Abstract:

Based on an integrated analysis of the conditions of hydrocarbon pooling,types and distribution of the reservoirs in the Lower Silurian Kepingtage Formation in the southern Tahe region of the Tarim basin,this paper focuses on the distribution patterns of the Silurian hydrocarbon reservoirs in the southern Tahe region and estimates the hydrocarbon potential in this area.The Kepingtage sandstones are reservoir rocks with low porosity and low permeability,but some of them are quality reservoirs,such as thick shoreside facies,distributary channels in delta,mouth bars and tidal channel.Several reservoir-seal combinations were developed in the Silurian.Hydrocarbons generated from the Cambro-Ordovician source rocks in the southern Tahe region migrated to and accumulated in the Kepingtage sandstones through Upper Ordovician Sangtamu mudstone via faults,fractures,sandstone layers and unconformities.Five types of reservoirs,including anticline,unconformity barrier,onlap,lithological and structural-lithological combination reservoirs,are recognized in the Kepingtage Formation and were mainly developed in the Himalayan period.The unconformity barrier reservoirs are mainly distributed around the denudation pinch-out line of the Silurian in the high of the northern Tahe area,while the anticline,onlap,lithological and structural-lithological combination reservoirs are mainly distributed in the southern Tahe area.The Silurian sandstone in the study area has the characteristics of deep burial,large area of distribution,low abundance,thin hydrocarbon-bearing layers,linkage via faults and overlapping of oil-bearing areas.The estimated oil reserves in the Silurian are about 160 million tons.Moreover,tight sands gas reservoirs may also occur in the study area.

Key words: reservoir rock, reservoir type, distribution pattern, hydrocarbon potential, Silurian, southern Tahe