To the geology of tertiary quaternary sediments of south-west part of the caspian sea published

To the geology of tertiary quaternary sediments of south-west part of the caspian sea published

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  4 To the geologyof Tertiary - Quaternary sediments of South-West part of the Caspian Sea Dr. Arzu Javadova a*, Kurosh Ettehad b, a. MicroPro GmbH, Germany, [email protected] b. Department of Geology, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, Iran, [email protected] Abstract The SW part of south Caspian offshore studied very poorly. Data studied from numerous offshore shallow engineering and deep exploration wells have provided useful information on the geology of the Tertiary- Quaternary sediments. The log, seismic data, and biostratigraphy confirmed that the Tertiary sediments consist of fluvial- deltaic–lacustrine sediments deposited in the isolated South Caspian Basin, particularly in the study area by several river systems. A Quarternary period is characterized by brackish water sediments. The "short" series of marine sediments of the deep and shallow facies of open sea bays, delta, and marine shallow waters are typical for the SW part of the Caspian. Pliocene and Quaternary sediments unconformably overlie more ancient formations, until the Mesozoic sediments are located at a relatively shallow depth. In the Lankaran-Talysh Deniz, the Miocene sequences below the middle part of Pliocene Pereryva formation are pinching out against the basin margin. The thickness of these series increases stepwise across the main structures giving evidence of a rift-system developing at the beginning of major subsidence in the South Caspian during the early Tertiary. No hydrocarbon discovery except little oil and gas shows are found in SW of the Caspian due to several geological reasons such as a reservoir, vertical and lateral migration problem. Keywords: geology, sedimentology, South Caspian, paleoecology, * Corresponding author. Tel.: +4917661283105. E-mail addresses: [email protected], [email protected].
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  5 1. Introduction The CaspianSea is the world’s largest inland water area. The South Caspian encompasses the southern extension of the Caspian Sea, including land areas in eastern Azerbaijan, western Turkmenistan, and northern Iran (Smith-Rouch, 2006). It is an elongated basin, extending from north to south direction and is characterized by shallow water in the northern part and a gradually increasing depth towards the south, reaching a maximum depth of 1200 meters in the southern part (Yassini, 1986). Fig.1. Fig. 1. Study area in the south-west Caspian Sea. Location of the Lankaran-Deniz, Talysh-Deniz, and Khazar structures and deep exploration wells In the SW Caspian Sea, there are drilled few exploration wells in such structures as Lankaran- Deniz, Talysh-Deniz, Kurdashi, Khazar, Pahlavi, Shahabad, etc. Our study focused on offshore shallow and deep exploration wells of Lankaran-Deniz, Talysh-Deniz (in Azerbaijan sector), and Khazar structures (in the Iranian sector). The studied Lankaran and Talysh Deniz structures are located close to the Lower Kura delta zone, approximately 50 km east of the city of Lankaran, where water depth ranges from 10 to 150 m, from north to south. The northern closure of the structure comes within 3 km of the boundary of the Kyzylagach wildlife reservation, a marshy area, sensitive from an ecological point of view. Structure Khazar is located approximately 100 km far from Lankaran city structure, relatively close to the Sefid-Rud river in the Iranian sector of the Caspian Sea, where water depth ranges from 15 to 150 meters. It should be noted that before any offshore exploration drilling there always drilled several shallow engineering wells up to 150 m with random core samplings. These wells are drilled for geotechnical purposes, below the mud line at the exploration well location, to determine the Jack-up legs penetration and identify any possible hazard masked by the gas front. The distance between deep exploration well and shallow engineering wells are normally around 4-5 meters. In mid of 1980th years in structures, Lankaran-Deniz and Talysh-Deniz drilled 74 shallow engineering wells, and in 2000-2001 the TDX1 deep exploration well drilled up to 4435 m (up to Tertiary) in Talysh – Deniz
