Integrated Multi-Physics Approach for Synthetic Core Derivation and Water Influx Mitigation Using 3D Far Field Sonic in Offshore Carbonate Reservoir
Authors: Saleh Khaled , Hegazy Amr , Hakim Emad Abdel , Patro Radhika , Hussain Syed Aaquib , Galal Mahmoud , Sinha Mrinal 
Published: November 2024

Interpreting older-generation coarse-resolution seismic data posed challenges in accurately assessing the subsurface in the presence of highly high-velocity layers. Significant variations in production rates were noted among key wells drilled in the Field under study, based solely on seismic. Despite substantial water influx, saturation analysis behind the casing indicated good hydrocarbon saturation. Unraveling the heterogeneity of these complex carbonate formations and identifying the source of water influx was critical for field development planning.

High-resolution image data and spectroscopy results were integrated with seismic data to refine the understanding of the sub-surface. Synthetic cores were created utilizing image data and spectroscopy results, and they were later used to define litho-facies differentiation across the field. Based on the synthetic cores, lithological distributions of cherty, dolomitic, and argillaceous limestone were done for the Field under study. In addition to spectroscopy analysis, Pulsed Neutron Capture data also aided in saturation analysis behind casing based on carbon-oxygen ratio and provided insights on fluid contacts. 3D far-field imaging was relied upon for understanding the presence of laterally extensive fractures with their location and orientation.

Sub-surface reclassification for the Field under study was done based on the generated litho-facies and synthetic cores. It was observed that wells drilled in dolomitic limestone areas had the most prolific hydrocarbon potential, while the argillaceous limestone had the least hydrocarbon potential. Integrating the 3D far field with other petrophysical logs revealed critical insights into the reservoir's structure and composition. 3D Far Field imaging identified extensive natural fractures that cross the oil-water contact, suggesting larger connected reservoir compartments than previously understood. Information on the presence of laterally extensive fractures contributing to water influx was critical in optimizing the completion and perforation strategies.

This lithological mapping has been instrumental in directing drilling operations toward zones with higher hydrocarbon yields and better reservoir properties. Based on these findings, the targeted approach has led to optimized drilling trajectories, improved oil recovery, and reduced water production. These outcomes demonstrate the effectiveness of combining these technologies and underscore their potential to transform traditional reservoir management practices by providing a more accurate and dynamic understanding of subsurface conditions.

This paper presents an innovative approach to redefining the subsurface by combining seismic, imaging, and spectroscopy findings—improved classification of the heterogeneous carbonate formations based on synthetic core aided in targeting optimal locations. Leveraging the 3D far-field imaging facilitated the mapping of extensive fracture networks and the development of the best completion and perforation strategy to boost production and prolong water cut delays. This approach significantly enhances the oil recovery process's predictive accuracy and operational efficiency.