(Report of the workshop to be published in First Break, February 2014)

Transcription

1 BASIN-MARGIN WEDGE EXPLORATION PLAYS LISBON, November 2013 (Report of the workshop to be published in First Break, February 2014) The European Association of Geoscientists and Engineers (EAGE) and the American Association of Petroleum Geologists (AAPG) continue to reinforce their cooperation by developing annual joint workshops. About sixty professionals attended the first workshop dedicated to Basin-Margin Wedge Exploration Plays, held in Lisbon in last November. The workshop was an opportunity for authors to present papers illustrating successful case studies and possible potential provinces particularly within the Atlantic and Eastern Africa margins. Open discussions during oral sessions and a «break-out session» allowed participants to share experience and knowledge and discuss the strengths and failings of concepts which have led, in recent years, to several significant discoveries in the South Atlantic Margins. Concerning the basin setting, it has been concluded the geodynamic context is not a key determinant for the success of the play. However, the topography of the margin is a critical element and has to be considered at the present stage but also evaluated during the deposition of the sediments. The regional source to sink model of the margin has to be understood in 4D with the help of global reconstructions and knowledge of the hinterland of the margin. For the charge risk analysis, analyses of migration pathways and connectivity processes within the sedimentary sequence are critical for stratigraphic traps bounded by bottom and top seals. Recent charge is a positive criteria and long residence time is considered more risky due to possible leakage across ineffective seals or biodegradation if the reservoir is maintained at sufficiently low temperatures. As for conventional plays in frontier areas, seabed coring and heat flow reconnaissance surveys are key inputs for calibrating basin models. The location of the continental-oceanic boundary is a key input in the basin modelling. From the reservoir point of view, the understanding of turbidite clastics is considered fair to good but turbidite carbonates remain unpredictable and an area for additional research. The main gap in our knowledge of Basin-Margin Wedge reservoir character is dealing with continuity/connectivity of reservoirs. Diagenetic history and compartimentalization of turbidite bodies pose significant challenges for justifying exploration/appraisal wells and optimizing development drilling programmes. The value of source to sink academic programmes to predict influx and qualities of sediments is recognized and knowledge sharing with teams working on unconventional resources is recommended for better predicting the characteristics of external and internal seals. Confidence in efficiency of trapping is higher if the trap is a combination of pinch out and fault geometry. By-pass existence and sand/shale content have an impact on the critical issue of the pinch out model. BMW play is still considered as a high risk exploration. 3D seismic acquisition is mandatory, even if 2D can be used to screen the basin. Stratigraphic traps are unique, so an evaluation by analogy should be applied with caution. A prospect evaluation based only on geometry and geology will provide a very low probability of success. The probability may be improved by integration of additional data such as seismic attributes analyses particularly if some calibrations are available close to the prospective area, seismic processing, specific non seismic tools, regional petroleum habitat review and seabed reconnaissance surveys. Jean-Jacques Jarrige On behalf of the Organizing Committee : J.J.Jarrige (formertotal), S. Harker (Circle Oil), H. Ligtenberg (Shell), D. Blanchard (Energy XXI), C. Duguid (Tullow Oil), N. Frewin (BG Group). Annex 1 : aim and final programme of the workshop Annex 2 : highlights of the «break-out session

2 Aim and Programme of the Workshop Basin-Margin Wedge Exploration Plays - Lisbon, November 2013 Aim Build an improved understanding of the Basin Margin Wedge Plays: strengths and failings of such a concept risks associated with each component of the petroleum system. Identify gaps that should be adressed by improved technology and studies by research institutes in collaboration with the industry Final Programme Thursday morning 09:00 Basin - Margin Wedge Play, A Game Changer for Exploration? J.J. Jarrige*(former Total), C. Duguid (Tullow Oil) & H. Ligtenberg (Shell) 09:45 TS2P - The Transform Source to Sink Project - 3D Modeling of the Long Term Stratigraphic Evolution of a Transform Margin D. Rouby* (Géosciences Environment Toulouse), D. Chardon (Géosciences Environment Toulouse), F. Guillocheau (Géosciences Rennes) & C. Robin (Géosciences Rennes) 10:30 Break 11:00 Structural Styles of the Equatorial Brazilian Margin L.H. Houston* (CGG) 11:45 Structuration and Subsidence of the French Guyana Hyper-oblique Margin F. Sapin (Total), J.C. Ringenbach (Total), M. Dall'Asta (Total), M. Lahmi (Total), H. Rojas (Total), M. Davaux (Université Pierre et Marie Curie) & G. Baudot* (Total) 12:30 Lunch Thursday afternoon 14:00 Fundamental Building Blocks of Extensional Margin Architecture - Implications for the Basin Margin Wedge Play L. Price* (ExxonMobil Exploration Company), G. Karner (ExxonMobil Upstream Research Company), C. Johnson (ExxonMobil Upstream Research Company) & B. Renik (ExxonMobil Exploration Company) 14:45 Rift Segmentation and Domain Architecture of Lofoten-Vesterålen margin (LVM), Offshore Norway R. Tasrianto (University of Stavanger), A. Escalona* (University of Stavanger), M.J. Young (ConocoPhillips Norge), N.T. Grant (ConocoPhillips UK) & C.D. Hirning (ConocoPhillips Norge) 15:30 Break 16:00 Abrupt Margins - Dawn of a New Exploration Era P. Renaud* (Total) 16:45 17:45 Break-out Session part 1 18:30 Departure to Dinner Friday morning 09:00 A Comparison of Four Fields in the Ghanaian Late Cretaceous Wedge Play R. Mecklenburgh* (Tullow Oil plc) 09:45 Reservoir Characteristics of Four Key Turbidite Depositional Facies J.R. Dribus* (Schlumberger) 10:30 Break

