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...

Examples

Embodiment 1

[0029] Embodiment 1 (blank cement slurry system)

[0030] Formula: 100 parts of high sulfate-resistant grade G oil well cement, 0.5 parts of sodium polystyrene sulfonate, 1.0 parts of polyvinylpyrrolidone, 0.2 parts of sodium gluconate and 40 parts of water.

[0031] The mineral components of high sulfate-resistant grade G oil well cement are shown in Table 1.

[0032] Table 1 Mineral components of high sulfate-resistant grade G oil well cement

[0033]

Embodiment 2

[0035] Formula: 100 parts of high sulfate-resistant grade G oil well cement, 0.8 parts of modified polybenzimidazole fiber, 0.5 parts of sodium polystyrene sulfonate, 1.0 part of polyvinylpyrrolidone, 0.2 parts of sodium gluconate and 40 parts of water.

[0036] The composition of the high sulfate-resistant type G grade oil well cement is the same as in Example 1.

[0037] The process of preparing modified polybenzimidazole fiber is as follows:

[0038] 1) Chopping polybenzimidazole fibers to obtain chopped polybenzimidazole fibers with an average length of 300 μm; 2) adding chopped polybenzimidazole fibers to a beaker, and then weighing 97% concentrated nitric acid Measure 200mL into the beaker, stir well, seal it with plastic wrap and tie it tightly with a rubber band. Put the beaker into the water bath and fix it. The heating temperature of the water bath is 60° C., and the constant temperature heating treatment is carried out for 3 hours. After the treatment, take out th...

Embodiment 3

[0040] Formula: 100 parts of high sulfate-resistant grade G oil well cement, 1.5 parts of modified polybenzimidazole fiber, 0.6 parts of polynaphthalene sodium sulfonate, 1.5 parts of hydroxyethyl cellulose, 0.3 parts of sodium borate and 44 parts of water.

[0041] The composition of the high sulfate-resistant type G grade oil well cement is the same as in Example 1. The composition and preparation of the modified polybenzimidazole fiber are the same as in Example 2.

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...

Examples

Embodiment 1

[0029] Embodiment 1 (blank cement slurry system)

[0030] Formula: 100 parts of high sulfate-resistant grade G oil well cement, 0.5 parts of sodium polystyrene sulfonate, 1.0 parts of polyvinylpyrrolidone, 0.2 parts of sodium gluconate and 40 parts of water.

[0031] The mineral components of high sulfate-resistant grade G oil well cement are shown in Table 1.

[0032] Table 1 Mineral components of high sulfate-resistant grade G oil well cement

[0033]

Embodiment 2

[0035] Formula: 100 parts of high sulfate-resistant grade G oil well cement, 0.8 parts of modified polybenzimidazole fiber, 0.5 parts of sodium polystyrene sulfonate, 1.0 part of polyvinylpyrrolidone, 0.2 parts of sodium gluconate and 40 parts of water.

[0036] The composition of the high sulfate-resistant type G grade oil well cement is the same as in Example 1.

[0037] The process of preparing modified polybenzimidazole fiber is as follows:

[0038] 1) Chopping polybenzimidazole fibers to obtain chopped polybenzimidazole fibers with an average length of 300 μm; 2) adding chopped polybenzimidazole fibers to a beaker, and then weighing 97% concentrated nitric acid Measure 200mL into the beaker, stir well, seal it with plastic wrap and tie it tightly with a rubber band. Put the beaker into the water bath and fix it. The heating temperature of the water bath is 60° C., and the constant temperature heating treatment is carried out for 3 hours. After the treatment, take out th...

Embodiment 3

[0040] Formula: 100 parts of high sulfate-resistant grade G oil well cement, 1.5 parts of modified polybenzimidazole fiber, 0.6 parts of polynaphthalene sodium sulfonate, 1.5 parts of hydroxyethyl cellulose, 0.3 parts of sodium borate and 44 parts of water.

[0041] The composition of the high sulfate-resistant type G grade oil well cement is the same as in Example 1. The composition and preparation of the modified polybenzimidazole fiber are the same as in Example 2.

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