Advances in electromagnetic techniques for exploration, prospecting, and monitoring of hydrocarbon deposits
Traditional exploration and prospecting for hydrocarbons (HC) has traditionally been carried out using seismic techniques. At the same time, it is well known that seismic techniques are inefficient in the presence of high-velocity layers (which reduce resolution at great depth), igneous rocks, thrusts within the crystalline basement, and tight limestone. Being sensitive to geological structure, seismic techniques are characterized by low resolution at the level of micro-parameters such as fluid type, porosity/ fracture, and degree of pores HC-saturation. Moreover, technical complications, e.g., highly rugged topography, dense vegetation and object remoteness may make seismic surveys difficult, expensive, or even impossible. Therefore, non-seismic methods are increasingly used in HC exploration and prospecting. In particular, electrical and electromagnetic (EM) methods (magnetotelluric sounding, direct current, time-domain EM (TDEM), induced polarization (IP), controlled source EM, etc.) complement seismic techniques and increasingly replace them (Johansen, 2008; Key, 2012; Zhang et al., 2014; Barsukov and Fainberg, 2015; Berdichevsky et al., 2015, among others). In parallel with EM, the efficient technologies for 3D modelling and inversion (see, for instance, a review paper by Siripunvaraporn (2012) and references therein) and integrated analysis of EM and other geophysical data (see, for instance, a review paper by Bedrosian (2007) has been created. Application of these methods in solving problems of exploration geophysics enabled progression in exploration, prospecting, and devel¬opment of HC deposits (see, for instance, a review paper by Strack (2014) and references therein). Meanwhile, very recent advances in indirect estimating of rock geophysical properties of lithologic reservoirs from electromagnetic sounding data (Spichak and Goidina, 2016; Spichak and Zakharova, 2015, 2016; Spichak, 2017) open up new possibilities related to development of more sophisticated approaches to estimation of the reservoir properties and its potential assessment. The purpose of this paper is to demonstrate the advanced capabilities of electromagnetic techniques in solving a wide range of prob-lems, especially those which seismic surveys are not effective in solving.