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Origin of natural gas of dissolved-in-water type in Japan inferred from chemical and isotopic compositions: Occurrence of dissolved gas of thermogenic origin.

1989; The Geochemical Society of Japan; Volume: 23; Issue: 3 Linguagem: Inglês

10.2343/geochemj.23.139

1880-5973

Shun-ichiro Igari, Susumu Sakata,

Ocean Acidification Effects and Responses

Carbon isotopic ratios of methane (δ13C(C1)) and chemical compositions were measured for natural gases of dissolved-in-water type (dissolved gases) from several gas fields in Japan. Most of the samples have low δ13C(C1) values (-69.1∼-66.4‰) and contain small amounts of C2+(CnH2n+2, n≥2) hydrocarbons. These two features indicate that they are of biogenic origin as has been suggested by previous researchers. However, several samples from the Yaizu gas field have high δ13C(C1) values (-34.3∼-33.8‰) which cannot be of biogenic origin, but thermogenic origin. This is the first report to confirm the occurrence of dissolved gas of thermogenic origin in Japan.