Environmentally adaptive temporary blocking particles for diversion fracturing, and methods of making and using the same

Abstract

The application discloses an environment-adaptable temporary plugging particle for steering fracturing and a preparation method and application thereof, and belongs to the technical field of fracturing temporary plugging in oil and gas fields. The environment-adaptable temporary plugging particle for steering fracturing is a SiO2 inorganic solid particle coated with starch, and the temporary plugging particles are adhered to each other to form a filter cake under formation conditions. The temporary plugging particle can solve the technical problem that the existing particle temporary plugging agent is not dense enough in plugging, has poor plugging effect on small pores between particles, and causes the fracturing fluid to be filtered in target reservoirs such as high-permeability layers and fractures that have been fractured.

Description

Technical Field

[0001] This invention belongs to the field of temporary plugging technology for oil and gas field fracturing, specifically relating to an environmentally adaptable temporary plugging particle for diverting fracturing, its preparation method, and its application. Background Technology

[0002] Particulate temporary plugging agents are currently the most commonly used diversionary plugging agents. They are primarily substances with relatively large particles that can fill formation fractures or pores around the wellhead to form a plugging layer. Although they offer strong plugging strength, good temperature and salt resistance, and excellent economic benefits, the plugging layer may contain gaps, leading to fluid permeation and thus generally lower plugging efficiency. This is because most particulate temporary plugging agents rely on rigid particles to fill fractures for sealing. While they have high compressive strength, the sealing is not dense enough, and their effectiveness in sealing the tiny pores between particles is poor. During fracturing operations, it is necessary to use particles of various sizes in combination to reduce the gaps in the particle plugging layer. However, the presence of tiny pores between rigid particles makes it difficult for temporary plugging particles to achieve the required plugging performance in actual operation.

[0003] Therefore, the existing particulate temporary plugging agents are not dense enough during the temporary plugging fracturing process, and have a poor sealing effect on the tiny pores between particles. This leads to the loss of fracturing fluid in target reservoirs such as high-permeability layers and already opened fractures, which is an urgent technical problem to be solved. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide an environmentally adaptable temporary plugging particle for diverting fracturing, its preparation method and application, in order to solve the technical problem that the existing particle plugging agent is not dense enough during the diverting fracturing operation, and has a poor sealing effect on the small pores between particles, resulting in the loss of fracturing fluid in target reservoirs such as high-permeability layers and fractures that have already been opened.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a method for preparing environmentally adaptable temporary plugging particles for diverting fracturing, comprising the following steps:

[0007] Prepare a mixed suspension of starch and isopropanol, and prepare a mixed solution of tetraethyl orthosilicate and anhydrous ethanol;

[0008] The mixed suspension and mixed solution are stirred and mixed, the pH of the system is adjusted to alkaline using a regulator, and the mixture is stirred and mixed evenly under water bath heating.

[0009] The mixture system obtained by the above steps is filtered, then washed with water, and the pH value is adjusted to neutral to obtain the washed product.

[0010] The water-washed product was frozen with liquid nitrogen and then freeze-dried to obtain powder particles.

[0011] 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.

[0012] In one embodiment, the regulator adjusts the pH of the system to 11-12.

[0013] In one embodiment, the regulator is one or both of NaOH solution and KOH solution.

[0014] In one embodiment, the water bath heating temperature is 40-50°C.

[0015] In one embodiment, the filtration time is 10-15 minutes.

[0016] In one embodiment, the washing process is terminated when the filtered product solidifies.

[0017] In one embodiment, the water washing is performed using an aqueous solution of HAc.

[0018] This invention provides an environmentally adaptable temporary plugging particle for diverting fracturing. The environmentally adaptable temporary plugging particle for diverting fracturing is an inorganic solid particle of SiO2 with starch coated on its surface. Under formation conditions, the environmentally adaptable temporary plugging particle for diverting fracturing adheres to each other to form a filter cake.

