AVO流体反演理论与实践

AVO fluid inversion: theory and practice

AVO流体反演技术能够定量地确定储集层含各种流体的可能性。首先利用测井曲线建立Monte-Carlo随机正演模型,然后通过Biot-Gassman流体替换理论获得模型中流体分别为油、气、水时的合成记录,利用Shuey公式得到相应的截距和梯度,将实际地震数据所得到的截距和梯度与模型所产生的截距和梯度进行对比,再利用Bayes理论即可定量求得所含油、气、水的可能性。当储集层中含有油、气、水中的二相或三相时,可能性分布图重叠,预测的可能性值比只含单相流体时有所降低,但是预测的准确性仍然比较高。将这项技术应用于川中天然气勘探,取得了较好的应用效果。

AVO fluid inversion can quantitatively determine the probability distribution of fluids in a reservoir. Procedures are as follows： establish a Monte-Carlo simulation model from logging curves, get the synthetic data using Biot-Gassman theory as the fluids are oil, gas, and water in the model, get intercept and gradient using Shuey＇s function, compare the intercept and gradient values from the seismic data with the model values, and finally determine the probability of each fluid using Bayesian theory. Compared to the one phase fluid, when the fluid is composed of two or three phases, the predicted value is low owing to the overlapping of the probability distribution graph, but its precision is still high. The technology was successfully applied in the middle Sichuan Province.