METHOD FOR MAINTAINING BIT LOAD ON FLOATING DRILLING UNITS AND DEVICE FOR ITS REALIZATION Russian patent published in 1994 - IPC

FIELD: floating drilling units. SUBSTANCE: to maintain bit load, active system for load compensation is installed between drill string and travelling block after output member of passive compensation system of heaving motions and absolute value of operation error of heaving passive compensator is computed. In this case, 80-90% of total bit load is ensured by short stroke pneumohydraulic cylinders with passive control system and 10-20% by short stroke hydraulic cylinders with active control system receiving signals from position transducer or drill string load. Method is realized in the compensator of vertical motions of drilling string. Installed on output member of compensation passive system is active compensation system comprising four chamber hydraulic cylinder of hydraulic supply source, pneumohydroaccumulator and automatic control system. Hydraulic cylinder body is rigidly connected with output member of compensation passive system, its rod is connected through intermediate member with drill string. First working chamber of hydraulic cylinder is connected with atmosphere, second with pneumohydroaccumulator, third and fourth chambers are connected with main lines of hydraulic supply source interacting with automatic control system. EFFECT: higher efficiency. 2 cl, 1 dwg