Chestnut Field: Case Study of an Innovative Development

Transcription

1 [Insert Image] Venture Production plc Chestnut Field: Case Study of an Innovative Development Peter Wood & Rachael Moore

2 Outline Overview of the Chestnut field Seismic data and Inversion Depositional Model Static model build Reservoir properties Production and Development Strapline Noble - click Ton and van add Langeveld text testing well 22/2a-16y Slide 2

3 Regional Map Slide 3

4 23 Years of Chestnut in a Nutshell Exploration Appraisal Production 2D Seismic OBC survey Inversion of Streamer data Discovery 1986 Premier 22/2-5 well Found oil in the Nauchlan and TD in the Forties Appraisal Premier then drilled the following appraisal wells 22/2-6 Exploration well, North of Chestnut field found 35 of gas in the Forties. Target was Nauchlan Sands analogous to Chestnut The 22/2a-7 wells 7 well no Nauchlan 7Y wet Nauchlan 7Z oil in the Nauchlan The 22/2a-8 wells 8 well thin wet sand 8Z oil show Appraisal/Production 2001 Brovig-RDS/Amerada Hess drill the horizontal producer 22/2a-11x Three side tracks were required due to borehole instability 22/2a-11x produces 1.1 mmstb from an EWT using the Crystal Ocean Development Venture Production pre-drill the water injector, 22/2a-12 Production 2008 Venture Production drill the 22/2a-16 wells Hummingbird commences production September 2008, now doing on average 13,000 bopd from 2 wells Slide 4

5 Poisson s Ratio Geobody 22/2a-8z 22/2a-11x Slide 5

6 Stratigraphy and Well 22/2-5 S-imp PR Slide 6

7 Rock Properties Nauchlan sands and surrounding mudstones are acoustically similar Cannot use traditional P-wave data to image the Nauchlan sands Acoustic Impedance v Poisson s ratio: colour coded by well and depth. Well 22/2a-7z, 22/2-2a-11x, 22/2-2a-5, 22/2a-7y, 22/2a-8z, 22/2a-7, 22/2a-8, 22/2a-12 Inversion products used to separate sand from shale and oil bearing from water bearing sands Static model was built using a combination of Shear Impedance and Poisson s Ratio to determine the Nauchlan sand from the surrounding mudstones AI PR Cross plot courtesy of Schlumberger RSS Slide 7

8 Rock Properties Nauchlan sands and surrounding mudstones are acoustically similar Cannot use traditional P-wave data to image the Nauchlan sands 22/2-5 Water Substitution Inversion products used to separate sand from shale and oil bearing from water bearing sands Static model was built using a combination of Shear Impedance and Poisson s Ratio to determine the Nauchlan sand from the surrounding mudstones AI PR Slide 8

9 Rock Properties Nauchlan sands and surrounding mudstones are acoustically similar Cannot use traditional P-wave data to image the Nauchlan sands 22/2-5 In Situ Inversion products used to separate sand from shale and oil bearing from water bearing sands Static model was built using a combination of Shear Impedance and Poisson s Ratio to determine the Nauchlan sand from the surrounding mudstones AI PR Slide 9

10 Rock Properties Nauchlan sands and surrounding mudstones are acoustically similar Cannot use traditional P-wave data to image the Nauchlan sands 22/2-5 In Situ Inversion products used to separate sand from shale and oil bearing from water bearing sands Static model was built using a combination of Shear Impedance and Poisson s Ratio to determine the Nauchlan sand from the surrounding mudstones Brine filled Caran Sands: higher AI than oil-bearing Nauchlan Fm AI PR Slide 10

11 22/2a-7 22/2a-7y S-imp PR 22/2a-7z S-imp PR S-imp PR 22/2a-7 well did not encounter any Nauchlan sand, only a Caran injectite Good S-impedance response at the Caran injectite 22/2a-7y well encountered a thin (10ft) oil bearing Nauchlan sand and a thicker water bearing Nauchlan at the main Nauchlan interval S-impedance and Poisson s Ratio response at thin oil bearing Nauchlan could be due to tuning 22/2a-7z well encountered over 100ft of oil bearing Nauchlan Strapline click and add text Poor S-impedance and Poisson s Ration response at the- well, only top Nauchlan has an anomaly Slide 11

12 22/2a-8 22/2a-8z S-imp PR S-imp PR Neither the 22/2a-8 or the 22/2a-8z well encountered Nauchlan sand Slide 12

