Introduction to wellbore stability in drilling operations.

1. Wellbore (in)Stability
A Challenge in Drilling Operations
Don Basuki, MSc. CPG
Jakarta, 30 May, 2023
Webinar Series
1

2. What is wellbore stability?
Basic understanding and concept
Geomechanics model
When shale behaving badly
Lost circulation: cause and mitigation
A
B
C
D
E
Cited as:
Basuki DS (2023) Wellbore (in)Stability: A Challenge in Drilling Operations. Presented at Ilugas Webinar Series, 30 May, Jakarta, Indonesia.

3. ©DSB2023
4
What is Wellbore Stability?
“An application of a
geomechanics study to
prevent wellbore
failure due to collapse
or fracture pressures
during drilling
operations”
(Don Basuki, 2017)

4. ©DSB2023
5
Wellbore stability
EMW (ppg)
Depth
(ft)
Mud window
Collapse
pressure
Fracture
pressure
Wellbore stability is about determining
mudweight limits (min and max) that
prevent compressional (shear) or tensile
failure respectively.

5. ©DSB2023
6
Modern Drilling Operations Challenges
Yesteryear

6. ©DSB2023
7
Modern Drilling Operations Challenges
NOW
Complex trajectories
limited drilling windows
Less wells drilled
learning from offset wells reduced
Deep water drilling
more casings
Difficult to avoid
wellbore stability
issues
mitigation

7. ©DSB2023
9
Drilling Problems → Geohazards NPTs

8. ©DSB2023
10
Origin of Wellbore Instabilities
01 Mechanical
➢ Rock types
➢ Rock stress → Rock strength
➢ Wellbore geometry
➢ Man-made related stress
02 Rock-Chemical
Interaction
➢ Shale instability
✓ Shale collapse
✓ Time-dependent instability
03 Drilling
Practices
➢ Lack of adequate planning
➢ Improper drilling practices
(Modified from Osisanya, 2012)
Osisanya SO (2012) Practical Approach to Solving Wellbore Instability Problems. Lecture Notes, SPE Distinguished Lecturer Program.
https://www.spe.org/dl/docs/2012/osisanya.pdf (accessed 28 October 2020)

9. ©DSB2023
11
Typical wellbore (in)stabilities
Gauged hole
Brittle rock:
Borehole collapse, breakouts,
overgauged hole
Swelling shale, tight hole
Hydraulic fracturing
(Modified from Kang et al., 2009)
Kang Y, Yu M, Miska S, and Takach NE (2009) Wellbore Stability: A Critical Review and Introduction to DEM. SPE 124669

10. ©DSB2023
12
Wellbore Stability – Factors Involved
1 Fractures and faults
2 High stress
3 Low strength
4 Unconsolidated formations
5 Overpressured
1 Mudweight
2 Circulating pressure
3 Wellbore orientation
4 Fluid-Rock interaction
5 Drillstring vibrations
6 Drilling fluid temperature
Natural Drilling

11. ©DSB2023
4 most common wellbore instability mechanisms
(After Pašić et al., 2007)
13
Pašić B, Gaurina-Medimurec N, and Matanović D (2007) Wellbore Instability: Causes and Consequences. Rudarsko-geološko-naftni zbornik v.19 pp.87-98.

12. ©DSB2023
14
Predicting wellbore stability methods
Empirical
Experience-based:
✓ Heuristic rules
✓ Experience
✓ Observational
Lab model
analogues:
✓ Thick-walled
cylinder
✓ Borehole collapse
test
✓ Polyaxial cell
Deterministic
Analytical & Semi
analytical models:
✓ Closed-form
models
✓ Kinematic models
✓ Bifurcation models
Numerical models:
✓ Finite elements
(FEM)
✓ Finite Differences
(FDM)
✓ Distinct elements
(DEM)
Probabilistic
Monte-Carlo Methods
Geostatistical Methods
(Modified from McLellan, 1996)
McLellan PJ (1996) Assessing the Risk of Wellbore Instability in Horizontal and Inclined Wells. The Journal of Canadian Petroleum Technology v.35 n.5 pp.21-32

13. ©DSB2023
Celestino MAL, de Miranda TS, Mariano G, de Lima MA, de Carvalho BRBM, Falcão TdC, Topan JG, Barbosa JA, and Gomez IF (2020) Fault damage zones width: Implications
for the tectonic evolution of the northern border of the Araripe basin, Brazil, NE Brazil. Journal of Structural Geology. DOI: 10.1016/j.jsg.2020.104116
(From Celestino et al., 2020)
15
Faults – Challenge for wellbore stability

