How Structural Segmentation Shapes Petroleum‐System Efficiency in a Transform‐Modified Rift: Insights From the Saltpond Basin (Offshore Ghana), Equatorial Atlantic Margin

ABSTRACT

Rifts host a substantial proportion of the world's hydrocarbon resources because lithospheric extension commonly generates sustained subsidence, thick sedimentary fills and laterally connected migration systems that enhance petroleum‐system efficiency. In transform‐modified rifts, where extension occurs along or adjacent to transform continental margins, the interaction between rifting and transform processes produces oblique deformation and pronounced structural segmentation, partitioning basins into discrete, fault‐bounded depocentres with limited lateral connectivity. However, how such segmentation controls petroleum‐system efficiency from source‐rock burial and maturation through migration to trap effectiveness remains poorly constrained. Using the Saltpond Basin (offshore Ghana) as a case study, this study integrates published structural interpretations, stratigraphic frameworks, well data and geochemical datasets to evaluate how structural segmentation influences petroleum‐system efficiency. The basin is characterized by segmented fault architecture and spatially variable subsidence, which together produce uneven burial histories and thermal maturity across structurally defined compartments. These conditions limit source‐rock maturation, restrict migration pathways and reduce reservoir–seal connectivity, resulting in compartmentalized petroleum systems. Biomarker evidence further indicates heterogeneous hydrocarbon compositions consistent with localized generation and restricted migration, confirming limited system integration. Comparison with other Atlantic‐margin basins, including rift‐dominated systems such as the Tano Basin and transform‐influenced margins such as the St. Paul Basin and Demerara Plateau, shows that such characteristics are typical of transform‐influenced extensional systems, but contrast with more efficient, laterally connected petroleum systems in fully developed rift basins. These findings demonstrate that structural segmentation and subsidence variability exert a first‐order control on petroleum‐system efficiency, by partitioning basins into fault‐bounded depocentres, generating spatially variable burial and thermal maturity and restricting migration pathways and reservoir–seal connectivity and provide a transferable framework for evaluating hydrocarbon prospectivity in transform‐modified rifts.