Productivity in sandstone reservoirs can be adversely affected by changes in permeability and porosity due to varying cementation materials, diagenetic clays and dual porosity systems. Extended use of conventional log evaluation techniques have resulted in poor well completion strategies and misunderstanding of the log behavoir on the best production pay zones.For improving the well completion strategy, a methodology for quantitative evaluation of this type of reservoir is given. This evaluation is made using core-log correlation,thin section analyses, crossplot techniques and clay volume calculations in order to evaluate effective primary porosity and water saturation using inversion models. This methodology was successfully applied for identifying changes in permeability, clay volume and formation factor in this area and allowing for a reliable estimate of hydrocarbon production capabilities of the Lower C sandstones A case by case study of wells is presented. The productivity of these sandstones is calculated using different evaluation methods and compared with production data from the wells. The excellent correlation between the estimation of well production and actual production data led to a better calculation of the oil reserves and will aid future development plans..

Keywords:
sandstone, evaluation, core-log calibration, crossplot technique, well logging, correction, cementation, detection, upstream oil & gas, society of petroleum engineers
Subjects:
Reservoir Characterization, Formation Evaluation & Management, Open hole/cased hole log analysis
Copyright 1994, Society of Petroleum Engineers
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