Characterization of Fractured Basement Reservoir, Melut basin, Southeast Sudan

Basement reservoirs can be of different types; fractured granitic, fractured quartzite, and/ or fractured Schist and Gneiss. In the fractured basement reservoirs, hydrocarbon is entrapped within the fractures network within the basement rocks. Porosity and permeability in basement reservoirs is controlled by the fractures and not by the rocks matrix as in the conventional reservoirs. Hydrocarbon-hosted in fractured basement reservoir was reported in many locations in Sudan since 2007 and the Melutbasin is one of those areas. Mapping and characterization of faults and fractures in those areas are important steps towards the quantification of hydrocarbon potentiality in the region. The main objective of this study is to characterize and model fractures system within the basement reservoir in Ruman area, Melut basin. The aim of this study is to better understand those fractures origin, distribution and connectivity. To achieve the goal of this study fractures, faults and lineaments were studied in different scales and from surface and subsurface data; well data, gravity, seismic data and satellite images. Obtained data was characterized base on orientation, length and intensity. Moreover; geostatistical extrapolation for areas in-between wells, stochastic and deterministic models were also conducted to determine the Discrete Fracture Network (DFN) model. Areas of fractures concentration and distribution were delineated using this technique. Compatible and parallel NW-SE, NNW-SSE to N-S, WNW- ESE to E-W and NE-SW trends were observed from the interpreted data of satellite images, gravity, wells and seismic data. It is evident from Rose-Diagrams generated for the faults detected from seismic data and fractures observed from the FMI-log of five wells that they are having similar trends. The same trends can also be noticed in gravity data and lineaments determined from satellite images. Three stages model were proposed for the origin of the fractures associated with the basement; fractures developed during the emplacement and cooling of the igneous pluton, fractures related to the Proterozoic tectonic events and faults related fractures (developed during Melut basin rifting).The outcome of this study delineated the possible origins of the fractures system hosting hydrocarbon in the basement rocks. Additionally the study characterized and defined the possible trends of those fractures and how are they related to different origin. The study also addressed the possible role of the major faults in hydrocarbon migration. From the in-situ stress analysis, faults and fractures trends were tested for the most susceptible at present day. The study outcomes and methodology can be used for hydrocarbon exploration and development in this area and for other areas of similar geological structural settings.