Magnetotellurics in the Rub al'Khali, Saudi Arabia

Magnetotelluric data were collected as part of a multi-disciplinary exploration program for Paleozoic non-associated gas in the southern Rub al-Khali Basin of Saudi Arabia. Data collection was difficult due to the presence of large sand dunes, but the use of specially developed buffer amplifiers helped to partially overcome the very high contact resistance. Interpretation of data was carried out using 3D inversion, and this images the basement structure well. The post-basement sediments show a local increase in resistivity above a positive basement structure. It is speculated that this might be due to porosity reduction (compaction or facies changes), or to a change in fluid resistivity (salinity reduction or hydrocarbon charging).