Modified polybenzimidazole fiber reinforcement cement paste system

Abstract

The invention discloses a modified polybenzimidazole fiber reinforcement cement paste system. The system comprises the following components in parts by weight: 100 parts of high sulfate resistance grade-G oil well cement, 0.2 to 3.0 parts of modified polybenzimidazole fiber, 0 to 40 pars of quartz sand, 0.5 to 2.5 parts of a dispersant, 1.0 to 6.0 parts of a fluid loss agent, 0.2 to 3.0 parts of aretarder, and 38 to 70 parts of water. The modified polybenzimidazole fiber is performed by performing surface modification on the polybenzimidazole fiber as follows: firstly, performing oxidation treatment on the polybenzimidazole fiber, then, performing low temperature plasma treatment on the polybenzimidazole fiber, and finally, performing coupling treatment on the polybenzimidazole fiber. Feinforcement cement paste has the characteristics of high tensile strength, breaking strength and low elasticity modulus, the modified polybenzimidazole fiber is high in temperature resistance capacityand good in dispersibility in cement paste, set cement is excellent in mechanical property, and the system has important application value for improving the cementing quality of high temperature deepwells and shale gas wells.

Description

technical field [0001] The invention relates to a modified polybenzimidazole fiber toughened cement slurry system, which belongs to the field of petroleum and natural gas exploration and development, and is suitable for the cementing operation of oil and gas wells with high requirements on the mechanical properties of the cement sheath. Background technique [0002] In the cementing of oil and gas wells, the cement slurry is injected into the casing or the annular space between the casing and the well wall to solidify and harden to form a cement sheath. The cement sheath plays the role of supporting the casing and isolating the underground fluid. Since cement stone is a brittle material with very low tensile strength, it is easy to be brittle to form micro-cracks and micro-annulus during pressure testing, perforating, mining, fracturing and other operations, resulting in the failure of the cement sheath. Therefore, it is very important to add toughening materials to cement s...

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Problems solved by technology

[0003] At present, the toughening agents for cement stone mainly include latex, rubber particles and fibers, etc. The disadvantage of latex is that the comprehensive performance is difficult to adjust; the disadvantage of rubber particles is that it has poor compatibility with cement slurry; the disadvantage of fibers is that the commonly used polypropylene Fiber and cellulose fiber have poor temperature resistance, and the toughening effect of the fiber will fail when used in high-temperature wells; while carbon fiber, etc. have poor dispersion in cement slurry, which is not conducive to exerting the toughening effect

Li Ming of Southwest Petroleum University and others added carbon fiber to cement slurry (Li Ming, Yang Yujia, Guo Xiaoyang. Mechanical properties of carbon fiber reinforced oil well cement[J]. Journal of Composite Materials, 2015,32(3):782-788 ), this method improves the toughness of cement stone, but does not completely solve the problem of carbon fiber dispersion in cement slurry

Li Ming and others also added brucite fiber to the cement slurry (Li Ming, Yang Yujia, Jin Jianzhou, et al. The enhancement effect and mechanism of brucite fiber on the mechanical properties of cement stone[J]. Natural Gas Industry, 2015,35(6):82-86), this method also improves the mechanical properties of cement stone, but the improvement effect of brucite fiber on the mechanical properties of cement stone is limited

Therefore, the current research focuses on how to improve the existing fiber tougheners such as poor dispersion effect and poor temperature resistance.

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