- ©2002. AAPG/DEG
The oil lakes in southern Kuwait have accumulated oil that was spilled during the 1991 hostilities and have been exposed to processes of surface degradation for the last decade. Long-chain normal alkanes are abundant in these oils, showing that biodegradation has not been a major factor, whereas the absence of most compounds with less than 10 carbon atoms suggests a significant role for evaporation. Evaporation has been simulated in laboratory experiments at 25, 30, 40, and 50°C and compositional changes monitored by taking samples periodically for gas chromatographic analysis. Evaporation is initially rapid but slows through time, and ultimately, most compounds with less than 10 carbon atoms are lost. For a given carbon number, loss proceeds in the sequence: normal alkanes> branched chains> naphthenes> aromatics (which is the opposite of water washing). GCMS data for hopane and sterane biomarkers confirm that oil in the lakes is derived from the giant Burgan oilfield and also show that these biomarkers are not affected by evaporation in either nature or the laboratory. Analysis of sulfur compounds using GC-FPD showed that oils exposed in the lakes were photo-oxidized and had reduced concentrations of benzothiophenes and increased volatile sulfur compounds. A loss of volatile hydrocarbons from the free surface leads to compositional layering unless the oil is well mixed by convection or diffusion. In experiments to monitor the development of layering, low molecular weight compounds were rapidly lost from the surface, and a steep compositional gradient developed. The formation of a devolatilized, viscous surface “skin” tends to make evaporation a self-limiting process and also has significance for the design of sampling protocols in environmental forensics.
Ahmed BuFarsan received a B.S. from Missouri (Rolla) and a Ph.D. from the University of Tulsa in 1999. Since then, he has been an Assistant Professor at the Kuwait Applied Public Authority. Dr. BuFarsan is a member of the Environmental Society of Kuwait and is completing a book on the Petroleum Geology of Kuwait.
Colin Barker received a B.A. in chemistry and a D.Phil. in geology from Oxford University and is the McMan Professor and Chairman of the Geosciences Department at the University of Tulsa. He worked for Exxon Production Research before joining the faculty at the University of Tulsa in 1969. Dr. Barker has been an AAPG Distinguished Lecturer (1980–1981), a Matson Award winner (1978 and 1982), and chairman of AAPG's Visiting Geologists Program (1996–2000). His research interests include organic geochemistry, ultradeep gas, and anomalous subsurface pressures.
David A. Wavrek is President of Petroleum Systems International, Inc., a company that integrates geochemistry, geology, and engineering to solve petroleum exploration and development problems. Dr. Wavrek received his Ph.D. from the University of Tulsa (1992), where he developed quantitative geochemical techniques. Since the mid-1980s, he has been conducting geochemical and petroleum systems analysis throughout the world (30+ countries) for clients that span mega-majors to independents. He has served as a continuing education instructor for the AAPG (2000– 2002) in the disciplines of petroleum systems and reservoir geochemistry.
Mohammad A. Al-Sarawi is the Chairman and Director General of the Environmental Public Authority (EPA), Kuwait. He has also been an Associate Professor of Geomorphology in the Department of Geology at Kuwait University since 1993. After a B.S. in Geology and Chemistry from Kuwait University (1975), he received a M.S. from Ohio (1978), and a Ph.D. from South Carolina (1980), both in geomorphology. Dr. Al-Sarawi specializes in geomorphology, environmental geology, and coastal zone processes. He is a member of AAPG and an editor of the Journal of Technology.