14. ©DSB2023
Celestino MAL, de Miranda TS, Mariano G, de Lima MA, de Carvalho BRBM, Falcão TdC, Topan JG, Barbosa JA, and Gomez IF (2020) Fault damage zones width: Implications
for the tectonic evolution of the northern border of the Araripe basin, Brazil, NE Brazil. Journal of Structural Geology. DOI: 10.1016/j.jsg.2020.104116
(From Celestino et al., 2020)
16
Faults – Challenge for wellbore stability
Broadhaven, Pembrokeshire, Wales, UK
Photo courtesy Anton Kristanto, 2018

15. ©DSB2023
17
What is Geomechanics? In brief…
Study of rock and soil mechanics
Movement and failure of rocks
How and why rocks move
What happens when rocks break
Result of nature or man-made

16. ©DSB2023
18
What is Geomechanics?
Sub-Surface Drilling
PHYSICS – MECHANICS
✓ Geology
✓ Geophysics
✓ Geodesy
✓ Geodynamics
✓ Geostatistics
✓ Reservoir
Static Mechanics Dynamic Mechanics
Fluids Mechanics
Solid Mechanics
✓ Gas
✓ Oil
✓ Water
✓ Soil
✓ Rock

17. ©DSB2023
19
Geomechanics Model
GE MECHANICS
Model
Rock
elastic/
mechanical
properties
Pore
Pressure
Stress
properties
υ, E, G, K, ρb,
Co, S0, θi, μi
Static (from lab)
Dynamic (from logs)
Direct
Indirect
Primary Secondary
Andersonian
Classification
Wellbore Stress
In-situ Stress

18. ©DSB2023
20
Geomechanical anatomy
Pp
Sv
Shmin
SHMax
Formation
Strength
Soroush H (2013) Non-conventional Geomechanics for Unconventional Resources. Presented at SPE Distinguished Lecturer Program SPE Northern Emirates Section, Dubai,
UAE 16 January.
(Modified from Soroush, 2013)
E υ

19. ©DSB2023
21
Geomechanics Model
Rock
elastic/
mechanical
properties
Pore
Pressure
Stress
properties

20. ©DSB2023
22
C◦H◦I◦L◦E
D◦I◦A◦N◦E
Modeling assumption
Continuous
Homogeneous
Isotropic
Linearly-Elastic
Discontinuous
Inhomogeneous
Anisotropic
Non-Elastic
Meanwhile in reality…
Common pitfalls in geomechanics modeling

21. ©DSB2023
23
Dynamic Modeling – Circle of Continuity
Pre-Drill
Model Real-Time
Model
Post-Drill
Model

22. ©DSB2023
24
Geomechanical Data Sources
Smith S, Ismail IY, Brehm A, and Castillo D (2006) Impact of Tectonic Stress Variations on Field Development Planning in the Temana and Bayan Field, Sarawak Basin. Paper
presented at GEO Asia Conference, Kuala Lumpur, Malaysia, 12-14 June
(Modified from Smith et al., 2006)

23. ©DSB2023
Shale
25
Not all pore pressure is the same!
Sandstone Carbonate

24. ©DSB2023
Shale
26
Not all pore pressure is the same!
Sandstone Carbonate

25. ©DSB2023
Shale
27
Not all pore pressure is the same!
Sandstone Carbonate

26. ©DSB2023
Shale
28
Not all pore pressure is the same!
Sandstone Carbonate
NO FORMULA FITS ALL!

27. ©DSB2023
30
Some methods used for pore pressure prediction
✓ Equivalent Depth → Hottman and Johnson 1965
✓ Eaton’s (sonic, resistivity) → Eaton 1975
✓ Weakley (modified Eaton) → Weakley 1989
✓ Bowers’ → Bowers 1995
✓ Compressibility Method → Atashbari and Tingay 2012
✓ Dxc → Jorden and Shirley 1966
✓ DEMSE → Majidi et al. 2017
✓ Seismic frequency v. Seismic Vint → Salehi and Mannon 2013
✓ Particle swarm optimization and genetic algorithm → Hossein & Ali (2020)
✓ Some other less common methods → work in certain areas only.
So, Eaton’s and Dxc
are not the only
methods available

