Most gas reserves in Algeria are located in unconventional tight reservoirs that typically contain multiple rock types from different depositional systems. Identifying and evaluating these reservoirs is difficult. Permeability predictions are very challenging because of results reliability from different downhole tools, and also by its direct relationship on production and economic impact.

This paper presents a case study that used an integrated formation evaluation approach of tight reservoir during an appraisal stage in an Algerian gas field. The workflow includes:

  • Petrophysical model using stochastic analysis to get shale volume, effective porosity and water saturation calculation.

  • Hydraulic flow unit zonation using flow zone indicator (FZI) and global hydraulic element (GHE) methods identified from core data.

  • Pressure transient analysis from wireline formation tester.

  • Mathematical phi-k relationship from core data under confining pressure.

  • Synthetic permeability log using previous relationships

In addition to determining reservoir geomechanical properties from the micro frac operation, Synthetic permeability curve were generated in areas of the reservoir that were not core sampled. These predictions were constraint by core data analysis as well as permeability from wireline formation tester.

This methodology was applied in an Ordovician tight sandstone reservoir in the South east Algerian Sahara gas field.

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