精细控压钻井井底压力自动控制技术初探

控压钻井技术是当前油气钻井工程领域的前沿技术之一。钻井各个工况的井底压力须保持恒定，才能确保窄密度窗口复杂地层井段的安全、顺利钻进。为此，通过分析前人对各个工况井底压力计算的研究成果，提出了精细控压钻井井底压力计算模型，该模型的环空循环压耗计算包含了多相流动的重力压降、摩阻压降和加速度压降梯度。在塔里木盆地实施了1口井的精细控压钻井作业，用停泵工况由地面回压泵施加的回压值与计算值比较，最大误差为0.30 MPa，能满足工程实际需要，为今后精细控压钻井井底压力精确计算与控制提供了理论支撑。

Automatic control of bottomhole pressure during precisely managed pressure drilling

Managed pressure drilling(MPD) is one of the front-edge drilling technologies in oil and gas drilling engineering.The bottomhole pressure must be kept constant under various working conditions to ensure safe drilling especially at the well sections with narrow safety drilling density of drilling fluids through complicated formations.Based on the analysis of the previous study results of bottomhole pressure calculation for different drilling conditions,the bottomhole pressure calculation model is built for precisely managed pressure drilling.The annulus circulation pressure loss calculation in that model includes the gravitational pressure loss of multi-phase flow,frictional pressure loss and acceleration pressure loss.That model has been applied in the precisely managed pressure drilling in a well in the Tarim Basin.Through the comparison made between the calculated pressure value and the backpressure exerted by the surface backpressure pump during the pumping-off,the maximum error is 0.30 MPa,which meets engineering requirements.It will provide theoretical support for precise calculation and control of the BHP during MPD in future.