28. ©DSB2023
31
Pore pressure prediction methods using drilling parameters
✓ Corrected drilling exponent (Dxc)
✓ Bellotti & Giacca (Sigmalog)
✓ Bourgoyne-Young Method (BYM)
✓ Fillippone
✓ Cardona (PSP3)
✓ Alberty & Fink (Total Gas Method)
✓ Cătălin (Modified Dxc and Sigmalog)
✓ DEMSE
✓ Hydro Rotary Specific Energy
✓ Hydro Mechanical Specific Energy

29. ©DSB2023
32
Carbonate Pore Pressure Prediction Methods
Several prediction methods for carbonates pore pressure:
➢ Hobart (2007) → modified Baldwin-Butler method
➢ Atashbari & Tingay (2012) → compressibility method
➢ Marin-Moreno et al. (2013) → Inverse model
➢ Wang et al. (2013) → effective medium theory
➢ Yu et al. (2014) → Wavelet transformation
➢ Azadpour et al. (2015) → Modified Atashbari & Tingay
➢ DEMSE (2016) → Drilling Efficiency and MSE method
➢ HRSE (2018) → Hydro Rotary Specific Energy
➢ HMSE (2019) → Hydro Mechanical Specific Energy
➢ Morales-Salazar et al. (2020) → Differential Stress-Porosity
➢ Liu et al. (2020) → Rock physics and poroelastic model
➢ Hossein & Ali (2020) → Particle swarm optimization and genetic algorithm
➢ Basuki & Setiawan (2021) → Cpv and MES
EATON’S?

30. ©DSB2023
33
Carbonate Pore Pressure Prediction Methods
Several prediction methods for carbonates pore pressure:
➢ Hobart (2007) → modified Baldwin-Butler method
➢ Atashbari & Tingay (2012) → compressibility method
➢ Marin-Moreno et al. (2013) → Inverse model
➢ Wang et al. (2013) → effective medium theory
➢ Yu et al. (2014) → Wavelet transformation
➢ Azadpour et al. (2015) → Modified Atashbari & Tingay
➢ DEMSE (2016) → Drilling Efficiency and MSE method
➢ HRSE (2018) → Hydro Rotary Specific Energy
➢ HMSE (2019) → Hydro Mechanical Specific Energy
➢ Morales-Salazar et al. (2020) → Differential Stress-Porosity
➢ Liu et al. (2020) → Rock physics and poroelastic model
➢ Hossein & Ali (2020) → Particle swarm optimization and genetic algorithm
➢ Basuki & Setiawan (2021) → Cpv and MES
EATON’S?*
*May work in an
encapsulated carbonate

31. ©DSB2023
34
Pore Pressure Prediction is a SERIOUS Business for Wellbore Stability Study!
Blowout April 2020
Shallow steam pocket kick leads to blowout
Therefore, never
ever underestimate
the importance of
pore pressure study!

32. ©DSB2023
35
Fracture pressure – Drillers’ Way


Pressure
Depth Purpose
✓ To determine upper limit of
pressure in the wellbore to
avoid mud losses anywhere in
the entire open-hole section
✓ Mudweight selection
Remember!
Leak-off can mean several things!
Overburden
Plan Fracture Pressure
Adjusted Fracture Pressure
𝐏𝐟𝐫𝐚𝐜 = LOT1 +
LOT2 − LOT1
D2 − D1
× D − D1
LOT 1
LOT 2

33. ©DSB2023
36
Fracture pressure – Geomechanics Perspective


Pressure
Depth
Overburden
Plan Fracture Pressure
Driller’s fracture pressure
LOT 1
LOT 2
Adjusted Fracture Pressure
Purpose
To determine upper and lower limits
of wellbore pressure to manage
wellbore instability (failure and mud
losses) at every depth in the open-
hole section
S3 (Min. principal in-situ stress)
Variable magnitudes:
✓ Formation type
✓ Mechanical properties
✓ Tectonic setting
From MEM
𝑷𝑓
𝑑𝑟𝑖𝑙𝑙𝑒𝑟
≠ 𝑷𝑓
𝑔𝑒𝑜𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑠
They are not the same, but both are correct for different purposes

34. ©DSB2023
Fracture pressure – Basic idea
Fracture
Pressure
Fracture to initiate a
fracture in formation
S1 (or σ1) → Maximum compressive stress
S2 (or σ2) → Intermediate compressive stress
S3 (or σ3) → Minimum compressive stress
In extensional basin → Pfrac = Shmin
Measurement from LOT or XLOT
Pfrac = S3 or σ3
Hydrofracturing occurs if Pp > Pfrac + τ
Borehole environment includes hoop stresses (or circumferential stresses, normal stresses in the tangential/azimuth direction).

