Habitat of natural gases in Papua New Guinea

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:425851

Schoell, M; Monnier, F ^[1]; Eisenberg, L I; Valenti, G L ^[2]

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1. Chevron Petroleum Technology Co., La Habra, CA (United States)
2. South Pacific Chevron Co., Brisbane (Australia)

Thermogenic natural gases in Papua New Guinea occur in hanging wall anticlines and related structures along a 160 mile section of the Papuan fold and thrust belt between S.E. Hedinia in the SE and Pnyang in the NW. Isotopic compositions of the oil associated gases in the SE between Hedinia and Mananda varies little ({delta}{sup l3}C{sub CH4}=-44{+-}2{per_thousand} and {delta}D{sub CH4}=-200{+-}20{per_thousand}). However, subtle isotopic and compositional patterns in these gases are structurally controlled and indicate primary differences in the filling history of the individual structures. In addition, secondary redistribution of the gases between the Agogo and Iagifu structure can be traced through isotopic similarities. In S.E. Mananda, however, gas isotope patterns are affected by bacterial degradation of the gas. Tire concentration of CO{sub 2} in the oil associated gases in the SE is low (0.6-3.0 %) and the carbon isotope values ({delta}{sup 13}C{sub CO2}=-10 to -19{per_thousand}) suggest an organic origin with minor inorganic contributions. Gas in the Juha structure ({delta}{sup 13}C{sub CH4}=-36.8{per_thousand}) is likely from a more mature source and has a CO{sub 2} concentration of 9.6% with a {delta}{sup 13}C{sub CO2}=-5.9{per_thousand}, indicating additional CO{sub 2} generating processes in this area, likely related to magmatic activity in the vicinity of the Juha structure. The Pnyang structure in the NW of the area holds a gas ({delta}{sup 13}C{sub CH4}-40.5{per_thousand}) which is isotopically intermediate between the Juha gas and the oil associated gases in the SE. The low CO{sub 2} concentration of 0.2% suggests that Pnyang is sourced from a gas kitchen similar to, but more mature than, the kitchen for the oil associated gases in the SE of the province. This is consistent with the high GOR in this structure and the association of the gas with a high API gravity condensate.

• OSTI ID: 425851
• Report Number(s): CONF-960527--
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
GEOCHEMISTRY
NATURAL GAS
NATURAL GAS DEPOSITS
ORIGIN
PAPUA NEW GUINEA
SOURCE ROCKS