孔隙度与含气饱和度变化正演模型特征分析

Characteristic Analysis Based on Forward Simulation Model with Porosity and Gas Saturation Changes

由于四川盆地某工区珍珠冲段致密砂岩储层因低孔隙性和含气饱和度变化所产生的地球物理特征变化相对较弱,故而难以确定其有利的储集空间。在分析工区岩石地球物理特征的基础上建立含气储层的地震地质模型,然后对模型进行波动方程有限差分数值模拟及叠前深度偏移处理,最后对其进行波场特征和地震属性分析,分析地震振幅属性与孔隙度及含气饱和度的定性关系。研究结果认为,当孔隙度达到含气要求时,含气特征分类与孔隙度大小关系不大,而主要与含气饱和度有关。N值随含气饱和度增大而增加,且有分段变化趋势,根据各段变化趋势可以将储层分为5种类型。该正演模拟的分析结果表明,可以通过对地震资料进行地震属性分析定性地确定工区含气特征,这对于地震勘探实践具有重要的指导意义。

The geophysical characteristic changes caused by low porosity and gas saturation changes were relatively weak,which was caused in tight sandstone reservoirs of Zhenzhuchong Formation of Sichuan Basin,thus it was difficult to determine the better reservoir space.A gas reservoir geological model was established based on the analysis of rock geophysical characteristics of the work area,and then forward simulation and pre-stack depth migration processing were conducted on the model,its wave field characteristics and seismic attribute were analyzed,the relationship between the seismic amplitude attribute and porosity and gas saturation was qualitatively studied.The result indicates that when porosity meets the requirements of containing gas,its gas feature and classification have little relationship with porosity,but mainly with gas saturation.The characteristics of gas features increase with the increase of gas saturation and it has the trend of zoning changes,the reservoirs can be divided into five different types according to its zoning changing trend.The forward simulation results show that the seismic attribute analysis can be used to qualitatively determine the characteristics of gas in the work area,it provides a guidance for seismic exploration.