Cement slurry with long-term-integrity cement sheath for heavy-oil thermal-recovery well and preparation method thereof

Abstract

The invention provides a cement slurry with long-term-integrity cement sheath for a heavy-oil thermal-recovery well. The cement slurry comprises, by weight, 100 parts of thermally responsive cement, 25 to 65 parts of water and 0.2 to 8 parts of a cement slurry aid. The thermally responsive cement comprises 30 to 60 parts of oil well cement, 10 to 20 parts of active silicon powder, 0 to 10 parts of hollow glass beads and 10 to 50 parts of a thermally responsive composite material. The thermally responsive composite material comprises 20 to 30 parts of clay mineral, 10 to 20 parts of fly ash and / or vulcanic ash, 5 to 20 parts of rubber powder and / or latex powder, 3 to 10 parts of carbon fiber, 10 to 15 parts of nanometer silicon dioxide, 5 to 10 parts of calcined magnesia, 10 to 20 parts of ultrafine superfine slag powder and 5 to 10 parts of inorganic whiskers. The cement slurry provided by the invention can solidify at normal temperature; and set cement can resist long-term high temperature, and the mechanical properties and thermal properties of the set cement in a high temperature environment are integrally adaptive to strata and casing pipes.

Description

technical field [0001] The invention relates to well cementing slurry and a preparation method thereof, in particular to a heavy oil thermal recovery well cementing slurry and a preparation method thereof. Background technique [0002] Viscous oil is heavy oil, which refers to the oil with API between 10°-22.3°, and its viscosity is between 100-10000cp. The annual production of heavy oil accounts for an increasing proportion of the total oil production. Due to its high viscosity, it is difficult to extract, so it needs to be exploited by the method of tertiary oil recovery (EOR). Among them, thermal recovery is a widely used recovery method in the world, mainly including steam huff and puff, steam flooding, steam-assisted gravity drainage and other methods. The high-temperature characteristics of thermal recovery wells and the continuous injection of high-temperature steam have extremely high requirements on the integrity of the wellbore. There are still many problems in t...

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Problems solved by technology

The above fracturing, cracking or micro-annulus will cause the annulus to lose its integrity

After the annulus loses its integrity, the downhole interlayer isolation will be lost firstly, and the injected high-temperature steam will channel through and even leak to the ground, which will affect the safety and economy of thermal recovery wells; The protective effect of support is weakened, and the casing is more prone to damage, which further affects the safety and economy of thermal recovery wells

However, the cement sheath formed by the existing cementing cement slurry undergoes multiple high and low temperature cycles, the performance of various aspects decreases rapidly, the failure rate is high, it is difficult to ensure long-term integrity, and the life of the oil well is greatly shortened.

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