新潟地域油•ガス田付随水の水素および酸素の同位体組成
1986 年 51 巻 2 号 p. 113-122
詳細
1986 年 51 巻 2 号 p. 113-122
Dueterium and 18O analyses were made on waters associated with oil and gas from Niigata basin.
The δD and δ18O values of formation waters vary from -8 to -20‰ and -4 to +3.5‰ relative to SMOW respectively. The δ18O values of formation waters from lower horizons tend to enrich the heavier oxygen. There is a positive correlation between δ18O value and formation temperature.
Although the δD and δ18O values of condensed waters vary widely, they seem to be lighter than those of formation waters.
It is inferred that the origin of formation waters may be sea waters entrapped during deposition and undergone chemical and isotopic alteration since their original entrapment.
The isotopic composition of condensed waters and formation waters in a reservoir shows a stragiht line on δD vs δ18O plot. The estimated temperature from slope of the line agrees with measured temperatures.
Since the isotopic compostion of condensed waters in a gas pool may have a close relationship to distance from the water level, it could be useful in monitering the gas/water contact.
