An acid resistant smart dissolving material for acidizing fracturing downhole fracturing tools

Abstract

In order to solve the problem that the dissolving speed of the existing soluble downhole fracturing tool in acid liquid is too fast and cannot meet the pressure bearing requirement of fracturing, the application discloses an acid-resistant intelligent dissolving material for an acidizing and fracturing downhole fracturing tool, which comprises a soluble magnesium-based or aluminum-based alloy matrix, an acid-resistant coating wrapped on the surface of the soluble alloy matrix and an intelligent dissolving control prepared from a thermal-induced shape memory material and uniformly distributed in the acid-resistant coating. The downhole fracturing tool prepared from the acid-resistant intelligent dissolving material can not only ensure that the fracturing tool does not dissolve during acidizing and ensure the pressure bearing capacity during fracturing, but also can make the intelligent dissolving control reach the deformation trigger temperature through the cumulative heat release of acid-rock reaction, cause the deformation recovery and form a channel in the acid-resistant coating for the acid liquid to enter, so as to realize the rapid dissolving of the fracturing tool after acidizing and fracturing, thereby making the soluble downhole fracturing tool have the acid resistance and solubility at the same time, effectively improving the oil and gas resource exploitation efficiency and reducing the oil and gas resource exploitation cost.

Description

Technical Field

[0001] This invention patent belongs to the field of oil extraction, specifically, it relates to an acid-resistant smart dissolving material for downhole fracturing tools used in acid fracturing wells. Background Technology

[0002] Carbonate oil and gas reservoirs occupy an extremely important position in global oil and gas resources. my country's carbonate oil and gas reservoirs are characterized by deep burial, low permeability, and heterogeneity, making development challenging. Acid fracturing is a key technology for connecting reservoirs and ensuring the safe and efficient exploitation of carbonate oil and gas reservoirs.

[0003] Acid fracturing refers to the injection of acid into the formation under pressures higher than the formation fracturing pressure, creating fractures within the formation. The acid then dissolves the fracture walls unevenly, forming highly conductive fractures. Downhole fracturing tools, such as soluble balls, soluble ball seats, soluble screens, and soluble packers, are crucial for ensuring successful fracturing by sealing the casing and meeting the pressure requirements. Existing downhole fracturing tools are mainly made of soluble magnesium-based alloys or soluble aluminum-based alloys, meeting the pressure requirements under hydraulic fracturing conditions and the need for rapid dissolution after fracturing, and are widely used in hydraulic fracturing. Acid fracturing typically employs a mixture of 5%-20% hydrochloric acid, thickener, crosslinking agent, retarder, conditioner, and breaker to improve the conductivity of carbonate reservoirs. Existing magnesium-based or aluminum-based soluble downhole fracturing tools can meet the requirements under hydraulic fracturing conditions; however, these tools dissolve at rates as high as 5763 mg / (cm³) in acid. 2 Above h), it will dissolve rapidly in acid and cannot meet the sealing and pressure-bearing requirements under acid fracturing conditions.

[0004] To address the challenge of existing downhole fracturing tool materials not simultaneously possessing both acid resistance and solubility, this invention coats the surface of commonly used magnesium-based or aluminum-based alloy materials in existing downhole fracturing tools with an acid-resistant coating, forming an acid-resistant composite material that ensures the magnesium-based or aluminum-based alloy matrix does not dissolve during acid fracturing. Within the acid-resistant coating, numerous intelligent dissolution controls made of thermotropic shape memory materials are designed. During acid fracturing, the reaction between the acid and the rock releases a large amount of heat. This heat accumulates, causing the intelligent dissolution controls embedded in the acid-resistant coating to reach their recovery temperature and undergo recovery deformation, returning to their initial shape. By designing a reasonable initial shape and shape embedded in the acid-resistant coating for the intelligent dissolution controls, as well as the relative relationship between the size of the intelligent dissolution controls and the coating thickness, the acid-resistant coating on the surface of the intelligent dissolution controls can be broken during the process of returning to their initial shape. This allows acid or formation water to come into contact with the soluble magnesium-based or aluminum-based alloy matrix through the cracks in the acid-resistant coating, causing the magnesium-based or aluminum-based alloy matrix to dissolve rapidly. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an acid-resistant intelligent dissolving material for preparing downhole fracturing tools for acid fracturing. Downhole fracturing tools prepared with this material not only ensure that they do not dissolve during acid fracturing, guaranteeing their pressure-bearing and temporary plugging function, but also achieve rapid dissolution after acid fracturing. This not only avoids the drilling and grinding problems associated with conventional acid fracturing downhole tools (steel fracturing tools), such as long drilling and grinding cycles, high drilling and grinding costs, and numerous drilling and grinding accidents, but also effectively solves the problem of excessively rapid dissolution of existing soluble fracturing tools (soluble magnesium alloy and soluble aluminum alloy fracturing tools) in acid. This can effectively improve the efficiency of acid fracturing operations, increase oil and gas resource extraction efficiency, and reduce oil and gas resource extraction costs. It can be widely used in downhole fracturing tools such as soluble balls, soluble ball seats, soluble screens, and soluble packers.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an acid-resistant intelligent dissolving material for downhole fracturing tools used in acid fracturing, the intelligent dissolving material comprising a soluble magnesium-based alloy or aluminum-based alloy matrix, an acid-resistant coating covering the surface of the magnesium-based alloy or aluminum-based alloy, and intelligent dissolving controls uniformly distributed in the acid-resistant coating.

