Flushing agent for well cementation of shale gas well and preparation method thereof

Abstract

The invention relates to the technical field of oil and gas well development, in particular to a flushing agent for well cementation of a shale gas well and a preparation method of the flushing agent. The flushing agent for well cementation of the shale gas well is prepared from the following raw materials in parts by weight: 1.5-3.4 parts of a compound surfactant, 2-4 parts of a lubricating drag reducer, 0.5-1 part of sodium silicate, 3-7 parts of potassium chloride and 80-150 parts of water. The compound surfactant is prepared from a cationic surfactant, a nonionic surfactant and an ampholytic surfactant according to the weight ratio of (0.3 to 0.8) to (0.8 to 1.8) to (0.4 to 0.9). The prepared flushing agent for well cementation of the shale gas well has high flushing rate and stability, and the cementing strength between a cement sheath and a casing pipe after well cementation can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas well development, and in particular to a flushing agent for shale gas well cementing and a preparation method thereof. Background Art

[0002] Improving cementing quality is one of the key technologies to ensure the life of shale gas wells and increase the recovery rate. The core issues that need to be solved to improve cementing quality are replacement and sealing. Replacement means that the drilling fluid retained in the annular space between the casing and the well wall is completely replaced by cement slurry; sealing requires that the cement ring has long-term good sealing performance. Replacement is a prerequisite for cement ring sealing. Only by flushing the drilling fluid and the adhering mud cake well can a high-quality cementing interface be provided for the cement slurry. Otherwise, it will be difficult to obtain long-term effective isolation. When drilling shale gas wells, oil-based or oil-in-water emulsion drilling fluids are required in the horizontal section. Oil-based or oil-in-water emulsion drilling fluids will make the well wall and casing wall prone to oil pollution and produce oil-wet interfaces, which will affect the bonding strength between the cement ring and the casing after cementing.

[0003] Patent technology document CN202010960073.0 discloses a shale gas well cementing oil-displacing flushing agent, which is calculated by weight as follows: 100 parts of water, 24-48 parts of emulsifier, 12-24 parts of cosolvent, and 6-12 parts of hydration inhibitor; wherein the emulsifier includes at least one of cetearyl alcohol polyoxyethylene ether, propylene glycol block polyether, and fatty alcohol polyoxyethylene ether potassium phosphate; the cosolvent is a weight ratio of (3-4): (1-2) isomeric alcohol polyoxyethylene ether and oleic acid polyoxyethylene ester; the hydration inhibitor includes polyethylene glycol, glucoside and / or oleyl alcohol polyoxyethylene ether. The flushing agent prepared by the present invention can effectively displace high-density oil-based drilling fluid, achieve interfacial wetting performance reversal, and ensure reservoir stability, but the invention uses a large amount of non-ionic surfactants, which are sensitive to temperature changes. Temperature increases may affect their performance and stability, affecting the cementing effect. Summary of the invention

[0004] In view of this, the purpose of the present invention is to propose a flushing agent for shale gas well cementing and a preparation method thereof, so as to develop a flushing agent for cementing oil-based drilling fluid, which has a high flushing efficiency and improves the bonding strength between the cement ring and the casing after cementing.

[0005] Based on the above purpose, the present invention provides a flushing agent for shale gas well cementing, which is prepared from the following raw materials in parts by weight: 1.5-3.4 parts of a compound surfactant, 2-4 parts of a lubricating drag reducer, 0.5-1 part of sodium silicate, 3-7 parts of potassium chloride and 80-150 parts of water.

[0006] Furthermore, the compound surfactant is composed of a cationic surfactant, a nonionic surfactant and an amphoteric surfactant in a weight ratio of 0.3-0.8:0.8-1.8:0.4-0.9.

[0007] Furthermore, the preparation method of the lubricating drag reducing agent is as follows:

[0008] (1) heating dodecyl glucoside and citric acid at 180-190° C. for 9-10 h, dispersing them in xylene, stirring them for 10-20 min, centrifuging them once, dispersing them in deionized water, stirring them for 10-20 min, centrifuging them twice, and vacuum drying them to obtain carbon microspheres;

[0009] (2) adding carbon microspheres, 2-bromoethanol and dicyclohexylcarbodiimide into dichloromethane, stirring at 60-70° C. for 2-3 h, washing, and separating to obtain brominated carbon microspheres;

[0010] (3) Adding carbon bromide microspheres and 1-methylimidazole into xylene, stirring at 60-70° C. for 30-40 min, washing, and separating to obtain a lubricating drag reducer.

