Petroleum & Reservoir Geology Univ. Stavanger PET500 course lecture notes

1. Classification: Internal 2011-09-06
Earth’s Energy “Golden Zone” :
A history and future for petroleum exploration
Paul Nadeau
Dept. Petroleum Engineering
University of Stavanger
PET500

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 80°C
• At temperatures > 60°C :
• 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 > 120°C
(Buller et al., 2005)

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
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 80°C 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
Temperature°C
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
Temperature°C
Nadeau et al., 2002
SEM North Sea Shales

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
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)
(Bjørkum et al., 1998)

7. 7
The Golden Zone Chemical “Pump”
(Nadeau, 2011)
c. 40% Ø
c. 25% Ø
< 20% Ø

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 = <2%
Statoil INT GEX NO GS /phn 05.03
(Walderhaug, 1994;
Bjørkum et al, 1998)
(Buller et al., 2005)

9. Classification: Internal
2011-09-06
9
Overpressure Development: A Common Feature
of Sedimentary Basins
HPHT
(Nadeau, 2011)

10. 10
0
5,000
10,000
15,000
20,000
Pressure psi
1,000
2,000
3,000
4,000
5,000
6,000
Syn-Rift Fluid Pressure Data:
Jurassic North Sea
35°C
65°C
95°C
125°C
155°C
Lithostatic
G
radient
HydrostaticGradient
diagenesis
Hydrofracturing &
Oil Remigration
Depthm
Temperature°C
approximate
Restricted Lateral
Drainage
Statoil INT GEX NO GS /phn 05.03
(70 MPa) (140 MPa)
HPHT
Buller et al., 2005
HPHT
HPHT
HPHT = High
Temperature
High Pressure
Diagenesis & Overpressure Risks > 120°C

11. 11
The “Golden Zone” for Oil & Gas Reserves
(Buller et al., 2005)
(Nadeau, 2011)

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 60°C and 120°C i.e. the “Golden Zone”
• The “Golden Zone” is controlled by Geothermal Gradients
• Globally these gradients in Sedimentary Basins are:
• 30°C +/- 10°C per km (P50, P10 & P90)
• The “Golden Zone” is on average 2 km thick (2, 1.5, 3 km)
Bjørkum & Nadeau, 1998; Buller et al., 2005; Nadeau et al., 2005

13. Validating The Golden Zone

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 ¤

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
60°C isotherm R = Reservoirs
120°C isotherm S = Source Rocks
S
R
Oseberg
Restricted Lateral Drainage
& Pressure Compartments
Due to Basement Faults
HPHT
R
Frigg

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
35°C/km
Circa 80°C/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

17. 17
Petroleum Remigration: The Golden Zone Play “Hotel” Model
(Nadeau, 2011)

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)

19. 19
Offshore Gulf of Mexico: Generalized N-S Cross Section
(Nadeau, 2011)

20. 20
Gulf of Mexico Shelf Reservoirs:
Temperature vs. Pressure & Field Reservoirs
Temperature°C
Pressure SG
Pressure
Golden Zone
Percent Reservoirs
60
120
90% Oil & 80% Gas
Reservoirs 60°-120°C
HPHT
Ehrenberg et al., 2008, Nadeau et al., 2005
P90, P50, P10

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)

22. 22
Temperature Prediction: The Golden Zone Reservoir Method
(Nadeau, 2011)

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)

24. 24
Fluid Pressue Probability Plots: US Gulf of Mexico
5%
20%
65%
(Nadeau, 2011)

25. A Golden Zone Exploration Risk Model
Greater Discovered Volumes at
Substantially Reduced Finding Costs

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
Temperature°C
0 100 200 300 400 500 600 700
Oil Reserves in BBO
0
20
40
60
80
100
120
140
160
180
200
Temperature°C
12% < 60°C
(0.2% / °C)
85% 60 to 120°C
(1.5% / °C)
3% > 120°C
(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

27. 27
Table 1. Distribution of Global
Conventional Petroleum Reserves
(including condensate)

28. 28
Mapping the Earth’s Golden Zone
Integrated map of:
Reservoir temperatures
Total sediment thickness
Surface temperatures & geology
Depth to 60°C isotherm

29. Classification: Internal 2011-09-06
The Golden Zone Discovery Process

30. 30
Norway: Discovery & Production History
Norway’s 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

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

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

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

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. ½ Global Oil Production Rate !

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)

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.

37. Classification: Internal 2011-09-06
The Golden Zone & Building a Stronger
Energy Bridge to a Sustainable Future

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 flat spots & amplitude anomalies for fluid contacts

39. 39
Historical Examples: 2001 UK Buzzard Oil Field
• Discovered in Viking Graben Rift Flank, June 2001 by PanCanadian
• Reservoir top depth 2.4 km, Temperature c. 90 oC.
• Stratigraphic trap in basin embayment setting
• Small Oil Giant, Recoverable Oil > 0.5 Billion Barrels
• Excellent Quality Upper Jurassic Turbidite sands up to 100 m thick
• Low Gas:Oil Ratio, 33 API gravity Oil, 1.4%S
• Investment: c. 2.4 Billion USD, Production Plateau 200,000 Barrels per Day
• Development costs: c. $5/barrel
• Finding costs: < $1/barrel

40. Buzzard: Largest UK Oil Discovery in c. 25 years
40

41. 41
Temp. c. 80oC

42. 42
A Large Oil Giant !

