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  1. 1. Classification: Internal 2011-09-06 Earths Energy Golden Zone : A history and future for petroleum exploration Paul Nadeau Dept. Petroleum Engineering University of Stavanger PET500
  2. 2. 2 Clay Diagenesis in Shales/Mudstones: Impact on Subsurface Rock-Fluid Systems Diagenetic clay precipitation severely reduces permeability Main control is temperature, initiating at 60 to 80C At temperatures > 60C : The risk of overpressure development increases The probability of hydrocarbon charge increases The risk of biodegradtion decreases Combined with thermo-chemical rates of quartz cementational porosity loss, the risk of hard overpressure, seal failure & oil/gas remigration increases exponentially at temperatures > 120C (Buller et al., 2005)
  3. 3. 3 Smectite / Kaolinite + K feldspar Reactant dissolution Illite precipitation The Golden Zone Chemical Seal (Nadeau, 2011) Major permeability reduction due to pervasive pore-bridging illite > 60oC
  4. 4. 4 Statoil F&T/phn/SOCAR-1/10.00 Modified after: Srodon & Eberl, 1984; Hower et al., 1976; Boles & Franks, 1979; Pearson et al., 1982, Nadeau et al., 1985*. Clay Diagenesis in Shales: Smectite to Illite vs. Temperature NB: Reaction onset is circa 60 to 80C in the North Sea and the Gulf of Mexico Permeability Reduction results from nucleation of circa 0.1 micron clay minerals in pore-network* North Sea Gulf of Mexico Percent Illite Layers TemperatureC 0 20 40 60 80 100 120 140 160 180 200 20 40 60 80 100 NB: Onset for Non-Calcareous Shales may be 60 C & Calcareous shales May be 80 C TemperatureC Nadeau et al., 2002 SEM North Sea Shales
  5. 5. 5 Quartz Cementation: Petrographic Evidence 250 microns Depth: 2.3 km Porosity: 30 % Well: 6507/8-4 250 microns Depth: 4.6 km Porosity: 10 % Well: 6406/2-7 Statoil INT GEX NO GS /phn 05.03(Buller et al., 2005)
  6. 6. 6 Quartz Cementation in Sandstones Mica / Quartz Dissolution Surfaces Quartz grain Quartz- Cement Sequentially coupled Silica Dissolution Transport & Precipitation process is : Precipitation Rate Controlled by TEMPERATURE & Pressure Insensitive Dissolution Mica / Illite Mica / Illite Mica / Illite Mica / Illite circa 25% Volume Reduction by Cementation / Redistribution Statoil INT GEX NO GS /phn 05.03 (Buller et al., 2005) (Bjrkum et al., 1998)
  7. 7. 7 The Golden Zone Chemical Pump (Nadeau, 2011) c. 40% c. 25% < 20%
  8. 8. 8 Quartz Cementation: Porosity Loss Rates vs Temperature 100 160140120 PorosityLossRatesin%/My 2.0 1.5 1.0 0.5 0 Medium Grained Sandstone Sandstones dVqtz dt = Ae -E/RT S( -1) cSiO2 Kqtz x S = Quartz Surface Area 0.2%/ My at 120 C Temperature C Quartz Cmt. Jurassic = 20% Miocene = 120C
  9. 11. 11 The Golden Zone for Oil & Gas Reserves (Buller et al., 2005) (Nadeau, 2011)
  10. 12. 12 The Golden Zone Paradigm Temperature represents integrated risks for : Hydrocarbon charge & Biodegradation Reservoir Quality, Overpressure, & Trap & Seal integrity Optimal Hydrocarbon Entrapment Efficiency in Basins Between 60C and 120C i.e. the Golden Zone The Golden Zone is controlled by Geothermal Gradients Globally these gradients in Sedimentary Basins are: 30C +/- 10C per km (P50, P10 & P90) The Golden Zone is on average 2 km thick (2, 1.5, 3 km) Bjrkum & Nadeau, 1998; Buller et al., 2005; Nadeau et al., 2005