[0007] Furthermore, the compressive strength of the soluble magnesium-based alloy or aluminum-based alloy matrix must meet the pressure requirements during acid fracturing, typically requiring a pressure-bearing capacity greater than 70 MPa.

[0008] Furthermore, the thickness of the acid-resistant coating can be adjusted according to the total amount and flow rate of the acid during acid fracturing and the acidizing time determined by the acidizing process, but the total thickness of the acid-resistant coating shall not exceed 1.5 mm. It can be prepared using materials such as epoxy resin, polyurethane, and fluorocarbon resin, and the yield strength under pressure shall not exceed 130 MPa.

[0009] Furthermore, the intelligent dissolving control can be made of thermotropic shape memory materials such as polyimide resin, graphene or carbon fiber reinforced polyimide resin, and iron-based shape memory alloy. The hardness of the intelligent dissolving control needs to be higher than that of the acid-resistant coating. Its initial shape is a small arc plate with a bending angle of 75° to 95°. It is pressed into a flat plate at a thermotropic deformation temperature of 200° to 300° and fixed at room temperature.

[0010] Furthermore, when the intelligent dissolving control is prepared using graphene or carbon fiber reinforced polyimide resin, the mass fraction of graphene or carbon fiber in the intelligent dissolving control is 0.2%-1.2%.

[0011] Furthermore, the thickness of the intelligent dissolving control is no more than 0.2 mm, and its length and width are 0.5 mm to 1.50 mm.

[0012] Furthermore, the weight percentage of the intelligent dissolution control in the acid-resistant coating is 3%-8%. The weight percentage of the intelligent dissolution control in the acid-resistant coating can be adjusted within the range of 3%-8% based on the total amount of acid, the flow rate, the acidification time, and the coating thickness during acid fracturing.

[0013] Furthermore, the recovery stress of the intelligent dissolving control should typically be higher than 130 MPa, so that when the intelligent dissolving control recovers its initial shape under the cumulative effect of the heat released by the reaction between acid and rock, it can break through the barrier of the acid-resistant coating and destroy the acid-resistant coating, forming a channel for acid or formation water to enter the interior of the acid-resistant intelligent dissolving material, thereby rapidly dissolving the internal magnesium-based alloy or aluminum-based alloy matrix.

[0014] The beneficial effects of this invention are:

[0015] To address the problem that existing soluble downhole fracturing tools dissolve too quickly in acid, failing to meet the pressure requirements under acid fracturing conditions, this invention creatively coats an acid-resistant coating onto the surface of a soluble alloy substrate. This improves the corrosion resistance of the soluble material in high-temperature acidic environments, ensuring the downhole fracturing tool does not dissolve during acid fracturing and guaranteeing the pressure requirements. Simultaneously, a smart dissolution control device made of thermotropic shape memory material is uniformly embedded within the acid-resistant coating. After acid fracturing, the recovery force of the smart dissolution control device damages the surface acid-resistant coating, exposing the soluble alloy substrate to the high-temperature acidic environment and enabling rapid dissolution of the fracturing tool. This allows the downhole fracturing tool to simultaneously possess acid resistance and solubility, avoiding the excessively rapid dissolution of existing soluble downhole fracturing tools in acid and the drilling difficulties associated with existing steel fracturing tools, such as long drilling cycles, high drilling costs, and numerous drilling accidents after acid fracturing. This effectively improves oil and gas resource extraction efficiency and reduces oil and gas resource extraction costs. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0017] Figure 2 This is an example of the deformation process of the thermo-induced shape memory material described in this invention.

[0018] Figure 3 This is a schematic diagram showing the distribution of the intelligent dissolving control of the present invention in the acid-resistant coating.

[0019] Figure 4 This is a schematic diagram of the intelligent dissolving control of the present invention restoring its shape and destroying the acid-resistant coating. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings, so that the objectives, technical solutions, and advantages of the present invention will be clearer. It should be understood that the examples described herein are only for better illustration and explanation of the present invention and are not intended to limit the present invention.

[0021] like Figure 1 and Figure 3 As shown, an acid-resistant smart dissolution material for downhole fracturing tools in acid fracturing wells includes a soluble aluminum-based alloy substrate 1, a smart dissolution control 2, and an acid-resistant coating 3, wherein the smart dissolution control 2 is uniformly distributed within the acid-resistant coating 3. Figure 4 As shown, the intelligent dissolution control 2 will return to its initial shape and damage the acid-resistant coating 3, producing cracks 4, after reaching the thermal recovery trigger temperature.

