2D seismic analysis of Chalk play in the northern Dutch offshore
From the sixties in the previous century various plays in the Dutch offshore have been intensively studied. Though the oil- and gas industry assesses the area as ‘mature’, new discoveries are still made in new and old plays. One of these plays is the Chalk Play. In the Dutch offshore only two fields have been verified up to now: the F2-Hanze field (1996) and only recently the F17-Rembrandt field (2011). Both fields relate to the same petroleum-geological elements: fractured Ekofisk Formation reservoir on top of a salt body, supplied by hydrocarbons from Late Jurassic Posidonia source rock. In 2014 EBN performed a regional study on the Chalk play in the northern Dutch offshore. The study was mainly based on recently shot 3D-seismic data in the D-, E- and F-quadrants. Results showed that the Chalk play is underexplored in this area and hydrocarbon potential is still present. Other parties that are interested in the northern offshore may perform seismic studies on the available - expensive - 3D-seismic data or else may make use of various public 2D-seismic surveys. AmsterdamPG applied advanced reprocessing algorithms that improved the quality of these 2D-seismic surveys significantly. Based on this reprocessed seismic dataset a regional seismic interpretation has been performed, focussing on the reservoir of the Chalk play. Based on this interpretation 37 anticlinal leads have been identified in the study area (>5 km2), ranging from steep Hanze-style structures, to relative flat anticlines. Additionally a geological study has been executed, showing the potential and risks of the play. Combined, the geological study, reprocessed seismic dataset and the interpretation give a unique insight in the Chalk Play potential in this area, which may stimulate interested parties to deploy (further) activities in this area.
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2D seismic analysis of Chalk play in the northern Dutch offshore
- 1. 2D Seismic analysis of Chalk play potential in the upper D, E and F-quadrants Dick Stegers, Msc Q2-2016
- 2. Chalk Economics • Exploration, like any other business, has one major goal: making profit 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 110.00 120.00 1/10 31/12 1/4 2/7 1/10 31/12 2/4 2/7 2/10 1/1 1/4 2/7 1/10 1/1 $/BBL Oil costs $/BBL Brent Crude Light Crude
- 3. Chalk Economics • Exploration, like any other business, has one major goal: making profit 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 110.00 120.00 1/10 31/12 1/4 2/7 1/10 31/12 2/4 2/7 2/10 1/1 1/4 2/7 1/10 1/1 $/BBL Oil costs $/BBL Brent Crude Light Crude
- 4. Chalk Economics • Exploration, like any other business, has one major goal: making profit 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 110.00 120.00 1/10 31/12 1/4 2/7 1/10 31/12 2/4 2/7 2/10 1/1 1/4 2/7 1/10 1/1 $/BBL Oil costs $/BBL Brent Crude Light Crude y = 3E-14x6 - 7E-09x5 + 0.0008x4 - 43.077x3 + 1E+06x2 - 2E+10x + 2E+14 R² = 0.9606
- 5. Chalk Background Discovery F17-NE 4-12-’12: Wintershall announces an oil discovery in exploration licence F17a in the Dutch North Sea. Exploration well F17-10 found a Late Cretaceous Chalk reservoir of good quality containing crude oil. Preliminary resource estimates indicate a potential of at least 30 million barrels recoverable oil with a more than significant upside. EBN study 2013: • ‘Chalk in the northern Dutch offshore is underexplored’ • Non-exclusive 3D-seismic in DEF-quadrants shot in 2011/2012 with Fugro F17
- 6. Chalk Study Area • Focus on open acreage • Regional 2D dataset • Eleven different surveys • 80’s, 90’s, 00’s • ~350 lines • Area of ~6.500 km2 F02 Hanze
- 7. Chalk Chalk study Reprocessing seismic data Defining and classifying leads Re-interpretation Welltops Geological study Interpreting seismic data Grids & thickness maps Analysis analogues HC analysis well documents