[0011] Preferably, in step (1), the weight ratio of dodecyl glucoside to citric acid is 10:3-5.

[0012] Preferably, the rotation speed of the first centrifugation and the second centrifugation in step (1) is 8000-9000 rpm, and the time is 8-10 min.

[0013] Preferably, in step (2), the weight ratio of carbon microspheres, 2-bromoethanol, dicyclohexylcarbodiimide and dichloromethane is 10:1.2-2.4:0.05-0.1:50-60.

[0014] Preferably, in step (3), the weight ratio of brominated carbon microspheres, 1-methylimidazole and xylene is 10:0.7-1.4:50-60.

[0015] Preferably, the cationic surfactant is hexadecyltrimethylammonium chloride.

[0016] Preferably, the nonionic surfactant is a mixture of one or both of fatty alcohol polyoxyethylene ether AE0-7 and fatty alcohol polyoxyethylene ether AE0-9.

[0017] Preferably, the amphoteric surfactant is lauramidopropyl hydroxysulfobetaine.

[0018] Furthermore, the present invention also provides a method for preparing a flushing agent for shale gas well cementing, comprising the following steps: adding a lubricating drag reducer into water, ultrasonically dispersing for 10-20 minutes, heating to 50-60°C, adding a composite surfactant, sodium silicate and potassium chloride, stirring for 30-40 minutes, and cooling to room temperature to obtain a flushing agent for shale gas well cementing.

[0019] Beneficial effects of the present invention:

[0020] The present invention firstly adopts dodecyl glucoside and citric acid as raw materials, prepares carbon microspheres with long carbon chains and carboxyl groups on the surface through hydrothermal reaction, then chlorinates the carboxyl groups on the surface of the carbon microspheres, and further reacts with methylimidazole to obtain carbon microspheres with long carbon chains and imidazole salts on the surface, and then uses the carbon microspheres as lubricating and drag reducing agents and is compounded with surfactants to prepare flushing agents.

[0021] The lubricating drag reducing agent provided by the present invention can spread on the surface of the casing to wet the casing, and cooperate with a surfactant to displace the oil stains to achieve wetting reversal. In addition, the lubricating drag reducing agent spread on the surface can form ionic interaction with cement slurry to improve the bonding strength.

[0022] The flushing agent for shale gas well cementing provided by the present invention adopts carbon microspheres containing long carbon chains and imidazole salts on the surface, compounded with cationic surfactants, nonionic surfactants and amphoteric surfactants. Due to the charge effect, the entire system has high stability, the carbon microspheres can be evenly dispersed in the flushing agent for a long time, and the storage stability is improved. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0024] Embodiment 1:

[0025] (1) 10 g of dodecyl glucoside and 3 g of citric acid were heated at 180° C. for 9 h, then dispersed in 100 g of xylene, stirred for 10 min, centrifuged once at 8000 rpm for 8 min, dispersed in 100 g of deionized water, stirred for 10 min, centrifuged twice at 8000 rpm for 8 min, and vacuum dried to obtain carbon microspheres;

[0026] (2) adding 10 g of carbon microspheres, 1.2 g of 2-bromoethanol and 0.05 g of dicyclohexylcarbodiimide to 50 g of dichloromethane, stirring at 60° C. for 2 h, washing, and separating to obtain brominated carbon microspheres;

[0027] (3) 10 g of carbon bromide microspheres and 0.7 g of 1-methylimidazole were added to 50 g of xylene, stirred at 60° C. for 30 min, washed, and separated to obtain a lubricating drag reducer.

[0028] (4) 2 g of lubricating drag reducer was added to 80 g of water, ultrasonically dispersed for 10 min, heated to 50 °C, 0.3 g of hexadecyltrimethylammonium chloride, 0.8 g of fatty alcohol polyoxyethylene ether AE0-7, 0.4 g of lauramide propyl hydroxysulfobetaine, 0.5 g of sodium silicate and 3 g of potassium chloride were added, stirred for 30 min, and cooled to room temperature to obtain a flushing agent for shale gas well cementing.

