Pre-water-control composite plugging agent for old well refracturing and preparation method of pre-water-control composite plugging agent

Abstract

The invention relates to a pre-water-control composite plugging agent for old well refracturing and a preparation method thereof, and belongs to the field of reservoir transformation. The composite plugging agent is prepared from the following raw materials: water-borne epoxy resin emulsion, a curing agent, cement, a dispersing agent, nylon fibers and magnesium oxide, wherein the mass ratio of the water-borne epoxy resin emulsion to the curing agent to the cement to the dispersing agent to the nylon fibers to the magnesium oxide is (10 to 15) to (10 to 13) to (18 to 25) to (0.4 to 0.6) to (0.2 to 0.6) to (0.04 to 0.08). Epoxy resin EP-20 is used as a raw material to synthesize a water-borne epoxy resin emulsion, then the water-borne epoxy resin emulsion, the curing agent, the cement, the dispersing agent, the nylon fiber and the magnesium oxide are scientifically matched, the front water control composite blocking agent is obtained, the viscosity of the blocking agent during injection is reduced, and the injection construction efficiency is improved; and the curing time of the plugging agent is greatly shortened by adding magnesium oxide.

Description

Technical Field

[0001] The invention belongs to the field of reservoir transformation, and particularly relates to a pre-placed water-controlling composite plugging agent for repeated fracturing of old wells and a preparation method thereof. Background Art

[0002] The Ordos Basin is a typical "three-low oil reservoir" that needs to be developed through water injection to achieve the goal of improving the ultimate recovery rate. With the extension of development time, affected by the heterogeneity of the reservoir and the adaptability of the well network, the main oil fields such as Ansai, Jing'an, and Jiyuan have entered the medium-to-high water content development stage as a whole. The current comprehensive water content is 62.9%. According to the production status of the Triassic directional wells of Chang 3 and below, there are 15,800 oil wells with a water content greater than 40%, accounting for 54.1%. Since the main technology of repeated fracturing of medium-to-high water-content wells has not yet been formed, it is difficult to achieve efficient potential after these wells have low production and low efficiency, resulting in the space for well selection of oil well measures becoming smaller year by year. The lost reserves are basically high-quality reserves. How to activate this part of the reserves has great potential and significance. At this stage, water control is mainly achieved through temporary plugging fracturing. During the fracturing process, temporary plugging agents are pumped into the fractures to inhibit excessive extension of the fracture length and reduce the risk of water content increase after the measures, but the effects of the measures vary greatly.

[0003] Water control and repeated fracturing are urgent needs for efficient development of oil reservoirs. Innovative water control and fracturing technology ideas for pre-plugging of medium and high water-content wells are proposed to effectively plug the water-seeping channels of oil wells and force the repeated fracturing cracks to turn. Among them, water-seeping channel identification is the premise, low-cost and efficient plugging materials are the basis, and pre-plugging + fracturing joint process is the key. Pre-plugging materials that meet the technical needs of repeated fracturing of medium and high water-content wells have not yet been finalized, and it is urgent to improve the comprehensive performance of the materials so that they have the characteristics of "two highs and three lows" (high compressive strength, high bonding strength, low cost, low viscosity injection, and low shrinkage). Summary of the invention

[0004] In view of the above problems, the present invention proposes a pre-water control composite plugging agent for repeated fracturing of old wells and a preparation method thereof.

[0005] The first object of the present invention is to provide a pre-load water-control composite plugging agent for repeated fracturing of old wells. The load plugging agent comprises the following raw materials: water-based epoxy resin emulsion, curing agent, cement, dispersant, nylon fiber and magnesium oxide. The mass ratio of the water-based epoxy resin emulsion, curing agent, cement, dispersant, nylon fiber and magnesium oxide is 10-15:10-13:18-25:0.4-0.6:0.2-0.6:0.04-0.08.

[0006] Furthermore, the mass ratio of the water-based epoxy resin emulsion, the curing agent, the cement, the dispersant, the nylon fiber and the magnesium oxide is 10:10:18:0.4:0.2:0.04.

