Today, geophysical explorations have many applications on many different underground or structural problems. For exploration studies of mines, pollution sites or oil and gas fields, geophysical methods have very successful efforts. In general, electromagnetic ways of prospecting are not the first method used in the fields, despite the fact that the methods are not well known or not widely used. In practice, electromagnetic methods are very successful in environmental duties. In addition to that, electromagnetic explorations are known as an expensive method because of some special cases even the method is not high-cost in many other field works. Another important aspect of the electromagnetic methods is practicability. In relation with the theory and the device properties, electromagnetic methods are user friendly. At last, electromagnetic methods are open to improvements because of the new application circumstances and interpretation abilities in relation with other prospecting methods. Due to the facts of being environment friendly, economically advantageous, user friendly and having good future, the electromagnetic methods’ applications have very important benefits and they are very important in geophysical underground explorations.
First of all, some abilities and application methods of the electromagnetic methods are providing the speciality of environment friendly. According to Gerkens (1989, p. 605), a big advantage of electromagnetic induction methods is there is no need for linking apparatus for transmitter and earth surface linking and receiver and earth surface linking. Also he adds this property gives the ability to make explorations from air (1989, p. 605). In addition, as pointed out by U.S. Department of Energy (2004, para. 7), decrease in yearly power keeps around sixteen percent in research drilling and decreasing of price and environmental strong effect of research by application of cheap tools. By doing this kind of surveys there is no destructive effect to the area and to the nature because of the reduced environment effect of the surveys. Furthermore, as told by Strack, in 1992, nearly all common metals appear in environment in forms of sulphide ores and adds that sulphide ores are extant in subsurface medium as a non-resistive, especially in solid forms (p. 5). In collaboration with the idea of geophysical surveying techniques are the non-destructive applications which are valuable devices for underground researches (Armah, n.d., para. 4). Additionally, as mentioned by Armah, ground penetrating radar, which is one of the E. M. methods, has benefits for hard work areas, for example, for solid ground situations do not generate obstacles because there is no need for direct connection to the ground and in addition, in rough areas it has superiority for data collecting (n.d., para. 14). These properties are the marker of success of the E.M. methods in environmental studies. Moreover, recent pollution cases or large scaled ground-water pollutions by total dissolved solids (TDS) are very bright materials to find because of the lowest resistivity values (Campbell & Fiterman, n.d., p. 5). Also, as shown by Unsworth (2005), explorers have many different combinations for different studies, such as land or marine explorations or natural source or controlled source investigations of the underground (pg. 38) (See Table 1). In light of the facts of being applicable in environmental duties and environment friendly usage, electromagnetic methods are the bright prospecting style.
Secondly, it is easy to see that electromagnetic methods have many economic advantages in different situations. As told by Unsworth, in 2005, ‘‘Early efforts realized that MT was potential tool for imaging conductive sedimentary rocks beneath thrust sheets of more resistive rocks such as carbonates, volcanics, and basement cored overthrusts’’ (p. 35). Besides, he adds that newly improved MT devices are portable and computerized in all duty on the same page. Another advice on the same page is that the new devices could be transported with two people from a position to another, in support of the ability to make records without a person. It can be clearly seen that the important explorations such as sedimentary basin explorations could be handled successfully by two people in short time. Moreover, topography effect on the data is nearly zero and this makes topography correction and layering modelling unnecessary (Auken et al., 2006, p. 1). Besides, as mentioned by Gerkens, in 1989, on page 605, the price of the field explorations will be relatively economic if the field of exploration is wide spread enough. In addition to these, Armah, (n.d.) supports under the need of high sampled data of shallow surface, E.M. measurement devices are easy to carry even as a bag (para. 11). He attaches that, in such a case where there is need for VLF-E.M. methods, electromagnetic signals broadcasted from radio antennas settled before, in addition data collecting is very fast and information collected are better than others in meanings of depth (n.d., para. 13). These are the confirmation of the cheapness of the methods in contact with the speed. Additionally, as told by Campbell & Fitterman (n.d., p. 6), electromagnetic surveys are good in acid mine drainage (AMD) explorations for time saving and economy. In addition to that, they indicate in wide range exploration cases, price of the airborne E.M. surveys will be cheaper than the direct surveys on the area (p. 4). Also, as reported by De Vos et al. (1997), when seismic, DC, TEM and VLF are matched for the special situations for searching AMD, VLF is the best in time and price conditions (Campbell & Fiterman, n.d., p. 4). At last, According to Unsworth (2005), on page 38, when making petroleum surveys, there is large variety in depth penetration and good alternatives in electromagnetic exploration methods (See Table 1). As shown before, in relation with the abilities of being fast, easily transportable and relatively good processing, methods are economically advantageous.