43. Where is the Remaining Giant Oil Potential ???
43
Utsira
Buzzard

44. 44
Statoil LUT GEO RESBES/phn/01.00
World's Super Giant Oil Fields (> 5 BBO)
Estimated Ultimate Recoverable Reserves BBO
NB: 36 Fields with c. 45% of World's Oil
Most discovered BEFORE 1970
Most are in the Middle East.
Ghawar reserves have grown to c 120 BBO since
this graph was made (1992).
Safania
Manifa
NumberofFields
Where are the Remaining Oil Super Giants ?
GhawarBurgan
Bolivar
Sarir
E. Texas*
Prudoe Bay
Shengli
Cantarell
Zakum
Kirkuk
Marun
Samotlor
Romashkinskoye
Bermudez
Daqing
Minas
Kashagan: 2000
Tupi ?
Brazil

45. 45
Global Energy: WHAT WE MUST DO !
• Improve Energy Efficiency: Prolong OUR RESOURCES
• Utilize Renewable Energy: To Improve Efficiency
• Increase Oil & Gas Recovery: Reservoir Geology & Technology
• Selectively & Innovatively Explore for Giant Oil Fields
. . . in the Golden Zone !

46. 46
Future Energy: It’s Up to US !

47. 47
Value of Golden Zone Oil: Most Efficient Energy
0
2
4
6
8
10
GZ Oil Heavy Oil Tar Oil Oil shale? Bio-Oil
EnergyUnits
“It Takes Energy to get Energy ! “
+ ‘Golden Zone’ Oil has the
Highest Net Energy Value
- Other sources are not viable
alternatives . . . IF
they have little or Negative
Net Energy Values, i.e. they
take As Much or More Energy
then they Create.
Oil Sands
NON-VIABLE ?
Highest ‘Net Energy’
?

48. Shale Gas & Oil: The Energy Game Changer
48
Devonian
Mississppian
Devonian
Devonian
Cretaceous
Jurassic
Mississppian
Cretaceous
Cretaceous
Cretaceous
Mississppian
Mississppian
Pennsylvanian
Mississppian
Cretaceous
Source: http://en.wikipedia.org/wiki/Shale_gas_in_the_United_States
Bakken

49. North American Shale Gas and Oil Plays
Geological Age (Bold = Major Plays) Number of Plays (Total = 57)
Miocene 2 (Monterey, Santa Maria Basin)
Eocene 1 (Green River, Uinta Basin)
Cretaceous 10 (Niobrara, Mancos, Lewis, Mowry)
Jurassic 5 (Haynesville)
Triassic 1 (Western Canada Basin)
Pennsylvanian 5 (Excello)
Mississippian 8 (Barnett, Bakken)
Devonian 18 (Marcellus, Antrim, New Albany)
Silurian 1 (Eastern Kentucky)
Ordovician 2 (Utica, Appalachian Foreland Basin)
Cambrian 1 (Alabama, Black Warrior Basin)
49
Source: http://www.marcellus-shale.us/gas-shale_plays.htm

50. 50
How to risk uplift and erosion ?

51. Classification: Internal
2011-09-06
51
Uplift & Erosion: The Golden Zone Story
North Sea Barents Sea Svalbard

52. 52
Impact on Oil & Gas
Exploration Potential
• Arresting source rock maturation and
petroleum charge
• Reduction of reservoir pressure
• Gas expansion and oil spilling from traps
• Hydrocarbon phase changes
• Reduction of seal integrity
• Diffusional leakage of reservoired
hydrocarbons over geological time.

53. 53
Uplifted Arctic Basin: West Barents Sea
NCS - Barents Sea Reserves
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0 500 1000 1500 2000 2500
Oil+Gas+Cond. MMboe
BaseReservoirDepthm(belowseabed)
NCS - Barents Sea Exploration Wells
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0 10 20 30 40 50 60
Cumulative Number of Wells
WellTDm(belowseabed)
Snøhvit
Goliat
Uplifted Golden Zone ?
50% Well drilled >
depth then 90%
Of Reserves
NCS - Barents Sea Reserves
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0 500 1000 1500 2000 2500
Oil+Gas+Cond. MMboe
BaseReservoirDepthm(belowseabed)
NCS - Barents Sea Exploration Wells
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0 10 20 30 40 50 60
Cumulative Number of Wells
WellTDm(belowseabed)
Snøhvit
Goliat
Uplifted Golden Zone ?
50% Well drilled >
depth then 90%
Of Reserves
The NCS Barents Sea
has been Uplifted &
Eroded by circa 1.2 km.
The base of the uplifted
‘Golden Zone’ is now
at circa 2.5 km depth.
Exploration well depths
(50%) have focused
below 2.5 km .
*Although the above suggests that the top of the ‘Golden Zone’ could be at circa 500 m, prospectivity is controlled by
the position of the unconformity erosional surface, and the sealing properties of the geology/lithology below it.
*

54. 54
CO2 and Temperature: The Antarctic Record
NB: + Cycle are slightly > than 100,000 years
+ GLACIAL periods are LONG duration
+ INTERGLACIAL period are SHORT duration <= 10,000 years
+ Cycles are asymmetric
+ Emergence to interglacial periods are RAPID
+ Descent to glacial periods are SLOWER
Questions : + Did the arctic ice cap melt in past interglacials ?
+ How much CO2 is required to postpone
descent into the next glacial period ?
Data Source: National Geographic, Sept. 2004, p. 64-65.
INTERGLACIAL
GLACIAL GLACIAL
Fossil Fuels