Weathered crust karst reservoirs with intricately interconnected fractures and caves are common but challenging enhanced oil recovery (EOR) targets. This paper investigated the remaining oil distribution rules, formation mechanisms, and EOR methods through physical experiments on acrylic models resembling the geological features of weathered crust reservoirs. Acrylic models with precision dimensions and morphologies were fabricated using laser etching technology. By comparing experiments under different cave filling modes and production well locations, it was shown that a higher cave filling extent led to poorer bottom water flooding recovery due to stronger flow resistance but slower rising water cut owing to continued production from the filling medium. Multi-well water and gas injection achieved higher incremental oil recovery by alternating injection–production arrangements to establish new displacement channels and change drive energy. Gas injection recovered more attic remaining oil from upper cave regions, while subsequent water injection helped wash the residual oil in the filling medium. The findings reveal the significant effects of fracture cave morphological configuration and connectivity on remaining oil distribution. This study provides new insights and guidance for EOR design optimization catering to the unique features of weathered crust karst fractured vuggy reservoirs.
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