Baltic Financial and Industrial Group” (BFIG)
Sibneft and Yukos JV August 09 2001
Sibneft Exploration August 27 2001
drilling on offshore
|Anadyr basin survey map||
CONCEPT AND APPLICATIONS
|An idealized profile cross section of southern Anadyr basin|
||Low-Porosity Triassic Reservoirs of Barents Sea||Pet Pot Shallow-areas of Russian Arctic|
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Chukotka Regional Administration
Governor’s Office 20 Beringa Street
Anadyr, Chukotka, Russia 689000
Governor: Roman Arkadievich Abramovich
Standard time zone: UTC/GMT +12 hours
MOSCOW "SCIENCE" 1988
Academy of Sciences USSR
The accountable editor academician I. S.
Basins: 1 - Sakhalin - Hokkaido (Zapadno
The dislocated terrigenous depositions of bow zones - relic of bending flexures of earlier stages of progressing, and also separate blocks and clumps flinty of igneous formations ocean stage of progression.
The special group of bending flexures is compounded North Sakhalin and West by the Kamchatka bending flexures. A constitution of a sedimentary jacket and the basis of these bending flexures allow to esteem them in merit of patterns of the uncompleted geosynclinal progression, which partially began a stage of an orogenesis. The progression of these bending flexures originated within the limits of zones of extensions, in which there was a submergence on late Cenozoic stage of progression involving in submergence fold structures, adjacent to them, of a frame. The heterogeneity of bending flexures is on the one hand, consequent of their location on boundary Kvaziplat uniform Okhotsk pattern with bowed structures of Kamchatka and Sakhalin, and with other - on presence at their frame of blocks earlier (Dokembry - Paleozoic) consolidation composed metamorphosed volcanic formations of but - sedimentary nature.
The exterior position in northwestern part of Tihookeansk belt is occupied by basins on young gantries which were taken up by water areas and having close connection with an intermountain, by a having on land, in which one was already established make room a mode. Examples serve by Anadyr basin of Chukotka and Bristol basin on Alaska.
The bottom of a sedimentary jacket is
rather local progressing in keystone faults. Frequently these
deposits bridged by a jacket larger discharge (page 128) Bending
with marine deposits features are peculiar of northern part of Bering
northern, and eastern parts of Okhotsk. All these patterns in areas of
reshaped crust are of young, subcontinental, pluton type, and on land
stage of progress.
1 - Boundary of basin;
Among all available variety of basins (fig. 36), it is possible to distinguish categories on structure of formations of basins composing them, including single class and poly-formations. The rather simple sedimentary oil-and-gas bearing basins composed are allocated to several formations. For example, among orogenic basins there are varieties folded only by one molasse (of basement rocks the roles containing oil or gas) did not play, and the varieties, in a constitution and oil-and-gas-bearing capacity which in this or that material measure participate depositions previous orogenic stages. These last basins are usually dated for bending flexures and basins of inherited progression.
Anadyr basin in modern pattern at ground level introduces a discordant superimposed depression, framing edges bow and over-lying strata by bow structures (fig. 37). The basin foundation is partly upper-Jurassic lower-chalk dislocated strata, and partly one of branches early Cainozoic igneous belt passing from Chukotka through the Bering Sea to Alaska. In northern part of basin on volcanics occurs a rather light-duty jacket of early (p.129) Miocene marine, Pliocene and Pleistocene littoral-marine and continental deposits. Under this jacket, on separate leases, grabens are present descriptive bending flexures implemented carbonic late chalk - Paleogene depositions. Western limitation of basin is back Rarytkin formed by folded chalk structures, in height of a cut-away which concern is introduced with a terrigenous carbonic stratum (1200 m+) of Danish Maestrictian age.
Along the back of Rarytkin is stretched the
Later, at the end of Miocene, it was expressed
in a thrust
on the north. The frontal parts of blocks and laminas have blocked
strata of the bottom complexes. The zones of maximum Eocene-Neogene
clearly gravitate to southern parts of bending flexures.
Between these two upheavals located wings figurative, stretch Majnitsk a bending flexure, in east along of axle, and then northeast direction Telekajsk-Povorotno of anticlinal zone is traced. The oil fields are connected to the most western local upheavals of this zone (upper Juchinsk and upper Telekajsk). The part of Majnitsk bending flexure-taking place to north from anticlinal zone sometimes is referred to as a "Flowing bending flexure". In the south Majnitsk of a bending flexure is partial under overlying stratas of a southern bead the patterns of one more anticlinal of zone are scheduled. To east from Majnitsk, being separated Tumansk upheaval, lays out a Lagoonal bending flexure opening already in the sea and compounding began circuits within reach in water area of bending flexures.
The communal submission about Anadyr bending flexure is possible to see in figure 37. Majnitsk bending flexure on thickness of sedimentary implementation rather is allocated in Anadyr basin. The thickness in it accrues from beads to the most embedded part promptly.
So on upper-Telekajsk upheaval an occurrence depth height of basal Miocene (Gagarinsk and Sobol'kovsk suite) compound 1500-2000 m, and these strata are dipped in 20 km to the south already on depth about 4500 m.
