Induced Polarization Technology
Williamson has a long-standing Cooperative Research Agreement with the US Geological Survey to commercially exploit the USGS marine IP streamer and acquisition patented technology to include redesign and fabrication the USGS marine IP streamer system in order to map and characterize municipal and industrial waste and hydrocarbons on and beneath the seafloor and hydrocarbon plumes in the seawater column. Williamson will manage the overall operational aspects of this effort and carry out preliminary data analysis in collaboration with USGS.
Induced polarization is a subtle surface-effect electro-physical phenomenon first observed in one form by Conrad Schlumberger in 1912. Simply put, he noticed that a resistivity measurement in some places gave different numbers for different frequencies – but not in other places. Under an inducting voltage, charge is adsorbed onto certain mineral grains. When the inducing voltage is removed, a time-delayed charge release can be measured similar to a capacitor bleeding off charge earlier forced onto it by an applied voltage. In modern IP systems, this reaction is typically measured as a phase-shift between transmitted and received signals. The frequency at which the maximum phase-shift occurs has been shown in other studies to be diagnostic of the specific materials being polarized. Hence the name: induced polarization.
Typical IP streamer configuration. Array can be towed in the water column or on the seabed depending on the application. Streamers are constructed to meet customer requirements. Distance between receiving electrodes determines swath width and depth of penetration.
Survey results from a Ilmenite sands survey off South Africa; area covered 4 x 11 km. Orange indicates highest concentration of the ilmenites.
Concentration levels of a particular hydrocarbon at the Wyckoff Site in Eagle Harbor, Puget Sound. The higher phase shift corresponds to a longer decay time of the electrical square wave pulse and therefore a higher concentration of the polarized material. Analysis of lab samples in the area will indicate the type of hydrocarbon. The swath width in this case was ten meters. The array was towed at about two kts.