An analysis of the depositional facies of T1j21－T1j1 and T1j51 layers of Lower Triassic Jialingjiang Formation in Chishui area

Abstract：The depositional facies of Lower Triassic Jialingjiang Formation in Chishui area of Guizhou belongs to continental-marine carbonate platform deposition. Based on field outcrop in combination with drill core, this paper divided the sedimentary facies into several types and pointed out that beach subfacies and dolomite-flat microfacies are depositional faices zones in favor of the development of T1j21－T1j1 and T1j51 reservoirs in this area and, using the “single factor analysis and multifactor integration graphing method”,obtained compositional thickness percentage distribution trend of different petrographic categories in the T1j21layer. On such a basis, the depositional facies of T1j21－T1j1 and T1j51favorable segments were also analyzed. It is thus concluded that, except for the southeast part of the Baoyuan structure, the Wunan structure, the Tai-9 well field and the Xue-1 well field, the T1j21－T1j1 layers mostly have quite favorable dolomite-flat microfacies,with the development of beach subfacies at the top of T1j1 layer in certain places. The development of T1j51 layer dolomite-flat microfacies is better in the southeast than in the northwest,with the central southern part of the Baoyuan structure being the best, the Wanglong structure possessing the second place,the Xuebaiping structure probably fairly good, and Taihe and Wunan structures being the worst. The deposition of the platform inner bar is localized around Wang12 and Wang 6 well area of the Wanglong structure.