Third, electromagnetic methods’ easy way of application or surveying provides the ability of being user friendly. As reported by Unsworth, in 2005 (p. 34), E. M. methods could be applied to different underground objectives such as capable reservoirs and/or origin rocks. On the same page, he adds that some applications results may give an idea about the existence of hydrocarbons. Also, theoretically, time based surveys or frequency based surveys are the same, but effects to the environment are not the same and this provide important benefits for one to other (USGS, 2004, para. 2). Another source point out that all geophysical methods are getting improved (Strack, 1992, p. 3). Transient EM method is the best within all due to it is easy to use and it is matching the way of processing of the seismic operations, which improved previously (Strack, 1992, p. 3). On the other side, as Strack (1992, p. 2) reported between the years 1983 and 1987 many important hydrocarbon reservoirs had been explored. In the same page, he adds that in some areas such as Brazil, Columbia and North Yemen, electromagnetic methods are advantageous to show capable reservoirs. In collaboration with the knowledge of high quality data collected at intervals from 4 to 15 meters which is related with flight route and operations more than 5 frequencies of data could be collected for overlaying underground basement interpretation of this, which provides high quality information about the substructure (USGS, 2004, para. 3). In addition to that ‘‘EM techniques can be used to detect buried metal in urban settings and to map conductive geological materials as an aid to classical geological investigations’’ (Armah, n.d. para. 10). Additionally, when the subject is low resistive underground layers, multi-frequency electromagnetic methods and particularly TEM are the best methods for the studies (Campbell & Fiterman, n.d., p. 5). In short, properties such as easy use and applicability and easy processing are all in electromagnetic methods.
Finally, related with the applications on the different problems, there are no doubt electromagnetic methods will have a good future. As mentioned by Strack (1992, p. 3), even it is clear to see the requirement to the E.M. methods is high, implementment and fitting to the other geophysical operations will occupy scientists for some time. On the same page, adds that by reason of easily application to the surveys and parallelism to the formerly produced imaging techniques of the seismic, the E.M methods are the best of the improving geophysical methods. In addition to that, the recently developed exploration way will provide new capability to the E.M. exploration surveys which are more realistic and predict improved modelling and calculations for mining problems (U.S. Department of Energy, 2004, para. 5). And E.M. exploration way of deep structures, and Magnetotelurics advanced in hydrocarbon reservoir detecting because of the fast progress made in signal acquisition correction and modelling (Unsworth, 2005, p. 34). Besides, Unsworth reports that electromagnetic methods are quickly advancing in the area of hydrocarbon detecting in open seas and oceans (2005, p. 37). On the same page, adds in the future with the improvement of electromagnetic methods with in connection with borehole sounding it can provides better information. As a conclusion to these in locating and data collecting, electromagnetic devices are useful to explore underground locations of the high conductive bodies of mine wastes (Campbell & Fitermann, n.d., p. 7) and newly found device technology and signal corrections can provide collection of data from airborne surveys as useful as field collected data (Auken et al., 2006, p. 1). As indicated above recently improvements and new application fields are indicating that the future of the electromagnetic methods is open.
In conclusion, electromagnetic methods are providing benefits in exploration studies in meaning of time, effort and money. Also, the brighter future of the methods is a very important aspect. Exploration and prospecting abilities of the methods are good in many situations. The benefits of these abilities are invaluable because they provide non-destructive or non-invasive to the study area and are suitable to all purposes. In addition, transportation and data collecting properties are making works easier for E.M. methods. Furthermore, development ways in many conditions are promising about the future of the methods. Under the conditions of this knowledge, electromagnetic methods are the bright future of the underground exploration studies.
