Structural analysis of seismic data, combined with well data, provides information for hydrocarbon exploration in a prospective basin. These techniques have been employed in the offshore Lamu Basin to characterize str...Structural analysis of seismic data, combined with well data, provides information for hydrocarbon exploration in a prospective basin. These techniques have been employed in the offshore Lamu Basin to characterize structural and stratigraphic setting of carbonate reefs and assess structural deformation and its effect on trapping mechanisms in the offshore basin. Structural interpretation was based on seismic and well data. A combination of microfossil, nannofossil and palynomorph data provided broad age-control for the stratigraphic interpretations. Seismic amplitude brightening attribute was used for tracing structural continuity. Faulted anticlinal traps were formed in the Upper Cretaceous and Tertiary periods. There are inversion features with recent extensional faulting. Favourable structural traps are in the near coastal region. The carbonate reefs in the offshore basin are interpreted from the Early Paleocene to Miocene periods. These reefs formed in the near coastal region, are likely to be quality traps/reservoirs for hydrocarbon accumulation. Five main structures are identified from the depth seismic maps for the Early Paleocene, Late Paleocene and Early Miocene. The reef front may have subsided early, the overlying shales offering the sealing mechanisms. The Davie-Walu transformation was likely to affect the trapping mechanism in the central and southern regions of offshore Lamu Basin. The study provides better understanding of the carbonate reefs’ hydrocarbon potential and trapping mechanisms in the offshore basin.展开更多
Fluid inclusion signal strength and visual inclusion abundance are generally lower along migration pathways than in charged reservoirs from the same area. A zone that displays strong fluid inclusion stratigraphy (FIS)...Fluid inclusion signal strength and visual inclusion abundance are generally lower along migration pathways than in charged reservoirs from the same area. A zone that displays strong fluid inclusion stratigraphy (FIS) hydrocarbon indications and high visualized petroleum inclusion abundance, indicates paleo-charge or in some cases a migration pathway, e.g, where inclusion abundance is enhanced by extensive microfracturing. In this study, fluid inclusion data are interpreted in seven offshore wells of the Lamu Basin to enhance the understanding of hydrocarbon generation, migration and migration pathways. The study also examines the interrelationship among rock texture, rock composition and trapped fluid distribution in the study area. The studies were based on FIS analyzed data courtesy of Fluid Inclusion Technologies (FIT) Inc. in USA laboratories. FIT conducted analysis on 391 samples from the Paleocene to Upper Jurassic (Kiboko-1 well), 249 from the Paleoecene to Campanian (Kubwa-1 well), 106 from the Maastrichtian to Turonian (Mbawa-1 well), 59 from the Eocene to Campanian (Pomboo-1 well), 26 form the Lower Eocene to Maastrichtian (Simba-1 well), 16 from the Eocene to Maastrichtian (Kipini-1 well) and 11 from the Maastrichtian to Campanian (Kofia-1 well). It also made analysis on sidewall core sample plates, with 44 from the Maastrichtian to Campanian (Kubwa-1 well), 108 from the Campanian to Upper Jurassic (Kiboko-1 well) and 8 from the Campanian (Pomboo-1 well) for petrographic evaluation. For photomicroscopy, thin sections were examined under a petrographic microscope using Ultra Violet (UV) fluorescence and microthermometry, in order to verify the presence of petroleum bearing inclusions in the rock samples and to explore textural relationships that may yield additional information on the timing of hydrocarbon migration or generation. Gas shows in Mbawa-1 well is a result of generated hydrocarbons from the carbonate interbeds in the Upper Cretaceous. Gas shows are pockets trapped in the thin carbonate rich beds. There is low abundance of upper-low, moderate and upper-moderate gravity liquid petroleum inclusions in Kubwa-1 well (central deep offshore). The low abundance suggests migration events rather than paleo-accumulations, possibly involving several discrete charges. Despite sufficient vitrinite reflectance and total organic carbon (TOC) content, the temperatures are still insufficient for hydrocarbon generation in the southern deep offshore in the region where Kiboko-1 well is located. There is no sufficient evidence for access to mature source rocks in the deep offshore basin.展开更多
