Slow-release gas expanding agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of oil wells, in particular to a slow-release type gas expanding agent and a preparation method and application thereof.The slow-release type gas expanding agent is prepared from, by weight, 1000-2000 parts of water, 800-1000 parts of alkali-soluble resin monomers, 125-250 parts of a nitrogen type gas forming agent, 1-5 parts of a surfactant, 1-5 parts of a dispersing agent and 5-20 parts of an initiator. Alkali-soluble resin monomers are polymerized to form alkali-soluble resin serving as a wall material, a nitrogen type gas forming agent serves as a core material, and in the alkaline environment of cement paste, the wall material is gradually dissolved, the core material nitrogen type gas forming agent is released and reacts in the cement paste to generate nitrogen, so that the gas forming rate is greatly reduced, and a gas expansion source is continuously provided for the plastic stage of the cement paste.

Description

Technical Field

[0001] The present invention relates to the technical field of oil wells, and in particular to a slow-release gas expansion agent and a preparation method and application thereof. Background Art

[0002] In the construction of oil well cementing, good bonding between cement sheath and formation and casing is the basis for achieving effective interlayer isolation. If the interface bonding is poor, it will affect the normal production of the oil well and the implementation of subsequent production increase measures. The volume shrinkage of cement sheath is one of the main reasons for poor interlayer isolation or crossflow. It has been confirmed that as long as there is a micro-gap of 10um at the interface, gas crossflow will occur, and when the micro-gap is 50~70um, it will lead to unqualified cementing quality. With the deepening of oil and gas exploration, the number of high-pressure natural gas wells drilled in Tarim Oilfield, Southwest Oil and Gas Field and other domestic fields has continued to increase, and gas crossflow after cementing and gas pressure at the wellhead often occur. In order to improve the bonding ability of cement stone interface and reduce the risk of air crossflow in the ring, expansion agent is usually added to oil well cement.

[0003] The application number is 201510112506.6, and the subject name is oil well cement gas expansion agent. It relates to an oil well cement gas expansion agent, which is composed of 30-40 parts by weight of nitrogen type gas generating agent and 60-70 parts by weight of stabilizer, wherein the gas generating agent is a sulfonylhydrazine compound, and the stabilizer is at least one of silicon dioxide and calcium silicate; the expansion agent starts to release nitrogen when the temperature reaches 35°C under alkaline conditions, and through the action of the stabilizer in the component, the tiny bubbles can be evenly distributed in the cement slurry and the gas generated is only nitrogen, which does not corrode the pipe, and can effectively compensate for the pressure loss and volume shrinkage during the solidification of the cement slurry, and prevent oil, gas and water from channeling during cementing. However, the prior art ignores the problem that the gas generation rate of nitrogen type gas generating agent is too fast and the initial gas generation temperature is low. Especially in cementing construction in high temperature areas in summer, the gas can be generated by reaction when the cement slurry is mixed on the ground, and gas loss is prone to occur, resulting in insufficient expansion rate.

[0004] The application number is 201610696723.9, and the subject name is gas expansion agent for cementing of medium and high temperature wells and its application. It relates to a gas expansion agent for cementing of medium and high temperature wells and its application. The gas expansion agent includes: 20 to 30 parts by weight of nitrogen-type gas generating agent, 5 to 10 parts by weight of gas generating aid, 0.5 to 1.0 parts by weight of foam stabilizer, and 40 to 90 parts by weight of filler. The nitrogen-type gas generating agent is a sulfonyl hydrazide compound, and the gas generating aid is selected from at least one of urea, sodium benzoate, zinc oxide, aluminum oxide and lead oxide. The gas expansion agent can meet the on-site cementing construction requirements of a circulation temperature of 80 to 120°C, effectively compensate for the pressure loss and volume shrinkage during the solidification process of cement stone, improve the cementing quality of cement stone, and improve the anti-gas collection ability. The prior art uses a gas generating aid to regulate the gas generating temperature and gas generating rate of the nitrogen-type gas generating agent, but this control effect is limited, and it is impossible to continue to gas and expand in the plastic stage of the cement slurry. Summary of the invention

[0005] In order to solve the above technical problems, embodiments of the present invention provide a slow-release gas expansion agent and a preparation method and application thereof.

