Abstract: In the present investigation down core variations of Zn and Ni in sediment core from Bay of Gorgan was studied. It should be pointed out that the waters of Bay of Gorgan are brackish due to the entrance of Caspian Sea water into the bay. Therefore, any oil pollution occurring in the Caspian Sea may find its path into the Bay of Gorgan. Inter-relationship amongst various parameters was brought out through correlation coefficients and cluster analysis. The results of the present study reveal that Zn and Ni possess both lithogenous and nonlithogenous sources. The increasing trend of Al towards tope of sediment core is indicative higher erosion in the recent years. Interestingly, concentration of all studied metals increases toward core top that might be indicative of influence of man's activities residing in catchment area of Gorgan Bay and also oil exploration in the Caspian Sea. Further 210 Pb and 137 Cs techniques were used to find out rate of sedimentation. The result of dating is indicative of sedimentation rate between 1.4 to 2.45 mm/yr. based one Pb and Cs activities respectively. INTRODUCTION The Bay of Gorgan is located on the most south-eastern corner of Caspian sea is a significant body of water not only from economic-social point of view, but also for its beautiful sceneries and supporting and sustaining a relatively vast and prominent ecological system of Miankaleh wetland. It is considered as the largest bay of the Caspian Sea with an area of about 400 Km 2 and a maximum length of 70 Km and maximum depth of 5m. The Qarahsoo River is the only important fresh water source flowing into the Bay (Figure 1). It is known that the bays and wetlands are comprised of complex systems involving interplay between various physical, chemical and biological factors (Hutchinson, 1957; Ruttner, 1963; Mortimer, 1941, 1942 and 1971; Sain and Neufield, 1975 and Coker, etal., 1979). Heat alongwith suspended and dissolved substances are factors that can effect the dispersion of trace elements in the waters, and accumulation or mobilization of trace elements in the sediments of Bays (AI-Masri, 2002 and Butman and Bothner, 1998). Trace metals that are derived from lithogenous and non-lithogenous sources can accumulate in the upper 5 to 20 cm of Bay sediments. Such accumulation takes place by biological and geochemical mechanisms (Mortimer, 1942 and 1971; Gorham and Swain, 1965; Mackereth, 1966; Cline and Upchurch, 1973; Farmer, 1991 and Rasmussen, 1994). Upward migration of trace metals may occur through the processes of de-watering resulted from compaction and also unidirectional ion migration; and also to a much greater extent, migration appears to be due to bacterial activity (Cline and Upchurch, 1973 and Coker and Shilts, 1979). Most trace metals tend to enrich in the modern organic sediment in relative to inorganic sediment (Henderson, 1995 and Kettles, etal., 1991). This is probably due to the nature of the metal-organic binding strength and perhaps increased ion-exchange capacity of organic sediments over inorganic types.

Abstract. A new method is presented which provides possibilities to deduce the generation and accumulation history of natural gas from 13C-values of gaseous hydrocarbons. This approach consists of two parts, a new analytical technique and a numerical model. It establishes a direct, deterministic link between the process of thermal hydrocarbon generation, commonly described by chemical reaction kinetics, and the stable isotopic composition of hydrocarbon gases generated by this process. It addresses questions regarding the timing of entrapment, the amount of accumulated gas, the size of the recharge area or the amount of actively producing source rock as well as questions regarding reservoir compartments. In this way reaction kinetic models of stable isotopes in natural gas potentially become a powerful tool in basin simulation studies. isotope pattern caused by generation fractionation while migration fractionation in INTRODUCTION most cases seems to be of minor importance. To describe isotope fractionation during gas The interpretation of the stable isotopic generation we apply first-order reaction kinetic composition of individual components of modeling to analytical data obtained from nonnatural gas is one of the most widely used isothermal, dry, open-system source rock tools to explain natural gas occurrences pyrolysis, on-line coupled with a gas although it still predominantly relies on chromatograph and an isotope ratio mass empirical or semi-empirical relationships. In spectrometer. many cases these relationships allow to decipher from stable isotopes