基于随钻测井资料的地层孔隙压力预测方法研究

以往针对直井的地层孔隙压力的计算方法在大位移井、水平井和分支井中由于井斜和井水平的特殊性及复杂性会产生较大误差.等效深度法等传统方法大多是针对砂泥岩地层建立的模型,对碳酸盐岩地层不大适用.利用随钻测量(MWD)资料和随钻测井(LWD)资料,研究把斜深校正成垂深,计算出与垂深相对应的测井值及上覆地层压力,综合考虑地层岩性、孔隙度、孔隙流体类型等因素的影响,采用层速度-有效应力法建立适用于斜井段和水平井段的地层孔隙压力计算模型,实现基于随钻测井资料的地层孔隙压力预测,避免了传统方法因建立泥岩正常压实趋势线所带来的误差.将该方法应用于实际随钻地层孔隙压力预测中,处理结果与实测结果符合率高,可靠性好.随钻测井资料预测孔隙压力具有实时性,对于提高钻速、防止井喷井漏等恶性事故有非常重要的现实意义.

Research on the Predication Method of Formation Pore Pressure Based on LWD Data

The conventional methods of computating formation pressure pore for the straight well are no longer used for extended reach well, horizontal well and branch well, and often generate great errors owing to the particularity and complicacy of inclined well and horizontal well. The conventional log methods such as equivalent depth calculating method and others are mainly used for sandshale formations, so they are not very feasible to carbonate formation. Based on the pre-decessor's studies, true drilling depth obtained from the MDD & LWD data is corrected to be to-tal vertical depth; the log value corresponding to the vertical depth and overlying formation pres-sure have been figured out. On the basis of considering the influence of formation lithology, po-rosity and pore fluid types, the interval velocity & effective stress algorithm is used to set up the formation pore pressure calculation model, which is fit for horizontal well and incline well, there-fore, successfully predicting the pore pressure while drilling with real-time MWD and LWD log data, and also avoiding errors caused by the conventional log methods establishing normal mud-stone compaction trend line. This algorithm is reliable, and has been used in actual prediction of formation pore pressure which drilling, the log result of which is in good agreement with the da-ta-processed one. Predicting the pore pressure with MWD data is real-time, so it is significant in increasing drilling speed, avoiding well blowout and mud loss, etc.