Anomalous Section Research Articles

Structure and genesis of the Achimov olistostromic strata of Western Siberia

The question of the genesis of the anomalous Bazhen-Achimov zones remains to be one of the most controversial problems in Western Siberia. By now, about dozen hypotheses of the sedimentary environment of this specific formation have been proposed. However, none of these hypotheses is generally accepted. All hypotheses have been classified by genesis and their critical analysis is given in the article. The solution is closely related with experience of the geological exploration works, since the prospects of oil and gas are associated with these deposits. The article highlights the key features of the structure of the anomalous section’s zones based on drilling and seismic data. The classification of the hypotheses is given and the features of sedimentation in the Bazhenov and Achimov times are highlighted. An accumulated data has allowed us to substantiate the olistostromous genesis of the anomalous section. Based on a set of data, including paleogeographic, sedimentological, paleotectonic reconstructions, a principal detailed model of the sedimentary environment of olistostromes is proposed for the first time. The proposed model seems to be the most logical, supported by the actual data known to date, is the most universal and fits into the paleogeographic situation and tectonic regime that prevailed in the Achimov time.

Anomalous 234U/238U isotopic composition in Southern Ocean sediments

Uranium is a redox-sensitive trace element that under certain sedimentary conditions will reflect changes in past biological productivity and/or deep ocean ventilation. Applications for the isotopic composition of U (234U:238U activity ratio, δ234U or the per mil deviation from secular equilibrium) as a paleoceanographic proxy, however, remain largely unexplored in pelagic sediments. We present δ234U of bulk U for a 504-kyr record of South Atlantic core ODP 1094, a record that has exhibited sensitivity to bottom water formation with minimal 238U remobilization due to changes in redox condition. Sedimentary δ234U at time of burial was modeled given authigenic and detrital sources, where it was found that δ234U has a reoccurring pattern of anomalous behavior around deglacial transitions. In many cases, the anomalous δ234U compositions in sediment exceeded seawater, which is not consistent with its expected sources. A mass balance of 234U across these anomalous sections showed that vertical rearrangement of 234U can explain anomalous sedimentary δ234U during Marine Isotope Stage (MIS) 7/8 and 11/12 transitions, as well as partially during MIS 5/6 and MIS 9/10. The distribution of these anomalies is likely consistent with the idea that deglacial spikes in aU, resulting from periods of high organic carbon delivery and thereby strong reduction in the sediments, act as a persistent sink of 234U alpha-recoiled from vertically adjacent sediment layers after burial. While this mechanism explains the negative δ234U anomalies, there is a large subset of positive δ234U anomalies that cannot be explained by vertical diffusion of 234U in pore waters alone. This excess 234U points to an extremely high δ234U source to seawater during deglaciation or additional diagenetic effects such as diffusion from lateral heterogeneity in the redox state of sediment at depth. We find that δ234U of pelagic sediment may be useful to identify fine-scale pore water migration of alpha-recoil products.

A model of a shear landslide wedge with subsequent hydraulic rupture as an explanation for the formation of an anomalous section of the Bazhenov formation in the north of Western Siberia. Part 2. Description of the mesostructural complexes in the core and the model of the anomalous section formation

A new anomalous section of the Bazhenov formation was described on the territory of the Urengoydeposit in the northern part of Western Siberia. This article presents descriptions of mesostructural complexes in the core, on the basis of which a new model for the formation of the anomalous section of the Bazhenov formation was proposed. It was found that the formation of the mesostructural complexes occurred at different stages of the landslide and when its body moved along the uneven surface of the detachment. In the formation of large injection “sand veins” in the studied section, the main role was probably played by the landslide-induced grain flow from the coastal shallow water area. The penetration of its sandy material into the rocks of the Bazhenov formation and, to a lesser extent, the Achimov formation occurred due to the energy of hydraulic shock and hydraulic fracturing along layer-by-layer and secant fractures.

