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近些年来的勘探实践表明,四川盆地须家河组存在“厚砂薄储”的问题,优质储层的形成主控因素复杂。前人研究认为优质储层主要受沉积相、岩石相和成岩相控制,然而,对其他因素考虑较少。通过系统的岩心、露头、岩石薄片等资料研究认为,生物扰动构造对储层物性的影响也较大,生物扰动强度与储层物性成正比。研究认为,四川盆地上三叠统可以划分出4种岩性—生物扰动组合:①厚泥层扰动,主要形成于厚层黑色泥岩中,反映滨湖沼泽或浅湖沉积环境;②砂泥边界扰动,发育于厚层深灰色泥岩夹薄层浅灰色粉—细砂岩中,扰动指数为2～3,反映远端砂坝下部环境;③砂泥薄互层扰动,主要发育在砂泥薄互层中,砂层单层厚度为2～8cm,纵向上砂泥薄互层,扰动指数为4～5,反映三角洲前缘远端砂坝上部环境;④厚砂层扰动,主要发育于厚层砂岩中,扰动指数为1～2,表明其形成于水体能量相对较强的水下分支河道环境。生物扰动构造与储层物性呈正相关,即生物扰动越强,储层物性越好;而弱扰动或未扰动部位原生孔隙胶结致密,孔渗性都非常差。这主要是因为生物扰动可以提高岩石的均质性和岩石颗粒的分选性。
The exploration practice in recent years shows that the Xujiahe Formation in the Sichuan Basin has the problem of “thick sand and thin reservoirs,” and the formation of high-quality reservoirs has complicated controlling factors. Previous studies suggest that high-quality reservoirs are dominated by sedimentary facies, lithofacies and diagenetic facies, however, less consideration is given to other factors. According to the data of core, outcrop and rock flake of the system, it is considered that the influence of bioturbation structure on reservoir physical properties is also great, and the bioturbation intensity is directly proportional to reservoir physical properties. The study suggests that there are four lithologic-bioturbation assemblages in Upper Triassic in the Sichuan Basin: ① thick mud disturbance, mainly formed in thick black mudstone, reflecting the depositional environment of the lake or shallow lake; ② the boundary of sand and mud Disturbances, developed in the thick dark gray mudstone thin layer of light gray powder - fine sandstone, the disturbance index of 2 to 3, reflecting the lower end of the environment of the sand bar; ③ interbedded sand and mud thin interbed, mainly in sand and mud thin Layer, the thickness of the sand layer is 2 ~ 8cm, the thin sand-mud layer is interbed in the vertical direction, the disturbance index is 4 ~ 5, which reflects the upper environment of the distal sand bar in the delta front; ④ The disturbance of the thick sand layer mainly develops in the thick layer Sandstone, the disturbance index is 1 ~ 2, indicating that it is formed in the relatively strong water body underwater branch channel environment. The bioturbation structure is positively correlated with reservoir physical properties, ie, the stronger the biological disturbance is, the better the physical properties of the reservoir are; and the weakly disturbed or undisturbed parts of the primary pores are densely cemented and the porosity and permeability are very poor. This is mainly because bioturbation can improve the homogeneity of rocks and the sorting of rock particles.