«OIL AND GAS GEOLOGY» № 4/2017

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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

 

HYDROCARBON RESOURCES AND RESERVES

 

M.I. Epov, J.J. Shemin. Quantative forecast of oil-and-gas-bearing capacity of regional Jurassic sedimentary reservoirs in the north of Western Siberia and in the Kara sea

 

In this article, the results of quantitative forecast of oil-and-gas-bearing capacity of the Oxfordian, Bathonian, Aalenian-Bajocian,Toarcian, Pliensbachian, and Hettangian-Sinemurian regional Jurassic sedimentary reservoirs in the North of West Siberia and in the Kara Sea are reported for the first time. It is based on the previously developed structural models and reconstructed formation conditions of each of these reservoirs and for their constituents — permeable complexes and seal rocks. Tectonic, lithofacial and geochemical criteria of oil-and-gas potential estimation of these reservoirs are explicated. The technique and results of a quantitative oil-and-gas potential evaluation of regional reservoirs are discussed, the charts of oil-and-gas potential, oil potential and gas potential of each reservoir are given. In these charts, areas of various prospectivity levels are shown and major top-priority objects of oil-andgas prospecting works are marked. The structure of hydrocarbon resources is shown including distribution of initial total hydrocarbon resources by phase composition, categorization of resources and reserves, and by regional reservoirs and petroleum bearing areas.

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A.A. Deshin, P.I. Safronov, L.M. Burshtein Evaluation of realization time of the main phase of oil generation in the middle – upper Jurassic deposits of the north of Western Siberia

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For the Upper – Middle Jurassic oil and gas generative formations in the North of the West Siberian oil and gas basin the extent and time of realization of the main phase of oil and gas generation have been reconstructed using the historic-genetic (basin) approach. One-dimensional numerical modeling was performed for sections of 8 wells located in the territory of the Yamalskaya, Gydanskaya and Yenisei-Khatangskaya (its western parts only) oil and gas bearing areas. Results of the modeling show that all considered oil and gas generative formations have entered the main zone of oil generation in the studied territory. The oil and gas generative deposits in wells located in the most deeply buried parts of the region, as in the S. Noskovskaya, Trekhbugornaya, Shtormovaya and Harasaveyskaya areas, have left the main zone of oil generation and passed into the deep zone of gas generation. Deposits of the Malyshev and Bazhenov horizons in the S. Tambey, Utrenniaya, Geofizicheskaya, Peliatkinskaya and Totaiakhinskaya areas are located in the main zone of oil generation. Generation of largest volumes of both liquid and gaseous hydrocarbons (HC) is noted in zones of elevated heat flux, higher quality of organic matter and considerable thicknesses of oil and gas generative formations. Average density of the HC generation in the Malyshev horizon was 1.7 million tons/km2 and 500 million m3/km2 for fluid and gaseous HC, respectively. Average density of the HC generation in the Bazhenov horizon was 750 thous. tons/km and 500 million m3/km2 for fluid and gaseous HC, respectively.

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A.P. Afanasenkov, N.D. Surova, L.V. Levchuk, A.A. Kiselev, E.A. Kopilevich. Capacitive characteristics of reservoirs of Jurassic – cretaceous deposits of the gidan and western part of the Yenisei-Khatanga oil and gas bearing areas

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In the article the capacitive characteristics of the Jurassic and Cretaceous oil and gas prospective reservoirs in the Gydanskaya oil and gas bearing area and western part of the Yenisei-Khatangskaya oil and gas bearing area are considered. Those characteristics were gained with the use of innovative technology based on an integral spectrum-velocity forecast with results presented in the form of maps of predicted effective thicknesses and specific capacity. Analysis of predicted values of reservoir capacity parameters has permitted to reveal regularities in their distribution and to identify zones of elevated values of reservoir capacity parameters for each considered reservoir. The results of analysis of distribution of the predicted values of reservoir capacity parameters obtained for four Cretaceous reservoirs and three Jurassic reservoirs were compared, which permitted to identify cases of overlapping of the zones of elevated values of capacity parameters. Comparison zones of distribution of elevated values of reservoir storage parameter with the new tectonic zoning of the territory is also presented. For more complete consideration of the reservoir capacity characteristic we present additional data on stratigraphy of oil and gas saturated intervals for the oil and gas fields already discovered in the considered part of the Yenisei-Khatanga regional deep. General characteristic of the seven considered reservoirs and variations of the values of reservoir capacity parameters in the section of Jurassic and Cretaceous deposits are shown. On the basis of the obtained prediction maps and results of their comparison, the conclusions are made on existence of prospective zones from the point of view of the capacitive characteristic, and the area of the zones is approximately assessed. Prediction maps of storage parameters were used for updating the assessment of resource potential of the western part of the Yenisei-Khatanga regional deep.

