Many of Sudan’s large oil fields suffer from low recovery factors and decline in primary production due to low oil gravity (<22 API) and viscosities above 100 cP. Many wells experienced premature water production. As such, Enhanced Oil Recovery project seems to be the option to improve oil recovery in Sudan.

Thar Jath field contains in excess of 1.2 billion STOIIP, 75% of the STOIIP comprises 20° API oil with 120–160 cP viscosity while the remaining STOIIP comprises 16° API with viscosity > 680 cP viscosity. The Full Field Review which was carried out through 2009 recognized that primary and secondary recovery could only recover, at best, 9.0% of the STOIIP with infill drilling. As such, a considerable number of Enhanced Oil Recovery (EOR) techniques have been assessed in order to recommend suitable EOR development project for the field, and to position the field as leading the way in Sudan. In the absence of a miscible gas option, dynamic reservoir simulation schemes were developed for the natural depletion, water flood, chemical, thermal and immiscible gas methods.

The three most promising techniques; ASP, steam flood/CSS and in-situ combustion were developed to optimize pattern spacing, injection rates and pressures for each technique. Thereafter, facilities schemes and notional costs were developed so that economic viability could be assessed to select the most preferred technique going forward. EOR has been found to be economically and technically feasible with highest economic recovery across all reservoirs from Steam technique. There is scope for thermal recovery to take recovery factor above 40% overall. The pilot test design study is on going with the objective to proof the concept and confirm scope of recovery from steam flooding prior to full field implementation.

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