Parameter Calibration and Validity Evaluation Method for Ultra-Deep Paleokarst Reservoirs in Penglai Gas Area
The lamp shadow group,situated within the Penglai gas-bearing area,serves as a pivotal successor zone for hydrocarbon production within the Sichuan Basin.With depths ran-ging from 6 000 to 9 000 meters,this geological formation delves into the realm of ultra-deep-seated ancient karstic-fractured reservoirs,marking a significant frontier in petroleum explora-tion and exploitation.Within these reservoirs,a diverse array of storage space types prevails,characterized by intricate pore networks and heterogeneity stemming from a myriad of geolog-ical processes.Microscopic examination reveals a complex diagenetic history,where fractures and fissures,commonly infilled with hydrocarbon-bearing fluids,asphalt,and silica,attest to the dynamic interplay of chemical dissolution and mineral precipitation.The genesis and evolu-tion of these reservoirs are intricately governed by lithological controls,dictating the spatial distribution and connectivity of porosity and permeability networks.Lithological heterogenei-ty begets a mosaic of pore structures,ranging from microporosity within lithic grains to macroporosity manifested in dissolution cavities and fractures.Additionally,the presence of karstic dissolution caves,fractures,and fault-related conduits further complicates reservoir architecture and fluid flow pathways.In elucidating the complexities of these reservoirs,this study adopts an integrated approach,amalgamating rock physics experiments,advanced log-ging techniques,and seismic analysis.Specialized mineral corrections are applied to refine key reservoir parameters such as electrical resistivity,acoustic properties,and seismic attributes,enhancing the fidelity of subsurface characterization.Calibration wells serve as pivotal bench-marks for validating and calibrating logging responses,thereby facilitating the development of robust reservoir evaluation methodologies.Leveraging a comprehensive dataset,a holistic e-valuation index of reservoir effectiveness is devised,furnishing a systematic framework for reservoir characterization and performance assessment.This pioneering approach culminates in the formulation of rigorous criteria for discriminating reservoir effectiveness,achieving excep-tional accuracy rates surpassing 95% in delineating high-productivity reservoir zones.In es-sence,this study represents a seminal contribution to reservoir characterization,offering pro-found insights into the challenges and opportunities posed by ultra-deep-seated karstic-frac-tured reservoirs.By providing a solid technical foundation for reservoir interpretation,this re-search stands as a linchpin for optimizing hydrocarbon exploration and exploitation in this geo-logically intricate terrain.
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