35. ©DSB2023
38
Fracture pressure algorithms
✓ Matthews’ and Kelly’s (1967)
✓ Eaton’s (1969)
✓ Anderson et al. (1973)
✓ Christman (1973)
✓ Breckels & van Eekelen (1981)
✓ Cesaroni et al. (1981)
✓ Daines (1982)
✓ Zoback et al. (1986)
✓ Pore Pressure Stress Coupling (1992)
✓ Zhang & Yin (2017)
✓ Zhang & Zhang (2017)
Common methods:

36. ©DSB2023
39
PPFG Model – An Example Model from Well X
Hydrostatic
Lithostatic
Fracture pressure
Mudweight
Pore pressure
Casing shoe
Top formations
Lithology
Known pressure
Methods used
Methods used

37. ©DSB2023
40
Elastic/Mechanical Properties of Rocks
Complete
stress tensor
Rock properties
Mechanical Earth Model
(MEM)
Poisson’s ratio
Bulk density
UCS

38. ©DSB2023
Why do we need elastic properties?
𝝈𝒉𝒎𝒊𝒏 =
ν
𝟏 − ν
∙ 𝝈𝒗 − 𝜶𝑷𝒑 +
𝑬
𝟏 − ν𝟐
∙ 𝜺𝒉𝒎𝒊𝒏 +
𝑬ν
𝟏 − ν𝟐
∙ 𝜺𝑯𝑴𝒂𝒙 + 𝜶 ∙ 𝑷𝒑
Component from vertical load (ν) Tectonic component (E)
𝝈𝑯𝑴𝒂𝒙 =
ν
𝟏 − ν
∙ 𝝈𝒗 − 𝜶𝑷𝒑 +
𝑬
𝟏 − ν𝟐
∙ 𝜺𝑯𝑴𝒂𝒙 +
𝑬ν
𝟏 − ν𝟐
∙ 𝜺𝒉𝒎𝒊𝒏 + 𝜶 ∙ 𝑷𝒑
41
Thiercelin MJ, and Plumb RA (1994). A Core-Based Prediction of Lithologic Stress Contrasts in East Texas Formations. SPE Formation Evaluation, 9(04), 251–258
(After Thiercelin & Plumb, 1994)
Poroelastic component (α)
Required for calculating the magnitude of
SHMax

39. ©DSB2023
Elastic Properties → Dynamic and Static
Dynamic Static
Continuous data Point data
In situ Laboratory
High strain rate Low strain rate
Derived from sonic log Measured from lab test
Significantly different!
Used for geomechanics model
NEED TRANSFORM FORMULA
42

40. ©DSB2023
43
From logs to lab…
Downhole measurement by high
frequency sonic vibrations
Very low stresses/strain
High strain rate
Always undrained
Measured in lab
High stresses/strain
Low strain rate
Usually drained
Cho SH, Mohanty B, Nakamura Y, Ogato Y, Kitayama H, and Kaneko K (2007) Fracture Processes of Rocks in Dynamics Tensile-splitting Test. Presented at the 1st Canada-US
Rock Mechanics Symposium, Vancouver, Canada, 27 May. ARMA-07-078
Dynamic Static
Needs converting
(After Cho et al., 2007)

41. ©DSB2023
44
Why do we use “static” elastic moduli for geomechanics models?
Rock Mechanical
Test
Dynamic
Static
Seismic Inversion
1-100 Hz
Log Velocity
10-40 kHz
Lab Acoustic
Velocity
100 kHz – 1 MHz
Dispersion caused by frequency The conversion depends on strain magnitude
Dynamic → small/low strains
Static → large/high strains
Correction is not a constant shift!
Lombardo E and Cuervo S (2017) A Simplified Workflow for Estimation of Elastic Anisotropy in Vaca Muerta. Search and Discovery Article #42002, 13 February.
(Modified from Lombardo & Cuervo, 2017)

42. ©DSB2023
Rock’s Moduli
Poisson’s ratio (𝛎) → material’s response in the directions orthogonal to this uniaxial
stress.
Young’s modulus (E) → material's strain response to uniaxial stress in the direction of this
stress (measured stiffness).
Shear modulus (G) → material's response to shear stress (modulus of rigidity).
𝐺 =
𝜏𝑥𝑦
𝛾𝑥𝑦
=
ൗ
𝐹
𝐴
ൗ
∆𝑥
𝑙
=
𝐹 ∙ 𝑙
𝐴 ∙ ∆𝑥
Bulk modulus (K) → material's response to (uniform) hydrostatic pressure (resistancy to
compressibility).
K = −V ∙
𝑑𝑃
𝑑𝑉
= 𝜌 ∙
𝑑𝑃
𝑑𝜌
Relationships
2𝐺 1 + ν = 𝐸 = 3𝐾(1 − 2ν)
ν =
Vp
2
− 2Vs
2
2 Vp
2
− Vs
2
x
y





