That is my presentation for my grad research about reservoir geomechanics, hope you find it useful, and my source book was reservoir geomechanics for prof Mark Zoback, soon the PDF copy will be available as well.
The extensive slide-pack starts with introducing physics and basics on geomechanics. A lot of stress and rock strength concepts are explored. Then it moves on to explain the importance of the discipline for drilling, injection, sanding. Apart from giving theory to understand more difficult content that follow, it throws in practical application and prepares good ground for further study of geomechanical literature.
This five-day course provides an intermediate level of understanding of the geomechanical factors that affect wellbore instability, sand production and hydraulic fracture design. The course is structured such that upon completion, participants will have understood the value that geomechanics can bring to drilling, completion and production operations and will be able to leverage this value wherever it applies. The course emphasis will be on integrating the topics presented through a combination of lectures, case-studies and hands-on exercises. A special focus will be on how geomechanics knowledge is extracted from routinely acquired well data and how it is applied in the prediction and prevention of formation instability.
That is my presentation for my grad research about reservoir geomechanics, hope you find it useful, and my source book was reservoir geomechanics for prof Mark Zoback, soon the PDF copy will be available as well.
The extensive slide-pack starts with introducing physics and basics on geomechanics. A lot of stress and rock strength concepts are explored. Then it moves on to explain the importance of the discipline for drilling, injection, sanding. Apart from giving theory to understand more difficult content that follow, it throws in practical application and prepares good ground for further study of geomechanical literature.
This five-day course provides an intermediate level of understanding of the geomechanical factors that affect wellbore instability, sand production and hydraulic fracture design. The course is structured such that upon completion, participants will have understood the value that geomechanics can bring to drilling, completion and production operations and will be able to leverage this value wherever it applies. The course emphasis will be on integrating the topics presented through a combination of lectures, case-studies and hands-on exercises. A special focus will be on how geomechanics knowledge is extracted from routinely acquired well data and how it is applied in the prediction and prevention of formation instability.
Stress analysis is the essence that is needed while planning exploration, drilling and development operations in oil and gas industries. Proper knowledge of Geomechanics will help us to reduce the risk of failure as well as provide a better picture of stresses inside the earth. From Hydrofracturing to directional drilling, stresses play their parts.
The presentation highlights the root causes of major drilling issues such as formation pressure uncertainty, subsurface feature like mud volcanoes, major fault, poor well planning & etc. Then it elaborates on consequences of all above on examples of wellbore instability, sticking, gumbo & so on.
Briefly explaining the basics of Pore Pressure Fracture Gradient (PPFG) plot & its role in planning, drilling & decision making. Please, refer to my "Formation pressure" upload for more details on pressure concepts.
A presentation of the acoustic waveform at a receiver of a sonic or ultrasonic measurement, in which the amplitude is presented in color or the shades of a gray scale. The variable-density log is commonly used as an adjacent to the cement-bond log, and offers better insights into its interpretation.
Extended-reach wells present difficult drilling challenges, which if inadequately understood and addressed can yield significant downside risks and extensive non-productive time (NPT). These challenges are mainly due to complex well designs that combine high-deviation and extended-reach wellbores with difficult geology and hostile environments. Understanding the challenges and developing solutions are important to deliver the well with the proper casing specifications for production purposes.
Geomechanically, due to their long reaches and high deviations, borehole instability and lost circulations are particularly dominant in the overburden shale sections of extended-reach and horizontal wells. However, a good understanding of the rock failure mechanisms and an innovative use of the wellbore strengthening techniques can mitigate these geomechanical challenges through integration with good drilling practices such as efficient equivalent circulating density (ECD) management and effective hole-cleaning strategies. In addition, the long open-hole exposure typically experienced in these wells can cause chemical, thermal and/or fluid penetration issues that can further complicate the difficult drilling conditions. These secondary influences further stress the importance of incorporating geomechanical understanding in drilling fluids formulation.
