Caspian Basin Research Articles

Seismogeological interpretation of the wave-reflecting horizons of the eastern side of the transition zone from the South Caspian to the Middle Caspian basin

Seismogeological interpretation of the wave-reflecting horizons of the eastern side of the transition zone from the South Caspian to the Middle Caspian basin

Oil and Gas Content of the South Caspian Basin

Abstract —We have compiled maps of areal isotope composition changes and constructed graphs of gas HC distribution depending on the stratigraphic age of the host rocks and graphs of isotope composition changes depending on the depth of sampling to study the hydrocarbon potential of the deep-seated oil and gas pools of the South Caspian Basin. The genesis of gas was studied using the techniques elaborated by M. Schoell and A. James. Two stages of hydrocarbon formation have been established by study of various kinds of gas manifestation. The first stage (Miocene–Eocene) began in the deposits underlying the Productive Series and continued up to the deposits of the latter. This stage was characterized by a frequent change in the directions of both downward and upward movements of gases. The second stage of hydrocarbon formation (Anthropogene–Pliocene) began in the deposits of the Productive Series and was characterized by a change in the regional geodynamic setting. Avalanche sedimentation and the predominance of downward movements over upward ones favored the accumulation of thick sediments at the time when the Productive Series formed. The sedimentation and tectonic processes (downwarping) in the deep-water zone of the basin led to harsh thermobaric conditions in the sedimentary strata. A detailed analysis of the results of gas survey in the deep-water zone of the South Caspian Basin has shown gas generation with a predominance of two components, methane and ethane. Study of the trends of temporal and areal hydrocarbon migration and of the areas of oil and gas generation makes it possible to reveal structures with evidence for large and giant hydrocarbon reserves. We have established that gas hydrocarbons in the bottom and upper-section sediments of the southern Caspian Sea are intimately related to the sources of hydrocarbons, their migration, and other processes running in the deep-seated sediments and in the upper section.

СВЯЗИ МЕЖГОДОВЫХ ВАРИАЦИЙ СРЕДНЕМЕСЯЧНЫХ УРОВНЕЙ КАСПИЯ, А ТАКЖЕ СУММ АТМОСФЕРНЫХ ОСАДКОВ В ЕГО БАССЕЙНЕ И ИХ ИЗМЕНЕНИЯ ПРИ СОВРЕМЕННОМ ПОТЕПЛЕНИИ КЛИМАТА

In the modern period, the level of the Caspian Sea water surface is rapidly decreasing, which creates significant problems for the population and economy of all countries of the Caspian region. Therefore, improvement of the methods for forecasting its further changes is an urgent problem of hydrology, meteorology and ecology. It is generally accepted that the main reasons for the current decline in the Caspian Sea level are the influence of anthropogenic factors and climatic changes on the dynamics of its water balance components. A significant component of the incoming part of this balance is the amount of precipitation falling in the territory of the Caspian basin. One of the methods used for forecasting the Caspian Sea level is multiple regression analysis. The validity of the forecasts obtained with its help depends on the significance of the relationships between the studied process in the future and the factors monitored in the present and in the past that are taken into account in their development. The article assesses the significance of statistical correlations between interannual variations in the average monthly background levels of the Caspian Sea and the dynamics of precipitation amounts in its basin, as well as its changes during the period of modern climate warming. The ERA 5 reanalysis information was used as factual material on precipitation. Information on the levels was obtained from literary sources. It was found that in the period of 1979-2021 the conclusion on the significance of the relationships under consideration was characterized by the reliability of at least 0.95 only if the changes in precipitation amounts corresponded to May. As the time shift between the analyzed process and this factor increases from 0 to 36 months, their correlation remains positive and significant, but slightly weakens. During the period of modern climate warming, the revealed correlation also became weaker, which allows us to doubt its significance even in the near future. There were also identified the Caspian basin areas for which, on the contrary, the considered relationship strengthened during the same period. It implies that the probability of the scenario in which they remain significant in the future is higher than that of other scenarios. Therefore, it is reasonable to take the identified relationships into account when forecasting changes in the average level of the Caspian Sea.

