Osalochnye Basins Far East USSR
Oil-And-Gas-Bearing Capacities 1987
|Chukotka Auton Regn Overview 10 1998||
Abramovich Canada Visit
Sibneft, managed by Roman Abramovich
SYSTEM-CONCEPT AND APPLICATIONS
Gregory F. Ulmishek, U.S. Geological Survey,
DFC, MS 940, Denver, CO 80225
A The petroleum system is becoming accepted as
concept in which various research focused at finding new hydrocarbon
can be conducted more efficiently. Proposed definitions of the
Three petroleum systems are compared to
how the concept is used in exploration, research and resource
The systems, from most to least explored:
Although the amount of information varies for
the petroleum system can be meaningfully portrayed. The exploration
can use the petroleum system map and cross sections to develop plays,
undiscovered commercial quantities of hydrocarbons within the system.
system map and cross sections can be used as an analog for another area
that contains a seldom-explored system. The research geologist can
and model how a system works, either in total or part, which helps in
new plays and in decreasing exploration risk. The appraisal
can evaluate the petroleum system map from a historical view to study
rate process or compare similar systems that have different levels of
to determine the ultimate yield of the little explored system.
Fig, 6. Isopach map of the rocks of the Anadyr
the supposed offshore petroleum system and cross-section on through the
onshore part of the basin. (The map is after Deter et al., 1986; the
is after Marlow et al, 1983, with changes according to Krylov et al,
The offshore part of the Anadyr basin in the Bering Sea is an undrilled frontier, which contains a speculative petroleum system. A grid of seismic lines covers the area (Marlow et al., 1983), and interpretation of the seismic data is based on drilling in the onshore part of the Anadyr basin and in the Navarin basin to the south (Fig. 5).
Drilling in the onshore part of the Anadyr basin revealed a sedimentary section consisting of Upper Cretaceous through Pliocene rocks overlying the Jurassic-Lower Cretaceous basement and separated into sequences by pre-Eocene, pre-Miocene, and pre-middle Miocene unconformities (Voronkov, 1987).
Several, non-commercial oil and gas fields and a number of hydrocarbon shows, which demonstrate a petroleum system, were found in the deep part of the basin on the south.
Although geochemical data are limited, the
rock occurs in the Eocene-Oligocene and possibly, in the lower Miocene
sequences (Ivanov et al., 1988). In the same stratigraphic
source rocks have been identified in the Navarin basin (Steffy et al.,
1985). Therefore, a potential source rock can be expected in the
upper Paleogene through lower Miocene rocks in the offshore part of the
The rocks pinch out toward the southern and northern slopes of the depression and on the Tuman uplift on the western flank.
Onshore, the top of the oil window occurs at depths varying from approximately 1.8 to 2.6 km (Ivanov et al, 1988).
Hydrocarbon pools and shows onshore arc dominantly concentrated in siliciclastic reservoir rocks of early and middle Miocene age. Middle Miocene shales to 330-m thick (Yeliseev Formation) form a regional seal. These rocks are present over all the depression, and overlap inner and marginal basin highs and extend into the offshore basin.
These data indicate that a petroleum system is
present in the offshore Anadyr basin beyond the Tuman uplift (Fig,
The exploration concept is to extend the onshore petroleum system
using structural data. The offshore system is separated from the
onshore system by a structural barrier, the Tuman uplift. The age
of the Tuman uplift is important to determining whether there are one
two petroleum systems. If the uplift is young, and formed after
source rock became mature, then one system occurs. Whereas, if the
was formed before the source rock became mature, then there are two
These examples demonstrate that the proven extent of the petroleum system is shown by a line that circumscribes a mature source rock and genetically related oil fields and significant shows. This map is easily made in c provinces where most of the fields have been found and a substantial amount of geological and geochemical data are available. However, even in these provinces, lateral extensions of the petroleum system can be expected based on mapping of the geometry of the rock body that contains the oil and gas fields within the system. This extension of the petroleum system can be the basis on which a play is predicted.
In moderately explored areas, such as in the
of Alaska, mapping of the rocks that constitute the petroleum system is
the best way to understand the extent of the system. Here,
fields are clustered in a relatively small area so more geologic
may be needed to understand the entire extent of the system.