[0006] To achieve the above object, the embodiments of the present invention adopt the following technical solutions: On the one hand, an embodiment of the present invention provides a slow-release gas expansion agent, which includes the following raw materials, in parts by weight: 1000-2000 parts of water, 800-1000 parts of alkali-soluble resin monomers, 125-250 parts of nitrogen-type gas-generating agents, 1-5 parts of surfactants, 1-5 parts of dispersants, and 5-20 parts of initiators.

[0007] In some embodiments, the alkali-soluble resin monomer includes an acrylate monomer and a carboxylic acid monomer, and the mass of the carboxylic acid monomer is 5-10% of the mass of the alkali-soluble resin monomer.

[0008] In some embodiments, the acrylic ester monomer is at least one of methyl methacrylate, ethyl methacrylate, styrene, ethyl acrylate, and butyl acrylate, and multiple monomers may be mixed in any proportion when used.

[0009] In some embodiments, the carboxylic acid monomer is at least one of acrylic acid, methacrylic acid, and itaconic acid, and multiple monomers can be mixed in any proportion when used.

[0010] In some embodiments, the nitrogen-type gas generating agent is at least one of benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide, 4,4'-oxybisbenzenesulfonyl hydrazide, and azodicarbonamide, and multiple types thereof can be mixed in any proportion when used.

[0011] In some embodiments, the surfactant is at least one of polyethylene glycol, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate, and multiple surfactants can be mixed in any proportion when used.

[0012] In some embodiments, the dispersant is at least one of methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose, and multiple types thereof can be mixed in any proportion when used. The initiator is at least one of azobisisobutyronitrile, dibenzoyl peroxide, and tert-butyl perbenzoate, and multiple types thereof can be mixed in any proportion when used.

[0013] On the other hand, an embodiment of the present invention provides a method for preparing a slow-release gas expansion agent, comprising the following steps: (1) mixing water, a nitrogen-type gas generating agent and a surfactant and dispersing them under ultrasound to obtain a suspension; (2) adding a dispersant and an alkali-soluble resin monomer to the suspension obtained in step (1), stirring at 1000 r / min for 10 to 20 min, to form oil phase microdroplets encapsulating the gas-generating agent in the water phase; (3) The oil phase droplets encapsulating the gas generating agent obtained in step (2) are heated to 75-80°C, and then the initiator is added dropwise with stirring for 20-30 min. After the addition is completed, the reaction is carried out at a constant temperature for 4-5 h; (4) The reaction product obtained in step (3) is cooled, centrifuged, washed, and dried to obtain a slow-release gas expansion agent.

[0014] In yet another aspect, an embodiment of the present invention provides a use of a slow-release gas expansion agent in oil well cement.

[0015] In some embodiments, the slow-release gas expansion agent is added in an amount of 0.2% to 0.4% by mass of the oil well cement.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The gas expansion agent of the present invention adopts a microcapsule coating method, with alkali-soluble resin monomers polymerized to form alkali-soluble resin as the wall material, and nitrogen-type gas-generating agent as the core material. In the alkaline environment of cement slurry, the wall material gradually dissolves, releasing the core nitrogen-type gas-generating agent, and reacting in the cement slurry to produce nitrogen, so that the gas generation rate is greatly reduced, and a gas expansion source is continuously provided for the plastic stage of the cement slurry.

[0017] 2. The gas expansion agent of the present invention benefits from the coating effect of the wall material on the core material, which increases the initial gas emission temperature of the gas expansion agent and reduces the expansion gas source lost due to the reaction during the construction stage due to the high ambient temperature.

[0018] 3. The gas expansion agent of the present invention benefits from the reduction of the gas generation rate, and the tiny bubbles can be evenly distributed in the cement slurry, which has little effect on the mechanical properties of the cement stone. The gas generated is nitrogen, which is safe, stable and does not corrode the casing.

[0019] 4. The gas expansion agent of the present invention uses water as solvent and adopts suspension polymerization to prepare the expansion agent microcapsules. The preparation method is simple, the production process is environmentally friendly, the wall thickness is controllable, and the wall material dissolution rate can be controlled by controlling the amount of alkali-soluble resin monomer, thereby controlling the gas generation rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The graph is a graph showing the cumulative gas release rate versus time for Example 1, Example 2 and Comparative Example 1. DETAILED DESCRIPTION

[0021] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in some embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present disclosure.

