古城地区鹰山组碳酸盐岩储层地震岩石物理特征

Seismic petrophysical characteristics of the carbonate reservoirs in Yingshan Formation of Gucheng area

塔里木盆地古城地区鹰山组碳酸盐岩在成岩和后成岩过程中形成了较为复杂的孔隙结构,致使其纵、横波速度等地震弹性参数不仅受孔隙度变化影响,还依赖于孔隙结构变化。通过对致密碳酸盐岩样品系统岩石物理测试,并对铸体薄片提取反映样品孔隙结构的特征比表面、平均孔喉半径等参数,定量研究了孔隙结构对岩石地震弹性性质的影响。结果表明,样品渗透率—孔隙度关系以及纵波速度—孔隙度关系受孔隙结构控制,碳酸盐岩样品纵、横波速度等地震弹性参数与反映孔隙结构特征的特征比表面、平均孔喉半径以及平均纵横比存在明显的相关性,表现为高速度样品具有低特征比表面、高平均孔喉半径特征。另外引入骨架柔韧性因子γ进行碳酸盐岩样品孔隙结构的表征,在相同孔隙度条件下,低骨架柔韧性因子的样品溶孔发育,储集层具有高速低渗的特征;高骨架柔韧性因子的样品微裂隙发育,储集层具有低速高渗的特征。研究成果可为相关储层的岩性及烃类地震检测提供依据。

Relatively complicated pore structures were formed in the diagenetic and post-diagenetic process for the carbonate rocks in Yingshan Formation of Gucheng area in Tarim Basin,which make their seismic elastic properties such as the vertical,horizontal velocity and so on not only influenced by the changes of the porosity,but also by the variance of the pore structure.Through the systematical test of the petrophysics of the tight carbonate rock samples,the parameters of the cast thin section such as the characteristic specific surface,average pore-throat radius and so forth were extracted to response the pore structure characteristics of the samples.The results show that the relationships between the sample permeability and porosity and moreover between the vertical velocity and porosity are both controlled by the pore structures,there are obvious correlation between the seismic elastic parameters i.e.the vertical,horizontal velocity and so on and the pore structure responding parameters including the characteristic specific surface,average pore-throat radius and average vertical-horizontal ratio so forth,the lower characteristic specific surface and higher average pore-throat radius are shown for the high-velocity samples.In addition,by means of introducing the frame flexibility factor(γ),the pore structures of the carbonate samples were characterized,under the condition of the same porosity,the dissolved pores with lower frame flexibility factor are well developed,the reservoirs are characterized by higher velocity and lower permeability;while for the samples with higher frame flexibility factor,the micro-fractures are well developed,the reservoirs are characterized by lower velocity and higher permeability.The study can provide evidences for the lithological and hydrocarbon seismic tests of the relative reservoirs.