| Title | Numerical Simulation Of Evolution Of Steam-Water Two-Phase Zone In A Fractured Geothermal Reservoir By Considering Capillary Pressure Effects |
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| Authors | Tateishi, Yohei ., Itoi, Ryuichi ., Tanaka, Toshiaki . and Takayama, Junichi |
| Year | 2014 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | numerical model, steam-water two-phase zone, capillary pressure |
| Abstract | Pressure drawdown in a geothermal reservoir due to production operations may lead to a formation of steam-water two-phase zone in the shallower parts of the reservoir as has been observed in the Wairakei geothermal field in New Zealand and in the Ogiri geothermal field in Japan. In this study, we carried out numerical simulations using a three dimensional reservoir model for investigating the influences of steam and water capillary pressure on the evolution of two-phase zone in the shallower parts of the reservoir. A developed three dimensional reservoir model consists of a cap rock and fracture systems, and was made in reference to the field data obtained from the Ginyu fault zone of Ogiri. The Ginyu fault plays the main reservoir for steam production with temperatures around 230oC. Pressure and temperature profiles of the well in the exploration stage suggest that there was a steam-water two-phase zone below a low permeable cap rock in the shallow zone of this reservoir. Production and reinjection simulations with the developed numerical model to examine the growth of two-phase zone in reservoir by incorporating the effects of steam and water capillary pressure into the model were carried out. The results indicated a vertical extension of the two-phase zone due to pressure drawdown in the fracture part of the model. Also, the vaporization front is shown to progress slowly in the model compared to that without the effects of capillary pressure. Capillary pressure lowers the vapor pressure which then allows the liquid phase water to exist even the surrounding pressure reaches to saturated with respect to its temperature. |