Eaton法计算地层压力中趋势线的半定量确定方法

A Semi-quantitative Method to Determine the Trend Line in Formation Pressure Calculation by the Eaton Method

渤海油田钻井施工过程中井漏、井塌等现象时有发生,井壁失稳现象严重,而地层压力预测准确与否直接关系到井壁的稳定性。Eaton法是计算地层压力适用范围较广的方法,其中关键参数正常压实趋势线的确定仍停留在定性阶段,人为性较强,因此需要寻找出一种定量确定趋势线的方法。利用声波时差与深度的关系,根据声波时差曲线趋势先定性划分趋势线,再将常规测井资料与地质录井资料相结合,在前期定性划分的每段趋势线内人工选取关键泥岩点,定量确定趋势线,从而减少了常规法确定趋势线的诸多人为因素。此方法在渤海油田大部分地区得到应用。应用结果表明:与实测数据对比,预测的地层压力数值与原方法对比,精度明显提高,并为后续破裂压力及坍塌压力的计算奠定了基础,可作为Eaton法计算地层压力的补充。

In the process of drilling in Bohai oilfield,the phenomenon of well loss and well collapse often occurs,and the phenomenon of wellbore instability is serious,and the accuracy of formation pressure prediction directly affects the stability of wellbore.The Eaton method is a widely applicable method to calculate formation pressure,among which the determination of the normal compaction trend line of the key parameter is still in the qualitative stage at present,and the human nature is strong,so finding a quantitative method to determine the trend line is always the goal of research.Based on the relationship between acoustic time difference and depth,the trend line is divided qualitatively according to the trend of acoustic time difference curve,and then the conventional logging data and geological logging data are combined to manually select the key mudstone points in each section of trend line in the early qualitative division,and the trend line is determined quantitatively,so as to reduce many human factors in the conventional method to determine the trend line.This method has been widely used in most areas of Bohai oilfield.The application results show that compared with the measured data,the predicted formation pressure is more accurate than the original method,and lays a foundation for the subsequent calculation of fracture pressure and collapse pressure.This method can be used as a supplement to the calculation of formation pressure by Eaton method.