The Doushantuo shale in the Yichang area of South China, a newly discovered Ediacaran gas shale, is important in evaluating the potential of Precambrian source rocks. The shales, with great thickness (50 ∼ 130.5 m), high total organic carbon (average TOC is 1.64%), and moderate thermal maturity (Ro is 1.8%∼2.5%), have a favorable hydrocarbon generation potential. Multiple techniques, e.g., gas adsorption, scanning electron microscopy (SEM), nano- and micro-computed tomography (CT), were subsequently carried out to evaluate the pore systems. Both organic and inorganic pores are considered major storage spaces. The size of organic pores is generally < 30 nm, while inorganic pores are closely related to macro-pores. The full-scale pore size distribution revealed that the average pore volume ratio of micro-, meso-, macro-pores, and micro-fractures is 20.15%, 46.83%, 21.64%, and 11.38%, respectively. Macro-pores and micro-fractures also play a decisive role in shale gas enrichment except migration. The development degree of inorganic pores was determined by TOC and carbonate contents. Three enrichment models, i.e., Type I (continuous deep burial with limited uplift amplitude), Type II (significant burial depth with substantial uplift amplitude), and Type III (moderate burial depth with moderate uplift amplitude), were proposed based on the burial history of shale strata. The Doushantuo shale falls into Type II, and its favorable combination of generation, storage, and preservation conditions suggests promising exploration potential. This study demonstrates that the Doushantuo shale is likely to become a new set of strata for the deep exploration of shale gas in southern China.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)