«OIL AND GAS GEOLOGY» № 1/2018
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
Editorial office address: 36 shosse Entuziastov, 105118, Moscow, Russia
Viktor Petersilie, deputy editor-in-chief
FORMATION AND LOCATION OF OIL AND GAS POOLS
A.P. Afanasenkov, A.N. Obukhov, A.A. Chikishev, V.A. Shaydakov, A.V. Bordyug, S.L. Kalamkarov. Tectonic setting of the northern surroundings of the Siberian platform based on the integrated study of geological and geophysical data
Integrated analysis of geological and geophysical results of the investi gati ons carried out recently in the northern neighbourhood of the Siberian Platf orm (Yenisei‑Khatanga regional trough, Anabar‑Khatanga saddle, and Lena‑Anabar trough) together with the previous studies, made it possible to make a more comprehensive and substanti ated update of tectonic framework of the study area. The improved composite geological section of the north‑western part of North‑Asian Carton is presented with delineati on of structural levels, strati graphic sequences, and correlation of main refl ecting horizons. Scale of tectonic events, deposodes and breaks is created, where five main structural levels are identified (pre‑Riphean metamorphic basement, Riphean‑Palaeozoic transiti on basement (of ancient platform); Upper Permian ‑ Lower Triassic rift basement; Middle Triassic ‑ Upper Cretaceous platform basement (of young platform); Paleogene‑Quaternary (Alpine) for the Gydan‑Yenisei‑Khatanga, Anabar‑Khatanga, Lena‑Anabar zones and Khatanga‑Lena delta. According to CDP seismic data, the results of magnetic and gravity surveys, Magnetotelluric Sounding, and Deep Seismic Sounding, the rift model of the Yenisei‑Khatanga regional trough evolution is substantiated. Structural and tectonic elements within the Palaeozoic (pre‑Middle Triassic) and post‑rift (post‑Lower Triassic) sequences are identified and/or updated. Tracking of the limits of the promising Neocomian clinoform complex was for the first time carried out within the Yenisei‑Khatanga regional trough eastward to the Anabar‑Khatanga saddle. The proposals about licensing and on the program of the further exploration are presented.
A.N. Dmitrievsky, N.A. Eremin, N.A. Shabalin. The seismic behaviour of the sedimentary cover section in the arctic zone of the Siberian platform
In the article the seismic behaviour of sedimentary cover of the Arctic zone of the Siberian platform is discussed. Southern and central parts of the the Siberian platform are characterized by a high density of oil and gas resources. The major petroleum province of the Siberian Platform is the Lena-Tunguska petroleum province. Source rocks the Lena-Tunguska petroleum province are associated with the Riphean, Vendian, Lower-Middle Cambrian deposits, in which the major oil and gas fields are discovered. In its modern boundaries, the Siberian platform neighbours with the Yenisei-Khatanga regional trough in the north and north-west; the eastern part of the trough joins with the Anabar-Lena trough, framing the north-eastern part of the Siberian platform. Analysis of the available geological and geophysical materials shows a fairly high potential of the Anabar-Lena and Yenisei-Khatanga troughs for discovery of large hydrocarbon fields. The basic understanding of the geological and tectonic architecture and oil and gas occurrence in the northern part of the Siberian Platform and adjacent Arctic shelf are based today on CDP seismic data, tied to the existing deep stratigraphic and prospecting wells. Understanding of deep structure and petroleum potential of certain areas, allocation of target promising oil and gas bearing horizons can change dramatically according to advancement of seismic CDP technique and software for seismic data processing and interpretation seismic data is improved.