13 Well 22/2a-11x 22/2a-11x is the horizontal producer drilled by Hess S-imp PR Encountered over 550ft MD of oil bearing Nauchlan sand in 3 intervals Poor S-impedance and Poisson s Ratio associated with the well Only the second sand encountered in the well has an anomaly associated with it Slide 13

14 22/2a-12 22/2a-12 well is the water injector drilled by Venture Encountered 67ft of oil bearing Nauchlan sand Strong S-impedance and Poisson s Ratio anomaly associated with the Nauchlan sands Possible thin injectites just below casing shoe S-imp PR Slide 14

15 Well 22/2a-16z and y The 22/2a-16 well was drilled on S-impedance and Poisson s Ratio anomaly Encountered a total of 78ft of oil bearing Nauchlan sand Side tracked down dip to move away from gas cap S-imp PR Slide 15

16 Seismic Datasets Geco Full stack seismic 1992 streamer data PP full stack acquired for Clyde and Premier WesternGeco TQ3d-4C OBC data PS volume, PZ (vertical component), near stack (5-15), far stack (25-35) compressional PS volume was not corrected to PP time Inversion of WesternGeco data Jason 2000 PS Elastic Impedance of TQ3d-4C data Input PS Volume Output PS-EI volume Odegaard 2002 AVO Inversion and Lithology cube from TQ3d-4C data Input 2 angle stacks from OBC data Outputs Acoustic Impedance and Poisson s Ratio and Lithology Cube SLB 2007 PP-PS AVO inversion of TQ3D-4C data Input PS, near and far stack from OBC data Simultaneously inverted Outputs Acoustic and Shear Impedance and Poisson s Ratio Fugro Multi Client Veritas Long Offset data acquired in Fugro Robertson reprocessed the data in 2003 Near, Mid, Far and Full stack Fugro-Jason Simultaneously inverted 3 angle stacks 2003 Outputs Acoustic and Shear Impedance volumes, Vp/Vs volume Slide 16

17 Example Seismic Line The following seismic lines are from NW to SE intersecting Strapline the 22/2a-7z - click well and and add the text22/2-5 well Slide 17

18 WesternGeco Data 12 5 NW SE NW SE z T. Alba 7z T. Alba T. Nauchlan T. Nauchlan P-wave Data T. Caran T. Caran PP-PS Aligned Data P-wave data does not give best image of the Nauchlan sands Schlumberger RSS aligned WesternGeco s PS volume with the P-wave data PP-PS data gave a better image of Nauchlan sands than normal P-wave data The top Nauchlan pick is from the Fugro S-impedance data Slide 18

19 Schlumberger RSS Inversion Results WesternGeco s near, far and PS data were the inputs into the Schlumberger RSS inversion NW 12 5 SE As predicted from rock property work, P-impedance can not distinguish the Nauchlan sands from the overlying mudstones The PS-impedance data highlighted the Nauchlan sands Poisson s Ratio was able to determine oil from water bearing sands 7z T.Alba T.Nauchlan The top Nauchlan pick is from the Fugro S-impedance data NW SE NW Abs P- Impedance T. Caran SE 7z T.Alba 7z T.Alba T.Nauchlan T.Nauchlan Abs PS-Impedance Strapline T. Caran - click and add text Abs Poisson s Ratio T. Caran Slide 19

20 Fugro s Nelson North Data Purchased the Nelson North seismic and inversion results off the shelf As with the WesternGeco P-wave data, the full stack was difficult to interpret the Nauchlan sands Due to higher frequency input data, the Fugro inversion is higher frequency than Schlumberger RSS inversion data and the anomalies matched the sand thickness in the wells better S-impedance and Poisson s Ratio anomalies had a good match to the well results The top Nauchlan pick is from the Fugro S-impedance data Slide 20

21 Fugro s Nelson North Data NW SE NW SE 7z T.Alba 7z T.Alba T.Nauchlan T.Nauchlan NW Full Stack T. Caran SE NW P-impedance T. Caran SE 7z T.Alba 7z T.Alba T.Nauchlan T.Nauchlan S-impedance Strapline T. Caran - click and add text Poisson s Ratio T. Caran Slide 21

22 Depositional Model Review Alba field is an incised channel at break of slope that has been back filled by high energy turbidites (Millennium Atlas). Chestnut is the same age and distal expression of the same system Oldest Nauchlan sands in Chestnut may result from the Alba field erosive event. Subsequent Chestnut deposition is a similar age to Alba field sand deposition and probably represents mass flow events by-passing Alba Topographic lows in Chestnut area pond turbidites Surlyk et al AAPG Memoir 87 Outflow from Strapline Alba - system click and ponded add text at Chestnut Slide 22

