Oil-soaked Dolomite in Upper Reach of the Shenglihe River,Northern Qiangtang
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摘要: 北羌塘坳陷南部胜利河上游出露油浸白云岩,层位为中侏罗统布曲组上部,近水平产状,下伏TOC含量高的黑色泥页岩。油浸白云岩呈灰黑色,原岩为生物碎屑灰岩,经历了白云岩化作用;表面覆盖烟灰状沥青,内含易于挥发的轻质油;地表样品含油率为765×10–6,远高于南羌塘坳陷隆鄂尼—昂达尔错古油藏地表出露的白云岩油砂(含油率（12～236）×10–6)。胜利河油浸白云岩裂隙发育,孔隙度为6.49%、渗透率为3.81 mD,属于羌塘盆地有利储层。油气地球化学及油源对比结果显示,胜利河油浸白云岩原油来源于中下侏罗统富有机质泥页岩。胜利河油浸白云岩对北羌塘坳陷油气勘查评价具有重要指示意义。Abstract: Oil-soaked dolomite discovered recently in the upper reach of the Shenglihe River, south of the Northern Qiangtang Depression, belongs to the upper section of the Middle Jurassic Buqu Formation. The dolomite is dark gray, gently dipping, and overlies dark mudstone and shale of higher total organic carbon content.Microscopic observation of the dolomite revealed dolomitization of bioclastic limestone. The oil-soaked dolomite is covered by ashy asphalt near the surface, and the light crude oil in fractures of the dolomite is volatile. The oil content of the dolomite sampled in the Shenglihe area reaches 765×10–6, which is much higher than the oil content of the dolomite oil sand outcropping in the Long’eni–Andarco Belt(（12–236）×10–6) in the Southern Qiangtang Depression. The oil-soaked dolomite is a favorable reservoir with a porosity of 6.49% and permeability of 3.81 mD. Petroleum geochemistry and biomarker parameters indicate that the crude oil of the dolomite in the Shenglihe area was derived from the Early–Middle Jurassic dark shale and mudstone enriched in organic matter.The oil-soaked dolomite in the Shenglihe area indicates a potential for petroleum resources in the Northern Qiangtang Depression.
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