- 8. Chalk Seismic reprocessing: Vintage W E Reprocessed seismic data • Improved signal-to-noise ratio • Improved fault recognition • Narrowed steep features • Widened rimsynclines • Improved reflection continuation
- 9. Chalk Seismic reprocessing: Reprocessed W E CK SL ZE KN N Reprocessed seismic data • Improved signal-to-noise ratio • Improved fault recognition • Narrowed steep features • Widened rimsynclines • Improved reflection continuation
- 10. Chalk Map Top Chalk E04 E05 E06 F04 F05 E07 E10 D09 D12 -600 -800 -1000 -1200 -1400 -1600 -1800 -2000 -2200 Elevation time (ms) F07 F10
- 11. Chalk Map Top Chalk EBN 3D AmsterdamPG 2D
- 12. Chalk Leads • Polygons of leads based on closing contours • 28 structures >10 km2 ; 9 structures 5-10km2 Area (km2 ) Height (ms) Nearby Well result Bright spot Structure 16 123 N/A - Anticline 30 186 Gas shows - Anticline 12 161 Gas shows - Collapsed AC 11 92 Gas shows - Anticline 10 75 Gas shows - Anticline 26 160 N/A - Anticline 15 70 N/A + Anticline 29 56 Dry + Flat AC 22 160 Gas shows + Anticline 34 149 N/A - Anticline 12 38 N/A - Flat AC 13 70 Dry + Anticline 38 121 Dry - Flat AC 22 62 Dry - Flat AC 30 81 Gas - Flat AC 21 111 Oil&Gas shows - Anticline 11 75 Dry + Anticline 18 84 Gas + Anticline 12 55 Dry + Anticline 70 405 Gas shows + Steep collapsed AC 65 57 Gas shows + Flat AC 20 117 Dry ++ Collapsed AC 28 861 Oil shows ++ Steep AC 45 81 Oil shows + Flat AC 63 412 Oil shows ++ Steep AC 29 339 Gas shows + Steep AC 21 221 Gas shows + Steep AC 10 209 Dry + Steep AC 8 32 N/A - Flat AC 9 23 Dry - Flat AC 9 68 N/A - Anticline 6 44 N/A - Anticline 6 81 N/A - Anticline 6 65 Oil shows - Anticline 10 33 Oil&Gas shows - Flat AC 6 15 Dry + Flat AC 5 198 Dry + Steep AC 5 44 Dry + Collapsed AC 0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 800.0 900.0 1000.0 0.0 20.0 40.0 60.0 80.0 Column Height(ms) Area (km2) F02-Hanze
- 13. Conclusions • Still high untapped potential in northern Dutch offshore • Reprocessed 2D-seismic data significantly improves quality • Regional analysis with 2D seismic gives an excellent indication of HC-potential different structures • Deliverables project: Geological report, 2D-seismic dataset and Petrel-project: Interpreted re-processed seismic dataset All wells incl. LAS-files and TD-tables Well top re-interpretation Well log analysis Polygon set of leads Maps of reservoir & seal Regional maps by TNO Chalk
- 14. Down to earth Thank you for your attention! D.P.M. Stegers d.stegers@amsterdampg.com www.amsterdampg.com
Editor's Notes
- After the collapse of oil prices in the second half of 2014, prices still not have adjusted and are less than half of what it used to be
- Various trendlines (liniear, exponential, polynomal) do not anticipate a merry forecasts of the future…
- If you look long enough, there actually is potential! R-square value of .96 indicates that this is véry likely ;-) The future looks bright indeed! Let’s start exploring!
- New discoveries led to further interest in this area. EBN/Fugro initiated further interest with 3D-survey (one of the last areas without). Expensive!
- 2D-seismic dataset: from 80’s and 90’s. Not bad, but reprocessing improves the quality
- Is this only a seismic project? No! A lot has been done in the Chalk project, including the subjects above. Too much to illustrate in just 10 minutes.
- Example salt structure. Bright spots – rimsynclines – steep structure
- Reprocessing led to several adjustments: steeper structure, more defined faults, wider rimsynclines, better overall continuation. Especially for post-stack 2D-data, quite an improvement
- Top Chalk map according to DEF-study AmsterdamPG
- Comparison between AmsterdamPG and EBN: for regional study the 2D-data gives excellent results, even up tot detail. Accordingly, an interesting structure can be closer analysed in detail with the available 3D-seismic data
- Analysis of structure, including nearby well results