钻井液密度窗口随钻预测理论及其工程应用

将岩石力学方法与地震勘探理论相结合,通过考察地震记录、岩石物理参数与孔隙压力之间的定量关系,建立了利用地震数据直接反演孔隙压力的模型。根据岩石力学参数地质统计特性,实钻过程中充分利用录井、钻井等实时信息,通过随机反演方法随钻预测钻头前方待钻地层的孔隙压力。依据孔隙压力反演结果进一步求取地应力、岩石强度、坍塌压力与破裂压力,通过对预测参数的综合分析,最终实现对待钻井段的安全钻井液密度窗口进行随钻预测。该方法在川东北HB探区的2口深探井进行了工程应用,现场应用情况表明该方法预测精度较高、实时操作简捷、计算过程稳定,具备良好的随钻适用性。

A theory on predicting drilling fluid density windows while drilling and its engineering application

Based on rock mechanics methods in combination with seismic exploration theories, a model that uses seismic data to directly retrieve pore pressure is established through investigating the quantitative relationship between seismic records, rock physical parameters and pore pressure. According to the geological statistical characteristics of rock mechanical parameters, as well as logging, drilling and other real-time information in the actual drilling process, this study predicts pore pressure of the strata to be drilled using a stochastic inversion method. Based on the inversion results of pore pressure, in-situ stress, rock strength, collapse pressure and fracture pressure are further solved. Through comprehensive analysis of the predicted parameters, the safe drilling fluid density windows of target strata are finally predicted while drilling. This method has been used for engineering application in the HB exploration area of northeast Sichuan. Field application results show that this method has high predicting precision, simple real-time operation, stable calculation process and good application in drilling.