Study On Shale Facies And Its Control Gas Characteristics In Eastern

Based on the National-973scheme "Prediction and Characterization of Favorable Shale Reservoir", this paper mainly studies about the marine shale of Wufeng-Longmaxi formation in East Sichuan and the periphery region of it. It was widely recognized in the past that the shale in specific sequence didn’t change obviously, thus there were not many researches on shale lithofacies. In recent years, as people put more and more emphasize on explorations of shale gas, searching for fine compressible organic-rich shale zone has become the main object of shale exploration, and the two factors are directly related to lithofacies. Therefore, based on the studying of sedimentary charateristics of Wufeng-Longmaxi formation in East Sichuan and its periphery region, this paper classfies the shale lithofacies of X region in East Sichuan, analyzes the characters of shale lithofacies and gas controlling factors, and predicts the shale lithofacies that favour production. It achieves results as follows:(1) Three outcrops of Shuanghe section, Qilong section and Guanyinqiao section are surveyed, a set of organic-rich shale are deposited in Wufeng-Longmaxi formation of these three sections, sedimentary facies can be divided into deep water shelf facies and shallow shelf facies. On this basis, six vertical wells were selected as standard wells in order to analyze the sedimentary sequence in X region. By using sign pattern comparison method, the paper completed the single well sedimentary facies division of the six wells by the method of sign pattern comparison, and found out the vertical and plane distribution characteristics of microfacies of Wufeng-Longmaxi formation in X region.(2) The sedimentary model of Wufeng-Longmaxi formation in East Sichuan was established. This paper suggests that Wufeng-Longmaxi formation shale is mainly influenced by structure and the fluctuation of sea level.The entire East Sichuan area is in the environment of the half confined back-bulge deep-water basin, in which a set of organic-rich shale is deposited.(3) In consideration of the gas-bearing property and shale mineability, this paper completed marine shale lithofacies division of Wufeng-Longmaxi formation in X region according to the organic and silicon content of shale and combination of the shale lithofacies by observing the outcrop, core and slice. It divided the shale lithofacies into carbon-rich high silicon shale lithofacies, high carbon high silicon shale lithofacies and other17types of lithofacies.(4) Based on the analysis of shale gas occurrence and its gas content, it shows that carbon-rich high silicon shale lithofacies and high carbon high silicon shale lithofacies have high gas content and gas production of all shale lithofacies types, while high carbon medium silicon shale, high silicon medium carbon containing silty shale lithofacies also has a high gas content by comparing statistics of various shales and their reservoir properties, shale gas content and open flow capacity.