Burlin, Y. K.

Sokolov, B. A.

English

Electronic Publication Information Center

Polarforschung 69, 149 -154, 1999 (erschienen 2001)Russian Arctic Sedimentary Megabasin andIts Reflection in Oil and Gas Properties of Its BorderlandsBy Yuri K. Burlin' and Boris A. Sokolov'THEME 9: Hydraearbon Potential of the Eurasian Margins:Geological and Teetonie FaetorsSummary: The Russian Arctic shelf and continental slope belongs to thegiant Arctic superbasin. This superbasin can be divided into an eastern and awestern segment with an apparently different structure and history. TheNorvegian - Barents platform is the main element of the western segment.Several large sedimentary basins filled with kilometres of Paleozoic andMesozoic strata had formed here. Seismic reflection data and the geology ofneighbouring areas show that the platform apparently existed from the earliestPaleozoic. A significant stage in the development of the western segment wasthe Permian to Triassic, when intensive subsidence and corresponding accu-mulation of sediments took place. It was the principal period for organic mate-rial transformation and hydrocarbon generation. The source rocks subsidedinto the gas window very fast. Gas production in the deep zones of the basinsresulted in the formation of supergiant gas-condensate fields in the Barentsand Karsa seas. Evidence for the existence of oil fields at earlier times in theperiphery of the basins has been discovered recently.The eastern segment is separated from its western counterpart by the Lomo-nosov ridge. The situation is different in the eastern segment, which has acomplex structure consisting of blocks and linear zones. Most blocks have aPrecambrian basement that has been reactivated in the Mesozoic. Theseblocks form a tectonic collage of massifs divided by mobile linear zones.Sedirnentary basin development was controlled by processes of reconstructionof the continental crust, the Mesozoie tectogenesis playing a significant role.Analyses of seismic data show six main successive units in the northern partof the Chukchi Sea, with a total thickness exceeding 10 km. The lowermostunit F apparently has an Upper Paleozoic - Triassie age. The next complex Ehas the greatest thickness, exceeding 3-4 km. It consists of terrigenous mate-rial. After a regression the lacustrine and shelly marine strata (unit D) weredeposited. The complexes E and D apparently have a Jurassie - Cretaceousage. The units C and B represent alluvial or paralic deposits and have a Paleo-gene - Lower Miocene age. The unit A shows the character of strata depositedin modern marine conditions, In the southern part of the Chukchi Sea, thethree lower complexes are included in the basement or transitional zone.The Russian Artic basins have a great hydrocarbon resource potential.THE RUSSIAN SHELF AND NEIGBOURING AREASINTRODUCTIONThe western and eastern part of the Russian shelf belongs tothe Aretie superbasin. The history and strueture of these twosegments divided by the Lomonosov Ridge are different. Thewestern segment is separated fram the eastern segment by thesubsea Lomonosov Ridge. The eastern segment eonsists of theLomonosov and Mendeleev ridges separated by the Makarovand Tollya depressions (Fig. 1)., Geologieal Department, Moseow Lomonosov University, Vorobjovy Gory, Moseow119899, Russia. <oil@geol.msu.ru>Manuseript reeeived 02 February 1999, aeeepted 14 May 2001The western segment eonsists of the Norvegian-Barents plat-form, and the Nansen and Amundsen deepwater depressionswhich are separated by the Gakkel Ridge rift. The platformunderwent rifting proeesses. The signifieant rifting, fast sub-sidenee and eorresponding aeeumulation of sediments tookplaee at the end of Paleozoie and beginning of Mesozoie eras,so that there are several large basins filled with kilometres ofPaleozoic and Mesozoic sediments. These events had impor-tant eonsequenees for hydroearbon generation, distribution,and aeeumulations. The Mesozoie strata have been drilled andstudied, and giant gas-eondensate fields were diseovered. Theupper Paleozoie part of the sueeession is supposedly oilbearing, while the upper part of the Mesozoie strata is gasbearing.The eastern segment including the Asian-Alaskan seetor wasloeated on a eontinental crust first. Then destruction by rigidmass processes played a significant role. Now the eastern partof the Russian Arctie shelf is a collage of rigid blocks dividedby folded Mesozoic zones. In the sedimentary basins, Meso-zoie and Cenozoic sediments attain the greatest thiekness ofthe sueeession. Analogs to the oil bearing structures of Alaskaare present here. Different