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FOREIGN RELATIONS
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Geology
Sits On Riches Lives In Poverty 
 Oil and Gas Basins
Russia's OIL AND GAS BEARING BASINS Continental outskirts 1988
Environm against floating nuclear power 
 Oil and Gas Reserves Marketable
Anadyr Basin 1987 drilling
Osalochnye Basins Far East USSR 
Oil-And-Gas-Bearing Capacities 1987
Chukotka Auton Regn Overview 10 1998
Some Reserve Estimates
ANADYR BASIN
Seeking a Positive Commitment
exploration history
Roman Abramovich
Abramovich Canada Visit
Sibneft, managed by Roman Abramovich
exploration in difficult Far East basins
Low-Porosity Triassic Reservoirs of Barents Sea
ms  Chukotka Prof  Konstantinovich
THE PETROLEUM SYSTEM-CONCEPT AND APPLICATIONS
Pet Pot Shallow-areas of Russian Arctic
THE PETROLEUM SYSTEM-CONCEPT AND APPLICATIONS

Gregory F. Ulmishek, U.S. Geological Survey, Box 25046, DFC, MS 940, Denver, CO 80225
Leslie B. Magoon U.S. Geological Survey, 3475 Deer Creek Road, Palo Alto, CA 94304

A The petroleum system is becoming accepted as a unifying concept in which various research focused at finding new hydrocarbon reserves can be conducted more efficiently.  Proposed definitions of the petroleum system vary. 
The system is understood as a group of discovered and/or undiscovered genetically related hydrocarbon accumulations that emanated from a contiguous body of source rocks and that occupy a specific rock volume. 
The petroleum system map, which shows source rocks and the genetically related accumulations and cross sections which show the stratigraphic position of the accumulations, clearly demonstrate the explorationist's interpretation of the origin and migration route of hydrocarbons. 

Three petroleum systems are compared to graphically demonstrate how the concept is used in exploration, research and resource appraisal.  The systems, from most to least explored:
Northern China in the Jizhong subbasin
Northern Alaska in the Colville basin
Anadyr basin in the Bering Sea

Although the amount of information varies for each basin, the petroleum system can be meaningfully portrayed. The exploration geologist can use the petroleum system map and cross sections to develop plays, find undiscovered commercial quantities of hydrocarbons within the system. The system map and cross sections can be used as an analog for another area that contains a seldom-explored system. The research geologist can investigate and model how a system works, either in total or part, which helps in locating new plays and in decreasing exploration risk.  The appraisal geologist can evaluate the petroleum system map from a historical view to study discovery rate process or compare similar systems that have different levels of exploration to determine the ultimate yield of the little explored system. 
 

Fig, 6. Isopach map of the rocks of the Anadyr basin showing 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 cross-section is after Marlow et al, 1983, with changes according to Krylov et al, 1988).
 

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 presumed source rock occurs in the Eocene-Oligocene and possibly, in the lower Miocene sequences (Ivanov et al., 1988).  In the same stratigraphic intervals, 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 Anadyr basin.
Rocks of this stratigraphic interval are present in the southern depression of the offshore Anadyr basin where they occur at depths of up to 4 km (Fig. 6)  (interpretation of seismic data Marlow et al., 1983; Krylov et al., 1988).

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 probably present in the offshore Anadyr basin beyond the Tuman uplift (Fig, 6).  The exploration concept is to extend the onshore petroleum system offshore 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 or two petroleum systems.  If the uplift is young, and formed after the source rock became mature, then one system occurs. Whereas, if the uplift was formed before the source rock became mature, then there are two independent petroleum systems. 
An analogy with uplifts north of the onshore Anadyr basin suggests that the Tuman uplift is an old structure formed before deposition of the middle Miocene shale; therefore, the map of the Anadyr basin indicates two petroleum systems (Fig. 6). 
The areal extent of the offshore system (shown on map) is based on probable presence of mature source rocks: approximately along isopach 2.5 km and includes adjacent structural slopes.  The probable stratigraphic extent of the petroleum system is from Eocene through middle Miocene strata. It may also include the top of the Upper Cretaceous section underlying the source rocks, although onshore, this section is devoid of good reservoir rocks.  Exploration based on this play concept may further reduce the spatial extent of the offshore system when more data on reservoir rocks, maturity of source rocks, and quality of the regional seal become available.

