From Thule to Huli's: Use of Magnetotellurics in Difficult Acquisition Areas

Karen Rae Christopherson

Recent applications Of magnetotellurics have produced results superior to those of earlier years by many improvements in the technology, the application and the interpretation of the method. MT continues to be useful in those areas where seismic acquisition is either difficult or expensive, where the surface inhibits effective seismic penetration, or where the use of MT is cost-effective as a predecessor to seismic.

Improvements made to MT within the last few years include: multi-site acquisition with varied station spacings and omni-directional, low frequency antennae; smaller, higher storage field computers, sensor-box modifications for filtering unwanted signal (such as lightning); post-acquisition re-processing of the data via robust schemes; and faster, larger 2-D and 3-D modeling capabilities.

Within the last two years, MT has been used world-wide for a variety of exploration targets. These include the continued use of MT for mapping subcarbonate plays in Papua New Guinea with on-going drilling. Here, use of seismic is precluded due to thick, high-velocity surface limestone. MT has been used as a precursor to seismic in overthrust regimes in Nevada and Colorado where MT is used to highgrade areas as prospects before seismic programs are acquired. ln Greenland, MT has been used for reconnaissance mapping in large basin environments sub-basalt.

On-going system modifications are being made to provide larger channel systems and future marine acquisition of MT.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California