Wilson, Kerri L.1, Alex G. Blacque1, Alan G. Collins1
(1) Robertson Research International, Llandudno, United Kingdom
ABSTRACT: The Petroleum Prospectivity of the Melut Rift Basin, Sudan
Dextral transcurrent movement along the reactivated Pan-African Central African Shear Zone was the driving force for rifting in the Cretaceous – Tertiary Melut Basin and other rift basins in Sudan. Dextral movement along the shear zone is expressed as NE-SW extension forming NW-SE to N-S trending rift basins. In the Melut Basin, the main rifting phase was during Late Cretaceous times although a phase of Early Cretaceous rifting may have occurred. Basin inversion in the Eocene and Early Oligocene was possibly associated with Tertiary igneous activity in neighbouring Ethiopia. Geophysical evidence suggests up to 12km of Cretaceous and Tertiary sediments.
Although the basin is only partially explored, the Adar-Yale field and recent oil discoveries indicate the existence of a significant active petroleum system. Source rock correlation however is not conclusive. Candidate source rocks are: 1. Lower Cretaceous - analogues of the Muglad Basin (probably over mature). 2. Upper Cretaceous Melut Formation - hints of source rock quality identified in Adar 1. 3. Tertiary Jimidi & Miadol Formations - some source indications (probably immature). These all comprise siltstone and clays interbedded with sands, which probably thicken and increase in importance towards depocentres as lacustrine Type I/II kerogens. Paleocene reservoirs consist of braided fluvial and lacustrine deltaic channel sands. Geometries are hard to predict, as sand thicknesses are below seismic resolution. Shales are found throughout the stratigraphic sequence and either overlie or interdigitate with reservoirs providing overlying and intraformational seals. Significant remaining potential is envisaged with many undrilled prospects.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.