With the concern over anthropogenic climate change (i.e. man-made climate change), there is a growing awareness that we must utilize energy resources that are sustainable. The power obtained from geothermal reservoir is one such sustainable resource that has the potential to supplement our energy systems and to displace many conventional fuels. In contrast to many renewable technologies, such as wind or solar, the geothermal resource can be used 24 hours a day, 7 days a week without any harm to the environment.
It is due to this reason that geothermal development, a natural extension of oil and gas development activities, is attracting both new petroleum engineering graduates and established petroleum engineers in increasing numbers. Along with the importance of geothermal energy, this paper details as to how different phases of geothermal industry like drilling, production, and reservoir utilize petroleum engineering techniques, the challenge awaiting engineers as they work to solve first- time problems and improve technology for future activities. The geothermal industry has tremendous potential for growth and will make a significant contribution to worldwide energy supplies.
The basic study from which this paper is prepared is the result of rapidly depleting petroleum reserves and the growing need throughout the world for increasing quantities of energy in all forms. Quite obviously, natural forms of energy that are readily available at low development cost are those in greatest demand. The underdeveloped countries and particularly those having little or no petroleum resources, are the countries in which the most interest is being shown in the newer energy sources. One of the least expensive energy sources is natural geothermal energy. Although this form of energy has been recognized for centuries, it has been only during the past few decades that serious efforts have been made to harness it.
Geothermal energy is heat energy originating deep in the earth's molten interior. It is this heat energy that is responsible for tectonic plates, volcanoes and earthquakes. The origin of this heat is from primordial heat (heat generated during the Earth's formation) and heat generated from the decay of radioactive isotopes. The temperature in the earth's interior is as high as 7000°C, decreasing to 650 - 1200°C at depths of 80 km -100 km. Through the deep circulation of groundwater and the intrusion of molten magma into the earth's crust, to depths of only 1 km-5 km, heat is brought closer to the earth's surface. The hot molten rock heats the surrounding groundwater, which is forced to the surface in certain areas in the form of hot steam or water (e.g. hot springs and geysers). The heat energy close to, or at the earth's surface can be utilised as a source of energy, namely geothermal energy.
The total geothermal resource is vast. However, geothermal energy can only be utilised in regions where it is suitably concentrated. These regions correspond to areas of earthquake and volcanic activity, which occur at the junctions of the tectonic plates that make up the earth's crust. It is at these junctions that heat energy is conducted most rapidly from the earth's interior to the surface, often manifesting itself as hot springs or geysers. There is currently an estimated 15,000 MW of direct use and over 9,000 MW of generating capacity in geothermal resources worldwide. To put geothermal generation into perspective, this generating capacity is about 0.4% of the world total installed generating capacity.