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  6 structure. In midof 1990th years 6 shallow engineering wells and 1 Khazar -1 deep exploration well drilled up to 5576 m (penetrated to Cretaceous strata) in the Khazar structure. The present study is based on the examination of cores, logs, and seismic from shallow engineering and deep exploration wells of Lankaran-Deniz, Talysh-Deniz, and Khazar structures. 2. Materials and methods. More than 550 samples from a various depth of 80 shallow engineering wells in Lankaran-Talysh Deniz and Khazar structures were studied. The study included the faunal content and lithology of core materials. Besides, that 2 deep exploration wells from Talysh-Deniz (TDX1) and Khazar -1 wells supported the biostratigraphy of deep sequences. We analysed the log materials (KS, PS, Gamma Ray, Mud log) of Talysh -Deniz, and Khazar structures and reviewed their 2D seismic profiles. It should be noted that the 2D seismic quality of the Khazar was very poor, old and therefore, we were limited to the seismic- geological profile across Khazar-1 well only. Fig.2. A- Lankaran-Talysh - Deniz. Scale 1:50 000; B-Khazar. Scale 1:100 000 Top Productive series structure map with studied shallow - engineering borehole and deep exploration well locations. 3. Regional Geological setting. According to the plate tectonics, the Arabian lithosphere plate moves north towards the Eurasian plate. The Earth crust in the South Caspian region is characterized by compression in the sub-meridional direction and extension in the sub-latitudinal. In this regional field, the stressed, large faults of the Caucasian and Trans Caucasus strike demonstrate geodynamic and seismic activity. The modern feature of the South Caspian Basin originated during the last stage of Alpine folding. This
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  7 explains why identifiedstructures in the SW part of Caspian and surrounding oil and gas fields are parallel to ancient structural elements that predate the latest movement. Currently, the SW part of Caspian along with the entire south Caspian basin is a region of active folding, diapirism, fracturing, seismicity, mud volcanism, geysers, and thermal springs (Buryakovskiy, et al., 2001). The Iranian coast extends over more than 600 km along the South Caspian lowland and includes the western Gilan, central Mazandaran, and eastern Golestan segments. The lowland is bordered by the Elburz Mountains to the south. It should be noted that the folded system of the Greater and Lesser Caucasus approach the western coast of the Caspian Sea, which are experienced sharp subsidence, with thick Neogene-Quaternary formations. The sedimentary cover of the South Caspian depression studied by drilling to a depth of 6.5 km belongs to the Pliocene-Quaternary complex. The deeper structure of the depression is predicted from geophysical and data and is largely hypothetical. The southern Caspian is limited on the south by the northern Alborz Mountain range and has a rapid and sharply deepening steep slope. On its southwestern margin, the bottom slope is more gradual (deepening) due to the Talesh and Caucasus mountains. It is filled with several hundred meters of loose sands and pebbles derived from the Elburz Mountains. Its surface is covered by flat terraces slightly inclined toward the seashore (Svitoch and Yanina, 2006). The geology map of the area shows that the most southern part of the Caspian Sea is occupied by the Iranian deep-water basin (or Pre Elbrus-Basin (Glumov, et al., 2004). Fig.3. Fig. 3. Simplified geological map of the study area and its surrounding (from Khabbaznia and Sadeghi, 2004; Nazari et al., 2004). Referring to the local geology and literature in the Cretaceous, magmatic formations have begun to play an essential role. The thickness of the sedimentary cover in the central part of Elbrus reaches 10 km, slightly decreases (to 7-8 km) at the SE end of the South Caspian depression, and decreases to 2.5-3 km at its SW part. This complex of rocks should theoretically lie under the Oligocene-Quaternary molasse in the SW segment of the South Caspian depression. According to regional seismic data, it can be concluded that, most likely, as a result of the stretching of the earth's crust during the formation of the South Caspian, the faulting process occurred. In certain areas of the
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  8 depression, there shouldbe zones of the absence of both Meso-Cenozoic and Cambrian-Cenozoic sedimentary cover, filled with Oligocene-Quaternary or Miocene-Quaternary deposits. SW of the Caspian Sea area across the continental shelf of Azerbaijan and Iran slopes to the SE direction of the South Caspian depression. Water depth in this area ranges from 5 m in the north to 500 m in the SE corner, while the SW and southern Caspian shelves in Iran have steep offshore slopes and corresponding steep coasts (Kakroodi, et al., 2012). The southern coast of the Caspian Sea in Iran side, typically the section from Anzali to Astara, consists of ancient and modern sandy beaches. The south–southwestern Caspian coastal lowland in Iran, or the Gilan–Mazenderan plain, is a relatively narrow but long, composite depositional area of late Quaternary age (Kazanci, et al, 2004). All anticlinal structures in the SW part of the South Caspian basin are the result of major compression / strike-slip movements. Structures are an elongated NS anticline which results from the compressive movements of the uppermost Pliocene (Akchagylian age) and transgressive movements of the Late Pleistocene (Apscheronian) induced by the collision of the Arabian & European plates, which are also responsible for the rise of the Caucasus, Talysh