Scientists and mining activists need to have a wide vision of earth and its formation in order to use this valuable data for better use of mineral deposit, underground water, oil and gas. For this reason, finding a comprehensive method which covers more details about an area, is too important. Nowadays, there are so many techniques for achieving useful information about earth layers.
Alongside with other geophysical methods that try to study various aspects and characteristics of a region without direct observation and have their own advantages and limitations, Electromagnetic method(EM) as a method which works with a time varying electromagnetic field source, analyzes layers with the aid of frequencies. The important point in this method is following behavior of transmitted frequencies to the earth and the received ones in order to realize the area construction and characteristics.
BEM technology is a unique and creative geophysical technique that investigates subsurface structures by analyzing the reaction of layers components to the electromagnetic waves in frequency domain. This technique helps researchers to perform water exploration, metallic and nonmetallic exploration, fault detection and to identify any anomaly that exists in subsurface in both shallow and deep parts, all around the world.
Using BEM approach gives a more clear understanding about earth layers and that’s a way to have an efficient and successful exploration. This technique enables researchers to study in all metallic, non-metallic and even playa areas. In places with hard accessibility like mountains that are dangerous for human to reach or in complicated regions, BEM as a portable device is a helpful choice. BEM airborne device can be used in such situation and researchers can guide it by software in different complicated topographies. On the other hand it has its own transmitter which allows investigators study on different frequencies each time of the day as they wish.
A great core value of this method is that according to performing analytical solution of the wave equations it is possible to reach data about the dielectric coefficient and in some cases estimate material type which is something more than common EM techniques achievement. The amplitude, phase, and polarization changes of the reflected waves are recorded in the BEM receiver. BEM used the innovative approach for inversion step which help to achieve the most correct solution for wave equation. Although other methods study the frequencies one by one, in BEM technology, wave packages are used based on the type of study area and target.
This method can record data in area with rough topography and determine zones with fractions, joints and gaps. Estimation the amount of metallic impurity and sending numerous frequency simultaneously are the other benefits of BEM method.
As it is mentioned above, BEM device consists of a transmitter and a receiver which work in broad band frequency range (Broad band Frequency Domain Electromagnetic Device). Of course they can also work in time domain too.
Transmitter can transfer several frequencies simultaneously. It is a point that makes it possible to analyze received data in several frequencies which belong to different depths and after that comparing results with each other can help researchers find a better vision of what’s going on, in different layers.
BEM transmitter is 14 kg and its 50*50cm receiver has 10 kg weight. The NS for transmitter is 800 and for receiver is 1200. The receiver is high sensitive (-140db) which is able to work with frequency range from 100 Hz to 40 KHz and separate subsurface layers based on resistivity. As well as being sensitive to nonconductive layer, it is able to increase power of intensity to investigate deeper sections.
BEM method can produce the results of 3 methods: (IP) Induced Polarization, Magnetometry and long range weak field measurements and on the other hand, it is capable of matching with other EM devices. Thus, it is an effective method for identification of types of minerals, their shape, the depth of bulk and layer recognition. This method by reducing procedures length and cost, saves money and time. Besides, being optimum and efficient, BEM let researchers study geophysics exploration in detail and accurately.
Working on projects based on BEM method is following by BEM Technology Group. For example, designing and developing airborne device to perform airborne geophysical surveying with the capability of loading more than 40 kg for large scale projects and for regions with rough topography which footborne surveying is impossible or very hard to perform and there are human hazard such as existence of mountain with rough topography or swamp. The other example is designing the new CSEM setup to achieve the deeper layer in marine and land surveying which its first generation design has a novel approach in sending and receiving EM signals. This new device has a good resolution in both deep layer and shallow depth.
For more details about these projects follow our next papers and news.