−
=
E =
ρ. Vs
2
. (3Vp
2
− 4. Vs
2
)
Vp
2
− Vs
2
E =
σ
ε
45

43. ©DSB2023
46
Internal friction angle (i)
IFA: measure of the ability of a unit of rock or soil to withstand a
shear stress.
β
𝛔1
𝛔1
𝛔3
𝛔3
(Modified from Zoback, 2007)
Zoback M (2007) Reservoir Geomechanics. Cambridge University Press, Cambridge New York, USA.
Internal Friction Angle (θi) experimentally:
𝜏 = 0.5 𝜎1 − 𝜎3 sin 2𝛽
𝜎𝑛 = 0.5 𝜎1 + 𝜎3 + 0.5 𝜎1 − 𝜎3 cos 2𝛽
S0
μ
θ
𝜇𝑖 = tan θ

44. ©DSB2023
47
Internal friction angle (i) from log data
𝜃𝑖 = sin−1
𝑉
𝑝 − 1000
𝑉
𝑝 + 1000
Shale
Lal, 1999
𝜃𝑖 = 57.8 − 105𝜙
Sandstone
Weingarten & Perkins, 1995
Shaley Sedimentary Rocks
Chang et al., 2006
𝜃𝑖 = 𝑡𝑎𝑛−1
𝐺𝑅 − 𝐺𝑅𝑠𝑎𝑛𝑑 𝜇𝑠ℎ𝑎𝑙𝑒 + 𝐺𝑅𝑠ℎ𝑎𝑙𝑒 − 𝐺𝑅 𝜇𝑠𝑎𝑛𝑑
𝐺𝑅𝑠ℎ𝑎𝑙𝑒 − 𝐺𝑅𝑠𝑎𝑛𝑑
μ = Internal friction coefficient
Chang C, Zoback MD, and Khaksar A (2006) Empirical relations between rock strength and physical properties in sedimentary rocks. Journal of Petroleum Science and
Engineering 51, pp. 223-237.
Lal M (1999) Shale stability: drilling fluid interaction and shale strength. SPE Latin American and Caribbean Petroleum Engineering Conference held in Caracas, Venezuela.
Weingarten JS and Perkins TK (1995) Prediction of sand production in gas wells: methods and Gulf of Mexico case studies. J. Petrol. Tech. 596–600..

45. ©DSB2023
48
Rock strength
HIGHLY COMPLEX for rocks!
Simple strength analysis
Complex strength analysis
Disagreements: dependency scale of tensile strength, time-dependent failure, etc.
UCS
✓ 3D stress state
✓ High temperature
✓ Pore pressure change
✓ “Creep” (time-dependent)

46. ©DSB2023
49
Example of rock strength test
UCS
Uniaxial Compressive Strength
Unconfined Compressive Stress
Thick-Walled Cylinder

47. ©DSB2023
50
Other tests for rock strength
✓ Triaxial Tests (Multi or Single-Stage)
✓ Tensile Strength Tests (Brazilian test)
✓ Differential Strain Analysis (DSA, DSCA)
✓ Compressibility Tests
✓ Acoustic Velocity Tests

48. ©DSB2023
Rock failure → break down of a rock a.k.a. broken rock
➢ Mostly based on peak stress of triaxial test curve.
➢ Prediction of failure in other geometries is based on criteria derived from several
triaxial tests → not always valid → i.e. thick-walled cylinder test.
➢ Failure stress for a solid cylinder under ambient pressure is the UCS
(Unconfined/Uniaxial Compressive Test)
➢ Commonly measures the strength of rocks.
➢ Failure is generally violent and easy to define.
➢ The rock deformation/failure pattern depends on the stress concentration and rock
strength.
EFFORT RESISTANCE
51

49. ©DSB2023
52
Effective Stress → cause of rock failure
σ Pp+ σ′
σ′ =
σ1 −Pp 0 0
0 σ2 −Pp 0
0 0 σ3 −Pp
Effective stress tensor
Total Stress σ
Effective Stress 𝝈′ = 𝝈 − 𝑷𝒑
Rock failure occurs due to the effective
stress and not the total stress
(Handin & Hager Jr., 1957)
Handin J and Hager Jr RV (1957) Experimental deformation of sedimentary rocks under confining pressure: Tests at room temperature. AAPG Bulletin 42(12): 2892-2934.

