Search

Authors used the paleogeographic approach to identify the different facies generation potential, mark out the areas with the highest organic matter and its types, analyse the reservoir quality for oil and gas potential assessment of the Pre-Caucasus basin Khadum formation. The greatest prospects in the Western and Central parts of the basin characterized by terrestrial and partly mixed organic matter types and are associated with the facies of the Sarpinsk-Armavir channel where discharge currents from the Volga-Don basin occurred. The same organic matter types can be related to clastic fans drawn from the north. In the Eastern part the main prospects are associated with unconventional black shale reservoirs with the predominantly aquatic organic matter, isolated on the top and base by the thick series of seal rock.

Most classifications of reservoirs, seals and source rocks based on the ability of the rock to generate, accumulate and preserve hydrocarbons, and the genesis of rocks is not always taken into account. The article presents a ranking scheme for continental, coastal-marine and marine sedimentation environments that determine the genesis and properties of the basic criteria of petroleum potential – source rocks, reservoirs, seals and pinch-out traps.Rocks, which can consider as source rock, reservoirs and seals are formed in each depositional environment. However, their structure, mineral composition and distribution area will differ from each other depending on the sedimentary environment and conditions. A combination of elements of the hydrocarbon system formed, corresponding to the sedimentation environment and are characteristic for basins of various types. Continental environments are favorable for the formation of reservoirs and local seals, while the accumulation of source rocks limited by lacustrine, floodplain, and swamp facies. The coastal-marine environment is favorable for the formation of all the basic criteria of petroleum potential, and the transgressive-regressive cyclicity determines the interbedding of source rocks, reservoirs and seals in the section. The marine depositional environments are most favorable for the formation of regional seals and source rocks, including high-carbon formations.The proposed ranking scheme of sedimentary environments and the basic criteria of petroleum potential genetically related to them is applicable in system analysis and selection for analogues of petroleum system elements in sedimentary complexes formed in similar depositional environments.

The criteria of petroleum potential of a sedimentary basin are the features that characterize the evolution of a hydrocarbon system as a geological unit. There are basic and additional criteria of oil and gas potential. Without basic criteria, the functioning of the hydrocarbon system and consequent petroleum field formation is impossible. Additional criteria characterize qualitatively and quantitatively properties of the basic criteria. The properties of all basic criteria are ordered by genesis and summarized in a system that allows to quickly and accurately establish a relationship between them and classify them. The system can be used to select quantitative parameters for geological simulation of different scales, but also for automated applying for petroleum exploration and production. At the same time, the classification of basic criteria can be used at all stages of exploration. At the prospecting stage, when the type of sedimentary basin and the sedimentary conditions are recognized with some uncertainty, it is possible to predict the properties of source rocks, reservoirs, types of traps and seals. If all static basic criteria, such as source rock, reservoir, seal and trap, are available, it is possible to simulate the formation of petroleum fields, including generation, migration, accumulation and subsequent post-accumulation processes. At the stage of exploration and development, the classifications will help to verify the geological and hydrodynamic models of the field, taking into account the link to the regional and local structural plans and correctly identify the geological features of the study object and select the geological analogues.

Oligocene-Lower Miocene clinoforms of the Maikop formation are productive in the Eastern and Central Pre-Caucasus region. In spite of commercial discoveries and long exploration history, Maikop formation is poor characterized by borehole data in the deep basins such as Terek-Caspian trough. Furthermore, there are challenges of the detail stratigraphic subdivision in the deep basins, correlation, sedimentary conditions and criteria of reservoirs exploration.Based on seismic and borehole data analysis, sequentstratigraphic framework, distribution area, progradation direction, seismic unconformities and thicknesses of the 17 Maikop sequences are established. Estimation of the clinoforms height allowed reconstructing paleobathymetry and paleogeography of the Pre-Caucasus region in the Oligocene – Early Miocene. Clinoforms M1-M7 prograded from the northeast, sea depth increased from 300 to 450 m. During clinoforms M8 sedimentation, new provenance area appeared on the west, sea depth increases up to 800 m.Clinoforms M12-M16 prograded from the north, sea depth decreases from 480 to 270 m. To the end of the M17 sequence deposition, starved deep basin was totally compensated.Three morphologic types of the clinoforms are identified. Type I represents by tangential clinoforms up to 75 m of height, that interpreted as subaqueous delta. Type II are the sigmoid shelf-edge delta clinoforms up to 800 m of height. Clinoforms of type III are low-angle wedges, confined to the slope and floor of the deep basin. Height of the wedges does not exceed 270 m. In the topset of the shelf-edge deltas, shallow-marine sandstones and structural traps predicted, while basin floor fans and stratigraphic traps expected in the bottomset. Subaqueous deltas are regarded to stratigraphic traps, while the wedges are predominantly mud-prone.

Unconventional oil and gas resource development and exploration is the one of the most prospective concept in petroleum geology. High carbon Khadum facies are investigated as unconventional resources in the Precaucas basin and contain gas, gas condensate and oil accumulations. Oligocene and Lower Miocene structure, prospectivity and fields distribution are the one of the most relevant subjects nowadays.This study is focused on the main stages Late Eocene and Early Oligocene deposits formation and the paleogeography of the Khadum formation in the Precaucas oil and gas basin. The new prospective zones are developed in Khadum formation based on the complex analysis of seismic, paleogeography and lithofacies analysis.