[0019] The present invention also provides an application of the above-described environmentally adaptable directional fracturing temporary plugging particles as a temporary plugging agent in the sealing of pores during fracturing directional fracturing.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention provides a method for preparing environmentally adaptable temporary plugging particles for diverting fracturing. A mixed suspension of starch and isopropanol and a mixed solution of tetraethyl orthosilicate and anhydrous ethanol are prepared, and the two mixtures are combined at a specific mass ratio. Tetraethyl orthosilicate is soluble in anhydrous ethanol; therefore, the wettability of anhydrous ethanol on starch can be used to carry the tetraethyl orthosilicate into the starch interior. Adjusting the pH of the system to alkaline using a regulator can prevent premature SiO2 formation. During the washing of the filtered product with an aqueous HAc solution, the tetraethyl orthosilicate inside the starch undergoes hydrolysis, generating inorganic solid particles of SiO2. After freeze-drying, solid SiO2 particles coated with starch are obtained. These inorganic solid SiO2 particles are used to fill fractures and complete the plugging process; their rigidity and hardness give the temporary plugging particles high compressive strength. Because the surface of the temporary plugging agent particles is coated with organic starch, it possesses environmental adaptability and adhesive properties. Therefore, it can match the micropores in formation fractures under formation conditions. Simultaneously, the starch molecules between the particles adhere to form a filter cake, thereby generating high plugging pressure and excellent plugging performance. The aforementioned environmentally adaptable temporary plugging particles for diverting fracturing also have the advantage of low reservoir damage. This invention is biodegradable; after fracturing operations, under the influence of formation temperature and water, it will automatically degrade after a period of stabilization. The degradation products do not harm the formation, reducing the damage of fracturing fluid to the formation. The preparation method is simple and easy to implement, the preparation process is straightforward, the raw materials are readily available and low in cost, and it is convenient for application during construction.

[0022] This invention provides an environmentally adaptable temporary plugging particle for fracturing. The plugging agent particle has environmental adaptability and adhesion under formation conditions. When used in combination, it can match formation fractures. At the same time, the particles adhere to each other to form a filter cake, thereby generating a high plugging pressure.

[0023] In summary, this invention provides an environmentally adaptable temporary plugging particle for diverting fracturing that achieves efficient sealing of micropores between particles. Through its environmental adaptability and adhesiveness, the plugging particle can match formation fractures during diverting fracturing operations. Simultaneously, the particles adhere to form a filter cake, generating high sealing pressure and effectively solving the technical problem of fracturing fluid loss in high-permeability layers and already fractured reservoirs. Furthermore, it is low-cost, biodegradable, and causes minimal reservoir damage, contributing to improved fracturing efficiency and enhancing the economic benefits of oilfield development. Attached Figure Description

[0024] Figure 1 This is a SEM scan of the temporarily blocking particles of the present invention. Detailed Implementation

[0025] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0026] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0027] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0028] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0029] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0030] This invention provides an environmentally adaptable temporary plugging particle for diverting fracturing, its preparation method, and its application. The environmentally adaptable temporary plugging particle for diverting fracturing is an inorganic solid particle of SiO2 with starch coated on its surface. Under formation conditions, the temporary plugging particles adhere to each other to form a filter cake. The environmentally adaptable temporary plugging particle for diverting fracturing is used as a temporary plugging agent to seal micropores during fracturing diversion.

[0031] The environmentally adaptable temporary plugging particles provided by this invention can solve the technical problems of insufficient sealing, poor sealing effect on the micropores between particles, and leakage of fracturing fluid in target reservoirs such as high-permeability layers and already opened fractures during the temporary plugging fracturing diversion operation of existing particle temporary plugging agents.

[0032] The aforementioned temporary plugging agent particles exhibit environmental adaptability and adhesion under formation conditions, enabling them to match formation fractures during fracturing diversion operations. Simultaneously, the particles adhere to each other, forming a filter cake that generates high plugging pressure. Furthermore, these particles are biodegradable, and their degradation products do not harm the formation, reducing the damage caused by fracturing fluid.