[0022] Example 1

[0023] A slow-release gas expansion agent suitable for oil well cement, the preparation method comprising the following steps: (1) 190 g of water, 25 g of a nitrogen-type gas generating agent, and 0.5 g of a surfactant were mixed and dispersed under ultrasound for 30 min, wherein the nitrogen-type gas generating agent was benzenesulfonyl hydrazide and the surfactant was polyethylene glycol; (2) adding 0.2 g of a dispersant, 80 g of an acrylate monomer and 10 g of a carboxylic acid monomer to the suspension system obtained in step (1), and stirring at 1000 r / min for 10 min, wherein the dispersant is methyl cellulose, the acrylate monomer is styrene, and the carboxylic acid monomer is acrylic acid; (3) Dissolve 2.5g of initiator in 10g of styrene to form liquid A for use. Place the suspension system obtained in step (2) in a reaction container, continue stirring and heat to 80°C to maintain a constant temperature. Add liquid A to the reaction container in a dropwise manner for 20 minutes. After the dropwise addition is completed, continue the constant temperature reaction for 4 hours and then cool to room temperature. The initiator is azobisisobutylnitrile; (4) After the reaction is completed and the product is cooled to room temperature, it is centrifuged, washed, and dried to obtain a powder, which is a slow-release gas expansion agent.

[0024] Example 2

[0025] A slow-release gas expansion agent suitable for oil well cement, the preparation method comprising the following steps: (1) 100 g of water, 12.5 g of a nitrogen-type gas generating agent and 0.1 g of a surfactant were mixed and dispersed under ultrasound for 20 min, wherein the nitrogen-type gas generating agent was azodicarbonamide and the surfactant was sodium dodecyl sulfate; (2) adding 0.1 g of a dispersant, 82 g of an acrylate monomer and 5 g of a carboxylic acid monomer to the suspension system obtained in step (1), and stirring at 1000 r / min for 20 min, wherein the dispersant is hydroxyethyl cellulose, the acrylate monomer is 23 g of methyl methacrylate and 59 g of butyl acrylate, and the carboxylic acid monomer is methacrylic acid; (3) Dissolve 1g of initiator in 10g of butyl acrylate to form liquid A for use. Place the suspension system obtained in step (2) in a reaction container, continue stirring and heat to 80°C to maintain a constant temperature. Add liquid A to the reaction container in a dropwise manner for 30 minutes. After the dropwise addition is completed, continue the constant temperature reaction for 5 hours and then cool to room temperature. The initiator is dibenzoyl peroxide; (4) After the reaction is completed and the product is cooled to room temperature, it is centrifuged, washed, and dried to obtain a powder, which is a slow-release gas expansion agent.

[0026] Example 3

[0027] A slow-release gas expansion agent suitable for oil well cement, the preparation method comprising the following steps: (1) In parts by weight, 250 g of water, 20 g of a nitrogen-type gas generating agent, and 0.3 g of a surfactant were mixed and dispersed under ultrasound for 25 min, wherein the nitrogen-type gas generating agent was p-toluenesulfonyl hydrazide and the surfactant was sodium dodecylbenzenesulfonate; (2) adding 0.5 g of a dispersant, 85 g of an acrylate monomer and 5 g of a carboxylic acid monomer to the suspension system obtained in step (1), and stirring at 1000 r / min for 15 min, wherein the dispersant is carboxymethyl cellulose, the acrylate monomer is 47.5 g of ethyl methacrylate and 37.5 g of ethyl acrylate, and the carboxylic acid monomer is itaconic acid; (3) Dissolve 0.5g of initiator in 10g of ethyl acrylate to form liquid A for use. Place the suspension system obtained in step (2) in a reaction container, continue stirring and heat to 75°C to maintain a constant temperature. Add liquid A to the reaction container in a dropwise manner for 25 minutes. After the dropwise addition is completed, continue the constant temperature reaction for 4.5 hours and then cool to room temperature. The initiator is tert-butyl perbenzoate; (4) After the reaction is completed and the product is cooled to room temperature, it is centrifuged, washed, and dried to obtain a powder, which is a slow-release gas expansion agent.

