基于贝叶斯理论的含可信度孔隙压力随钻修正方法

Bayes theory based credibility containing pore pressure correction method while drilling

地层压力预测与监测一直是油气钻井的一项重要任务,准确预测地层压力是保证钻井从设计到施工顺利安全进行的重要前提。地层压力钻前预测法是通过地震资料来预测地层压力,但是预测结果精度不高,孔隙压力预测结果与井底实际压力之间存在较大误差。为了根据随钻测量数据动态更新孔隙压力预测结果,不断降低其不确定度,提出了基于Bayes理论的含可信度孔隙压力随钻修正方法。孔隙压力后验概率信息综合了钻前孔隙压力预测信息以及随钻孔隙压力观测信息,在钻前预测的基础上利用随钻资料进行修正与更新,最大限度地保证了钻进过程中钻头位置局部孔隙压力预测准确度。该研究可以为钻井作业过程中动态风险评估提供实时且更为准确的孔隙压力,辅助钻井作业人员快速、准确地进行施工方案的决策,减少由于压力信息不准确带来的钻井风险。

Formation pressure prediction and monitoring has always been one important task of oil and gas well drilling,and accurate formation pressure prediction is the important prerequisite to ensure the smooth and safe process from design to construction.Pre-drilling formation pressure prediction method is to predict the formation pressure by using the seismic data,but its prediction accuracy is low and there is a larger error between the predicted pore pressure and the actual bottom hole pressure.In order to update the prediction results of pore pressure dynamically according to the measurement data while drilling and reduce its uncertainty further,this paper put forward the Bayes theory based credibility containing pore pressure correction method while drilling.Posterior probability information of pore pressure includes the pre-drilling pore pressure prediction information and the pore pressure monitoring information while drilling.Based on pre-drilling prediction,combined with while drilling data,pore pressure is corrected and upgraded to ensure the prediction accuracy of local pore pressure at the position of drilling bit in the process of drilling as high as possible.The research results provide the real-time accurate pore pressure for the dynamic risk evaluation in the process of drilling operation, assist drilling operators to make decision on the construction scheme fast and accurately and reduce the drilling risks causedby inaccurate pressure information.