ABSTRACT
As reservoir engineers, we can analyze most conventional oil and gas reservoirs and even tight gas plays by measuring or estimating the variables that constitute Darcy’s law and the material balance equation. These include:
nn PVT properties such as viscosity, formation volume factor, and isothermal compressibility nn Porosity and saturations nn Reservoir pressure and temperature nn Permeability including phase relative permeabilities nn Reservoir geometry including thickness and area nn In the case of hydraulic fractured wells, fracture geometry, and permeability
Complete descriptions of reservoir performance in conventional reservoirs and tight gas may further require knowledge of natural fractures and other detailed heterogeneities. The spatial variations of reservoir properties as dictated by geology represent the largest group of unknowns. The most critical aspect of this variability is often the spatial correlation of extreme values such as in natural fractures of faults. Conventional tools to address this problem include 3D or even 4D seismic to improve the spatial model, integration of geological knowledge about the reservoir along with petrophysical (and less frequently but likely no less important geomechanical) information into an integrated earth model.
