Burial Diagenesis and Thermal Maturity Evaluation of The North West Muglad Rift Basin, Sudan

By

 Osman M. Abdullatif¹

(1) KFUPM, Dhahran 31261, Saudi Arabia

 This study evaluates and compares the state of organic maturity and oil generation in the northwestern part of the Muglad rift basin of interior Sudan. Different maturity indices were utilized such as the percentage of the expandable smectite layers, the measured organic maturity ( vitrinite reflectance, Rock-Eval pyrolysis) and the predicted maturity from the time-temperature (TTI) modeling. The rift basin facies consists of non-marine cyclic sequences of lacustrine and fluvial/alluvial facies of early Cretaceous to late Tertiary age.

The thermal maturity evaluation indicated progressive smectite conversion with the increase of depth and temperature, where the percentage of smectite layers ranges from 35% to 75%. The smectite layers decrease with the increase in both observed and predicted maturities . Significant illitization is associated with the early Cretaceous facies of Abu Gabra and Sharaf Formations. These same formations are indicated by both observed and predicted maturity indices as mature potential source rocks. Whereas the largely immature late Cretaceous and Tertiary facies showed insignificant illitization. This indicates the close relationship between smectite illitization and temperature- related changes in the organic matter maturity. The variation of smectite illitization along the burial profiles may indicate the effect of various controls on burial diagenesis such as temperature, potassium availability, inhibitor ions, permeability, smectite composition, kinetics and time. The TTI modeling indicated that the oil generating strata are the Aptain/Albian Abu Gabra Formation and the timing of oil generation began in the Oligocene and continued to present time