of gas LABORATORY EXPERIMENTS ON components the type and maturity of the GENERATION AND STABLE ISOTOPES corresponding source rock1-3. Only recently, a OF NATURAL GAS more fundamental understanding of the This new analytical technique provides processes affecting the isotopic composition of high resolution insights into the generation natural gas arises, since the principles of dynamics and isotope trends of individual gas chemical reaction kinetics4, molecular components like methane, ethane, propane, modeling5, as well as quantification to and carbon dioxide. These data show that the migration-related fractionation processes6 are isotopic evolution of natural gas components increasingly taken into account in natural gas may exhibit much more complex patterns than studies. predicted from the empirical relationships. Thus, during non-isothermal laboratory Based on pyrolysis experiments with pyrolysis methane, the most important prominent gas-prone source rocks (coals) and constituent of natural gas, during its generation on the theory o

Abstract. Recent advances in petroleum geochemistry include a better understanding of hydrocarbon migration, new concepts such as deposition of organic matter and organic facies, and wide use of standard tools, mainly derived from pyrolysis. Moreover, the rapidly expanding impact of geochemical modelling has promoted a new interdisciplinary and quantitative approach to using earth sciences in petroleum exploration. Major oil companies make systematic use of geochemistry during all steps of exploration: evaluating petroleum potential, possible size of accumulations and nature of expected discoveries (oil, condensate, gas) before acquiring new leases or participations; following up wells being drilled; preparing and updating basin compilations. The role of geochemistry has changed from a qualitative to a quantitative risk evaluation tool in exploration. New advances are expected in understanding various aspects of hydrocarbon generation and accumulation, such as timing and efficiency of migration, and modelling of the related processes. Finally, the training of future ‘explorationists’ is an important problem, since the proper teaching of petroleum geochemistry is not commonly available. Résumé. Les progrès récents en géochimie du pétrole comprennent en particulier une meilleure compréhension d e la migration des hydrocarbures, de nouveaux concepts comme la sédimentologie de la matière organique et les faciès organiques, et un large usage des analyses standardisées, surtout dérivées de la pyrolyse. Bien plus, l'impact grandissant des modèles géochimiques a ouvert la voie à une nouvelle approche interdisciplinaire et quantitative pour l'utilisation des Sciences de la Terre en exploration pétrolière. Les principales compagnies utilisent systématiquement la géochimie à tous les stades de l'exploration: pour évaluer le potentiel pétrolier, la taille possible des accumulations, et la nature des fluides attendus (huile, condensat, gaz) avant d'acquérir de nouveaux droits miniers; pour le suivi des forages en cours, pour préparer et mettre à jour les synthèses de bassin. Dans tous les cas, le rôle de la géochimie est passé d'une évaluation qualitative à une évaluation quantitative du risque en exploration. D e nouveaux progrès sont attendus dans divers domaines: ils concernent en particulier l'époque et l'efficacité de la migration et la modélisation de ces processus. Enfin, les problèmes de formation sont très importants, car il n'existe que peu d'enseignements réguliers de géochimie du pétrole. 1. INTRODUCTION is, after all, fundamental that all of the three essential aspects of petroleum exploration, namely (1) source The rationale for using geo

Abstract. Isotopic studies of rare gases, CO2, N2, sulphur compounds, and water have elucidated many phenomena in natural gas occurrences including origin, maturation, migration, radioactivity, thermochemical and biological conversions, as well as intrusion of surface water and the atmosphere. Certain generalizations have evolved. Lower temperature shallow reservoirs with surface water penetration and biological activity contrast markedly with the thermochemical reactions of deeper occurrences. Shallow reservoirs are characterized by large kinetic isotope effects whereas much smaller kinetic isotope effects and possibly exchange phenomena are identified with deeper high temperature environments. Aside from problems which arise in interpreting the isotopic data, the challenge is to decipher the information that the non-hydrocarbon constituents provide about the geochemistry of natural gas per se. This, in