Cambrian-Ordovician Carbonate Microfacies of Tazhong Area in Tarim Basin

摘要

This paper took two wells in Tazhong area as the research subject.The samples which are made by dyeing specimens are observed to achieve the calcite and dolomite' s grain size,shape and texture,the intercrystal pore types and pore throats,the physical properties and metasomatism of biodetritus,the shape,size and filling of stylolites and fractures with the microscope.The comprehensive sequence histograms of the two wells are analyzed and the result shown:in the Tazhong area it is a widespread phenomenon that the metasomatism between limestone and dolomite after the organic cavities and stylolites are filled by calcite results in the dolomite crystal grain being generally medium coarse and coarse which is larger than the deep dolostone.This texture is more favorable for the storage of hydrocarbon in the intercrystal pores to form the reservoir.Lithology transforms gradually from limestone to dolomitic limestone,then calcitic dolomite,and in the end,dolomite.The crystal grain also transforms from fine to coarse.In the aspect of the microfacies,the medium coarse and coarse-grained dolomite is more conducive to forming a high-quality reservoir than limestone.