BOTTOMHOLE PRESSURE PREDICTION AND CONTROL TECHNOLOGY IN UNDERBALANCED DRILLING

This paper presented the necessity of maintaining 100% underbalanced conditions during underbalanced drilling operation.The factors affected bottomhole pressure fluctuation were analyzed.The new development of bottomhole pressure control and prediction technology in underbalanced drilling was introduced.The deficiency in the study and limitation in use was presented.The innovation method of solving bottomhole pressure fluctuation was given:the dynamic model by coupling wellbore and formation flow characteristic was established to predict wellbore pressure current time.During tripping and drilling connections,the reservoir influx substituted for the interrupted surface injection to control bottomhole pressure fluctuation.These conditions should allow preservation of underbalanced conditions and consequently avoid formation damage.To predict bottomhole pressure effectively,the combination of dynamic and steady state models should be studied.