膨胀性流体超压预测方法及其应用

Prediction of Overpressures Generated by Fluid Expansion: Methods and Application

在分析不同成因增压机理对岩石物理特征影响的基础上,探讨了膨胀性流体超压的预测方法。研究结果指出,Eaton法适用于流体膨胀成因超压的预测,并以济阳坳陷沾化凹陷渤南洼陷为例,采用Eaton法对其多成因超压的地层压力进行了预测。初步确定伊顿指数为1~4,然后引入预测压力相对误差平方和参数,利用迭代法,通过对比不同伊顿指数所对应的相对误差平方和来拟合伊顿指数。当伊顿指数取2.6时,渤南洼陷预测压力的相对误差平方和最小,预测效果最好。

Accurate pore-pressure prediction in overpressured regions is essential to ensure safe drilling operations,also provides essentialdata for reservoir planning and reserves estimation. Based on the differences of petrophysical signatures between different overpressuremechanisms,the prediction method for overpressure generated by fluid expansion mechanisms was syudied. The results showed that the Ea-ton method is suitable for estimating overpressure generated by different mechanisms. Taking Bonan sag of Zhanhua depression in the Ji-yang subbasin as an example,the procedure of determining the exponent c and predicting fluid pressure by Eaton method were explained.At first,it is initially identified that the exponent c was between 1 to 4. Then,introducing a parameter the sum of the squares of relative er-ror and using the iterative method,the exponent c could be determined by comparing the different sum of the squares of relative error. Theresults showed that the sum of the squares of relative error was the smallest when the Eaton exponent is 2.6,and the prediction was most ac-curate.