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PESA DL 2009 PJ Boult Page 1 In requesting the services of GINKGO ENP GNG the client agrees that GINKGO ENP GNG is acting in an advisory capacity and shall.

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Presentation on theme: "PESA DL 2009 PJ Boult Page 1 In requesting the services of GINKGO ENP GNG the client agrees that GINKGO ENP GNG is acting in an advisory capacity and shall."— Presentation transcript:

1 PESA DL 2009 PJ Boult Page 1 In requesting the services of GINKGO ENP GNG the client agrees that GINKGO ENP GNG is acting in an advisory capacity and shall not be liable or responsible for any loss, damages or expenses incurred by the client, or any other person or company, resulting from any data or interpretation presented in this report. Introduction to seismic structure interpretation methods and assessment of trap integrity in exploration and baffles to production. for PESA by Dr Peter Boult GINKGO ENPGNG October / November 2009

2 PESA DL 2009 PJ Boult Page 2 Acknowledgements Graham Yielding (Badleys Geoscience) Brett Freeman (Badleys Geoscience) John Walsh (FAG Dublin) Quentin Fisher (Leeds RDR) SANTOS Rodinia Oil Corp (Calgary) Meridian Petroleum (UK) Adelaide Energy Permission to reproduce material in this PESA DL course has been granted by

3 PESA DL 2009 PJ Boult Page 3 Seismic Structure Introduction –Basic fault and fold terminology. –Why do some rocks fold while others fracture? Using 3D folds axial surfaces of to get better 2D maps –Locating axial surfaces in seismic sections –A novel (better?) interpretation workflow for folds in 2D data Lessons - mapping folds Introduction to faults –Why and how do they form –What do they look like Normal faults Reverse fault Strike-slip faults –Relays –Duplexes Exercise Seismic structural interpretation in complex faulted settings –Interpretation workflow recommendations Geometric considerations Seismic processing considerations –Checking your interpretation for geological plausibility Kinematic considerations Exercise Fault seal classification Lithification: – Rock deformation – brittle or ductile? Fault seals in exploration –Primary analysis – juxtaposition –Secondary analysis Fault rock analysis Fault reactivation / top seal failure –Case study Fault seals in production –Methods for incorporating faults into production simulation models –Case study Exercise Calibration Asking the right questions Evidence-based approach to fault seal analysis Validation –Exploration –Production Concluding remarks Workshop 1 Workshop 2

4 PESA DL 2009 PJ Boult Page 4 Seismic Structure in Petroleum Exploration & Production? Structural traps make up 95% of reservoirs Fold and fault mapping is a crucial, though very underrated step in the structural geological workflow in exploration and production. Provides the foundations for all subsequent analysis and modelling

5 PESA DL 2009 PJ Boult Page 5 Why is Fault and Fault Seal Analysis important? Faulting issues impact on >70% of reservoirs Petroleum Exploration –Faults often form one of the main seals for reservoirs –Faults are often invoked as conduits for petroleum migration –Faults may allow the leakage of petroleum through top seals Petroleum Production –Faults can severely retard fluid flow resulting in compartmentalisation –Many companies have had to lower their reserve estimates due to fault-related compartmentalisation –Effective production strategies require understanding of fault behaviour

6 PESA DL 2009 PJ Boult Page 6 Why do some rocks fault while others fold? Substance –Minerals –Porosity Temperature Confining pressure Strain rate Transition from elastic to ductile OR brittle depends on:- Stress Elastic Ductile Brittle Elastic Strain

7 PESA DL 2009 PJ Boult Page 7 In requesting the services of GINKGO ENP GNG the client agrees that GINKGO ENP GNG is acting in an advisory capacity and shall not be liable or responsible for any loss, damages or expenses incurred by the client, or any other person or company, resulting from any data or interpretation presented in this report. Seismic Structure - folds Using 3D folds axial surfaces of to get better 2D maps –Locating axial surfaces in seismic sections –A novel (better?) interpretation workflow for folds in 2D data Lessons - mapping folds

