Measurement of thermal maturation of petroleum by proton magnetic resonance spectroscopy

Abstract

THE processes of petroleum generation and maturation have been shown to depend on the thermal breakdown of organic material contained in the sediments as the temperature increases due to increased burial depth^1,2. Measurement of the degree of thermal alteration of the organic matter in shales and other potential petroleum source rocks is therefore of fundamental importance to petroleum exploration. The most common methods of estimating the degree of thermal alteration are based on measurements of the residual insoluble organic material in rocks. Some of the more common methods use changes in the chemical composition of the kerogen², electron spin resonance³, kerogen coloration⁴ and vitrinite reflectance⁵. The method reported here is based on measurements on the soluble aromatic hydrocarbons extracted from the sediments. As the aromatics are represented in both the source rock and reservoir petroleum they may eventually provide a useful medium for comparing the thermal history of reservoir and source rock hydrocarbons. This method uses well established chemical techniques and provides a simple quantitative measure of thermal maturation by measuring the percentage of aromatic protons in the aromatic fraction of petroleum.