川东北地区下三叠统飞仙关组白云岩成因类型

DOLOMITE GENETIC TYPES IN FEIXIANGUAN FORMATION OF LOWER TRIASSIC SERIES IN NORTHEAST AREA OF SICHUAN

本文研究了川东北地区下三叠统飞仙关组白云岩的岩石矿物学和地球化学特征，指出区内由泥—微晶白云石构成的白云岩，是在盐度较高的潮坪和局限—半局限台地泻湖环境中沉积的碳酸盐沉积物经准同生白云化作用改造而成的，岩石的孔、渗性均较差，且具有相对较重的碳、氧同位素，阴极发光呈暗红色，有序度很低，两相包裹体的均化温度约４０℃；且残余颗粒结构（鲕粒、内碎屑）的粉晶白云岩，是滩、坝等高能环境中的颗粒灰岩经成岩早、中期混合水白云化作用形成的，具有较好的孔、渗性，碳、氧同位素相对较重，阴极发光仅显微弱的暗紫红色，有序度较低，两相包裹体的均化温度约为６５℃；而细晶白云岩则是与受断裂作用有关的晚期埋藏白云化作用的产物，其孔、渗性极佳，碳、氧同位素值较轻，阴极发光仅在晶体边缘见红光，有序度较高，两相包裹体均化温度超过１２０℃，是十分有利的碳酸盐储层。通过对铁山、双家坝构造的综合研究和钻探表明，该区的细晶白云岩对油气的聚集做出了贡献。

The petro-mineralogy and geochemistry characteristics of dolomite in Feixianguan formation of Lower Triassic Series in northeast area of Sichuan are studied. The dolomicrite in the area is transformed through the penecontemporaneous dolomitisation of the carbonate sediment deposited in the lagoon environment of tidal flat with higher salinity and restricted-semirestricted tableland. The doldsiltite with residual grain framework is formed through the mixing water dolomitisation at the eogenetic and middle stages of grain limestone diagenesis in high energy environment of beach and for. The aplite-dolomite is the result of paulopost burying dolomitisation relative to rifting, and it is favourable carbonate reservoir. The comprehensive research and drilling of Tieshan and Shuangjiaba structures indicate that the aplite-dolomite in the area made a contribution to oil-gas accumulation.