporary plugging fracturing diversion construction process, and the plugging effect on the tiny pores between the particles is poor, resulting in the loss of fracturing fluid in target reservoirs such as high permeability layers and cracks that have been opened, which is a technical problem that needs to be solved urgently. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide an environmentally adaptable temporary plugging particle for diverting fracturing and a preparation method and application thereof, so as to solve the technical problem that the existing temporary plugging particles are not dense enough during the temporary plugging fracturing diverting construction process, and the plugging effect on the tiny pores between the particles is poor, resulting in the loss of fracturing fluid in target reservoirs such as high permeability layers and cracks that have been opened, which is an urgent problem to be solved.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for preparing environmentally adaptable temporary plugging particles for diverting fracturing, comprising the following steps: preparing a mixed suspension of starch and isopropanol, and preparing a mixed solution of ethyl orthosilicate and anhydrous ethanol; The mixed suspension and the mixed solution are stirred and mixed, the pH value of the system is adjusted to alkaline using a regulator, and the stirring and mixing are continued under the condition of heating in a water bath to be uniform; The mixture system obtained by the above steps is filtered, washed with water, and the pH value is adjusted to neutral to obtain a washed product; The washed product is frozen by liquid nitrogen and then freeze-dried to obtain powder particles.

[0006] In one embodiment, the mass ratio of the mixed suspension to the mixed solution is 1.0:(2.0-2.2); wherein the mass ratio of starch to isopropanol is (1.0-1.5):9, and the mass ratio of tetraethyl orthosilicate to anhydrous ethanol is (1.0-2.0):19.

[0007] In one embodiment, the regulator adjusts the pH value of the system to 11-12.

[0008] In one embodiment, the regulator is one or both of a NaOH solution and a KOH solution.

[0009] In one embodiment, the water bath heating temperature is 40-50°C.

[0010] In one embodiment, the filtration time is 10-15 min.

[0011] In one embodiment, the water washing is terminated when the product after suction filtration solidifies.

[0012] In one embodiment, the water washing is performed using a HAc aqueous solution.

[0013] The present invention provides an environmentally adaptable temporary plugging particle for steering fracturing. The environmentally adaptable temporary plugging particle for steering fracturing is SiO2 inorganic solid particle with starch coated on the surface. Under formation conditions, the environmentally adaptable temporary plugging particle for steering fracturing adheres to form a filter cake.

[0014] The present invention also provides a temporary plugging particle for environmentally adaptable diversion fracturing as described above, which is used as a temporary plugging agent in plugging pores in diversion fracturing.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing environmentally adaptive temporary plugging particles for steering fracturing, comprising preparing a mixed suspension of starch and isopropanol and a mixed solution of tetraethyl orthosilicate and anhydrous ethanol, and mixing the two mixtures in a certain mass ratio. Tetraethyl orthosilicate is soluble in anhydrous ethanol, so the wettability of anhydrous ethanol on starch can be used to carry tetraethyl orthosilicate into the starch, and then the pH of the system is adjusted to alkaline with a regulator to avoid the premature generation of SiO2. In the process of washing the product after suction filtration with an aqueous HAc solution, the tetraethyl orthosilicate located inside the starch is hydrolyzed to generate inorganic solid particles SiO2. After freeze-drying, SiO2 solid particles with starch coated on the surface can be obtained. The inorganic solid particles SiO2 are used to fill cracks to complete the plugging, and the temporary plugging particles have a higher compressive strength due to their rigidity and hardness. Because the temporary plugging agent particles are coated with organic starch on the surface, they have environmental adaptability and adhesion, so they can match the tiny pores in the formation cracks under formation conditions. At the same time, the starch molecules between the particles adhere to form a filter cake, thereby forming a higher plugging pressure and good plugging performance. The above-mentioned environmentally adaptable temporary plugging particles for steering fracturing also have the advantage of low reservoir damage. The present invention is biodegradable. After the fracturing construction is completed, it will automatically degrade after being stable for a period of time under the action of formation temperature and water. The degradation products do not harm the formation, and can reduce the damage of the fracturing fluid to the formation. The preparation method is simple and easy, the preparation process is simple, the raw materials are easy to obtain and the cost is low, which is convenient for construction and injection.