[0007] Furthermore, the waterborne epoxy resin emulsion is prepared by the following steps:

[0008] Dissolve EP-20 in propylene glycol methyl ether and heat to a fixed temperature to obtain a transparent solution;

[0009] Then, polyethylene glycol-2000 was added to the transparent solution, and then boron trifluoride ether was dropped into the solution. After being stirred for 5-7 hours at a temperature, the solution was cooled to room temperature, and distilled water was added and stirred evenly to obtain a water-based epoxy resin emulsion.

[0010] Furthermore, the fixed temperature is 80-100°C.

[0011] Furthermore, the mass ratio of the EP-20 to propylene glycol methyl ether is 1:6-8.

[0012] Furthermore, the mass ratio of the added mass of polyethylene glycol-2000, boron trifluoride etherate, and distilled water to the mass ratio of the added mass of EP-20 is 10.43-11.17:0.14-0.16:17.57-20.33:1.

[0013] Furthermore, the curing agent is an amine curing agent.

[0014] Furthermore, the dispersant is a polycarboxylic acid type dispersant.

[0015] Furthermore, the pre-placed water-controlling composite plugging agent has a pressure bearing strength of ≥25MPa, a bonding strength of ≥5MPa, an injection viscosity of ≤70mPas, and a shrinkage rate of ≤10%.

[0016] The second object of the present invention is to provide a method for preparing a pre-placed water-controlling composite plugging agent for repeated fracturing of old wells, comprising:

[0017] The water-based epoxy resin emulsion, curing agent, cement, dispersant, nylon fiber and magnesium oxide are uniformly mixed to obtain a pre-water control composite plugging agent.

[0018] Beneficial effects of the present invention:

[0019] 1. The present invention uses epoxy resin EP-20 as a raw material to synthesize water-based epoxy resin emulsion, and then scientifically mixes the water-based epoxy resin emulsion with a curing agent, cement, a dispersant, nylon fiber, and magnesium oxide to obtain a pre-water-controlling composite plugging agent, which reduces the viscosity of the plugging agent during injection and improves the injection construction efficiency. When the pre-water-controlling composite plugging agent is cured, the epoxy resin and the curing agent are cured to form a cross-linked structure, and the nylon fiber is interspersed in the former network, and the cement particles are blocked in organic / inorganic interlocking micro-regions, which greatly improves the curing strength (compressive strength and bonding strength) and reduces the shrinkage rate. At the same time, the curing time of the plugging agent is greatly shortened by the addition of magnesium oxide, because the hydrolysis reaction of magnesium oxide can consume a large amount of water in the network, thereby reducing the curing time;

[0020] 2. Before repeated fracturing, the plugging agent liquid of the present invention is pumped and placed at the front end of the crack, where it solidifies under the action of temperature to form a "hard baffle", plugging the water channel of the oil well and forcing the repeated fracturing crack to turn;

[0021] 3. The present invention forms a new type of pre-water control composite plugging agent for repeated fracturing with the characteristics of two highs and three lows (high compressive strength, high bonding strength, low cost, low viscosity injection, and low shrinkage rate) through the compounding of organic and inorganic materials. The compressive strength is ≥25MPa, the bonding strength is ≥5MPa, the cost is ≤0.6000 / cubic meter, the injection viscosity is ≤70mPas, and the shrinkage rate is ≤10%.

[0022] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and claims. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] Preparation of plugging agent:

[0026] Dissolve 10g of EP-20 in 70g of propylene glycol methyl ether, heat in an oil bath to 90°C to form a transparent solution, add 108g of polyethylene glycol-2000 thereto, and then uniformly drop 1.5g of boron trifluoride ether as a catalyst after dissolution, stir at a constant temperature for 6h, cool to room temperature, add 180g of distilled water and stir to obtain a water-based epoxy resin emulsion;

[0027] Take 13g of epoxy resin emulsion, 11g of ethylenediamine curing agent, 20g of cement, 0.45g of polycarboxylic acid dispersant, 0.2g of nylon fiber and 0.04g of magnesium oxide, stir them evenly to form a mixed solution, and obtain a pre-water control composite plugging agent.

