In order to reduce risks and costs of exploration newer techniques are constantly being developed. One of the lacuna of seismic surveys is that it provides little data regarding the nature of fluids discovered within structures and cannot easily distinguish between waterbearing and hydrocarbon bearing geological formations. Until recently the only way to identify whether hydrocarbons were present was to drill. Over the last few years O&G companies have begun using controlled source electromagnetic imaging (CSEM) as a key component in their exploration tool kits to complement their seismic data, gain a more complete picture of the sub-surface, delineate reservoirs and reduce the risk of drilling costly dry holes. The technique uses electro-magnetic signals to map the variations in the resistivity of the geological formations below the seabed. The resistivity in hydrocarbon bearing layers is typically between 10 and 100 times greater than the surrounding strata. CSEM uses this contrast in the resistivity between water and hydrocarbons to detect and delineate structures that are likely to contain oil and gas.