This presentation focuses on the geomechanical challenges of drilling extended-reach wells. It highlights the need to integrate geomechanical solutions with appropriate drilling practices, particularly solutions based on good understanding of the intricate relationship between borehole stability, lost circulation, ECD, hole cleaning and bottom-hole assembly (BHA) optimizations in overcoming the drilling performance limiters. A case history will be presented as an example.
Borehole geophysics is the science of recording and analyzing measurements of physical properties made in wells or test holes. Probes that measure different properties are lowered into the borehole to collect continuous or point data that is graphically displayed as a geophysical log. Multiple logs typically are collected to take advantage of their synergistic nature--much more can be learned by the analysis of a suite of logs as a group than by the analysis of the same logs individually. Borehole geophysics is used in ground-water and environmental investigations to obtain information on well construction, rock lithology and fractures, permeability and porosity, and water quality. The geophysical logging system consists of probes, cable and drawworks, power and processing modules, and data recording units. State-of-the-art logging systems are controlled by a computer and can collect multiple logs with one pass of the probe
Microfracturing is an excellent method of obtaining direct stress measurements, not only in shales, but in conventional reservoirs as well. Recent advances have shown that microfracturing can help improve reservoir management by guiding well placement, completion design, and perforation strategy. Microfracturing consists of isolating small test intervals in a well between inflatable packers, increasing the pressure until a small fracture forms and then by conducting a few injection and shut-in cycles, extend the fracture beyond the influence of the wellbore. Results show that direct stress measurements can be successfully acquired at multiple intervals in a few hours and the vertical scale nearly corresponds to electric log resolution. Therefore, microfracture testing (generally performed in a pilot / vertical well) is an appropriate choice for calibrating log derived geomechanical models and obtaining a complete, accurate, and precise vertical stress profile. This talk describes the microfracturing process and presents several examples that led to increased hydrocarbon recovery by efficient stimulation and/or completion design. Case studies presented range from optimizing hydraulic fracturing in unconventionals, determining safe waterflood injection rates in brownfields, and improving perforation placement in ultra deepwater reservoirs.
Mayank Malik is the Global Formation Testing Expert in Chevron's Energy Technology Company and is a champion for advancing research on microfracturing. He holds a B.S. in Mechanical Engineering from Delhi College of Engineering (India), MS in Mechanical Engineering from University of Toronto (Canada), and Ph.D. in Petroleum Engineering from The University of Texas at Austin (USA). Malik has authored numerous papers on petrophysics, formation testing, and microfracturing. He is currently serving on the SPE ATCE Formation Evaluation committee and is also the Chairman for SPWLA Formation Testing Special Interest Group.
Stress analysis is the essence that is needed while planning exploration, drilling and development operations in oil and gas industries. Proper knowledge of Geomechanics will help us to reduce the risk of failure as well as provide a better picture of stresses inside the earth. From Hydrofracturing to directional drilling, stresses play their parts.
The presentation highlights the root causes of major drilling issues such as formation pressure uncertainty, subsurface feature like mud volcanoes, major fault, poor well planning & etc. Then it elaborates on consequences of all above on examples of wellbore instability, sticking, gumbo & so on.
Briefly explaining the basics of Pore Pressure Fracture Gradient (PPFG) plot & its role in planning, drilling & decision making. Please, refer to my "Formation pressure" upload for more details on pressure concepts.
A presentation of the acoustic waveform at a receiver of a sonic or ultrasonic measurement, in which the amplitude is presented in color or the shades of a gray scale. The variable-density log is commonly used as an adjacent to the cement-bond log, and offers better insights into its interpretation.
Extended-reach wells present difficult drilling challenges, which if inadequately understood and addressed can yield significant downside risks and extensive non-productive time (NPT). These challenges are mainly due to complex well designs that combine high-deviation and extended-reach wellbores with difficult geology and hostile environments. Understanding the challenges and developing solutions are important to deliver the well with the proper casing specifications for production purposes.