[0029] Embodiment 2:

[0030] (1) 10 g of dodecyl glucoside and 4 g of citric acid were heated at 180° C. for 10 h, then dispersed in 100 g of xylene, stirred for 20 min, centrifuged once at 9000 rpm for 10 min, dispersed in 100 g of deionized water, stirred for 20 min, centrifuged twice at 9000 rpm for 10 min, and vacuum dried to obtain carbon microspheres;

[0031] (2) adding 10 g of carbon microspheres, 1.8 g of 2-bromoethanol and 0.08 g of dicyclohexylcarbodiimide to 55 g of dichloromethane, stirring at 65° C. for 2.5 h, washing, and separating to obtain brominated carbon microspheres;

[0032] (3) 10 g of carbon bromide microspheres and 1 g of 1-methylimidazole were added to 55 g of xylene, stirred at 65° C. for 35 min, washed, and separated to obtain a lubricating drag reducer.

[0033] (4) 3 g of lubricating drag reducer was added to 120 g of water, ultrasonically dispersed for 20 min, heated to 55 °C, 0.5 g of hexadecyltrimethylammonium chloride, 1 g of fatty alcohol polyoxyethylene ether AE0-7, 0.4 g of fatty alcohol polyoxyethylene ether AE0-7, 0.6 g of lauramide propyl hydroxysulfobetaine, 0.7 g of sodium silicate and 5 g of potassium chloride were added, stirred for 40 min, and cooled to room temperature to obtain a flushing agent for shale gas well cementing.

[0034] Embodiment 3:

[0035] (1) 10 g of dodecyl glucoside and 5 g of citric acid were heated at 190° C. for 10 h, then dispersed in 100 g of xylene, stirred for 20 min, centrifuged once at 9000 rpm for 10 min, dispersed in 100 g of deionized water, stirred for 20 min, centrifuged twice at 9000 rpm for 10 min, and vacuum dried to obtain carbon microspheres;

[0036] (2) adding 10 g of carbon microspheres, 2.4 g of 2-bromoethanol and 0.1 g of dicyclohexylcarbodiimide to 60 g of dichloromethane, stirring at 70° C. for 3 h, washing, and separating to obtain brominated carbon microspheres;

[0037] (3) 10 g of carbon bromide microspheres and 1.4 g of 1-methylimidazole were added to 60 g of xylene, stirred at 70° C. for 40 min, washed, and separated to obtain a lubricating drag reducer.

[0038] (4) 4 g of lubricating drag reducer was added to 150 g of water, ultrasonically dispersed for 20 min, heated to 60° C., 0.8 g of hexadecyltrimethylammonium chloride, 1.8 g of fatty alcohol polyoxyethylene ether AE0-9, 0.8 g of lauryl amide propyl hydroxysulfobetaine, 1 g of sodium silicate and 7 g of potassium chloride were added, stirred for 40 min, and cooled to room temperature to obtain a flushing agent for shale gas well cementing.

[0039] Comparative Example 1:

[0040] (1) 14 g of citric acid was heated at 180° C. for 10 h, then dispersed in 100 g of xylene, stirred for 20 min, centrifuged once at 9000 rpm for 10 min, dispersed again in 100 g of deionized water, stirred for 20 min, centrifuged twice at 9000 rpm for 10 min, and vacuum dried to obtain carbon microspheres;

[0041] (2) adding 10 g of carbon microspheres, 1.8 g of 2-bromoethanol and 0.08 g of dicyclohexylcarbodiimide to 55 g of dichloromethane, stirring at 65° C. for 2.5 h, washing, and separating to obtain brominated carbon microspheres;

[0042] (3) 10 g of carbon bromide microspheres and 1 g of 1-methylimidazole were added to 55 g of xylene, stirred at 65° C. for 35 min, washed, and separated to obtain a lubricating drag reducer.

[0043] (4) 3 g of lubricating drag reducer was added to 120 g of water, ultrasonically dispersed for 20 min, heated to 55 °C, 0.5 g of hexadecyltrimethylammonium chloride, 1 g of fatty alcohol polyoxyethylene ether AE0-7, 0.4 g of fatty alcohol polyoxyethylene ether AE0-7, 0.6 g of lauramide propyl hydroxysulfobetaine, 0.7 g of sodium silicate and 5 g of potassium chloride were added, stirred for 40 min, and cooled to room temperature to obtain a flushing agent for shale gas well cementing.

