CASING STRING CEMENTING METHOD IN WELL Russian patent published in 2020 - IPC E21B33/14 C09K8/467 C04B14/38 

FIELD: construction.

SUBSTANCE: invention relates to construction of oil wells, namely to methods of cementing a casing string in a well with residual or partial absorption of drilling mud or with abnormally low formation pressure. Proposed method comprises successive pumping of washing buffer fluid and portions of cement slurry. In this case two portions successively pumped cement slurry, a first portion of the cement slurry is pumped density 1520–1544 kg/m³ in volume providing filling casing annulus in a borehole in the range from mouth to 100 m from the face, wherein the first portion of the cement slurry contains a dry cement mixture, a water loss reducer - PVS-VR or PVA, an antifoaming agent - PENTA-465 or FOBR and water, dry cement mixture used is a mixture of Portland cement which facilitates inert filler - foamed microgranules glass fractions 0.1–1.5 mm or fine porous ceramic foam spherical granules of the same fraction, and fiber glass fiber size of 3–6 mm with diameter of 22–35 mcm at the following ratio of components, pts. wt.: Portland cement 100; which facilitates inert filler - foamed glass microgranules with particle size of 0.1–1.5 mm or fine porous ceramic foam spherical granules with same fraction 10–23; fibrous fiber 0.1–0.6; fluid loss reducer PVS-VR or PVA 0.5; antifoaming agent PENTA-465 "FOBR" 0.05; at that ratio of dry cement mixture to water is 100 pts. wt. to 50 pts. wt., respectively, then injected into a second portion of the cement slurry density 1585–1590 kg/m³ in volume as to fill the well annulus in range of 100 m from the face, wherein the second portion of the cement slurry contains a dry cement slurry, a setting accelerator - calcium chloride, and water, as a dry cement mixture, a mixture of Portland cement is used, which facilitates inert filler - foamed microgranules glass fractions 0.1–1.5 mm or fine porous ceramic foam spherical granules of the same fraction, and fiber glass with fiber size of 3–6 mm with diameter of 22–35 mcm, with the following ratio of components, pts. wt.: portland cement 100 which facilitates inert filler - foamed glass microgranules with particle size of 0.1–1.5 mm or fine porous ceramic foam spherical granules of same fraction 10–23; fibrous fiber 0.1–0.6; setting accelerator - calcium chloride 1–4; at that ratio of dry cement mixture to water is 100 pts. wt. to 50 pts. wt. respectively.

EFFECT: technical result is higher efficiency of the method of casing string cementing.

1 cl, 1 dwg, 5 tbl, 1 ex