Rapid subsea induced polarization detection using CSEM transmitter electrodes

The marine controlled-source electromagnetic method has become a pivotal tool in the exploration of subsea resources, including oil, gas, and metal sulfides. Recent advancements in both methodology and instrumentation have highlighted the benefits of signal amplitude analysis in near-source observations. Despite these developments, traditional exploration techniques continue to rely on a transmitter–receiver separation model, largely overlooking the potential responses at the transmitter site itself. This study breaks new ground by examining the relationship between the potential variations of the transmitter electrodes and the presence of anomalous targets. Introducing the innovative concept of a transceiver, this research leverages existing direct current (DC) theory to conduct COMSOL Multiphysics simulations. These simulations focus on DC potential anomalies related to resistivity and turnoff potential anomalies associated with induced polarization (IP) effects. By applying the Cole-Cole model within the complex resistivity theory framework, frequency-domain simulations were performed to extract frequency-domain IP signals from electrode potentials. The study further correlates these frequency-domain responses with time-domain turnoff responses using the fast cosine transform method. Laboratory water tank experiments utilizing the transceiver to observe graphite and polyvinyl chloride anomalies demonstrated a significant correlation between electrode potentials and anomalous bodies, aligning with theoretical predictions and simulation outcomes. Notably, the IP potential amplitude induced by the graphite anomaly obtained through this method demonstrates a 60 % relative increase compared to the background response. This method can serve as both an independent approach for detecting shallow seabed targets and shows promise as a complementary tool for conventional marine electromagnetic exploration.