Geochemical analysis of Fort Worth Basin Barnett gas samples collected from the well head offers insight into basin evolution and thermal maturity at a resolution and level of confidence superior to traditional maturity proxies. Gas geochemistry, including bulk composition and stable isotope composition, is a direct measurement of the product we wish to exploit and bring to sale. Gas geochemistry is apparently independent of production history, drilling and completion practices, or other metrics that introduce complex, irresolvable variables.
Bulk compositional analysis of Barnett gas samples clearly demarcates dry gas from liquids-rich " windows" of the resource play. Additionally, bulk composition of these gases reveals the influence of noncombustible components to the heating value of produced gases.
The isotopic chemistry of gases reflects their source geochemistry as well as level of thermal maturity. Methane isotopes, unlike heavier methane homologues, behave in a strongly linear fashion over a wide maturity range. Methane carbon and hydrogen isotope compositions become more positive (isotopically " heavier") with increasing thermal maturity. This relationship is the well-known kinetic isotope effect. Thermal maturity derived from study of the hydrogen and carbon isotopes of methane for the Barnett is mappable, and when compared to other maturity proxies provides a superior characterization of the thermal maturity of the resource play on a local scale. Gas isotope geochemistry can be an effective forward-modeling tool for resource play development and high-grading existing leasehold.
The exploration for, and exploitation of, self-sourcing reservoirs normally involves geochemical characterization of a target interval. Typically, organic richness, organic type, level of organic transformation (maturity), and mechanical properties of the target interval are studied. The current investigation emphasizes the importance of accurately and rapidly defining the thermal maturity of the Barnett in the Fort Worth Basin at a scale of individual well locations.