Evaluation of the Late Evaluation of the Late Cretaceous-Cenozoic uplift Cretaceous-Cenozoic uplift and 1D petroleum systems and 1D petroleum systems

modeling of the eastern modeling of the eastern Barents SeaBarents Sea

Peter Sobolev 1, Nikolay Sobolev 1, Bernhard Cramer 2, Viktor Vasiliev 1, Evgeniy Petrov 1

1 A.P. Karpinsky Russian Geological Research Institute (VSEGEI), Russia2 Federal Institute for Geosciences and Natural Resources (BGR), Germany

The Russia Barents Sea – achievements and problems

+ One of the most promising shelf area in Russia – there are 11 large oil and gas deposits;

+ Plans to start an industrial development for several fields in the nearest future;

+ The area is studied beginning from 1970-s;- The area covered with surveys and wells very

irregularly;- All gas and oil fields related with Jurassic and Triassic

complexes, whereas for the Timan almost whole section is productive (from Ordovician up to Triassic).

- Large volume of data (especially on well logs) is not processed with modern methods.

Plan of the presentation

1. Recent compilative works of VSEGEI;2. Previous works on modeling on the Barents

Sea Shelf;3. Evaluation of Cenozoic uplift; 4. Thermal history assessment;5. Results of 1D petroleum systems modeling for

several wells;6. Plans for the future projects on the Barents Sea

Basin modeling.

Main objective of the presentation

How to get new information from the “old” data using modern computer methods

The estimation of hydrocarbon resources of the Northern Eurasia sedimentary basins based on geodynamic studies: 2006-2008

Karpinsky Russian Geological Research Institute (VSEGEI, SPb, Russia);

Senior executive is Nikolay Sobolev;

Principal goals: Compilation of geological-geophysical data on the Barents-Kara and Laptev Sea regions.

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Large volume of various data

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Structural maps

(Late Jurassic)

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Paleogeographic maps (Early Cretaceuos)

Geodynamic reconstructions

Main reasons to start modeling of the Barents Sea Basin

1. A large body of the data on the area (geological, geochemical, geophysical) and necessity of their generalization on a new level;

2. Lack of such approach in Russia;

3. Cooperation of VSEGEI and BGR (Germany).

1 stage 1D modeling (PetroMod) for several wells (2008)

2 stage 2D и 3D modeling (plans)

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Previous studies on modeling

2D modeling along 7 profiles (Barents and Pechora Sea)

Suprunenko, Oreshkin, Lopatin, Viskunova, Merkulov 2007

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Two principal problems that should be solved before to start modeling

1. Estimation of Late Cretaceous-Cenozoic erosion (or uplift) in the Russian Barents Sea:

Well log interpretation; Statistical methods of trend porosity evaluation; Sonic logs for shale intervals.

Vitrinite reflectance.

2. Reconstruction of heat flow history;

Recognition of principal rifting events.

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Estimation of thickness of Cenozoic erosion in the Barents Sea

Total thickness of Cenozoic sedimentation along the western Barents Sea margin,combined with erosion estimates (Dimakis et al., 1998)

1) There many studies of the uplift in Norwegian Sea and Western part of the Barents Sea.

2) There is no data on Cenozoic uplift in the Eastern part of the Barents Sea. Meanwhile this data are evalution not only for structural investigaions but for the petroleum exploration as well.

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Bezmaternikh, E.F., Kireev, Y.I., Yritsenko, I.I. Tertiary uplift and erosion effects on prospectivity. Proceedings of the International Seminar…, Murmansk, 1989, pp. 193-197.3

Boreholes on the Barents Sea shelf

Total number of drilled boreholes is more than 100

Parametric 11

Prospecting 71

Exploration > 40

Petrophysical analysis

+ 1D modeling

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Some problems related with well data

1. Very irregular representability – both in plan and in cross-section. Usually only gas and oil pays are studied in some details;

2. Very rare sampling: Up to 3-4 coring sections about of 5-15 m length

per well with bottom about of 3000-4000 m; Sludge Poor laboratory investigations of cores;

3. Low quality of geophysical logging data for many wells (digitizing errors, part of the whole section, variety of methods and devices etc.);

4. Absence of the reliable interpretation of geophysical logging for the most of wells.

Well log interpretation – 10 wells

gammasonic, polarization, resistivity

clay volume

porosity; lithology

Porosity trendlines for different rock types

Main unsolved problem – there isn’t a “calibration” curve with normal porosity trend

Porosity vs. depthtrend

• Erosion level • Rock type• Solution type•Sedimentation rate•Pore pressure•Temperature

Petrophysical analysis for 10 wells

Travel time (s/ft) – depth (m) Porosity – depth (m)

Porosity trends ( e- c·z )

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Erosion evaluation

Porosity curves calculated relatively Ledovay-1 well curves3

Rough evaluation of regional uplift

400 - 700 м

700 - 1000 м

> 1000 м

Isolines - seismic horizon “Г” – lower Cretaceous upper boundary

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Examples from the literature. (Jankowsky,1962; Magara,1976).