development histories in thewestern and eastern segments are the reason why some areasare gas bearing and others oil bearing.The Western SegmentA marine terrigenous-carbonate Paleozoic eomplex coverswide areas on the Barents shelf. Lacustrine and alluvial depo-sits are found along the shelf periphery in Svalbard (Spits-bergen) in the northwest and Peehora Sea in the south.Paleozoie rocks on the shelf were deposited as platform facies,which was followed by Late Paleozoic - Triassie rifting. I.Gramberg noted that the Permian-Triassie rifting manifestedthe reconstruetion of the Earth's Crust between the Paleozoicand Mesozoic eras (GRAMBERG 1997). Rifting is suggested bymagnetic anomalies identified in the meridional zone of theBarents Sea (FreHLER et al. 1997). Simultaneously folding andorogenesis was initiated in the Urals and West Siberianregions. The denudation of associated rising mountains inthese zones provided abundant quantities of terrigenous mate-rial. Streams from the new uplifts flowed westward andnorthward filling the South and North Barents depressions andKarsa Sea depression in Pennian and Triassie time. This was asignificant stage in the development of the basins. Thethickness of Permian and Triassie deposits in the Barents Seais as much as 9-10 km.One significant event was the forming of the Novaya Zemlya1491000 1200 1400V60J DJIDTaimyr Siberian 11 SIPechoraBlock Platform PlatformI-~I Mesozoic 1=---=1 Oceanic 1\\\1 Ritt Fig. 1: Teetonic sketch of theBelt Depression Fault Arctic megabasinarc (now archipelago) at the end of the Triassic. As MARTlRO-SYAN et al. (1998) noted, the Late Paleozoic - Early Mesozoicuplift of the Urals and the Novaya Zemlya orogen changed theregional picture dramatically. The influx of terrigenous mate-rial into the Barents depressions was stopped by this barrier,but material continued to flow into the Kara Sea depression.Because of strong subsidence and sediment accumulation andorganic transformation there was aperiod of significant petro-leum hydrocarbon generation at depths corresponding to the"oil window", Following this the source rocks subsided andthe maturation level increased into the gas window and gasgeneration dominated at these deeper levels.Gas production in deep zones of the basins resulted in the for-mation of supergiant gas-condensate fields in central parts ofthe basins like Shtokmanskoe and others in the Barents Sea,Leningradskoe and Rusanovskoe in the Kara Sea (Fig. 2). Oilon the other hand migrated to the basin peripheries to formdeposits in the Pechora Sea and Timan- Pechora depressiononshore. Evidence of previous oil bearing strata are found onSvalbard, Franz-Joseph Islands and Novaya Zemlya wherenumerous places with petroleum saturated rocks are known(KLUBOV 1997).150The Eastern SegmentThe situation is different in the eastern polar segment, whichhas a complex structure consisting of blocks and linear zones(GRAMBERG et al. 1997). These blocks are predominantly rigidmassifs of different age and structure surrounded by fold belts.The Chukchi-Eskimo massif is the oldest and most blockshave a Precambrian basement that has been reactivated in theMesozoic. Some of them had been rifted away from the ance-stral Hyperborean platform or from the North American cratonat different times. These blocks generally moved from east towest. They had formed a tectonic collage of massifs dividedby mobile linear zones filled with Upper Mesozoic and Ceno-zoic deposits.The block embraced by Taimyr and the southern part of Sever-naya Zemlya archipelago played an important role as atectonic boundary between the western and eastern parts of theRussian Arctic. The Precambrian basement of the NorthTaimyr zone began to rise and Paleozoic strata overlying rhebasement on the Severnaya Zemlya archipelago were weaklydeformed. It may have been the margin of the Barents plat-form which was later destructed. From the end of Devoniantimes on, the North Taimyr block stood high above largedepressions on the east and west.The eastern part of the Russian sector is less weIl studied thanthe western part. During the last 60 Ma, rifting was apparentlyan important process with spreading axes forming the AlfaRidge, rifts near the New Siberian Islands and Vrangel Island,and the Gakkel Ridge.The Gakkel rift zone pinches out southward. Apparent contin-uations of this zone are two branches on the Laptev Sea shelf:the Lena-Taimyr in the west and Oloy in the southeast. Purespreading dominates the Lena-Taimyr branch, while subhori-zontal tension and displacement dominated in the Oloy branch(PrsKAREv et al. 1997).Sedimentary basin development was