Differences in reservoir characteristics of marine and nonmarine sandstones of the Mesaverde Group, northwestern Colorado

Abstract

Reservoir and rock properties change with the different diagenetic and depositional environments present in strata of the Cretaceous Mesaverde group. These changes can be seen in the 4200 ft (1280 m) of core taken from the Mesaverde group at the US Department of Energy's Multiwell Experiment site, located in the Rulison field in the east-central part of the Piceance Basin, northwestern Colorado. Comparative measurements of porosity, permeability, water saturation, Young's modulus, Poisson's ratio, compressive and tensile strengths, and fracture toughness suggest that variations in these petrophysical properties are controlled by petrologic changes, that are in turn a function of depositional and diagenetic environments. For example, sandstones deposited in high-energy marine environments are ''cleaner'' and therefore have uniform permeability distributions and high Young's Moduli. Sandstones formed in coal-bearing strata have irregularly distributed but generally higher porosity and permeability due to irregular nonmarine environments and the presence of organic acids during diagenesis. 32 refs., 25 figs., 6 tabs.