turn relates to whether a given constituent was geochemically independent or originated from the same source(s) as the gas and the extent to which there were interactions during maturation and migration. Basic principles, examples from the literature, and recent data from gas occurrences of western Canada illustrate the potential information which isotopic analyses of non-hydrocarbon constituents can provide. Résumé. Les études isotopiques des gaz rares, CO2, N2, composés du soufre, et de l'eau ont permis d'élucider de nombreux phénomènes existant dans les accumulations de gaz naturel, tels que l'origine, la maturation, la migration, la radioactivité, les conversions thermochimiques et biologiques, et l'intrusion de l'eau de surface dans l'atmosphère. Certaines généralisations ont évolué. Les réservoirs peu profonds à basse température avec pénétration d'eau de surface et une activité biologique, contrastent fortement dans leurs réactions thermochimiques avec les accumulations plus profondes. Les réservoirs peu profonds sont caractérisés par des effets cinétiques isotopiques importants, alors que des effets cinétiques isotopiques beaucoup plus faibles et des phénomènes possibles d'échange se rencontrent dans des milieux plus profonds à haute température. A côté des problèmes d'interprétation des données isotopiques, la difficulté est de déchiffrer les informations fournies par les constituants non-hydrocarbures sur la géochimie du gaz naturel luimême. Ceci à son tour dépend du fait qu'un constituant donné était géochimiquement indépendant ou bien engendré par la même source que le gaz, et de la mesure des interactions pendant la maturation et la migration. Les principes de base, des exemples pris dans la littérature et des données récentes sur des gisements de gaz de l'Ouest du Canada mettent

Abstract. Since 1973, 11 exploratory wells have been completed on the Labrador shelf. Four of these are significant gas discoveries. The gas occurs in a Visean dolomite, a Lower Cretaceous fluvial sand and a marine Paleocene sand. No discoveries were made in 5 wells drilled off southwestern Greenland. The discoveries and prospects are on structures or stratigraphic traps or combinations of the two, associated with horsts and grabens of the initial rifting stages. Organic matter of marine origin is approximately 3% in most of the Cenozoic and less in the Paleocene and Upper Cretaceous. Terrestrially derived organic matter dominates the Lower Cretaceous. The best prospects may occur within the Mesozoic-Cenozoic sections above Late Jurassic to Cretaceous fracture zones which appear to be present in the continental crust at right-angles to the Labrador coast. Heat flow from these zones may have matured the organic matter in the Sediments more favourably than elsewhere. Résumé. Depuis 1973, on a terminé 11 puits d'exploration sur le plateau continental du Labrador. Quatre ont été des découvertes importants de gaz. Le gaz est piégé dans une dolomie Viséenne, un sable fluviatile Crétacé inférieur, et dans un sable marin Paléocène. Les cinq puits forés au large du sud-ouest du Groenland ont tous été secs. Les perspectives et découvertes sont situées dans des pièges structuraux, stratigraphiques ou mixtes, associés à des horsts et à des grabens d'un début d'ouverture océanique. I1 y a 3% de matière organique d'origine marine dans le Tertiaire et moins dans le Paléocène et le Crétacé supérieur. La matière organique d'origine continentale est abondante dans le Crétacé inférieur. Les meilleures perspectives paraissent se placer dans le Mésozoïque-Cénozoïque, au dessus du Jurassique à Crétacé Supérieur, le long des zones de fracture, qui semblent se situer dans la croûte continentale, perpendiculairement à la côte du Labrador. Le flux calorifique, venant de ces zones, peut avoir été un facteur plus favorable qu'ailleurs à la maturation de la matière organique dans les Sediments. 1. INTRODUCTION The first industry exploration in the Labrador Sea began in late 1966 by the low-level flying of approximately 15 O00 km of line with a high sensitivity caesium vapour magnetometer on the Labrador shelf. This survey resulted in the approximate delineation of the principal areas of thick nonmagnetic rocks. In 1967, dredging and gravity piston coring was conducted with the aid of air gun reconnaissance. This proved the presence of Cenozoic and Mesozoic clastics. Conventional reconnaissance seismic surveys were started in 1968 and the first prospects were ready for drilling in 1971, when the Leif E-38 well (near the subsequent Leif M-48) was suspended at 1088