[0016] The present invention provides temporary plugging particles for environmentally adaptable steering fracturing. The temporary plugging agent particles have environmental adaptability and adhesion under formation conditions, and can match formation fractures when used in combination. At the same time, the particles adhere to form filter cakes, thereby forming a higher plugging pressure.

[0017] In summary, the present invention provides a temporary plugging particle with environmental adaptability for diverting fracturing, which can achieve efficient plugging effect on the tiny pores between particles. Through its environmental adaptability and adhesion, the temporary plugging particles can match the formation cracks during fracturing diversion construction, and at the same time, the particles adhere to form a filter cake, thereby forming a higher plugging pressure, effectively solving the technical problem of fracturing fluid loss in target reservoirs such as high permeability layers and cracks that have been opened. At the same time, it has low cost, biodegradability, and low damage to the reservoir, which helps to improve the fracturing effect and promote the efficiency and economic benefits of oil field exploitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a SEM scan of the temporary plugging particles of the present invention. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0021] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0022] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0023] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0024] The present invention provides an environmentally-adaptive temporary plugging particle for steering fracturing, and a preparation method and application thereof. The environmentally-adaptive temporary plugging particle for steering fracturing is an SiO2 inorganic solid particle with starch coated on the surface. Under formation conditions, the temporary plugging particles adhere to form a filter cake. The environmentally-adaptive temporary plugging particle for steering fracturing is used as a temporary plugging agent in the plugging of tiny pores in fracturing steering.

[0025] The environmentally adaptable temporary plugging particles provided by the present invention can solve the technical problems that the existing temporary plugging particles have insufficient plugging density during the temporary plugging fracturing diversion construction process, have poor plugging effect on the tiny pores between particles, and have fracturing fluid filtration loss in target reservoirs such as high permeability layers and cracks that have been opened.

[0026] The temporary plugging agent particles have environmental adaptability and cohesiveness under formation conditions, and can match the formation cracks during fracturing diversion construction. At the same time, the particles adhere to form a filter cake, thereby forming a higher plugging pressure. In addition, the particles are biodegradable, and the degradation products do not harm the formation, reducing the damage of the fracturing fluid to the formation.

[0027] The invention provides an environmentally adaptable temporary plugging particle for fracturing diversion, which is a SiO2 inorganic solid particle with starch coated on the surface. The raw materials of the temporary plugging agent include a mixed suspension prepared by starch and isopropanol in a mass ratio of 1.0:(2.0-2.2) and a mixed solution prepared by tetraethyl orthosilicate and anhydrous ethanol, wherein the mass ratio of starch to isopropanol is (1.0-1.5):9, and the mass ratio of tetraethyl orthosilicate to anhydrous ethanol is (1.0-2.0):19.

[0028] The present invention also provides a method for preparing the environmentally adaptable temporary plugging particles for diverting fracturing, comprising the steps of: A mixed suspension of starch and isopropanol is prepared, wherein the mass ratio of starch to isopropanol is (1.0-1.5):9; a mixed solution of ethyl orthosilicate and anhydrous ethanol is prepared, wherein the mass ratio of ethyl orthosilicate to anhydrous ethanol is (1.0-2.0):19; The mixed suspension of starch and isopropanol and the mixed solution of ethyl orthosilicate and anhydrous ethanol were mixed in a mass ratio of 1.0:(2.0-2.2) and stirred for 10-15 minutes; Use a regulator to adjust the pH value of the system to alkaline 11-12, and continue stirring for 10-15 minutes under the condition of water bath heating to fully mix, wherein the regulator is NaOH and / or KOH solution, and the water bath heating temperature is 40-50°C; The mixture system is filtered for 10-15 minutes, and washed with HAc aqueous solution several times until the filtered product solidifies, so as to adjust the pH value to neutral; After washing with water to obtain a solidified product, it is quickly frozen with liquid nitrogen and freeze-dried to obtain powder particles, which are temporary plugging particles.

