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

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 d_(c) 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.