HYDRODYNAMIC METHOD FOR CHECKING RELIABILITY OF ISOLATION OF LOSS ZONES, CARRIED OUT BEFORE CEMENTING CASING STRINGS Russian patent published in 2024 - IPC E21B47/06 E21B33/138 

FIELD: oil and gas industry.

SUBSTANCE: hydrodynamic method has been claimed for testing reliability of isolation of absorption zones, carried out before cementing the casing. The free end of the drill string is lowered to the bottom of the well, connected to a container with testing fluid, the annular space is sealed with a preventer, the testing fluid is pumped into the drill string, and using a throttle valve on the block, excess pressure is stepwise created in the annular space of the well to the design testing pressure. Excessive pressure is formed in the process of flushing with pressure testing fluid with a supply that ensures its speed of movement equal to the expected speed of movement of the cement and drilling fluids in the annular space of the well during cementing. At each value of excess pressure, presence or absence of loss is recorded by comparing the amount of pressure testing fluid injected and leaving the well. The final testing pressure is determined by the formula: If, during pressure testing, the open wellbore can withstand the design pressure, it is recognized as tight and ready for cementing job.

EFFECT: improvement of efficiency and quality of well completion by preventing complications during their cementing, namely loss of cement slurry, which eliminates corrective cementing and the associated costs of time and materials.

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