Toughened anti-channeling agent for cement and toughened cement for cementing shale gas horizontal well

Abstract

The invention relates to cement paste used when a shale gas horizontal well is cemented, and a toughened additive added to the cement paste, and belongs to the technical field of oil-gas well cement engineering. A toughened anti-channeling agent for cement is prepared from butadiene styrene rubber powder and re-dispersible rubber latex powder at the mass ratio of 2 to 1 in a mixing manner, wherein the butadiene styrene rubber powder is subjected to treatment comprising the following steps before use: firstly, preparing a silane coupling agent solution with the mss percent content being 1.5%; adding butadiene styrene rubber powder, standing for 24 hours, and then filtering; and drying in the sun, wherein the system is stable in performance after the cement paste is prepared; the thickening time is easy to adjust; the water loss is smaller than 30ml; free fluid with an inclination angle of 45 degrees and the difference of densities are 0; the compressive strength at 50 DEG C for 24 hours is greater than 30MPa; the applicable temperature range is 50-120 DEG C; the thickening time is 110-240 minutes; and the toughened anti-channeling agent for cement is added to the toughened cement for cementing the shale gas horizontal well. The cement paste system disclosed by the invention is good in stability, and low in water loss and leakage, and can meet the requirements of multistage fracturing of the shale gas horizontal well on the cement paste system.

Description

technical field [0001] The invention relates to a cement slurry used in shale gas horizontal well cementing and a toughening additive added therein, belonging to the technical field of oil and gas well cementing engineering. Background technique [0002] The cement slurry in well cementing is used to seal the annular space between the casing and the formation to isolate the oil, gas and water layers and support the casing. The later development of shale gas horizontal wells adopts large-scale staged fracturing. It must withstand high-strength pressure and multiple impacts. Cement is a high-strength, highly brittle hydraulic cementitious material. When it is subjected to high-strength mechanical impact, it will produce micro and macro cracks, lose its sealing performance, and cause oil, gas and water to escape. At the same time, poor stability of cement slurry settlement or excessive water loss and precipitation can easily form high-edge water bands in the horizontal section...

AI Technical Summary

Problems solved by technology

[0003] At present, the improvement of the brittleness of cement stone is limited to adding latex, rubber powder and fiber toughening materials or a mixture of fiber and rubber powder to improve toughness. Obviously; the fiber has a great influence on the strength, and the toughening effect is limited; the rubber powder is easy to affect the stability of the cement slurry, and the fiber can not obviously improve its defects after mixing with it, so that its comprehensive performance can meet the solidification performance of shale gas horizontal wells. well demand

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