Guizhou The Chishui Areas Yangxin System, In The Upper Triassic And Lower Jurassic Sedimentary Facies And Reservoir Characteristics

The research area is at the area between Guizhou and Sichuan Provinces,which is belong to Chishui city, Xishui county of Guizhou Province and Luzhou city of Sichuan Province,the area is about 4600km2.Through a lot of in door and outdoor work,some achievements are obtained in this paper:1. Maokou Fm. is shallow ramp sediments,the reservoir characteristics was controlled by paleo-weathering crust, geological movement and corrosion in depth.2. In the geological history, the distribution and the development of sedimentary facies was controlled by the regional tectonics and the regional relief.3. The Luzhou Uplift, which was under the influence of Dongwu Movement, was one of the important controlling factors for the distribution of facies. During the Early and the Middle Triassic, the Luzhou Uplift stretched to the south, the Baoyuan and the Longzhao are as located at the Seslope of the Luzhou Uplift, the position of the Baoyua was higher than that of the Lonzhao. At the high part of the Uplift, the open sea environment had the stronger hydro-energy, the different banks had been deposited at this area which are better for reservoirs formation. From the higher part to the lower part of the Uplift, along with the depth of water increased, the thickness of sediments increased, and the grain of the sediments decreased which was the representative of deeper water deposition.4. The Luzhou Uplift also controlled the diagenism of this region. The meteoric water diagenetic facies and evaporative facies distributed at the high part of the Uplift, the constructive diagenism such as evaporative dolomization, mixed dolomization, meteoric water corrosion. At the lower part of the Uplift, such as Lonzhao area, the seepage reflux dolomization developed.5. According to the sedimentary facies distribution and regional deposits characteristics , the regional topography characteristic controlled the Early and the Middle Triassic reservoirs distribution, the reservoirs at Longzhao area are better than that of at Baoyua area.6. During the Later Triassic, the first, the third and the fifth members of Xujiahe Fm. were the thin mud deposits with lower organic contain which was belong to the front delta subfacies and littoral and shallow lake subfacies. The second, the forth and the sixth members of Xujiahe Fm. contain middle-thin grain feldspathic quartz sandstone or lithic sandstone with micro-pore pores.7. The Lower Jurassic strata deposited in the arid-semiarid climate as the lake-delta and some fluvial facies with lower organic material. Both the porosity and the permeability of the Lower Jurassic are also lower than that of the Xujiahe Fm. With the fissure-micro-pore pore type, the Lower Jurassic belongs to the low porosity-permeability reservoir.