Prospects for the allocation of Paleorousels in the subsalt complex of the south-east of the Caspian sedimentary basin

development and features of the formation of the sedimentary complex of the south of the Caspian sedimentary basin are presented. The complex geological structure of the region is mainly due to the influence of tectonic, volcanic and denudation processes on sedimentation. The introduction of terrigenous material deep into the sedimentary basin (Matken-Ushmolinsk, Biikzhal and South Embin zones) by paleorubic flows contributed to the emergence of accumulative shafts and interbranch uplifts composed mainly of clay rocks with alternating siltstone-sandstones. In the paleorusls themselves, coarser sediments were deposited – gravelites and sandstones. The reconstruction of the conditions of formation of sand bodies made it possible to predict their facies composition, morphology and identify patterns of spatial placement, and are also of great interest in the search for oil and gas deposits in deep-lying lithological traps. The prospects of these structures and their resource potential are evidenced by the world experience in identifying large deposits of hydrocarbon raw materials. This is a new highly promising direction of large accumulations of hydrocarbons for the Caspian Basin. The results of drilling deep wells conducted in recent years have made it possible to refine the internal structure, substantiate new facilities in the Late Paleozoic sedimentary complex, and reassess the prospects of oil and gas potential and forecast oil and gas resources of the south of the Caspian Basin.

Ediacaran to Jurassic geodynamic evolution of the Alborz Mountains, north Iran: geochronological data from the Gasht Metamorphic Complex

The Alborz Mountains in north Iran underwent several tectono-metamorphic events during opening and closure of the Palaeotethys and Neotethys Oceans. These events are recorded by rare and discontinuously exposed metamorphic rocks, such as the HP-LT Asalem-Shanderman Complex and the Gasht Metamorphic Complex (GMC), that are considered to have been metamorphosed during the closure of the Palaeotethys Ocean. The GMC comprises poorly exposed metasediments and amphibolites metamorphosed under greenschist- to amphibolite-facies conditions, along with smaller volumes of granites. Different dating methods were applied to selected samples of the GMC basement to constrain the geological evolution of this part of the Alborz Mountains. A metagranite yielded two LA-ICP-MS U–Pb zircon ages of 638.4 ± 4.1 Ma and 590.3 ± 4.8 Ma that possibly date protolith crystallisation and later deformation and metamorphism, respectively, and a granite yielded a late Ediacaran 551 ± 2.5 Ma U–Pb zircon crystallisation age. A northern provenance from the basement to the South Caspian Basin can neither be established nor ruled out because no age data are available for this unit. Derivation of the GMC from Turan Block basement is unlikely, as this has a different crustal makeup and is probably composed of Paleoproterozoic and early Neoproterozoic material. The zircon ages are similar to published ages from the Arabian-Nubian Shield, indicating that this part of the Alborz basement may have belonged to the northern margin of Gondwana in the Neoproterozoic before rifting and drifting away along with other Iranian blocks (the Cimmerian terranes) during opening of the Neotethys Ocean. Chemical Th-U-total Pb ages for metamorphic monazites from two metapelite samples yielded a very large range of spot ages, of which c. 80% falls between 200 and 250 Ma, that do not allow to distinguish between Eo-Cimmerian and Main Cimmerian events in the GMC. However, they may indicate that the amphibolite-facies peak metamorphism of the GMC occurred sometime in the Triassic, in any case much later than the Carboniferous metamorphism in the neighbouring Asalem-Shanderman Metamorphic Complex to the north. Peak-metamorphic amphibole from amphibolite, retrograde white mica and foliation-defining biotite from metapelites and magmatic white mica from granite yielded much younger 175.1 ± 0.5 to 177.0 ± 0.4 Ma 40Ar/39Ar plateau ages. The Toarcian 40Ar/39Ar ages for minerals with different nominal closure temperatures reflect very rapid cooling of GMC basement below the Shemshak Group due to extension-triggered uplift. This late Toarcian to Aalenian extension event can be correlated with the regional Mid-Cimmerian unconformity of mid-Bajocian age (c. 170 Ma) that resulted from the tectonic movements causing rapid uplift and erosion. Extension probably started in the western Alborz Mountains in the Toarcian, migrated eastward, and culminated in the Aalenian in the eastern Alborz with the formation of a deep-marine basin. It was probably triggered by the onset of the subduction of Neotethys oceanic crust beneath the Central Iranian Microcontinent.

