The Challenges of Shaly Sand Petrophysics and Formation Evaluations: Case Study Keyi Main Oil Field, Block 6, Sudan

Abstract

The study area located in Keyi Main Oil Field of southern part of western escarpment trend of Fula sub-basin, Block-6, Muglad basin in Sudan. Conventional logging data from wells, Keyi-4, Keyi-11, and dipole shear sonic data (XMAC) of Keyi-12, have been studied. The ultimate goal of this research is to verify an accurate lithology, mineralogy, porosity, permeability and water saturation derived from Indonesian and dual water models of Ghazal and Zarga Formations. Another aim is to overcome the challenges associated with gamma ray log (radioactive effect of potassium), thus identify reasonable shale content and clay type. The methodology and workflow used for this work consists of three steps: logs analysis, core analysis and dynamic elastic rock properties techniques, moreover mineral base model or multi mineral analysis method used in this research for the logging interpretation, to describe the minerals components utilizing Elan Plus software. A rock physics (Elastic constant) technique, based on wireline log data adopted, for dynamic elastic constant modeling identification, and constrain the logging interpretation results, by using log responses equations to calculate the density (synthetic) base on different mineral models assumptions and compare between original dynamic elastic modules and re-contracted elastic dynamic models. In order to achieve all these results, a comprehensive analysis performed for logging interpretation, calibrated to core data and integrated with DST results. The Studied reservoirs composed of dominant K-feldspar, Kaolinite, with considerable amount of quartz and traces of smectite and chlorite. The rock type had been classified into three facies, based on capillary pressure curves and core porosity versus permeability. The logging interpretation results and dynamic elastic models demonstrated an improvement in the reservoir characterization, obtained by integrating both logging interpretation and rock physics data.

Key Words: The Challenges for Shaly sand Petrophysics and Formation Evaluation, of Keyi oil-Field, Fula Sub basin, Sudan.