Time lapse Seismic, a journey Trough 20 years of seismic challenges

Transcription

1 Time lapse Seismic, a journey Trough 20 years of seismic challenges Cyril Saint-Andre*, Benoit Blanco, Yann Montico, Patrick Charron, Emmanuelle Brechet Total SA Time-lapse seismic data have now proved to be very valuable for monitoring production and fluid injection in reservoirs. Overcoming the 4D acquisition and processing challenges in both quality and timing is still a key task for operators as 4D data deliverables must conform to challenging production and development deadlines. This paper will review several case studies showing examples of 4D experiments with a wide range of technical difficulties and contexts. The case study fields are characterized by very different geological settings and development maturities We shall start in the early 1990s with a naive 2D-on-2D trial from the North sea, and continue with a look at the precise and repeated monitoring of water injection and production for reservoir management and field development in the Gulf of Guinea turbidite reservoirs a decade later. Following these early successes we will describe the actions taken to industrialize time lapse processing and thus drastically reduce the processing turnaround and costs. In order to cope with the increase in processing challenges we developed efficient and innovative QCs that allow faster and more straightforward assessment of the 4D signal quality after each processing step. The next step up in difficulty came with the use of 4D technology to monitor production phenomena in carbonates fields. Time-lapse seismic has been acquired on a field in Eastern Asia affected by significant subsidence effects which significantly complexify the 4D processing workflow. However the rise in the Gas Water Contact (GWC) was clearly observed, which allowed us to anticipate future water breakthroughs in the field. More recently, Time lapse processing techniques applied to the overburden have enabled us to characterize very subtle geomechanical effects above heavily depleted reservoirs. Looking ahead, we are now aiming to routinely apply 4D techniques in Middle east carbonate fields suffering from heavy multiple contamination; Land 4D will offer another set of challenges, the first of which being to achieve acceptable acquisition repeatability, where using permanent sources and receivers may be a major part of the solution. Last but not least 4D in Sub Salt contexts adds imaging challenges to the difficulties of preserving the reliable and repeatable amplitudes needed for quantitative time lapse results assessment.

2 p.1 Time lapse Seismic, a Journey Trough 20 Years of Seismic Challenges Cyril Saint-Andre*, Benoit Blanco, Yann Montico, Patrick Charron, Emmanuelle Brechet Total SA

3 OUTLINE p.2 The «early days» of 4D s Toward 4D Workflow Optimization Focus on dedicated QCs The «carbonate» Challenges The overburden Bonus The Leaps forward and Beyond!

4 OUTLINE p.3 The «early days» of 4D Toward 4D Workflow Optimization Focus on dedicated QCs The «carbonate» Challenges The overburden Bonus The Leaps forward

5 4D: What is it for? 4D = Images / Pictures of a reservoir taken at different Period of time 4D gives you the unique spatial monitoring image It contributes to the dynamic knowledge of the field: > Fluid communications > Reservoir heterogeneities (geological & dynamic barriers) > Fault sealing behaviour > Water/gas injection efficiency > GWC or WOC rise ups > Production efficiency: drained versus undrained areas > Monitoring of pressure and/or geomechanical effect p.4 Gas ex-solution linked to depletion Water injection in oil pool Aquifer rise

6 What is 4D?: The African Sunset 4D Experiment p.5 BASE MONITOR

7 What is 4D?: The Sunset 4D Experiment p.6 «4D» is a term defining successive 3D experiments The quality of a 4D result is strictly related to the quality of the baseline survey As any other physical measure, 4D is subject to errors, carried by every 3D contributor The way we restitute data is at least as important as how we acquire it A 4D effect, in general, generates a number changes in the surrounding environment

8 p.7 4D is used in a field life in a short and in a long term processus Short term using a fast track: Long term using a full processing: 3 months after 4D acquisition 6 months/1 year after 4D acquisition 4D is used in a qualitative way 4D is used in a quantitative way 7 Objectives: Field developement Positionning infill wells Reservoir management Understanding of global communications and dynamic behaviours of the field Processing & post processing: Fast track full offset cube Warping 4D Interpretation: Boundaries &/or geobodies on dv/v attributes and/or amplitude cubes Proximity between 4D processing teams and warping teams enhanced the speedness of 4D - Références, date, lieu inversion cubes delivery Objectives: Integration of 4D interpretation inside reservoirs models Imporovement of reservoir model to be more predictive by changing AE, facies, NTG, permeabilities, fault transmissibilities to perform better HM Processing & post processing: Full processing with substacks Warping 4D inversion 4D Interpretation & integration: Geobodies on dv/v and/or dip/ip Upscaling inside reservoir models Comparison with geological models, eclipse simulations, seismic modellings Update of AE, facies, NTG, K, Fmult

