Home – Home – Jornals – Russian Geology and Geophysics 2009 number 4

A probabilistic estimate of the global conventional recoverable oil resource was performed based on the concept of the Earth's sedimentary cover as a holistic system. A forecast for global oil production was made for the period till the end of the 21st century. It has been shown that the global oil production will most likely peak at 4.2-4.7 billion tons a year in 2020-2030. For that period, the top oil-producing regions in the world will be the Persian Gulf, West and East Siberia. The upstream sector at that time will turn its focus to the Arctic shelf. Annual oil production could be maintained at a level of 4.2-4.5 billion tons till the late 2040s.

The article deals with current problems of exploitation and pre-exploitation measures in oil and gas resource replenishment in Russia. Specific procedures are proposed to be taken at different levels of state administration for improving the efficiency of reserves replenishment. The public private partnership is suggested as one of the effective means to solve the problem. The level of the state's involvement in funding and management during regional exploration and prospecting survey is discussed. A systemic approach and a set of criteria for assessing the exploration success rate (at different stages) are recommended for use by the state, as subsurface owner, and for operating companies. In addition, several recommendations and action-oriented proposals are given for preparation of licensing programs that will ensure the preset rates of oil and gas reserves replenishment in the region.

This paper gives a review of oil and gas resource potential of the North Caspian petroleum province. A new potential for finding several giants and large-size discoveries exists, respectively, in the presalt and postsalt sequences. Recommendations for future directions in exploration targeting at postsalt deposits (Upper Permian-Triassic and Jurassic-Paleogene petroleum systems) are given. It is emphasized that, given adequate exploration techniques, the postsalt sequence may provide stable and commercial production for decades. Most of the prospects are located within nonlicensed area. Therefore, the future exploration activity will have to be implemented through special-purpose governmental projects, namely, state-funded integrated projects aiming at investigation of the individual petroleum regions and zones.

Aleksei Emil'evich Kontorovich, a titular member of the Russian Academy of Sciences, contributes very much to oil geology, in particular, to the foundation and development of the modern theory of petroleum generation and methodology of petroleum potential forecast.

According to recent data from seas and oceans, marine sediments have extremely uneven thicknesses varying from tens of meters to 15-20 km. Sedimentary material is localized mainly at three global levels: river-sea boundary (zero level, continental base of erosion), continental rise (3-5 km), and trenches (6-11 km). As a result of extremely rapid («avalanche») deposition in trenches, large amounts of organic matter accumulate in bottom sediments, thus providing their high petroleum reservoir potential. Sediments in areas of rapid sedimentation have a particular rheology, which causes them to move downslope hundreds of kilometers on the sea floor. Continental rise is a global area where gravitites accelerate, with their potential energy due to a depth difference of 3 to 5 km. Global-scale drift of sedimentary masses driven by eustatic sea level change produces very large deposition zones rich in oil and gas at the continental rise (global piedmont), i.e., at the second level. Predicted oil and gas fields of this kind have been discovered recently at sea depths over 3.5 km, which lie in stock for future development through the 21st century.

Available data on synthesis, input, and decomposition of organic matter (OM) in the water column and recent bottom sediments of the World Ocean are generalized. The most reliable values of OM production and masses in the ocean, the total supply of organic carbon, and the input of terrigenous OM with coastal erosion, river runoff, and eolian matter are estimated. Maps of fossilization coefficients, distribution, and accumulation of OM in recent bottom sediments of the World Ocean are presented. A numerical expression is proposed for the main circumcontinental pattern of OM accumulation in the ocean. The group and elemental compositions of living matter of the ocean, land, and the Earth as a whole and the organic composition of bottom sediments are briefly considered.

Oil and gas generation is a basic problem of geology and natural sciences, which is associated with energy resources as well as with the origination of life on the Earth. The evolution of hydrocarbons is controlled by the evolution of the biosphere and is an issue of phylogeny. Organic matter (OM) buried in sediments since the Early Precambrian consists mostly of phytoplankton, the main carrier of lipids producing hydrocarbons. Organic matter accumulates in marine sediments according to the law of periodicity. Middle Paleozoic fossilized OM is largely composed of zooplankton. Zooplanktonic OM, classified as sapropelites, had interfered with the process of oil and gas generation since its origin, e.g., tentaculites of the Domanik formation increased oil content. The inception of low-lipid macrophytes gave rise to introduction of humic OM into water bodies and formation of mixed-type OM. The larger the humic component in OM, the higher its gas potential. However, instead of replacing oil generation, enhanced gas generation had come on the scene since the Mesozoic, and their scales were approximately equal. The actual oil/gas ratio in sedimentary basins depends both on phylogenetic factors and on the evolution of each separate basin.

The paper deals with the main fundamental problem of oil and gas geology-compilation of a theoretical basis and elucidation of the mechanism of hydrocarbon pool formation. The temperature factor determining this mechanism is insufficient for the breaking of carbon-carbon bonds in organic molecules. It is shown that this process is provoked by the internal energy of the subsurface organic matter determined by unpaired electrons surrounding carbon nuclei. In natural processes, this phenomenon is realized as a result of sedimentary-rock consolidation on the subsidence of sedimentation basins, during subhorizontal microdislocations measured via Poisson's ratio and Protod'yakonov «arch». This effect can be reached on hydrofracturing. A possibility of fluid hydrocarbon migration beyond the modern-day oil and gas pools is discussed, thus demonstrating that there are no traces that would suggest oil migration. Hydrocarbon pools have been revealed in clayey rocks, both bituminous and OM-poor. It is shown that the exploitation of a new type of reservoir (bazhenite) with natural hydrocarbon pools as well as technogenic (newly formed) oil and gas pools in clayey, clay-siliceous, siliceous, clay-carbonate, and clay-siliceous-carbonate bituminous rocks will significantly increase oil production in West Siberia.

