«OIL AND GAS GEOLOGY» № 3/2017

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Geologiya Nefti I Gaza" ("Oil And Gas Geology") is included by the Higher Attestation Commission in the list of leading scientific journals and publications where the main scientific results of dissertations for the degree of candidate and doctor of sciences

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CONTENTS

 

OIL AND GAS POTENTIAL PROSPECTS AND EXPLORATION RESULTS

 

Skorobogatov V.A. Yenisei-Lena megaprovince: formation, placement and forecasting of hydrocarbon deposits

 

The main features of the development and modern structure of the sedimentary cover of the Yenisei-Lena megaprovince include: the very complex structural and tectonic development of the Siberian Platform in the Riphean-Vendian and post-Cambrian times. The main reasons of the insufficiently high current and “accumulated” efficiency of geological exploration works in the field of prospecting for deposits and their further exploration, and even often unreasonable re-exploration, are very complex tectonic and dynamic development and the modern geological structure of the Siberian Platform and certain regions, areas, zones, local sites; old age of hydrocarbon deposits origination. Oil geological potential value of the Siberian Platform’s subsoil, together with the Mesozoic depressions and sags within the Yenisei-Lena megaprovince, can’t be greater than the gas potential by definition. The real recoverable oil resources are much lower
than the resources of non-associated gas.

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Migurskiy F.A., Yakupova E.M. Substantiation of local studies of oil and gas potential of Predverkhoyanskiy pericratonic sag 

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Insufficient geological and geophysical studies make it difficult to assess the prospects of the oil and gas content of the Predverkhoyanskiy pericratonic sag located on the north-eastern periphery of the Siberian Platform. Interpretation of new (2014–2016) geological and geophysical data will help to accelerate its geological study and industrial development.

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Lebedko G.I. Prospects for accrual of hydrocarbon crude resources in the southern region of Russia

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As the upper (Meso-Cenozoic) part of the geological section with deposits of commercial oil and gas productivity is well developed (depletion of some productive horizons has exceeded 90 %), the approach to assessment of oil and gas possibilities needs to be optimized. Geological and economic analyses show that the first-priority projects should be related to the Paleozoic series of consolidated rocks (fractured reservoirs in reefogenic formations С1-2) on the southeast slope of the Voronezh anteclise. Southwards from the Donbass folded structures we recommend a comeback to the Khadumits (hard-to-extract reserves of the Maikop series and the Khadum and Kumsk suites) within the Indolo-Kuban and Terek-Caspian foredeeps. The prediction methodo-logy should be integral and provide for use of not only CDP-2D and KMPV (refraction correlation method), but also other seismic tools, including the analysis of potential fields. Prediction has to be focused not only on tracing the horizontal surfaces, but also on identification of activated sub-vertical zones of the destruction accompanied with flux of fluids (the heat-mass transport zones). Traditional technologies of seismic-geological data interpretation are noted not to result in unam-biguous identification of possible sub-vertical and inclined HC pools. In this connection we propo-se a technology based on the ration of velocities permitting to evaluate the dynamic (velocity-related) parameters of the section, which enable to identify compositely controlled traps. The proposed methods and technologies can be applied with minimum expenses, provided one shall use data of the deep wells drilled in still not licensed areas (their number in the region is about 10 thous.

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Andreyev V.M., Byakov A.A., Vesnina I.I., Podshuveit V.B., Khaliman L.A. New large closure on the Zhiguli arch

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Geological-geophysical data on the North-Western part of Zhiguli arch has been consolidated. South-Syzran anticline – top of the Zhigulev arch – was discovered in the area of Saratov reservoir with the use of Common Depth Point Seismic. Hydrocarbon accumulations are expected in the Devonian - Carbonian strata.

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METODS OF OIL AND GAS DEPOSITS PROSPECTING

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Vorobyev V.S., Chekanov I.V., Klinovaya Ya.S. The distribution model of terrigenous reservoirs and saline sand-gravelite deposits within the fields of the central part of the nepal arch

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The presence of both formation salts and the pore space of rocks being created by these salts are typical of the deposits of the Nepa arch of the Nepa-Botuobinsk anteclise of the Siberian Platform. Salinization’s spread in the area and in the section is extremely uneven. The presence of effective thicknesses in terrigenous stratum, and therefore their productivity, is determined mainly by secondary transformations of sediments. A major role in this process is played by attenuation and anhydrizing. The problem of forecasting zones of improved and saline reservoirs is the key issue for the main deposits in the region (Verkhnechonskoye, Chayandinskoye, Talakanskoye, Vakunai, Tympuchikanskoe, Ignyalinskoye and others). The core samples were selected and common and special studies were performed by 25 producing wells of the Verkhnechonskoye field (Rosneft), as well as the 13 exploratory wells of the Ignyalinskoye, Vakunayskoye and Tympuchi-kanskoye fields (Gazprom Neft). The Early Cambrian Usol is characterized by the sea basin shallowing. The data analysis of 3D seismic surveys (4500 km2 area) gives grounds for assuming the transferring of saline waters through the carbonate part of the section along the vertical decompressed zones. The use of the revealed analytical dependencies makes it possible to locate prospecting and exploration drilling wells as early as the processing and initial interpretation stage of 3D seismic data.