[0029] The present invention also provides a temporary plugging particle for diverting fracturing with environmental adaptability, which is used as a temporary plugging agent for plugging tiny pores in diverting fracturing.

[0030] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0031] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0032] Example 1 The temporary plugging particles 1# of this embodiment include 2g of starch, 18g of isopropyl alcohol, 2g of tetraethyl orthosilicate, and 38g of anhydrous ethanol.

[0033] The preparation process of temporary plugging particles 1# is as follows: A sedimentation experiment was conducted on temporary plugging particles 1#. The temporary plugging agent particles and clean water were weighed at a ratio of 1:5 (mass ratio). Temporary plugging agent particles 1# were added to the surface of clean water to observe whether the temporary plugging agent particles settled. After observation, it was found that temporary plugging agent particles 1# did not settle, indicating that temporary plugging particles 1# had a good plugging effect and there was no clean water infiltration to cause sedimentation of temporary plugging particles 1#.

[0034] Example 2 The temporary plugging particles 2# of this embodiment include 2 g of starch, 18 g of isopropyl alcohol, 2.1 g of tetraethyl orthosilicate, and 39.9 g of anhydrous ethanol.

[0035] The preparation process of temporary plugging particles 2# is as follows: A sedimentation experiment was conducted on temporary plugging particles 2#. The temporary plugging agent particles and clean water were weighed at a ratio of 1:7 (mass ratio). Temporary plugging agent particles 2# were added to the surface of clean water to observe whether the temporary plugging agent particles settled. After observation, it was found that temporary plugging particles 2# did not settle, indicating that temporary plugging particles 2# had a good plugging effect and there was no clean water infiltration to cause sedimentation of temporary plugging particles 2#.

[0036] Example 3 The temporary plugging particles 3# of this embodiment include 2 g of starch, 18 g of isopropyl alcohol, 2.2 g of tetraethyl orthosilicate, and 41.8 g of anhydrous ethanol.

[0037] The preparation process of temporary plugging particles 3# is as follows: A sedimentation experiment was conducted on the temporary plugging particles 3#. The temporary plugging agent particles: polyacrylamide solution = 1:5 (mass ratio) were weighed, and the temporary plugging agent particles 3# were added to the surface of the polyacrylamide solution to observe whether the temporary plugging agent particles settled. After observation, it was found that the temporary plugging agent particles 3# did not settle, indicating that the temporary plugging particles 3# had a good plugging effect and there was no sedimentation of the temporary plugging particles 3# caused by the penetration of the polyacrylamide solution.

[0038] Example 4 The temporary plugging particles 4# of this embodiment include 2.86 g of starch, 17.14 g of isopropyl alcohol, 2.93 g of tetraethyl orthosilicate, and 37.07 g of anhydrous ethanol.

[0039] The preparation process of temporary plugging particles 4# is as follows: Prepare a mixed suspension of starch and isopropanol and a mixed solution of tetraethyl orthosilicate and anhydrous ethanol, wherein there are 2.86g of starch, 17.14g of isopropanol, 2.93g of tetraethyl orthosilicate and 37.07g of anhydrous ethanol; mix 20g of the mixed suspension of starch and isopropanol and 40g of the mixed solution of tetraethyl orthosilicate and anhydrous ethanol, and stir for 15 minutes; adjust the pH value of the system to 11 with a regulating agent KOH solution, and continue stirring for 12 minutes under the condition of heating in a 43°C water bath to fully mix; filter the above mixture system for 15 minutes, and wash it with HAc aqueous solution for 3 times to adjust the pH value to neutral; after the product solidifies after washing, quickly freeze it with liquid nitrogen, and freeze-dry it to temporarily block particle 4#. A sedimentation experiment was conducted on temporary plugging particles 4#. The temporary plugging agent particles and polyacrylamide solution were weighed at a ratio of 1:4 (mass ratio). Temporary plugging particles 4# were added to the surface of the polyacrylamide solution to observe whether the temporary plugging agent particles settled. It was found that temporary plugging particles 4# did not settle, indicating that temporary plugging particles 4# had a good plugging effect and there was no sedimentation of temporary plugging particles 4# caused by the penetration of polyacrylamide solution.