Considerable variations in depth zoning of dispersed organic matter (DOM) catagenesis are caused by various physical and geological factors. The evolution of a sedimentary basin (SB) implies successive changes in organization levels of this system. In the process of evolution the system structure is determined by the interaction of its subsystems. Any parameter of an SB (physical properties of rocks, degree of OM catagenesis, temperature, formation pressure, phase ratio of hydrocarbons) is governed by the processes running in the system. Variations of these parameters in space and time characterize the structure of the changing system. The intensity of lithification of terrigenous rocks, OM catagenesis, and HC generation in time is approximated by a curvilinear relation, which becomes asympthotic at a particular stage. In other words, these processes drastically decay 150 ± 50 Myr after the main sedimentation had completed. For an SB system with a natural set of main subsystems (mineral, water, organic, hydrocarbon), the age is less important (at least throughout the Phanerozoic) than the duration of the process. Analysis is given to the formation of vertical HC zoning, which includes all the processes observable within an SB. The relationship of events and qualitative temporal and spatial changes during these processes is considered.

Tectonics and petroleum potential of the underexplored East Arctic area have been investigated as part of an IPY (International Polar Year) project. The present-day scenery of the area began forming with opening of the Amerasia Ocean (Canada and Podvodnikov-Makarov Basins) in the Late Jurassic-Early Cretaceous and with Cretaceous-Cenozoic rifting related to spreading in the Eurasia Basin. The opening of oceans produced pull-apart and rift basins along continental slopes and shelves of the present-day Arctic fringing seas, which lie on a basement consisting of fragments of the Hyperborean craton and Early Paleozoic to Middle Cretaceous orogens. By analogy with basins of the Arctic and Atlantic passive margins, the Cretaceous-Cenozoic shelf and continental slope basins may be expected to have high petroleum potential, with oil and gas accumulations in their sediments and basement.

The relationship between the petroleum potential of the West Siberian province and the Mesozoic to Cenozoic tectonic processes is analyzed. The studies were based on structural and isopach maps of seismogeologic megacomplexes compiled from generalized geological and geophysical data on the province at the Trofimuk Institute of Petroleum Geology and Geophysics as well as on the results of interpretation of regional seismic CDP (common depth point) profiles. The main stages of formation of structures of different ranks and faults have been established. It is shown that the petroleum potential of the province was determined mainly by its structure and tectonic processes at the Cenozoic stage of evolution. At that time, the Koltogory-Urengoi megatrench formed, which became the main zone of hydrocarbon generation, as well as large positive structures-petroleum accumulation zones. Also, disjunctions originated, which served as channels for hydrocarbon migration from the oil source rocks of the Bazhenovo Formation to the main Neocomian and Aptian-Albian-Cenomanian petroleum reservoirs of the province.

The set of geological and geophysical features used to recognize paleorifts is not always complete. As a result, other negative tectonic elements having no favorable conditions for oil and gas generation may be misinterpreted as rifts. The aim of this study was to outline most important controversial aspects in distinguishing paleorift positions and to substantiate the necessity of taking into account a certain combination of their diagnostic features.

On the basis of complex research into the western part of the West Siberian Plate, a new scheme of the structure-formation zones of its basement has been developed and a new geological map of its pre-Jurassic basement has been compiled. Ophiolites and other mafic-ultramafic complexes (fragments of the oceanic Earth's crust) were studied. The most complete Late Ordovician ophiolite complex comprising a melange of serpentinites, gabbroids, plagiogranites, and basalt with jasper interbeds lies in the Shaim area. Weakly altered spinel lherzolites were also examined there. The research has revealed not only Ordovician but also Devonian basalts as well as gabbroid complexes (392 Ma, Sm-Nd dating). The Paleozoic geodynamic history of the region was terminated with collision, which was accompanied by tectonic piling and the intrusion of granite plutons, metamorphism, and formation of new continental crust. These crucial events, which consolidated Paleozoic complexes throughout the vast area of the future West Siberian megabasin, date from the Early Permian. The composition, age, and nature of granitoid plutons in western West Siberia were studied, and isochrons and isotope characteristics were obtained, which give an insight into both the genesis and age of granite plutons and their subsequent transformations.

The formation of the western margin of the Siberian craton in the Neoproterozoic is considered, with a focus on its transformation from a passive continental margin into an active one, accretion and collision processes, formation of island arcs and ophiolites, orogeny, and continent-marginal rifting. The evolution and correlation of sedimentary basins within fold-thrust belts of the Siberian Platform framing are considered. New structural and kinematic data on the Yenisei fault zone are discussed. On the basis of paleomagnetic data obtained for the structures in the zone of junction of the Siberian Platform and the West Siberian Plate, new models are proposed for the location of the Siberian craton relative to other paleocontinents and microcontinents in the Neoproterzoic. All these data provide a consistent evolution scheme for the western margin of the Siberian paleocontinent in the Neoproterozoic and constrain the position of the Siberian craton margin in Late Neoproterozoic (pre-Vendian) time.