Curing liquid for improving well cementation quality of oily well wall interface and application thereof

Abstract

The invention belongs to the field of oil and gas well cementation and oilfield chemistry, and particularly relates to a curing liquid for improving the cementation quality of oily well wall interface cementation and application thereof, the curing liquid comprises the following raw materials by weight: 100 parts of oil well cement, 1 part of a fluid loss agent, 1-2 parts of an enhancer, and 44 parts of water; the interface reinforcing agent is a mixture of a silane coupling agent KH560, sodium methyl silicate and Tween 60, the oily well wall is an oil-based drilling fluid drilling well wall or a coal rock well wall, the curing liquid contains a special reinforcing agent, and the cementing quality of the curing liquid and the oily well wall is obviously superior to that of conventional oil well cement paste; the problem that the enhancement effect is lost after a traditional enhanced prepad fluid modified oily well wall interface is scoured by oil well cement paste is solved; the problem that oily well wall interface modification cannot meet requirements due to prepad fluid leakage is avoided, and the problems that oil well cement paste is too long in setting time and slow in strength development after a traditional interface reinforcing agent is added into the oil well cement paste are solved.

Description

Technical Field

[0001] The present invention belongs to the field of oil and gas well cementing and oilfield chemistry, and specifically relates to a solidifying liquid for improving the cementing quality of the oily well wall interface and its application. Background Art

[0002] With the development of oil and gas resources, the construction of oil and gas wells has gradually expanded towards unconventional oil and gas reservoirs (such as shale oil, shale gas, tight oil and gas, coalbed methane, etc.) in terms of exploitation needs, and the well types of drilling have gradually developed towards complex structure wells (high-angle wells, branch wells, large-reach wells, horizontal wells, etc.). In order to reduce the risks of the drilling process, prevent oil and gas layer pollution, and improve the success rate of well construction, oil-based or mixed oil drilling fluids are generally used in the completion section to make the well wall have certain oily characteristics, or for the development of coalbed methane, the well wall coal rock itself has oily characteristics, and the oil wettability of the oil-rich well wall interface will affect the bonding and adhesion between the cement sheath of the cemented oil well and the well wall, thereby reducing the cementing quality.

[0003] Aiming at the problem of poor cementing quality caused by oil wetting at the oily well wall interface, Wang Li, Zheng Fei and others developed a pre-fluid that can improve the wettability of the oily well wall interface by adding a surfactant that can improve the wettability of the well wall to the cementing pre-fluid to improve the quality of coal-rock cementing. However, there are certain problems with the method of using pre-fluid to improve the wettability of the oily well wall interface. After the pre-fluid flushes the oily well wall interface, the cementing oil well cement slurry will flush the oily well wall again for a long time, which can easily flush the surfactant adsorbed on the surface of the oily well wall to improve the wettability of the oily well wall surface, so that the oily well wall will recover the oil wetting, thereby losing the effect of improving the cementing quality of the oily well wall. To this end, some researchers have developed an erosion-resistant interface enhancer by adding a silane coupling agent and a surfactant to the pre-fluid, and formed a pre-fluid system suitable for the corresponding pre-fluid system. However, the subsequent long-term cementing still causes problems such as reduced erosion enhancement effect, or the loss of the pre-fluid system causing some oil-based wellbore walls to be unable to fully contact with the erosion-resistant interface enhancement pre-fluid system. Therefore, it is a more effective way to directly add an enhancer that can improve the wettability of the oil-based wellbore wall to the oil well cement slurry to form a solidifying liquid that improves the cementing quality of the oil-based wellbore wall interface. The solidifying liquid that improves the cementing quality of the oil-based wellbore wall interface is to directly add an enhancer to the oil well cement slurry to improve the cementing quality of the oil-based wellbore wall. It has two main advantages: (1) It can eliminate the problem that ordinary surfactants are not resistant to erosion of oil-based cement slurry after being adsorbed on the surface of the oil-based wellbore wall as enhancers; (2) It can prevent the loss of pre-fluid during construction, resulting in the problem that some oil-based wellbore walls cannot contact with the pre-fluid.

[0004] Although adding surfactants, silane coupling agents, etc. to oil well cement slurry can improve the bonding quality of the oil-based well wall interface, most of them will affect the properties of the oil well cement slurry, such as the setting time and strength. Selecting a strengthening agent with little effect on the performance of the oil well cement slurry is of great significance for the development of oil well cement slurry that can improve the bonding quality of the oil-based well wall. Summary of the invention

[0005] The purpose of the present invention is to provide a solidifying liquid for improving the cementing quality of oil-based well wall. The solidifying liquid contains a special strengthening agent. The cementing quality of the solidifying liquid with the oil-based well wall is significantly better than that of conventional oil well cement slurry, and the solidifying liquid has excellent comprehensive performance.

