Abstract: Remote Sensing Technology in Support of Geophysical Operations, Yemen

James M. Ellis, Robert J. Rossetter

Chevron International (Yemen), Ltd. concluded a production sharing agreement for the Shabwah Gardan Block in January, 1991, and initiated an exploration program. This area is characterized by varied terrain consisting of relatively low-relief desert in the west and a large, flat high plateau in the east bounded by towering cliffs and deeply incised drainage. The work program included seismic and gravity data acquisition and regional and detailed geologic mapping, all supported by remote sensing technology. Prior to this application of remote sensing technology, only small-scale basemaps and topographic maps (1:500,000 scale) of the area were available.

Landsat TM data (30 m ground resolution) were digitally integrated with a black and white, high-resolution (10 m ground resolution) SPOT satellite image to produce a remarkable color composite capable of enlargement to 1:25,000. The colors on this TM/SPOT image were easily correlated with stratigraphy and terrain conditions (especially vehicular accessibility), enabling field crews to plan their routing across this rugged terrain in advance. However, detailed planning was limited because a reliable topographic map was not available. To acquire the necessary topographic map, Chevron International (Yemen), Limited ordered new, overlapping satellite imagery from SPOT Corp. and initiated a GPS surveying program. The stereoscopic SPOT images and 11 GPS ground control points were used to cr ate a digital elevation model (DEM) with a 10-m grid that covered about 50 × 100 km in area. Topographic maps were generated from this DEM with scales varying from 1:100,000 to 1:25,000 and contour intervals from 50 to 10 m. The topographic maps were most useful for regional planning and field operations. Large-scale maps (1:25,000) with 10 m contours required careful implementation because the algorithm that generated the DEM displayed steep, near-vertical cliffs as rounded features.

As required, images, basemaps, and topographic maps were delivered to the field during the first year of the exploration work program. This project demonstrates that timely and practical application of remote sensing technology supports more efficient and cost-effective field operations.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994