控压欠平衡钻井工艺实现方法与现场试验

控压钻井是国外新近发展起来的一项新的钻井技术，为解决复杂地层安全钻进问题提供了一个新方案，国内对其研究才刚刚起步，尚无可资借鉴的经验。为此，系统分析了欠平衡钻井技术与控压钻井技术的异同，比较分析了控压过平衡、近平衡与欠平衡钻井的工艺特征，提出了一套控压欠平衡钻井关键工艺的实现方法，包括：循环钻进、起下钻和接单根等不同工况的控压钻井程序，并在川中蓬莱9井进行了控压钻井欠平衡现场试验。结果表明：该项控压欠平衡钻井工艺技术能实现循环钻进、起下钻、接单根等工况的压力平稳衔接，钻进过程中压力误差值在0.2 MPa左右，起下钻、接单根过程压力误差在0.5 MPa左右，并且能实现“有控制”的边喷边钻。采用控压欠平衡钻井技术在保障井下安全、提高机械钻速的同时，还达到了有效发现储层的目的。

A case study of underbalanced and managed pressure drilling process

Managed pressure drilling is recently developed as a new technology at abroad,which provides a new solution to safe drilling especially in complicated formations.However,such studies have just started in China so we can not find good experience to learn from.In view of this,this paper makes a systematic analysis of the differences between underbalanced drilling(UBD) and managed pressure drilling(MPD),and compares the features of managed over-balanced process,managed near-balanced process,and UBD process.On the basis of this,a set of methods are proposed to realize the underbalanced and managed pressure drilling process,including the MPD procedures adopted under different conditions such as circulation,tripping and pipe connection.Through a case study of the well Penglai-9 in the central Sichuan Basin,the developed UBD and MPD drilling process not only achieved the controlled flow drilling,but realized a smooth pressure convergence during circulation,tripping,and pipe connection with the pressure error of about 0.2 MPa during drilling and about 0.5 MPa during tripping and pipe connection.To summarize,this drilling process can ensure downhole safety and ROP improvement,meanwhile realize effective discovery of pay zones.