[0006] The solidifying liquid for improving the cementing quality of oil-based well wall described in the present invention comprises, by weight, 100 parts of oil well cement, 1 part of fluid loss reducer, 1-2 parts of interface enhancer, and 44 parts of water. The enhancer is a mixture of silane coupling agent KH560, sodium methyl silicate, and Tween 60; by weight ratio: silane coupling agent KH560: sodium methyl silicate: Tween 60 = (15-25): (60-80): (7-10).

[0007] The oil-based wellbore interface is an oil-based drilling fluid wellbore or a coal-rock wellbore.

[0008] The fluid loss reducer is selected from one of the oil well cement fluid loss reducers prepared by copolymerization of a plurality of ethylene monomers. For example, a copolymer of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) with acrylamide and acrylic acid; a copolymer of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) with N, N-dimethylacrylamide and maleic anhydride; a copolymer of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) with N, N-dimethylacrylamide, acrylamide and maleic anhydride, and other types of fluid loss reducers.

[0009] The oil well cement is selected from oil well G grade cement.

[0010] The water is fresh water.

[0011] The specific preparation process is: mixing and stirring oil well cement, fluid loss reducer, strengthening agent and water.

[0012] In the present invention, the super strong interface connection ability of silane coupling agent KH560 and surfactant Tween 60 is utilized to improve the bonding quality of the interface between oil well cement slurry and oily well wall, and the cementing quality is improved, and Tween 60 is not easy to foam when added to the oil well cement slurry; the super strong adsorption ability of sodium methyl silicate on the surface of oil well cement particles is utilized to reduce the adsorption of silane coupling agent KH560 on the surface of oil well cement particles, prevent the super slow setting of oil well cement slurry, that is, prevent the setting time of oil well cement slurry from being too long due to the addition of silane coupling agent KH560, and improve the strength characteristics of oil well cement slurry; in addition, sodium methyl silicate can also assist in improving the bonding quality between oil well cement stone and oily well wall.

[0013] Compared with the prior art, the present invention can solve the problem that the oil-based wellbore interface modified by the traditional enhanced pre-fluid system loses its enhancement effect after being flushed by oil well cement slurry; it can also avoid the problem that the wettability modification of the oil-based wellbore fails to meet the requirements due to the loss of pre-fluid; it can also solve the problem that after the traditional interface enhancer is added to the cement slurry, the cement slurry coagulation time is too long and the strength development is slow. DETAILED DESCRIPTION

[0014] Example 1 A solidifying liquid for improving the cementing quality of oil-based well wall, the raw materials of which are composed of 100 parts of oil well cement, 44 parts of water, 1 part of fluid loss reducing agent and 1 part of strengthening agent in parts by weight.

[0015] The reinforcing agent, in parts by weight, comprises the following raw materials: 15 parts of silane coupling agent KH560, 78 parts of sodium methyl silicate and 7 parts of Tween 60.

[0016] The fluid loss reducer is a copolymer of 2-acrylamide-2-methylpropane sulfonic acid, acrylamide and acrylic acid.

[0017] Example 2 A solidifying liquid for improving the cementing quality of oil-based well wall, the raw materials of which are composed of 100 parts of oil well cement, 44 parts of water, 1 part of fluid loss reducing agent and 1.5 parts of strengthening agent in parts by weight.

[0018] The reinforcing agent, in parts by weight, comprises the following raw materials: 20 parts of silane coupling agent KH560, 72 parts of sodium methyl silicate and 8 parts of Tween 60.

[0019] The fluid loss reducer is a copolymer of 2-acrylamide-2-methylpropane sulfonic acid, acrylamide and acrylic acid.

[0020] Example 3 A solidifying liquid for improving the cementing quality of oil-based well wall, the raw materials of which are composed of 100 parts of oil well cement, 44 parts of water, 1 part of fluid loss reducing agent and 2 parts of strengthening agent in parts by weight.

[0021] The reinforcing agent is composed of the following raw materials in parts by weight: 25 parts of silane coupling agent KH560, 65 parts of sodium methyl silicate and 10 parts of Tween 60.

[0022] The fluid loss reducer is a copolymer of 2-acrylamide-2-methylpropane sulfonic acid, acrylamide and acrylic acid.

[0023] Comparative Example 1 The curing liquid, in parts by weight, comprises the following raw materials: 100 parts of oil well cement, 44 parts of water, and 1 part of fluid loss reducer.

[0024] The fluid loss reducer is a copolymer of 2-acrylamide-2-methylpropane sulfonic acid, acrylamide and acrylic acid.

[0025] Comparative Example 2 The curing liquid, in parts by weight, comprises the following raw materials: 100 parts of oil well cement, 44 parts of water, 1 part of fluid loss reducer, and 0.42 parts of strengthening agent.