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O.A. Bogdanov, V.N. Koloskov, A.O. Shuvayev, K.V. Musikhin, S.B. Istomin, M.A. Bobrova,
P.S. Maglevannaya. Analysis of evolution of the Bolshehetsk depression hydrocarbon systems based on the use of basin modeling method

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In the article the results of using the technology of 3D basin modeling to reconstruct evolution of hydrocarbon systems of the Bolshekhetsk depression located in the northeastern part of the West Siberian plain known as a highly prospective land area of the Tazovsk oil and gas bearing region of the Pur-Tazovsk oil and gas bearing area are discussed. The area has been relatively well studied by seismic, however the HC potential of the Achimov and Jurassic deposits remained questionable for a long time due to considerable depths of their occurrence over the most part of the area. Moreover, the exploration is complicated by presence of zones of abnormally high formation pressure where the drop of elastic wave velocities is observed caused by deconsolidation of the Jurassic and Cretaceous rocks. At least ten such zones are identified in the Bolshekhetsk depression. Basin modeling is known as a method of geological studies permitting to integrate a wide spectrum of geological, geophysical and geochemical information into one model. Results of such modeling permit to trace the main stages in the basin formation history and development of elements of HC-systems, as well as to predict and localize zones of oil and gas accumulation, which will significantly reduce geological risks, and therefore, diminish the costs of exploration operations.

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METHODOLOGY OF PROSPECTING AND EXPLORATION OF OIL AND GAS FIELDS

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D.N. Krylov, M.D. Krylova. Interpolation technology in case of complex mapping solutions

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Some key geological data could be obtained only on the basis of well information. Technology of interpolation to find optimal well mapping solution is presented in the paper. In case of complex anomaly zone geometry and sparse drilling the mapping could be complex and have multiple different solutions or even not correct. Mapping process could be optimized by the proper choice of interpolation algorithm and data filtration. Technology employs algorithms of linear and optimized statistical interpolation in the “live” window (smart averaging). Mapping error is quantitatively assessed by validation technique, i.e. by removing wells from computing process one by one and calculating each time the interpolated datum error at the removed well location. Then using trial and error method we can test interpolation and filtration options and compare interpolation errors for each set of interpolation parameters. After the error distribution analysis the best interpolation parameters are determined and used for mapping.

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M.V. Sharashkina, N.N. Polskaya, A.Yu. Samoylenko. Comparative compositional analysis of Sarmat field condensates by simulated distillation method

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The article presents the results of laboratory study of fractional compositions of stable condensates from the Tithonian stage sampled in Wells Sarmatsk-1 and Sarmatsk-2. The study was performed by the simulated distillation method using a gas-liquid chromatograph. Based on the results of the study of the samples we have obtained the curves of true boiling points (TBP) and hydrocarbon fractions concentration distribution and further used the curves to perform comparative evaluation of quantitative and qualitative compositions of the condensates. The results of chromatographic distillation show that the condensates become lighter vertically downwards along the field section (from Tithonian Layer I to Layer II and Layer III), which is proved by respective change in their component composition. Based on analysis of the presented data it was concluded that the reservoirs of Layer I contain an independent HC accumulation. The condensates obtained by testing from Layers II and III are identical in terms of their ultimate content and fraction distribution pattern, which may indicate their belonging to a common gas-condensate system. As much as the limits of the article permit, the possibility of using the simulated distillation as an express method for evaluation of the correlation of productive layers is shown.

