Sedimentary Facies And Oil-Gas Distribution Characteristics Of The Silurian In Tarim Basin

There are abundant hydrocarbon resources in Silurian reservoirs in Tarim basin, and the stratum of the Silurian is the key exploration stratum in Tarim basin. At present the silurian series research is facing the questions which multitudinous need to be solved, such as the sandbody macrofacies distribution rule, the high quality reservoir and the favorable facies belts of hydrocarbon accumulation, key factors controlling the hydrocarbon accumulation and so on. In connection with the problems exit in Tarim basin Silurian series research, the paper , that integrates the comprehensive earthquake, the well drilling geology, the oil well logging and the modern analysis chemical examination material, uses the reservoir sedimentology new theory and the reservoir description new technology, to analyses the deposition system, to rebuild the Silurian palaeogeography, and to analyses the prospect for petroleum exploration. The results are as follows.(1)In the Silurian Sedimentary Period, the Structural framework and evolution of Tabei uplift was the key factor controlling the evolution of the palaeogeography in Tarim basin. In the lower and middle member of Kalpingtag Formation sedimentary period, the Tabei uplift was not an important source area. In the upper member of the Kalpingtag Formation sedimentary period, the Tabei upleft had formed a very important source area, but there were many place with the broad sea link channel in the basin, so the Silurian palaeogeography of Tarim basin showed a peculiarity,wich were "there is not only a sea in the mountain but also a mountain in the sea".(2) The paper has built sedimentary models of Kalpingtag Formation in Tazhong area, which are braided delta, estuary and complex delta. During the lower member of Kalpingtag Formation sedimentary period, the sea level was rising, the coastline advances from north to south. Tazhong area received abundant clastic sediments from the east uplift, and it formed transgressive braided deltas. At the upper 2nd member of Kalpingtag formation sedimentary period the sea level was the highest during the Silurian sedimentary period, and estuarine deposit system well developed in the Tazhong area. At the upper 1st member of Kalpingtag formation sedimentary period, complex delta deposit system developed in the Tazhong area, which was influenced by the cooperation of river, tide and wave.(3) The paper has built sedimentary models of Kalpingtag and Tataairtag Formation in Tabei and Tadong area, which are braided delta and terminal fan. At end of the lower member of Kalpingtag Formation sedimentary period, Tabei uplift had been elevated gradually, and then it produced clastic sediments for Tabei area in the upper member of Kalpingtag Formation sedimentary period. The clastic sediments that deposited in Tadong area mainly come from northeast and southwest of Tarim basin, and the supplies is extremely sufficient, so coarse grain braided delta systems developed in Tadong area. During Yimugatawu formation sedimentary period, there are terminal fan depositions in Tabei and Tadong area.(4) According to the homogenization temperature of fluid inclusions distribution, unifies the subsidence and burial History, the Silurian series in Tarim basin have three episodes of oil/gas charge. The advantageous area is predicted based on kinds of conditions for hydrocarbon accumulation and a definitude direction is given to oil-gas exploration.