and Elburz mountain ranges (Berberian, 1983). There is major structural direction is developed and SW. Fig.4. Fig. 4. South Caspian basin. Fields and prospects. Major structural directions of the study area. 4. Structural analysis. Reviewed seismic information provided information about reverse faulting in Pontian and older Pliocene levels which is a common feature in the South Caspian basin. Often mud diapirs are related to the anticlines. The reverse faults are related to older rifting/normal faulting interpreted from thickness variations across faults at deeper levels. The offshore part of the South Caspian basin: during Pliocene and Quaternary time is characterized by both, very high rates of subsidence and very high rates of sediment influx. The accommodation generated by subsidence however always was higher than the rate of sediment supply. This is obvious when regarding the structures which developed mainly during this period. The crests of the anticlines never were subject to erosion,
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  9 stages of majorstructuring e.g. in late Pliocene, at the Pliocene-Quaternary boundary, and during Quaternary can be recognized from onlapping reflections in the synclines (Narimanov, 1993). This is most obvious at the basin margin e. g. on sections across Lankaran-Deniz, Talysh-Deniz, and Khazar anticlinal structures. Geologically these structures are in the SW corner of the South Caspian Basin close to its SE limit of the Talysh fault. In the seismic, Lankaran and Talysh Deniz structures are well defined beyond any doubt. They are NS elongated anticlines accompanied by an NS trending fault system of the compressional type in the lower part of the section. This deep compression is compensated by graben-like normal features in the shallower crest part of the structures. Pliocene and Quaternary sediments unconformably overlie more ancient formations, until the Mesozoic sediments are located at a relatively shallow depth. Nevertheless, the structures were already initiated in the upper Miocene; as a result, the lowermost units of the Pliocene were not deposited over the top of the structure, and may not be encountered in the drilled two exploration wells in Talysh - Deniz (Well TD1X ) and Khazar (Well Nr1). Miocene sequences below the middle part of Pliocene Pereryva formation are pinching out against the basin margin. The thickness of these series increases stepwise across the main structures giving evidence of a rift-system developing at the beginning of major subsidence in the South Caspian Basin during the early Tertiary. These faults subsequently were re-activated in a compressional regime, and the normal faults converted to reverse faults. This is less obvious in Lankaran as due to the basin ward intercalation of additional sequences below the Lower Pliocene Productive Series the fault rather resembles a normal fault. Fig. 5 and Fig. 6. Fig. 5. Talysh - Deniz structure. A seismic line through Well TD1X Unsuccessful drillings in the southern offshore part of the South Caspian basin (Inam, Kurdashi, Yanar-Tava, Atashkah, Dashly, Sebail, etc) including SW located Talysh- Deniz and Khazar structures targeted to Pliocene deposits resulted that there was no hydrocarbon discovery except few oil and gas shows, due to several geological reasons such as a reservoir, vertical and lateral migration problem, etc.. The time window for charging of Talysh-Lankaran from the mature oil kitchen area further east was small, and the capacity of the structure at that time interval was limited. TDX1 well confirms effective charge to the adjacent Lankoran structure to be the key risk element, however, a flat spot in the PodKirmaku sands could point to effective charge.Fig.7.
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  10 Fig. 6. Lankaran-Deniz.A seismic line over the structure Fig. 7. The seismic line between Lankaran and Talysh Deniz structures Severe overpressures were observed in TDX1 well, starting from very shallow depths due to in-situ under compaction (abnormally low velocities observed). According to logs, sandy intervals may have a somewhat lower pressure regime when they are thick and widespread, allowing pressures to bleed off. When sands are relatively thin and not widespread, the likelihood is that they are disconnected and have essentially the same pressure regime as the under compacted shales around. In this situation, significant HC-columns cannot develop as an effective charge of the sandy unit is not possible. The dip's main bounding fault system is active until recent times and may provide the passageway for the fluids bleeding from the under compacted shales and over pressured sands. With steep flanks, the transmission of these under compaction pressures to shallower depths, and fluid pressures may locally exceed the overburden gradient. This may create fracturing and add to the risk that HC’s originally trapped may have escaped; there remains disagreement as to whether these mechanisms is an important risk element, or not.