V.I. Isaev, G.A. Lobova, A.K. Mazurov, V.I. Starostenko, A.N. Fomin. Zoning of mega-depressions by shale oil genegation density of Togur and Bazhenov source suites in the southeast of Western Siberia
Search for shale oil, referred to hard‑to‑recover reserves, is a recent trend for Western Siberia, where Upper Jurassic Bazhenov and Lower Jurassic Togur deposits are widespread. Developed infrastructure of the Southeast defines these lands priority for zoning of the prime searching areas. The arti cle deals with input geological‑geophysical data, research methods and fi rst zoning results of Togur and Bazhenov suites within Nyurol and Ust‑Tyma mega‑depressions by shale oil resource density. Zoning technique is based on the paleo-temperature modeling allowing as to reconstruct the thermal history of source deposits, select and map oil source kitchens using geothermal criterion. The method is based on numerical soluti on of heat equati on of a horizontally layered solid with moving upper boundary. The mathemati cal model includes climati c secular temperature variati on on the earth’s surface, as a boundary conditi on, and paleo‑temperatures from the vitrinite reflectivity definitions, as “observed”. The method does not require a priori data on the origin and quanti ty of the deep heat flow. Esti mati on of the shale oil resource density (generati on density) is determined by the integrated indicator directly dependent on time of fi nding the source suite in the main oil generati on zone and its geo‑temperatures. Potential shale oil areas of Togur suite were identified. This is the juncti on zone of Kulan‑Igay depression, Igolsko‑Talovoye domal upwarping and North‑Mezhov mega‑homocline, zone of Festival bar and northern bead of Tamrad depression, eastern part of the northern cut within the Nyurol mega‑depression. Within the Ust‑Tyma mega‑depression the junction zone of the central and southwestern parts of mega‑depression with the North‑Parabel mega‑homocline are predicted to be rather prospective. Potential shale oil areas of Bazhenov suite were identified. It is a sub‑lati tude zone including the southern parts of Kulan‑Igay depression and the Festi valbar, Tamrad depression and positive structures framing the eastern part of Nyurol mega‑depression. Within the Ust‑Tyma mega‑depression there is the triple junction zone of the Sampat meso‑deflection, Parabel mega‑outshot, Northern‑Parabel mega‑homocline and the triple junction zone of the Negotsky meso‑deflection, Alexandrov dome, Karaminskaya meso‑saddle. The consistency of zoning is justified by oil showings and oil flows from intervals of source rocks in explorati on and parametric wells.
OIL AND GAS RESERVOIRS
E.N. Cherepanov. New model of formation of the Early Cambrian carbonate petroleum reservoirs in the Nepsko-Botuobinskaya anteclise region
This paper describes a new model of petroleum reservoirs formati on in the osinskiy carbonate horizon of the Early Cambrian usolskaya suite in the Nepsko‑Botuobinskaya Anteclise region. This new conceptual model involves the thrust tectonics processes in the overlying carbonate‑salt sequences, influencing the osinskiy carbonates. These processes are related to one of the base detachment surfaces in the carbonate‑salt formations, where the carbonate rocks of the osinskiy horizon belong to the intervals, which experienced intensive thrust deformations along this major sub‑horizontal detachment surface. In the result, the osinskiy carbonate rocks were subject to very significant tectonic deformations by the tangential compressional forces originating from the Baikal rift zone. These deformations included numerous faults and fracture zones, as well as sub‑horizontal slicing of the carbonate rocks into series of small tectonic sheets, layers and blocks, which in some cases experienced lateral sliding and imbrication, compressions and other small‑scale tectonic deformations. Later, in the fault zones, fracture corridors, or along major bedding planes and thrust detachment surfaces, deformed carbonate rocks of the osinskiy horizon were subject to extensive dissolution, leaching, and cavern formati on, up to large caves of several meters in size, which were filled by carbonate clastic material of different sizes. These processes were result of the circulati on and movement of aggressive, high‑temperature hydrothermal fluids along deformati on zones. They also included the reacti ons of abiogenic thermochemical sulfate reduction, which were represented by the processes of intensive hypogene (deep, burial) karst of the osinskiy carbonates. All these process then resulted in the formati on of carbonate reservoirs with anomalously high porositi es and permeabiliti es, and oft en they are characterised by huge producti on rates of hydrocarbons. Further studies and more complete understanding of the complex tectonic and post-sedimentation processes in the carbonate rocks, and therefore, better understanding of the internal architecture of this type of hydrocarbon fields will allow for better prediction of high porosity and high permeability zones within such fields. This will also allow for higher success rates during exploration and production drilling in carbonate rocks of Cambrian age in the region, and will also help developing technical strategies for exploration of similar types of hydrocarbon fields on the Siberian Platform.
