Abstract:
This paper is the result of oil and gas exploration engineering.
Objective The southwestern margin of the Xuefeng Uplift exhibits intricate tectonics and low shale gas exploration maturity. This study evaluates the shale gas potential of the Niutitang Formation in the region, identifying favorable areas for shale gas exploration to support future drill site placement.
Methods Focusing on the black shales of the Niutitang Formation, this research integrates regional data, cross-sections, core observations, organic geochemical analyses, petrophysical tests, argon ion polishing combined with scanning electron microscopy, gas content, preservation conditions analysis, and recent drilling results. The study characterizes the geological conditions of shale gas in the region, identifies favorable areas, and preliminarily estimates resource volumes.
Results (1) Organic-rich shale deposition in the Niutitang Formation is influenced by deepwater shelf environments, with thickness increasing from northwest to southeast; (2) High organic richness is observed in the Niutitang Formation, with an average total organic carbon content of 4.95%, δ13C values of the kerogen averaging from −33.04‰ to −33.87‰ indicative of type I kerogen, and Ro maturity values ranging from 2.4% to 2.6%, showing moderate thermal evolution; (3) The Niutitang Formation exhibits high quartz content with storage spaces primarily composed of intergranular pores, intragranular pores, organic pores, and fractures, with an average porosity of 6.78% and an average permeability of 0.0580×10−3 μm2, representing a low porosity-low permeability to low porosity-ultra-low permeability reservoir.
Conclusions Through a multifactor overlay approach, favorable exploration areas for shale gas within the Danzhai, Xuanwei, and Majiang regions of the Niutitang Formation have been identified, with geological resource estimates totaling 3995.39×108 m3.
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