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  11 The Khazar structureextending from the south-southwest to the north-east of the Caspian Sea, with a length (according to 2900 isopach of top Productive series) of 14 km, the width of 5 km, and height of 1500 m. It is a complicated geological structure with tectonic faults with an amplitude of up to 300 m. The structure is asymmetrical in length and width. The relatively elevated part of the structural crest inclined to the north-east and is surrounded by 2400 m isopach. Based on the core data, the angle of inclination of the strata in the south-eastern wing of the Khazar structure reaches 10-150 m. In the upper part of the section in the salt and anhydride strata, it reaches 30-350 m, and the NW wing has almost flat deposition. To the north of the structure, near the arch, there is an active griffin on the seabed. The base of the Akchagyl deposits consists mainly of clays and has a large thickness (up to 1050 m). Fig.8. Fig. 8. Khazar structure Cross-section 5. Biostratigraphy and Sedimentary There is no published literature about the stratigraphy, fauna, and sedimentary information of Tertiary- Quaternary of the SW Caspian Sea due to low exploration drilling. According to the onshore geology of SW Caspian, there are Cretaceous, Tertiary, and Quaternary deposits take place. Micropaleontological studies of the Khazar-1 well confirmed that the well contains Pleistocene to Cretaceous sediments. In the log, there is observed a discontinuity between the deposits. Pliocene to Pleistocene sediments confirmed by ostracod and the Palaeozoic Cretaceous age by benthic and plankton foraminifera. Based on the analysis of 2 deep exploration well sections incorporation with surrounding regional geology and other onshore drilling results, it should be noted that the SW Caspian Sea lowland in Iran and Azerbaijan sides forms a thick sedimentary stratum produced by interactions of marine, deltaic, and fluvial processes during the Late Neogene and Quaternary periods. Deltaic and fluvial deposits have been developed mainly by the Sefid-Rud and Kura rivers. Different sections of
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  12 the South Caspiancoasts are characterized by their facies series. The "short" series of marine sediments of the deep and shallow facies of open sea bays, delta, and marine shallow waters are typical of the Lankaran-Talysh and Kura lowlands. For the coastal plain of the mountainous coast of the Caucasus, this is a combination of shelf facies - beach - lagoon; shallow water shelf - deltas - marine sediments - diluvium; sea beach - aeolian precipitation. It is confirmed that Lankaran - Deniz and Talysh - Deniz's structure is a continuation of the Lankaran-Talysh lowland in the South Caspian. Drilling uncovered till Tertiary deposits. In the onshore side, the Tertiary system of Lankaran -Talysh lowland region is represented from the Palaeocene till the Ackchagyl stage. The Apsheron deposits are absent in onshore. Probably they were not deposited in the onshore area at all. İn onshore the total thickness of the Tertiary system deposits is 8000-9000 m on average (including the volcanogenic formations- 3500 m- 4000 m). The Quaternary system deposits in the north margin of the Lankaran-Talysh lowland region are up to several hundred meters. In offshore the Talysh - Deniz TDX1 well-stripped thickness of Tertiary deposits is 2772 m; the Quaternary is 932 m. After a depth of 3740 m, there is the presence of discontinuity and non- deposition of Eocene, Oligocene, and Miocene. In Miocene sections reservoirs are sand. Tertiary rocks are not rich with quartz and there is pyroclastic material present in their content (polymictic and tuffogenic sandstones). Therefore, reservoir properties of the Lankaran region are worse than quartz sandstones of other oil-bearing regions. Fig.9 Reservoir properties of arenaceous, siltstone and tuff-sandy rocks of the Tertiary section of the Lankaran region vary both in the vertical and horizontal direction. Improving is observed in the vertical direction from down up, and from the SE to the NW in the horizontal direction. In the onshore south-west part of the Caspian Sea, the porosity of rocks-reservoirs of Oligocene and Miocene varies within 