Discussion on the uniformity of shale oil and gas in China

Abstract

Shale oil and gas are important strategic resources in China's energy sector, existing in shale formations with self-generation and self-storage characteristics. In 2012, a significant breakthrough was achieved in Fuling, China, with the discovery of marine shale gas, which led to the formulation of the "two-factor enrichment" theory. This theory proposes that the development of high-quality mud shale in deep-water continental shelves is fundamental for hydrocarbon generation and controlled storage, while favorable preservation conditions are key to reservoir formation and controlled production. Recent efficient exploration and development practices in shale oil and gas have indicated that China's continental shale oil also exhibits "two-factor enrichment" characteristics. By analyzing the characteristics of typical shale oil and gas reservoirs in China, this study incorporates shale oil and gas into a unified system of hydrocarbon formation, storage, and accumulation, further deepening the theoretical connotation of the "two-factor enrichment" theory and forming a new understanding of the uniformity in shale oil and gas enrichment. Future research trends are also explored. Results show that: (1) Sedimentary environments dominated by semi-deep to deep-water continental shelves and semi-deep to deep lakes are the basis for hydrocarbon generation and controlled storage, controlling both the abundance and type of organic matter in shales as well as the distribution of high-quality reservoirs and favorable lithofacies combinations. (2) Stable tectonic conditions, effective top and bottom seals, and self-sealing properties of shale, in conjunction with overpressure, provide good preservation conditions that are crucial for reservoir formation and controlled production, providing key guarantees for the enrichment and high production of shale oil and gas. (3) The formation and enrichment of shale oil and gas are part of a unified dynamic evolutionary system, with thermal evolution as the main driver, following the sequential formation of shale oil, condensate oil, and shale gas. (4) Future study should focus on strengthening the integrated evaluation of conventional and non-conventional resources, deepening the understanding of distribution coefficients for conventional and non-conventional oil and gas, and considering the distribution patterns of oil and gas from a holistic perspective. The research results have important scientific and practical significance for deepening the theory of shale oil and gas enrichment and guiding their exploration and development.

Keywords

• shale oil and gas
• enrichment characteristics
• sedimentary environment
• preservation condition
• thermal evolution degree
• uniformity