STRUCTURE AND FORMATION OF MUD VOLCANOES IN THE SOUTH CASPIAN BASIN ACCORDING TO SEISMIC DATA

The South Caspian Basin (SCB) constitutes a classic province to study mud volcanoes and their associated processes. About 280 active mud volcanoes have been documented in the offshore and the onshore areas of Azerbaijan, emitting water, hydrocarbons (oil and mainly methane), and fluidized muds that transport solid fragments from deep sedimentary sequences. Seismic characteristics of mud volcano systems in the Azerbaijan area of the SCB are used to address: (1) the nature of the mud volcano source layer, (2) the internal geometry of the feeder systems, and (3) the processes associated with shale mobilization and extrusion. We confirm that the source layer is mainly the Maykop Suite (Oligocene–Lower Miocene), which is a thick (up to 3 km) and deep (>10 km) clayey sequence rich in organic matter. This layer was quickly buried due to basin subsidence and the rapid deposition (since the Middle Miocene) of thick fluvio-lacustrine sediments of the Productive Series (Upper Miocene–Upper Pliocene), which contributed to the creation of high pore pressures and the transformation of organic matter into methane (through thermal cracking). Since the Middle Miocene, and more importantly during the Upper Pliocene, the Maykop shales mobilized due to an increase in shear stresses and pore pressures, which promoted a decrease in effective stresses and, as a consequence, facilitated the achievement of critical state conditions in the shales that began to flow. This process repeated over time, allowed multiple pulses of shale mobilization to originate (as in a loading piston system). Shale piercing transporting deep-sourced fluids (and hydrocarbons) was carried out through fractures in the outer arc of anticlines, forming subvertical feeder systems. The mobilized hydrocarbons and fluids also recharged some of the younger and more permeable layers of the Productive Series, creating shallower reservoirs in the vicinities of the mud volcano structures.

Some features of local structures and their reservoir properties in the South Caspian Basin

Some features of local structures and their reservoir properties in the South Caspian Basin

Dating the middle and late Quaternary Caspian Sea-level fluctuations: First luminescence data from the coast of Turkmenistan

The Caspian region provides the basis of the stratigraphy and palaeogeography of the Pleistocene of Central Eurasia, and has been actively studied for more than 200 years. Many issues concerning the palaeogeographic history of the various basins of Caspian Quaternary remain unsolved, but the main problem centres on uncertainties in the chronology. Previous chronological studies have focused on a detailed description of the sedimentation history in the Lower Volga and Eastern Caucasus, ignoring a number of unique sites on the eastern Caspian coast, mainly due to inaccessibility. We obtained access to one of the most complete sections, western Cheleken, located on the Caspian coast of Turkmenistan. Within this sandy and generally lowland coast, the western part of the Cheleken peninsula forms a 10 km wide cliff opening a unique series of Middle Pleistocene - Holocene sediments which record in detail the history of Caspian transgressions and regressions. Stratigraphical, geomorphological and palaeontological studies of the section were supplemented with luminescence and radiocarbon dating. Analysis of Caspian molluscs and luminescence ages allowed the reconstruction of the sedimentary history of this region during one of the most important events of the Caspian Basin: the Early and Late Khazarian, Khvalynian and Novocaspian transgression/regression series. Luminescence dating of quartz and feldspar provided 12 OSL, IR50 and pIRIR290 ages, comparison of which showed that quartz grains were sufficiently bleached before deposition. Our chronology provides, for the first time, a deeper understanding of the sedimentation and environmental history in this region and the entire Caspian Sea. The Early Khazarian transgression occurred here at ∼220–200 ka (MIS 7). The Late Khazarian stage recorded in shallow-marine clays had relatively stable level ∼150–130 ka ago. In the second half of MIS 5 sea-level decreased and sedimentation was controlled by a large river, most probably the palaeo-Amu-Daria. The Early Khvalynian stage started at ∼27 ka and continued presumably until ∼14 ka.

