The passive margin of Offshore Somalia was characterized in a regional study which defined opportunities at the play fairway scale in three sub-basins, the Mid-Somalia High, Mogadishu Deep, and Jubba Deep. These basins stretch for more than 1000 km along the coastline and accumulate up to 12 km of sediment from the opening of a rift basin in the early Jurassic to the establishment of a Cretaceous and Tertiary Passive Margin.
The principal geophysical dataset comprised a 20,000 line-km sparse regional 2D survey acquired in 2014, supplemented by gravity and magnetic data. The potential field datasets had limited application due to signal overprinting by multiple phases of the basement and sediment deformation. Geophysical analysis was supplemented by regional geologic models based on onshore studies in Somalia and in the rift-conjugate margin of Madagascar, where an active petroleum system is well-documented.
Geophysical analysis was critical in characterizing the carbonate fairway on the Mid-Somalia High (MSH), where studies identified three play fairways. The stratigraphy on the MSH is calibrated by a direct tie on the regional data to the well Meregh-1, drilled in 1982, which penetrated more than 2700 m of Jurassic carbonates at the southern end of an epeiric shelf basin extending up to the Arabian Peninsula.
The seismic data were interpreted in time and depth domains and with the aid of some computational seismic attributes used to enhance the imaging of the geology. On a regional scale, vertical trace attributes correlated through the dataset helped to improve geologic interpretation. They enabled the separation of the geologic sequences and correlation with the regional tectonic events in the basin. The computational methods included a review of angle stacks to QC processing, computation of an energy attribute, and spectral decomposition for reservoir and fluid content characterization. Spectral decomposition attributes were particularly effective in highlighting potential reservoir and source intervals, possible gas chimneys, and shallow gas anomalies. These features were also prominent in the Energy attribute.
We conclude that using uncalibrated post-stack seismic attributes in a frontier basin helped to constrain uncertainty in the characterization of the geologic sequences, analysis of petroleum system indicators, and definition of the structural traps. Furthermore, area selection for the planned 3D seismic acquisition was guided by understanding the exploration plays defined on the MSH by this phase of work.
To be presented as a poster 2024 AAPG ICE, Madrid, 6-8 November
Somalia offshore is a passive margin basin with a sedimentary sequence ranging in age from Jurassic to recent. Coastline Exploration holds seven blocks under early-mover PSAs, block areas are 50002 km each. Currently, Coastline Exploration is finalizing a 3D seismic acquisition program.
Register to be pre-screened for Coastline Exploration Dataroom to farm-in the blocks offshore Somalia.