Study On The Differences Of Reef Beach Reservoir Of Lianglitag Formation,Upper Ordovician Along Northern And Southern Platform Margin In Tazhong Area

Tazhong region is the important target area of oil-gas exploration in Tarim Basin, and the reef-beach reservoir of lian glitag formation in northern pl atform margin and southern platform margin is the main reservoir area of oil-gas resources. Predecessors have done som e researchs about the liangli tag formation of northern platform and southern platform margin. but the fine division of sedimentary microfacies of the two sides platform margin, the difference of reservoir between the dif ferent microfacies and causes of the difference remains to be further research.On the basis of previous studies, with m odern petrology, sedimentology and reservoir geology theory as the instruc tion, using the method of combining the macroscopic research and m icroscopic analysis, from the existing seism ic, core, drilling, and various advanced testing analysis of actual da ta, this article researched the reef-beach sedim entary microfacies characteristic and dif ference of uppe r ordovicion lianglitag form ation between northern platform and southern platform margin.on the basis of above, com bined with the test data, compares and analysis the difference of reservoir of the sedim entary microfacies in the two platform margin. And combined with the diagenesis, tectonic background and sedim entary background,made a comprehensive analysis for the causes of the dif ference of the reef-beach in the two platform margin. All of these provide important geological basis and reference for the favorable explorati on area in tazhong region. This paper has made the following points:(1).The reef-beach sedimentary microfacies of lianglitag formation in northern platform margin and southern platform margin can be divided into reef base, reef core, reef-beach, bioclast beach, sand-gravel beach and oolitic beach.And the difference of sedimentary microfacies in the two side s mainly reflected in the lithologic combination, biological combination,reef body size and reef development cycle.(2).On the basis of fine divided and compared for sedimentary m icrofacies, analysis difference of the res ervoir rock types, thetypes of reservoir space and reservoir performance of the two sides platform margin. The results showd that on the transverse, the reef-beach re servoir performance in nort hern platform margin is superior to the southern platform margin.on the longitudinal, in the northern platform margin, the reservoir perform ance of reef co re is superior to th e bioclast beach and sand-gravel beach, and the reef-beach, reef base and oolitic beach take the other place. In the southern platform margin, the microfacies of the reservoir performance for reef core>reef beach>bioclast beach>reef base>sand-gravel beach>oolitic beach. Because of the reef is smaller and the its quantity is less in southern platform margin, so in the so uthern platform margin, the microfacies reservoir of beach is the m ain quality reservoirs.(3).Combined with the tectonism, sedimentation and diagenesis analysis, research the causes of the reservo ir difference in the two sides.the resu lt showed that the ancient geomorphology and sedimentary background caused by tectonism is the material basis of the difference, sedimentary facies is the basis caus es that led to the difference of dif ferent sedimentary microfacies, and the dif ference of diagenesis ultimately determines the quality of the reservoir development.