Illustration of how drilling location directly influences the success rate of geothermal exploration
Geothermal exploration is much deeper than surface water and always related to the faults and fractures. That make difficults for traditional geophysical survey. And higher coast of deeper (1000-3000M) drilling requires a more accuracy survey.
Geothermal Exploration Technique
Seismoelectric Method can not only overcome the problem of being complicated and costly, which are the shortcomings of traditional exploration techniques in exploration seismic survey geophone arrangement, but also overcome the shortcomings of being only applicable to the shallow surface detection with low resolution by the high density resistivity method, gravity method and magnetic method. In addition, the method of underground electrical shock sensitive fluid medium, can be effectively combined with a wealth of information while seismic signals and excitation signals of shock, underground fluid detection.
It is both an innovation on theory and a breakthrough on technology. It is also a practical method of detecting water, oil and gas underground. Compared with the traditional geophysical methods with seismoelectric exploration methods, seismoelectric method is a good fit for the geothermal exploration.
The DC-4500, computer, seismic source, electrodes, geophone, etc. compose a systerm to detect the underground fluid. When the fluid is near to the hot source, the liquid should be heated, that is the geothermal resource.
Seismoelectric survey vs MT survey
The figure above is MT survey results in this area. Previous MT survey didn’t find any potential and convincible geothermal resource. Due to the defect of the principle of MT method, it is difficult to locate deep aquifer which has much smaller signal than shallow aquifer. The principle of MT method is based on this equation:
R2 = R1/d3
R2 is apparent resistivity of deep aquifer;
R1 is apparent resistivity of shallow aquifer;
d is the distance between R1 and R2
Seismoelectric method is based on a different theory: the SE signal of deep aquifer is generated later than the SE signal of shallow aquifer, so we can differentiate SE signal from different depth of aquifers by time. Thus, this method is more ideal to detect geothermal resources.