Asiadi Mrutu

Asiadi Mrutu

Senior Exploration Geophysicist

Tanzania Petroleum Development Corporation


SESSION 2:  Hydrocarbon Potential for TPDC Blocks 4/1B and 4/1C Offshore Southern Tanzania

Under new Petroleum Act, 2015, TPDC is currently operating as National Oil Company with mandate to conduct petroleum reconnaissance, exploration, development and carrying out specialized operations in the petroleum value chain in Tanzania. Through the Government Notice (GN 184) published on 20th May,2016, the Ministry of Energy and Mineral exclusively reserved Blocks 4/1B and 4/1C for National Oil Company (TPDC). The two Blocks located in Southern Tanzania bordering to the south by Mozambican Blocks which is estimated to have total of about 200TCF natural gas discovery and to the North and Western side bordering Blocks 1, 2, 3 and 4  with total estimated resource of about 47.13TCF gas discovery. Blocks 4/1B and 4/1C are covered by 2682 Line Kilometre sparse 2D seismic data processed on both Pre-Stack Time Migration and Pre-Stack Depth Migration. These includes 802 Line Kilometre acquired and processed by Western- Geco and 1880 Line Kilometre Acquired and processed by GX Technology. TPDC is planning to acquire 4058km (3km x 3km grid) infill 2D seismic survey over the two Blocks with the objective to increase understanding in terms of hydrocarbon potential and locate the future drillable prospect. TPDC will then farm out some of its share interest to strategic partner from which they will operate together to develop these two Blocks.

Along East African margin, the existing recent discoveries are located in the water depth less than 2000m, which gives indication that there are working petroleum system in the region i.e. mature source rock and presence of reservoir rocks. The detail studies conducted using 2D seismic interpretation approach aiming to identify and map any possible areas with plays and prospect for future hydrocarbon exploration. The literature review suggesting that, the petroleum systems along the region are closely linked to Karoo continental rifting phase during Permian to Early Jurassic, and to a subsequent passive margin setting. The tectonic setting was closely linked to the Gondwanaland break-up during Permo-Triassic period. Four mega-sequences have been identified i.e. Pre-rift phase (Karoo phase), Syn-Rift Phase, Post-Rift phase and recent East African Rift System. The sequence boundaries were used to control the extrapolation for the reservoirs from nearby discoveries. The extrapolation for the reservoirs is supported by the clear evidence that, the deposition for Ruvuma Channel extends to the deeper part offshore southern Tanzania bypassing Davie Ridge Fracture Zone.

In this study the stratigraphic and structural model were integrated with the extrapolated reservoir rocks and used to define the sub-surface geological model. This model was used as the bases for plays and prospects mapping from which nine prospects were mapped followed by producing detail structural contour map for each prospect. Initial results indicating that the two Blocks are highly prospective with the prospect mapped with large volumes compared to the surrounding gas field.