Abstract for SEG Workshop on 3D IP – 2014 SEG Conference: 3D IP Data From Historic IP Arrays With Examples From Porphyry Copper Exploration Available to Purchase

The advent of 3D IP data acquisition is partially due to 3D modeling capabilities to handle alternate array geometries and the quantity of data collected. Modeling algorithms for 3D visualization of traditional pole-dipole and dipole-dipole linear arrays from multiple line grids allowed a tool for integration with other kinds of 3D modeled geophysical data and geologic information from drilling and surface mapping. However, 3D modeling of 2D linear data can generate artificial and misleading anomalies if the modeling is not constrained. An example from the Safford district in Arizona contrasts the results of 2D modeling presented in 3D as compared to two different 3D models generated by different source codes. Before investing in often expensive 3D IP data acquisition, exploration personnel should evaluate traditional IP data acquisition arrays that, in principle, are 3D methods. Two of these are the reconnaissance IP (RIP or VIP) and downhole radial methods. Actually, even the traditional pole-dipole and dipole-dipole linear arrays have a 3D component as seen in countless examples of off-line anomalies. Comparison of RIP and downhole radial measurements with traditional dipole-dipole lines suggest that magnitudes and placement of anomalies from these historic 3D methods agree well with linear 2D results. These empirical data argue that standard 2D acquisition is giving 3D information as are the RIP and downhole radial methods. Comparisons of dipole-dipole lines with RIP are shown for porphyry systems at North Silverbell, Dos Pobres and Piedras Verdes. The downhole radial array is compared to a dipole-dipole line taken along one of the radials at a porphyry exploration property in Indonesia.