Continuous Circulation During Drilling Utilizing a Drillstring Integrated Valve-The Continuous Circulation Valve

摘要

A Continuous Circulation Valve, CCV, was developed forenabling drilling in depleted reservoirs in the Norwegian sectorof the North Sea. By utilizing a system to obtain circulationthroughout the whole drilling operation, the down holepressure will remain constant even during drill pipeconnections. By balancing this down hole pressure between amaximum pore pressure and a minimum fracture pressure,drilling can be performed properly even through narrowdrilling windows.The valve is a two position three way ball valve. It ispossible to circulate through the valve from the top drive downthe drill string or through a side port and down the drill string.Such a valve must be installed at the top of each drill pipestand before the continuous circulation operation starts. Whena connection is to be performed, a hose must be connected tothe side inlet of the valve, the flow from the mud pumps willthen be switched from the top inlet to the side inlet and topdrive can then be disconnected and a new stand installed. Tocontinue drilling, the operation is reversed. The valve isdesigned to withstand HPHT pressures including gas filledcasings, bull heading and maximum pressure during standarddrilling operation.A prototype of the valve has been produced and operationtested on the full scale research drilling rig "Ullrigg" inStavanger, Norway. The current paper presents in detail theadvantages gained by using the CCV in a drilling operation.The paper gives a thorough description of the valve and itsperformance. The "Ullrigg" test of the prototype is describedin detail.