Overcoming Heterogeneity Challenges in Globigerina Limestone Using Pre-Stack Seismic Inversion: A Pre-Drill Strategy from the Madura Strait, North East Java Basin

Abstract

The DK Field is a key future gas producer supporting regional energy security in Java Island, Indonesia. Located in the Madura Strait, North East Java Basin, it contains the Pliocene Globigerina Limestone as the primary reservoir. Its heterogeneity, comprising eight rock types with complex lateral and vertical variations, increases subsurface uncertainty. Building on previous campaign success, this study applies pre-stack seismic inversion approach to identify sweet spots and optimize pre-drill strategies to enhance field development. Pre-stack seismic inversion was conducted by integrating 3D pre-stack seismic data with well log calibration to generate acoustic impedance, shear impedance, density, and Vp/Vs volumes. These attributes, combined into K-Rho, validated through rock-physics crossplot and calibrated with well-based rock physics parameter to provide consistency between log-derived properties and rock type classification at well. This calibration enabled extrapolation of rock type into the seismic domain, which enables rock-type classification mapping to support reservoir property distribution process in geological modeling. This study employs pre-stack seismic inversion as an effective approach to distinguish gas-bearing from non-productive intervals in the Globigerina Limestone, providing guidance for well trajectory design toward optimal reservoir sweet spot. The inversion results show strong correlation with porosity and fluid content, while rock physics crossplot successfully classify reservoir quality (poor-medium - excellent) and reveal laterally continuous sweet spots. Integration of seismic attributes with well calibration indicates that high-quality zones are generally associated with low acoustic impedance and low density, reflecting higher porosity and gas saturation. The results indicate the most favorable reservoir properties toward the northwest and southeast, where two development wells are optimally targeted to maximize gas recovery. This integrated approach enhances reservoir characterization and provides a robust framework for reducing development risk and refining pre-drill strategies. The integration reduced subsurface uncertainty and support informed decision-making in development well targeting. Moreover, the workflow can be applied to similar carbonate settings.