Russia's
OIL AND GAS BEARING BASINS Continental outskirts
MOSCOW "SCIENCE" 1988
Academy of Sciences USSR
The Ministry of Oil Industry
Awards of A Labor Red Banner
Institute of Geology and Development of
Combustible Minerals
N. A. Krylov
Ju. K. Burlin
L.I. Lebedev
The accountable editor academician I. S.
Gramberg
Fig. 36 Survey map of oil-and-gas bearing basins
of a
northwest part of Tihookeansk belts.
Basins: 1 - Sakhalin - Hokkaido (Zapadno
Sakhalin),
2 - Sakhalin of Okhotsk (North Sakhalin),
3 - South - Sakhalin,
4 - Okhotsk - Kamchatka,
5 - east - Kamchatka,
6 - central Kamchatka,
7 - Il'pin-Vyvensk,
8 - Olyutorsk - Komandor,
9 - Hatyr,
10 - Anadyr,
11 - Navarin,
12 - Bristol (Nushagak),
13 - Kuka Embayment,
14 - Yakataga (Saint-Elias)
15 - south Kurile
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
characterized by
rather local progressing in keystone faults. Frequently these
lagoonal-continental
deposits bridged by a jacket larger discharge (page 128) Bending
flexures
with marine deposits features are peculiar of northern part of Bering
Sea,
northern, and eastern parts of Okhotsk. All these patterns in areas of
reshaped crust are of young, subcontinental, pluton type, and on land
of postorogen
stage of progress.
Figure 37 Anadyr basin survey map
1 - Boundary of basin;
2 - Rough iso-heights on one of horizons in lower
of
a part of Cainozoic depositions km
3 - Gas and oil aggregations;
4 - Explosive disturbances;
5 - Areas of an approximate occurrence of the
foundation
ZG of Zolotogorskoe upheaval;
AH (AN = AH) - Anaut upheaval;
P (R) - Rarytkinsk fold back zone;
K - Koryak of Skladchato - Pokrovno zone
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
Predrarytkinsk
bending flexure.
Most interesting is the basin southern part. It
is possible
to guess that in the folded basement complexes formed in depressions,
such
as deep-water pocket Mesozoic and early Cenozoic age, are advanced
predominantly
terrigenous slate and flysh. In Paleogene, in separate leases, probably
inherited from chalk time, the serial of the depressions that have been
carved out from each other is reshaped by extension disturbances. On
the
Eocene and Oligocene boundary, active processes of contraction were
made.
Later, at the end of Miocene, it was expressed
in a thrust
on the north. The frontal parts of blocks and laminas have blocked
sedimentary
strata of the bottom complexes. The zones of maximum Eocene-Neogene
sedimentation
clearly gravitate to southern parts of bending flexures.
From the south, on land, Anadyr basin is bounded
by Pokrovno-bowed
structures of Navarin branches expressed by way of Koryak upland. Here
among volcanic sediment strata, the forming laminas are contracted
hyper-base
massifs. The communal move of mass is directional to north. On separate
leases of formation of frame bridge basin formations, under chalk and
hyper-base
massifs formations of the Neogene. Some structural lines of a frame
proceed
under a hollow in a northeast direction - Chirynajsk upheaval,
Tumanskoe
upheaval.
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,
6-7 km.
The attitude of formations can be seen on a profile cut-away (figure
38),
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
130)
(Avtatkul'sk and other suites) occurring basin, forming a communal
raincoat
a figurative overlying strata escaping far beyond Majnitsk bending
flexure.
Figure 38 An
idealized profile cross section of southern Anadyr basin
1 - Sandstones, siltstones, clay, hardpans coal
Telekajsk
2 - Sandstones, less often siltstones Avtatkul'sk
suite
3 - Sandstones, siltstones, clay Gagarinsk suite
4 - Sandstones, with hardpans of siltstones
Sobol'kovsk
suite
5 - Mudstone, siltstones Majnitsk suite
6 - Cause Mesozoic age
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
bearing complexes
are allocated; Middle Eocene oil-and-gas bearing (Avtatkul'sk suite),
lower
Eocene oil-bearing (oil-producing) (Sobol'kovsk suite, oil ingress's
and
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
Miocene
on east-Lake upheaval referred to northern frame of Majnitsk bending
flexure.
In limits this of upheaval in skv ? 2 the most significant gas kick
from
depth 1288 - 1313 m in an opened trunk was received.
Header are the polymictic medium sandstones with
an accessible
porosity about 20 % and insight 200 - 300 mD. From Avtatkul'sk of suite
some inflow ?????? on upper - Juchinsk of the floor space are received.
The maximum inflow had a rate of yield 38 m/day. A peculiarity of oil
at
gravity 0,819 - 0,824 is the high contents of paraffin - from 14 up to
22,6 %, contents of aromatic - up to 5 - 8 %. From stratigraphically
more
deep levels in structure of Sobol'kovsk of suite also are received oil
inflows on upper - Telekajsk area specially intensively in skv 3 (159
m3
/day) and 9 (two horizons in a depth interval 1850 - 2000 m). The rate
of yields compound in the latter case at trial by a formation tester
about
90 and 130 m/day, oil of the same type, as on upper - Juchinsk of the
floor
space, contents of paraffin up to 28 %.
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
in considered
region Tikhookeansk segment three basic provinces: northern belt of
metamorphic
formations dokembriya and Paleozoic, igneous belt, reaching from Asia
to
Alaska, and advanced frontal belt embedded inside of it bending
flexures
near to edges of deep-water basins. To a southern part of this belt
Navarin
basin is referred also, it is characterized Mesozoic by the basis,
folded,
and modestly dislocated. END
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