Geomechanically, due to their long reaches and high deviations, borehole instability and lost circulations are particularly dominant in the overburden shale sections of extended-reach and horizontal wells. However, a good understanding of the rock failure mechanisms and an innovative use of the wellbore strengthening techniques can mitigate these geomechanical challenges through integration with good drilling practices such as efficient equivalent circulating density (ECD) management and effective hole-cleaning strategies. In addition, the long open-hole exposure typically experienced in these wells can cause chemical, thermal and/or fluid penetration issues that can further complicate the difficult drilling conditions. These secondary influences further stress the importance of incorporating geomechanical understanding in drilling fluids formulation.
This presentation focuses on the geomechanical challenges of drilling extended-reach wells. It highlights the need to integrate geomechanical solutions with appropriate drilling practices, particularly solutions based on good understanding of the intricate relationship between borehole stability, lost circulation, ECD, hole cleaning and bottom-hole assembly (BHA) optimizations in overcoming the drilling performance limiters. A case history will be presented as an example.
Borehole geophysics is the science of recording and analyzing measurements of physical properties made in wells or test holes. Probes that measure different properties are lowered into the borehole to collect continuous or point data that is graphically displayed as a geophysical log. Multiple logs typically are collected to take advantage of their synergistic nature--much more can be learned by the analysis of a suite of logs as a group than by the analysis of the same logs individually. Borehole geophysics is used in ground-water and environmental investigations to obtain information on well construction, rock lithology and fractures, permeability and porosity, and water quality. The geophysical logging system consists of probes, cable and drawworks, power and processing modules, and data recording units. State-of-the-art logging systems are controlled by a computer and can collect multiple logs with one pass of the probe
Microfracturing is an excellent method of obtaining direct stress measurements, not only in shales, but in conventional reservoirs as well. Recent advances have shown that microfracturing can help improve reservoir management by guiding well placement, completion design, and perforation strategy. Microfracturing consists of isolating small test intervals in a well between inflatable packers, increasing the pressure until a small fracture forms and then by conducting a few injection and shut-in cycles, extend the fracture beyond the influence of the wellbore. Results show that direct stress measurements can be successfully acquired at multiple intervals in a few hours and the vertical scale nearly corresponds to electric log resolution. Therefore, microfracture testing (generally performed in a pilot / vertical well) is an appropriate choice for calibrating log derived geomechanical models and obtaining a complete, accurate, and precise vertical stress profile. This talk describes the microfracturing process and presents several examples that led to increased hydrocarbon recovery by efficient stimulation and/or completion design. Case studies presented range from optimizing hydraulic fracturing in unconventionals, determining safe waterflood injection rates in brownfields, and improving perforation placement in ultra deepwater reservoirs.
Mayank Malik is the Global Formation Testing Expert in Chevron's Energy Technology Company and is a champion for advancing research on microfracturing. He holds a B.S. in Mechanical Engineering from Delhi College of Engineering (India), MS in Mechanical Engineering from University of Toronto (Canada), and Ph.D. in Petroleum Engineering from The University of Texas at Austin (USA). Malik has authored numerous papers on petrophysics, formation testing, and microfracturing. He is currently serving on the SPE ATCE Formation Evaluation committee and is also the Chairman for SPWLA Formation Testing Special Interest Group.
Rocks mechanics and its application in mining geology.
It aims at enhancing the mining process and higher yielding by reducing the chance of failures by providing information about the rocks of the mining area.
1. Determination of the State of Stress With
Applications to Wellbore Stability and
Fracture Flow in Reservoirs
Mark Zoback
Professor of Geophysics
Stanford University
1
2. Geomechanics Through the Life of a Field
E xploration A ppraisal D evelopment H arvest A bandonment
P
r Wellbore Stability
o Pore Pressure Prediction
Fault Seal/ Fracture Permeability
d
u Sand Production Prediction
c Compaction
t Casing Shear
i Subsidence
Coupled Reservoir Simulation
o
Fracture Stimulation/ Refrac
n Depletion
Geomechanical Model
Time
3. Geomechanics Through the Life of a Field
E xploration A ppraisal D evelopment H arvest A bandonment
P
r Wellbore Stability
o Pore Pressure Prediction
Fault Seal/ Fracture Permeability
d
u Sand Production Prediction
c Compaction
t Casing Shear
i Subsidence
Coupled Reservoir Simulation
o
Fracture Stimulation/ Refrac
n Depletion
Geomechanical Model
Time
4. Middle East and
Caspian Sea
GMI
Dubai
LEGEND
Wellbore Stability
Fracture Permeability
Fault Seal
Pore Pressure
Sand Production
Stress Direction
Last Update:
1/10/09
5. Topics
How to Determine the State of Stress in
Oil and Gas Wells (and How Not To)
Wellbore Stability Applications
Fluid Flow in Fractured Reservoirs
3D/4D Geomechanics
6.