G.А. Petrov. Stylolite and suture seams in Upper Carbon and Lower Permian carbonate rocks
The paper presents the materials that define genesis of stylolite and suture seams common for Palaeozoic carbonate rocks. Their origin remained an enigma and led many researchers to suggest various hypotheses of their formation. In order to determine the seams genesis, the author used X‑ray Diff racti on Analysis to study a fiber‑like material sandwiched between the seam walls. As a result of the analyses, it was found that this material is a magnesium silicate hydrate — sepiolite — member of clay mineral group. Thin fiber‑like aggregates — “echelons” in the form of vertically sinuous seams develop resulting from its crystallizati on in carbonate rock. High concentration of clay mineral (sepiolite) in carbonate rock provides formation of stylolite seams, while the low one predetermines formati on of suture seams. Stylolite and suture seams within which sepiolite was aff ected by supergene processes and eluviation (of transformed clay material) occurred may serve as migration paths and reservoirs for oil, gas, and water. Presence of stylolite seams in carbonate rocks can be exploration criterion for identi fication of valuable clay mineral accumulations, magnesium silicate hydrate — sepiolite.
T.A. Kireeva. Hydrochemical features of basement in the context of oil bearing capacity
Vertical migration of petroleum hydrocarbons from basement to sedimentary cover as a part of endogenous fluid is substantiated. The conditions for separation of deep fluid into gas, oil and water components, where the latter is represented by low-mineralized HCO –Na waters and dilute Cl–Na brines, are considered. The possibility of early hydrocarbon migration as a part of carbonate HCO –Na solution followed by Cl–Na solution movement to the basement surface and basal part of the sedimentary cover is discussed. It is proposed to consider the zones of hydrochemical inversions in the sedimentary cover to be a prospecting guide for presence of hydrocarbon accumulations in the deep parts of sedimentary cover and basement, while brines supply from the basement to be a sign of oil lacking.
HC HARD-TO-RECOVER RESERVES AND UNCONVENTIONAL SOURCES
M.B. Skvortsov, V.D. Nemova, I.V. Panchenko, A.M. Kirsanov. Criteria of oil bearing capacity of the Bazhenov formations
The paper discusses the criteria of oil bearing capacity of the Bazhenov formations. In recent years, a vast amount of production and core data was collected for the Bazhenov formation, which allowed analysing relationships of impermeable seal thickness and pressure and temperature conditions of the formation with its oil bearing capacity. Analysis of impermeable seal thicknesses does not make it possible to predict the Bazhenov oil bearing capacity, while the high present-day formation temperature and pressure are the reliable indicator of oil bearing capacity of this sequence. It is shown that bitumoid group analysis differs in dry and productive wells. Therefore, this indicator can be counted in the list of oil bearing capacity criteria for the Bazhenov formation. On the basis of these criteria, the areas prospective for testing are identified in the Yamalo-Nenets Autonomous Okrug.
A.F. Safronov, A.I. Sivtsev. History of the Olenek natural bitumen field formation
The history of formation of the Olenek natural bitumen deposit from the standpoint of the Olenek syneclise existence is considered in the paper. According to previous studies, it is supposed that the Olenek syneclise was formed in the Late Precambrian – Early Cretaceous time within the Laptev plate, and it is not unlike the Viliuisky syneclise in terms of development history and architecture of the Upper Precambrian – Lower Cretaceous section. Based on the retrospective model of the geological development of the Laptev Sea shelf (Laptevsky Plate) being a part of the Siberian Platform, the dynamics of catagenetic transformations of rocks and dispersed organic matter of its Permian part of the Upper Precambrian – Lower Mesozoic section is discussed. The role of generation potential of the Permian sequences in the southern part of the Olenek syneclise and the northern part of the Predverkhoyansky trough in formation of the Olenek natural bitumen deposit is quantitatively estimated. The results showed that the total probable generation potential of the Permian formations of the segment selected within the eastern part of the southern shoulder of the Olenek syneclise could make 32.932 billion tons. The conclusion is drawn that, taking into account the migration losses, the estimated potential of the Permian sequences in the neighbouring part of the Laptev Sea shelf (in the modern structural plan) is sufficient for formation of the Olenek natural bitumen field.