欠平衡井底压力采集系统的研制与应用

在欠平衡钻井、空气或泡沫钻井中,当钻井液含有多相流时会出现井底压力不清楚、地层压力预测误差较大、欠平衡井底负压值控制不准确等问题。通过在三开欠平衡井段的现场试验,实测出钻井过程中在井底存在多相流时的井底压力,发现理论计算误差在10%左右,在有气侵的情况下误差高达13%,为此,提出一种利用实测井底压力准确计算地层压力的新方法,完井实测地层压力证明了该理论计算的准确性。它能准确计算出井底负压值以及环空钻井液平均密度的大小,合理确定后续欠平衡钻井的钻井液密度,从而发展和完善了欠平衡钻井井底压力控制技术,实现了欠平衡钻井数据采集分析的定量化、标准化和自动化。

Development and Application of Under - Balanced Downhole Pressure Acquisition System

During under-balanced drilling, air drilling or foam drilling, such problems as uncertain downhole pressure, large errors on formation pressure prediction, improper control of the under-balanced downhole pressure may often occur when there are multi-phase flows in drilling fluid. Field test was conducted to accurately monitor the downhole pressure when there are multi-phase flows during under-balanced drilling in the third section, and the results proved that the conventional theoretical error is about 10%, sometimes as high as 13% when there is gas cut. A new method is presented to accurately calculate formation pressure by using the real monitored downhole pressure data, while the downhole under-balanced pressure and drilling fluid average density in the annular can be calculated also, thus a better determination of the mud weight in the following under-balanced drilling becomes possible.