Geochemistry of hydrocarbons of the Terek-Caspian trough

Tari

et al. 2018

Initial crustal collision between Africa and Eurasia in the middle Eocene – early Oligocene enclosed a semi‐restricted Paratethyan seaway of linked basins and platforms across a region stretching from the Eastern Alps to the South Caspian Sea. As the African Plate continued to advance north during the later Neogene, the seaway shrank into a series of more isolated basins separated by the rising Alpine – Carpathian – Caucasus fold‐thrust belts. Organic‐rich oil‐prone Paratethyan source rocks of middle Eocene (Kuma Formation and equivalents) and Oligocene – early Miocene (Maikop and Menilite Beds) ages, and more gas‐prone post‐orogenic mid‐upper Miocene shales, subsequently charged over 2500 accumulations across the region with combined recoverable reserves of 95 billion brl oil‐equivalent (B boe). These accumulations are clustered in discrete petroleum provinces, each with a distinct tectono‐stratigraphic architecture and comprised of one or more petroleum systems. The provinces can be grouped into five broad categories: Average Reserves Average Field Sizes Fold‐thrust Provinces60,980 MMboe2–590 MMboeSub‐thrust Provinces255 MMboe3.4 MMboeForeland Provinces18,671 MMboe2–77 MMboeIntermontane Provinces13,122 MMboe1–40 MMboeBlack Sea back‐arc Province> 1391 MMboe>33 MMboe The productivity of each province (estimated very approximately from the number of barrels oil equivalent / square kilometre) is extremely variable, and its relationship with the geological factors controlling hydrocarbon entrapment and retention is complex. The most critical of these factors appears to be the quality and distribution of source rocks and post‐charge structural modification.

Section: Principal Source Rocksmentioning

confidence: 99%

Section: Principal Source Rocksmentioning

confidence: 99%

Petroleum Provinces of the Paratethyan Region

Boote¹,

Tari

et al. 2018

“…Oligocene to Early Miocene (Maikopian) source rocks are widely distributed within the Paratethys, and comprise the main source for oil in a number of basins including the Alpine Foreland Basin (Gratzer et al, 2011), the Carpathian Basin (Kotarba et al, 2007), the Caucasus Foredeep basin (Ulmishek, 2001;Yandarbiev et al, 2017), the Kura Basin and the South Caspian Basin (e.g. Inan et al, 1997;Katz et al, 2000;Guliyev et al, 2003).…”

Section: Oligocene Early Miocene Maikopian Source Rocksmentioning

confidence: 99%

Paratethyan Petroleum Source Rocks: An Overview

Popov

Ćorić

et al. 2018

The Paratethys area extends from Central Europe to the borders of the Caspian Sea in Central Asia and hosts a significant number of petroleum provinces, many of which have been charged by Eocene to Miocene source rocks of supra‐regional significance. These include highly oil‐prone Middle Eocene marls and limestones in the Eastern Paratethys (Kuma Formation and equivalents) which are several tens of metres thick. Estimates of the source potential index (SPI) indicate that the Kuma Formation in the northern Caucasus and the Rioni Basin (Georgia) may generate 1 to 2 tons of hydrocarbons per square metre (tHC/m2). This implies that the Kuma Formation may also be an important and additional source rock in the eastern Black Sea. Oligocene and Lower Miocene pelitic rocks (Maikop Group and equivalents) are considered to be the most important source rocks in the Paratethys. Vertical variations in source potential record different stages of basin isolation that reached a maximum during the Early Oligocene (NP23) Solenovian Event. However major variations exist between different sub‐basins in the Central and the Eastern Paratethys. In the Central Paratethys, the highest quality source rocks occur in the Carpathian Basin where the Menilite Formation, several hundreds of metres thick, can generate up to 10 tHC/m2. Locally the Menilite Formation is about 1500 m thick and continues into the Lower Miocene. In these settings, the Menilite Formation can generate approximately 70 tHC/m2. In the Alpine Foreland Basin (Schöneck and Eggerding Formations) and the Pannonian Basin (Tard Clay Formation), oil‐prone source rocks are restricted to the Lower Oligocene. In the Eastern Paratethys, the best source rock intervals of the Maikop Group are typically associated with the Early Oligocene Solenovian Event. By contrast, with the exception of the Kura Basin in Azerbaijan, the potential of Upper Oligocene and Lower Miocene rocks is often limited. In total, the Maikop Group may generate up to 2 tHC/m2 in the North Caucasus area and 4 tHC/m2 in the Rioni Basin. A particular source rock facies is found in the Western Black Sea where diatomaceous rocks with good oil potential accumulated in the Kaliakra Canyon during Early Miocene time. This facies may generate up to 8 tHC/m2, but is probably limited to shelf‐break canyons. Middle and Upper Miocene rocks are the main source for oil and thermogenic gas in the Pannonian Basin System, and also contributed to thermogenic hydrocarbons in the Moesian Platform and the South Caspian Basin. In addition, Upper Oligocene and Miocene rocks are the source for microbial gas in several basins including the Alpine and Carpathian foredeeps.

