CHARACTERISTICS OF THE SILURIAN HYDROCARBON ACCUMULATION IN THE SOUTHERN TAHE REGION, THE TARIM BASIN

The distribution pattern of the Silurian hydrocarbon accumulation in the southern Tahe region,the Tarim Basin has been established and the direction of oil and gas exploration in this region has been predicted based on the research results of the reservoir characteristics,the accumulation conditions and the controlling factors of the hydrocarbons in the Silurian Kepingtage Formation.The sandstone reservoir of the Kepingtage Formation is of low porosity and low permeability,with some high quality thick layers of the shore phase,the delta distributary channel phase,the channel-mouth bar phase and the tidal channel phase developing locally.The Kepingtage Formation sandstone reservoir is characterized by deep burial,large area,low abundance,thin hydrocarbon layer,fault conduit,and superimposition of layers.Hydrocarbons generated from the Cambrian-Ordovician source rocks in the southern Tahe region migrated through the faults,the fractures,the sandstones and the uncomformities in the Upper Ordovician Sangtamu Formation into the Kepingtage Formation and accumulated as hydrocarbon reservoirs.The hydrocarbon reservoirs in the Kepingtage Formation mainly formed during the Himalayan period and can be divided into four types,including anticline reservoir,stratigraphic unconformity reservoir,stratigraphical overlap reservoir and lithologic reservoir.The region around the Silurian erosional pinch-out line is favorable for developing stratigraphic unconformity reservoirs,whereas the area southward is favorable for developing anticline,lithologic and stratagraphic overlap reservoirs.