豊羽鉱山における天然亀裂を含む鉱脈を用いた熱抽出実験のモデル化

抄録

Heat extraction tests through natural joints at high temperature were conducted at Toyoha Mine. At these tests, cold water was injected to a borehole at constant flow rate. Water which flowed through natural joints was produced from other boreholes. Flow rate, temperature and pressure of water at production borehole were measured during these tests. To understand the flow paths and the nature of heat extraction zone, computer simulation model was developed using FEHM (Finite Element Heat and Mass Transfer) code. And also we calculated the case of the continuous injection by using FEHM model. The major results obtained from simulation are as follows.
1) The natural water flow through the vein was about 0.182kg/s in the vertical direction and there was small amount of natural water flow in the horizontal direction.
2) As the natural water flow through the vein was larger than the injection flow rate of 0.67kg/s, the temperature and the flow rate of water from production boreholes did not change clearly by injecting water.
3) However, the temperature at the point where the production borehole No. 456 intersects the vein decreased a little as indicated by temperature measurement using the optical fiber.
4)Even in case of the continuous injection, cold area of Toyoha mine model was very narrow.