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 North Slope of Alaska, mapping of the rocks that constitute the petroleum system is the best way to understand the extent of the system.  Here, discovered fields are clustered in a relatively small area so more geologic information may be needed to understand the entire extent of the system.
In unexplored frontier areas, mainly structural and limited stratigraphic data, coupled with comparative analysis of similar provinces, can be used to map the speculative petroleum system and to evaluate its probable stratigraphic extent.

The map of the system in this latter case presents the maximum possible extent of the system, and commonly, this extent decreases as more data on distribution of mature source rocks, reservoir rocks, and seals become available.  At all stages of exploration, a comparison between the proven lateral and stratigraphic extent of the system and its maximum possible extent indicates potential areas for further exploration efforts.  Using the petroleum system concept, plays can be developed to find commercial quantities of petroleum in unexplored extensions of the system.
 

ANADYR BASIN
ANADYR BASIN
P 64
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:
Ust' - Chirynajsk (P3/2 >) - sandy-argillaceous; 
Majnitsk (P3) with three under suites (bottom, argillaceous, middle, siltstone, and upper, sandy - siltstone); Sobol'kovsk (N1/1) - predominantly tufa - sandstone; 
Gagarinsk (N1/1), Avtatkul'sk (N1/1-2), Eliseevsk (N2/1), Ozerninsk (N2/1-3), Echinsk (N3/1-N2) and Aleksandrovsk (N2-Q), differ among themselves on nature of an interlayering dominating type of terrigenous formations, and enriched hydrocarbon and carbonaceous formations [45, 47]. 

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 [47]. 

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.

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65

text fig 29
Figure 29.
Pattern catagenesis of a field Anadyr of basin on a base surface Neogene of depositions 
1 - Boundary of basin and its frame; 
2 - Well and significance of magnitudes (OCB=OSV) in terms of R\3 base on Neogene surface; 
3 - Line of equal significance (OCB=OSV) (izoresplendy); 
4 - Areas with significance (OCB=OSV) = 7.0-8.00; 
6 - Tectonic disturbances influencing isometric figure of (a - thrust, overlap faults, b - sea disposals) 

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.

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68
Fig. 31. The allocation schem? of CK with (B  %) in Neogene and Paleogene siltstone depositions of Anadyr Basin.

1 - Boundary of basin its frame: 2 - point assay; 3 - line of the equal contents C/HK  %
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CK are referred to blended sapropel -humic to a type, or III to a type on classification of the French Petroleum Institute [170].

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.

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The total contents YB With, in formations Majnitsk suite vary 3 from less 0.01 to 0.09 of %, compounding in recalculation on C/nk 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
?12, more lighter dominate ?6 - ?10 (tab. 2) - ratio ?6-?10/?11-C15- is inflected within the limits of 0.7 - 56.3, averaging 7.6.

The formations Neogene of a complex, in the majority beds in zone of proto-catagenesis, have rather non-uniform allocation CK. According 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).
Owing to higher contents CK Neogene of deposition in the greater extent are enriched and bitumen with reductants, however extent bitumen CK in recalculation on Snk here is lower. Among bitumen dominates DSBB. In comparison with Eocene-Oligocene by a complex XB more oxidize also, contain less YB (see fig. 30). The IK-spectra point, that in pattern XB the basic role is played by chained aliphatic pieces. The stated materials in a combination to the data of element structure HOB (H/C at- 0.8 - 0.9) allows to speak about predominantly continental genesis CK Neogene of a complex.

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 cut-away.
p.70

 

exploration history
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.

 
Chukotneftegasgeologia 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.