Theoretical and experimental study of the composition of deep source gas. Final report. [Volatiles and gases in fluid inclusions in cements, quartz, calcites].

Author: Barker, C.
Published: United States : [publisher not identified], 1985
Springfield, Va.: National Technical Information Service, [approximately 1985]
Physical Description: microfiche : negative ; 11 x 15 cm

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Summary

As current natural gas supplies are consumed there will be increased pressure to explore in higher risk settings including areas much deeper than those routinely probed now. This raises the question of natural gas stability in the deep subsurface and a combined theoretical and experimental approach has been used to try and provide answers. A computer program has been developed for calculating the stabilities of natural gas components in reservoirs of various mineralogies. It finds the minimum free energy in multi-component (up to 70), multiphase (up to 20) systems for conditions corresponding to temperatures and pressures down to 40,000 ft. (12 km) and does not assume ideal gas behavior. These calculations show that methane has considerable stability in sandstone reservoirs even in the presence of feldspars and their clay breakdown products. However if there is appreciable calcite cement this tends to thermally decompose at high temperatures and the evolved carbon dioxde then dilutes the methane to give overall gas compositions that are unlikely to be economic. In carbonate systems the main factor influencing methane stability is the presence of sulfur-bearing phases such as anhydrite. The sulfur compounds lead to hydrogen sulfide production and methane is eliminated so that at 40,000 feet the predicted gas composition is CO2-H2S. If iron-bearing phases are present they can tie up some of the sulfur as sulfides and methane then survives. A computer-controlled, fast-scanning mass spectrometer system has been developed to analyze individual fluid inclusions in deep cements because these contain uncontaminated gas samples from the growth environment. Fluid inclusions are opened in vacuum by thermally-induced decrepitation. 50 refs., 21 figs., 8 tabs.

Report Numbers

DE85015759; DOE/MC/21229-2065

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Note

DOE contract number: AC21-84MC21229
OSTI Identifier 5122534
Research organization: Tulsa Univ., OK (USA).

View MARC record | catkey: 47355471

Actions for Theoretical and experimental study of the composition of deep source gas. Final report. [Volatiles and gases in fluid inclusions in cements, quartz, calcites].

Theoretical and experimental study of the composition of deep source gas. Final report. [Volatiles and gases in fluid inclusions in cements, quartz, calcites].

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