METHOD OF CEMENTING CASING STRING IN WELL Russian patent published in 2024 - IPC E21B33/14 C09K8/467 

FIELD: mining.

SUBSTANCE: invention relates to a method for cementing a casing in a well. Method involves successive pumping of a washing spacer fluid and portions of cement mortar, the first portion of cement mortar with density of 1,520–1,640 kg/m³ in a volume which provides filling of the annular space in the well in the interval from mouth to 100 m from the bottomhole. First portion of the cement mortar contains a dry cement mixture, a water loss reducer, an antifoaming agent and water. Dry cement mixture is represented by a mixture with the following ratio of components, wt.pts.: portland cement – 100, lightening inert filler – 10–23, fibrous material – 0.1–0.6, water loss reducer “ПВС-ВР” or “ПВА” – 0.5, antifoaming agent “ПЕНТА-465” or FOBR – 0.05, at a ratio of dry cement mixture to water of 100 wt.pts. to 60 wt.pts. respectively, second portion of cement mortar, forcing through portions of cement mortar, performing process exposure for the time of waiting for hardening of cement mortar. Second portion of the cement mortar is pumped with density of 1,880–1,920 kg/m³ in a volume which provides filling of the annular space of the well in interval of 100 m from the bottomhole. Second portion of the cement mortar contains a dry cement mixture and water at a ratio of the dry cement mixture to water of 100 wt.pts. to 44 wt.pts. respectively, dry cement mixture used is a mixture of backfill portland cement and microcement, with the following ratio of components, wt.pts.: portland cement – 100, cement with particle size of 5 microns – 10–20.

EFFECT: increased efficiency of the method due to improved quality of cementing in wells with residual losses of drilling mud, elimination of filtration of cement mortar after opening of pores of permeable formations and increased tightness of cement lining at contact of cement stone-rock.

1 cl, 2 tbl