For the past two decades or so, remote sensing satellite technology has been widely used by the petroleum industry to support exploration in both frontier and mature areas. The application of this technology covers a wide range of geological and logistical aspects of the petroleum sector including:
reconnaissance geological mapping of large areas,
detailed mapping of prospective structures,
delineation of fractured related reservoir trends,
direct detection of surface alterations and vegetation changes related to oil seeps,
logistical application associated with the collection and planning of seismic data, and
environmental monitoring of petroleum related activities.
Radar imaging systems have proven to be excellent surface mapping tools in temperate and tropical areas because they are sensitive to variations in topography and surface roughness, and thus are capable of imaging the topographic expression of structures which are completely obscured by vegetation and other surficial material. Moreover, images can be obtained through heavy cloud cover due to radar's longer wavelength.
The shadow effect which results from radar's active nature greatly enhances the surface expression of structures on the image. This effect can be maximized by carefully selecting the beam alignment to coincide with preferred structural orientations. In addition, images over the same area with different incidence angles and same or opposite look directions can be used to obtain stereo images which improve the structural mapping capabilities of radar.
The advantages of radar imaging systems as compared to passive imaging technology (such as the sensors on the LANDSAT and SPOT satellites) can be seen in Chevron's exploration attempts in the Sumapaz Area of the Magdalena Basin in Colombia (Figures 1a and 1b). LANDSAT images of the area without significant cloud cover were difficult to find. The best of these images is shown in Figure 1a and the corresponding RADARS AT image is shown in Figure 1b. Not only does radar defeat the cloud cover problem, it captures, in much greater detail, the topographic expression of the structures.
Figures 1c and 1d illustrate the benefit of using radar systems in areas with more subtle structures, showing a comparison between imaging technology and radar images over the mildly deformed region of the Canadian fore-foothills. Note that the imaging technology used in this area is very flat, showing no topographic relief, whereas the shadowing effect of radar enhances the topographic expression of subtle elongated anticlines which form significant hydrocarbon traps in the area.
Successful application of radar imaging systems for geological exploration has been achieved with airborne synthetic apeture radar (SAR) surveys. However, airborne surveys suffer from two main shortfalls. First, the surveys can become prohibitively expensive when used as regional reconnaissance tools. Second, airplane access to remote or politically unstable areas is problematic.