ROLF, E. GERALD, Independent, San Antonio, TX, and KENNETH O. SEEWALD, Seewald Energy Company, San Antonio, TX

ABSTRACT: Aeromag Survey Identifies Features Along the Central Texas Overthrust

The use of aerial and ground magenetics in mineral and hydrocarbon exploration has long been an accepted technique. Over the past several years, however, the introduction of the cesium-vapor magnetometer has resulted in a new level of absolute resolution in aeromagnetic surveys. The cesium-vapor magnetometer has both a rapid cycle time (0.25 s sample rate) and an extremely high sensitivity (0.01 gamma), which can detect low-amplitude, but geologically important, micromagnetic anomalies on the order of 0.25 to 0.50 gamma. Compared to the older, but still more commonly used proton magnetometer, the cesium-vapor model is 80 times more sensitive and has a cycle time (sample rate) about eight times faster. The faster cycle time of the cesium vapor model yields significant advantages over p evious magnetometers. These advantages include (1) faster data acquisition, (2) increased number of survey points, (3) lower altitude possible during flight operations ( +/- 300 ft), and (4) improved stability of flight operations. These advantages, coupled with proprietary analytical tools designed to work with the raw data on a bit-by-bit basis for direct profile interpretation, allow the detection of relatively small geologic basement structures in a very cost-effective manner.

The Ellenburger, Marble Falls, Barnett, and dropped formations have yet to be fully evaluated within the Strawn basin of central Texas. Although there is no commercial production to date, there have been significant shows and flaw tests, indicating the opportunity for significant commercial accumulations. Because there are no recognized regionally developed reservoirs, this area has been downplayed as to its potential. These are good geologic and economic reasons for industry to take another look at the Strawn basin.

AAPG Search and Discovery Article #90994©1993 AAPG Southwest Section Meeting, Fort Worth, Texas, February 21-23, 1993.