[0028] Example 4

[0029] A slow-release gas expansion agent suitable for oil well cement, the preparation method comprising the following steps: (1) In parts by weight, 200 g of water, 15 g of a nitrogen-type gas generating agent and 0.2 g of a surfactant are mixed and dispersed under ultrasound for 20 min, wherein the nitrogen-type gas generating agent is 4,4'-oxybisbenzenesulfonyl and the surfactant is sodium dodecyl sulfate; (2) adding 0.2 g of a dispersant, 83 g of an acrylate monomer and 7 g of a carboxylic acid monomer to the suspension system obtained in step (1), and stirring at 1000 r / min for 20 min, wherein the dispersant is hydroxypropyl cellulose, the acrylate monomer is 31 g of styrene and 52 g of butyl acrylate, and the carboxylic acid monomer is acrylic acid; (3) Dissolve 1.5g of initiator in 10g of butyl acrylate to form liquid A for use. Place the suspension system obtained in step (2) in a reaction container, continue stirring and heat to 80°C to maintain a constant temperature. Add liquid A to the reaction container in a dropwise manner for 30 minutes. After the dropwise addition is completed, continue the constant temperature reaction for 5 hours and then cool to room temperature. The initiator is azobisisobutylnitrile; (4) After the reaction is completed and the product is cooled to room temperature, it is centrifuged, washed, and dried to obtain a powder, which is a slow-release gas expansion agent.

[0030] Comparative Example 1 A nitrogen expansion agent commonly used in oil well cement is prepared by grinding 30g of azodicarbonamide, 30g of silicon dioxide and 40g of calcium carbonate.

[0031] Comparative Example 2 A nitrogen expansion agent commonly used in oil well cement is prepared by grinding and mixing 30g of p-benzenesulfonyl hydrazide, 30g of silicon dioxide, 40g of calcium carbonate, 3g of zinc oxide and 1g of sodium dodecyl sulfate.

[0032] The above expansion agents were tested and analyzed, and the results are as follows: In order to simulate the environment of saturated Ca(OH)2 in oil well cement, 200 mL of saturated Ca(OH)2 aqueous solution was prepared and poured into a conical flask, and then the conical flask was fixed in a constant temperature water bath at 60°C, and 1g of the gas expansion agent provided in Example 1 and 1g of the gas expansion agent provided in Comparative Example 1 were added respectively, and the cumulative gas release rate of the expansion agent was determined by the displacement gas method. Figure 1 This is a graph showing the relationship between the cumulative gas release rate of Example 1, Example 2 and Comparative Example 1 in a saturated Ca(OH)2 aqueous solution and time.

[0033] Depend on Figure 1The results show that, compared with the comparative example 1, the gas generation amount of the examples 1 and 2 has a significant slowing trend over time. After 30 minutes, the cumulative gas release rates of the examples 1 and 2 are 25.6% and 13.8%, respectively, while the cumulative gas release rate of the comparative example 1 after 30 minutes is 97.0%, which is almost completely gassed. This shows that the gas expansion agent of the embodiment of the present invention can control the gas generation rate and can slowly release nitrogen in the alkaline environment (pH=12~13) of the cement slurry.

[0034] The gas expansion agent provided in Example 3, Example 4 and Comparative Example 2 was added to the oil well cement, and the expansion performance and comprehensive performance of the obtained oil well cement were tested. The oil well cement slurry formula used was as follows: 1000g G-grade oil well cement, 4g gas expansion agent, 16g fluid loss additive, 1g retarder, 5g dispersant, 2g defoamer, and 447g tap water.

[0035] The sources and models of cement and admixtures are as follows: (1) Grade G oil well cement, purchased from Sichuan Jiahua Special Cement Co., Ltd.; (2) The fluid loss additive comes from PetroChina Sichuan Qing Drilling Downhole Operation Company, and its main ingredient is 2-acrylamide-2-methylpropane sulfonic acid (AMPS); (3) The retarder comes from PetroChina Sichuan Qing Drilling Downhole Operation Company, and its main component is cellulose derivatives; (4) The dispersant comes from PetroChina Sichuan Qing Drilling Downhole Operations Company, and its main component is polystyrene sulfonate dispersant; (5) The defoaming agent comes from PetroChina Sichuan Qing Drilling Downhole Operations Company, and its main ingredient is silicone defoaming agent.

[0036] The preparation method of oil well cement slurry refers to GB / T 19139-2012 "Test methods for oil well cement".

[0037] According to SYT 5504.3-2013 "Evaluation Methods for Oil Well Cement Admixtures Part 8: Expansion Agents", the volume changes of cement slurries in Example 3, Example 4 and Comparative Example 2 were tested. The experimental results are shown in Table 1.