A Model of a Shear Landslide Wedge with Subsequent Hydraulic Rupture as an Explanation for the Formation of an Anomalous Section of the Bazhenov Formation in the North of Western Siberia. Part 2. Description of the Mesostructural Complexes in the Core and the Model of the Anomalous Formation of the Section

A Model of a Shear Landslide Wedge with Subsequent Hydraulic Rupture as an Explanation for the Formation of an Anomalous Section of the Bazhenov Formation in the North of Western Siberia. Part 2. Description of the Mesostructural Complexes in the Core and the Model of the Anomalous Formation of the Section

A model of a shear landslide wedge with subsequent hydraulic rupture as an explanation for the formation of an anomalous section of the Bazhenov formation in the north of Western Siberia. 1. Section description, lithology, palynology

А new anomalous section of the Bazhenov formation was described in the territory of the Urengoy oil and gas condensate field in the northern part of Western Siberia. Article 1 presents the results of the lithological description of the core, the division of the main rocks into lithotypes, the results of granulometric and palynological analyzes. It was revealed that gray-colored sandy-clay deposits and sandy vein-like bodies are younger than the host rocks of the Bazhenov Formation, represented by black kerogen-siliceous-clay rocks. On the basis of palynological studies, as well as the similarity of the mineral and granulometric compositions of the studied sandstones with the sandstones of the Achimov strata, it was assumed that the studied clastic rocks belong to the Achimov deposits, which were intruded into the deposits of the Bazhenov Formation.

A Model of a Shear Landslide Wedge with Subsequent Hydraulic Rupture as an Explanation for an Anomalous Section of the Bazhenov Formation in the North of West Siberia. Article 1. Section Description, Lithology, and Palynology

A Model of a Shear Landslide Wedge with Subsequent Hydraulic Rupture as an Explanation for an Anomalous Section of the Bazhenov Formation in the North of West Siberia. Article 1. Section Description, Lithology, and Palynology

Ключевые моменты интерпретации сейсмических данных внутри зон аномального разреза баженовской свиты на примерах Поточной, Спорышевской, Выинтойской и Ватинской зон.

The Bazhenovo horizon of Western Siberia has traditionally been one of the objects most studied by geologists and geophysicists in recent decades in Russia. However, along with the more familiar "classical" structure, there are areas where gray-colored inclusions of sandy-silty-clayey deposits are present between the carbonate-clayey-siliceous rocks of the Bazhenovo Black Shales Formation. Such sections geologists call "anomalous". The paper describes the application of the spectral decomposition method for detailing the structure of anomalous sections zones of the Bazhenovo Formation or in another words Giant Sand injection Complex (GSIC) of the Ob river region. Combining the results of dynamic interpretation of 3D seismic data with well logging data for a vast fund of exploration and production wells made it possible to build a seismogeological model of the of the Ob river region GSIC in the Potochnaya area. The clue approach was tested on the Sporyshevskaya and Vyyntoyskaya, Vatinskaya areas, which were much less explored by drilling. The listed zones were formed at different geological times, belong to different regional clinoforms, but have common patterns of structure, which is reflected in the seismogeological model of the Ob river region GSIC. The model describes the distal and proximal parts of the intrusion, which were formed in the Neocomian time, when gravity-driven flows of sandy-silty material injected and spread inside high-bituminous Jurasic Bazhenovo formation Black Shales. Within the proximal part gravity-driven flows were accompanied by slumps of more clayey rocks. The dimensions of these flows and slumps, their location over the area are shown, their mapping in the 3D seismic data is discussed. In this work, we managed to get closer to solving the problem of predicting the development of sandy downward intrusions. There are oil reservoirs in the Ob river region GSIC, but they are insufficiently studied.

Types of interaction between rocks of Achimov sequence and Bazhenov formation

Many fields in the northeastern part of Surgut oil and gas region were discovered in 1960s-1970s. Currently, because to the development of reserves of large deposits of simple structure the restoration of the resource base and maintenance of the production level of oil and gas producing organizations are the main tasks. Its implementation is possible due to the development of new territories, increasing the depth of prospecting drilling, additional exploration of deposits of complex structure.Residual reserves of deposits in the studied area are confined to Achimov sequence and reservoirs in anomalous section of the Bazhenov formation.The article considers the types of deposits in Achimov sequence with normal and anomalous structure of Bazhenov formation. The author proposes a classification of oil deposits in the fondoform part of clinoforms. This classification clearly shows the possible relationship between Achimov sequence and the underlying bituminous deposits of Bazhenov formation.Some deposits associated with reservoirs in anomalous section of the Bazhenov formation may be missed targets; therefore, additional exploration is required. Since the reservoirs of Achimov sequence and anomalous section of the Bazhenov formation have different properties, it is necessary to differentiate them when planning geological and technological measures to extract oil.