7. Get the Stress Right!
Principal Stresses at Depth
Sv – Overburden
SHmax – Maximum horizontal
Sv principal stress
Shmin – Minimum horizontal
principal stress
Additional Components of a
Geomechanical Model
UCS Pp – Pore Pressure
Pp
UCS – Rock Strength (from logs)
Fractures and Faults (from Image
Shmin SHmax Logs, Seismic, etc.)
7
8. Developing a Comprehensive Geomechanical Model
Parameter Data
z0
Vertical stress Sv (z0 ) = ∫ ρ g dz
0
Least principal
stress Shmin ⇐ LOT, XLOT, minifrac
Max. Horizontal
Stress SHmax magnitude ⇐ modeling
wellbore failures
Stress
Orientation Orientation of Wellbore failures
Pore pressure Pp ⇐ Measure, sonic, seismic
Rock Strength Lab, Logs, Modeling well failure
Faults/Bedding Wellbore Imaging
Planes
16. Geomechanics Through the Life of a Field
E xploration A ppraisal D evelopment H arvest A bandonment
P
r Wellbore Stability
o Pore Pressure Prediction
Fault Seal/ Fracture Permeability
d
u Sand Production Prediction
c Compaction
t Casing Shear
i Subsidence
Coupled Reservoir Simulation
o
Fracture Stimulation/ Refrac
n Depletion
Geomechanical Model
Time
18. Don’t Calculate Stress From Poisson’s Ratio
Assumptions: However...
•Sv applied instantaneously •Observations indicate that the
•No other sources of stress exist horizontal stresses are not equal,
•No horizontal strain (Bilateral
•Model doesn't explain SH > Sh > Sv,
Constraint)
•Material is elastic, homogeneous •Global tectonic activity indicates that
and isotropic from the time Sv is the crust is not tectonically relaxed
applied to the present
ν
SH - Pp ~ 1− ν
(Sv - Pp)α
Utilizing an Effective
Poisson’s Ratio and
Adding Tectonic Stress
Does Not Make Model
Correct
Lateral Constraint
(horizontal strain = zero)
20. Topics
How to Determine the State of Stress in
Oil and Gas Wells (and How Not To)
Wellbore Stability Applications
Fluid Flow in Fractured Reservoirs
3D/4D Geomechanics
21. The Key to Wellbore Stability is Controlling the
Width of Failure Zones
24. Tendency for Breakout Initiation for
Different Stress Regimes
3 km Depth, Hydrostatic Pp
25. Mud Weight Needed to Maintain 30º Breakouts
Normal Strike-Slip Reverse
Stress States Same as Previous Slide
Medium Strong Rock UCS = 7250 psi
26. Example - Stability of Uncased Multi-Laterals
Key Questions:
• Is it possible to leave short sections
(~15’), of laterals uncased near the
parent well?
• Will such intervals be stable as the
reservoir is produced?
• Could producing too fast
exacerbate sand production and
stability problems?
27. Calibrated Rock Strength Log
C o, K psi
0 5 10 15 20
9500
• Triaxial tests in laboratory
9600
• Relate strength to P-wave
modulus
9700
• Use ∆T and density to compute
UCS
9800
• Caution - should not be used in
hydrocarbon zones
9900
10000
28. Wellbore Stability Plot
N
Less stable
Required mud weight
Required Strength
Breakout Width W E
More stable
S
S H m ax
Lower hemisphere stereographic projection of well orientation
29. Previously Unknown
Drilling Experience
M O NO PO D
K-2 6 -9
80
0'
0'
70
-9
0'
60
-9
in g
B ay
Fa
u lt
-9
00
0'
Well X
'
00
ad
-92
'
00
Tr
0'
-94
-960
0'
-980
-9800'
Drilled at 335 degrees,
KING SALMON
-9
60
0'
G-1 5 RD -9
-9600'
40
0'
-9400'
maximum deviation 108 degrees.
