鄂尔多斯盆地南部三叠系油页岩地质特征及富集规律

Geologic Characteristic and Regular Pattern of Triassic Oil Shale South of Ordos Basin

通过对鄂尔多斯盆地南部地区长7段油页岩样品分析,结合盆地南部地区三叠系油页岩沉积时期的地质特征,认为该区长7段富集的油页岩为古气候、古构造、古沉积环境共同影响下形成的。温暖、潮湿的古气候有利于提高沉积盆地中湖泊初始生产力。长8段沉积末期,盆地西缘和西南缘发生的火山喷发事件导致长7沉积期形成以深湖相为主的沉积格局,有利于有机质的富集;在长7段底部由火山喷发产生的凝灰物质形成的凝灰岩的纹层可起到隔氧的作用,有利于油页岩的保存。深湖相沉积环境发育的油页岩总厚度最大,含油率较高,其次为半深湖—浅湖相,表明长7段油页岩发育的厚度明显受沉积相控制。

Through the analysis of oil shale samples of the 7th Member of Yanchang Formation, and combined with geological features of Triassic sedimentary period of oil shale in the south of Ordos Basin, it is believed that the rich oil shale of the 7th Member of Yanchang Formation was formed affected by paleoclimate, structure, and sedimentary environment. Warm and moist paleoclimate is conducive to improving the initial productivity of lakes in the sedimentary basin. At the sedimentary end of the 8th Member of Yanchang Formation, volcanic eruption events occurred on the west and southwest margin of the basin led to the formation of the sedimentary pattern dominated by deep lake of the sedimentary period of the 7th Member, which was favorable for enrichment of organic matter. Tuff bed generated from tuff particles produced by volcanic eruption at the bottom of the 7th Member of Yanchang Formation could insulate oxygen and be conducive to oil shale preservation. Oil shale developed in deep lake sedimentary environment is the thickest and has higher oil content, and is semi-deep and shallow lake facies. It indicates that the thickness of oil shale in the 7th Member is obviously controlled by sedimentary facies.