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Views from space help oil prospectors see deep underground   This fly-through covering 500 square kilometres of west central Algeria illustrates the massive amount of varied topographic and geological information that satellites can provide in order to more effectively pre-plan a seismic survey campaign for oil and gas exploration. It begins with a space-derived Digital Elevation Model (DEM), used for assessing gradient and hence accessibility and safety – note the high limestone outcrop on the east side of the image. Next comes an enhanced visible image from Landsat data showing ground cover, useful for overall planning. After that appears an ERS-based guide to ground roughness, crucial for good seismic coupling. The roughness shown here corresponds to the weathered limestone outcrop. Then comes a combination of bands highlighting vegetation, which can be linked to buried water channels that can degrade seismic signals. Next comes a chart of short-wave infrared (SWIR) lithology, highlighting the limestone outcrop in red. Thermal infrared (TIR) can also be utilised to study buried mineral deposits.
Out of these and other potential satellite inputs can come relevant outputs such as this image showing hard rock data quality based on dip, roughness and the presence of limestone. The final image predicts soft rock potential problems – soft rock can cause vibration trucks base plates to sink into it, or absorb part of the seismic signal.  Seismic crew camp in the Middle East. The company WesternGeco has been working with ESA to investigate the usefulness of satellite imagery in pre-planning seismic survey campaigns of remote regions in the search for oil and gas reserves.  Seismic survey crew deploying geophones in the Middle East. Satellite images are being used to pre-plan the optimum positions of geophones as well as vibrator trucks in order to obtain the best possible information on subsurface characteristics.   Problems in coupling the vibrator baseplate to the ground due to uneven contact or terrain that is too hard or too soft leads to degradation in seismic signal quality. Use of satellite imagery enables enhanced preplanning of a seismic survey campaign, potentially saving time and money.  Inaccessible rough terrain in North Africa. Seismic surveys have to be carried out in some of the remotest territory on Earth. Satellite imagery can deliver valuable advance information on surface - and also subsurface - conditions.  Surface characterisation in basalt areas. This dense rock causes a lot of data distortion during seismic surveys but the presence of basalt can be known in advance using satellite instruments looking in particular in thermal infrared bands - underlying basalt layers radiate thermal energy strongly.  Release date: 10 November 2010 |