272-9 Bedding-parallel stylolites in the Middle and Upper Ordovician limestones in the northern Tarim Basin: implications for fluid flow

Session: Faults, Fractures, and Geomechanics for the Energy Transition (Posters)

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There have been debates for several decades about whether stylolites in carbonates act as barriers or conduits with respect to fluid transport in sedimentary basins. The current study contributes to our understanding of the controls on stylolite development and its impact on the evolution of the transport properties and coeval to later diagenesis of the hosting carbonate rocks. These insights are based on observations from a case study of the Middle to Late Ordovician limestones in the Halahatang area, Tarim Basin, northwestern China. Quantitative characterization of the stylolites was conducted in 380 m carbonate cores from 16 wells, and petrographic and geochemical studies were completed on 240 samples. In the studied cores, both isolated and anastomosing stylolites are common. Dentate and seismographic stylolites are dominated; wavy type is moderately to sparsely present, and columnar stylolites are relatively rare. Distribution of euhedral to subhedral minerals (including quartz, dolomite, clay, pyrite, and apatite) along bedding-parallel stylolites indicates they once acted as conduits for diagenetic fluids. In addition, the stylolites might play an important role for hydrocarbon migration on the basis of the concentration of bitumen along them. The results reveal that stylolites can significantly influence a variety of diagenetic processes and reservoir properties. Stylolites require more attention to evaluate whether they are fluid-flow-efficient features owing to their prevalent presence in carbonate rocks.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8929

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