Applications of Recent Reservoir and Petrophysical Developments to a Field Study

Abstract

Fifth Annual Joint Meeting of the Rocky Mountain Petroleum Sections of AIME, 2–3 April, Casper, Wyoming Abstract A reservoir and petrophysical study was made of the Red River (Ordovician)reservoir of the Gas City field. The heterogeneous carbonates which make up the reservoir were grouped by the physical properties which control fluid saturations and fluid flow. The fluid content of the reservoir was determined from the capillary characteristics of the groups of rocks and from porosities calculated from the radioactivity log. It was found that the reservoir void volume contains a large percentage of fine pores and a high average water saturation; however, distribution of the larger pores was such that all ranges of porosity will contribute some oil to production. The utilization of an electronic computer to calculate porosity from the neutron log proved an effective, rapid means for evaluating a large number of logs. Saturation calculations from electrical logs were used as a check on capillary determinations, and the results of the two different methods were substantially in agreement. The methods outlined should result in a more accurate estimate of reservoir fluid content and a better understanding of reservoir performance. Introduction The engineering study of an oil reservoir has as its major objectives (1) the determination of the types and quantities of fluids in place at the original reservoir conditions, (2) the determination of the productive forces active in the reservoir, and (3) an estimate of the fluids which will be produced under various methods of operation. Particularly during the early life of an oil field, the original contents of the reservoir can be estimated most accurately by determining the volumetric and saturation parameters of the intervals being exploited. For this purpose core analysis and various types of well logs are in general use.