An Integrated Approach to Well Logging: The Case of the Bazhenov Formation

New geological structures – displaced blocks of salt diapirs’ overburden – were identified in the axial part of the Dnieper-Donets basin (DDB) beside one of the largest salt domes due to modern high-precision gravity and magnetic surveys and their joint 3D inversion with seismic and well log data. Superposition of gravity lineaments and wells penetrating Middle and Lower Carboniferous below Permian and Upper Carboniferous sediments in proximity to salt allowed to propose halokinetic model salt overburden displacement, assuming Upper Carboniferous reactivation. Analogy with rafts and carapaces of the Gulf of Mexico is considered in terms of magnitude of salt-induced deformations. Density of Carboniferous rocks within the displaced flaps evidence a high probability of hydrocarbon saturation. Possible traps include uplifted parts of the overturned flaps, abutting Upper Carboniferous reservoirs, and underlying Carboniferous sequence. Play elements are analyzed using analogues from the Dnieper-Donets basin and the Gulf of Mexico. Hydrocarbon reserves of the overturned flaps within the study area are estimated to exceed Q50 (Р50) = 150 million cubic meters of oil equivalent.

Carapaces of the Dnieper-Donets Basin as a New Exploration Target

New geological structures - displaced blocks of salt diapirs’ overburden - were identified in the axial part of the Dnieper-Donets basin (DDB) beside one of the largest salt domes due to modern high-precision gravity and magnetic surveys and their joint 3D inversion with seismic and well log data. Superposition of gravity lineaments and wells penetrating Middle and Lower Carboniferous below Permian and Upper Carboniferous sediments in proximity to salt allowed to propose halokinetic model salt overburden displacement, assuming Upper Carboniferous reactivation. Analogy with rafts and carapaces of the Gulf of Mexico is considered in terms of magnitude of salt- induced deformations. Density of Carboniferous rocks within the displaced flaps evidence a high probability of hydrocarbon saturation. Possible traps include uplifted parts of the overturned flaps, abutting Upper Carboniferous reservoirs, and underlying Carboniferous sequence. Play elements are analyzed using analogues from the Dnieper-Donets basin and the Gulf of Mexico. Hydrocarbon reserves of the overturned flaps within the study area are estimated to exceed Q50 (P50) = 150 million cubic meters of oil equivalent.

Gravity Anomalies And Crustal Structure Of The Eastern Part Of The Verkhoyansk Fold-And-Thrust Belt, NE Russia: Evidence From The Junction Area Of The Adycha-Elga And Allakh-Yun Tectonic Zones

The results of geophysical studies of the junction area of the Adycha-Elga and Allakh-Yun tectonic zones of the Verkhoyansk fold-and-thrust belt located on the submerged eastern margin of the Siberian craton are presented. Three structural-mineral complexes are recognized: Archean-Paleoproterozoic, Mesoproterozoic-Middle Carboniferous, and Upper Carboniferous-Early Mesozoic. The Early Jurassic plume-related basaltic volcanism and suprasubduction Late Jurassic-Early Cretaceous granitoids, regional Brungadin and Suntar faults are identified. The goal of the research is to identify deep heterogeneities and clarify the structure of the Earth’s crust in the junction area of the Adycha-Elga and Allakh-Yun tectonic zones of the Verkhoyansk fold-and-thrust belt. The analysis of gravitational anomalies is carried out, their transformations are performed – distinguishing the medium and low-frequency components, the vertical derivative Vzz, and calculating the equivalent distribution of sources of density masses at depth. It is determined that the hidden granitoids of the Adycha-Elga tectonic zone are located mainly in linear zones of decompaction at a depth of about 3.5 km. In the Allakh-Yun zone, a large gravitational minimum has been identified, where it is assumed that there is a magma granitoid chamber occurring at a depth of about 9 km. The model of the deep structure of the territory is based on the analysis of materials on the reference seismic profile 3-DV with the use of gravimetric data and the regional structure of the territory. According to the results of the wave pattern interpretation, the thickness of the lithosphere varies from 41 to 44 km. The thickness of the Upper Carboniferous-Triassic terrigenous rocks is 8-12 km, Mesoproterozoic - Middle Carboniferous carbonate-terrigenous complex is up to 12 km. The Archean-Paleoproterozoic crystalline basement occurs at a depth of 19-21 km. The Conrad discontinuity is assumed at a depth of about 30 km. Intense deformations of the crystalline basement are recognized, and trans-crust faults are identified.