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OIL AND GAS RESERVOIRS

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Shaldybin M.V. Fenstral structures of riphean carbonate rocks of the Yurubcheno-Tokhomskaya zone

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The article studies the matters of the formation of open-cavity structures in the carbonate sediments of the Riphean of the Yurubcheno-Tokhomskaya oil and gas accumulation zone. The dolomite cavern porosity of the Riphean of the Siberian platform has a synsedimentary and early-diagenetic origin, and the caverns correspond to the sedimentological definition. The formed cavities cause a directed process of enveloping the walls of the fenstral caverns with euhedral dolomite crystals during its recrystallization. The Riphean fenestras of the Siberian platform have an isolated distribution pattern and are rarely interconnected. The horizons of the distribution of loferites and fenestral cavities can serve as stratigraphic traps and, in the case of a favorable development of fracturing in them (with intersection), HC should be accumulated.

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GEOPHYSIKAL INVESTIGATIONS

 

Borodkin V.N., Kurchikov A.R., Nedosekin A.S., Lukashov A.V., Smirnov O.A. 

Characteristic of geological nature of inversion circular structures in the arctic zone of west Siberia as a criterion of oil-and gas occurrence

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Inversion circular structures are represented here by local circular uplifts in the Neocomian section passing into depressions at the level of Jurassic horizons. Most of them are found in the Northern and Arctic regions of West Siberia, including in water areas of the Kara and Barents seas. There are several visions connecting this phenomenon with processes of deep outgassing of the Earth, great height of the column of oil-and-gas saturation, existence of destruction zones, abnormally high formation pressures (AHFP), avalanche-like sedimentation at the Jurassic - Early Neocomian frontier, etc. The character of seismic records in the zone of inversion circular structures, negative anomalies of Δg, considerable fracturing of rocks in the Jurassic - Neocomian section and existence of AHFP, etc. suggest their connection with zones of destruction and processes of vertical migration of fluids. Also existence of the inversion circular structures can be explained by inhomogeneity of formation pressure and its influence on velocity characteristics of local seismic waves. Despite the variety of opinions on geological nature of the inversion circular structures, their existence, on one hand, should be regarded as indication of AHFP, which is very important for well-drilling in offshore areas of Russia. On the other hand, in zones of their development the oil-and-gas saturation of a considerable interval of the section is observed as a rule, which can be considered as a positive criterion for prediction of oil and gas occurrence.

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HARD-TO-EXTRACT AND NON-TRADITIONAL HYDROCARBON SOURCES

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Ilyinsky A.A., Prishchepa O.M. New forms of organizational interaction for solution of problems of geological studying and development of nonconventional and hardly removable stocks

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The main trend in development of the World energy industry is as follows: continuous increase of production of HC crudes. In the process of extraction of the resources the possibilities of further growth of oil and gas production shift to remote and Arctic regions of the World and marine zones with still greater sea depths, which involves multiple leaps of relevant capital investments. Extensive exploration activity does not provide for adequate compensation of the extracted HC resources regarding active reserves with quality matching that of the exhausted ones. This negative tendency in the near future and in a long run may become a serious challenge for the energy and economic security of the country. Nonconventional sources and types of HC crudes represent an important part of the HC-in-place resource balance. Their contribution to the balance many times exceeds that of traditional resources known to constitute the basis for commercial production of HC. Federal government agencies respond to the need of studying and development of nonconventional resources and reserves of HC crudes by issuing strategic and programming documents determining the basis of state policy of Russia in the area of use of mineral raw materials and exploration-production licensing. According to the decision of the Ministry of Natural Resources and Ecology, “the coordination center for study and development of nonconventional types and sources of crude hydrocarbons” has been recently founded at JSC Rosgeologiya. Activity of the Center will provide integration of efforts of key relevant scientific institutes of Rosnedra and major Russian production and service companies for studying and development of nonconventional resources and reserves of hydrocarbon crudes. Development of new forms of interaction of the above organizations (including those based on technological platforms) for solution of the problems of geological study and development of nonconventional and hard-to-extract reserves will help to combine common efforts of the state, companies – license-holders and scientific community for achieving stabilization of the all-Russian production of HC crudes.

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Khisamov R.S., Azimov N.A., Khannanov R.G., Podavalov V.B., Bazarevskaya V.G., Salimov O.V. Multizone acid hydraulic fracturing of domanik deposits in the bavly oil field

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Contribution of oil-saturated shales to the World oil production rapidly grows. In a short period of time North America could overcome the tendency oil production decline owing to development of only two shale oil fields - the Bakken and Eagle Ford. Deterioration of the structure of reserves and acute problem of their renewal does make the development of similar deposits in Tatarstan extremely urgent. Analogs of the shale formations of the North American platform in Russia are as follows: the Bazhenov shales in West Siberia, Domanik deposits in the Volga-Ural and Timan-Pechora oil-and-gas provinces and Khadum suite in the Pre-Caucasus. Technologies of production of nonconventional HC are dictated not only by chemical-physical properties of the HC and geological and physical characteristics of the reservoir rocks, but also (and quite substantially) by their lithological properties. Each “shale” field of “tight” oil is known to require its own pro-duction technology, however in general all the technologies follow the scheme as follows: drilling wells terminated by a horizontal hole with e subsequent multistage hydraulic fracturing of the productive layer. In the first quarter of 2015 at the Novo-Bavlinsk part of the Bavly oil field a horizontal well (Well 2917ã) was drilled with horizontal borehole in the Domanik layer of the Dankov-Lebedyansk (DDL) horizon. The horizontal hole 264,5 m long was designed and drilled based on geophysical and well logging data acquired in the pilot hole and results of special analyses of oriented core. To attain higher efficiency of the layer hydraulic fracturing, i.e. obtain a higher flow rate, at these particular geological conditions it is necessary to perform various versions of NBZT (near-borehole zone treatment) and MAHF with use of acid solutions at different operating conditions (varying pumping-in pressure, pumped volumes, concentrations, flow rates, etc.).