Magara(1976,1986) showed, that the acoustic interval transit time (Δt) of shales decreases exponentially with depth (normal compaction trend).

Magara’s sonic log extrapolation technique

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The main task – careful selection of data (Stokmanovskaya-1 well)

1) “Gamma-ray filtration”. Only points with GR > 100 API units were chosen for the next step (these values are typical for shales).

2) Values with the lowest values of Δt were taken to evaluate upper limit of uplift.

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Conclusion:

Upper limit of Cenozoic erosion is about of 500 m

Uncompacted shale value of approximately 200 s/ft (656 s/m)

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Vitrinite reflectance measurements

Conclusion: Uplift evaluation is about of 500 m

near-surface reflectance value is of 0.25%

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Timing of regional uplift

Cavanagh et al., 2006

SouthwesternBarents Sea

33.9 – 2 Ma

Pg3-N1

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D2-3

P-T

J2K1

P-T

Thermal history - subsidence curve analysis

K1

K1

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Time, Ma Epoch β Abun-dance

Occurences in neighbouring areas

115-125 K1 < 1.2 local Normal faulting and subsidence in the Western Barents Sea

160-170 J2 < 1.2 regional Rifting over major parts of the North Atlantic

240-260 P-T ~ 2 global Global boundary. Mass extinction, rifting, basaltic magmatism, beginning of Pangaea break-up

360-380 D2-3 < 1.2 regional Rifting and magmatism throughout the Russian Platform

Main rift events in the Barents Sea Basin (from the analysis of subsidence rate)

Heat flow changing during rifting – McKenzie model

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Petromod (PetroMod 1D)

1. Estimation of petroleum potential of Jurassic black shales;

2. Evaluation of the sources for the Triassic oil/gas pools;

3. Estimation of petroleum potential of the Devonian and Carboniferous sequences.

Petroleum systems modeling – some problems relating with the Barents Sea

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gas show-ings

gas pool

S-Kildinskaya-82: maturity history

5Kinetic models – Burnham(1989)_T2 for sapropelic, Burnham(1989)_T3 – for humus.

gas cond. pool

Stokmanovskaya-1: maturity history

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gas mainly

gas/oil showings

oil pool

Prirazlomanaya-1: maturity history

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1. Generation of the today´s petroleum pools begun in Mezosoic (mainly Triassic) and ceased with the uplift´s beginning (Cenozoic) in the central parts of the Russian Barents Sea Basin;

2. Gas pools of Lower Triassic are very likely indigenous; 3. Petroleum generation in the Jurassic sequence are unlikely

(though there are black shales with high organic content). However, it is possible to suggest “oil window” in the Jurassic layers for more submerged depressions;

4. Oil/gas in Paleozoic rocks were “cooked out” until Triassic for the Central Part of the Barents Sea. Than they might be imported into the areas with less subsidence;

5. For the marginal parts of the Barents Sea with reduced thickness of Mesozoic rocks a petroleum generation is possible during Mesozoic time.

Preliminary conclusions from the modeling of petroleum systems

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„Exploration strategy“ for the Barents Sea

Upper Jurassic

Lower Triassic

Devonian-Carbonifer

ous

Upper Jurassic

Lower Triassic

Devonian-Carbonifer

ous

Upper Jurassic

Lower Triassic

Devonian-Carbonifer

ous

oil window

surface

Central parts ofthe Barents Sea

Deep depressions of the Barents Sea

The Pechora Sea and highs in the Barents Sea

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Principal results

1. Reinterpretation of well log data

2. Qualitative evaluation of the Cenozoic uplift;

3. Several rifting events recognition in PZ-MZ;

4. Petroleum systems evaluations for different tectonic settings;

5. Modeling is a useful tool for many reasons:• Integration of data and knowledge;• Detection of errors and lack of data;• Formulation of new tasks;• Evaluation of hypotheses.

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Future tasks

1. Checking up the results and improve them:• Well log analysis;• Seismic profiles interpretation;• Thermal history assessment;• New laboratory investigations on lithology and

geochemistry;

2. A new project on 2D and 3D-modeling of the Barents Sea basin;

3. Using of such an approach for new areas…

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Petroleum system model of the Russian Barents Sea – what’s new

1. Open approach – publish as much as possible (both methods and data);

2. New joint interpretation of geophysical, lithostratigraphic, petrophysical data;

3. New petrochemical, petrographic, petrophysical measurements;

4. Several models of tectonic evolution. Two extreme cases: spreading (Aplonov) and rapid sagging (Artyushkov);

5. Full studies - from 1D to 3D models (different scales?).

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Today’s principal problems

1. Lack of the data Irregular distribution of wells and

profiles; Inhomogeneous set of data; Low quality of many data; Uncertainties with interpretation of

tectonic history;

2. Timing of Late Cretaceous – Cenozoic uplift;

3. Choosing of software for modeling;

4. Searching for an additional financial support.

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Thank you for your attention!