9 OUTLINE p.8 The «early days» of 4D Toward 4D Workflow Optimization Focus on dedicated QCs The «carbonate» Challenges The overburden Bonus The Leaps forward

10 4D processing Dedicated team Objective & Motivation p.9 OBJECTIVES Minimize timing for delivery of final 4D volumes after the end of acquisition; No more Fast-track for repeated monitors! (2 months for processing turnaround) Cope with sharply increasing 4D activity (Nb of projects / Acquisition cycle) Reduce costs 4D activity in TOTAL Ofon MEANS Long term contract => anticipation Fixed Processing sequence Process incremental monitor only! Secure same resources for repeats Synergies with Development team for 4D interpretation & integration with reservoir monitoring and models operated Done or decided In progress or under examination Non operated Done or decided In progress or under examination 9

11 4D: Girassol Example / History p => Increasing turnaround 2008 => Increasing complexity

12 Getting more out of 4D by Processing Turnaround reduction p.11 4D Processing Turnaround Reduction by 4D Single Monitor Processing (SMP) Innovative Solutions Lean, stable and standardized single monitor processing sequence No fast -track route; only full integrity dataset delivered within the same turnaround Testing phase limitation to the strict necessary More time devoluted to QC s

13 4D stabilized «lean» processing sequences p.12 WHAT : Do not reprocess all vintages for each new monitor Reduce lost time in procurement phase Capitalize on previous 4D experiences Replace FT & Full scenario by optimized Full processing only 2 months turnaround target for new monitor BENEFITS : Mimimize testing Take full advantage or Vintages already processed (Base and Mx) Implement automated QCs X X X Strip down costs $ $ $ $ Turnaround Reduction (RTT)

14 Getting more out of 4D by Processing Turnaround reduction p.13 Preserving 4D signal No Compromise on quality Lean & Frozen sequence per project Seamless production ( // Milestones) Capitalize on previous 4D experiences

15 OUTLINE p.14 The «early days» of 4D Toward 4D Workflow Optimization Focus on dedicated QCs The «carbonate» Challenges The overburden Bonus The Leaps forward

16 4D R&D interaction & innovative QCs p.16 Innovative QCs SDR: Signal Distortion Ratio, NCCP, Noise Characterization Cross Plot RPTSC, Relative Phase Time Shift Cube NRMS Band Pass SDR vs NRMS cross plot.

17 Dedicated proprietary QC Integration in SISMAGE p.17

18 OUTLINE p.18 The «early days» of 4D Toward 4D Workflow Optimization Focus on dedicated QCs The «carbonate» Challenges The overburden Bonus The Leaps forward

19 Time lapse Seismic, a Journey Trough 20 Years of Seismic Challenges STORY OF THE DAY comes from yesterday yesterday First 3D development acquisition performed in 1993 followed by a second one in p Start of production of Gas Field Geological context: Miocene Carbonate Platform 1998 first gas Production with 13 gas producer wells 2012 Today 2012 Acquisition of the new 3D acquisition first 4D Monitor Processing, Interpretation and analysis of the 4D

20 MAIN Challenges p.20 2 inhomogeneous vintages Base = two different old seismic from 1993 & 1995 Monitor = modern New Acquisition 2012 Subsidence observed at Water Bottom It introduces a time shift and make 4D processing very tricky Challenge for both acquisition & processing Challenge for both processing & interpretation Base 1995 Base 1993 Production platform area during monitor acquisition Rig area during base acquisition Monitor 2012 Subsidence Area

21 Attenuation of the 4D footprint with subsidence phenomena p.21 SUBSIDENCE Subsidence is an aging effect that must be preserved Subsidence is a production effect that must be preserved Overburden Reservoir

22 -6ms Time lapse Seismic, a Journey Trough 20 Years of Seismic Challenges 4D time & amplitude de-striping (base only) 0 +6ms Raw Time Shift Map Subsidence Map New full global matching for Base merge (93 & 95) 3D time de-stripping One per vintage (new one for Base) Global Matching Pseudo surface consistent residual time statics 4D Binning 12.5x25m 4D time & amplitude destripping applied on Base (to fit Monitor) 3D regularization 12.5x25m Inline interpolation 12.5x12.5m 3D Kirchhoff Pre Stack Time Migration using new PSTM velocity field RMO correction Angle mute & stacking Residual Global Matching Local Matching p.23 4D Full Processing Raw Time Shift map is smoothed (1250 x 1250m) Low Frequency = Subsidence map