Тrophic structures and the specifcs of paleocoenosis of the Middle-Upper Carboniferous skeletal mounds on the Shchuger River (Northern Urals)

Research subject. Organogenic structures such as the Moscowian-Kasimovian skeletal mounds from the Verkhnie vorota section on the Shchuger River (Northern Urals). Materials and methods. The lithological-paleoecological analysis of biohermal limestones and the determination of their fauna in thin sections (60 samples) and polished slabs (10 samples) taken in outcrops 39 on the Shchuger River, 89 m thick. Results. It is revealed that the Middle-Upper Carboniferous skeletal mounds were characterized by a three-level food chain at three stages of their development. Cyanobacteria, calcimicrobes and green algae were the suppliers of organic matter. Their further consumers were bryozoans, brachiopods, fusulinids, small foraminifera and bacteria. Omnivores and predators were absent. It is found that, heterotrophs were the most common organisms at the stabilization stage, while autotrophs were typical of the colonization stage. The paleocenoses of the Kasimovian skeletal mound had a more extensive composition. Here, each developmental stage was represented by two types of paleocenosis, compared to the Moscowian mound. Conclusions. It is found that the main external abiotic factors that controlled the development of the biocenosis in the sites under study were the hydrodynamic regime and sea level fluctuations. An important internal factor was the development of bio-induced cement on the skeletons of organisms, which contributed to the formation of solid frameworks of buildings. Another internal factor was the widespread occurrence of Anchicodiaceae algae, which caused a decrease in the biodiversity of other groups of organisms. The data obtained allowed us to conclude that a shallow sea basin with a good aeration and low hydrodynamic regime existed in this area in the MiddleLate Carboniferous. A decrease in the basin area in the Late Carboniferous was manifested by a reduction in not only algal taxa, but also the biodiversity of the entire ecosystem.

A further strange Archaeorthoptera from the Moscovian of Nord-Pas-de-Calais (France) (Insecta, Polyneoptera)

The new Archaeorthoptera Duquesnia gallica gen. et sp. nov. Nel & Roques, is described from the upper Carboniferous of Northern France. It shows several putative synapomorphies with the three genera Contracladus Dvořák et al., 2021 (Pennsylvanian of Germany), Nugonioneura (lower Permian of USA), and Avionugonioneura from the Moscovian of Avion (France).

In Situ Stress State of the Ruhr Region (Germany) and Its Implications for Permeability Anisotropy

In this study, we carried out reactivation potential analysis of discontinuities revealed from four exploration boreholes penetrating heavily faulted and folded Upper Carboniferous rock strata of the Ruhr region. We performed this study based on the notion that slip is controlled by the ratio of shear to effective normal stresses acting on a pre-existing plane of weakness in the prevailing stress field configuration. The results of this analysis were supported by indicators of localized fluid flow, both on micro- and macro-scales, which confirm relationship between secondary permeability and in situ stress state in the Ruhr region. Findings from this study, in conjunction with results of destructive laboratory testing, indicate that the steep NW–SE- and NNE–SSW-striking planar discontinuities are likely to be either close to the critical state or critically stressed in the in situ stress configuration in the Ruhr region. These planar structures, as evidenced by indicators of localized permeability, are the main fluid pathways in the studied region. The NE–SW-striking discontinuities, on the other hand, are most likely to be closed and hydraulically inactive in the prevailing stress state. Based on results gained from this study, implications for utilization of deep geothermal energy in the region were discussed.