Forward Modeling of Seabed Logging by Finite Integration and Finite Element Methods

Seabed electromagnetic (EM) modeling for detection of deep target hydrocarbon reservoirs has been a challenge for oil and gas industry. More precise and accurate electromagnetic (EM) methods are required for better detection of hydrocarbon (HC) reservoirs. To overcome this problem, Finite integration method (FIM) and Finite element method (FEM) were chosen for 3D modeling of seabed logging to produce more precise EM response from the hydrocarbon reservoir. EM modelling is used to investigate the total electric and magnetic fields instead of scattered electric and magnetic fields, because it shows accurate and precise resistivity contrast at the target depth of up to 3000 m below seafloor. The FIM and the FEM were applied to our proposed seabed model having an area of 20 × 20 km. It was observed that the FIM showed 6.52 % resistivity contrast at a target depth of 1000 m whereas the FEM showed 16.78 % resistivity contrast at the same target depth for the normalised E-field. It was also found that normalised E-field response decreased as the target depth increased gradually by 500 m from 1000 to 3000 m at constant frequency of 0.125 Hz and current of 1250 A. It was also observed that at frequency of 0.125 Hz, phase versus offset (PVO) showed 3.8 % for FIM whereas 6.58 % for FEM better delineation of hydrocarbon at 3000 m target depth. PVO of electric field gives better delineation of HC presence compared to magnitude of E and H fields.