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AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain

Downthrown Trap Infill Analysis, Case Study from Melut Basin Sudan

Izzeldin Z. Abdelrahim1

(1) Exploration, PDOC, Khartoum, Sudan.

Melut basin is early to late cretaceous rift basin covered by thick sequence of non-marine sediments, which vary in age from Cretaceous to Tertiary. Exploration results have indicated proven hydrocarbon system in both Tertiary and Cretaceous sections. This petroleum system has a perfect assemblage of source, reservoir and top seal. The source is the Cretaceous lacustrine shale of Galhak Formation. The reservoir is the braided stream sandstones of Yabus formation, and the top seal is the fluvial shale of Adar formation.

The majority of trap style in Melut basin are structural faulted block requiring fault seal on one or more bounding faults. There fore the lateral seal play as a critical role to assess the trap infill probability.

In exploration context the challenge is to adopt role that the fault either connect juxtaposed reservoirs or make a side barrier, prevent escape of hydrocarbon from lower structure. Effective fault seal model analysis and calibration depend on the quality of available data.

The methodology applied in the analysis of fault seal potentiality in Melut basin encompasses, identifying reservoir juxtaposition areas over the fault surface; using the mapped horizons and refined reservoir stratigraphy defined by isochors at the fault surface; and deriving an empirical relationship between rock type and fault displacement to assess the likely hood of sealing fault rocks being developed. Shale thickness and amount of displacement play an important role to estimate SGR in the fault zone. Buoyancy pressure profiles are used examination to identify which data analysis techniques and seal-failure criteria best predict the observed hydrocarbon contacts in a given area. They can also be used to verify the threshold shale gouge ratio values that represent the onset of fault sealing. Results from hydrocarbon test of drilled well multiple provide a means for adopting same way of analysis and therefore lead to improved prospect risking