清水洼陷致密砂岩地震岩石物理特征及优势储层预测

Seismic Petrophysical Characteristics of Dense Sandstones in Qingshui Sag and Dominant Reservoir Prediction

针对常规叠后反演无法准确预测储层中流体的问题,采用叠前AVO流体预测方法,分析清水洼陷致密砂岩中的岩石物理特征及AVO响应特征,开展叠前流体因子反演研究。通过岩石物理实验测定致密砂岩的弹性模量及砂岩饱和不同性质流体时的纵横波速度关系,开展流体替代及叠前AVO分析。研究结果表明:清水洼陷致密砂岩在饱和油、气、水状态下,密度和泊松比变化明显,尤其是含气后密度和泊松比迅速减小,AVO反射振幅表现为随偏移距增大而快速衰减的特征。利用该特征及实测泥石基线约束叠前AVO流体因子反演,有效地提高了该区致密砂岩油气预测的准确性,为该区油气水关系的准确预测奠定基础。

In view of the issue that conventional post-stack inversion fails to accurately predict the fluid in the reservoir,a pre-stack AVO fluid prediction method was used to analyze the petrophysical characteristics and AVO response characteristics of the dense sandstone in Qingshui Depression and to carry out a study on pre-stack fluid factor inversion.Petrophysical experiment was conducted to determine the elastic modulus of dense sandstones and the relationship between p-wave velocity and s-wave velocity of sandstone when the sandstones were saturated with fluids of different properties.Fluid substitution and pre-stack AVO analysis were also carried out.The results of the study showed that the density and Poisson′s ratio of dense sandstone in Qingshui Sag changed significantly under the condition of saturated oil,gas and water,especially after containing gas,the density and Poisson′s ratio decreased rapidly,and the AVO reflection amplitude decreased rapidly with increasing offset.This feature and the measured mudstone baseline were used to constrain the inversion of pre-stack AVO fluid factor,effectively improves the accuracy of oil and gas prediction in the tight sandstone of the area,laying a foundation for the accurate prediction of the oil-gas-water relationship in this area.