The Structural and Diagenetic Coupling Controls the Distribution of Deep Carbonate Rock Reservoirs in the Southern of Tahe Oilfield, Tarim Basin

Deeply buried carbonate successions in China’s Tarim Basin host substantial hydrocarbons. In the southern Tahe Oilfield, Middle–Lower Ordovician limestones show little evidence of subaerial weathering because the Upper Ordovician strata protected them; nevertheless, the genesis and evolution of these carbonate reservoirs remain debated. Using cores, conventional and image logs, 3D seismic interpretation, and geochemical data, this study characterizes Paleozoic faulting and diagenetic fluids in the area. Four principal fluid types are identified—meteoric water, formation water, hydrothermal fluids, and mixed fluids. Two episodes of NNW- and NNE-trending strike-slip faulting during the Middle Caledonian and Early Hercynian periods facilitated fluid migration and dissolution. Later, Late Hercynian faults acted as primary pathways for hydrothermal flow, promoting the development of hydrothermal dissolution pores and caverns. The work clarifies how the interplay between strike-slip faulting and distinct diagenetic fluids governs reservoir development, providing theoretical guidance for predicting deep carbonate reservoirs and for hydrocarbon exploration and production.