[0033] This invention provides an environmentally adaptable temporary plugging particle for fracturing diversion, which is a SiO2 inorganic solid particle with starch coating. The raw materials of the temporary plugging agent include a mixed suspension of starch and isopropanol in a mass ratio of 1.0:(2.0-2.2) and a mixed solution of 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.

[0034] This invention also provides a method for preparing the environmentally adaptable temporary plugging particles for diverting fracturing, comprising the following steps:

[0035] Prepare a mixed suspension of starch and isopropanol, wherein the mass ratio of starch to isopropanol is (1.0-1.5):9; prepare a mixed solution of tetraethyl orthosilicate and anhydrous ethanol, wherein the mass ratio of tetraethyl orthosilicate to anhydrous ethanol is (1.0-2.0):19.

[0036] Mix the starch and isopropanol suspension and the tetraethyl orthosilicate and anhydrous ethanol solution at a mass ratio of 1.0:(2.0-2.2) and stir for 10-15 min.

[0037] Adjust the pH of the system to alkaline 11-12 using a regulator, and continue stirring for 10-15 minutes under water bath heating to ensure thorough mixing. The regulator is NaOH and / or KOH solution, and the water bath heating temperature is 40-50℃.

[0038] The mixture was filtered for 10-15 minutes and washed several times with HAc aqueous solution until the filtered product solidified, in order to adjust the pH to neutral.

[0039] After washing with water to obtain the solidified product, it is quickly frozen with liquid nitrogen and then freeze-dried to obtain powder particles, which are the temporary plugging particles.

[0040] The present invention also provides an environmentally adaptable directional fracturing plugging particle as a plugging agent for sealing micropores in fracturing directional fracturing.

[0041] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0042] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0043] Example 1

[0044] The temporary plugging particles #1 in this embodiment include 2g of starch, 18g of isopropanol, 2g of tetraethyl orthosilicate, and 38g of anhydrous ethanol.

[0045] The preparation process of temporary plugging particles #1 is as follows:

[0046] A sedimentation experiment was conducted on temporary plugging particles #1. The ratio of temporary plugging agent particles to water was 1:5 (mass ratio). Temporary plugging particles #1 were added to the surface of water, and the sedimentation phenomenon was observed. It was found that temporary plugging particles #1 did not settle, indicating that the sealing effect of temporary plugging particles #1 was good, and there was no water penetration that caused the sedimentation phenomenon of temporary plugging particles #1.

[0047] Example 2

[0048] The temporary plugging particles #2 in this embodiment include 2g of starch, 18g of isopropanol, 2.1g of tetraethyl orthosilicate, and 39.9g of anhydrous ethanol.

[0049] The preparation process of temporary plugging particles #2 is as follows:

[0050] A sedimentation test was conducted on temporary plugging particles #2. The ratio of temporary plugging agent particles to water was 1:7 (mass ratio). Temporary plugging particles #2 were added to the surface of water, and the sedimentation phenomenon was observed. It was found that temporary plugging particles #2 did not settle, indicating that the sealing effect of temporary plugging particles #2 was good and there was no water penetration that caused the sedimentation phenomenon of temporary plugging particles #2.

[0051] Example 3

[0052] The temporary plugging particles #3 in this embodiment include 2g of starch, 18g of isopropanol, 2.2g of tetraethyl orthosilicate, and 41.8g of anhydrous ethanol.

[0053] The preparation process of temporary plugging particles #3 is as follows:

[0054] A sedimentation experiment was conducted on temporary plugging particles #3. The ratio of temporary plugging agent particles to polyacrylamide solution was 1:5 (mass ratio). Temporary plugging particles #3 were added to the surface of the polyacrylamide solution, and the sedimentation phenomenon of the temporary plugging agent particles was observed. It was found that temporary plugging particles #3 did not settle, indicating that the sealing effect of temporary plugging particles #3 was good, and there was no polyacrylamide solution penetration that caused the sedimentation phenomenon of temporary plugging particles #3.

