沖縄本島南部の水溶性天然ガス

抄録

Two exploratory wells (Naha R-1 and Osato R-1) drilled in the southern part of Okinawa-jima, Okinawa Prefecture, Japan, for which the targets were basement gases dissolved in water, were successfully completed with good result from production tests. Geological and engineering information from the wells shows that the basement is a fractured reservoir for natural gases dissolved in water, mainly thermogenic methane based on carbon isotopic composition. This result contributes to a better understanding of the petroleum geology in the area, including the stratigraphy, the underground geologic structure, and the characteristics of reservoir rocks and fluids.

Further work including a comprehensive interpretation of well and seismic data for practical use, and an assessment of possible application of these gases dissolved in water, is necessary because of the limited exploration of basement in the potential distribution areas of the gases and insufficient ultization of data.