柴达木盆地西南区震积作用及其研究意义

Seismic Deposition in Southwestern Qaidam Basin and Its Implication

研究表明,柴达木盆地西南地区地震活动强烈,深、浅层均发现一系列与古地震有关的震积岩,形成一系列软沉积物变形构造,主要包括震积砂枕、砂球构造、枕状层、液化砂泥岩脉、层内错断、地裂缝、微褶皱纹理、沙侵蘑菇等。研究区震积岩的岩石类型则主要包括震褶岩、震裂岩、震塌岩、自碎屑角砾岩、自碎屑副角砾岩、液化角砾岩及震浊积岩等。地震活动使岩层产生大量的微裂缝,裂缝沟通了原有的孔隙,同时增加了储集层的储集空间,极大地改善了储集层的渗透性,并使原先不具渗透性的砂泥薄互层产生裂缝,成为输导层,这为在地震断裂系统附近寻找低渗透岩层中的高渗储层提供了新的方向。而地震断裂系统上倾的三角洲前缘水下分流河道、河口坝砂岩以及滨浅湖滩坝所构成的岩性圈闭必将成为柴西南地区岩性油气藏勘探的新领域。

Earthquakes occured overmuch and seismites developed in southwestern Qaidam basin. The seismites made serious seismic-related soft-sediment deformation structures, including pillow structure, ball structure, pillow bed, liquefied sand-stone vein, liquefied mudstone vein, micro-fault, micro-fracture, micro corrugated lamination and sandstone fungus. Seismites can be subdivided into many types,such as seismic corrugated rock, shattered rock, seismic collapse rock, autoclastic breccias, intraclastic parabreccia, liquefied breccia and seismoturbidite rock. Earthquakes made a great amount of micro fractures connecting with original pores of the rocks, therefore greatly improved the storage and permeability of reservoirs. Also earthquakes made fractures penetrating interleaved sand and mud beds. These provide a direction to find high permeability reservoirs in low permeability rocks near earthquake rift systems. The lithologic trap, constituted of the updip sand of the underwater distributary channel, mouth bar of the delta front, the beach bar sand of the mere and shore in seismic faulted system,will be a new exploration territory of lithologic reservoir in southwestern Qaidam basin.