METHOD OF CEMENTING CASING PIPE OF GAS WELL UNDER CONDITIONS OF PERMAFROST ROCKS Russian patent published in 2008 - IPC E21B33/14 

FIELD: oil and gas industry.

SUBSTANCE: invention refers to methods of cementing casing pipe of gas well under conditions of permafrost rocks-PFR. The method consists in lowering casing pipe equipped with a back valve of BV (back valve)-type without a gate element- ball below the zone of PFR, in pumping buffer fluid, the first portion of cement grout, into the casing pipe, in withdrawing drilling agent from casing string borehole annulus by means of forcing the first portion of cement grout through a bottom of the casing pipe to bottom hole of the well, in pumping the second portion of cement grout, in control over pressure in annulus at bottom hole, and in conditioning the well for the period of cement hardening; also as buffer fluid aerated cement grout is pumped with a degree of aeration at well bottom hole of 0.2-0.4; as the first and the second portions cement grouts are pumped in volumes calculated from reduced mathematical dependences. As the first portion there is pumped cement grout of composition, wt %: portland cement of 1-G type 69.4-69.9; polypropylene fiber 0.04-0.07, water 30.06-30.53; as the second portion there is pumped cement grout of composition, wt %: backfill arctic cement "Arccement" 66.7-68.9, water 31.1-33.3. When density of fluid flowing out of the well coincides with density of cement grout pumped into the well, forcing the first portion through is terminated and a gate element-ball is thrown into the casing pipe, whereupon the second portion of the cement grout is pumped with adjusting pressure at the well head in a string space by throttling.

EFFECT: upgraded efficiency of cementing casing pipe of gas well under conditions of PFR.

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