METHOD OF WELL CEMENTING UNDER CONDITIONS OF ABNORMALLY LOW FORMATION PRESSURE Russian patent published in 2013 - IPC E21B33/13 

FIELD: oil and gas industry.

SUBSTANCE: method of well cementing under conditions of abnormally low formation pressure involves pumping to the well of nonshrinkable foam cement grouting with plugging capability coefficient of not less than 5.6 and with expansion value of 0.5-1.0%; for that purpose, density of that grouting is calculated for formation conditions based on prevention of absorption of foam cement grouting with the weakest formation, then, PZT D0-400 basic cement, Gorkal-70 cement, rubber granules and polypropylene fibre are mixed in dry form in the specified ratios. The obtained dry mixture is mixed with fresh water based on the ratio of that water to the obtained dry mixture of 0.5-0.65. Volume of such cement grouting is assumed in terms of 1-3 m³ per 1 m of developed formation thickness. Then, foaming agent in quantity of 0.5-1.5 kg is added to the obtained grouting in terms of 1 m³, and that grouting is passed through mixer to the well head, where it is mixed with gas or air until design density of cement grouting is obtained. After that, foam cement grouting is subject to treatment with magnetic field with intensity of 0.8-1.2 kilooersted.

EFFECT: improving cementing efficiency owing to increasing the plugging capability of the used foam cement grouting and stability of its foam structure, improving the resistance of cement stone on its basis to temperature, impact and corrosion impacts.

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