Characteristics of source rocks and features of petroleum systems of the South Caspian basin

Characteristics of source rocks and features of petroleum systems of the South Caspian basin

Heavy carbon isotope composition of the Miocene diatomites and oils in the South Caspian Basin as a possible global phenomenon

Heavy carbon isotope composition of the Miocene diatomites and oils in the South Caspian Basin as a possible global phenomenon

Gold mineralization in oil fields of the South Caspian Basin. Discussion paper

Gold mineralization in oil fields of the South Caspian Basin. Discussion paper

Time and mechanism of formation of mud volcanoes in the South Caspian basin according to seismic data

There are 277 mud volcanoes located in the South Caspian basin and the Apsheron-Gobustan periclinal trough and the Lower Kura depression that open to it. On land there are 177 mud volcanic structures, from which steam, water, mud, gas and oil are constantly erupting at approximately 500 points. Mud volcanoes located in the Caspian Sea (about 100) also play an important role in the degassing (mainly methane) of the sedimentary layer of the earth’s crust. Based on the results of geological and geophysical research, it has been established that almost all mud volcanoes discovered on the territory of Azerbaijan are associated with hydrocarbon deposits. In the Oligocene – Lower Miocene, mainly in the Maikop time, a thick clayey stratum (Maikop) - source rocks – accumulated in the South Caspian depression. At the end of the Miocene, there was a sharp drop in erosion levels in this basin. As a result of the activity of several river systems (Pleo-Volga, Paleo-Kura, Paleo-Pirsagat, Paleo-Amu Darya) over the Maikop clay deposits, a system of alternating layers of low and high density was formed with a total thickness of sediments of eight kilometers or more. The Maikop clay formations buried under this multilayer system, possessing the properties of a non-Newtonian fluid, created intrusions in the overlying environment, which at subsequent stages of development of the sedimentation basin became eruptive channels of mud volcanoes. The results of research using 3D seismic data made it possible to identify the mechanism of formation of mud volcanism, which, according to the authors, is associated with the migration of hydrocarbons from oil and gas source rocks to reservoir rocks, with the channels of mud volcanoes being considered as the main migration routes. Geological interpretation of seismic data shows that the formation of mud volcanoes in the South Caspian basin supposedly began from the beginning of the Miocene and continued in parallel during subsequent periods of development of the sedimentation basin. As the thickness of the sedimentary cover increased, mud volcanoes periodically became active.

Influence of geotemperature conditions on the oil and gas potential of the South Caspian depression (the case of the Lower Kura depression and Baku archipelago)


 
 
 In the article, the oil and gas potential of the deep-lying sediments of the Lower Received in revised form 13.08.2023; Kura depression and the Baku archipelago, which are geostructural elements of the South Accepted 13.11.2023 Caspian depression, are investigated according to the geotemperature conditions. The main aim of the research is identifying the oil-gas «windows» in the 22-24 km thick sedimentary rock complex of the South Caspian depression based on the geothermal factor. Using temperature values measured at different depth sections in different structures of the Lower Kura depression and Baku archipelago, temperature distribution maps of the area and a graph of changing temperature by depth were constructed. According to the geothermal maps constructed for the Lower Kura depression, a relatively high temperature value is observed in the north-west part of the area. This anomalous value is related to the location of active, periodically erupting mud volcanoes, which play an important role in temperature distribution, as well as local uplifts, which are more complicated by tectonic landslides and upthrusts. At great depths (5,500-6,500 m) within the research region, almost everywhere, anomalously high pore and reservoir pressures are observed, which create the conditions for the manifestation of tectonic-physical processes and the generation of great energy affecting the oil and gas potential of the area. In all the geotemperature maps constructed for different depth intervals in the Baku archipelago, high temperature values are observed in the north zone where the Sangachal-deniz-Duvanni-deniz-Khara-Zira island and Alat-deniz structures are located. This is due to the complication of uplifts by active mud volcanoes, which play an important role in the formation of local heat sources. The Khara-Zira island mud volcano, the largest in the Baku archipelago, is also located here. Based on the analysis of the temperature values in the research areas, a decrease in the temperature values is observed due to increase in the thickness and the clay content of the sedimentary layer in the direction from the Lower Kura depression to the South Caspian basin. The temperature is 990C at 5,000 m in the Lower Kura depression, 900C in the Baku archipelago. So, a decrease in temperature is characteristics for all depths. The analysis of the compiled graphs shows that the top of the main zone of oil formation in the Lower Kura depression starts at a depth of 2,000-2,500 m, and the lower limit is located at a depth of about 9,000 m (1500 C). The top of the main zone of oil formation in the Baku archipelago starts at a depth of 3,000 m, and the lower limit is located at a depth of 9,000-11,000 m. So, it shows that as the oil and gas formation sources the potential oil source rocks in the Lower Kura depression and the Baku archipelago at the depth range from 2,000-2,500 m to 8,000-11,000 m can produce industrially important oil and gas.
 