15-45%, Eocene and Palaeocene- 5-20%. Permeability of Oligocene and Miocene is 15-20, and rarely 100-110 MD, Eocene, and Palaeocene- 30-40 MD. Respectively, the former can be considered as more or less permeable and the latter is poorly permeable. The main reasons for not satisfactory enough reservoir properties of Palaeocene and Eocene rocks are their bad sorting, presence in their content of a considerable amount of pyroclastic material, and the character of cementation. Southern Caspian depression where located Khazar structure corresponds to the Gilan– Mazenderan plain of the latest Tertiary–Quaternary or to the Mesozoic–Cainozoic subaerial part of the south Caspian basin. Berberian (1983) reported that Pliocene–Quaternary continental strata are 1,600–2,000 m thick in the coastal plain north of the thrust fault that marks the north flank of the Elburz Mountains (Smith-Rouch, 2006). According to log analysis In Khazar-1 well from a depth of 3800 to 4512 m, there is an anonymous zone which might be a sequence of Lower Palaeocene age. There was not found any fauna which might help us to confirm log analysis with a clear definition of the stratigraphy of this sequence. In the interval of 4512 to 4763 m again observed an anonymous sequence without any fauna. In 4763 to 5576 meters (final depth), the anonymous sequence with foraminifera fauna resembling Cretaceous Albian- Cenomanian age. The thickness of Tertiary deposits is 1850 m and the Quaternary is 1889 m with a characteristic complex of ostracod and fragments of macrofauna. A drilled sequence of the Khazar-1 well has a thickness of 5576 m and in descending stratigraphic order has been divided into the Neocaspian, Khvalinan, Khazarian, Bakunian, Apsheronian, Akchagylian, Pliocene, and unnamed Palaeocene-Cretaceous strata. Dominant lithology in Khazar-1 well includes volcanic ash, siltstone, and sandstone. Along with carbonate layers, the drilled Khazar-1 borehole was compared with the onshore Lankaran-Talysh area. Based on this comparison and paleontological data in the middle Pliocene-upper Miocene strata are not present in the Khazar-1 in SW Caspian. Fig.10
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  13 Fig. 9. Talysh-DenizTDX1 well section with biostratigraphy
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  14 Fig. 10. Khazar-1well section with biostratigraphy
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  15 The Shahabad-1 wellis the exploration well in the Iranian onshore Mugan area, which is relatively close to the Khazar-1 well. We compared the drilled sequence of Shahabad -1 with Khazar- 1 well. For instance, Eocene strata are present in the Shahabad-1 well, whereas this stratum is absent in the Khazar-1. Likewise, the volcanic rock fragments and tuff are more common than the Khazar-1. Furthermore, the Pliocene deposits of the Shahabad-1consist of carbonate sand (coquina), tuff, and volcanic rock fragments, whereas the Pliocene strata of Khazar-1 mainly consist of claystone, conglomerate, and anhydrite. Upper Pliocene sediments which are a reservoir in the Azerbaijan and Legend of Figure 9 and 10 Turkmenistan area of the south Caspian Sea is present in Khazar-1 well, whereas it is absent in the Shahabad-1. Upper Pliocene in Khazar-1 is made of anhydrite and limestone, contrary to the other areas of south Caspian Sea with alternation of shale, siltstone, and sandstone. This alternation is a source and reservoir in the Turkmenistan and Azerbaijan side of the south Caspian basin. The paleoenvironment was not suitable for an organism’s life. So, it cannot be as source rock. The Apsheronian strata of Khazar-1 have been attributed to the Pleistocene age (Eopleistocene). Since much works have been done in the Iranian part of the south Caspian basin, one cannot apply the result of the Khazar-1 well for the whole parts of Iran part of the south Caspian basin. On the other hand, around Azerbaijan and Turkmenistan parts of south Caspian, the Pliocene strata have been deposited as fluvial-deltaic sediments by Paleo-Volga, Paleo- Kura and Paleo-Uzboy rivers whereas the Pliocene strata of Khazar-1 well were deposited in an enclosed marine basin. Despite the fact, the most migration has been occurred in the Pliocene time, when this sediment was not deposited. The