controlled by processesof reconstruction of the deep continental crust. The Amerasianbasin opened in Jurassic-Cretaceous time (150-110 Ma). TheRussian part of the Amerasian basin is subdivided into foursubbasins, Laptev Sea subbasin, East Siberian Sea subbasinand North- and South-Chukchi Sea subbasins (Fig. 2). Thebasement in the southwestern part of the Laptev Sea is a conti-nuation of the Siberian platform. The basement under theeastern part of Laptev Sea, and basins east of it, is hetero-geneous and was re-activated during the Mesozoic. Sedimentfills in these basins vary in age. The majority of basinsequences start with Devonian strata which crop out along thesouthern periphery of the Amerasian basin, in northern Alaskaand Chukotka. Devonian and younger strata are more ubiqui-tous than older deposits (THURSTON & THEISS 1987). Terrige-nous-carbonate rocks of the Upper Devonian, Carboniferousand Permian seem to correlate with the Lower Ellesmerian inAlaska. Upper Permian and Lower Triassie strata are generallyterrigenous in composition and are about 3 km or more thick.The clastic material was transported from the north.The intensive subsidence took place all over the Arctic duringthe Mesozoic. Teetonic reconstruction resulted in chan gingterrigenous source areas during the Cretaceous. The bulk ofMesozoic strata are marine and near shore facies of UpperTriassic, Jurassie and Cretaceous ages. Fluvio-deltaic forma-tions are recognized and are the reservoirs in Prudoe Bay oilfield of Alaska. Volcanic activities influenced the depositionand character of sedimentary rocks in the Cretaceous andPaleogene.SEISMIC FACIES UNITSFigure 3 shows a proposed correlation between sequences ofNorth Alaska and the North Chukchi basin in the Chukchi Sea.There are six units in the North Chukchi basin with a totalthickness exceeding 10 km (Fig. 4). The greatest thicknessesare found in the northern part of the Chukchi Sea in the Creta-ceous and Jurassie (units Fand E). Apparently they consist ofpredominantly terrigenous material, but they may also includecarbonate and volcanic rocks. These deposits may be corre-lated with the upper Ellesmerian sequence of Alaska.The Vrangel Island block was elevated at this time, and Juras-sie and Cretaceous strata pinch out toward the island. After aregression the lacustrine and shelly marine strata were depo-sited over a wide area representing marginal marine or non-marine facies. These strata are in unit D, where low-amplitudeparallel reflectors are typical.~1Wz 0 3 r;:a't (ll]s ~'51C47[g8[§]9 f%:lfOIQ11 rn12Fig. 2: Big sedimentary basins on Russian Arctic shelf. I: Taimyr block, 2: Norvegian-Barents platform, 3: Pechora platform, 4: Mesozoic foldingzone, 5: Activated platform, 6: Early Kimmerian tectogenesis zones, 7: Sedimcntary basins, 8: Big highs, 9: Riftgenesis zones, 10: Continental slope,11: Deepwater oceanic depressions, 12a: oil and 12b: gas fields. Basins: Barents Sea I: North Depression, 2: South Depression), 3: Kara Sea, 4: NorthKara Sea, 5: Laptev Sea, 6: East Siberian Sea, 7: North Chukchi , 8: South Chukchi (basin Hope in eastern part)151~f ~2 ~3_4~5 bdo1:'0;oj7~8 [ll]9 8'0 "1 ~ 12Fig. 3: Correlation seheme ofAretie slope on Alaska and NorthChukehi Sea basin. I: Clastie de-posits, 2: Marine elays, 3: Conden-sated marine shale, 4: Argillite, 5:Limestone and dolomite, 6: Hiatusor erosion, 7: Coarse deposits, 8:Folded basement, 9: Granite, 10:Coal, 11: oil show, 12: gas show.EB~--" c" ... 'NorthChukchiseabasln"' , .9640JurassieD . 360evoman toProterozoio~1----144_c: 208t Triassie Illill~~~~~------~~~t:: 245co ~ _.t: PermianQ) 286ECI)~w CarbonHerousCenozOicQ,)os:::Q.):::I-ci'"'Q)VJc:.~75 Cretaceouseeo.......;..,. Ma -r"lo:-T'~__-:_:___=__~2In the Paleocene there was a transformation in the tectonicregime. Northern Chukotka underwent orogenesis and becamea source of terrigenous material. Continental facies is assumedfor Latest Eocene and Oligocene strata. A marginal marinelowland was limited by uplift in the South. Rivers cut thepreviously formed plain delta complexes. The seismic faciesconfiguration is typical of a progradational shelf 01' platform.Variable seismic characteristics of seismic sequences C and Bsuggest that they represent an alluvial plain 01' paralic deposits(Fig. 5). To the north, reflectors in these units become morecontinuous and parallel indicating that the sequence ispossibly marine in that area.The land area became subdued in Early and Middle Miocene,but was rejuvenated at the end of Miocene. Seismic unit Ashows the character of strata deposited in modern marineconditions. The sediments consist mainly of silt, mud andsand, its seismic characteristics suggest a marine depositionalsetting, the seismic reflectors are parallel and of low-ampli-tude. The large seismic disruption that begins from unit D andcontinues into younger units is interpreted to represent either astream of gas 01' the margin of a diapir.152CHUKOTKABSKZFig. 