Fault and Unconventional Traps Identification Of Galhak IV in Palouge Area - Melut basin, South Sudan

Abstract

Abstract The Melut Basin is the largest rift basin discovered in Sudan. It trends sequence buried by a Miocene-Recent post-rift sedimentary cover. These continental sediments comprise fluvial and lacustrine facies. Still there are some areas at Melut basin need to be investigated such as Galhak Formation. It is very complicated due to reservoir discontinuity that caused by imbedded clay lenses and the existence of structure complication (manly faults). In this study the area of interest is Palouge area located in Block 3/7 Melut Basin in the south of Sudan. The used data sets was Geophysical Data, (3D seismic cube and wells data) . At present 99.2% of geological reserves of this area centralize in Yabus and Samaa formations which are the main force oil- layers of Paleocene in Northern Sub-sag of Melut Basin. In this study the identification of faults was not only based on their individual fault characters and time slice as a normal techniques, but also utilized advanced techniques such as geo-feature mapping and seismic sections interpretation to scan the distribution of faults throughout the 3D seismic . These techniques were carried out to enhance the fault interpretation of the target area and to help in the interpretation of the minor faults, which can hardly be identified using conventional method. Several structural patterns were delineating during the 3D seismic section interpretation which lead to create seismic structural maps (TWT structural maps) for Galhak IV Formation top and base. These produced maps provide a reliable evaluation of the general structural characteristics of the Palouge area using faults map and structural style. Types of seismic attributes contraction and analysis to determine layered sand shale. applied the results of structure interpretation discovered three structural-lithologic traps and three lithologic traps. Structural traps are formed by tectonic forces after the sedimentary rocks have been deposited. They generally fall into two categories: anticlines, where the rock has been folded or bent upward, and faults, where movement along a joint or fracture has driven an impermeable layer above a permeable layer. Stratigraphic traps are formed as a result of lateral and vertical variations in the thickness, texture, porosity or lithology of the reservoir rock at the time of sediments are deposited. They fall into three categories: pinchouts, unconformities, carbonate reefs fossilized coral constructions and associated deposits.