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Solid-state NMR analysis of coals and shales from the Mesaverde Group, Green River Basin, Wyoming

Technical Report ·
OSTI ID:10108019
Samples of coals and shales from the Almond Formation of the Mesaverde Group, Greater Green River Basin, Wyoming were analyzed using solid-state {sup 13}C nuclear magnetic resonance (NMR) techniques of cross polarization with magic-angle spinning (CP/MAS). The samples were taken from a present-day depth of burial ranging from {approximately}3,000 to {approximately}15,000 ft. In addition, CP/MAS {sup 13}C NMR measurements were made on residues from the hydrous pyrolysis of Almond coal. The hydrous pyrolysis experiments were conducted isothermally for 72 hr in the temperature range of 290 to 360{degree}C (554 to 680{degree}F). In general, the maturation trends observed by NMR for the naturally and artificially matured samples were in agreement with results obtained from other geochemical analyses. The NMR spectra of the naturally matured shale samples showed only a small aliphatic component at depths greater than about 12,000 ft, indicating little capacity for hydrocarbon generation at depths greater than this. Vitrinite reflectance measurements placed the oil window at between 4,500 and 14,500 ft. NMR measurements of the hydrous pyrolysis residues showed a clear loss of aliphatic carbon, relative to the aromatic carbon, with temperature. For the residue obtained from the highest study temperature (360{degree}C/680{degree}F), there was a 60% depletion of the hydrocarbon-producing aliphatic components. The trends in loss of aliphatic carbon with temperature suggested a means of defining a geochemical transformation ratio in terms of the loss of the aliphatic carbon fraction. A good correlation was found between the NMR transformation ratio and the production index determined by Rock-Eval pyrolysis measurements.
Research Organization:
University of Wyoming Research Corp., Laramie, WY (United States). Western Research Inst.
Sponsoring Organization:
USDOE, Washington, DC (United States); Gas Research Inst., Chicago, IL (United States)
DOE Contract Number:
FC21-86MC11076; FG05-89ER75506
OSTI ID:
10108019
Report Number(s):
DOE/MC/11076--3554; ON: DE94000079; BR: 400403000/AA0520000; KN0000000; CNN: 5091-221-2146
Country of Publication:
United States
Language:
English