Composition Correlations of Natural Gas in Reservoir Engineering Problems

Abstract

Abstract This paper is presented as a summary report of the use of well gas composition correlations obtained from mass spectrometer recordings as a means of identification and determination of reservoir continuity. Conventional methods for detecting composition differences are expensive, elaborate, and difficult to obtain. This excludes the use of extensive composition data for most applications. During recent years the mass spectrometer has come into general use as an analytical tool in petroleum refineries. The use of mass spectrometer composition patterns in characterizing or "finger-printing" the produced gas from a reservoir, presents a novel method for correlating gas samples from well to well. The mass spectrometer provides a trace similar to an electric log, having peaks which represent the abundance of certain hydrocarbons in the well gas sample. Without going further into the detailed analysis, the idea has been advanced that these traces or patterns could be used as a means of identifying a particular natural gas. This theory has proven to be essentially correct. The mass spectrometer pattern method is simple and cheap as compared to other standard methods. It greatly facilitates the solution of reservoir and geological problems in which correlation of well gas compositions is a factor. Specific field applications have been made. This paper concerns the results obtained in 465 individual gas analyses from 35 fields and 77 reservoirs. In a number of cases it has been found that such data have been extremely valuable in the determination of reservoir continuity. In at least one case, the method was a valuable contribution in tracing a reservoir from sand to sand in a complex faulted field involving numerous gas reservoirs. Field applications are presented to illustrate the possibilities of the method at the present stage of development and to stimulate the employment of this new approach by geologists and petroleum engineers in the industry.