[0055] Example 4

[0056] The temporary plugging granules #4 in this embodiment include 2.86g of starch, 17.14g of isopropanol, 2.93g of tetraethyl orthosilicate, and 37.07g of anhydrous ethanol.

[0057] The preparation process of temporary plugging particles #4 is as follows:

[0058] Prepare a mixed suspension of starch and isopropanol and a mixed solution of tetraethyl orthosilicate and anhydrous ethanol, wherein the starch content is 2.86 g, isopropanol 17.14 g, tetraethyl orthosilicate 2.93 g, and anhydrous ethanol 37.07 g; mix 20 g of the starch and isopropanol mixed suspension and 40 g of the tetraethyl orthosilicate and anhydrous ethanol mixed solution and stir for 15 min; adjust the pH of the system to 11 using KOH solution as a regulator, and continue stirring for 12 min under a 43℃ water bath heating condition to ensure thorough mixing; filter the above mixture for 15 min and wash three times with HAc aqueous solution, adjusting the pH to neutral; after washing, allow the product to solidify, then quickly freeze it with liquid nitrogen for freeze drying, temporarily plugging particles #4. A sedimentation test was conducted on temporary plugging particles #4. The ratio of temporary plugging agent particles to polyacrylamide solution was 1:4 (mass ratio). Temporary plugging particles #4 were added to the surface of the polyacrylamide solution, and the sedimentation phenomenon of the temporary plugging agent particles was observed. It was found that temporary plugging particles #4 did not settle, indicating that the sealing effect of temporary plugging particles #4 was good, and there was no polyacrylamide solution penetration that caused the sedimentation phenomenon of temporary plugging particles #4.

[0059] Example 5

[0060] The temporary plugging granules #5 in this embodiment include 2.86g of starch, 17.14g of isopropanol, 3.07g of tetraethyl orthosilicate, and 38.93g of anhydrous ethanol.

[0061] The preparation process of temporary plugging particles #5 is as follows:

[0062] A sedimentation test was conducted on the temporary plugging particles #5. The ratio of temporary plugging agent particles to polyacrylamide solution was 1:7 (mass ratio). The temporary plugging particles #5 were added to the surface of the polyacrylamide solution, and the sedimentation phenomenon of the temporary plugging agent particles was observed. It was found that the temporary plugging particles #5 did not settle, indicating that the temporary plugging particles #5 had a good sealing effect and there was no polyacrylamide solution penetration that caused the temporary plugging particles #5 to settle.

[0063] Example 6

[0064] The temporary plugging particles #6 in this embodiment include 2.86g of starch, 17.14g of isopropanol, 3.22g of tetraethyl orthosilicate, and 40.78g of anhydrous ethanol.

[0065] The preparation process of temporary plugging particles #6 is as follows:

[0066] (1) Prepare a mixed suspension of starch and isopropanol and a mixed solution of tetraethyl orthosilicate and anhydrous ethanol, wherein starch is 2.86 g, isopropanol is 17.14 g, tetraethyl orthosilicate is 3.22 g and anhydrous ethanol is 40.78 g.

[0067] (2) Mix 20g of starch and isopropanol suspension and 44g of tetraethyl orthosilicate and anhydrous ethanol solution and stir for 10min;

[0068] (3) Adjust the pH of the system to 12 using KOH solution as a regulator, and continue stirring for 15 minutes under a 50°C water bath heating condition to ensure thorough mixing;

[0069] (4) The mixture system was filtered for 15 minutes and washed three times with HAc aqueous solution to adjust the pH value to neutral.

[0070] (5) After the product solidifies after washing with water, it is quickly frozen with liquid nitrogen and freeze-dried to temporarily block particle 1#.

[0071] A sedimentation test was conducted on temporary plugging particles #6. The ratio of temporary plugging agent particles to water was 1:5 (mass ratio). Temporary plugging particles #6 were added to the surface of water, and the sedimentation phenomenon was observed. It was found that temporary plugging particles #6 did not settle, indicating that the sealing effect of temporary plugging particles #6 was good and there was no water penetration that caused the sedimentation phenomenon of temporary plugging particles #6.

