A COMPARATIVE STUDY BETWEENWATER SATURATION MODELS in RESERVOIR EVALUATION FROM HEGLIG OIL FIELD, MUGLAD BASIN, SUDAN

Abstract

The Muglad Basin is a large rift basin located in south Sudan. This basin is characterized by sedimentary section of non-marine clastic sequences of Jurassic (?)-Cretaceous and Tertiary age. A high numbered of drilled wells and geophysical work is located in this basin, where the most significant oil discoveries, Unity and Heglig filed. This study has been carried out in Heglig Field. This study explains the values of formation evaluation on Heglig Field, and explains its important in reserve estimation of oil in this area. Petrophysical interpretations have been done on the previous log data of selected productive wells drilled in the study area, focusing on Bentiu Formation. From interpretations, reservoir properties such as porosity, permeability and water saturation have been determined. Archie, Indonesian, Dual water, and Simandoux equations were used to calculate water saturation, which influence oil reserve estimation. Comparisons between the values of water saturations have been done. Different models illustrate those differences. The comparison shows differences in oil content found in the same formation and shows that Dual water equation for water saturation calculation is the best equation to be used in shaly-sand oil bearing formation as Bentiu Formation in this study filed.