A New Prospecting Method on the Hydro-geological Properties of Fractures in Geothermal Field

摘要

The definition of the fracture and the concept of the reservoir engineering were described as a basic knowledge on a new prospecting method on hydro-geological structure of the fracture. The method combines the computer aided pressure transient testing method, the method using the highly accurate tilt-meter and the metering method of two-phase flow. Summaries of the outline of this prospecting method are as follows.(1) In the computer aided pressure transient method, water injection and air pressure systems were used to change fluid injection rate in the well. The former is used for high permeability formations, and the latter used for low permeability formations. The water injection pump and the compressor were controlled by inverter control in sine wave type. Then learning and fuzzy functions were installed in computer to control the compressor. The analysis software of test data was improved for the use on personal computer. As the result of applying this method to some actual geothermal fields, highly reliable measurement on the hydro-geological parameter were acquired.(2) As the result of the simulation on the observation method using the high precious tilt-meter, the effect of the reservoir parameters (depth, permeability, pressure and Young's modulus et al.) on the inclination of surface was quantitatively estimated. It was clarified that this observation method effectively functioned in order to estimate activity fracture distribution and hydro-geological parameters.(3) In two-phase flow rate metering method, the metering system which combined laser beam flow-meter with the magnet-strain level indictor is used. As the result of applying the metering system in actual geothermal field, it was shown that this metering system was sufficiently effective under the two-phase flow conditions (40 m /s in steam velocity and 2 m /s in hot water flow velocity).