Abstract. This paper considers the exploration significance of developments in organic and other areas of geochemistry. The utility of geochemical criteria in early reconnaissance and developmental stages of exploration of sedimentary basins for crude oils and natural gases is discussed and illustrated with case histories. References to surface (land) and marine hydrocarbon survey technology, source bed determination, hydrocarbon maturation and migration phenomena, post-migration alteration and transformation, correlation processes and nonconventional hydrocarbon sources are made. Advances in spectroscopic techniques such as high resolution GC-mass spectrometry, nuclear and electron spin resonance, infrared and UV-fluorescence and their relevance in correlation of hydrocarbons with stratigraphic units and reservoirs are discussed. Results of an updated literature review on the theories of oil and gas formation will be presented. The role of stable isotopes of carbon, nitrogen, and sulphur in elucidating problems in evolution migration and alteration of petroleum is treated. Hydrocarbon gases, N-S-O organic compounds, and other elements as proximity indicators of petroleum reservoirs will be evaluated. Résumé. On étudie l'influence des progrès réalisés en géochimie, et surtout en géochimie organique. On discute de l'utilité des critères géochimiques dans les phases de reconnaisance initiale et d'exploration approfondie des bassins sédimentaires pour le pétrole et le gaz, et on l'illustre par la description de cas réels. On fait référence aux techniques d'études de surface des hydrocarbures sur terre et en mer, de détermination des roches-mères, des phénomènes de maturation, de migration des hydrocarbures, de transformation et d'altération après leur migration, des procédés de corrélation, et aux sources d'hydrocarbures non conventionnels. On évoque les progrès réalisés dans le domaine des techniques spectroscopiques, telles que la chromatographie en phase gazeuse couplée avec la spectrométrie de masse à haute résolution, la résonance magnétique nucléaire et la résonance paramagnétique électronique, la fluorescence par infrarouges et ultraviolets, et leur importance dans les corrélations entre hydrocarbures, unités stratigraphiques et réservoirs. On présente les conclusions d'une revue des publications récentes sur les théories concernant la formation du pétrole et du gaz naturel. On traite aussi du rôle que jouent les isotopes stables du carbone, de l'azote et du soufre dans la solution des problèmes de l'évolution, de la migration et de l'altération du pétrole. On évalue également la valeur des hydrocarbures gazeux, des composés organiques de N, S et O, ainsi que d'autres éléments comme indicateu

Abstract According to experimental investigations, all light hydrocarbons present in crude oils including their heavier components are originated from the organic matter of sedimentary rocks. Higher pressure at moderate temperatures is favourable to the formation of petroleum. According to the experimental data and new information on oil and gas composition and distribution, biochemical and then thermocatalytic and thermal transformation of organic matter have led to the formation of hydrocarbons while the subsidence of sedimentary rocks takes place. As seen from the experimental investigations, the primary migration of hydrocarbons is caused by diffusion, transferring of liquids and gases from solution and microbreaks. Oil and gas accumulation under lateral and vertical migration together with water results from the release of hydrocarbons from solution in subsurface waters, as a consequence of changes in physicochemical conditions. by M. F. MIRCHINK, Institute of Geology and Exploration of Fuels (IGZRGI) Azerbaijan Institute of Petroleum Exploitation (AZNII DN) A. A. BAKIROV, Moscow Institute of Petrochemical and Gas Industry V. V. VEBER, All- Union Scientijìc Research Institute of Geological Survey for Oil (VNZGNI) N. B. VASSOEVICH, Moscow State University, Geological Department M. F. DVALI, All-Union Institute of Geology and Exploration of Oil (VNIGRI) S. P. MAXIMOV, All- Union Scientijìc Research Institute of Geological Survey for oil S. N. SIMAKOV, All-Union Institute of Geology and Exploration of Oil (VNZGRZ) V. A. SOKOLOV, Institute of Geology and Exploration of Fuels, Moscow B-312, Fersman str., 50 A. A. TROFIMUK, Siberian Branch of the Academy of Sciences of the A. A. ALI-ZADE, U.S.S. R. 21 Résumé Les études expérimentales réalisées ont montré que tous les hydrocarbures légers qui sont présentes dans les huiles naturelles, ainsi que leurs composants plus lourds, sont obtenus des substances organiques des roches sédimentaires. Une