  11. 13. Validating The Golden Zone
  12. 14. 14 Mapping the Golden Zone: Reservoir Data A Case Study of Planet Earth (Total circa 120,000) Sources: NPD, DTI, IHS, EUB, MMS, DOE & Univ. OK (after Ehrenberg & Nadeau, 2005) Gulf of Mexico North Sea Bombay Reservoirs
  13. 15. 15 The Golden Zone: North Viking Graben 270 km 0 km NorwayTrollGullfaksStatfjord 30 km 10 km 20 km S RR R SE Modified after Fjeldskaar et al., 2004, Fig. 12. NW GZ GZ 60C isotherm R = Reservoirs 120C isotherm S = Source Rocks S R Oseberg Restricted Lateral Drainage & Pressure Compartments Due to Basement Faults HPHT R Frigg
  14. 16. 16 0 1000 2000 3000 4000 5000 6000 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% depth(m) exploratory wells drilled recoverablehc 0 1000 2000 3000 4000 5000 6000 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% depth(m) wellsdrilled hcrecoverable 60 120 60 120 Exploration Efficiency: Oil & Gas vs. Well Depth North Sea: 60% Bombay: 10% 30 to 35C/km Circa 80C/km Cumulative % Exploration well depth / TVD to 90% of Resources Cumulative % Oil + Gas Base Reservoir Depth 90% of Exploration well depths > depth to 90% of Resources 1 2 3 4 5 6 1 2 3 4 5 6 0 0 Golden Zone Golden Zone Nadeau et al., 2005 HPHT
  15. 17. 17 Petroleum Remigration: The Golden Zone Play Hotel Model (Nadeau, 2011)
  16. 18. 18 Offshore Gulf of Mexico: 12,000 Reservoirs (Nadeau, 2011; Ehrenberg et al., 2008 / Data: MMS, 2003; Seni et al. & Hentz et al., 1997) (Nadeau, 2011)
  17. 19. 19 Offshore Gulf of Mexico: Generalized N-S Cross Section (Nadeau, 2011)
  18. 20. 20 Gulf of Mexico Shelf Reservoirs: Temperature vs. Pressure & Field Reservoirs TemperatureC Pressure SG Pressure Golden Zone Percent Reservoirs 60 120 90% Oil & 80% Gas Reservoirs 60-120C HPHT Ehrenberg et al., 2008, Nadeau et al., 2005 P90, P50, P10
  19. 21. Classification: Internal 2011-09-06 21 Petroleum Remigration & Reservoir Gas/Oil Ratio (GOR) GB Lectrure MS: Fig. 10 20 40 60 80 100 120 140 160 180 200 Log Reservoir GOR ReservoirTemperatureC Oil Gas Gas Cond. HPHT COMPACTION ZONE EXPULSION ZONE (Nadeau, 2011)
  20. 22. 22 Temperature Prediction: The Golden Zone Reservoir Method (Nadeau, 2011)
  21. 23. 23 US Gulf of Mexico Estimated Geothermal Gradients: Red = High, Blue = Low BOEMRE reservoir and NOAA sea-floor temperatures, water depth contour interval 200 m (Nadeau, 2011)
  22. 24. 24 Fluid Pressue Probability Plots: US Gulf of Mexico 5% 20% 65% (Nadeau, 2011)
  23. 25. A Golden Zone Exploration Risk Model Greater Discovered Volumes at Substantially Reduced Finding Costs
  24. 26. 26 Global Cumulative Oil Reserves vs. Temperature 0 100 200 300 400 500 600 700 Oil Reserves in BBO 0 20 40 60 80 100 120 140 160 180 200 TemperatureC 0 100 200 300 400 500 600 700 Oil Reserves in BBO 0 20 40 60 80 100 120 140 160 180 200 TemperatureC 12% < 60C (0.2% / C) 85% 60 to 120C (1.5% / C) 3% > 120C (0.05% / C) Related to the impact of Diagenesis on HC Migration, Trap & Recovery Efficiency. Nadeau et al., 2005 Golden Zone Total Recoverable Oil Reserves (proven + probable) HPHT