[0044] Comparative Example 2:

[0045] (1) 14 g of dodecyl glucoside was heated at 180° C. for 10 h, then dispersed in 100 g of xylene, stirred for 20 min, centrifuged once at 9000 rpm for 10 min, dispersed again in 100 g of deionized water, stirred for 20 min, centrifuged twice at 9000 rpm for 10 min, and vacuum dried to obtain carbon microspheres;

[0046] (2) adding 10 g of carbon microspheres, 1.8 g of 2-bromoethanol and 0.08 g of dicyclohexylcarbodiimide to 55 g of dichloromethane, stirring at 65° C. for 2.5 h, washing, and separating to obtain brominated carbon microspheres;

[0047] (3) 10 g of carbon bromide microspheres and 1 g of 1-methylimidazole were added to 55 g of xylene, stirred at 65° C. for 35 min, washed, and separated to obtain a lubricating drag reducer.

[0048] (4) 3 g of lubricating drag reducer was added to 120 g of water, ultrasonically dispersed for 20 min, heated to 55 °C, 0.5 g of hexadecyltrimethylammonium chloride, 1 g of fatty alcohol polyoxyethylene ether AE0-7, 0.4 g of fatty alcohol polyoxyethylene ether AE0-7, 0.6 g of lauramide propyl hydroxysulfobetaine, 0.7 g of sodium silicate and 5 g of potassium chloride were added, stirred for 40 min, and cooled to room temperature to obtain a flushing agent for shale gas well cementing.

[0049] Comparative Example 3:

[0050] (1) 10 g of dodecyl glucoside and 4 g of citric acid were heated at 180° C. for 10 h, then dispersed in 100 g of xylene, stirred for 20 min, centrifuged once at 9000 rpm for 10 min, dispersed in 100 g of deionized water, stirred for 20 min, centrifuged twice at 9000 rpm for 10 min, and vacuum dried to obtain carbon microspheres;

[0051] (2) 3 g of carbon microspheres were added to 120 g of water, ultrasonically dispersed for 20 min, heated to 55 ° C, added with 0.5 g of hexadecyl trimethyl ammonium chloride, 1 g of fatty alcohol polyoxyethylene ether AE0-7, 0.4 g of fatty alcohol polyoxyethylene ether AE0-7, 0.6 g of lauramide propyl hydroxysulfobetaine, 0.7 g of sodium silicate and 5 g of potassium chloride, stirred for 40 min, cooled to room temperature, and obtained a flushing agent for shale gas well cementing.

[0052] Comparative Example 4:

[0053] Heat 120g of water to 55°C, add 0.5g of hexadecyltrimethylammonium chloride salt, 1g of fatty alcohol polyoxyethylene ether AE0-7, 0.4g of fatty alcohol polyoxyethylene ether AE0-7, 0.6g of lauramide propyl hydroxysulfobetaine, 0.7g of sodium silicate and 5g of potassium chloride, stir for 40min, cool to room temperature, and obtain a flushing agent for shale gas well cementing.

[0054] Performance Test:

[0055] Flushing rate: According to the original petroleum and natural gas industry standard (SY / T5374-2000), the circular mold of the simulated casing in the flushing device is cleaned, wiped dry, and weighed m 0 Then, the round mold of the simulated casing was immersed in the oil-based drilling fluid D-OMEDRIL of Shandong Deshunyuan Petroleum Technology Co., Ltd., and then taken out, placed in the air, and then weighed. 1 The round mold with drilling fluid was placed in a device containing flushing fluid for 30 minutes. After flushing, the round mold was taken out and placed in air for 10 minutes. 2 , weigh. Calculate the flushing rate A according to the following formula:

[0056]

[0057] Stability: The prepared flushing solution was left to stand at room temperature for 10 days and the flushing efficiency was measured to evaluate the stability;

[0058] Interface bonding strength: Cement and water were mixed in a mass ratio of 100:40 and stirred evenly to obtain cementing cement slurry. The simulated casing was then immersed in the oil-based drilling fluid D-OMEDRIL of Shandong Deshunyuan Petroleum Technology Co., Ltd. and then taken out. The casing was flushed with a flushing fluid for 30 minutes. The flushed casing was placed in a mold, and cement slurry was poured into it. It was then placed in a constant temperature water bath at 80°C for curing. After 28 days of curing, the interface bonding strength was tested. The results are shown in Table 1.

