基于Gassmann方程岩石速度倒转现象成因分析

Gassmann理论主要用于处理流体替换问题,在进行流体替换研究中发现总会在一定情况下出现"倒转现象"。解释为在一定的孔隙度情况下,100%含气岩石速度大于100%含水岩石速度,这同岩石物理实验室测试结果相违背。因此针对不同的岩样数据及测井资料,图示分析了完全饱和岩石速度倒转成因,发现替换后饱和岩石密度差异过大会造成此现象。同时在对碳酸盐岩储层岩石进行了饱和度替换数值模拟后发现,模拟结果同实验室测试数据趋势一致,只是碳酸盐岩对孔隙度大小分类不同。因此强调了流体替换正演模拟的重要性,在一定物理意义下的替换才有实际价值。

ROCK VELOCITY REVERSE CAUSE ANALYSIS BASED ON GASSMANN EQUATION

Gassmann effective medium theory is the most classic and most basic rock physics model.On this basis,the other equivalent model established greatly enriched media saturated rock elastic wave propagation theory.Gassmann theory is mainly used for dealing with the issue of fluid substitution,but fluid substitution always appear "reverse phenomena" under certain conditions.Interpreted as the porosity under a certain,fully gas-saturated rock velocity more than water-saturated,which is contrary to the result of physics rock laboratory test.Therefore,graphic analysis the cause of saturated rock speed reverse for different rock sample and well log data,found that the density difference of saturated rock is too large causes leading to reverse.AT the same time,the saturation of carbonate reservoir rocks were replaced by numerical simulation,the simulation results was consistent with the laboratory test data,only carbonate rocks of different porosity size.Therefore emphasizes on the importance of fluid substitution forward modeling,the actual value of fluid substitutions only under certain physical meaning.