Geothermal Energy - Geophysics


Geophysics is a field of science that deals with the properties of the earth and its environments. It is the study of magnetic and gravitational fields, internal properties of the earth, water cycles, mineral deposit formation, and the solar terrestrial relations.

Geophysics specializes in finding resources under the earth’s crust and determining the potential threats such as earthquakes. It also entails qualitative analysis to identify the best sites for mining, oil drilling and geothermal deposits.

Branches of Geophysics

Various branches of Geophysics are −

  • Study of solid earth − Solid earth properties range from tectonic study to seismic analysis for earthquakes. This branch studies the oil and mineral deposits. The soils samples are analyzed for any unusual deposits or textures.

  • Study of water − This is the study of fresh water as well as water under the earth surface. Study of water is done by hydrologists who analyze water cycles and water tables. Oceanography, the study of the oceans and the ground beneath, also falls under this category.

  • Study of air − Air is a major component of the earth. The study of air helps in predicting weather conditions and guard against extreme conditions such as hurricanes.

  • Life and geophysics − The interaction of organisms and the earth is an important factor. It is important to note that oil deposits mainly result from decaying matter. Conditions below the ground are studied to assess their effect on the existence of organisms.


Some rocks, called aquifers, provide a good environment for water to flow through naturally. These rocks are porous and filter water running through. Aquifers are best sites where wells are drilled to provide constant water flow. Rocks that make good aquifers are sand, granite, conglomerate, sandstone, and fractured lime.

Aquifers lie underneath the water table such that precipitation immediately replenishes water pumped from wells. Aquifers are very important in sustaining the earth’s water cycle. Wells are drilled into aquifers surrounded by non-porous rock. These rocks generate pressure that helps in pumping the water. These kinds of wells are known as artesian wells.

Hydrogeology Tests

Hydrogeology utilizes several tests in aquifers to capture their characteristics. These tests are conducted in controlled environments called control wells.

The three major tests are −

  • Pumping test − Water is extracted and pumped back into the well at constant intervals. Behavior of neighboring wells is recorded as a result of the changes. This test helps in determining the permeability of the aquifers surrounding the well.

  • Slug test − Slug means a swift change in water level. In this test, the effect on the neighboring wells and the duration it takes to recover its original level is measured. This could be achieved by drawing from the lake or water could be pumped into the well to drastically change the level.

  • Constant-head test − This is done using an experimental well called a control well. In a control well the thermal drawdown can be maintained at a level. The effect is recorded for the neighboring wells. Drawing from the well regularly may dent the water table. This may cause depression and cause abnormal flow.