Abstract
The Niigata gas field yields methane gas associated with connate water from the Quaternary formations, i.e. the Uonuma group. This field is divided into two productive areas. One is the Niigata gas field in sensu strictu, and the other the Kita-Kambara gas field. Kajigawa No. 1 is the first exploratory well to the latter, of which location is nearly at the center of the basin.
Two gas horizons were tested by this well. Because of good productivityindices, the productivity of gas of both horizons are satisfactory. But gas-water ratio is slightly under the theoritical solubility value in both horizons.
Although high salinity of the connate waters may indicate that the marginal meteoric water of low salinity does not yet invade this area, the geochemical properties of connate waters coin cide with the low gas-water ratio and there may be possibility that the present producing horizons rapidly merge in low potential area towards the margin of the basin.