Pliocene sediments on the Iranian side of the SW Caspian corner cannot be considered as reservoir and source rock since these sediments have not enough organic material to generate hydrocarbon. In Khazar-1 at depths around 1040, 1062, 1600 to 1700, 1700 to 2400, and 2900 to 5570 meters gas and water flow are observed within the drilling fluid. Laboratory analysis confirms oil shows in the deep horizons of the Cretaceous sediments (more than 5500 meters), The gas is absorbed, although the higher horizons also have evidence of this. At the end of the Pliocene time, sedimentation went under stable hydrodynamic and high salinity water conditions. The tectonic conditions were stable, except for volcanic processes in Elbrus and the Caucasus. The process of transgression continued in a stable hydrodynamic regime on the Apsheronian period. Therefore, clayey sediments and thin-layered clayey marls were deposited. During the Quaternary period, there was a continuous sedimentation process in the South Caspian Sea, including the Iranian shelf, and carbonate clays and thin-walled marls dominated the cross- section. It should be noted that since older sediments have not been studied in the area (below Upper Cretaceous), it is of great interest to assess their prospects Post Pliocene sediments of Khazar-1 like Lankaran-Talysh Deniz has been deposited in a brackish water environment. Most of the sandstone of Khazar-1 well has a clayey cement. Except few HC shows, oil and gas has been not found in Khazra-1 and Talysh Deniz and onshore Shahabad-1 wells. In
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  16 Lankaran Deniz structurethere was not deep exploration drilling. The Cretaceous sediments of Khazar- 1 well has also no signs of important reduction strata. subject Rock unit Khazar-1 well Lankaran-Talysh Deniz Dominant lithology Pleistocene+Holocene Eopleistocene (Apsh) Akchagylian strata Upper Pliocene (Productive/Red series) Clay, siltstone, coquina Claystone, shale Clay and anhydrite evaporite Clay with inter- layer of coquina, detrital limestone, sand, clay, shale, sand Clay with a thin interlayer of sand and ash Sand, shale, loam, siltstone. Sedimentary environment Upper Pliocene (Productive/Red series) Evaporitic enclosed basin Fluvial-deltaic Table 1. Comparison of sedimentary environment and lithology of Lankara-Talysh and Khazar -1 well Conclusions: The analysis of the borehole, seismic data, and biostratigraphy confirmed that the Tertiary sediments consist of fluvial- deltaic–lacustrine sediments deposited in the isolated South Caspian Basin, particularly in the study area by several river systems. Quaternary sediments have been deposited in a brackish water environment. According to seismic the Pliocene and Quaternary sediments unconformably overlie more ancient formations, until the Mesozoic sediments are located at a relatively shallow depth. The Miocene sequences below the middle part of Pliocene Pereryva formation are pinching out against the basin margin. The thickness of these series increases stepwise across the main structures giving evidence of a rift-system developing at the beginning of major subsidence in the South Caspian Basin during the early Tertiary. The time window for charging of Talysh-Lankaran from the mature oil kitchen area further east was small, and the capacity of the structure at that time interval was limited. TDX1 well confirms effective charge to the adjacent Lankaran structure to be the key risk element, however, a flat spot in the PodKirmaku sands could point to effective charge. No hydrocarbon discovery found in Lankaran- Deniz, Talysh-Deniz, and Khazar structures except little oil and gas show due to several geological reasons such as a reservoir property, vertical, and lateral migration problem. References: Berberian, M., King, G.C.P., 1981. Towards a paleogeography and tectonic evolution of Iran. Can. J. Earth Sci. 18, 210–265. Berberian, M., 1983, The southern Caspian: A compressional depression floored by a trapped, modified Dumont, H.J., 1998. The Caspian Lake: History, Biota, Structure, and Function. Limnology and Oceanography 43, 44–52. Glumov, I.F.,Malovitskiy, Y.P.,Novikov, A.A., Senin, B.V.,2004.Regionalnaya geologiya I nefteqazonosost Kaspiyskogo moray, Moskva, Nedra, 342 p.
