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Titre du document / Document title

Biogenic origin of coalbed gas in the northern Gulf of Mexico Coastal Plain, U.S.A

Auteur(s) / Author(s)

WARWICK Peter D. (1) ; BRELAND F. Clayton (2) ; HACKLEY Paul C. (1) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) US. Geological Survey, 956 National Center, Reston, VA 20192, ETATS-UNIS
(2) Louisiana Department of Natural Resources, 617 North 3rd Street, Baton Rouge, LA 70802, ETATS-UNIS

Résumé / Abstract

New coal-gas exploration and production in northern Louisiana and south-central Mississippi, Gulf of Mexico Basin, is focused on the Wilcox Group (Paleocene-Eocene), where the depth to targeted subbituminous C to high volatile C bituminous coal beds ranges from 300 to 1680 m, and individual coal beds have a maximum thickness of about 6 m. Total gas content (generally excluding residual gas) of the coal beds ranges from less than 0.37 cm3/g (as-analyzed or raw basis; 1.2 cm3/g, dry, ash free basis, daf) at depths less than 400 m, to greater than 7.3 cm3/g (as-analyzed basis; 8.76 cm3/g, daf) in deeper (> 1,500 m) parts of the basin. About 20 Wilcox coal-gas wells in northern Louisiana produce from 200 to 6485 m3 of gas/day and cumulative gas production from these wells is approximately 25 million m3 (as of December, 2006). U.S. Geological Survey assessment of undiscovered, technically recoverable gas resources in the Gulf of Mexico Coastal Plain, including northern and south-central Mississippi, indicates that coal beds of the Wilcox Group contain an estimated mean total 109.3 million m3 (3.86 trillion ft3) of producible natural gas. To determine the origin of the Wilcox Group coal gases in northern Louisiana, samples of gas, water, and oil were collected from Wilcox coal and sandstone reservoirs and from under- and overlying Late Cretaceous and Eocene carbonate and sandstone reservoirs. Isotopic data from Wilcox coal-gas samples have an average δ13CCH4 value of-62.6% VPDB (relative to Vienna Peedee Belemnite) and an average δDCH4 value of -199.9%o VSMOW (relative to Vienna Standard Mean Ocean Water). Values of δ13CCH2 range from -25.4 to 3.42%o VPDB. Produced Wilcox saline water collected from oil, conventional gas, and coalbed gas wells have δDH2O values that range from -27.3 to -18.0%o VSMOW. These data suggest that the coal gases primarily are generated in saline formation water by bacterial reduction of CO2. Shallow (<150 m) Wilcox coal beds containing freshwater have little or no biogenic gas. Molecular and isotopic analyses of gas samples collected from conventional gas and oil wells suggests that both biogenic and thermogenic gases are present in and adjacent to the Wilcox intervals that contain biogenic coal gases. Oil, probably sourced from thermally mature, down-structural-dip parts of the Wilcox Group, is produced from sandstones within the coal-bearing interval Gas chromatograms of C10+ saturated hydrocarbons from Wilcox oils show a depletion of n-alkanes probably resulting from biodegradation of the oil. Isotopic composition of the gases associated with the oils is of mixed themogenic and biogenic origin (average δ13CCH4=-44.4%o VPDB, and average δDCH4=-182.4%o VSMOW).

Revue / Journal Title

International journal of coal geology    ISSN  0166-5162   CODEN IJCGDE 

Source / Source

2008, vol. 76, no 1-2 (187 p.)  [Document : 19 p.] (2 p.), pp. 119-137 [19 page(s) (article)]

Langue / Language

Anglais

Editeur / Publisher

Elsevier, Oxford, ROYAUME-UNI  (1980) (Revue)

Mots-clés anglais / English Keywords

North America

;

United States

;

Atlantic Ocean

;

North Atlantic

;

Northwest Atlantic

;

North American Atlantic

;

Mesozoic

;

clastic rocks

;

Phanerozoic

;

Cenozoic

;

Tertiary

;

Paleogene

;

sedimentary rocks

;

carbonaceous rocks

;

coal

;

Mississippi

;

Louisiana

;

Gulf of Mexico

;

deuterium

;

saturated hydrocarbons

;

gas chromatograms

;

stable isotopes

;

formation water

;

C-13/C-12

;

carbonates

;

Cretaceous

;

reservoirs

;

sandstone

;

natural gas

;

microorganisms

;

coalbed methane

;

methanogenesis

;

volatiles

;

Eocene

;

Paleocene

;

bituminous coal

;

coastal plains

;

biogenic origin

;

Mots-clés français / French Keywords

Amérique du Nord

;

Etats Unis

;

Océan Atlantique

;

Océan Atlantique Nord

;

Océan Atlantique Nord Ouest

;

Océan Atlantique Nord Américain

;

Mésozoïque

;

Roche clastique

;

Phanérozoïque

;

Cénozoïque

;

Tertiaire

;

Paléogène

;

Roche sédimentaire

;

Roche carbonée

;

Charbon

;

Mississippi

;

Louisiane

;

Golfe du Mexique

;

Deutérium

;

Hydrocarbure saturé

;

Chromatogramme phase gazeuse

;

Isotope stable

;

Eau formation

;

C 13-C 12

;

Carbonate

;

Crétacé

;

Réservoir

;

Grès

;

Gaz naturel

;

Microorganisme

;

Méthane couche charbon

;

Méthanogenèse

;

Matière volatile

;

Eocène

;

Paléocène

;

Charbon bitumineux

;

Plaine côtière

;

Origine biogène

;

Mots-clés espagnols / Spanish Keywords

America del norte

;

Estados Unidos

;

Océano Atlántico

;

Océano Atlántico Norte

;

Roca clástica

;

Fanerozoico

;

Cenozoico

;

Terciario

;

Paleógeno

;

Roca sedimentaria

;

Roca carbonosa

;

Carbón

;

Misisipi

;

Luisiana

;

Golfo de Mejico

;

Deuterio

;

Isótopo estable

;

C 13-C 12

;

Carbonato

;

Cretáceo

;

Gres

;

Gas natural

;

Microorganismo

;

Materia volátil

;

Eoceno

;

Paleoceno

;

Carbón bituminoso

;

Planicie costera

;

Origen biogénico

;

Mots-clés d'auteur / Author Keywords

Coalbed gas

;

Methanogenesis

;

Wilcox Group

;

Gulf of Mexico Basin

;

Localisation / Location

INIST-CNRS, Cote INIST : 18273, 35400018536681.0110

Nº notice refdoc (ud4) : 20792757



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