Depositional and post-depositional architectural elements of the Dar es Salaam Platform, central coastal Tanzania: distribution of petroleum system elements and their implications for petroleum prospectivity

The Dar es Salaam Platform (DSP) and Mafia Basin are within the Bigwa-Rufiji-Mafia (BRM) hydrocarbon exploration block of the coastal Tanzania basin. The DSP has made insignificant hydrocarbon discoveries despite some exploration campaigns that involved the acquisition of seismic reflection data and exploration drilling. This study used 2D seismic interpretation techniques and well-log analysis to establish depositional and post-depositional architectural elements of the DSP for the purpose of contributing to the understanding of the petroleum prospectivity of the area. Based on well-log analysis, correlation has been made to the Mafia Basin to assess any spatial variability in depositional conditions and processes, which may be key to understanding the petroleum potential of the DSP. Results show that tectonics, sea level changes, and sediment supply mainly controlled the formation of the DSP. Different tectonic events created hydrocarbon migration pathways from deep buried source rocks to shallow seated reservoirs and formed possible petroleum prospects. The revealed petroleum prospects are fault-controlled and have not been tested by drilling. Some of the prospects have been fractured by subsequent faulting. The faulting of the petroleum prospects within the DSP caused hydrocarbon leakages to be revealed by the mapped gas chimneys. These gas chimneys are reported for the first time in the study area. The hydrocarbon leakage from the DSP prospects may be one of the reasons why the previous exploration campaigns ended with some dry wells.