pression élévée déjà en températures basses est favorable pour la formation du pétrole. Les données des expériences et les matériaux nouveaux sur les études des composés et des distributions du pétrole et du gas confirment que leur formation est un résultat des transformations biochimiques et puis thermocatalytiques et thermiques des substances organiques des roches sédimentaires au fur et à mesure de leur subsidence. Les études expérimentales ont montré, que la migration primaire des hydrocarbures est déterminée par la diffusion, le transfèrement des solutions liquides et gazeuses, les microruptures. L'accumulation du pétrole et du gaz pendant une migration latérale et verticale avec l'eau est le résultat du dégagement des hydrocarbur

Abstract Porphyrin compounds and related pigments are good geochemical marker compounds in the genesis of petroleum. Porphyrins or chlorins, isoprenoids and perylenes exist in rocks of all ages from early in the Precambrian to the present, and in modern plants. Of the distinctive pigment compounds, porphyrins predominate in old rocks, chlorins in recent. Mass spectrometry reveals the existence of phyllo and etio homologous series of porphyrins and chlorins with mass ranges from about 408 to 504. Low sulfur lowvanadyl-porphyrin oils show a direct relationship between vanadyl porphyrins and sulfur in heavy petroleums. Separate origins for the porphyrins of vanadyl and nickel pigments are indicated, with vanadyl coming from vanadyl chlorins of plants, and nickel from chlorophyll degradation products. The surface activity role of porphyrin and chlorin pigments in oil field formation is uncertain. Evidence for molecular associates of porphyrin pigments may reveal distinctive geochemical behaviour of lipids or proteins during oil field genes. Résumé Les pétroles bruts contiennent des composés de la porphyrine dans des proportions variant de 1,700 à 0.001 ppm. Ces composés sont en principe des molé- cules planes constituées de quatre groupes pyrrole reliés par des ponts méthine et contenant dans la plupart des cas un ion métallique en position centrale (le plus souvent un ion nickel ou vanadyl). On retrouve les mêmes complexes métalliques de la porphyrine dans les roches sédimentaires de toutes les époques depuis le précambrien en quantités variant de 40 à 0.0001 ppm. On considère généralement que ces pigments proviennent de la chlorophylle ou des composés semblables des plantes vivantes. Les transformations chimiques de ces pigments donnent des indications sur le mode de conversion que les matières organiques en général doivent subir dans l'histoire géochimique du pétrole. Geochemistry of petroleum is concerned with the processes by which crude oil accumulations are formed, and as such includes the various chemical and physical processes involved. The chemical steps refer to the chemical changes which occur to convert the source material into the hydrocarbons and nonhydrocarbons of petroleum. The physical changes refer largely to the relocation phases of hydrocarbon accumulation, including those of mobilization, migration and collection of the compounds involved in oil field formation1. It is generally acknowledged, however, that petroleum arises from biological substances, either directly or indirectly, and interest has centered on the study of biogenic tracers to gain an understanding of the chemical and physical factors involved in the evolution of petroleum. Porphyrin pigments have long been by G. W. HODGSON Head, Petroleum Division, Research Council of Alberta, Canada. B. L. BAKER and E. PEAKE Research Chemists, Petroleum Division, Research

Abstract Evolution of search procedure in the location of nonrenewable natural resources1 has led to the application of the philosophical principles underlying the geosciences, geology, geophysics and geochemistry; these approaches lead to tactical planning of search for prizes of commercial interest in areas selected for their potential promise, based on geoscience criteria. It now appears that a global strategy may be constructed using mathematical modeling with overall profitability of the system as a measure of effectiveness. The philosophy of this approach implies that an initial systematic grid-drilling procedure, leading to an inventory of the non-renewable natural resources of a large region, may be an optimal strategy. Successful application of this model would supply a new and more exacting basis for improvements in the philosophy of the geosciences and would, therefore, also lead to improvements in the tactical search procedure. Introduction Natural resources form the basic raw material for the