The influence factors of gas-bearing and geological characteristics of Niutitang Formation shale in the southern margin of Xuefeng Mountain ancient uplift: A case of Well Huangdi 1

Abstract

ABSTRACT: In order to evaluate the geological characteristics and gas-bearing factors of Niutitang Formation within the Lower Cambrian of northern Guizhou, the Huangping area located at the southern edge of the ancient uplift belt of Xuefeng Mountain was selected as the target area, and Well Huangdi 1 was drilled for the geological survey of shale gas. Through geological background analysis and well logging and laboratory analysis such as organic geochemical test, gas content analysis, isothermal adsorption, and specific surface area experiments on Well Huangdi 1, the results show that the Niutitang Formation is a deep-water shelf, trough-like folds and thrust fault. The thickness of black shale is 119.95 m, of which carbonaceous shale is 89.6 m. The average value of organic carbon content is 3.55%, kerogen vitrinite reflectance value is 2.37% and kerogen type is sapropel-type. The brittle mineral content is 51% (quartz 38%), clay mineral content is 38.3%. The value of porosity and permeability are 0.5% and 0.0014 mD, which the reservoir of the Niutitang Formation belongs to low permeability with characteristics of ultra-low porosity. The gas content is 0.09 −1.31 m3/t with a high-value area and a second high-value area. By comparing with the geological parameters of adjacent wells in the adjacent area, the accumulation model of “sediment control zone, Ro control zone, structure controlling reservoir” in the study area is proposed. Therefore, deep-water shelf-slope facies, Ro is between high maturity-early stage of overmaturity and well-preserved zones in the Niutitang Formation in this area are favorable direction for the next step of shale gas exploration.