[0072] Example 7

[0073] The temporary plugging particles #7 in this embodiment include 2.35g of starch, 17.65g of isopropanol, 3.81g of tetraethyl orthosilicate, and 36.19g of anhydrous ethanol.

[0074] The preparation process of temporary plugging particles #7 is as follows:

[0075] A sedimentation test was conducted on the temporary plugging particles #7. The ratio of temporary plugging particles to water was 1:7 (mass ratio). The temporary plugging particles #7 were added to the surface of the water, and the sedimentation phenomenon was observed. It was found that the temporary plugging particles #7 did not settle, indicating that the temporary plugging particles #7 had a good sealing effect and that there was no water penetration that caused the temporary plugging particles #7 to settle.

[0076] Example 8

[0077] The temporary plugging granules #8 in this embodiment include 2.35g of starch, 17.65g of isopropanol, 4g of tetraethyl orthosilicate, and 38g of anhydrous ethanol.

[0078] The preparation process of temporary plugging particles #8 is as follows:

[0079] A sedimentation test was conducted on the temporary plugging particles #8. The ratio of temporary plugging agent particles to polyacrylamide solution was 1:5 (mass ratio). Temporary plugging particles #8 were added to the surface of the polyacrylamide solution, and the sedimentation phenomenon of the temporary plugging agent particles was observed. It was found that temporary plugging particles #8 did not settle, indicating that the temporary plugging particles #8 had a good sealing effect and there was no polyacrylamide solution penetration that caused the temporary plugging particles #8 to settle.

[0080] Example 9

[0081] The temporary plugging particles #9 in this embodiment include 2.35g of starch, 17.65g of isopropanol, 4.19g of tetraethyl orthosilicate, and 39.81g of anhydrous ethanol.

[0082] The preparation process of temporary plugging particles #9 is as follows:

[0083] A sedimentation test was conducted on the temporary plugging particles #9. The ratio of temporary plugging agent particles to polyacrylamide solution was 1:4 (mass ratio). The temporary plugging particles #9 were added to the surface of the polyacrylamide solution, and the sedimentation phenomenon of the temporary plugging agent particles was observed. It was found that the temporary plugging particles #9 did not settle, indicating that the temporary plugging particles #9 had a good sealing effect and there was no polyacrylamide solution penetration that caused the temporary plugging particles #9 to settle.

[0084] like Figure 1 As shown in the electron microscope, the temporary plugging agent particles prepared in the above embodiment have irregular shapes due to the irregular shape of the internal silica. The surface of the temporary plugging agent particles is coated with organic starch. Because the surface of the particles is coated with starch, they have environmental adaptability and adhesion. Therefore, it can be observed that under formation conditions, the starch molecules between the particles adhere to form a filter cake.

[0085] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing environmentally adaptable temporary plugging particles for diverting fracturing, characterized in that, Includes the following steps: Prepare a mixed suspension of starch and isopropanol, and prepare a mixed solution of tetraethyl orthosilicate and anhydrous ethanol; The mixed suspension and mixed solution are stirred and mixed, the pH of the system is adjusted to alkaline using a regulator, and the mixture is stirred and mixed evenly under water bath heating. The mixture system obtained by the above steps is filtered, then washed with water, and the pH value is adjusted to neutral to obtain the washed product. The water-washed product was frozen with liquid nitrogen and then freeze-dried to obtain powder particles; The washing is performed using an aqueous solution of HAc, and the washing is terminated when the filtered product solidifies. The environmentally adaptable diverting fracturing temporary plugging particles are SiO2 inorganic solid particles coated with starch. Under formation conditions, the environmentally adaptable diverting fracturing temporary plugging particles adhere to each other to form a filter cake. The mass ratio of the mixed suspension to the mixed solution is 1.0:(2.0-2.2); 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.

2. The method for preparing environmentally adaptable temporary plugging particles for diverting fracturing according to claim 1, characterized in that, The pH of the system is adjusted to 11-12 by the regulator.

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

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

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

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