4: Structural schcme and geological profile. I: Acoustic basement counter line, 2: Fault, 3: Delta cone, 4: profile line.N3,.2.!1,oIkm i 4 km..'_.....&-.........- ...._ ...._ ....sFig. 5: Fragment of seismic profile showing seismic facies units.153DISCUSSIONThe eastern part of the Russian Arctic shelf has a very bigpotential for hydrocarbons; predominantly oil in upper Paleo-zoic and Triassie strata and gas in younger deposits. Thesubstantial thickness of sedimentary strata, and a favourableMesozoic to earliest Paleogene geothermal regime made for avery good environment for hydroearbons generation.Conditions in the Russian Arctic sector are different. Thewestern part apparently had a relatively stable platform regimeat the beginning of Paleozoie time, but rifting accompanied byintense subsidence took place in the Permian-Triassic. Thelarge quantity of terrigenous material was transported from theeast and southwest. It affeeted hydrocarbon generation anddetermined the distribution of oil and gas. Gas bearing stratain the upper part of the stratigraphie sueeession in the eentralpart of the Barents Sea are correlated with oil bearing upperPaleozioc strata in marginal parts of this area (Peehora Sea). Asimilar situation is interpreted for the margin of the Karsa Seawhere the giant gas-eondensate fields are loeated and evidenceof previous oil bearing in Paleozoic strata are found on thesurrounding islands.The eastern Russian Arctic shelf is part of the Asian-Alaskansector of the Aretic where oil fields were found in Alaska. Themain stratigraphie eomplexes are common 01' similar (ORUD-JEVA et al. 1999). There are two wide strips in the Asian-Alaskan sector of the Arctie. One strip which is more gasbearing than oil bearing extends from east to west, i.e. fromCape Lisburn to Gerald Island, Vrangel Island and farther westinto rhe Vostoehno-Siberian Sea This strip is dominated byyoung orogen molasse complexes. The second strip is north ofthe first one. Here it is believed that there is the possibility ofdiscovering oil in the large sedimentary basins, because theyhave some similarity to the Alaskan Arctie slope. The diffe-154rence in strueture and sedimentary history determines themain reason for the difference in hydroearbon oeeurrenees inthe west and east. The oil-bearing reservoirs are moreeommon in the east than in the west, particularly on theRussian Aretie shelf. This shelf and eontinental slope belongto the eireum-polar marginal zone system with big oil and gasbearing basins, have high hydrocarbon potential and deservespecial attention. The Russian Aretic basins is a great oil andgas province for the twenty-first eentury.ReferencesFichle}; cn.. Rundhovde, E., Johansen, S. & Saether; B.M. (1997): Barents Seatectonic structures visualized by ERS Isatellite gravity data with indica-tions of an offshore Baikalian trend.- EAGE, First Break, 15, NO.II: 355-363.Gramberg. I. (1997): Barentsevomorsky Permo-Triassovy paleorift i egoznachenie dlya problemy neftegasonosnosti Barentsevo-Karskoy plity.-Doklady Akademii nauk, 352, No.6: 789-791 (in Russian).Gramberg. 1., Piskarev, A & Belyaev, I. (1997): Blokovaya tektonika dnaVostochno-Sibirskogo i Chukotskogo morey po dannym analiza gravita-zionnykh i magnitnykh anomaliy.- Doklady Akademii nauk, 352, NO.5:656-659 (in Russian).Klubov, B. (1997): Natural bitumen shows within the Arctic Eurasian andNorth American margins.- Oil and Gas Geology 3: 10-16 (in Russian).Martirosyan, V, Popova, L. & Vepreva, M. (1998): The petroleum system ofthe Pechora Platform Foreland, Russia.- Petroleum Geoscience 4: 333-348Orudjeva D., Obukhov, A & Agapitov D. (1999): Prospects of oil and gasoffshore exploration in the Chukchi Sea.- Oil and Gas Geology, No. 3-4:28-33 (in Russian).Piskarev A, Manukhova A. & Chernyshev A M. (1997): Geodynamicheskayasystema morya Laptevykh po dannym analiza gravitazionnykh i magnit-nykh anomaliy.- Doklady Akademii nauk, tom 354, NO.2: 230-233 (inRussian).Thurston D. & Theiss, L. (1987): Geological report for the Chukchi Sea plan-ning area, Alaska.- Mineral Management Service, Anchorage, Alaska,193 p.

Russian Arctic Sedimentary Megabasin and Its Reflection in Oil and Gas Properties of Its Borderlands

Abstract

Similar works

Full text

Available Versions

Electronic Publication Information Center