CONTROL OF REVERSE FLOW PRESSURE IN PROCESS OF RAISING DRILL STRING ASSEMBLY BOTTOM

摘要

FIELD: mining.SUBSTANCE: drill string assembly bottom in process of the drilling operation on a casing string is raised by displacement of fluid medium in the casing string with the fluid medium of less density compared to the fluid medium in the annular space. The drill string assembly bottom moves upwards in the casing string under action of upward force specified by different density of fluid media in the casing string and in the annular space. The displaced fluid medium exits from the casing string via a throttling hole of the nozzle that limits the flow. The throughput section of the throttling hole varies in process of movement of the drill string assembly bottom upwards to control speed of upward movement of the drill string assembly bottom.EFFECT: increased efficiency of raising a drilling string assembly bottom.20 cl, 14 dwg