[0040] Example 5 The temporary plugging particles 5# of this embodiment include 2.86 g of starch, 17.14 g of isopropyl alcohol, 3.07 g of tetraethyl orthosilicate, and 38.93 g of anhydrous ethanol.

[0041] The preparation process of temporary plugging particles 5# is as follows: A sedimentation experiment was conducted on the temporary plugging particles 5#. The temporary plugging agent particles: polyacrylamide solution = 1:7 (mass ratio) were weighed, and the temporary plugging agent particles 5# were added to the surface of the polyacrylamide solution to observe whether the temporary plugging agent particles settled. After observation, it was found that the temporary plugging agent particles 5# did not settle, indicating that the temporary plugging particles 5# had a good plugging effect and there was no sedimentation of the temporary plugging particles 5# caused by the penetration of the polyacrylamide solution.

[0042] Example 6 The temporary plugging particles 6# of this embodiment include 2.86 g of starch, 17.14 g of isopropyl alcohol, 3.22 g of tetraethyl orthosilicate, and 40.78 g of anhydrous ethanol.

[0043] The preparation process of temporary plugging particles 6# is as follows: (1) Prepare a mixed suspension of starch and isopropanol and a mixed solution of tetraethyl orthosilicate and anhydrous ethanol, wherein the mixture contains 2.86 g of starch, 17.14 g of isopropanol, 3.22 g of tetraethyl orthosilicate and 40.78 g of anhydrous ethanol; (2) Mix 20 g of a mixed suspension of starch and isopropanol and 44 g of a mixed solution of ethyl orthosilicate and anhydrous ethanol, and stir for 10 min; (3) Use KOH solution as a regulator to adjust the pH value of the system to 12, and continue stirring for 15 minutes under the condition of heating in a 50°C water bath to fully mix; (4) Filter the mixture for 15 min, wash it with HAc aqueous solution three times, and adjust the pH value to neutral; (5) After the product solidifies after washing with water, it is quickly frozen with liquid nitrogen and freeze-dried to temporarily block particle 1#.

[0044] A sedimentation experiment was conducted on temporary plugging particles 6#. The temporary plugging agent particles and clean water were weighed at a ratio of 1:5 (mass ratio). Temporary plugging agent particles 6# were added to the surface of clean water to observe whether the temporary plugging agent particles settled. It was found that temporary plugging particles 6# did not settle, indicating that temporary plugging particles 6# had a good plugging effect and there was no clean water infiltration to cause sedimentation of temporary plugging particles 6#.

[0045] Example 7 The temporary plugging particles 7# of this embodiment include 2.35 g of starch, 17.65 g of isopropyl alcohol, 3.81 g of tetraethyl orthosilicate, and 36.19 g of anhydrous ethanol.

[0046] The preparation process of temporary plugging particles 7# is as follows: A sedimentation experiment was conducted on temporary plugging particles 7#. The temporary plugging agent particles and clean water were weighed at a ratio of 1:7 (mass ratio). Temporary plugging agent particles 7# were added to the surface of clean water to observe whether the temporary plugging agent particles settled. It was found that temporary plugging particles 7# did not settle, indicating that temporary plugging particles 7# had a good plugging effect and there was no clean water infiltration to cause sedimentation of temporary plugging particles 7#.

[0047] Example 8 The temporary plugging particles 8# of this embodiment include 2.35 g of starch, 17.65 g of isopropyl alcohol, 4 g of tetraethyl orthosilicate, and 38 g of anhydrous ethanol.

[0048] The preparation process of temporary plugging particles 8# is as follows: A sedimentation experiment was conducted on the temporary plugging particles 8#. The temporary plugging agent particles and polyacrylamide solution were weighed at a ratio of 1:5 (mass ratio). The temporary plugging agent particles 8# were added to the surface of the polyacrylamide solution to observe whether the temporary plugging agent particles settled. It was found that the temporary plugging agent particles 8# did not settle, indicating that the temporary plugging particles 8# had a good plugging effect and there was no sedimentation of the temporary plugging particles 8# caused by the penetration of the polyacrylamide solution.

