车西洼陷沙三上亚段滑塌浊积砂体的沉积特征

Sedimentary characteristics of the fluxoturbidite of the upper submember of Sha 3 in Chexi Subsag

沙三上亚段沉积期,在车西洼陷南坡曹家庄断阶带的车40和车44断阶发育了数量众多的滑塌浊积砂体.通过大量的岩心观察和相关测试资料分析,对滑塌浊积砂体的岩性以及空间展布特征进行了研究.结果表明,浊积砂体具有成分成熟度和结构成熟度低的特点,结构和构造均反映砂体为滑塌后再沉积的产物.总结了滑塌浊积砂体的3种相序类型,即正粒序重力流型、正递变重力流型、砂泥互层型.对不同砂组储层的空间展布形态和发育规模进行了研究.分析了滑塌浊积砂体的成因机制,认为三角洲的快速推进为其形成提供了先决条件,而同沉积断裂强烈活动引发的地震是其最主要的触发机制.

During the depositing period of the upper submember of Sha 3,rich fluxoturbidite is developed in Che 40 and Che 44 fault blocks of Caojiazhuang step-fault zone in the southern slope of Chexi Subsag.The lithology and the spatial distribution are studied according to the observation of cores and the experimental data.The study results show that the fluxoturbidites have lower compositional and textural maturities,with the characteristics of slumping redeposition.There are three facies sequence types,namely,normal graded sequence gravity flow,normally grading gravity flow,interbed of sandstone and mudstone.The reservoir spatial distribution characteristics and the development scale of different sandstone groups are studied.The genetic mechanism of the fluxoturbidite sandbodies is analyzed,and it is held that the rapid advance of delta is the precondition to forming the fluxoturbidite sandbodies,and the seismic process aroused by the strong activity of syndepositional faults is the uppermost triggering mechanism.