PETROLEUM GEOLOGY OF THE FULA SUB-BASIN, MUGLAD BASIN, SUDAN

Dou Lirong1*, Cheng Dingsheng2, Li Zhi2, Zhang Zhiwei2 and Wang Jingchun1

1 China National Oil and Gas Exploration & Development Corporation. No. 6-1, Fuchengmen Beidajie, Xicheng District, Beijing 100034, P. R. China.

2 African Department, Research Institute of Petroleum Exploration and Development, PetroChina, Xueyuan Road 20, Haidian District, Beijing 100083, P. R. China.

* Corresponding author, email: doulirong@cnpcint.com

The Fula sub-basin is a fault-bounded depression located in the NE of the Muglad Basin, Sudan, and covers an area of about 3560 km2. Eleven oilfields and oil-bearing structures have been discovered in the sub-basin. The Lower Cretaceous Abu Gabra shales (Barremian Aptian), deposited in a deep-water lacustrine environment, are major source rocks. Reservoir targets include interbedded sandstones within the Abu Gabra Formation and sandstones in the overlying Bentiu and Aradeiba Formations (Albian Cenomanian and Turonian, respectively).

Oil-source correlation indicates that crude oils in the Aradeiba and Bentiu Formations are characterized by low APIs (<22), low sulphur contents (<0.2%), high viscosity and high Total Acid Number (TAN: >6 mg KOH/g oil on average). By contrast, API, viscosity and TAN for oils in the Abu Gabra Formation vary widely. These differences indicate that oil migration and accumulation in the Fula sub-basin is more complicated than in other parts of the Muglad Basin, probably as a result of regional transtension and inversion during the Late Cretaceous and Tertiary.

The Aradeiba-Bentiu and Abu Gabra Formations form separate exploration targets in the Fula sub-basin. Four play fairways are identified: the central oblique anticline zone, boundary fault zone, fault terrance zone and sag zone. The most prospective locations are probably located in the central oblique anticline zone.

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