The Rosebank Discovery. A new play type in intra basalt reservoirs of the North Atlantic volcanic province. DEVEX AECC 13 May 2009

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1 The Rosebank Discovery A new play type in intra basalt reservoirs of the North Atlantic volcanic province DEVEX AECC 13 May 2009 Louise Duncan, Dag Helland Hansen, Cliona Dennehy Chevron 2009 DOC ID

2 Outline Introduction Regional geology and play concept The Rosebank Discovery Appraisal Program and Results Development studies: Use of Analogues Challenges associated with Volcanic Plays Conclusions & Acknowledgements Chevron 2009 DOC ID 2

3 Introduction Rosebank Lochnagar Location Structural elements map restored back to break up of N Atlantic (Paleogene) 3

4 Geologic Setting Rosebank & Greater Rosebank Area Easterly advancing volcanic system of extrusive basalts & volcaniclastics. Contemporaneous Flett Delta system to the SE prograding in a N/NW direction Confluence of volcanic and sedimentary interaction Chevron 2009 DOC ID 4

5 1s TWT Greater Rosebank Area The Play Concept W E Inversion anticlines Seabed 2s Flett Fm. Late Paleocene/ Early Eocene 3s Volcanic Complex 4s Pre Tertiary Base Tertiary 5s Inversion phases Various pulses throughout Cenozoic Rift phase(s) Corona Ridge Pre Rift sediments 5 ~10km

6 NW Rosebank The prospect in 2001 SE Exploration Target Volcanics Reservoir Hydrocarbon Target 6

7 Rosebank Lochnagar The Discovery in /27 1Z Rosebank North Rosebank 213/27-1Z Rosebank Discovery 350 Flett Fm. Lochnagar Pre Tertiary NW SE 7

8 Proven Petroleum Plays Intra and Sub Volcanic Reservoirs Volcaniclastics Basalt - lavaflow Fluvial / Marginal marine Risk Elements Reservoir: Intra & Sub basalt: Siliciclastic fluvial and shallow marine reservoir sandstones Trap: 4 way inversion structure Source: Pre Tertiary Source Rock Seal: Volcanic rocks & shales Basalt - lavaflow Fluvial Basalt - lavaflow Fluvial Marginal Marine Volcaniclastics Basalt Flett Fm, Paleocene Eocene, Intra volcanic Paleocene Cretaceous, Sub volcanic Lochnagar, Rona sst, Jurassic 8

9 Appraisal Drilling Top Colsay 1 Depth Structure 3 well appraisal campaign carried out in 2006/2007 aimed at: Defining field commerciality Reducing key reservoir uncertainties Data Acquired: Log data, SWC & whole core Production Data: 1DST Pressure Data: MDT Seismic Data: VSP Extensive data acquisition programme provided a comprehensive dataset for field delineation & aid future development decisions 9

10 Appraisal program DST Results Press release: Aberdeen, Scotland, 17th July 2007 Chevron North Sea Limited announced today the successful conclusion of a production test of the Rosebank appraisal well 205/1 1, West of Shetland. The Rosebank discovery is in approximately 3,700 feet of water some 100 miles north west of the Shetland Islands. Rosebank partners are Chevron as operator, Statoil, OMV and DONG Energy. During the production test, the well flowed at choked rates of 6,000 barrels of oil per day of good quality light oil (37 o API). 10

11 Rosebank Correlation Panel TVDss Upper Volcanics Colsay 1 Colsay 3 Lower Volcanics S 11 N

12 Appraisal program Results Summary Reservoir Intra and sub volcanic siliciclastic sandstone reservoir Fluvial shallow marine environment Varying thickness, NTG and reservoir quality Medium porosities with very high permeabilities Fluids Thin gas cap encountered Oil downdip in all zones ~37 o API oil Pressure Independent reservoirs within different fluid contacts Seismic data VSP Re processing and calibration of seismic Reservoir characterization with seismic 12

13 Development Challenges Resource Size Benchmark reservoir properties e.g. NTG, reservoir architecture etc against appropriate analogues Outcrop Analogues Predicting away from well control Seismic Imaging challenging in intra basalt reservoirs Multiple attenuation and resolution challenges Attempts to delineate Sand Fairways Uncertainty Management Size of Accumulation Reservoir Quality and productivity 13

14 Analogs Sites of Study Field Scale Rosebank West Coast Greenland East Coast Greenland West of Scotland Isle of Skye Mull Iceland Grand Canyon 14

15 Analogue Studies East Coast Greenland Fluvial shallow marine sandstone Volcanics Sub basalt fluvial / marine Sandstone 15

16 Analogue Studies Iceland Lava flow Forms cliff line Iceland Lava topography Inflation Structures Iceland Present day processes Lava flow Braided river deposits gradually filling in surface and burying lava flow Fluvial channel feeding a shoreface sand 16

17 Seismic Imaging 3D 1998, Pre drilling 3D 2007, Post drilling Intra and Sub volcanic imaging, a continuous improvement process Various seismic acquisition and processing techniques have been tested: focus on frequency enhancement, velocity estimation and multiple attenuation Currently assessing how valuable the seismic is in delineating sand fairways for development planning 17

18 Seismic Imaging Deriving the geology from seismic 2 nd -well 1 st -well Discovery 3 rd -well S Soft sediment : shale/sand Hard rocks : Volcanics N Seismic Coloured Inversion Structure interpretation Paleo topography and faults Amplitudes and seismic stratigraphy Paleo environment Reservoir quality maps 18

19 Development Challenges Uncertainty Management Size of HC accumulation Reservoir extent Reservoir thickness Sealing Capacity Quality of Reservoir Sand poro perm Reservoir architecture Sealing faults Volcanic baffles / barriers to flow Mineral precipitation along fault planes and in reservoir? Reservoir architecture / sand distribution dominated by drainage systems and lavaflow barriers 5m Intrusives cutting through reservoir Basalt plug / reservoir baffle 19

20 Reservoir Characterisation Volcanoclastic Prodelta Shale Build Structural Framework grids Channel Axis Mouth Bar Model Facies Channel Margin Petrophysical Modeling OOIP Uncertainty Analysis & Calculate Volumes Select Models for simulation Chevron 2009 DOC ID QC / Peer Review 20

21 Conclusions Rosebank discovery & appraisal programme demonstrates Working intra volcanic and sub basalt plays Siliciclastic sands Seal in volcanic clays High permeability and productivity Unconventional challenges and uncertainties Volcanic petroleum geology systems > Analogs for improved understanding Seismic imaging challenges The Rosebank discovery opens up new opportunities for prospectivity along the North Atlantic Volcanic Margin 21

22 Acknowledgments Rosebank Partners: Chevron Dong Energy OMV StatoilHydro Chevron 2009 DOC ID