Development and Testing of a Fully Automated System to Accurately Control Downhole Pressure During Drilling Operations.

摘要

Accurate control over bottomhole pressure during drilling isessential as the industry meets increasingly challengingdrilling environments such narrow drilling margin formations,HPHT wells and fractured formations.To increase the accuracy of the control over bottom holepressures during drilling, a fully automated prototype systemconsisting of a hydraulics simulator, a computer controlledchoke manifold and a pump as part of the mud return systemhas been developed and tested.Rather than mud density alone, the system uses a reduceddensity mud in combination with a variable back-pressure atthe annulus exit to achieve the required downhole pressure.The system is able to substantially compensate downholepressure variations induced by the drilling operation byvarying the surface back-pressure.A number of possible advantages are associated with the useof the system:1.Reduction of formation impairment2.Reduction of mud losses3.Reduction of formation fluid influx4.Increased ROP5.No flat time during weight-up/down6.Potential to reduce number of casing strings7.Automatic kick circulationA successful experimental program has been conducted on areal size test well in preparation of a field test sequence.The system was easily retrofitted to the existing test rig andnormal drilling procedures were minimally impacted.