Satellite-based hydrocarbon exploration employing ASTER and fuzzy logic

Despite the known practical applications of remote sensing in a wide range of industries and situations, it has not been used extensively in petroleum exploration, which has relied mostly on geological and / or geophysical surveys. With the advances made in sensing equipment since the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) became operational, extraction of potential indicators such as: surface emissivity, surface kinetic temperature, brightness temperature and surface radiance need to be re-evaluated in the context of petroleum exploration.

Land Surface Temperature (LST) anomalies associated with geothermal activity was used, to determine if petroleum in place, can be the source of thermal anomalies detected at surface, by ASTER. A study area, in onshore Iran, consisting of 53 existing petroleum-rich areas was selected. Twenty (20) ASTER scenes (Granules) covering the study area were provided by National American Space Agency (NASA).

In order to highlight subsurface contributors to geothermal anomalies detected at surface, assumed to be due to underlying hydrocarbons, ASTER images were processed to minimize temperature variations caused by any sources other than the underlying hydrocarbons. In order to assign weight to the role-playing variables according to their degree of influence over the final LST, fuzzy logic was employed, as the main processing approach. In the resulting processed maps, following the removal of all the contributors to LST, the remaining thermal anomalies, which were reduced up to 80% in some areas of the study area, could then be linked to the underlying hydrocarbons. The final results indicate that, even after the influence of all the contributors to LST has been removed, still 67.9% (36 out of 53 petroleum containing areas) of the pixels within the buffer zones of petroleum reservoirs of the study area are considered to be thermally-anomalous.

Continuity of thermal anomalies, in different directions, was also investigated within the buffer zones of each of the petroleum reservoirs, by Variograms. The results of the Variogram analysis indicate that even if the detected thermal anomalies within the buffer zones of some of the reservoir of the study area were not high, the direction of thermal anomalies strongly follow the NW-SE direction, which is the direction along the trend line of elongation axes of petroleum reservoirs. Details of the spatial analysis post LST processing will be reported.

By employing GIS and fuzzy logic, a dynamic model was developed, with variable input data from geology and ASTER, which could be customised and changed according to target area's thermal specifications and characteristics.