A preliminary step to any marine EM survey is to carry out a feasibility study to assess the applicability of the technology.
EM methods are powerful and have a huge potential for reducing exploration risk. However, not all targets are suitable for EM investigations. In the initial phase, PetroMarker assesses the conditions at each specific site to estimate the probability of successful detection of the target(s) of interest.
Since hydrocarbons are more resistive than brine, the critical factor is whether a hydrocarbon-filled target is believed to give a sufficient resistivity contrast compared to the background resistivity. All targets are therefore screened to see if an EM investigation will add any value in the exploration workflow, by reducing the associated exploration risk. In spite of the effectiveness of EM methods to distinguish between hydrocarbon-filled and brine-filled reservoirs, these methods also have some limitations. Examples of challenging conditions for all EM methods are large burial depth, small lateral extent and/or limited target thickness, shallow gas in the overburden, other resistive bodies in the vicinity of the target etc.
Feasibility modeling is normally done using simplified models. In more complex settings, arbitrary degrees of complexity can be added to the model to take local geological phenomena into account. More sophisticated modeling (multi-dimensional) can be performed on request. Modeling is also applied in the interpretation phase, to check the quality and robustness of the interpretation results.