琼东南盆地深水区探井随钻压力监测技术与应用

Research and application of while-drilling pressure-monitoring technology in exploration wells of deep water area,Qiongdongnan Basin

南海西部琼东南盆地深水区蕴藏着丰富的天然气资源,但钻进中面临着高温超压、水深、钻井液密度窗口窄等高风险难题,为降低探井施工作业风险,开展了随钻监测压力技术试验。在钻井过程中,以先进的随钻测量技术、数据传输技术作为支撑.将随钻测量的地球物理信息转换为井下地层3个压力数据,用于及时修正钻前压力预测模型,评估井眼稳定状况,调整钻井液密度;完井后,使用地层漏失试验、测压取样等资料再对地层压力进行计算,以便更新、完善钻前模型,为后续工作做好准备。该技术在深水区探井的实际应用表明,地层压力监测精度超过95%,同时,应用已完钻井的地层压力成果及实际钻井作业中实时监测获取的地层压力剖面,优化了后续滚动探井的井身构造,成功地减少了一层套管,极大地节约了钻井成本。目前该技术已在该盆地深水探井作业中被广泛采用.并取得了良好的经济效益。

The deep water area in the Qiongdongnan Basin of South China Sea is rich in natural gas resources. However, high risks often exit in drilling, like high temperature, overpressure, deep water and narrow drilling fluid density window. To reduce the risks during operations of exploration wells, technical test is carried out of while-drilling pressure monitoring. In the course of drilling, the advanced MWD technique and data transmission technique are adopted to transform the geophysical data obtained from MWD into three types of pressure data of downhole formations, so as to modify in time the pre drilling pressure prediction model, evaluate the wellbore stability and adjust the drilling fluid density. After completion, the data of formation leakage test and pressure test sampling to recalculate the formation pressure, so as to update and perfect the pre-drilling model and get ready for subsequent jobs. The prac- tical application of this technique in the exploration wells of the deep water area shows that the formation pressure monitoring accura cy exceeds 95%. Moreover, the formation pressure results of drilled wells and the formation pressure profiles obtained from real- time monitoring in actual drilling are used to optimize the casing programs of subsequent progressive exploration wells, which have successfully reduced one layer of casing and largely cut down the drilling cost. This technique has been widely used in the deep water exploration wells of this basin with good economic benefits achieved.