Computer Analysis of a Limited Well Log Suite in a Geothermal Well -- A Case History

Abstract

This paper presents the case history of analysis of a "limited" logging suite (density, sonic, gamma ray, caliper and temperature) from a geothermal well with a complex mixture of sedimentary and igneous lithologies. The drill cuttings description listed at least nineteen lithologica types. Starting with the drill cutting description and digitized log date, a detailed lithologic zonation of the well achieved by systematic analysis of the clustering of data points cross plots. Because of the large number of lithologic types and limited logging suite, quantitive estimates of the various lithologic components and porosity could not be obtained. However by comparing all log responses and lost correlation data, the porous zones could be identified. An estimate of mechanical strength of various zones from density and sonic logs correlated well with caliper log and physical characteristics expected of various lithologies.