Paper submitted to EAGE Annual 2026
Summary
Several source rock intervals have been proven across the MSGBC offshore basins, when considering exploration boreholes, DSDP wells, seafloor cores and coastline seeps. Most of them are particularly close to the palaeo-shelf edge where bypass systems connect proximal plays with the deeper basin domain.
Methods such as satellite seep detection provide strong evidence for an active petroleum system, while basin modelling based solely on structural interpretation can offer a reasonable first-order assessment of thermal evolution. Operators with access to exploration well data, specifically temperature and fluid measurements, also benefit from critical calibration points that strengthen these models.
The real advantage of multibeam and seafloor sampling campaigns (MB&SS), however, lies in the targeted acquisition of hydrocarbon samples directly from live or palaeo seeps, often far from existing exploration wells. The resulting 3D temperature, burial-history, and maturation model is therefore calibrated using measured geochemical and heat flow data, elevating the model far beyond a hypothetical reconstruction. Because heat flow measurements at the present-day seabed, together with borehole temperature profiles, must align with model predictions, the integrated MB&SS and seismic approach yields a near–real-time representation of subsurface maturity conditions. These models are therefore driven by measured geophysical data rather than purely conceptual rift-history assumptions, as this study will show case.
Furthermore, geochemical characteristics of oil and gas families, biomarker characteristics, and maturation ages provide an additional suite of constraints. These data must reconcile with the stratigraphic framework, burial history, and predicted source rock maturity through time. Minimum migration timing from reservoir to seabed also imposes strict temporal limits. Collectively, these constraints narrow the range of viable charge scenarios and allow elimination of options that do not satisfy the observations from the full geophysical and geochemical dataset. As a result, predictions of which source rocks (and their modelled timing of expulsion) may have contributed to specific discoveries become non-unique but tightly bounded, even in the absence of exploration wells.
Achieving this level of confidence, however, depends on acquiring a sufficiently large number of high-quality geochemical samples to enable robust biomarker and kerogen analyses. These measurements are factual and non-negotiable; any mismatch with the model forces a return to the interpretation workflow.