“…this study this study + Yandarbiev et al (2017a) Yandarbiev et al (2017a the Dagestan Promontory and the Maritime Zone (Fig. 4).…”

Section: Studied Fieldsmentioning

confidence: 92%

“…Although the NE Caucasus is one of the oldest oil and gas producing regions in the world, geochemical information is limited and the presence of different oil families is still unclear as is the source of the oils (e.g. Yandarbiev et al, 2017a). Potential source rocks include argillaceous limestones and shales in the Triassic succession; thick marine shales of Middle Jurassic (Bajocian) age; and anoxic marine mudstones in the Kuma Formation and the lower (Oligocene) part of the Maikop Group (Ulmishek, 2001;Sachsenhofer et al, 2017;2018b).…”

Section: Introductionmentioning

confidence: 99%

Geochemistry of Oils in the Terek‐caspian Foredeep and Prikumsk Swell, Ne Greater Caucasus, Southern Russia

Yandarbiev

Ajuaba

et al. 2021

Hydrocarbon reserves of the order of 1140 MM brl oe have been identified in the northern foreland of the eastern Greater Caucasus, principally in the Terek-Caspian fold-and-thrust belt and the Prikumsk Swell in the north of the Terek-Caspian foredeep. Despite the great economic significance of these areas and their long exploration history, the origin of the hydrocarbons is still poorly understood. In the present paper, geochemical data from 73 oil samples representing 28 fields are used to investigate the presence of oil families and to correlate the oils with potential source rocks.Biomarker composition of oils in Cretaceous and Miocene reservoirs in the Terek-Caspian fold-and-thrust belt is mainly controlled by reservoir depth (100-5700 m) and maturity (0.70-1.15 %R o ), and it is therefore difficult to separate maturity and facies effects. For example, a downward increase in diasterane/sterane ratios may indicate a change in source rock facies or may be attributed to increasing maturity. Some shallow oils are biodegraded. The presence of short-chain n-alkanes in biodegraded oils indicates recent hydrocarbon migration. Biomarker data (e.g. the presence of oleanane) and compound-specific isotope data suggest that the Khadum Formation in the lower part of the Maikop Group is the main source rock. However data from Cretaceous and Paleogene organic-rich rocks, which may also have contributed to the accumulated oils, are urgently needed in order to quantify their possible input.In the Prikumsk Swell, at least two oil families, characterized by low and high C 28 /C 29 sterane ratios respectively, can be distinguished in reservoir rocks of Triassic to Cretaceous age. Most oils are characterized by low C 28 /C 29 sterane ratios and the absence of oleanane ("Group B oils"). These characteristics suggest a pre-Upper Cretaceous source for the oils, which is also supported by the geological setting. Hierarchical cluster analysis suggests the presence of four sub-groups (Sub-Groups B1 to B4). Typically, biomarker ratios in oils in Cretaceous reservoirs are more uniform than those in Triassic and Jurassic reservoirs. Potential source rocks include Lower Triassic deep-water clayey limestones and shales as well as Middle Jurassic and Aptian-Albian marine shales. Three oil samples from Triassic and Cretaceous reservoirs form a separate oil family ("Group A"), which is genetically related to oils from the Terek-Caspian fold-and-thrust belt. Group A oils have high C 28 /C 29 sterane ratios and in general contain at least some oleanane. A contribution by Cenozoic source rocks to Group A oils is likely.