[0022] An acid-resistant smart dissolution material for downhole fracturing tools in acid fracturing wells, comprising a soluble aluminum-based alloy matrix and a smart dissolution control system using 0.6% (mass fraction) carbon fiber reinforced polyimide resin. The deformation process of the carbon fiber reinforced polyimide resin is as follows: Figure 2 As shown. The intelligent dissolving control is initially shaped like an arc plate bent at 85°. Under external force at 200°C, the intelligent dissolving control is pressed into a flat plate shape and fixed at room temperature.

[0023] A 0.3mm thick epoxy resin acid-resistant coating is sprayed onto a soluble aluminum alloy substrate. Then, a flat, 0.15mm thick intelligent dissolving control unit (1.0mm in length and width) is uniformly sprayed onto the acid-resistant coating, followed by another 0.3mm thick epoxy resin acid-resistant coating. The total weight of the intelligent dissolving control unit is 5% of the total weight of the acid-resistant coating.

[0024] like Figure 3 and Figure 4As shown, in the initial stage of acid fracturing, the epoxy resin acid-resistant coating on the surface of the smart dissolution material protects the soluble aluminum-based alloy from corrosion, thus ensuring the pressure-bearing and temporary plugging effect during acid fracturing. During acid fracturing, the acid added during acidification reacts with the rock. The acid-rock reaction is an exothermic process, and the heat released during the reaction accumulates continuously in the confined space around the fracturing tool, causing the temperature of the fracturing tool to rise. When the temperature of the acid-resistant coating on the surface of the fracturing tool rises to the trigger temperature of the thermally induced recovery of the carbon fiber reinforced polyimide resin, the smart dissolution control made of carbon fiber reinforced polyimide will be triggered to undergo deformation recovery. Its shape will gradually return from a flat plate to an initial arc plate shape with a bending angle of 85°. Since the recovery stress of carbon fiber reinforced polyimide resin is higher than the compressive strength of epoxy resin acid-resistant coating, the intelligent dissolving control made of carbon fiber reinforced polyimide resin will break through the barrier of epoxy resin acid-resistant coating and destroy the epoxy resin acid-resistant coating, creating multiple channels for acid to enter the interior of the acid-resistant intelligent dissolving material. After the acid enters the interior of the acid-resistant intelligent dissolving material through the channels formed by the destruction of the acid-resistant coating by the intelligent dissolving control, it comes into direct contact with the soluble aluminum-based alloy. The soluble aluminum-based alloy dissolves rapidly in a high-temperature acidic environment.

[0025] The above are embodiments of the present invention. Those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above. Any obvious improvements, substitutions or modifications made by those skilled in the art based on the present invention are within the protection scope of the present invention.

Claims

1. An acid-resistant smart dissolving material for downhole fracturing tools used in acid fracturing wells, characterized in that... The acid-resistant smart dissolving material uses a soluble magnesium-based alloy or aluminum-based alloy as the matrix (1), and covers the surface of the soluble magnesium-based alloy or aluminum-based alloy matrix (1) with an acid-resistant coating (3). The acid-resistant coating (3) contains a certain number of uniformly distributed smart dissolving controls (2) made of shape memory material. The compressive strength of the soluble magnesium-based alloy or aluminum-based alloy matrix is ​​greater than 70 MPa; The thickness of the acid-resistant coating (3) is not greater than 1.5 mm, and the yield strength under pressure is not greater than 130 MPa; The intelligent dissolving control (2) has a thickness of no more than 0.2 mm and a length and width of 0.5 mm to 1.50 mm. The shape memory material used to prepare the intelligent dissolving control (2) is polyimide resin, polyimide resin reinforced with graphene or carbon fiber at a mass fraction of 0.2%-1.2%, or iron-based shape memory alloy. The initial shape of the intelligent dissolving control (2) is a small arc plate with a bending angle of 75°~95°. It is pressed into a flat plate in a high temperature environment of 200°-300° and fixed in an acid-resistant coating at room temperature. The recovery stress of the intelligent dissolving control (2) should be higher than 130MPa so that when the intelligent dissolving control recovers its initial shape under the cumulative effect of the heat released by the reaction of acid and rock, it can break through the barrier of the acid-resistant coating and destroy the acid-resistant coating, forming a channel for acid or formation water to enter the interior of the acid-resistant intelligent dissolving material, thereby rapidly dissolving the internal magnesium-based alloy or aluminum-based alloy matrix.

2. The acid-resistant smart dissolving material for downhole fracturing tools in acid fracturing wells according to claim 1, characterized in that, The acid-resistant coating (3) is an epoxy resin coating, a polyurethane coating, or a fluorocarbon resin coating.

3. The acid-resistant smart dissolving material for downhole fracturing tools in acid fracturing wells according to claim 1, characterized in that, The intelligent dissolving control (2) accounts for 3%-8% of the weight of the acid-resistant coating (3).

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