Maturation history modeling of Sufyan Depression, northwest Muglad Basin, Sudan

•The present heat flow map of Sufyan Depression is drawn based on 13 wells.•The heal flow history of Sufyan Depression is predicted.•The Ro (%) history of AG source rocks is simulated.•The Ro (%) maps of AG-2_down and AG-3_up source rocks are completed and the results match the present oil shows.

The Sufyan Depression is located in the northwest of Muglad Basin and is considered as a favorable exploration area by both previous studies and present oil shows. In this study, 16 wells are used or referred, the burial history model was built with new seismic, logging and well data, and the thermal maturity (Ro, %) of proved AG source rocks was predicted based on heat flow calculation and EASY %Ro modeling. The results show that the present heat flow range is 36 mW/m2∼50 mW/m2 (average 39 mW/m2) in 13 wells and 15 mW/m2∼55 mW/m2 in the whole depression. Accordingly, the geothermal gradient is 20 °C/km∼26 °C/km and 12 °C/km∼30 °C/km, respectively. The paleo-heat flow has three peaks, namely AG-3 period, lower Bentiu period and Early Paleogene, with the value decreases from the first to the last, which is corresponding to the tectonic evolution history. Corresponding to the heat flow distribution feature, the AG source rocks become mature earlier and have higher present marurity in the south area. For AG-2_down and AG-3_up source rocks that are proved to be good-excellent, most of them are mature with Ro as 0.5%–1.1%. But they can only generate plentiful oil and gas to charge reservoirs in the middle and south areas where their Ro is within 0.7%–1.1%, which is consistent with the present oil shows. Besides, the oil shows from AG-2_down reservoir in the middle area of the Sufyan Depression are believed to be contributed by the underlying AG-3_up source rock or the source rocks in the south area.