Detection and imaging sensitivity of the marine CSEM method

Abstract

We have developed a formalism to systematically study the sensitivity of the marine controlled source electromagnetic method for hydrocarbon exploration, taking into account measurement errors. We utilize error propagation to estimate the data uncertainty, and find that contributions that scale by the transmitter dipole moment give qualitatively different behavior than noise contributions that are independent of the dipole moment. The uncertainty is used in quantitative criteria to determine if a hydrocarbon reservoir can be detected and whether it can be successfully imaged. Our formalism can be used to make detailed feasibility studies incorporating equipment accuracy limitations, and to identify which experimental component that must be improved to ensure overall improvement in sensitivity. The criteria can be applied to identify the limiting factors for detection and imaging of targets with increasing burial depth. We have defined experimental accuracy conditions for next generation CSEM equipment to successfully image a large hydrocarbon reservoir at 5 km burial depth.