Integrated approach to the typification and localization of deposits of the anomalous section of the Bazhenov formation of the Frolov oil and gas region

Introduction. The subject of the study of this work is the deposits of the anomalous section of the Bazhenov formation (ASB) of Western Siberia, the disturbed occurrence of which was recorded by 2D, 3D seismic exploration and borehole data at many fields of the Frolov oil and gas region. The research area unites the company’s assets in the KhMAO and the Tyumen region, which are part of the large hydrocarbon cluster “ZIMA”. 
 
 Aim. In order to typify various complexes of rocks of the Bazhenov formation and further localization of deposits, a comprehensive core analysis, GIS and seismic studies were performed. 
 
 Materials and methods. According to the results of lithological study of the core and petrophysical interpretation of logging diagrams, have been identified various types of rocks in the interval of the Bazhenov formation. According to the results of the interpretation of the seismic survey materials, contoured zones that differ in the wave pattern by different coherence of the axes of common phase. The revealed differences in seismic sections compared with borehole data and geological bodies mapped based on the obtained patterns. 
 
 Results. Based on a comprehensive interpretation of the core, GIS and seismic studies, established the zonality of the distribution of various types of deposits of the Bazhenov formation, the relationship of the development of ASB zones with the introduction of Early Cretaceous sedimentary bodies and showed the introduction of detrital material from the overlying rocks. 
 
 Conclusions. The authors of the article conclude that the development of anomalous sections of the Bazhenov formation involves several stages of the introduction of landslide bodies of overlying rocks, according to the gradation of Neocomian clinocyclites in the north-west direction. Within the study area, mapped three large landslide bodies in the Bazhenov formation interval, each of which was formed an internal zonality and because of the introduction of rocks from the overlying interval.

Petrographic study of oil migration on the example of Imilorskoye field (Kogalymsky petroleum region, Western Siberia)

Subject. This paper presents the results of studies of the mechanism of primary oil migration in the boundary sediments of the late Jurassic (Bazhenov formation)–early Cretaceous (Achimov pack) on the example of the well 431Р of the Imilor field. Materias and methods. Based on the working hypothesis of fluid fracturing as the main mechanism of primary oil migration, using optical-petrographic analysis, supplemented by geochemical research methods, systems of interconnected microcracks in the Tithonian-lower Berriasian and early Valanginian deposits were studied. Results. It is established that the investigated cracks occurred in three stages: 1) formation of primary sedimentary-lithogenetic fissures as a result of dehydration of clays in the stage of diagenesis and hydraulic fractures in the implementation of the Achimov of terrigenous rocks; 2) partial healing of cracks with secondary minerals in the catagenesis; 3) restoration of patency of the cracks in the generation of large amounts of free hydrocarbons of protopetroleum. It is shown that the migration of hydrocarbons generated by the formation occurred both within the Bazhenov formation itself and through a system of interconnected cracks in the contact zone of the Bazhenov formation with the Achimov formation. Conclusion. A detailed study of the mechanism of oil migration allows us to expand our understanding of the reservoir properties of the oil column, which in the future will allow us to forecast the reservoir properties of the Bazhenov formation including in the zones of anomalous sections (for example, in the Kogalym region).

