KEGS Presents: Understanding and Extracting Airborne IP
Induced polarization (IP) effects observed in airborne time domain electromagnetic (TEM) survey data offer information on the chargeability of the subsurface in addition to conductivity derived from TEM data and have been studied by many. In recent years, airborne IP has gained more interest as a potential product (Kratzer and Macnae, 2012; Kang et al, 2014). A better understanding of the IP process helps us to develop suitable methods to extract and use the IP in airborne TEM. The IP effect is generally weak and obscured in the total TEM response.
As a result, the typical inverse transient associated with IP effect does not always manifest itself in the total EM response. This causes difficulty for algorithms that rely on the inverse transient to estimate the chargeability of the subsurface. In this work, we first examine the Cole-Cole model (Pelton et al, 1978) and consider two types of DC energizing sources: voltage and current. Our goal is to examine the two simple cases to gain insight in the IP phenomenon and thus decide the proper model in studying and computing airborne IP effect.
We then develop a robust method that decomposes the total electromagnetic response into a fundamental (inductive) and a polarization component. We can estimate apparent chargeability from the estimated polarization response. We finally illustrate the effectiveness of this method with field examples.
Presented by: Dr. Tianyou Chen, CGG, Mississauga