[0049] Example 9 The temporary plugging particles 9# of this embodiment include 2.35 g of starch, 17.65 g of isopropyl alcohol, 4.19 g of tetraethyl orthosilicate, and 39.81 g of anhydrous ethanol.

[0050] The preparation process of temporary plugging particles 9# is as follows: A sedimentation experiment was conducted on temporary plugging particles 9#. The temporary plugging agent particles and polyacrylamide solution were weighed at a ratio of 1:4 (mass ratio). Temporary plugging particles 9# were added to the surface of the polyacrylamide solution to observe whether the temporary plugging agent particles settled. It was found that temporary plugging particles 9# did not settle, indicating that temporary plugging particles 9# had a good plugging effect and there was no sedimentation of temporary plugging particles 9# caused by the penetration of polyacrylamide solution.

[0051] like Figure 1 As shown, under electron microscope scanning, the temporary plugging agent particles prepared in the above embodiment have irregular shapes due to the irregular shapes of the internal silica, and the surface of the temporary plugging agent particles is coated with organic starch. Because the surface of the particles is coated with starch, there is environmental adaptability and adhesion. Therefore, it can be observed that the starch molecules between the particles adhere to form a filter cake under the formation conditions.

[0052] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing environmentally adaptable temporary plugging particles for diverting fracturing, characterized in that: The following steps are involved: preparing a mixed suspension of starch and isopropanol, and preparing a mixed solution of ethyl orthosilicate and anhydrous ethanol; The mixed suspension and the mixed solution are stirred and mixed, the pH value of the system is adjusted to alkaline using a regulator, and the stirring and mixing are continued under the condition of heating in a water bath to be uniform; The mixture system obtained by the above steps is filtered, washed with water, and the pH value is adjusted to neutral to obtain a washed product; The washed product is frozen by liquid nitrogen and then freeze-dried to obtain powder particles.

2. The method for preparing the environmentally-adaptable temporary plugging particles for diverting fracturing according to claim 1, characterized in that: The mass ratio of the mixed suspension to the mixed solution is 1.0:(2.0-2.2).

3. The method for preparing the environmentally-adaptable temporary plugging particles for diverting fracturing according to claim 1, characterized in that: The mass ratio of the starch to isopropanol is (1.0-1.5):9, and the mass ratio of the tetraethyl orthosilicate to anhydrous ethanol is (1.0-2.0):

19.

4. The method for preparing the environmentally-adaptable temporary plugging particles for diverting fracturing according to claim 1, characterized in that: The regulator adjusts the pH value of the system to 11-12.

5. The method for preparing the environmentally-adaptable temporary plugging particles for diverting fracturing according to claim 1, characterized in that: The regulator is one or both of a NaOH solution and a KOH solution.

6. The method for preparing the environmentally adaptable temporary plugging particles for diverting fracturing according to claim 1, characterized in that: The water bath heating temperature is 40-50°C.

7. The method for preparing the environmentally-adaptable temporary plugging particles for diverting fracturing according to claim 1, characterized in that: The filtration time is 10-15 min.

8. The method for preparing the environmentally-adaptable temporary plugging particles for diverting fracturing according to claim 1, characterized in that: The water washing is performed using a HAc aqueous solution, and the water washing is terminated when the product after suction filtration solidifies.

9. An environmentally-adaptive temporary plugging particle for diverting fracturing prepared by the method for preparing environmentally-adaptive temporary plugging particle for diverting fracturing according to any one of claims 1 to 8, characterized in that: The environmentally-adaptable temporary plugging particles for diverting fracturing are SiO2 inorganic solid particles with starch coated on the surface. Under formation conditions, the environmentally-adaptable temporary plugging particles for diverting fracturing adhere to each other to form a filter cake.

10. Use of the environmentally adaptable temporary plugging particles for diverting fracturing as claimed in claim 9 as a temporary plugging agent in plugging pores in diverting fracturing.

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