23 4D time & amplitude de-striping (base only) After 4D De-striping application De-striped Time Shift Map Time Shift Map No Subsidence New full global matching for Base merge (93 & 95) 3D time de-stripping One per vintage (new one for Base) Global Matching Pseudo surface consistent residual time statics 4D Binning 12.5x25m 4D time & amplitude destripping applied on Base (to fit Monitor) 3D regularization 12.5x25m Inline interpolation 12.5x12.5m 3D Kirchhoff Pre Stack Time Migration using new PSTM velocity field RMO correction Angle mute & stacking Residual Global Matching Local Matching p.24 4D Full Processing Good de-striping & Subsidence preserved

24 Efficient acquisition + Processing led to relevant reservoir and overburden information 4D interpretation highlights some significant differences compared to reservoir simulation. Reservoir model can be improved to optimize the production. Subsidence related to Reservoir Carbonates Compaction can be assessed Time lapse Seismic, a Journey Trough 20 Years of Seismic Challenges INTERPRETATION p m dv/v 4D GWC (2012) Original GWC Simulated GWC (2012) Porosity & Permeability overestimated in Reservoir model Optimistic Res. Mod. Porosity & Permeability under-estimated in Reservoir model GWC: 4D vs. Simulated Pessimistic Res. Mod. 30m

25 Vintage D Processing of 1996 data p.26 26

26 2014 4D Processing of 1996 data p.27 Improved SNR Less multiples More continuity. 27

27 Time Shift Panorama Reservoir Mishrif-SB6 p Denoise 2. Shallow Water Demultiple 3. Cold Water Statics 4. 4D Destriping 5. 4D Binning & Reg 6. PreSTM 4D SRME + Undershoot Matching 7. Final Mute + Global Matching Fast Track PoSTM + 4D SRME 29

28 NRMS Panorama Reservoir Mishrif-SB6 p Denoise 2. Shallow Water Demultiple 3. Cold Water Statics 4. 4D Destriping 5. 4D Binning & Reg 6. PreSTM 4D SRME + Undershoot Matching 7. Final Mute + Global Matching Fast Track PoSTM + 4D SRME 30

29 p.31 4D Destriping methodology allows to reveal the 4D signal 4D SRME allows to apply a SRME without any 4D artefacts Demultiple of this 4D project is better than vintage 3D processing Time Shift 4D Signal is below 1ms in the overburden / 2ms in the reservoir About 60 segy output for internal 4D QCs 11% NRMS at reservoir level ;

30 OUTLINE p.32 The «early days» of 4D Toward 4D Workflow Optimization Focus on dedicated QCs The «carbonate» Challenges The overburden Bonus The Leaps forward

31 Dalia M14 overburden 4D PROCESSING p.33 4D Destriping theory, used to reveal a potential 4D signal in the overburden.

32 Dalia M14 overburden 4D PROCESSING p.34 Water bottom difference converted in depth. The subsidence is very slight but appears clear on this particularly repeatable 4D seismic Time Shift section over the producing fields allows seeing the slight arching effect. The deghosted section is visible by transparency.

33 Results in sections: 4D qc attributes (xl 3582) p.35 Overall increase in 4D signature from M12 to M14, as expected.

34 OUTLINE p.36 The «early days» of 4D Toward 4D Workflow Optimization Focus on dedicated QCs The «carbonate» Challenges The overburden Bonus The Leaps forward

35 Conclusions p.37 4D processing is not only a good combination of good 3D processing 4D processing require accuracy to match Base and Monitor Cross functionality / Integration with the research team, reservoir interpreters and experts. Knowledge building and development of dedicated innovative workflows. Internal development of innovative QCs. Cost / Workload / Procurement effort reduction

36 The Leaps forward p.38 Looking ahead, we are now aiming to routinely apply 4D techniques in carbonate fields suffering from heavy multiple contamination Land 4D will offer another set of challenges, the first of which being to achieve acceptable acquisition repeatability Last but not least 4D in Sub Salt contexts adds imaging challenges to the difficulties of preserving the reliable and repeatable amplitudes needed for quantitative time lapse results assessment.

37 p.39 THANK YOU! Cyril Saint-Andre*, Benoit Blanco, Yann Montico, Patrick Charron, Emmanuelle Brechet Total SA