Song Yan, Wan Chengxiang. Mechanisms and differences of self-sealing in shale gas reservoirs of Longmaxi Formation in Sichuan Basin[J]. Acta petrolei sinica, 2025, 46(9): 1677-1687.
Song Yan, Wan Chengxiang. Mechanisms and differences of self-sealing in shale gas reservoirs of Longmaxi Formation in Sichuan Basin[J]. Acta petrolei sinica, 2025, 46(9): 1677-1687. DOI: 10.7623/syxb202509003.
Mechanisms and differences of self-sealing in shale gas reservoirs of Longmaxi Formation in Sichuan Basin
The self-sealing capacity of shale is a critical factor for the enrichment and accumulation of shale oil and gas. However
the current understanding of the self-sealing mechanism of shale oil and gas reservoirs remains insufficient
which severely restricts the development of unconventional oil and gas geology theories and the advancement of hydrocarbon exploration in China. An in-depth research on the self-sealing mechanisms and differences regarding typical marine shale gas will contribute to improving the unconventional hydrocarbon accumulation theories and guiding the exploration and development practice. This study focuses on the Longmaxi Formation shale in Sichuan Basin
and comprehensively using petroleum geology theory
nanoscale water film theory
and adsorption thermodynamics theory
as well as gas reservoir analysis
fine-scale reservoir characterization and theoretical calculations
the following three research achievements have been obtained. (1)This study clarifies the geological characteristics of the self-sealing system of Longmaxi Formation shale gas in Sichuan Basin
discovers the vertical variation patterns and differences in the total organic carbon (TOC)content
pore structure
and fluid characteristics of the shale. These factors serve as important geological foundations for the formation of the shale gas self-sealing system. (2)The study reveals the microscopic self-sealing mechanism in shale gas reservoirs. The tight shale reservoirs with poor pore connectivity facilitate physical self-sealing. The complex organic-inorganic pore system of shale
along with its gas-water distribution patterns
jointly contribute to the capillary force-driven self-sealing effect. This effect is dually controlled by pore structure and water saturation. Moreover
the adsorption capacity of shale can result in self-sealing capacity
which is primarily related to the specific surface area and TOC content of the shale
and is particularly remarkable in organic-rich shale. (3)An analysis has been performed on the vertical differences in self-sealing effects. The upper gas reservoir is dominated by capillary force-driven self-sealing
followed by physical self-sealing. In contrast
the lower gas reservoir exhibits a composite mechanism involving physical self-sealing
capillary force-driven self-sealing
and adsorption force-driven self-sealing. The research results are expected to provide valuable insights for improving the theoretical system of unconventional oil and gas accumulation
and guiding exploration and development practices.
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