Study on Sedimentary Microfacies in Bara Area, Muglad Basin, Sudan

Abstract

The Muglad basin is a Cretaceous rift basin located in Sudan, developing three sag-rift cycles. The Fula sub-basin is located at the northeast of the basin, mostly extending in nearly NS. And the Bara area is located at the south part of the western steep slope of the Fula sub-basin. However, there are various views on the sedimentary facies of Abu Gabra (AG) formation in this area. For example, some researchers believe that it develops underwater fans, supplied by Babanusa High which is located at the west of Fula sub-basin; other researchers reveals that there is no source supply in this area, whose sedimentary environment is shallow lacustrine. Therefore, further studies should be conducted on the distribution of sedimentary microfacies and the subdivision of the fourth-order sequences.

In this study, we mainly focused on AG2 member of the Bara 3D area, using seismic, well logging and core data to carry out the fourth-order sequence subdivision, single well facies identification, and lateral distribution features of the gross content of sandstone and sedimentary microfacies. It was considered that the AG2 member in Bara area could be subdivided into 4 sequences, i.e. SQ4-1, SQ4-2, SQ4-3 and SQ4-4. On the basis of the identification of typical sedimentary facies, the single well facies division was carried out, and the shoal facies and shallow lacustrine facies were identified. Lateral distribution features of the gross content of sandstone and sedimentary microfacies of each layers of AG2 member in the Bara area were worked out, finding that the sand body in AG2 member was mainly distributed in SQ4-2, and from SQ4-1 to SQ4-4, the thickness of sand varied from thin to thick and finally to thin. Different from the previous understanding, Babanusa High should be at the lower part in the AG stage, so there was no near source supply.

During this study, the distributive characteristics of AG2 microfacies were described by dividing AG2 member into 4 fourth-order sequences. It revealed that there was no supply in the Bara area, which was mainly deposited by monsoonal flat sedimentary facies, distributed along the western boundary. In addition, there are shallow lacustrine deposits, distributed separately in the northeast and southeast.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018