METHOD FOR ELIMINATING BEHIND-CASING FLOWS AND INTER-CASING PRESSURE IN OIL AND GAS WELLS Russian patent published in 2015 - IPC E21B33/138 C09K8/467 

FIELD: oil and gas industry.

SUBSTANCE: in method for elimination of behind-casing flows and inter-casing pressures, which involves preparation of aerated grouting mortars of light weight and normal density, their series delivery to a production string and squeezing to behind-casing and inter-casing spaces with squeezing liquid, as aerated grouting mortars of light weight and normal density there used are sedimentation stable fine-aerated solutions with densities of not higher than 1650 kg/m³ and not lower than 1800 kg/m³, which contain no extra Portland cement and heat-resistant plasticising and expanding additive including kaolin clay thermally activated at the temperature of 900÷1000°C with specific surface of 300÷400 m²/kg, aluminium sulphate, boric acid and an Aeroplast air-entraining additive excluding formation of stable foam, and mixing liquid at the following ratio of components, wt %: non-extra Portland cement 85-75, kaolin clay 10-18, aluminium sulphate 4.7-6.1, boric acid 0.2-0.5, Aeroplast air-entraining additive 0.1-0.4, mixing liquid over 100% till water-mixed ratios of 0.63÷0.65 m³/t and 0.40÷0.50 m³/t are obtained, with that, first, sedimentation stable aerated light-weight grouting mortar is delivered with controlled density of not more than 1650 kg/m³, then, aerated grouting mortar of normal density of not more than 1950 kg/m³ is delivered; with that, required densities of grouting mortars are provided by variation of a water-mixed ratio, intensity and duration of mixing, and squeezing is performed till partial displacement of aerated light-weight grouting mortar from behind-casing (inter-casing) space with squeezing liquid heated up to 50÷60°C during winter season and at cementing of low-temperature wells.

EFFECT: improving cementing quality.

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