-94
00
'
-9200'
-96 00'
00
' -92
-920
0'
0'
60
-9
Successfully drilled and
0'
-900
-9600'
-940
M-3 1
0'
0'
-940
0'
-920
completed
0'
GRAYLING
-900
00'
-94
0'
20
-9
STEELHEAD
-920
0'
-940
0'
-920
0'
-9
60
0'
0'
-940
Well Y
0'
60
-9
0'
80
-9
Drilled at 31 degrees,
0'
20
-9
DOLLY VARDEN
deviation 88 degrees.
-9
40
0'
-9
60
-9400'
0'
0'
-960
0'
-980
Wellbore collapsed in
open-hole section
30. Moderate Drawdown / Damage
• Decreased pressure drop
• Damage zone less
important
Pore pressure distribution during drawdown
31. Moderate Drawdown / No Damage
Smaller pressure drop
10000
Uniaxial compressive strength [psi]
Lower stress at wellbore
8000
6000
→Relatively more stable
4000 →Total BO’s ~ 100o
2000
0
32. Rapid Drawdown / Damage
• Large pressure drop near
the well
• Exacerbated by damage
zone
Pore pressure distribution
during drawdown
33. Rapid Drawdown / Damage
Large pressure drop
10000
Increased stress at wellbore
Uniaxial compressive strength [psi]
8000
→Unstable well
6000
→Total BO’s > 180o
4000
2000
0
Strength required to prevent failure is too high → excessive breakouts
34. Example 2
• Severe wellbore instabilities in
the Fortune Bay shale led to
abandonment of original PG-2 Side track
well and required drilling a side track
• The side track was completed abandoned
successfully by switching to oil
PG-2
based mud and raising the mud
weight to 12 ppg in the Fortune
Bay shale.
Objective for future wells
• Optimization of wellbore stability
in deviated and horizontal wells
• Feasibility of drilling highly
deviated wells with a maximum
mud weight of ~11.5 ppg
35. Orientation of SHmax
Hibernia
World stress map data
superimposed with mean SHmax
Newfoundland orientation (red arrow) derived from
St. John’s 4-arm caliper and UBI breakout
analysis in vertical wells of the
Terra Nova field
Terra Nova
36. Pore Pressure and Stress in the Terra Nova Field
Pressure/Stress [bar]
0 200 400 600 800 1000
0
Pp[bara] wet sand
Pp water
500 Pp[bara] sand
Pp oil wet
LOT (C-09)
Hydrostatic
Hydrost. [bara]
Overburden
Sv [bara]
1000
Test Pres.[bara]
FIT
LOT
X-LOT
1500
SSTVD [m]
2000
2500
1.117
Sv = 0.0848*SSTVD
3000
X-LOT (GIG-3)
X-LOT (PG-2)
3500
Pp = 0.098*SSTV LOT (C-23)
4000
Shmin = -15.889 + 0.19416*SSTVD
37. Breakouts from UBI log in PG-2
Azimuth [deg]
Fortune
0 90 180 270 360
Shale
•
3800
Total breakout
Bay
no data
Low er FBS
3850 E sand
ED shale
length: 32 m
Dc sand
3900
•
Db shale
Da sand
D congl.
Mean breakout
3950
UC2 sand
width: 40° (±11°)
LC2 shale
Jeanne d’Arc
Reservoir
4000
LC2 sand
C2C1 shale
4050
C1 sand
4100
C1B shale
4150
B sand
B Rank shale
no data Rankin Mbr.