文摘Structural analysis of seismic data, combined with well data, provides information for hydrocarbon exploration in a prospective basin. These techniques have been employed in the offshore Lamu Basin to characterize structural and stratigraphic setting of carbonate reefs and assess structural deformation and its effect on trapping mechanisms in the offshore basin. Structural interpretation was based on seismic and well data. A combination of microfossil, nannofossil and palynomorph data provided broad age-control for the stratigraphic interpretations. Seismic amplitude brightening attribute was used for tracing structural continuity. Faulted anticlinal traps were formed in the Upper Cretaceous and Tertiary periods. There are inversion features with recent extensional faulting. Favourable structural traps are in the near coastal region. The carbonate reefs in the offshore basin are interpreted from the Early Paleocene to Miocene periods. These reefs formed in the near coastal region, are likely to be quality traps/reservoirs for hydrocarbon accumulation. Five main structures are identified from the depth seismic maps for the Early Paleocene, Late Paleocene and Early Miocene. The reef front may have subsided early, the overlying shales offering the sealing mechanisms. The Davie-Walu transformation was likely to affect the trapping mechanism in the central and southern regions of offshore Lamu Basin. The study provides better understanding of the carbonate reefs’ hydrocarbon potential and trapping mechanisms in the offshore basin.
文摘Fluid inclusion signal strength and visual inclusion abundance are generally lower along migration pathways than in charged reservoirs from the same area. A zone that displays strong fluid inclusion stratigraphy (FIS) hydrocarbon indications and high visualized petroleum inclusion abundance, indicates paleo-charge or in some cases a migration pathway, e.g, where inclusion abundance is enhanced by extensive microfracturing. In this study, fluid inclusion data are interpreted in seven offshore wells of the Lamu Basin to enhance the understanding of hydrocarbon generation, migration and migration pathways. The study also examines the interrelationship among rock texture, rock composition and trapped fluid distribution in the study area. The studies were based on FIS analyzed data courtesy of Fluid Inclusion Technologies (FIT) Inc. in USA laboratories. FIT conducted analysis on 391 samples from the Paleocene to Upper Jurassic (Kiboko-1 well), 249 from the Paleoecene to Campanian (Kubwa-1 well), 106 from the Maastrichtian to Turonian (Mbawa-1 well), 59 from the Eocene to Campanian (Pomboo-1 well), 26 form the Lower Eocene to Maastrichtian (Simba-1 well), 16 from the Eocene to Maastrichtian (Kipini-1 well) and 11 from the Maastrichtian to Campanian (Kofia-1 well). It also made analysis on sidewall core sample plates, with 44 from the Maastrichtian to Campanian (Kubwa-1 well), 108 from the Campanian to Upper Jurassic (Kiboko-1 well) and 8 from the Campanian (Pomboo-1 well) for petrographic evaluation. For photomicroscopy, thin sections were examined under a petrographic microscope using Ultra Violet (UV) fluorescence and microthermometry, in order to verify the presence of petroleum bearing inclusions in the rock samples and to explore textural relationships that may yield additional information on the timing of hydrocarbon migration or generation. Gas shows in Mbawa-1 well is a result of generated hydrocarbons from the carbonate interbeds in the Upper Cretaceous. Gas shows are pockets trapped in the thin carbonate rich beds. There is low abundance of upper-low, moderate and upper-moderate gravity liquid petroleum inclusions in Kubwa-1 well (central deep offshore). The low abundance suggests migration events rather than paleo-accumulations, possibly involving several discrete charges. Despite sufficient vitrinite reflectance and total organic carbon (TOC) content, the temperatures are still insufficient for hydrocarbon generation in the southern deep offshore in the region where Kiboko-1 well is located. There is no sufficient evidence for access to mature source rocks in the deep offshore basin.
