The application of remote sensing technology continues to expand from the first Landsat images of the early seventies to the wide range of satellite data products available today. The oil and gas industry has been in the forefront in using satellite imagery to assist in the identification of promising exploration areas.
      In particular, radar data has always played a major role in the surface geologic interpretation of extensively cloud-covered areas. Synthetic Aperture Radar (SAR) satellite systems such as ERS-1 have made this data more accessible and affordable. Future radar satellites such as Canada's RADARSAT (which will be launched in September 1995) will also substantially increase the amount of SAR data available to the oil and gas industry.
      Spectra Resources Inc. (SRI) is a Houston, Texas based consulting firm that specializes in the geologic and environmental applications of a wide range of remotely sensed data. In a recent study, SRI used satellite imagery to map and analyze a part of the Andean frontal fold belt of Ecuador. The impetus for this study was to aid oil and gas companies in selecting exploration drilling areas being offered by the Ecuadoran government in the seventh licensing bid round.
      Tight deadlines for bid submission are a typical feature of such rounds, and many international areas lack accessible regional geologic data. Utilizing satellite imagery to rapidly construct maps which portray a consistent interpretation of the regional surface geology and structure makes it an ideal tool in the bid evaluation process.
      Both ERS-1 radar and Landsat TM images were used in mapping the approximately 50,000 square kilometers contained in the nine exploration blocks (see inset box in Figure 1) up for bid. ERS-1 was especially useful in enhancing structural features particularly in areas of low relief and providing data in this cloud-prone region.
      "Using ERS-1 and Landsat imagery is a very cost-effective way to help analyze the hydrocarbon potential of these possible exploration areas. This is especially important for smaller and mid-size independents who are becoming more involved in international exploration," said Walter Tomlinson, SRI's vice president.
      SRI focuses its interpretation efforts on creating surface geologic maps as opposed to simple lineament and geomorphic anomaly maps. Map sets are constructed from bedding orientations and stratigraphic distributions interpreted from the satellite imagery. This forms the basis of the standard geologic map presentation (Figure 1). The second step is producing the surface structure formline map (Figure 2) which uses interpreted dip and fault information for control. This map portrays the structural configuration in the form of a contour map, which is familiar to most geologists and geophysicists. The structure formline map allows structural relationships between the surface features to be easily discerned and can aid in interpreting fault orientations on a regional seismic grid.
      Figure 3 shows a portion of a Landsat TM image located in the Oriente region of Ecuador. Figure 4 is a corresponding ERS-1 radar image of the same area. Aside from the obvious cloud-penetrating ability, ERS-1 enhances the signature of the geological structures located in the topographically flat jungle. Faults with transverse motion can be difficult to interpret from a regional seismic grid. These cross-trending faults are often important factors in the structural development and hydrocarbon entrapment in an area, and are generally easily defined utilizing satellite imagery, especially using radar's capability to enhance low relief features.
      With the growing emphasis on environmental concerns, there is a need for environmental base line maps. These are produced from satellite imagery and present an accurate depiction of surface conditions before the start-up of exploration activity. Interpretation of archive satellite data can establish the rate of change for sensitive aspects such as deforestation. Multitemporal satellite data can also be used to monitor activities within sensitive areas throughout the exploration and development phases.
      "Our goal is to produce maps that provide another layer of information to help explorationists effectively evaluate large areas for their hydrocarbon potential," said Tomlinson. "Satellite imagery contributes significantly to providing this valuable product as well as providing a means of monitoring the environment."

About the Authors:
Sylvie Scantland is marketing manager, special projects of RADARSAT International and can be reached at 613-238-6413 for more information about ERS-1 SAR products.
Robert Barton is president of Spectra Resources Inc. (SRI) and may be contacted at 713-974-6061 for more information on SRI. The ERS-1 imagery used in this study was provided by RADARSAT International.

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