Cement slurry system for cementation of geothermal well, and preparation method thereof

Abstract

The invention discloses a cement slurry system for cementation of a geothermal well and a preparation method thereof to overcome the problem that conventional cement slurry systems are not applicableto cementation of geothermal wells with both super-high temperature and super-large temperature difference. The cement slurry system provided by the invention comprises dry ash, a fluid loss additiveBFL-12L for oil well cement and a high-temperature retarder BRT-22L, wherein the addition amount of the fluid loss additive BFL-12L for oil well cement is 6%-8% by weight of the dry ash; the additionamount of the high-temperature retarder BRT-22L is 5%-9% by weight of the dry ash; the dry ash comprises G-grade oil well cement, a high-temperature anti-declining agent BHS-70S accounting for 50%-100% of the G-grade oil well cement, micro-silica accounting for 0%-5% of the G-grade oil well cement and a high-temperature-resistant stabilizing agent BCS-400S accounting for 0.6%-1.0% of the G-grade oil well cement. The thickening time of the cement slurry system at a temperature of 220 DEG C is adjustable in a range of 200 min to 400 min; strength starts from the top of the system within 72 h, which satisfies usage requirements under the condition of co-existing of ultra-high temperature and super-large temperature difference in geothermal well cementing; and the cement slurry system can alsoeffectively guarantee compressive strength at a temperature of 200 DEG C or above and prevents the strength of cement stone from declining.

Description

technical field [0001] The invention relates to the field of cement, in particular to a geothermal well cementing cement slurry system and a preparation method thereof. Background technique [0002] my country is relatively rich in geothermal resources. The total amount of geothermal resources accounts for about 7.9% of the world's total, and the recoverable reserves are equivalent to 462.65 billion tons of standard coal. steam), geothermal resources can not only provide clean energy, but also a hot brine resource and natural fertilizer water resource for extracting industrial raw materials such as bromine, iodine, borax, potassium salt, and ammonium salt. In today's environment with huge environmental pressure and the promotion of new energy development, geothermal resources will be fully utilized. [0003] The cementing of geothermal wells is similar to the cementing of ultra-high temperature oil and gas wells. During the injection process, the cement slurry will experienc...

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Problems solved by technology

[0004] At present, there are few cement slurry systems actually applied by foreign manufacturers in the geothermal well cementing site. At present, there is no report on the cement slurry formula with a thickening time of 180°C reaching 200 minutes to return to the wellhead and strength within 72 hours.

In addition, the existing cement slurry system has been exposed to high temperatures above 110°C for a long time, and there will be a relatively large strength decline

Previous studies have shown that adding silica fume that accounts for 35% or more of cement can prevent such decline, but existing research and actual production on site show that silica fume can no longer effectively resist this kind of decline, even with 35% and above silicon Flour (quartz sand) cement will also experience a relatively large strength decline at high temperatures above 150°C. After the strength of the cement declines, a series of problems such as annular pressure and reduced recovery will occur, and even lead to the well scrapped

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