充氮气钻井技术在长宁区块页岩气井的应用

Application of Nitrogen Injection Drilling Technology for Shale Gas Wells in Changning Block

长宁区块Φ311.2 mm井眼段井漏问题突出,已经成为制约页岩气勘探开发进度的难题之一。基于页岩气井中上部地层工程地质特征,分析了长宁区块Φ311.2 mm井眼段钻井技术难点及相应井段漏层特征和井漏机理,提出了采用充氮气连续循环钻井进行治漏的技术思路。从侧向阀优化设计、连续循环钻井工艺、EM-MWD测斜工具减振三方面完善了充氮气连续循环钻井工艺;以同平台2口已钻井的实测漏层压力系数为目标循环当量密度,通过软件模拟开展了氮气注入参数设计,形成了长宁区块Φ311.2 mm井眼段充气钻井的技术方案并在N216H14-5井开展了现场试验。试验情况表明:实施充氮气钻井后有效减少了漏失量,提高了钻井时效,缩短了井漏复杂处理周期,实现了预期的治漏目标,并初步形成了上部快速钻井+中段防塌+下部井漏治理的防漏治漏钻井模式该模式具备进一步现场推广应用的潜力。

The leakage problem in the 311.2 mm hole section in Changning block is prominent,which has become one of the major technical bottleneck restricting the progress of shale gas exploration and development.Based on the engineering geological characteristics of shale,this paper analyzes the drilling technical difficulties and the characteristics of the leakage zone in the 311.2 mm well section in Changning block.The technical idea of using nitrogen injection continuous circulation drilling to control the leakage was put forward.The nitrogen injection continuous circulation drilling technology was improved from such three aspects as lateral valve optimization design,continuous circulation technique and EM-MWD damping.Taking the measured pressure coefficient of leaky formation from two Wells drilled on the same platform as the target circulation equivalent density,nitrogen injection parameters were designed by software simulation,forming a technical scheme of aerated drilling in Φ311.2 mm section of Changning block,and field tests were carried out in Well Ning 216 H14-5.The test results show that after the implementation of nitrogen injection drilling the loss is reduced,drilling efficiency is improved,the complex treatment time of well loss is shortened,and the expected goal of loss control is achieved,and the leak prevention and leak control drilling mode with fast drilling in the upper section,collapse prevention in the middle section and lost circulation control in the lower section has been formed.This mode has the potential of further field promotion and application.