关键词: 页岩气, 储层特征, 含气性, 沉积相, 牛蹄塘组, 鄂西地区

Abstract: The Lower Cambrian Niutitang Formation is one of the major shale gas exploration fields in western Hubei. In order to further understanding the shale gas reservoir and gas-bearing properties of the Niutitang Formation, drilling and stratigraphic profile data were used to comprehensively analyze the rock formation, sedimentary facies, shale burial depth, shale thickness, geochemical properties, reservoir physical and gas-bearing properties. Research indicates that the Niutitang Formation in western Hubei can be divided into two members according to the lithofacies. Shallow-water and deep-water shelf facies are dominant in this area with the wider distribution of deep-water shelf facies. There are three underwater uplifts in Xingshan County-Yichang City. Laifeng County-Enshi City and Shennongjia shows the maximum shale thickness of more than 200.0 m. The TOC of Niutitang Formation gradually decreases from bottom to top. The Xianfeng-Hefeng area shows a high regional TOC distribution and the corresponding TOC is dominated by high and extra-high levels of greater than 2.00%. The R_o is about 2.0%～3.5% in high maturity stage. The mineral components are dominated by clay minerals and quartz, and the clay mineral content gradually increases from bottom to top. The Niutitang Formation is considered as a low-porosity and ultra-low permeability reservoir. The gas content of Niutitang Formation increases rapidly and then gradually decreases. The lower part of the Niutitang Formation shows a maximum gas content in the longitudinal direction and the relatively high gas content laterally distributes in the southeast flank of the Huangling anticline. Comprehensive analysis suggests that the favorable exploration zones are locates in the wide and gentle anticline wings within the deep-water shelf facies and far away from the regional fault zone. This research could provide certain reference for the shale gas exploration well deployment in the Niutitang Formation of Western Hubei.

Key words: shale gas, reservoir property, gas-bearing property, sedimentary facies, Niutitang Formation, western Hubei