The objective of the panel was to evaluate and discuss recent theories and research results concerning the origin of oil and gas in source beds, the mechanisms and timing of expulsion of oil and gas from source beds, and the alteration of oil and gas in reservoirs. The difficult problem of correlating petroleum with its parent source bed and source material was also considered. Emphasis was placed on time and temperature relations in a geologicalgeochemical perspective.
Each of the Panel papers is concerned directly or indirectly with one or more of the seven criteria that are essential for commercial oil and gas fields. These criteria are effective source beds, migration paths and carrier beds, traps, reservoirs, seals, proper timing, and preservation or sustained protection after entrapment.
Dr ERDMAN treats the subject of the genesis of oil and gas in the preparatory stage, emphasising the importance of abiogenic oxidation; his study is concerned primarily with effective source beds. The author stresses the importance of abiogenic oxidation as a negative factor in petroleum generation; abiogenic oxidation constitutes a competitive demand on the available organic hydrogen, thus imposing a limit on the ultimate petroleum yield.
Messrs DEMAISON and SHIBAOKA investigate the genesis of hydrocarbons from kerogen which is deficient in hydrogen; thus their study pertains to the problem of effective oil versus gas source beds. The authors conclude that hydrogen-poor kerogen with H/C ratios such as occur in vitrinite is incapable of generating significant quantities of crude oil at any temperature.
The subject matter of the paper by EVANS et al. encompasses all seven essential criteria. The authors conclude from their study that pressure seals play an important role in hydrocarbon migration and accumulation. Other important conclusions are that structured, land-derived organic matter, requiring a high degree of maturation, may have been the source material for the oil, and that late compaction drainage enhances the prospectiveness of the mixed compaction facies where 90 % of the reserves have been found.
Professor TISSOT and his colleagues concentrate on the timing of generation and primary migration in a number of geological provinces; they also relate timing of migration to seal, reservoir and trap development, and make some observations about preservation of hydrocarbon accumulations through geological time. Additional evidence is presented in support of the interpretation that most petroleum accumulations now in existence were formed during the Cretaceous Period and Cenozoic Era.
VAN DER WEIDE and his co-authors focus on the factors which can affect protection of petroleum