高压气井CX488井天然气欠平衡压力钻井技术

新场构造沙溪庙组地层压力梯度高达0．015～O．018MPa／m，采用微超平衡压力钻井，在高密度钻井液条件下钻进，不但机械钻速低，还不利于发现和保护油气层。为此，在制定了详尽的完井方案、带压起下钻技术措施、岩屑分离方案和相关的应急措施后，CX488井在钻进沙溪庙组产层段时试验应用了天然气欠平衡压力钻井技术。试验结果表明，在高压地层采用天然气钻井技术可以大幅提高钻井速度，该井平均机械钻速达11．46m／h，与邻井相比机械钻速提高1倍以上。该技术在高压气井CX488井的成功应用为在高压地层应用气体钻井技术积累了经验。

Natural Gas Underbalanced Drilling Technique in a High Pressure Gas Well CX488

The formation pressure gradient of Shaximiao formation in Xinchang gas field is up to 0. 015 -0. 018 MPa/m. The rate of penetration is low and it is very difficult to identify and protect reservoir in high density drilling fluid using near balanced drilling technique. The experiment results indicate that rate of penetration can be increased significantly using natural gas drilling technology. The average rate of penetration reaches 11.46 m/h, increased for about 100% compared to the rate of penetration of neighboring well. The successful application of this technique in high pressure gas well CX488 accumulates the experiences for drilling using gas in high pressure formation.