[0038] Table 1 Test results of cement slurry volume change rate over 24 hours

[0039] As can be seen from Table 1, at 40°C, the volume of the cement slurries in Examples 3 and 4 is still shrinking, while the volume of the cement slurry in Comparative Example 2 has expanded, indicating that the slow-release gas expansion agent of the present invention is more adaptable to the working temperature of oil well cement, and will not lose gas due to the reaction when the cement slurry is mixed on the ground due to the low initial gasification temperature, resulting in insufficient expansion rate. At 60°C, the volume expansion of the cement slurries in Examples 3 and 4 is greater than that in Comparative Example 2 in 24h, the reason is that the gasification rate of Comparative Example 2 is too fast, and the initial gasification temperature is low, so some gas is lost during the test. The slow-release gas expansion agent of the present invention, due to the microcapsule coating method, has an increased initial gasification temperature and a slow gasification rate, which can continuously provide a gas expansion source for the cement slurry.

[0040] The comprehensive properties of the cement slurries of Examples 1-4 and Comparative Examples 1-2 were tested in accordance with GB / T 19139-2012 “Test Methods for Oil Well Cement”. The test results are shown in Table 2.

[0041] Table 2 Comprehensive performance results of cement slurry

[0042] As can be seen from Table 2, the gas expansion agent of the embodiment of the present invention has no adverse effect on the comprehensive performance of cement slurry, the cement slurry has good fluidity, the free liquid is less than 0.1%, the API water loss is less than 50 mL, the water loss performance is good, and the rheological properties are good. Although Comparative Example 1 and Comparative Example 2 have no effect on the fluidity of cement slurry, API water loss and other slurry properties, the 48h compressive strength of cement paste is relatively low. In comparison, the 48h compressive strength of cement paste of Example 1 to Example 4 is higher. This is because the gas expansion agent of the present invention has a slow gas evolution rate in cement slurry, and the tiny bubbles can be evenly distributed in the cement slurry, which has less effect on the mechanical properties of cement paste.

[0043] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0044] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A sustained-release gas expansion agent, characterized in that: The composition comprises the following raw materials in parts by weight: 1000-2000 parts of water, 800-1000 parts of alkali-soluble resin monomer, 125-250 parts of nitrogen-type gas generating agent, 1-5 parts of surfactant, 1-5 parts of dispersant and 5-20 parts of initiator.

2. A slow-release gas expansion agent according to claim 1, characterized in that: The alkali-soluble resin monomers include acrylate monomers and carboxylic acid monomers, and the mass of the carboxylic acid monomers is 5-10% of the mass of the alkali-soluble resin monomers.

3. A sustained-release gas expansion agent according to claim 2, characterized in that: The acrylic acid ester monomer is at least one of methyl methacrylate, ethyl methacrylate, styrene, ethyl acrylate and butyl acrylate.

4. A sustained-release gas expansion agent according to claim 2, characterized in that: The carboxylic acid monomer is at least one of acrylic acid, methacrylic acid and itaconic acid.

5. A sustained-release gas expansion agent according to claim 1, characterized in that: The nitrogen type gas generating agent is at least one of benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide, 4,4'-oxybisbenzenesulfonyl hydrazide and azodicarbonamide.

6. A slow-release gas expansion agent according to claim 1, characterized in that: The surfactant is at least one of polyethylene glycol, sodium dodecylbenzene sulfonate and sodium dodecyl sulfate.

7. A slow-release gas expansion agent according to claim 1, characterized in that: The dispersant is at least one of methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose, and the initiator is at least one of azobisisobutyronitrile, dibenzoyl peroxide and tert-butyl perbenzoate.

8. A method for preparing a slow-release gas expansion agent as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: (1) mixing water, a nitrogen-type gas generating agent and a surfactant and dispersing them under ultrasound to obtain a suspension; (2) adding a dispersant and an alkali-soluble resin monomer to the suspension obtained in step (1), stirring at 1000 r / min for 10 to 20 min, to form oil phase microdroplets encapsulating the gas-generating agent in the water phase; (3) The oil phase droplets encapsulating the gas generating agent obtained in step (2) are heated to 75-80°C, and then the initiator is added dropwise with stirring for 20-30 min. After the addition is completed, the reaction is carried out at a constant temperature for 4-5 h; (4) The reaction product obtained in step (3) is cooled, centrifuged, washed, and dried to obtain a slow-release gas expansion agent.

9. Use of the slow-release gas expansion agent according to any one of claims 1 to 7 or the slow-release gas expansion agent prepared by the preparation method according to claim 8 in oil well cement.

10. The use according to claim 9, characterized in that: The added amount of the slow-release gas expansion agent accounts for 0.2% to 0.4% of the mass of the oil well cement.

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