Application of Dielectric and Standard Logging Suites to Characterize the Stratigraphic and Lithologic Variations in Archie Parameters within the Green River Formation of the Greater Monument Butte Field, Uinta Basin, Utah, USA

摘要

Estimation of accurate electrical property parameters, such as the “cementation exponent” m and “saturationexponent” n is critical for characterizing hydrocarbon saturations with resistivity based models for completionsdecisions and original oil-in-place estimation. These exponents are known to vary with formation brine salinity,clay-content, porosity, grain-size distribution, pore geometry, stress and fluid wettability. Consequently, within largecomplex reservoirs electrical parameters will vary stratigraphically, lithologically and geographically.Characterizing these variations in a field petrophysical model is critical for successful reservoir characterization andfield development.Traditional methods for estimating m and n are problematic. Core-based measurements of m and n are timeconsumingand expensive. It is also difficult to reconstruct in-situ restored state conditions for accurate estimation ofm and n with core-based methods. Because of the high paraffin content in our oil, the cleaning processes involvedin preparing core samples for electrical property measurements can alter the original clay structure and wettabilityresulting in inaccurate estimations of m and n. Standard log-based methods for estimating m rely on analysis in a“wet” sand, often not present in unconventional fields and extremely rare at Monument Butte. NMR logging can beused to measure saturations in the flushed zone, but can be prohibitively expensive for routine application in acomplex reservoir.A method for estimating m and n using dielectric data in combination with standard triple combo logs has beendeveloped (Ramakrishna et al, 2012). We expand upon the dielectric model and apply this methodology to over 40wells within the Green River Formation of the Greater Monument Butte Unit (GMBU) in northeastern Utah, USA.The GMBU covers approximately 100,000 acres with numerous productive stratigraphic units and variable clasticand carbonate depositional facies. This methodology has the distinct advantage of measuring the properties in-situand allows us to economically extend the analysis to non-cored intervals and additional regions within the field. Inthis study we illustrate the variations in m and n with variations in rock quality, facies, wettability and stratigraphywithin the complex Green River reservoirs.