 

К вопросу о методике литолого-петрофизических исследований каменного материала (в процессе бурения нефтегазовых скважин)

This article discussessome aspects of the methodology for preparingsludge andcoresamples for lithological and petrophysicalstudies. Methods for obtainingrockmaterial(sludge,core) are described interms of determiningthemoment of openingthereservoir layer,tyingthecore in depth, and sampling the sludge. A sludge collector has been proposed that makes it possible to obtain sludge of overall fractions washed from the drilling fluid. The effectiveness of the harmonic analysis method, which takes into account the lithology of the studied section and changes in drilling parameters to optimize the frequency of sludge sampling during drilling, is shown. A system for placing sludge sampling points has been justified to increase the information content of the study of well sections. An analysis of the actual material on the connection of sludge to formations using natural gamma activity in wells drilled in the conditions of the Saratov Volga region was carried out. The distribution of the residual values of the burial depths according to thesludge and well logging allowed us toconclude that in the vast majority (> 75%) ofcases, the binding ofsludge during geological testing iscarried out withsatisfactory accuracy. The implementation ofsome elements of the above described interpretation techniques is shown using the example of one of the wells located in the northwestern part of the near-shore zone of the Caspian basin.

Tectonic stress around the South Caspian basin deduced from earthquake focal mechanisms

ABSTRACT In this paper, we study the tectonic stress around the South Caspian Basin (SCB), which includes the Kopeh Dagh, Alborz, Talesh, eastern Greater Caucasus mountain belts, the Apsheron sill, and the Balkhan-Ashkabad fault zone. We apply the stress inversion to focal mechanisms of 410 mainshocks that have occurred over the last 69 years. These mechanisms indicate that the surrounding fault zones of the SCB exhibit diverse types of faulting, ranging from thrust to strike-slip, normal, and their combinations. The results of the stress inversion align with the kinematics of the major fault zones bounding the SCB and emphasize the spatial heterogeneity of the stress field in this region. The region is predominantly under compression, but transpressive and strike-slip regimes are also present. This highlights the role of obliquely oriented basement faults with respect to the maximum horizontal compressive stress (S Hmax ) in accommodating deformation through convergent zones. The orientation of the S Hmax is in the NE to NNE direction in the Kopeh Dagh, Alborz, Talesh, and Ashkabad-Balkhan fault zones, being rotated to NNE-N in the Greater Caucasus. The orientation of the S Hmax relative to the convergence direction of the Arabian and Eurasian plates indicates that the Arabian-Eurasian oblique convergence-derived tectonic stress is the primary contributor to the total stress and deformation in this region.

Paleozoic reef formation in the Pechora syneclise and the Caspian basin – a comparative analysis

In the two marginal depressions of the East European Platform, the Pechora syneclise and the Caspian depression, reef formations are widely represented, but the stratigraphic intervals of their development are far from equal. In the Pechora syneclise, reef formation began in the second half of the Llandoverian, reached its maximum in the Frasnian and was replaced by the development of reef hills in the Famennian. The structures are represented both as asymmetric reefs framing the shallow zones at their boundary with relatively deep paleobasins and in the form of single structures within the latter. The reefs of the next global maximums, the Late Visean-Serpukhovian and Lower Permian, are developed only marginally at the boundary with the Ural paleoocean and its relic, the Pre-Urals foreland basin. In the Caspian basin, reefs of all three global maxima of development are present, and there are both asymmetric reef systems framing the shelf edges and symmetric intra-basin isolated structures. Such difference is due to the different paleogeomorphological type of the basins. The Caspian basin was sharply differentiated in depth throughout the Middle and Late Paleozoic, which led to the formation of reefs rising above the bottom of these basins. In the Pechora syneclise, depth differentiation of the basins occurred only in the late Devonian. Generally weakly dissected shallow seas of the Visiean-Serpukhovian and early Permian did not provide conditions for the formation of powerful reefs protruding above the seafloor. The latter were formed only on the edge of the Ural paleoocean, and in the Permian ‒ on the edge of the Pre-Ural foreland basin.