23 Slide 23

24 Slide 24

25 Slide 25

26 Slide 26

27 Sand geometry defined by wells not depositional. 22/2a-7z core Shows sand injection features GR Res Shear Impedance Lithology Indicator Geometry defined by horizontal wells 22/2a-7Z (off section) Poisson s Ratio Fluid Indicator Geocellular Model Modified to tie well data 22/2a-7z (off section) 11x Area Strapline shows - significant click and add remobilisation text Slide 27

28 GR Res Shear Impedance Lithology Indicator Steep dip between 16z and y Poisson s Ratio Fluid Indicator Geocellular Model Modified to tie well data Polygonal Fault Conical Caran Injectites South of Strapline Field - Clearer click and seismic add text response Slide 28

29 Reservoir Properties Reservoir is high quality and relatively homogeneous Only available core is from a remobilised sand Log porosity and character is consistent throughout field Reservoir quality is analagous to other Eocene fields such as Alba and Pilot Permeability of 1 to 2 darcies is supported by well test data Overburden correction to permeability (and porosity) is an unknown Difficult to model reservoir properties sensibly given the depositional context Strapline High Quality - click Reservoir and add text Slide 29

30 Evolution in Field Characterisation Fina/Premier Net Pay 1988 Prospect drilled on a low relief Eocene Mound Targeted a Alba analogue Stratigraphic trap with significant pay south of appraisal wells Appraisal Strapline Wells placed - click on and 2D reflection add text seismic Slide 30

31 Development Overview P2 Well Tie-in Report SEVAN Hummingbird WATER INJ RISER BASE CONTROLS RISER EXISTING PROD RISER BASE 8 FLEXIBLE RISERS (TYP) NEW CHOKE BASE EXISTING CONTROLS UMBILICAL NEW CHOKE BASE NEW P2, 22/2a -16 PRODUCTION TREE NEW UMBILICAL 1.0KM TRENCHED EXISTING W.I TREE, 22/2a-12 EXISTING 8 W.I FLEXIBLE (2320m) CHESTNUT P2 FIELD LAYOUT NEW 6 PRODUCTION LINE WITH 2 GL PIGGYBACKED (3.4km) TRENCHED & BACKFILLED EXISTING PROD WELL 22/2a-11 Sevan Hummingbird Cylindrical FPSO First deployment in North Sea (2 nd Worldwide) 250,000 bbl capacity Short field life and re-deployment strategy 3 Subsea wells tied back 2 producers 1 Injector Excellent Facilities and Reservoir Performance Slide 31

32 Field Performance /2a-11x Extended well test (to Crystal Ocean Vessel) produced 1.1 mmstb with increasing water cut which stabilised Good reservoir performance Poor uptime Current Field performance is better then expected Field had partially re-equilibrated, pressure had recovered to 30 psi off virgin pressure 22/2a-11x performance was equivalent to that seen at beginning of EWT Water Injection was delayed Voidage replacement, but water injection capacity constrained Challenging to initiate injection due to relative permeability Stable injection rates > 20,000 bbls Producing GOR has been relatively stable Differs from EWT behaviour 22/2a-16Y (2 nd producer) now onstream 2008/9 Cumulative Production has exceeded initial EWT Reservoir and Facilities performance in excess of expectations Sevan Hummingbird uptime has been excellent Slide 32

33 Chestnut field production performance Tanker Offloads P2 Tie in P2 Onstream Slide 33

34 Summary Chestnut field onstream 22 years after first discovery Seismic technology has transformed the understanding of Chestnut Eocene Mound to Middle Eocene stratigraphically trapped, turbidite sourced, partially remobilised sand reservoir Original structural definition of field area and subsequent appraisal wells would have benefited from seismic improvements Excellent example of AVO response Chestnut is a geologically complex field and a deliberate development of a sand injectite Sevan Hummingbird FPSO is an innovative solution that is performing well Future Seismic Technology: Further AVO inversion, Stochastic inversion, assess potential of 4D More wells Surveillance Slide 34

35 Thank you Colleagues: Sam Murphy, Tatiana Kiyrushkina, Andy Alexander, Paul Herrington, Nigel MacLean, and Mike Travis Partners: Contractors: Slide 35