3 11:00 A Multidata Integration to Understand the Prospectivity of the Barreirinhas Basin J. Martin* (TGS), C. O'Reilly (TGS) & I. Deighton (TGS) 11:45 Passive Margin Play and Prospect Evaluation Using Regional Depth Seismic and Inversion of Seismic Processing Velocities J.H. Hubred* (Aker Geo AS) & I. Meisingset (Aker Geo AS) 12:30 Lunch Friday afternoon 14:00 Broadband seismic impact on seismic interprétation for Basin-Margin Wedge Plays G. Duval (CGG-Veritas) 14:45 Basin-Margin Wedge Play perspectives within the western and eastern African continental margins M. Francis (Schlumberger) 15:30 Coffee break 15:40 Wrap Up: conclusion of break-out session groups 17:00 End of meeting

4 Highlights of the break-out session groups Participants of the workshop were split in four groups and the objective of break-out was to identify: weaknesses in our current understanding of these plays. what can be done to improve. Group Basin Setting Range of geodynamic settings? Not restrictive Possible in all types of margin Topography Relationship to a source of sand, paleodrainage Trap component of onlap (base lap) In a passive margin the basin floor fan is tilted towards the basin. But this topography is mainly formed long after deposition, as a consequence of subsidence. During deposition the basin looked very different. More like this. The question of topography is actually two questions, how it was during deposition, and how it is now, when we have a trap. Reconstructions are useful Scientific priorities Heat flow, maturity and migration dynamics Confidence as to level of understanding Reliant on seismic, resolution limited Will the BMW play develop into a strong global theme? Maybe Groups Reservoir Group 1 : How well do we understand the reservoir character? For turbidite clastics: fair to good understanding For turbidite carbonates: poor to fair understanding Issues include diagenesis and no AVO application for risk mgt Gaps in our knowledge of BMW reservoir character? Compartmentalization: continuity and connectivity Proper seismic illumination: stratigraphy is often below visibility Good on external geometry, poor on internal architecture Texture: what grain size is too fine for commercial recovery Thin bed analysis: clay content, clay effect, lamination analysis Often lacking core

5 Diagenesis: mechanical (compaction), chemical (cementation) clay mineral transformation effects Value of a sediment provenance research consortium? An industry consortium on provenance is a good idea Since most turbidites are re-sedimented from delta sources during low stands, study should include on composition of deltas to determine lithologies and texture (grain size) available to turbidites. Should also consider paleo-climate and availability of water for erosion Effect of provenance distance on sediment maturity: reservoir quality Provenance for mud members important as well: ductile vs brittle shales Role of Diagenesis: what is important? Clastic and carbonate diagenesis differences Diagenesis history in rift systems with active volcanism Timing of diagenesis and catagenesis (hc transformation) Temperature and heat flow Mechanical compaction and unloading history Chemical cementation Feldspar and mica alteration Formation of glauconite. Compartmentalization issues? Structural segmentation into separate flow units by faulting Stratigraphic architecture Shingling between lobes Partitioning within lobes Dissection by mud-filled channels Threshold size of reservoirs to justify well drill and complete cost Compartmentalization impact on ultimate recovery What tools should be developed or improved? Higher resolution seismic acquisition: full azimuth to ultra azimuth Improved seismic processing and re-processing More accurate velocity modeling Improved depth conversion Higher resolution resistivity image log for both water- and oil-based muds For improved thin bed analysis For improved stratigraphy and depositional environment interpretation Develop CSEM DHI tool: high resolution 3-D resistivity mapping Develop AVO/DHI tool for carbonates Improved Sequence Stratigraphic Analysis including sea floor effect More Source to Sink studies to predict sediment influx in all global basins Group 2 High confidence in CONCEPTUAL grasp of reservoir character. Sediment provenance, processes on abrupt margins, relative paucity of well data. Well data is the only proof of concept, seismic is a great tool BUT Academic work on provenance is regarded as of high value. Core objectives; keep it simple, clearly recognize limitations, source lithology, processes & sorting... Improving understanding of Diagenesis. Cross-pollination from unconventional? Carbonates remain unpredictable. Stratigraphic Compartmentalization is significant challenge; are we missing analogues, (water depth)? Is Jubilee as good as it gets?! Higher resolution seismic. More core data please.

6 Group Charge The pilot check list : AVO? Yes or no Migration pathways and connectivity of the petroleum system Location of the kitchen yield, timing quality of SR Leak point? Dynamic system? Recent charge? Basin modelling Charging mechanism, pressure regime, Seismic velocity, pressure regime Data acquisition sea bed geochemistry and heat flow measurement 3D mandatory Several wells to drill before success? Group Trapping Trapping (but not only -) Confidence in trapping: mixed not convinced. fault or pinch out required (one, the other or both ) For pure strat traps pinch out model (lateral or axial), by pass existence and size (single event vs. Multiple events impact on potential size) and sand/shale content easier when mixed (faults = big size?) Uniqueness of strat traps (field size from 1MMBoe to 6 Bboe, nugget?) and RISKY if just geometry is defined core risk ~10% Pg > if presence of Class III AVO, hydrocarbon flags, updip field, seeps BUT dangerous in unproven basin Globally good at predicting and finding sands BUT poor at predicting reservoir quality and HC presence 2D can be used to screen basin but 3D (even BroadBand) required to define and derisk prospect (subtle geometry vs. Size need to find a compromise) Long residence time should be considered a risk (biodegradation, later leakage ), more recent charge is preferred but not essential