METHOD FOR CEMENTING CASING STRINGS IN PRESENCE OF LOSS ZONES Russian patent published in 2023 - IPC E21B33/14 

FIELD: oil and gas industry.

SUBSTANCE: invention can be used for cementing casing strings, especially in wells with formations with low absorption gradients. The claimed method for cementing casing strings in presence of loss zones includes pumping buffer fluid, cement slurry and displacement fluid into the casing string, followed by forcing the cement slurry into the annulus to a predetermined height. At the same time, before the buffer fluid is pumped into the casing string, a calculated amount of a polymer sealing composition with a given transition time to the elastic state is pumped into it, which is placed in the gap and above the loss formation, and then pressed into the loss formation and kept inside the formation for the estimated time to complete the process of polymer cross-linking and gaining structural strength and elasticity. After that, the well is flushed and cemented with a low-density cement slurry.

EFFECT: improving quality of casing string cementing in presence of loss zones.

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