Oilfield chemistry

Chemical and Carbon Isotope Composition Proves Effective as Gas Diagnostic Tool

This paper presents different geochemical approaches to assess the origin of produced gases and thermal maturity and evaluate the effect of adsorption on shale gas during production.

A modern natural gas processing plant during sunset
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Chemical and carbon isotopic compositions of produced gases are useful tools to monitor gas production and to assess their origin, thermal maturity, and migration. In the complete paper, the authors present different geochemical approaches to assess the origin of gases and thermal maturity and to evaluate the effect of adsorption on shale gas during production.

Introduction

Carbon isotope type curves constructed for compounds from methane through n-pentane can be used to group gases into distinct families and correlate them to their source rocks. Large variations in carbon isotope ratios exist among the natural gas compounds, which are caused by isotopic fractionation between the sedimentary organic matter (kerogen) and each individual hydrocarbon compound. During the generation of hydrocarbons from kerogen, cracking of 12C-12C bonds requires slightly less energy than 13C-12C bonds.

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