渤海湾盆地东营凹陷砂岩储层地震特征及对岩石结构的指示

系统选取渤海湾盆地东营凹陷古近系各层段砂岩样品250块(以沙河街组为主),并在模拟储层条件下利用脉冲穿透法测试样品的纵、横波速度,在此基础上给出储层条件下速度-孔隙度、速度-密度等的统计岩石物理模型。样品在纵波速度-泊松比交汇图中呈现出两种主要变化趋势,分别对应泥质与钙质胶结物的影响。在每个变化趋势中,随泥质含量与钙质胶结物含量的增加,岩石结构从颗粒支撑逐渐表现为基质支撑,弹性波能量的传播也从通过颗粒接触边界转变为通过岩石基质传播。这是使砂岩样品测试结果表现出两种截然不同变化趋势的主要原因,为利用岩石物理特性从地震资料中提取岩石结构、沉积与成岩特征的信息提供了依据。

Seismic properties of reservoir sandstones and their implication to rock texture in the Dongying Sag,the Bohai Bay Basin

A total of 250 sandstone samples were selected from various sections of the Paleogene(dominated by the Shahejie Formation) in the Dongying Sag of the Bohai Bay Basin to measure their compressional-and shear-wave velocities by pulse transmission techniques under simulated reservoir conditions.Statistic petrophysical models under reservoir conditions,such as velocity versus porosity and velocity versus density,were built based on the measured data.On the cross plot of P-wave velocity vs.Possion's ratio,the samples show two major trends,which reflect the effects of shale content and calcareous cement content on the elastic properties of sandstone samples respectively.For each trend,the rock texture changes gradually from grain-supporting to matrix-supporting with the increase of shale content and calcareous cement content,and thus the propagation of elastic wave also changes from via grain-to-grain contacts to via rock matrix.These are the main reasons for the two entirely different trends of the sandstone samples.The results provide a basis for extracting information about rock texture,sedimentary and diagenetic features by using the petrophysical properties of reservoir sandstones.