An information-analytical overview of mud volcanoes in the lower Kura basin (Azerbaijan)

This article provides an overview of mud volcanoes (MV) of the Lower Kura region (Azerbaijan). The Lower Kura Depression (LKD) occupies the southeastern part of the Kura-Araks lowlands. Tectonically the LKD is considered to be the eastern edge belonging to the west board of the South Caspian Basin (SCB). The large thickness of sedimentary deposits, reaching 25 km, and the high rate of sedimentation are consequences of the activity of the Paleovolga and Paleokura. Mud volcanic structures in the region are widespread and associated mainly with longitudinal fault dislocations of large amplitude. This paper provides an assessment of numerous research data from studies of mud volcanic products of the Lower Kura Basin. Using the PETROMOD software package, mud volcanoes, and the main factors of their formation were analyzed and physical models were built. The identified differences in the chemical composition of gases and water, kerogen types of organic matter contained in rock emissions, make it possible to improve the understanding of sediments located in deep zones, poorly studied or not yet opened. The conducted research and analysis once again prove that the use of new methods for studying mud volcanism, giving preference to comprehensive analysis, is an important requirement of oil and gas geology.

On new prospects for petroleum and gas capability of Paleozoic sediments of the Karpovski projection

The article presents the geological data of recent years – the results of seismic exploration and deep drilling, which allow us to make new constructions of the model of the structure of the Paleozoic sedimentary complex of the northern side zone of the Caspian basin. In the historical development of the Caspian sedimentary basin, multiple geotectonic collisions have been observed, leading to transgressions and regressions of the Paleocean, as well as erosion of accumulated sedimentary strata, as well as interruptions in sedimentation. In the northern side zone, the determining influence of the structural sedimentation factor affected the age-varying carbonate ledges of the Karachaganak carbonate platform of the Aksaiblock, the Teplov-Tokarev zone of the Karpovsky tectonic ledge. Most of the oil, oil and gascondensate and gas condensate fields identified in the subsalt complex of the north of the Caspian Basin are associated with these zones. A comparative comparison of the deposits of the instrument zones of the Caspian basin has shown a fundamental difference in the conditions of accumulation of productive horizons, which lies in the nature of the location and in the significant variability of the filtration and capacitance properties of formations in natural reservoirs. The presence of deep-submerged carbonate structures is predicted in the deep part of the depression, on the slopes of carbonate platforms. Prospects for the detection of organogenic structures in the inner part of the paleobasin are assumed on the eastern extension of the Karpovsky ledge of the foundation and inside the Pogodaevo-Ostafyevsky trough, where, according to the results of 2D and 3D seismic surveys, promising structures Cretaceous, Orlovskaya and a number of others have been identified.

China’s energy diplomacy in the Caspian Basin and its impact on the energy security of Europe

Recent global events such as COVID-19 and Russia's invasion of Ukraine led to a significant transformation in the global energy market. The European Union's (EU) vulnerability to energy supply made the concept of diversification of energy supply more prominent. China also needs a stable energy supply for its sustainable economic growth. We observe that the energy resources of the Caspian Basin are crucial for the energy supply of China and the EU in this market for energy supply diversification. The research aims to analyze energy trends in the Caspian Basin and in what direction are these energy trends? Towards Europe or China? Three theories - interdependency, energy security, and sustainability - are used to analyze the research aim. The findings indicate that China has sustainable Gross Domestic Production (GDP) growth and a high Human Development Index (HDI) level, and its energy diplomacy in the Caspian Basin follows three concepts: Shanghai Cooperation Organization (SCO), Belt and Road Initiative (BRI), and Mutual Cooperation. Conflicts around the Caspian Sea have geopolitical roots in the West but internal roots in the East. Thus, current trends in the Caspian Basin are causing states to move toward China.

Paleozoic Reef Formation in the Pechora Syneclise and the Caspian Basin: A Comparative Analysis

Paleozoic Reef Formation in the Pechora Syneclise and the Caspian Basin: A Comparative Analysis