4200
Breakout azimuth
Azimuth (deg)
Breakout (deg)
Width width
38. Breakouts from UBI log in PG-2
N
Lc2 shale within the
W E
Jeanne d’Arc reservoir
S
Isotropic compressive failure
C1 sand within the
Jeanne d’Arc reservoir
39. Breakouts from EMS 6-arm caliper log in PG-2
Jeanne d’Arc reservoir Fortune Bay shale
Isotropic failure Anisotropic failure
The difference in failure behavior between the Fortune Bay shale
and the Jeanne d’Arc reservoir is similar to the UBI images
40. Breakouts from UBI log in PG-2
Lowermost Fortune Bay shale
Anisotropic compressive failure
41. Modeling anisotropic breakouts in the Fortune Bay shale
with the given in situ stress state
Anisotropic failure Anisotropic failure
Bedding plane properties:
• dip = 8° (from core data)
• Azi = 23° (from core data)
• S0 = 4.8 MPa (from lab data)
• µs = 0.21 (from lab data)
MW = 10.5 ppg MW = 12 ppg Result:
The in situ stress tensor
Isotropic failure Observed
derived in this study and the
bedding plane properties
measured in the lab can
account for the anisotropic
breakouts seen in the Fortune
Bay shale
42. Predicting stability in the
Fortune Bay shale for well GIG-3
C0 = 55 MPa
wBO = 75° MW = 12 ppg
Assuming anisotropic behavior
• There exists a steep stability gradient for deviations between 25° and 45 °
• Well PG-2 is oriented less favorably in the current stress field
• Well GIG-3 is oriented more favorably in the current stress field
• Severe stability problems can be avoided for GIG-3 with a maximum
mud weight of 11.5 ppg if deviation < 30 °
43. Business impact
• Petro-Canada successfully drilled well
GIG-3 through the Fortune Bay Shale successful
by limiting deviation to 27° and
mud weights to 10.5 ppg – 11 ppg
abandoned
• Petro-Canada avoided costly stability
PG-2
problems by following GMI’s
recommendations for this well
successful
GI
G-
3
Graben structure at base of reservoir
44. Topics
How to Determine the State of Stress in
Oil and Gas Wells (and How Not To)
Wellbore Stability Applications
Fluid Flow in Fractured Reservoirs
3D/4D Geomechanics
47. Active Faults Maintain Permeability Through Time
Faulting is key to maintaining permeability
48. Temperature Anomalies and
Permeable Faults in the KTB Borehole
Zoback and Townend (2001)
Ito and Zoback (2000)
49. Mechanical Lithosphere
Zoback, Townend and Grollimund (2002)
High Stress, Critically-Stressed Crust
Ductile Lower Crust and Upper Mantle
Is This Model Quantitatively Correct?
58. Need For a Better Model to Match Reservoir Flow
Permeability Model Does Not Match
Pressure Data in
Producers or Injectors
59. No Wells Directly in Damage Zones
Dynamic Rupture Propagation to Calculate Damage Zones
Depth ~2700m
0 2000 N
m
Origin point of rupture
8
x 10
Damage Intensity 1 .5
sxx
Damage zone sxy
syy
1 szy
szx
s t r e s s m a g n it u d e ( P a )
Rock strength szz
Horizontal Plane 0 .5 S1
S2
S3
oct shear
0 to ta l o c t s h e a r
Fault Plane
-0 .5
Cross Section View Along -1
0 50 100 150 200 250 300
Strike of Normal Fault d is t a n c e f r o m r u p t u r e f r o n t ( m )
60. Calculated Damage Zone Width
At reservoir depths from
100 simulations:
Simulation 1 Mean of DZ width ~50-90m
Simulation 2
Process Zone Width, m
Simulation 3
Fault Zone Length, m
Simulation 4 Vermilye and Scholz (1998)
2km
61. Utilizing the Dynamic
Rupture Model to
Predict Width of
Damage Zone and
Anisotropic Permeability
64. Geomechanics Through the Life of a Field
E xploration A ppraisal D evelopment H arvest A bandonment
P
r Wellbore Stability
o Pore Pressure Prediction
Fault Seal/ Fracture Permeability
d
u Sand Production Prediction
c Compaction
t Casing Shear
i Subsidence
Coupled Reservoir Simulation
o
Fracture Stimulation/ Refrac
n Depletion
Geomechanical Model
Time