Enhancing the Accuracy of Gas Breakthrough Timing Through Comprehensive Approaches to Sub-Seismic Scale Karst as High Permeability Streaks in a Heterogeneous Giant Carbonate Reservoir, Offshore Abu Dhabi

Accurate modeling of gas breakthrough timing is essential for optimizing reservoir management and development strategies in heterogeneous, giant carbonate reservoirs. This study introduces a comprehensive approach to simulate High Permeability Streaks (HKS) at sub-seismic resolution, with a focus on karst-associated features in offshore Abu Dhabi, United Arab Emirates. Although the modeled permeability-thickness (KH) values were successfully aligned with those derived from well test during dynamic history matching, notable discrepancies in gas-oil ratio (GOR) trends and gas breakthrough timing were observed, prompting further investigation. Detailed analysis of flowmeter and pulsed neutron logging data revealed that tight zones with matrix permeability below 1 mD were contributing to flow. These zones were initially interpreted as mud-dominant facies lacking fractures. However, subsequent core analysis identified karst-related facies such as karst breccia and vadose silt, indicating the presence of HKS. These facies were mapped across multiple wells, enabling spatial definition of karst distribution. By assigning well test KH values to these identified layers, the reservoir model successfully replicated gas front migration and breakthrough timing, resulting in significant improvement in history matching and cumulative production forecasts. This novel integration of geological characterization with Production Logging Tool (PLT) and time-lapse pulsed neutron logging data enhances predictive reliability and provides a robust framework for field development planning in complex carbonate systems.