Isotope Logging: A Case Study of Integration with Borehole Geology

Summary Isotope logging has been used regularly as advanced mud-logging services; however, it has not been often integrated with other while-drilling data, such as borehole images to characterize the sub-surface. Real-time δ13C1 Isotope logging service has been used as a formation evaluation tool and its capability of providing stable and high-resolution data under difficult conditions on an offshore drilling site becomes more important for realtime decision making while integrating with logging-while-drilling (LWD) data. This case study comes from the Sabah Basin, located on the North western continental margin of offshore Malaysia. The hydrocarbon reservoirs in the Sabah Basin are predominantly siliciclastic. This basin is subdivided into provinces that are characterized by distinct structural styles and sedimentation histories. Seismic investigation of study-area showed that’s it is complexly faulted and the compartmentalization is perceived as a recovery risk, including suspected sub-seismic fault population. Real-time δ13C-C1 Isotope logging service proved to be a cost-effective qualitative tool to understand the sub-seismic faulting of the reservoir. Integrating this data with borehole images confirmed various degrees of subsurface compartmentalization and provided verification and increased interpretation confidence.