  25. 27. 27 Table 1. Distribution of Global Conventional Petroleum Reserves (including condensate)
  26. 28. 28 Mapping the Earths Golden Zone Integrated map of: Reservoir temperatures Total sediment thickness Surface temperatures & geology Depth to 60C isotherm
  27. 29. Classification: Internal 2011-09-06 The Golden Zone Discovery Process
  28. 30. 30 Norway: Discovery & Production History Norways Total Discovered Oil+Gas Reserves=60BBOE Of which > 50% Have been produced. (Norwegian Petroleum Directorate, 2006) Norway Cumulative Discovered and Produced Oil & Gas 0 10000 20000 30000 40000 50000 60000 70000 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Discovery Year RecoverableReservesP+PMmboe E S T+O OL
  29. 31. 31 Past Discovery after ExxonMobil (Longwell). Future Discovery extrapolated The Growing Gap 0 10 20 30 40 50 60 1930 1950 1970 1990 2010 2030 2050 Gb Past Discovery Future Discovery Production ? Global Oil Reserves: Exploration vs. Production NB: Discovery rate < 10 Gb/yr
  30. 32. 32 Present Day Perspective: World Creamed ??? Global Creaming Curve: Oil y = -8.3805x3 + 49359x2 - 1E+08x + 6E+10 R2 = 0.9953 0 500000 1000000 1500000 2000000 1910 1930 1950 1970 1990 2010 2030 Discovery Year CumulativeVolumeMMbo CONTROL: Geology - model predicts limited yet-to-find. NB. Golden Zone mainly creamed / drilled using rotary drilling tech. (invented circa 1910) w/ anticlinal theory of oil, in the 25 years after WWII. Discovery Rate has Fallen since then Despite Improved Technology & Price. WWII 1980 Oil Price Hike Did not affect Discovery Rate
  31. 33. 33 Global Oil Production Scenarios: EIA/USGS, 2005 & Hubbert, 1969 Hubbert, 1969 2100 0 10 20 30 40 50 60 70 80 90 1900 1925 1950 1975 2000 2025 2050 2075 2100 2046 2035 2021 2026 3% Efficiency/Conservation Increase moves Peak Oil 25 years . NB: after EIA Peak, production drops by Half in less than 10 years ! * * July, 2008 actual 30
  32. 34. 34 How Much is 80 Million barrels of Oil / day ? Global production is currently circa 80 million barrels Of Oil per day. The Suldal River in W. Norway flows at a rate of circa 40 Million Barrels per day (circa 75 m3/sec.) GEX team 18.09.02Approx. Global Oil Production Rate !
  33. 35. 35 What do Production Profiles look like ? Statfjord Field is an efficient profile, but Ekofisk Field is not. The OD had Phillips Petroleum begin Ekofisk water injection in 1987, With immediate Positive Results ! (after Nadeau & Ehrenberg, 2006)
  34. 36. 36 Oil Price Spike of 2008 & The Global Recession 584 Billion usd/yr annual monthly US oil import Costs from 2000-2008 are about half of the US dept ~ 3 Trillion usd for that period.
  35. 37. Classification: Internal 2011-09-06 The Golden Zone & Building a Stronger Energy Bridge to a Sustainable Future
  36. 38. Implications for Future Oil Giant Discoveries Re-examine regional 2D data for shallow targets, c. 1.7 to 2.7 km depth TVD i.e. the upper part of the Golden Zone in the North Sea & Mid-Norway Focus on Oil rich kitchen areas Select Geological sites favourable for stratigraphic / subtle trap geometries Integrate with 3D where available Include HC indicators such as: Oil/Gas Seepage Seabed features, pochmarks and cold water coral colonies Potential f