The map of the system in this latter case
maximum possible extent of the system, and commonly, this extent
as more data on distribution of mature source rocks, reservoir rocks,
seals become available. At all stages of exploration, a
between the proven lateral and stratigraphic extent of the system and
maximum possible extent indicates potential areas for further
efforts. Using the petroleum system concept, plays can be
to find commercial quantities of petroleum in unexplored extensions of
The basin is connected to the same superimposed depression, which one bridges complex zone of an articulation of flank decay of Anadyr - Koryak of system Cenozoic with junction by patterns of Chukotsky Mesozoic and western protrusion Chukotsky - Stjuardsk block. Besides, here are stretched chalk Willingly Chukotsky and Paleogene Anadyr - Bristol'sky vulcanology belt.
Two zones are allocated in the common basin plan. In north and northeast, the complex of sedimentary implementation is introduced only young (N-Q) coarse deposits thickness up to 2 - 2,5 kms, which bedding is direct on Eocene- effusives bridging. In turn more ancient, miscellaneous formation genesis and structure occurs in the folded basement. These areas differ by poorly contrasting tectonics, flat dip of strata, co-sedimentation type of local upheavals. At southern edge of this zone under Paleocene-Eocene effusive the marine terrigenous and continental carbonic formations upper chalk, forming a buried floor complex of implementation are laid out.
The leases of basin, approximate to its southern and southwest frame, differ greatly. Up to 3 - 5 kms thick depositions of Neogene-Quaternary and presence under them essentially of argillaceous and silty-argillaceous upper Eocene - Oligocene formations (up to three kms). Early Paleogene volcanics here are abbreviated in thickness and are replaced by terrigenous formations.
Below at a cut-away of a buried floor of implementation there are terrigenous strata and - Cenozoic tufa siltstone depositions. In these areas, young diastrophic movements with horizontal compounding were brightly exhibited. That caused formation overlap faults and thrusting, along which the narrow highly peaked anticlines frequently complicated by the phenomena of current argillaceous mass, and disconnected detachment fault are laid out.
In limits most known Cenozoic part of a
cut-away of basin
from below following suites and strata upslope stand apart:
Anadyr basin is well understood in the regard of pattern of catagenesis in this region [47, 65, 158]. Tectonic discontinuity of basin, thermal properties of formations, availability in a cut-away of truncations, fluid washes and unconformities, progressing of explosive disturbances, transformation a calorific area and forms by high heat generation. All these factors attach a catagenic complex areal nature (fig. 29). Thus, frequently prove, that the same litho-stratigraphic divisions in different areas are resized rather variously, quite often even on the neighbor leases, where they are approximately on equal depths. All this results that the separate suites and strata are characterized by a wide range of catagenic transformations .
Standard chemical - bitumen examination the performance of clay materials of Anadyr basin results in fig. 30. It is necessary at once to point out, that the contents in CK bituminous reductants and their structure on the given generalized schedules mirror not only feature of original composition ??, but also the non-uniform conditions catagenesis, in which various lithologic-stratigraphic division. Lower tufaceous formation, opened up by a well in the central part of the basin, 1.2 % contain a (beta/XB) in amount 1.1 -1.2%, but are characterized by minute concentrations XB and low significance of bitumen coefficient (p), As formations of this complex bedding in optimum from outlook oil generation to zone catagenesis (MK3), the low contents in them dissoluble is possible to believe, that reductants is connected to features of structure CK and with influencing of tufogennogo such as mineral environment.
text fig 29
Upper deposition of a buried floor of implementation of basin are enriched CK in some smaller extent (see fig. 30). The extent of their catagenesis transformation varies in a range of gradation MK\2-MK\4 (concluding V. N. Boroiaeva, A.A. Koshunova, A.I. Utkinoj). However, for a facies type CK is essentially humic arkose, the contents XB and magnitude beta\XB here nevertheless is higher, than in underlying a complex.
Paleogene depositions abundant only in a southern part basin are inflected in a wide range of catagenesis (PK/2-MK/2) [27, 47, 153), but in the basic part deposition in conditions of zone of mezo- catagenesis. Eocene-Oligocene deposition in structure of Ust'- Chirynajsk and Majnitsk suites are characterized contouring inclusive CK. Within the limits of this complex of concentration C/nk in siltstone formations grow from 0.54 % in mean - upper under suites of Majnitsk of suite up to 0,79 % in under majestic and 0.77 % in Ust-Chirynajsk. In the plan of the contents Cnk (NOV) are augmented from less 0.5 up to more than 0.7 % in a southwest direction (fig. 31). On the data of element analysis of the allocated concentrate CK (IS NEW) and pyrolysed (?/? at = 1.0; hydrogen and oxygen subscripts 150 mg ??/g? and 130 mg ??2/??/nk accordingly).
