| Abstract |
In central Japan near Matsunoyama the hot spring field in Niigata Prefecture is pressured by the Izu Peninsula, which is defined by the presence of syntaxis. In the Matsunoyama geo-pressured region, the large Matsunoyama dome structure exists, where the natural gas field is characterized by Tertiary sediments. Generation testing of the 50kW Kalina cycle plant using the fluids from Takanoyu#3 well, at a fluid temperature of 97 oC and a flow rate of 300 L/min, has been progressing since 2010. An estimate of the power generation potential and sustainability of the hot spring reservoir in the geopressured field is based on the assessment of the geochemistry and historical production data from the Takanoyu#3 well. The Takanoyu#3 was drilled to a total depth of 1,300 meters in 2007 and its initial production rate was 623L/min. The fluid chemistry from Takanoyu#3 indicated the following concentrations: Cl of 10,000 mg/l, Na of 3,700 mg/l, K of 200mg/l, Ca of 2,100 mg/l and HCO3 of 36 mg/l, which are similar to those for Takanoyu#2, which was drilled to a depth of 280 meters. The gas composition of the fluid is about 95% CH4, 1.8% N2 and 0.5% CO2. The O-18 and Deuterium isotopes suggest that the fluid is enriched in both isotopes, with data points plotting to the right of the Japan meteoric line and the below that of the sea water. In the Matsunoyama field, the hot spring Takanoyu#2 well was drilled in 1964 with an initial flow rate measured at about 160 L/min. After 30 years, the production rate of Takanoyu#2 dropped to a constant rate of 100 L/min, about 65 % of the initial flow rate. . Similarly, the production rate of Takanoyu#3 has dropped to about 400L/min, which is likewise about 65% of the initial flow rate. |