Geothermal energy is the heat from the Earth. It's clean and sustainable. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma.
The global distribution of geothermal energy mainly concentrates in three areas: the first is the west coast of circum-Pacific belt, which includes south of New Zealand, West Indonesia, Philippines, Japan, China Taiwan as well. The second is the Mid-Atlantic Ridge zone, mostly in the ocean, across the northern end of Iceland; the third is the Mediterranean to the Himalayas, including Italy and China's Tibet. So there are good prospects for geothermal exploration in Indonessia and Japan.
Geothermal exploration is the exploration of the subsurface in search of viable active geothermal regions with the goal of building a geothermal power plant, where hot fluids drive turbines to create electricity. Exploration methods include a broad range of disciplines: geology, geophysics, geochemistry and engineering.
In recent years, more and more countries are starting to use geothermal energy, especially in the distribution of the world's major countries at the junction of the plate. Most of the world's geothermal resources are concentrated in the tropical Pacific Rim (Ring of Fire), the local geothermal gradient and heat flux among the highest in the world, and therefore possess the world's largest geothermal power plant.
Geothermal Exploration Technique
Seismoelectric Method can not only overcome the problem of traditional exploration techniques in exploration seismic survey geophone arrangement which is complicated and costly shortcomings, but also overcome the high density resistivity method which is only applicable to the disadvantage of the shallow surface detection, with low resolution gravity and magnetic methods of the class shortcomings. 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.
SINOPEC Seismoelectric Geothermal Survey Project
In 2014, SINOPEC cooperated with Seismo Electronics LLC to operate the geothermal exploration project in Pleasant Bayou, Houston, TX, USA. The geothermal resource in this area is from Frio Formation. It shows the fault is developed, the major fault strike is north-east to south-west. The survey area is located on a big fault in the middle of this area.
The survey area located in the south of Houston with a rectangular boundary. Based on owner’s requirement, we only made two-dimensional survey line construction design. Generally speaking for good result to find geothermal, three-dimensional composed 2-3 parallel survey lines is necessary. We designed two exploration seismic survey line, which are located in the west and the north boundary of the target area, containing a total of 34 exploration seismoelectric measuring points.
According to the two seismic survey lines and faults, we selected two lines made a total of four cross-section: AA ', BB', CC 'and DD'. We combine geological information on cross-sectional data and calculate the depth and thickness of the water layer. Where in the cross section BB 'displays information earthquake measuring points with the well known (N1) comparative analysis of information so as to make exploration more accurate.
It shows a cross section from the L11 to L14(DD’). Between measuring points L12 and L13 there are faults. This fault on both sides are still a dense impermeable rock (shale) in perpendicular to the fault type in the fracture zone. By comparing the SEW of L12-L13 and R5-R8, we find that fracture between L12-L13 is wider than R5-R8, more liquid can be stored. If drill a well here, the production of water should higher than the zone of R5-R8. As we all know it also requires further exploration. If the water of two faults are from a same water source, high permeability faults more producing water.
It shows the cross section from R4 to L16(AA') consecutive measuring point data. Between the measuring point R5 and R8 the fault exists. Both sides of the fault are dense rock (there should be a shale) formed fracture zone in a direction perpendicular. Underground water flow along the vertical fracture zone to shallow area. If we drill a well here, it will get geothermal groundwater.
Processed and Interpreted seismoelectric data compare with nearby well log data show 70% match.
The results of this project show that seismoelectronic technic can help us find the geothermal water which other geophysical methods is difficult to find. The evaluation committee of SINOPEC gave our technology high recognition with proof which we can provide to our new customer.