Porosity From Well Logs of the Kuparuk Reservoir: Procedures for Using Core Data

Abstract

ABSTRACT This paper describes a reservoir description technique for computing porosity using both core and log data from the Kuparuk formation, North Slope, Alaska. Core porosity is used as a calibration tool to define clay parameters of the gamma ray and porosity logs. The gamma ray log must be normalized to apply its corresponding clay parameters. This approach is necessary in this reservoir because of the uncertainty in estimating clay volume fractions from well logs alone. Clay parameters can be applied over a wide area to compute porosity in uncored wells. An analysis of core samples indicates that quartz and siderite are the dominant non-clay components. Various clay minerals and minor amounts of other carbonate minerals are also present. Moreover, natural fractures and vugs have been identified in core samples from zone C of the Kuparuk. Porosity and volume fractions of quartz, siderite, and clay are calculated using the density, neutron, and gamma ray logs. Fractured intervals are identified with the sonic log. A comparison of core versus log data is presented from three cored wells of the Kuparuk field. Siderite concentrations obtained from logs agree with foot-by-foot measurements on cores. Agreement between computed and core porosity is usually two porosity units or better.