development of a region or political unit; they may be subdivided into renewable natural resources comprising products based on animal and plant resources and nonrenewable resources which consist of metallic, nonmetallic and fuel resources. Some of the non-renewable materials have been worked since man appeared on earth and the location of these resources was, at least in the earliest days, a matter of chance observation. As in most human activities the search for natural resources developed into a search for "pattern" or "order" in their occurrence and there was an early pre-scientific period, equivalent to alchemy, in this evolutionary sequence; the doodlebug, the hunch and "chance" plays are contemporaneous equivalents which persist and still achieve some success. The scientific period commenced with, and encouraged the growth of, geology; its roots lie in the work of Agricola (1494-1555) and Werner (1750-1817) and eventually, as the composition and structure of the earth's crust became familiar, new patterns of search related to the distribution of the non-renewable resources were designed and an attempt was made to explain the patterns by constructing theories of origin of earth materials. Throughout this period from 1500 to the early 1800's the amateur prospector was almost the sole explorer and in the 19th and early 20th centuries by DR. JOHN C. GRIFFITHS Head, Department of Geochemistry and Mineralogy, The Pennsylvania State University, U.S.A. 39-11 the prospector and burro is symbolic of the more successful procedures for finding local concentrations of non-renewable natural resources. Local structural patterns, for example the association of oil and anticlines, were the main geological guides during this period. From 1925 geophysical techniques became effective in searching for the patterned structure associated with th

Abstract. This author concurs with the common belief nique. La nature de la biosynthèse, fondamentalement int hat petroleum is of organic origin. The fundamentally changée durant les 500 millions d'années qui viennent de unchanged nature of biosynthesis throughout the last s'écouler, est examinée; de là, l 'extr ême importance de 500 million years is argued and hence the study of the l'étude des sédiments actuels dans le cadre du problème recent Sediments is cogent to the problem of petroleum de la genèse du pétrole. Le r ôle important jou é par les genesis. The important role of fatty acids and waxes in acides dans la formation des hydrocarbures à chaîne f ormation of straight-chain hydrocarbons and naphthenes droite et des naphtènes est mis en évidence. Une étude i s noted. A study of recent Sediments shows that vir - des sédiments récents montre que presque tous les acides tually all free fatty acids disappear extremely rapidly. gras disparaissent extr êmement rapidement. Des étapes I mportant steps in the production of kerogen may occur importantes de la formation du kérogène peuvent ê tre while the organic detritus is slowly sinking to the sedi- franchies pendant la lente descente des particules, et leur ment. The organic contents of recent Sediments are dépôt. Les produits organiques contenus dans les sédialready much altered from their original form and re- ments r écents sont déjà tr ès transform és par rapport à semble petroleum more closely than biochemicals. leur nature originelle, et ressemblent déjà bien d'avan-Although small amounts of hydrocarbons are present in tage au p étrole qu 'ils ne ressemblent aux constituants Sediments their amount and mass distribution are such biochimiques. Bien que de petites quantités d'hydrocaras to indicate that original hydrocarbons play only a bures soient présentes dans les sédiments, leur quantité m inor role in petroleum. The existence in petroleum of a et leur r épartition sont telles qu'elles indiquent clairement spectrum of fatty and naphthenic acids plus the observed que les hydrocarbures originels comptent pour peu dans d istribution of straight-chain hydrocarbons and naphthenes la composition finale du pétrole. L'existence, dans le demands a complex origin for petroleum. All these sub- pétrole, de tout un spectre d'acides gras et d'acides stances can in principal be derived from thermal de- naphténiques, ainsi que la r épartition des hydrocarbures gradation of kerogen or cross-linked fatty acids or waxes. à chaîne droite et des naphtènes, requiert pour le p é trole une origine complexe. Toutes ces substances Résumé. L'auteur s'accorde avec l'idée généralement pourraient, en principe, d ériver de la dégradation theradmise, selon laquelle le p étrole serait d'origine orga- mique du kérogène ou des