[0026] The reinforcing agent, in parts by weight, comprises the following raw materials: 20 parts of silane coupling agent KH560 and 8 parts of Tween 60.

[0027] The fluid loss reducer is a copolymer of 2-acrylamide-2-methylpropane sulfonic acid, acrylamide and acrylic acid.

[0028] Comparative Example 3 The curing liquid, in parts by weight, comprises the following raw materials: 100 parts of oil well cement, 44 parts of water, 1 part of fluid loss reducer, and 1 part of strengthening agent.

[0029] The reinforcing agent, in parts by weight, comprises 75 parts of silane coupling agent KH560 and 25 parts of surfactant CAEO-15.

[0030] The fluid loss reducer is a copolymer of 2-acrylamide-2-methylpropane sulfonic acid, acrylamide and acrylic acid.

[0031] Experimental example Cut the oil-based wellbore core (sand and mudstone are soaked in oil-based or mixed oil drilling fluid for 16 hours, and coal rock is directly cored) into a cylinder with a diameter of 25mm and a height of 50mm, and put it in the middle of a mold with an inner diameter of 40mm. Then, pour solidifying liquid into the gap between the coal rock and the mold. After it solidifies, place a steel column with a length of 24mm and a height of 60mm on the upper end of the coal rock. Use a press to squeeze the steel column to test the friction between the coal rock and the oil well cement stone. The maximum reading of the press divided by the external surface area of ​​the oil-based wellbore core cylinder is the bonding strength of the oil well cement stone and the oil-based wellbore core.

[0032] Table 1 Interface bonding strength and oil well cement strength .

[0033] According to the data in Table 1, compared with Comparative Example 1, the compressive strength of Example 1, Example 2, and Example 3 is similar to that of Comparative Example 1, but the interface bonding strength of Example 1, Example 2, and Example 3 is significantly improved, indicating that the present invention is very effective in improving the interface bonding strength of oil-based well walls. The 24h compressive strength of Comparative Example 2 is 16.5MPa, which is much lower than the compressive strength of Comparative Example 1 and Examples 1-3. This is mainly due to the presence of silane coupling agent, which has a strong retarding effect on oil well cement slurry, resulting in a significant decrease in the strength of oil well cement slurry. The 24h compressive strength of Comparative Example 3 is 9.3MPa, which is much lower than the compressive strength of Comparative Example 1 and Examples 1-3. This is similar to Comparative Example 2, which is mainly due to the presence of silane coupling agent, which has a strong retarding effect on oil well cement slurry, resulting in a significant decrease in the strength of oil well cement slurry. In Examples 1-3, the introduction of sodium methyl silicate interferes with the adsorption of silane coupling agent on the surface of oil well cement particles, so that the strength of oil well cement slurry is not significantly damaged. In addition, since the compressive strength of Comparative Example 2 is significantly reduced, the interface bonding strength between it and the oil-rich well wall core is significantly reduced, while Examples 1-3 have good interface bonding strength with the oil-rich well wall core.

[0034] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to the embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A solidifying fluid for improving the cementing quality of oil-based wellbore interface, characterized in that: The raw material composition is as follows: 100 parts of oil well cement, 1 part of fluid loss reducer, 1-2 parts of strengthening agent and 44 parts of water; the strengthening agent is a mixture of silane coupling agent KH560, sodium methyl silicate and Tween 60.

2. The solidifying liquid for improving the cementing quality of the oil-based well wall interface according to claim 1, characterized in that: Calculated by weight ratio: silane coupling agent KH560: sodium methyl silicate: Tween 60 = (15-25): (60-80): (7-10).

3. The solidifying liquid for improving the cementing quality of the oil-based well wall interface according to claim 1, characterized in that: The fluid loss reducer is selected from one of the oil well cement fluid loss reducers prepared by copolymerization of a variety of ethylene monomers.

4. The solidifying liquid for improving the cementing quality of the oil-based well wall interface according to claim 1, characterized in that: The monomer is a copolymer of 2-acrylamide-2-methylpropanesulfonic acid, acrylamide and acrylic acid, or a copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N, N-dimethylacrylamide and maleic anhydride, or a copolymer of 2-acrylamide-2-methylpropanesulfonic acid, N, N-dimethylacrylamide, acrylamide and maleic anhydride.

5. The solidifying liquid for improving cementing quality of oil-based wellbore interface according to claim 1, characterized in that: The oil well cement is mainly selected from oil well G grade cement.

6. The solidifying liquid for improving the cementing quality of the oil-based well wall interface according to claim 1, characterized in that: The oil-based wellbore interface is an oil-based drilling fluid wellbore or a coal-rock wellbore.

7. Use of the solidifying fluid for improving cementing quality at the oil-based well wall interface as claimed in claim 1 in cementing.