Landsat Thematic Mapper Assessment of Oil Lakes and Oil-Contaminated Soils in the Burgan Oil Field, Kuwait

Kuwait’s oil lakes and oil-polluted surfaces were an act of sabotage imposed on the desert environment during the 1990 to 1991 Arabian Gulf War. During the war, Iraqi troops deliberately set ablaze several oil-producing wells and damaged others to allow crude oil to flow freely. The oil formed networks of oil rivers and oil lakes that accumulated around oil wells and in relatively low areas. The environmental criminal act in Kuwait’s oil fields resulted in either the detonation, destruction, or ignition of 798 oil wells representing 87.3% of the 914 producing wells. The breakdown was as follows: 604 (66%) burning oil wells, 45 (4.9%) gushing wells and 149 (16.3%) destroyed wells—neither gushing nor burning. Several oil lakes of various sizes, and covering an area of more than 49 km2, were formed in the oil fields, with the majority in the Burgan oil field. Presently, the affected areas consist of oil lakes; thick, light, and disintegrated tar mats; black soil; and vegetation.

In the Burgan oil field, Kuwait’s largest producer and the second largest field in the world, 515 oil wells were either set on fire or were damaged and allowed to gush. During the ten months of oil fires the Burgan oil field was practically inundated with crude oil and oil mist. In addition, several tons of combustible and incombustible petroleum products were released into the atmosphere. The soot and oil mist eventually settled in the oil fields, urban and desert areas, and in the Arabian Gulf being driven by the predominantly northwest-southeast winds.

This study, which uses satellite imagery to monitor the spatial and temporal changes in the oil lakes in the affected oil fields, is part of a multidisciplinary study being conducted by the Kuwait Institute for Scientific Research to monitor the long-term effect from the oil lakes and oil-polluted soils. Landsat Thematic Mapper (TM) datasets acquired between 1986 and 2000 are used in a time series to monitor the spatial and temporal changes of the oil lakes and oil-polluted soils in the Burgan oil field. In addition the TM thermal infrared band images are used to map changes in the surface temperatures in the Burgan oil field and surrounding areas.

The need to continuously monitor the status of the oil lakes and polluted surfaces is obvious, as they might be an unwelcome addition to Kuwait’s environment for a long time to come. Potential environmental hazards emanating from the oil lakes and polluted soils include:

• Contamination of the local groundwater;

• Contamination of the soil;

• Inhibition of growth of vegetation and wild animals;

• Alteration of the bio-diversity of the contaminated areas; and

• Health risks to both humans and animals.

Given its technical robustness, remote sensing offers an unparalleled technique to study and monitor any surficial, spatial, and/or temporal changes associated with the oil lakes and their environs on a continuous basis. The many advantages presented by using remote sensing in this and other environmental studies/projects include the combination of a synoptic view of the study area, cost-effectiveness, non-destructiveness, relatively high spatial resolution, repetitive data at the same scale for a particular satellite, digital format, availability of satellite imagery, and acquisition of imagery from inaccessible areas without the hindrance of political or security restrictions. The changes in the study area can be recorded in pictorial forms and evaluated in a much more rapid mode that is not possible using any other method. Furthermore, the resilience of the polluted areas can be monitored periodically using satellite images. Such studies, in addition to others, can provide invaluable information to decision-makers, and environmental scientists since Kuwait’s oil lakes are more or less the first of their kind in history.

The first unmanned space satellite designed to collect earth resources data was launched by the United States’ National Aeronautical and Space Administration (NASA) in July 1972. Since then, remote sensing has emerged as one of the most reliable and promising techniques used in different aspects of ecosystem analysis, evaluation and monitoring. Several satellites with different spatial and spectral resolutions are currently available and are used in diverse projects and studies. Landsat satellites have repetitive, circular, sun-synchronous and near-polar orbits. Landsat 5 and 7, which are currently active, cross the equator on their north-to-south bound orbit at approximately 0930 local mean time. The TM sensors aboard Landsat satellites acquire data in seven spectral bands: three visible (0.45 to 0.52, 0.52 to 0.6, and 0.63 to 0.69 m), one near infrared (0.76 to 0.9 m), two mid-infrared (1.55 to 1.75 and 2.08 to 2.35 m), and one thermal infrared (10.4 to 12.50 m). The Landsat TM reflective bands have a spatial resolution of 30 m, whereas the thermal infrared band has a spatial resolution of 120 m. A typical TM scene is 185 by 185 km, and Kuwait is covered in four scenes.

The satellite images were radiometrically corrected and geometrically registered to the Universal Transverse Mercator (UTM) coordinate system and the US Geological Survey map zones 38 to facilitate their comparison and overlays. They were processed further using various image processing techniques to extract the information of interest. Surface temperatures of the contaminated area were derived from Landsat TM’s thermal infrared band 6 and evaluated in a time series. This channel is quantitatively sensitive to temperatures up to 100 C above which the channel saturates and becomes non-quantitative for whole pixel temperature evaluations. During Landsat TM overpass of Kuwait in the mornings, land surface temperatures are low for a particular day and well within the TM band 6 sensitivity range threshold.

