BACKFILL FOR CEMENTING WELLS WITH HIGH GAS RATIO Russian patent published in 2012 - IPC C09K8/46 E21B33/138 

FIELD: chemistry.

SUBSTANCE: invention relates to well construction, particularly backfill compositions used when cementing casing columns, mainly with high gas ratio. The backfill contains portland cement, oxyethylcellulose, a plasticiser, an antifoaming agent - modified organosilicon reagent POLYCEM DF, a modified vinyl acetate copolymer GASBLOCK and water. The backfill additionally contains an expansion agent - calcium oxide or calcium hydrosulphoaluminate and a setting accelerator - calcium chloride, the plasticiser is a substance the active ingredient of which is sulphonated melamine formaldehyde (CEMPLAST MF), or a product of condensation of naphthalene sulphonic acid and formaldehyde S-3, or polyether carboxylate (Melflux), with the following ratio of components, pts.wt: portland cement 95.0-99.9; modified vinyl acetate copolymer GASBLOCK 1.0-2.0; said expansion agent - up to 5.0; oxyethylcellulose 0.3-0.5; said plasticiser 0.6-0.8; calcium chloride - up to 2.0; said antifoaming agent 0.1-0.2; water 47-52. Total weight content of the dry mixture of cement and expansion agent is equal to 100 pts.wt, and total weight ratio of the modified vinyl acetate copolymer GASBLOCK and the expansion agent in the material is equal to 1:(2.5-5.0), respectively.

EFFECT: preventing migration of gas in the columned space after well cementing using the disclosed backfill.

4 cl, 2 tbl, 1 ex