[0059] Table 1 Performance test results

[0060]

[0061] Data analysis: From Examples 1-3 and Comparative Example 4, it can be seen that the flushing agent for shale gas well cementing prepared by the present invention has a high flushing rate and interface bonding strength. This is mainly because the lubricating drag reducer in the flushing fluid can spread on the solid surface to wet the solid, and the surfactant displaces the oil stain to achieve wetting reversal, and the lubricating drag reducer spread on the surface can form ionic interactions with the cement slurry to improve the interface bonding strength. It is worth mentioning that the flushing agent for shale gas well cementing prepared by the present invention has high stability. After standing for 10 days, the flushing rate has almost no change.

[0062] It can be seen from Example 2 and Comparative Examples 1-2 that in the preparation process of carbon microspheres, dodecyl glucoside and citric acid are indispensable. The cleaning rate of citric acid alone is only 85.3. This is mainly because dodecyl glucoside makes the surface of the carbon microspheres have long carbon chains, which helps them to replace oil stains. The cleaning rate of dodecyl glucoside alone will lead to a decrease in the interfacial bonding strength. This is mainly because the lack of citric acid will cause the surface of the carbon microspheres to lack carboxyl sites, making it difficult to graft imidazole salts and unable to be evenly distributed on the surface of the carbon microspheres.

[0063] It can be seen from Example 2 and Comparative Example 3 that the imidazole salts on the carbon microspheres have a significant effect on the flushing rate, interface bonding strength and stability, which is mainly because the imidazole salts on the carbon microspheres can improve the wetting reversal ability and interface bonding strength.

[0064] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A flushing agent for shale gas well cementing, characterized in that: The invention is prepared from the following raw materials by weight: 1.5-3.4 parts of compound surfactant, 2-4 parts of lubricating drag reducer, 0.5-1 parts of sodium silicate, 3-7 parts of potassium chloride and 80-150 parts of water; The composite surfactant is composed of a cationic surfactant, a nonionic surfactant and an amphoteric surfactant in a weight ratio of 0.3-0.8:0.8-1.8:0.4-0.9; The preparation method of the lubricating drag reducing agent is as follows: (1) heating dodecyl glucoside and citric acid at 180-190° C. for 9-10 h, dispersing them in xylene, stirring them for 10-20 min, centrifuging them once, dispersing them in deionized water, stirring them for 10-20 min, centrifuging them twice, and vacuum drying them to obtain carbon microspheres; (2) adding carbon microspheres, 2-bromoethanol and dicyclohexylcarbodiimide into dichloromethane, stirring at 60-70° C. for 2-3 h, washing, and separating to obtain brominated carbon microspheres; (3) adding the brominated carbon microspheres and 1-methylimidazole into xylene, stirring at 60-70° C. for 30-40 min, washing, and separating to obtain a lubricating drag reducer; In the step (1), the weight ratio of dodecyl glucoside to citric acid is 10:3-5.

2. The flushing agent for shale gas well cementing according to claim 1, characterized in that: The cationic surfactant is hexadecyltrimethylammonium chloride salt.

3. The flushing agent for shale gas well cementing according to claim 1, characterized in that: The nonionic surfactant is one or a mixture of two of fatty alcohol polyoxyethylene ether AE0-7 and fatty alcohol polyoxyethylene ether AE0-9.

4. The flushing agent for shale gas well cementing according to claim 1, characterized in that: The amphoteric surfactant is lauramide propyl hydroxysulfobetaine.

5. The flushing agent for shale gas well cementing according to claim 1, characterized in that: The rotation speed of the first centrifugation and the second centrifugation in step (1) is 8000-9000 rpm, and the time is 8-10 min.

6. The flushing agent for shale gas well cementing according to claim 1, characterized in that: In the step (2), the weight ratio of carbon microspheres, 2-bromoethanol, dicyclohexylcarbodiimide and dichloromethane is 10:1.2-2.4:0.05-0.1:50-60.

7. The flushing agent for shale gas well cementing according to claim 1, characterized in that: In the step (3), the weight ratio of brominated carbon microspheres, 1-methylimidazole and xylene is 10:0.7-1.4:50-60.

8. A method for preparing a flushing agent for shale gas well cementing according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: adding a lubricating drag reducing agent into water, ultrasonically dispersing for 10-20 minutes, heating to 50-60° C., adding a compound surfactant, sodium silicate and potassium chloride, stirring for 30-40 minutes, cooling to room temperature, and obtaining a flushing agent for shale gas well cementing.

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