Integrated geological-petrophysical-reservoir engineering studies conducted within the Alberta basin, Canada, by Canadian Hunter Exploration, Ltd., resulted in the discovery of a number of gas fields, including the giant Elmworth field (Masters, 1979; and Sneider et al, 1983). These studies utilized rock-fluid data from cuttings, cores, well logs, and drill-stem and production tests to determine reservoir-rock potential and hydrocarbon saturation of thick, multiple Cretaceous sandstone and conglomerate intervals. These rocks typically range in porosity from 3 to 15% and in permeability from a few microdarcys to several darcys. Key elements in the exploration search and field exploitation are the evaluation of reservoir-rock quality, determination of the depositional facie containing the best reservoir rocks, and integrated log evaluation that identifies and quantifies lithology, porosity, and fluid type and distribution.

This paper focuses on the rock-log part of the integrated studies and discusses the methodology used to establish accurate evaluations of pore space and hydrocarbons of all drilled wells. The paper is presented in three parts. The first part covers the evaluation and characterization of reservoir-rock properties primarily from well cuttings. The second part addresses rock-log calibration methods and describes "quick-scan" and digital log analysis techniques for accurate porosity and hydrocarbon saturation determination. The third part presents some examples that illustrate the methodology and results of rock-log calibration.