8 PESA DL 2009 PJ Boult Page 8 Folds in seismic sections Folds can be classified based on whether or not the thickness of stratigraphic layers changes over various dip domains OR across axial surfaces T 2 = T 1 γ 1 = γ 2 T 2 > T 1 γ 1 < γ 2 Diagrams from Shaws et al, 2005

9 PESA DL 2009 PJ Boult Page 9 Fold models and processes Flexural or bedding plane slip Ductile T 2 = T 1 γ 1 = γ 2 T 2 > T 1 γ 1 < γ 2 Diagrams from Shaws et al, 2005

10 PESA DL 2009 PJ Boult Page 10 Locating axial surfaces in seismic sections Migration moves dipping reflectors upward and laterally to properly image the fold geometry. Reflections on non-migrated OR UNDERMIGRATED sections do not accurately represent fold shape. However, the axial surfaces can still be interpreted by mapping the truncations of the HORIZONTAL reflections Diagrams from Shaws et al, 2005

11 PESA DL 2009 PJ Boult Page 11 Compression of domino basement blocks – with some strike-slip movement Axial planes propagate from discontinuities of rigid basement. Not a fold just a bend in the seismic Data courtesy of Rodinia Oil Corp / Officer Basin Energy Pty. Ltd.

12 PESA DL 2009 PJ Boult Page 12 But how should we create a map out of data like this? Aliasing problem! Not a fold just a bend in the seismic Data courtesy of Rodinia Oil Corp / Officer Basin Energy Pty. Ltd.

13 PESA DL 2009 PJ Boult Page 13 1200 x 1200 2400 x 2400 Lots of bulls eyes 4800 x 4800 At half the line spacing the gridding bulls eyes have almost gone.

14 PESA DL 2009 PJ Boult Page 14 4800 x 4800 But individual structures bear little resemblance to folds

15 PESA DL 2009 PJ Boult Page 15 So what’s the best way to deal with this situation? Put the fold axes on Not a fold just a bend in the seismic Data courtesy of Rodinia Oil Corp / Officer Basin Energy Pty. Ltd.

16 PESA DL 2009 PJ Boult Page 16 Line fold axial traces up in 3D Correlate fold axes Add horizon axial traces Not a fold just a bend in the seismic Data courtesy of Rodinia Oil Corp / Officer Basin Energy Pty. Ltd.

17 PESA DL 2009 PJ Boult Page 17 Using horizon axial traces as well as 2D horizons give more control when gridding Not a fold just a bend in the seismic Data courtesy of Rodinia Oil Corp / Officer Basin Energy Pty. Ltd.

18 PESA DL 2009 PJ Boult Page 18 Not a fold just a bend in the seismic Data courtesy of Rodinia Oil Corp / Officer Basin Energy Pty. Ltd. Top reservoir horizon

19 PESA DL 2009 PJ Boult Page 19 Map using horizon axial trace control 600 x 300

20 PESA DL 2009 PJ Boult Page 20 600 x 300 45 degs rotation with fold axes – BUT NO Z DATA Just for comparison – using the horizon based fold axial traces – BUT NO Z DATA 1200 x 600 45 degs rotation with fold axes – BUT NO Z DATA 2400 x 1200 45 degs rotation with fold axes – BUT NO Z DATA

21 PESA DL 2009 PJ Boult Page 21 Lessons - mapping folds Correlation should be done in True Perspective 3D –Consider en-echelon nature of folds IN OUTCROP –Line up fold axes and extract horizon-based axial traces Need to grid at the correct scale –Normally ½ 2D line spacing –BUT when fold axis are used, can go down to much smaller grid without bulls eyes. BEST to use a grid cell with its longer dimension along structural grain However, EVEN BETTER to combine above with use of Z data on horizon-based axial traces Z data best created in 3D interpretation package


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