[0028] Example 2

[0029] Preparation of plugging agent:

[0030] 10g EP-20 was dissolved in 60g propylene glycol methyl ether, and the solution was heated in an oil bath to 85°C to form a transparent solution. 105g polyethylene glycol-2000 was added thereto, and after dissolution, 1.5g boron trifluoride ethyl ether was uniformly added dropwise as a catalyst. The solution was stirred at a constant temperature for 7h and then cooled to room temperature. 180g distilled water was added and stirred to obtain a waterborne epoxy resin emulsion.

[0031] Take 12g of epoxy resin emulsion, 10g of ethylenediamine curing agent, 20g of cement, 0.5g of polycarboxylic acid dispersant, 0.3g of nylon fiber and 0.05g of magnesium oxide, stir them evenly to form a mixed solution, and obtain a pre-water control composite plugging agent.

[0032] Example 3

[0033] Preparation of plugging agent:

[0034] 10 g of EP-20 was dissolved in 77 g of propylene glycol methyl ether, and the solution was heated in an oil bath to 90° C. to form a transparent solution, 104.3 g of polyethylene glycol-2000 was added thereto, and after dissolution, 1.4 g of boron trifluoride ethyl ether was uniformly added dropwise as a catalyst, and the solution was stirred at a constant temperature for 6 h, then cooled to room temperature, and 185 g of distilled water was added and stirred to obtain an aqueous epoxy resin emulsion;

[0035] Take 14g of epoxy resin emulsion, 10g of ethylenediamine curing agent, 18g of cement, 0.4g of polycarboxylic acid dispersant, 0.4g of nylon fiber and 0.06g of magnesium oxide, stir them thoroughly to form a mixed solution, and pre-place a water-controlling composite plugging agent.

[0036] Example 4

[0037] Preparation of plugging agent:

[0038] 10g EP-20 was dissolved in 75g propylene glycol methyl ether, and the solution was heated to 100°C in an oil bath to form a transparent solution. 108g polyethylene glycol-2000 was added thereto, and after the solution was dissolved, 1.6g boron trifluoride ethyl ether was uniformly added dropwise as a catalyst. The solution was stirred at a constant temperature for 5h and then cooled to room temperature. 190g distilled water was added and stirred to obtain a waterborne epoxy resin emulsion.

[0039] Take 15g of epoxy resin emulsion, 13g of ethylenediamine curing agent, 25g of cement, 0.6g of polycarboxylic acid dispersant, 0.5g of nylon fiber and 0.07g of magnesium oxide, stir them evenly to form a mixed solution, and obtain a pre-water control composite plugging agent.

[0040] Example 5

[0041] Preparation of plugging agent:

[0042] 10 g of EP-20 was dissolved in 80 g of propylene glycol methyl ether, and the solution was heated to 95° C. in an oil bath to form a transparent solution. 107 g of polyethylene glycol-2000 was added thereto. After dissolution, 1.5 g of boron trifluoride ethyl ether was uniformly added dropwise as a catalyst. The solution was stirred at a constant temperature for 6 h and then cooled to room temperature. 200 g of distilled water was added and stirred to obtain an aqueous epoxy resin emulsion.

[0043] Take 10g of epoxy resin emulsion, 10g of ethylenediamine curing agent, 18g of cement, 0.4g of polycarboxylic acid dispersant, 0.6g of nylon fiber and 0.08g of magnesium oxide, stir them evenly to form a mixed solution, and obtain a pre-water control composite plugging agent.

[0044] Example 6

[0045] Preparation of plugging agent:

[0046] Dissolve 10g EP-20 in 80g propylene glycol methyl ether, heat in an oil bath to 85°C to form a transparent solution, add 111.7g polyethylene glycol-2000 thereto, and then uniformly drop 1.6g boron trifluoride ethyl ether as a catalyst after dissolution, stir at a constant temperature for 7h, cool to room temperature, add 203.3g distilled water and stir to obtain a water-based epoxy resin emulsion;

[0047] Take 15g of epoxy resin emulsion, 12g of ethylenediamine curing agent, 25g of cement, 0.5g of polycarboxylic acid dispersant, 0.4g of nylon fiber and 0.06g of magnesium oxide, stir them evenly to form a mixed solution, and obtain a pre-water control composite plugging agent.

