Transformations and genetic models of the Lower Paleozoic carbonate reservoirs interpreted by the whole petroleum system in the platform-basin area, Tarim Basin

Deep carbonate hydrocarbon reservoirs in the platform-basin area of the Tarim Basin represent a significant hydrocarbon pay interval in China, holding considerable resource potential. However, their transformation characteristics, genetic models, and distribution patterns remain poorly understood due to the influence of multi-phase tectonic activities, multi-stage hydrocarbon charging, and late-stage adjustments and modifications. These hinder the progress of effective deep and ultra-deep hydrocarbon exploration therein. Based on the theory of the whole petroleum system, we systematically investigate the transformation processes and genetic models of the Lower Paleozoic carbonate hydrocarbon reservoirs in the platform-basin area of the Tarim Basin. The results indicate that the reformed carbonate hydrocarbon reservoirs in the platform-basin area exhibit several distinct characteristics: (1) tectonization-induced failure of the dynamic boundaries for hydrocarbon accumulation; (2) tectonic movement-induced failure of the dynamic fields for hydrocarbon accumulation and migration; (3) the transformation of early-stage continuous, tight reservoirs into conventional fractured, fractured-vuggy, or pore-cavity reservoirs; (4) the formation of superimposed, consistently distributed hydrocarbon reservoirs, and (5) the emergence of novel fault-karst hydrocarbon reservoirs. These reservoirs are governed by the dynamic coupling of multiple factors, including sedimentary evolution, tectonic movements, hydrocarbon accumulation and migration stages, and preservation conditions. The failure of the dynamic boundaries for hydrocarbon accumulation occurred after three evolutionary stages of physicochemical effects. The reformed hydrocarbon reservoirs display an orderly distribution pattern characterized by vertical layering and lateral zoning. The vertical layering is primarily determined by the differences in lithologic assemblages and depositional environments, while the lateral zoning is controlled by the developmental degrees of faults and unconformities. In the platform-basin area, reef-shoal and unconformity-controlled pore-cavity reservoirs are predominantly distributed within free hydrodynamic fields. In contrast, fault-controlled fractured reservoirs are typically found in constrained hydrodynamic fields between the buoyancy-driven hydrocarbon accumulation depth (BHAD) and the baseline of hydrocarbon accumulation.