The resulting data are referred to CK, converted not more strongly than gradation PK/3.
1 - Boundary of basin its frame: 2 - point
assay; 3 -
line of the equal contents C/HK %
CK are referred to blended sapropel -humic to a type, or III to a type on classification of the French Petroleum Institute .
In balance of dissoluble reductants CK the equal proportion neutral (XB) and acidic (DSBB) bitumen or dominance maiden of them (Ust' - Chirynajsk stratum) takes place approximately; the IK-spectra XB confirm commingle sapropel -humic a nature SK - rich-dark occluding in field 850 - 700 cm\-1 in a combination to a bar mean intensities at 1600 cm\-1 and with strong occluding in field 1720 - 1700 cm\-1. The extent re-establish XB (back is proportional contents GZ), and contents in XB YB C15 + here optimum in all cut-away. Extent and polymodality of the schedules of allocation standard chemical carbon bitumen index of clay materials Paleogene of age testify to active processes reallocating in them mobile of reductants.
The total contents YB With, in formations
vary 3 from less 0.01 to 0.09 of %, compounding in recalculation on
0.5 up to 9.2 %. The proportion of concentrations of factions C15?/C15+
changes within the limits of 0.2 - 0.54, thus inside of factions Page 70
The formations Neogene of a complex, in the
in zone of proto-catagenesis, have rather non-uniform allocation CK.
to magnification saturated. Upslope on a cut-away ascending dispersions
of the contents Snk from 0.18-2.53 % in Gagarin and Sobol'kovsk suites
to 1.69 - 7.87 % in Aleksandrovsk is fixed. Enriched Snk of silty-clay
materials Neogene grows from central to western and southern inshore to
zones (see fig. 31).
The contents YB C1+ in formations Neogene is inflected from 0.003 up to 0.13 % and compounds in recalculation on Cnk 1 1 4.6 %. Among YB C1+ considerably dominate C15+, (the ratio of factions C15 /C15+, as a rule, does not exceed 0.27), inside of lighter YB C1+ the dominance more lighter YB C6-C10 (ratio C6-C10/C11-C15 on the average equally 13.5) is hardly expressed.
Contrast enough distinctions of physical-genetic types CK Neogene and Paleogene complexes of depositions are exhibited at comparison of the data on allocation normal alkanes and regular isopentane C15 +. On catagenesis a level (PK3) of significance of coefficient of oddness normal alkanes CPI in formations Neogene compound 3.3 - 6.7, whereas for Paleogene of depositions of significance CPI do not exceed 2.9. The ratio Pr/n-C17 is inflected from 4.1 up to 13.8 in formations of Neogene age and from 1.6 up to 3.7 in Paleogene formations; the magnitudes of coefficient Pr/f compound 4.2 - 8.3 and 1.3 - 4.1 accordingly.
For formations of both complexes converted within the limits of gradation MK1, - MK3 learning individual structure low-boiling YB With, (tab. 3) was implemented.
As it is visible, the distinctions of types CK are exhibited in means of indexes of a faction YB C7 clearly.
3 Summary contents in ?? C15+ here in all
ARCO has signed preliminary agreements with two local governments covering E&P in the Soviet Far East.
ARCO's protocols with regional councils of Magadan and the Chukotka Autonomous Area pave the way for ARCO to negotiate for exclusive rights for onshore and offshore E&D. Target areas will be identified in subsequent negotiations. The councils will help ARCO obtain required legal approvals of the Soviet and Russian Federation governments.
January 12, 1993
In a deal that could lead to a joint venture agreement, IPC and Chukotneftegasgeologia have a joint study agreement covering an area in the Chukotka region. The two will assess the technical and economic feasibility of producing small onshore oil fields in the ANADYR ANDKAHTYRKA BASINS,aimed at yielding exports for western markets.
Crude from the two basins has a high wax content, but it is low in sulfur and the fields are close to the Pacific Coast.
IPC said depending on results of the study, it could enter a production agreement with Chukotneftegasgeologia in the next 2-5 years.