[0048] Comparative Example 1

[0049] Preparation of plugging agent:

[0050] The epoxy resin emulsion was prepared in the same manner as in Example 5;

[0051] Take 10g of epoxy resin emulsion, 10g of ethylenediamine curing agent, 18g of cement, 0.4g of polycarboxylic acid dispersant, and 0.6g of nylon fiber, stir them thoroughly to form a mixed solution to obtain a plugging agent.

[0052] The plugging agents (liquids) obtained in Examples 1-6 and Comparative Example 1 were pumped and placed at the front end of the cracks for consolidation. The curing time was recorded, and the physical properties of the obtained plates were tested. The test results are shown in Table 1.

[0053] Table 1

[0054]

[0055]

[0056] The curing time in Table 1 is the complete curing time recorded in the on-site construction.

[0057] It can be seen from the data in Table 1 that the compressive strength, bonding strength and shrinkage rate of the plugging agents obtained in Examples 1-6 are better than the corresponding performances of the plugging agent obtained in Comparative Example 1, and the curing time of the plugging agents obtained in Examples 1-6 is shorter than the curing time of the plugging agent obtained in Comparative Example 1, which is conducive to repeated fracturing construction.

[0058] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pre-water control composite plugging agent for repeated fracturing of old wells, comprising the following raw materials: water-based epoxy resin emulsion, curing agent, cement, dispersant, nylon fiber and magnesium oxide, wherein the mass ratio of the water-based epoxy resin emulsion, curing agent, cement, dispersant, nylon fiber and magnesium oxide is 10-15:10-13:18-25:0.4-0.6:0.2-0.6:0.04-0.

08.

2. The pre-water control composite plugging agent for repeated fracturing of old wells according to claim 1, characterized in that: The mass ratio of the water-based epoxy resin emulsion, the curing agent, the cement, the dispersant, the nylon fiber and the magnesium oxide is 10:10:18:0.4:0.2:0.

04.

3. The pre-water control composite plugging agent for repeated fracturing of old wells according to claim 1, characterized in that: The aqueous epoxy resin emulsion comprises the following steps: Dissolve EP-20 in propylene glycol methyl ether and heat to a fixed temperature to obtain a transparent solution; Then, polyethylene glycol-2000 was added to the transparent solution, and then boron trifluoride ether was dropped into the solution. After being stirred for 5-7 hours at a temperature, the solution was cooled to room temperature, and distilled water was added and stirred evenly to obtain a water-based epoxy resin emulsion.

4. The method for preparing a pre-water control composite plugging agent for repeated fracturing of old wells according to claim 3, characterized in that: The fixed temperature is 80-100°C.

5. The method for preparing a pre-water control composite plugging agent for repeated fracturing of old wells according to claim 3, characterized in that: The mass ratio of the EP-20 to propylene glycol methyl ether is 1:6-8.

6. The method for preparing a pre-water control composite plugging agent for repeated fracturing of old wells according to claim 3, characterized in that: The mass ratio of the added mass of polyethylene glycol-2000, boron trifluoride etherate, and distilled water to the mass ratio of the added mass of EP-20 is 10.43-11.17:0.14-0.16:17.57-20.33:

1.

7. The pre-water control composite plugging agent for repeated fracturing of old wells according to claim 1, characterized in that: The curing agent is an amine curing agent.

8. The pre-water control composite plugging agent for repeated fracturing of old wells according to claim 1, characterized in that: The dispersant is a polycarboxylic acid type dispersant.

9. A pre-water control composite plugging agent for repeated fracturing of old wells according to any one of claims 1 to 8, characterized in that: The pre-placed water-controlling composite plugging agent has a pressure bearing strength of ≥25MPa, a bonding strength of ≥5MPa, an injection viscosity of ≤70mPas, and a shrinkage rate of ≤10%.

10. A method for preparing a pre-water control composite plugging agent for repeated fracturing of old wells, characterized in that: The pre-water control composite plugging agent according to any one of claims 1 to 9 is prepared, comprising: The water-based epoxy resin emulsion, curing agent, cement, dispersant, nylon fiber and magnesium oxide are uniformly mixed to obtain a pre-water control composite plugging agent.

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