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GEOCHEMICAL SURVEYS

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G.Ch. Borukaev. Organic geochemistry of Paleosoic-Triassic sediments of Wrangel island

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The objects of the study are dislocated and metamorphosed carbonate, carbonate-terrigenous, terrigenous and less often evaporite rocks of the shelf type. Organic matter (OM) of these sedimentary rocks was studied by methods of pyrolysis, coal petrography, gas-liquid chromatography, chromatography-mass spectrometry and isotopic analysis of carbon. Just a few diagnostic indices are found to have preserved their genetic at final stages of apocatagenesis. Generative potential of OM is exhausted, reservoir properties of the deposits are lost and the dynamic fluid systems of the geological past are unpromising. Aquatic nature of OM of the II and II/III types is supposed is suggested. At the present stage the average concentration of organic carbon is about 1 % and bitumen — 0.001–0.002 % in the isolated horizons. In some samples, these indicators reach 2–3.6 % and 0.038 %. The carried out reconstruction of OM the initial and located in the oil window area contents, showed that in the past the oil deposits had high quality. Their favorable combination in a section with series of sandstones and organogenic limestones contributed to the formation of fluid dynamic systems located at stratigraphic levels that are close to those found in the oil and gas basin of the North Slope of Alaska. Now their generation and accumulation potentials on the island are almost exhausted, and they have no prospects. Under conditions of the North Chukotka sedimentary basin these systems could function and release some part of the generated HC to upper horizons of the cover. The materials obtained on Wrangel Island allow us to positively assess the prospects of the oil and gas potential of the largest basin on the Chukotka shelf.

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O.S. Kotik, I.S. Kotik, T.G. Kargieva Permian deposits of the South-East of Korotaikhinskaya depression: coal petrography, geochemistry and oil and gas generation potential

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The article presents the results of geochemical and coal petrological research of Permian deposits in the southeastern part of Korotaikhinskaya depression. The lekvorkutskaya (P1lv) and sylovskaya (P2sl) suites are characterized by a similar maceral compositi on with the  redominance of vitrinite group and larger content of liptinite (20 %) in Upper Permian rocks. The Rock‑Eval pyrolysis analyses show that the organic matter of P1lv deposits has type III–IV kerogen with a low generati on potential (HI < 50 mg HC/g TOC), and the organic matter of P2sl deposits has type II–III kerogen with a good hydrocarbon potential (HI — 161–357 mg HC/g TOC). Rо data show the catagenetic transformati on of organic matter of P1lv deposits according to the gradati on MK2 –MK3 (R — 0.75–1 %) in the west and gradation MK5(R  — 1.75–1.95 %) in the east of the studied area with local abnormally high values of maturity to gradation AK (R  > 2 %). The P2sl deposit reached the main oil generation zone, and catagenetic transformati on of organic matter has gradation MK2–MK3 (R  — 0.8–0.85 %). The distributi on of n‑alkanes and isoprenoids in the hydrocarbon fraction of bitumen shows a significant proportion of humic organic matter with the contributi on of sapropel compounds increasing in Lower Permian clay rocks.

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GEOPHYSICAL SURVEYS

 

T.R. Akhmedov. Effective thickness and miocene deposits producibility on Absheron oilfields of Hovsan block, Azerbaijan, using 3D seismic survey

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The article is devoted to oil-and-gas potential of Lower Pliocene deposits, more exactly to the effective thickness, which is also the main hydrocarbon-bearing formation in Azerbaijan, particularly in the Absheron peninsula, as well as Miocene deposits considering the 3D seismic data. In the article it is pointed out that now geologists and geophysicists are facing challenges related to study of smallsize traps of the anticline, non-anticline and other nonstandard types, such as traps of the "hanging" type common in the Absheron peninsula and adjacent territories of Azerbaijan. It is emphasized that with improvement of the seismic exploration technology and methodology the geophysicists become equipped with new tools for detailed and confident studying geological section. The study area is situated within confines of the most ancient oil-and-gas production region of the World, and despite the fact that this field has been developing for more than 60 years, the area does not suffer any loss of interest, because the lower series of the Pliocene section, as well as the Miocene deposits are highly prospective and a special role in their exploration belongs to seismic surveys. The results of dynamic processing and interpretation of the 3D seismic data are presented in the article, as well as prediction maps based on these results. On the obtained maps and sections identified anomalies of the seismic record of the "accumulation" type are shown. Several hydrocarbon traps have been identified in the bottom part of the effective thickness and in Miocene deposits as the result of dynamic analysis of 3D seismic survey data.