基于机械钻速的地层孔隙压力随钻监测方法

Monitoring method for formation pore pressure while drilling based on rate of penetration

杨前亮 黄洪林 罗鸣 吴艳辉 李文拓 肖平

YANG Qianliang HUANG Honglin LUO Ming WU Yanhui LI Wentuo XIAO Ping

中海石油(中国)有限公司海南分公司 海南省深海深层能源工程重点实验室

CNOOC (China) Co., Ltd. Hainan Branch, Haikou 510700, Hainan, China Key Laboratory of Deep-Sea Deep-Formation Energy Engineering of Hainan Province, Haikou 570100, Hainan, China

精确监测地层孔隙压力是及时调整钻进参数、确保安全钻进的重要基础，但目前国内地层孔隙压力随钻监测难度大，精度不足。考虑钻进过程中钻井液渗流引起的近井底地层孔隙压力重分布问题，分析井底压差、钻头单齿吃入井底岩石深度和钻头机械钻速三者间对应关系，推导并建立了地层孔隙压力随钻监测模型(机械钻速法)，并将机械钻速法的监测结果与d_c指数法和岩石强度法的计算结果进行对比分析。研究结果表明，井底压差与钻井液渗透强度和机械钻速呈正相关关系，与钻头单齿吃入井底岩石深度呈负相关关系；机械钻速法的单点监测精度均高于95%，平均误差只有1.63%，适用性更强。研究成果为钻进参数(尤其是窄密度窗口层段)及时调整提供理论支撑，为安全、高效钻井提供保障。

Accurate monitoring of formation pore pressure is a crucial foundation to adjust drilling parameters promptly and ensure safe drilling operations. Currently, domestic formation pore pressure monitoring while drilling is difficult and less accurate. In response, the near-wellbore formation pore pressure redistribution caused by drilling fluid flow during the drilling process was taken into consideration. The correlations among bottom-hole pressure difference, depth of drill bit penetration into the bottom rock and penetration rate were analyzed, and a model (penetration rate method) for monitoring formation pore pressure while drilling was derived and established. Finally, the monitoring results from the penetration rate method were analyzed and compared with the computation results obtained using index method and rock strength method. The research results show that there exists a positive correlation between bottom-hole pressure difference and drilling fluid permeation intensity as well as penetration rate, while a negative correlation with the penetration depth of single tooth of the drill bit into the bottom rock. The single-point monitoring accuracy of the penetration rate method is consistently above 95%, with an average error as low as 1.63%, demonstrating its greater applicability. The research results can provide a theoretical support for the timely adjustment of drilling parameters, especially in narrow-density window intervals, ensuring the safety and efficiency of drilling operations.

10.13639/j.odpt.202304033