Методические приемы детальной корреляции разрезов скважин при изучении геологического строения верхнеюрских и нижнемеловых комплексов пород (на примере Тевлинско-Русскинского нефтяного месторождения Сургутского свода) Часть 1. Обоснование особенностей фор

Методические приемы детальной корреляции разрезов скважин при изучении геологического строения верхнеюрских и нижнемеловых комплексов пород (на примере Тевлинско-Русскинского нефтяного месторождения Сургутского свода) Часть 1. Обоснование особенностей фор

Комплексное обоснование тектонической природы аномальных разрезов верхнеюрской баженовской свиты и нижнемеловой ачимовской толщи Западной Сибири. Часть 1. Аномальные разрезы верхнеюрской баженовской свиты и нижнемеловой ачимовской толщи

Комплексное обоснование тектонической природы аномальных разрезов верхнеюрской баженовской свиты и нижнемеловой ачимовской толщи Западной Сибири. Часть 1. Аномальные разрезы верхнеюрской баженовской свиты и нижнемеловой ачимовской толщи

Комплексное обоснование тектонической природы аномальных разрезов верхнеюрской баженовской свиты и нижнемеловой ачимовской толщи Западной Сибири. Часть 2. Клиноформы нижнемеловых отложений

Комплексное обоснование тектонической природы аномальных разрезов верхнеюрской баженовской свиты и нижнемеловой ачимовской толщи Западной Сибири. Часть 2. Клиноформы нижнемеловых отложений

A petrographic study of the genesis of anomalous sections in the Bazhenov Formation, the Imilor deposit, Western Siberia

Research subject. Anomalous sections present in the oil- and bituminous-bearing Bazhenov Formation (BF), in the central areas of the West Siberian basin, are considered to have emerged due to the injection of plastic pulp masses from the sedimentation slope into weakly lithified basal deposits. The aim of this research was to evaluate the as-emerged rocks by analyzing their composition and structure at the macro- and micro- levels. Materials and methods. We investigated reference well sections in the Imilor deposit to elucidate the interaction of the rocks with sandy-clay landslide pulp, their volumetric weight, ductility or brittleness, caused by the presence or absence of a continuous mineral frame. Results. According to core and well logging data, nine regional packs were distinguished in the BF stratotype. The maximal depth of the natural hydraulic fracturing of the rocks is explained by their high bulk density. The lateral movement of the main slump mass is found to have occured on the stratigraphic level of the first and second BF packs, since these layers possessed zero-buoyancy with regard to the injected pulp under their approximate equality in terms of bulk density. The traces of such active movements were revealed in rock samples from the walls of horizontal cracks in the form of clay intrusions having a thickness of about 0.1 mm and strict orientation of all micro-crystals along the walls and the flow. It is shown that inclusions of the rocks under investigation (bazhenits) in BF are generally characterized by their initial stratigraphic sequence, which is confirmed by the sequential disintegration of proto-bazhenit plates during the process of BF up-floating on a growing sedimentation slope. During the disintegration of the lithified and non-lithified layers of radiolarits, the former crumbled due to alternating loads, while the latter - mobile radiolarites - were represented by the hydraulic fracturing liquid, along with quicksand. Conclusion. A detailed petrographic study of core samples from intact deposits of the Bazhenov and George Formations and their anomalous sections have allowed their layer-by-layer comparison to be confirmed the landslide hypothesis and to be derived the information on the degree of lithification of the BF strata during the formation of its anomalous sections.

КРИТЕРІЇ ПОДІБНОСТІ ЛІНГВІСТИЧНИХ МОДЕЛЕЙ

Важливою складовою лінгвістичного підходу до виявлення аномалій у часових рядах є критерій, за яким оцінюється подібність двох моделей. Наявність аномалії встановлюється шляхом порівняння моделей. Саме від вибору критеріїв залежить можливість застосування лінгвістичного підходу до аналізу часових рядів різної природи. Для вчасної реакції на ситуацію важлива швидкість виявлення аномалії. Вибір критеріїв залежить від можливості застосування мовного підходу до аналізу часових рядів різного характеру. Розглянуті основні метрики схожості текстів Геммінга, Левенштейна, Джаро-Вінклєра та ін.

