Oct 21, 2013 - 2013-10-21. 8. = . P-wave velocity. Lithology. Present-day thermal conductivity. Example from Viking Graben, North Sea ...
Integrated basin-scale thermal modeling Ketil Hokstad, Rune Kyrkjebø, Kenneth Duffaut, Christine Fichler, Zuzana Alasonati Tašárová, Torgeir Wiik, Andrew J. Carter, Eirik Dischler, Øyvind Kjøsnes Statoil Research Centre, Trondheim
EAGE, Amsterdam, 18. June 2014.
Introduction Temperature history is important for petroleum exploration: • Source maturation • Reservoir quality Integrated thermal modeling: • Geophysical observations • Kinematic restoration
Example of quartz cementation.
• Rock physics model
(from Walderhaug-Porten (2012), MSc thesis, NTNU, Trondheim)
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Thermal modeling
Temperature
Geological time
Present-day temperature
Diffusion equation
Max paleo temperature
Dræge et al., TLE, 2014
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Steady state
Rock physics model: Underlying principles • Simplified rock physics model aimed at basin-scale frontier exploration • Fundamental parameters controling all geophysical parameters (Vp, K, density) are:
− Porosity − Lithology
• Rocks have «memory»
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Rocks have ‘’memory’’!
Rock physics model : Thermal conductivity Heat conductivity (𝐾) :
𝐾 = 𝑎(𝐿)𝑉𝑃
Depth (km)
𝑉𝑃 = seismic velocity 𝐿 = "lithology parameter”
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Adapted from Rybach (1997) (1997)
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Depth (km)
Steady-state temperature from well data
__ 50 0C/km __ Rock physics model o MDT o BHT 460C NPD
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Thermal conductivity in 2D and 3D P-wave velocity
Present-day thermal conductivity
Lithology
𝐾 = 𝑎 𝐿 𝑉𝑃 Example from Viking Graben, North Sea
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Elements of time-dependent thermal modeling • Backstripping: (time-reversed geology) 1D
− Background porosity trend − Heat conductivity (velocity)
2-3D
− Density, − Velocity • Basal heat flow history
Temperature modeling
− Crustal stretching and thinning Geological time • Solve the heat equation − 1D Finite Difference − 2D Finite Difference
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Backstripping
Viking Graben: Seismic line NSDP-84-1 P-wave velocity
• Horizons of interest: • BCU (source) • Top Brent (res) • Top Statfjord (res)
Lithology
• Projected wells: • 34/11-2S (Kvitebjørn) • 35/11-7 (Troll area) Previous work on NDSP-84-1: • Kyrkjebø (1999) • Odinsen et al. (2000) • Christiansson et al. (2000)
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Backstripping velocity, density and K Present-day thermal conductivity
Decompaction
Frozen
Time of maximum burial Two episodes of Neogene uplift (=erosion) in the east
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Viking Graben: Macro-trend (compaction curve)
Macro trend is obtained from • Seismic interval velocities • And/or density (gravity modeling)
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Barents Sea: Macro trends from seismic velocities and density depth function (gravity)
Seismic velocity trend functions
Density-depth function from gravity Porosity:
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Viking Graben: Basal heatflow history 0 Ma
-65 Ma
-165 Ma
Tectonic restoration – β-factors Rune Kyrkjebø (1999); PhD Thesis
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Crustal thickness
Basal heatflow
Seismic velocity and heatflow
Seismic velocity and temperature
Thermal modeling Projected well 34/11-2S (no uplift)
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Comparison with 34/11-2S well (Kvitebjørn)
____ Time dependent: Seismic ____ Steady state: Seismic ____ Steady state: Well log 18
Thermal modeling Projected well 35/11-7 (500m uplift)
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Comparison with 35/11-7 well (Troll area)
____ Time dependent: Seismic ____ Steady state: Seismic ____ Steady state: Well log 20
Synthetic example: Generic effects of subsidence (sedimentation) and uplift Temperature at z=2.5 km
subsidence
Subs./uplift turned ON
Subs./upift turned OFF
uplift
• Subsidence&sedimentation => cooling • Uplift => first heating; then cooling; • Effect of advection and changed conductivity
Black: Reference (steady) Red: Subsidence 50 m/My Blue: Uplift 50 m/My
Viking Graben: Thermal equilibrium? Projected well 35/11-7: • Aproximately thermal equilibrium • Neogene uplift and erosion
Projected well 34/11-2S • Not in thermal equilibrium • Neogene sedimentation • Pliocene sed.rate: 170 m/Ma
____ Time dependent ____ Steady state 22
Top Brent Temperature
Top Brent Quartz Temperature cement
(Walderhaug, 1996)
BCU Transformation ratio
(1st order Arrhenius reaction)
BCU Vitrinite reflection
(Burnham and Sweaney 1991)
Conclusions • New appraoch to thermal modeling − Based on geophysical data and rock physics model
− Objectives and application similar to conventional basin modeling • Demonstrated on Viking Graben (Line NSDP-84-1) • Tested with good results in a different settings, inside and outside Norway
− Continental shelf, passive margin, subduction zone
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Acknowledgements We thank • Ketil Kåsli for initiating our research on thermal modeling
• Kjell Inge Skjønberg for turning our research Matlab codes into Petrel plugins • Anders Dræge, Jan Ove Hansen, Kristin Rønning, Torbjørn Dahlgren, Luppo W. Kuilman, Michael Erdmann, Stoney Clarke, Lill-Tove W, Sigernes and Olav K. Leirfall for discussions • Statoil for permission to publish this work
Reference:
Hokstad, K. , Wiik, T., Dræge, A., Duffaut, K., Fichler, C., and Kyrkjebø, R. (2014), Temperature modeling constrained on geophysical data and kinematic restoration: Patent Application No WO/2014/029415
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