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  17 Kakrodi, A.A., Kroonenberg,S.B., Hoogendoorn, R.M., Mohammad Khani, H., Yamani, M., Ghassemi, M.R., Lahijani, H.A.K., 2012. Rapid Holocene sea-level changes along the Iranian Caspian coast. Quaternary International 263, 93e103. A.A. Kakroodi, S.A.G. Leroy, S.B. Kroonenberg, H.A.K. Lahijani, H. Alimohammadian, I. Boomer, A. Goorabi., 2015. Late Pleistocene and Holocene sea-level change and coastal paleoenvironment evolution along the Iranian Caspian shore. Marine Geology 361 (2015) 111–125 Kazancı, N., Gulbabazadeh, T., Leroy, S.A.G., Ileri, O., 2004. Sedimentary and environmental characteristics of the Gilan–Mazenderan plain, northern Iran: influence of long- and short-term Caspian water level fluctuations on geomorphology. Journal of Marine Systems 46 (1–4), 145–168) oceanic crust: Canadian Journal of Earth Sciences,v. 20, p. 163–183. Leroy, S., Chalie, F., Wesselingh, F., Agpe, K.,2018. Multi-proxy indicators in a Pontocaspian system: a depth transect of surface sediment in the SE Caspian Sea. Geologica Belgica 21(3-4):143 DOI: 10.20341/gb.2018.008 Narimanov, A.A., 1993. The Petroleum Systems of the South Caspian Basin. Norwegian Petroleum Society (NPF) special publication 3. Elsevier, Amsterdam, pp. 598–608 Smith-Rouch, L.S., 2006. Oligocene-Miocene Maykop/diatom total petroleum system of the south Caspian Basin province, Azerbaijan, Iran, and Turkmenistan. U.S. Geol. Surv. Bull. 2201, 1–27. Yassini I., 1986. Ecology, paleoecology, and stratigraphy of ostracodes from upper Pliocene & Quaternary deposits of the south Caspian Sea, North Iran. Proceedings of the International Symposium on Shallow Tethys 2, Wagga, pp. 475–497. Xülasə Cənubi Xəzər şelfinin cənub-qərb hissəsi çox zəif tədqiq edilmişdir. Dənizdə qazılan çoxsaylı dayaz mühəndis geoloji və dərin kəşfiyyat quyularından götürülən məlumatlar, sözügedən ərazinin Üçüncü- Dördüncü dövr çöküntülərinin geologiyası haqqında faydalı məlumatlar vermişdir. Kern, karotaj, seysmik məlumatları və biostratiqrafiya Üçüncü dövr çöküntülərinin qapalı Cənubi Xəzər hövzəsində, xüsusən də çay sistemlərinə bitişik tədqiqat zonasında çökmüş flüvial-delta-lakustrin çöküntülərdən ibarət olduğunu təsdiqləmişdir. Dördüncü dövr isə duzlu su çöküntüləri şəraitilə xarakterizə olunur. Xəzərin cənub-qərb hissəsindəki açıq dəniz körfəzlərində yaranan deltalar və dayaz su fasiyaları üçün "qısa" müddətli dərin və dayaz su dəniz çöküntüləri xarakterikdir. Əgər Mezozoy çöküntüləri də nisbətən dayaz dərinlikdə yerləşərsə Pliosen və Dördüncü dövr çöküntüləri qeyri-uyğun yatımla qədim çöküntülər üzərində yatir. Lənkəran-Talış-Dəniz strukturlarında, Miosen və orta Pliocenin Fasilə çöküntüləri çökəkliyin kənarına döğru pazlaşır. Bu seriyanın qalınlığı əsas strukturlar boyunca pilləvari şəkildə artır. Bu da Cənubi Xəzərin ilk Üçüncü dövründə böyük bir çökmə procesinin başlanğıcında inkişaf edən riftəmələgəlməni göstərir. Kollektorlar, şaquli və yanal miqrasiya problemləri kimi bir neçə geoloji səbəblərə görə kiçik neft və qaz işartıları istisna olmaqla, Xəzərin cənub-qərbində heç bir karbohidrogen tapılmamışdır. Аннотация Юго-западная часть шельфа Южного Каспия изучена очень плохо. Данные, изученные по многочисленным морским мелководно- инженерным и глубоким разведочным скважинам, предоставили полезную информацию о геологии Третично-Четвертичных отложений рассматриваемой участки. Каротаж, сейсмические данные и биостратиграфия подтвердили, что Третичные отложения состоят из флювиально-дельтово-озерных отложений, отложившихся в изолированном Южно-Каспийском бассейне, особенно в районе исследования рядом с речными системами. Четвертичный период характеризуется наличием солоноватоводных
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  18 отложений. «Короткая» серияморских осадков глубоководной и мелководной фаций открытых морских заливов, дельты и морских мелководий характерна для юго-западной части Каспия. Плиоценовые и Четвертичные отложения несогласно перекрывают более древние образования, пока Мезозойские отложения не располагаются на относительно небольшой глубине. В структурах Ленкоран-Талыш-Дениз Миоценовые толщи ниже средней части Плиоценовой свита Перерыва выклиниваются по окраину впадины. Мощность этой серии увеличивается ступенчато по основным структурам, что свидетельствует о рифтовой системе, развивающейся в начале крупного погружения Южного Каспия в раннем Третичном периоде. На юго-западе Каспия не обнаружено углеводородов, за исключением небольших проявлений нефти и газа, что связано с несколькими геологическими причинами, такими проблемами как коллекторы, вертикальные и боковые миграции.