| Abstract |
In the T-Project, Tohoku University, a subsurface system, which consists of an artificial, globally flat crack and two wells, were successfully constructed as designed (Takahashi and Abe, 1988). After the connection of the two wells through the reservoir crack, experiments to examine the hydraulic properties of the subsurface system were performed. The experiments were the transmissivity tests, the circulation tests and the tracer test. Th~ objective of the present paper is two fold. The first is to evaluate the hydraulic properties of the subsurface system of the r-Project and the second is to develop the methods to predict the flow impedance and to estimate the area of the effective heat exchange surface from the tracer tests. To this end, the water pressure and velocity distribution of the flow in a penny shaped crack with an inlet and an outlet are analyzed, where the water loss during the circulation is appropriately taken into account. The transmissivity can be obtained by the straight forward manner proposed by Jung (1987). Based on the analysis just stated, the flow impedance can be expressed as a function of the crack size, the transmissivity and the location of the inlet and the' outlet. Therefore, the flow impedance is predictable when these are given. This approach is applied to the subsurface system of the r-Project. The application results show that the approach gives excellent predictions. As to the evaluation of the area of effective heat exchange surface, the time variation of the tracer concentration at the outlet during the tracer test is firstly simulated based on the analysis of the flow stated before. The outlet tracer return profile so constructed is compared with the results of the tracer test to evaluate the area of the effective heat exchange surface. It has been found that the area is approximately 470 m2. |