Prior to the oil lakes/fires episode, the Burgan oil field was not different from the other sand sheet areas expect the locating of several oil wells and oil producing infrastructures. Other features observed in the satellite images include sabkhas, quarries and urban areas under construction (see Fig. 1). In the third week of February 1991, the majority of the area was transformed into oil fires and pools of oil lakes, tar mats, oil mist, and soot from the burning oil wells. With the help and expertise of 27 fire-fighting companies from different countries, the last oil well fire was extinguished on November 6, 1991 (see Fig. 2). Initially the oil lakes were indistinguishable from the surroundings in satellite Landsat TM images owing to lack of contrast with the surroundings. The features on the surface were oriented in a northwest-southeast manner due the prevalent wind direction, which also resulted in the deposition of a majority of the soot and oil mist in the southeastern part of the Burgan oil field (see Fig. 3).

With time, the soot turned the underneath soil black, smaller and shallower oil lakes dried up to form tar mats, which continue to disintegrate gradually under the harsh weather conditions. Some of the oil lakes were concealed by a veneer of sand and could not be observed from the surface. Furthermore, some of the oil migrated to new locations as a result of occasional strong rainstorms and flash floods (see Fig. 4). A barbwire fence was constructed around the oil field in 1994. Consequently the areas inside the oil field had more vegetation in the form of grass and shrubs compared to the denuded outside areas, which are overgrazed by camels, sheep and goats. Kuwait experienced higher than average rainfall between 1992 and 2000 and that enhanced the vegetation growth in the protected area. (see Fig. 5). In spite of the large quantities of soot that were deposited, some of the contaminated areas were able to support plant growth in the presence of adequate water. Because of the high rate of sand movement in the area the soot/black soil continue to disappear from the surface (see Fig. 6). The total area of oil lakes mapped from March 1995 TM imagery in the Burgan oil field was 35.45 km2. In 1998 the area observed from satellite imagery was 24.13 km2. The area of the oil lakes observed on the surface from satellite images continues to decrease. However, the contaminants remain in the soil and pose environmental problems to the underlying aquifer. In the Burgan oil field the underlying water is either brackish or saline and is only used for irrigation purposes.

The land surface temperature distribution in the Burgan oil field was not complex and quite uniform in the desert and oil field areas before the 1991 oil fires (see Fig. 7). The lowest temperatures were observed mainly in the urban areas. Because of the greenery and building materials, the surface temperatures were in general 2 to 6 ºC less than the desert sand sheet. In the desert areas, the temperature differences among the surface materials were less that 4 ºC, and that could be attributed to the soil types and the emissivity of the materials. Sabkhas with surface salt encrustation displayed high temperatures than the surrounding areas.

After the oil fires, the surface temperature distribution in the Burgan oil field area was completely transformed owing to the deposition of soot, tar mats, and oil droplets. Satellite images showed temperature differences of up 16 ºC among the surface materials. Soils that previously had the same temperatures showed a difference of approximately 8 ºC due to the fall out (see Fig. 8)). From the images, areas with relatively thick tar mats and soot displayed a much higher temperature than the surroundings. The barbwire around the oil field introduced another variable to the surface temperature distribution. The corollary was a temperature difference of about 2 ºC across the fence with higher temperatures in areas with relatively more vegetation (Fig. 9). From the satellite images oil lakes displayed relatively lower temperatures compared to the surrounding contaminated soil. The images showed that temperature distribution is useful variable for mapping the oil lakes from the surroundings. The polluted soils consistently showed higher temperature distribution compared to the surroundings.

What are the long-term implications for such drastic temperature variations from the oil lakes and polluted soils? The answers are not quite obvious now. However, it is conceivable that there could be changes in the flora and fauna. Such a prediction can only be supported by long-term detailed monitoring of the contaminated soils and the vegetation in the area.

List of Figures

Fig.1. Landsat TM bands 2, 4, and 7 color composite image of the Burgan oil field, February 4, 1987. The shades of green represent vegetation. The dark circulation areas are sabkhas or salt flat.

Fig. 2. Landsat TM bands 2, 4, and 7 color composite image of the Burgan oil field, April 28, 1991. The red dots denote the location of burning oil wells and black represents smoke and oil mist.

Fig. 3. Landsat TM bands 2, 4, and 7 color composite image of the Burgan oil field, November 14, 1991. Black represents oil lakes, tar mats, soot and black soil.

Fig. 4. Landsat TM bands 2, 4, and 7 color composite image of the Burgan oil February 28, 1993. The shades of green represent vegetation and black oil lakes, tar mats and black soil.

Fig. 5. Landsat TM bands 2, 4, and 7 color composite image of the Burgan oil April 7, 1998. Green represents vegetation and black the location of oil lakes, tar mats and black soil.

Fig. 6. Landsat TM bands 2, 4, and 7 color composite image of the Burgan oil March 2000. Green represents vegetation and black the location of oil lakes, tar mats and black soil.

Fig. 7. Landsat TM-derived surface temperature distribution in the Burgan oil field recorded on February 4, 1987.

Fig. 8. Landsat TM-derived surface temperature distribution in the Burgan oil field recorded on November 14, 1991.

Fig. 9. Landsat TM-derived surface temperature distribution in the Burgan oil field recorded on April 7, 1998.

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