Discovery of Sandy Beach-Bar and Its Significance on Petroleum Geology Around Ruman Buried Hill of Melut Basin, South Sudan

Abstract

After almost 20 years exploration, only a few structural traps were left for drilling in Melut Basin, South Sudan. Exploration for new areas such as lithological reservoirs is needed to tackle the reserve and production decline. Based on analysis of palaeogeomorphic reconstruction, provenance system, mico-facies in single well, distribution of sandbodies, and investigation of modern deposition in Qinghai Lake, large-scale sandy beach-bars are discovered in Cretaceous Galhak Fm. around Ruman buried-hill in Melut Basin. Two depositional models of buried-hill periphery and underwater buried-hill platform have been built. In the initial stage of Galhak Fm. deposition, Ruman buried hill exposed for a short duration because of intense tilting of faults, where large scale of sandy bar was developed with an area of 10 km2 and a thickness 10-20m, the sediment source was provided by basement and long-axis delta. Ruman burial hill was sinking into the water as the relative lake level rising, sandy beach-bars of underwater buried hill platform (dominated by large area of thin layer beach-sand with thick bar-sand in local) was developed, the sediments source was supplied by long-axis delta. Sandbodies of beach-bar, up-dipping pinched-out boundary, underlying source rock of Renk Fm., flooding mudstone in the top and lateral lacustrine mudstone seal were matched to form lithological traps. The discovery of sandy beach-bar guided the lithological reservoir exploration effectively, several exploratory wells that were deployed on the basis of “beach bar” were succeeded, promoting the reserve scale of Ruman area.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018