The influence of natural and anthropogenic factors on grain size distribution along the southeastern Baltic spits

The influence of natural and anthropogenic factors on the distribution of sand grain size along sandy beaches is assessed, based on study of three spits of the southeastern Baltic Sea: the Curonian, Vistula and the Hel. 330 sand samples were collected from the beach and foredune at 1 km intervals. Our findings show that although the three spits have some characteristics in common, e.g. a predominance of fine- and medium-grained marine sand on their beaches and foredunes, the grain size distribution patterns of the recent sediments along these spits differ significantly. The key factors determining the grain size distribution include the dominant hydrometeorological regime, anthropogenic activity and geological framework. Trends in the mean grain size differentiation along the Vistula and Curonian spits directly correlate with the direction of the longshore sediment transport: as the distance from sources of the longshore sediment transport increases, the size of sand particles, both on the beach and the foredune, decreases. By contrast, on the Hel Spit, this pattern is disturbed in areas of hydrotechnical construction and artificial beach nourishment. Sand differentiation along the beach can also be predetermined by the geological framework, particularly in lithologically anomalous sections, such as the JuodkrantĹ settlement on the Curonian Spit.

ANOMALOUS SECTIONS OF BAZHENOV SUITE: A VIEW THROUGHFIFTY YEARS AFTER DISCOVERY

It has been almost fifty years that the so called Bazhenov suite anomalous sections, i.e. formations distinguished by sandy-aleuritic inclusions in Bazhenov bituminous clay attract the wide range of geologists and geophysicists who circulate innumerable, often exotic assumptions concerning generation of anomalous sections. Integrated analysis of mixed geological and geophysical data on anomalous sections formation proved that the initial definition of the former as submarine landslide dislocation by K. I. Mikulenko and G. B. Ostry remains most accurate.

Goethite Concentration Variations in the Red Clay Sequence on the Chinese Loess Plateau

AbstractThe Goethite is a common magnetic mineral in soils and is important for understanding past climatic and environmental change. Although goethite concentration records are available for the Quaternary loess‐paleosol sequences from the Chinese Loess Plateau (CLP), no goethite concentration record is available for the underlying Red Clay sequence. Here, we generate a record of goethite concentration from the Chaona section on the CLP and investigate the relationship between goethite and ferrimagnetic mineral concentration and climate parameters on the Red Clay sequence deposited from 6 to 2.7 Ma. We found that increasing goethite concentration generally corresponds to decreasing magnetic susceptibility for the Red Clay sequence, with the exception of an anomalous section from 4.3 to 3.7 Ma where both records show increasing trends. Precipitation seasonality could explain this opposite variation pattern between magnetic susceptibility and goethite concentration in the Red Clay sequence. From 3.6 to 2.7 Ma, goethite concentration has a decreasing trend while magnetic susceptibility increased, which we interpret as more seasonally distributed precipitation associated with intensification of the East Asian summer monsoon (EASM). Similar pattern was observed from 0.65 to 0 Ma from the Lingtai section. Taken together, the goethite record reveals that the EASM experienced two stages of rapid intensification with apparent seasonally distributed precipitation since 6 Ma.

FEATURES OF THE STRUCTURE AND OIL AND GAS POTENTIAL OF LOWER CRETACEOUS AND UPPER JURASSIC SEDIMENTS IN WESTERN AREAS OF WESTERN SIBERIA

The features of the geological structure and oil and gas potential of the Bazhenov-Abalak oil and gas complex are discussed. Based on new geological and seismic data, using an integrated approach, the zones of distribution and the boundaries of thinning out of silty sand reservoir rocks of Vogulkinskaya strata were mapped, four traps and two zones (Ourinskaya, Eastern Tolumskaya), which are perspective for hydrocarbon deposits search, were distinguished. In Bazhenov horizon, the zones of development of anomalous sections and bituminous sediments were mapped, laying above Bazhenov formation, which are perspective for hydrocarbon deposits search. Recommendations for further exploration are given.

Information entropy as an identifier in rock mass structure determination using low-frequency radars

The procedure of revealing water-saturated areas near underground openings by the data of radars with resistive-loaded antennas is developed. The key identifying parameter (attribute) of the procedure is the information entropy showing specific character of function of distribution of radar trace amplitudes. It becomes possible to distinguish anomalies in the profiles using the attribute after amplitude equalization. The procedure of processing of traces is described and exemplified, and the reasons of the entropy parameter efficiency are explained. For the comparison, the author considers alternative identifying parameters that appear less efficient as against the entropy attribute either for their weak capability to reveal anomalous sections in profiles or for the low interference immunity.