Final depth of a bending flexure, is probably,
The attitude of formations can be seen on a profile cut-away (figure
drilled by seismic survey Telekajsk area and further is almost meridian
from the south from a frame up to upper Telekajsk area and further. On
a profile the appreciable dislocation in strata of the mentioned suites
are visible. Only above bedding formation from middle Miocene (page
(Avtatkul'sk and other suites) occurring basin, forming a communal
a figurative overlying strata escaping far beyond Majnitsk bending
Figure 38 An
idealized profile cross section of southern Anadyr basin
In Anadyr basin, it is possible to dedicate four large complexes distinguished on structure and parted partially by unconformities. The first lithologic series in the central part of basin is folded, poorly lithified sandy-argillaceous depositions upper Eocene and Pliocene of age (Telekajsk series). They mirror an independent sedimentation cycle of offshore-marine situations of basin correlation.
Within the limits of a marine part of basin (Anadyr bending flexure) this lithologic series, apparently s east -, the bottom of seismo-complex A. Vtor?j by Second Lithologic series answers engages depositions lacustrine and Avtatkul'sk suites of mean Miocene. The depositions of Eliseevsk of suite are introduced a uniform stratum sandy clayey of siltstones with hardpans silty of sandstones and clays. Avtatkul'sk suite almost is wholly folded by continental sandstones with hardpans of siltstones and clays, to a lesser degree gravel conglomerates with clay hardpans, that testifies to its shoal-marine genesis.
In east (marine part) Anadyrsk basin ???? to suites would answer seismo-complex. It is characterized by tabular velocities 2,5 - 3,2 km /sec., that will well be agreed the data of vertical seismic profiling (VSP) in overland parts of basin (2,4 - 3,1 km /sec). Third lithologic a series in limits of central Anadyr of a bending flexure is advanced locally in Majnitsk a bending flexure. To it are referred Gagarinsk and Sobol'kovsk of suite early Eocene age. The thickness of suites is inflected in a wide range from first 100 meters on Sobol'kovsk area up to 1500-2000 meters on upper Echinsk area. The particular lithological and petrophysical properties allow confidently to dedicate and to correlate them within the basin limits. The suites are referred to alluvial - divided between offshore marine (bars and interspersed) and outward to shelf formations. The classic differentials are folded tuff generated by fine-medium sandstone with Zeolite cement.
By works of VMNPO of "Goyuzmorgeo" 1983 in limits East-Anadyr bending flexure the complex is allocated, which by us is conditional parallel with lower Miocene depositions. Within the bending flexure limits, the complex thickness does not exceed 1,5 km, which is less than in Majnitsk basin is central -Anadyr bending flexure. American explorers in Anadyr embayment allocate two basic reflection horizons alpha and beta. The boundary velocity of a reflection horizon alpha is inflected in a range from 3,6 - 3,9 km /sec, and horizon B - accordingly 4,3 - 4,8 km /sec. Apparently, surface of seismo-geologic complex is Parallel with horizon alpha. The tops of a complex on upheavals are cut off.
Below than seismo-geologic complex in bedding a complex G is structurally dated for large grabens between protrusion of the foundation. Most likely, this complex includes age analogues Majnitsk suite of Oligocene - Eocene of the same bending flexure on land. On seismo-profile, the beaded bodies are allocated. Majnitsk suite in a ground-level part (page 132) is introduced in the basic mudstones, however are present Paleogene stratum and diverse structure. The abrupt variability both age, and facies structure of a complex G is exhibited in progressing sub-complex of a beaded constitution, which answers several transgressive - regressive cycle. In a cut-away east Anadyr bending flexure it is possible to guess primary progressing of sandy-argillaceous strata with the slave significance of coarse clastics.
In Anadyr basin on land the oil-and-gas
are allocated; Middle Eocene oil-and-gas bearing (Avtatkul'sk suite),
Eocene oil-bearing (oil-producing) (Sobol'kovsk suite, oil ingress's
in overlying Gagarinsk), interquartile, oil-and-gas bearing upper chalk
here gravitate. Some vertical ash value is planned, thus. The first gas
horizon was opened up a key hole in Avtatkul'sk to suite of middle
on east-Lake upheaval referred to northern frame of Majnitsk bending
In limits this of upheaval in skv ? 2 the most significant gas kick
depth 1288 - 1313 m in an opened trunk was received.
The tested objects, apparently, do not belong to the determined benches, and are fractured zones, that are well visible in a core. The petroleum composition, on the one hand, speaks about its genesis from humic material, which is characteristic for littoral-marine subcontinental of conditions of formation of these strata. In addition, with other - testifies about streams of oils metamorphosed from the most embedded parts of Majnitsk basin, where, probably, the centers of the petroleum formations are laid out.
One more perspective object is the upper chalk deposition. In span of wells from them water by a rate of yield up to 25 m /day with emulsified crude oil is received.
Southeast of the Anadyr basin, on the edge of continental shelf is located Navarin basin. In constitution, it participates Cenozoic strata spread chalk.
Many Soviet and American geologists allocate
region Tikhookeansk segment three basic provinces: northern belt of
formations dokembriya and Paleozoic, igneous belt, reaching from Asia
Alaska, and advanced frontal belt embedded inside of it bending
near to edges of deep-water basins. To a southern part of this belt
basin is referred also, it is characterized Mesozoic by the basis,
and modestly dislocated. END