50. ©DSB2023
Rock strength around the wellbore
Wiebols G and Cook N (1968) An energy criterion for the strength of rock in Polyaxial compression. International Journal of Rock Mechanics and Mining Sciences and
Geomechanics Abstracts, 5 (6): 529–549
53
Effective axial stress
(parallel to wellbore trajectory)
σz
Effective radial stress
(acting along the radius of the wellbore)
σr
Effective Hoop stress
(perpendicular to wellbore wall)
σθ
UCS CSw BCS
Near wellbore stresses:
When drilling in balance:
σr ≈ 0
σz ≠ 0
σθ ≠ 0
Wiebols & Cook (1968)
𝐁𝐂𝐒 = 𝐔𝐂𝐒 𝟏 − 𝟎. 𝟔𝝁

51. ©DSB2023
54
Compressive and Tensile Strength
Compressive stress compressive strength
→ compressive (shear) fail
Log-based strength estimates can
be valid if they are calibrated
→ dynamic vs. static
Tensile strength compressive strength,
sometimes can be assumed as zero
(After Artuso and Lukiantchuki, 2019)
(After Sayers et al., 2016)
(After Johnson and DeGraff, 1988)

52. ©DSB2023
Rock Deformation – Constitutive Laws
1 Linear elastic models
2 Poroelastic models
3 Elasto-plastic models
5 Poro-viscoelastic models
Constitutive laws for rock deformation:
Constitutive laws describe deformation of the rock under applied stress.
4 Poro-elastoplastic models
55
“Traditional/Simple” geomechanics
Poroelasticity
Porosity
Permeability
“Sandstone & Carbonates” deformation
Some “Shale” deformation

53. ©DSB2023
56
Failure criteria → laws used to predict rock failure
Failure criteria Describe compressive (shear) failure
Unfortunately, models are almost never practical in most case studies!
Objectives:
Primary → To identify rock strength contrasts
Secondary → To describe rock strength using advanced failure criteria
Commonly used parameters:
✓ UCS
✓ Tensile strength
✓ Friction angle
✓ Cohesion

54. ©DSB2023
57
Failure criteria for rock materials
Wellbore instability Rock formation failure
To understand a failure phenomenon, needs a
specific and compatible failure criterion
For example: sand fail in shear, clay fail due to
plastic deformation
Some mechanisms:
✓ Tensile failure → loss circulation
✓ Shear failure → wellbore collapse
✓ Plastic deformation → pore collapse
✓ Cohesive failure → erosion
✓ Creep failure → time-dependent instability
✓ Comprehensive failure → usually during production

55. ©DSB2023
58
Failure criteria
Many failure envelopes
Stress
Strain
Commonly used failure criteria:
✓ Coulomb
✓ Mohr-Coulomb
✓ Griffith
✓ Griffith-Coulomb
✓ Von Misses
✓ Tresca
✓ Drucker & Prager
✓ Hoek & Brown
✓ Wiebols & Cook/Modified Wiebols & Cook
✓ Lade/Modified Lade
✓ Mogi-Coulomb

56. ©DSB2023
59
The Linearized Mohr failure envelope
●
●
●
Easier to measure!
2β
θ
S0 = Cohesive
σ
τ
Shear
stress
Effective normal stress
C0 = UCS
μi = internal friction coefficient
σ1
σ3
IFA
τ = S0 + μiσn C0 = 2S0 𝜇𝑖
2
+ 1 Τ
1 2
+ 𝜇𝑖 𝜇𝑖 = tan θ
(Modified from Zoback, 2007)
Zoback M (2007) Reservoir Geomechanics. Cambridge University Press, Cambridge New York, USA.
Failure criteria

57. ©DSB2023
60
Failure criteria for Sandstone
Mogi-Coulomb
Mohr-Coulomb
Hoek-Brown
Drucker-Prager
Modified Lade
(Modified from Zhang et al., 2016)
Zhang R, Shi X, Zhu R, Zhang C, Fang M, Bo K and Feng J (2016) Critical drawdown pressure of sanding onset for offshore depleted and water cut gas reservoirs: Modeling and
application. Journal of Natural Gas Science and Engineering 34:159-169

58. ©DSB2023
61
Failure criteria for Sandstone
Mogi-Coulomb
Mohr-Coulomb
Hoek-Brown
Drucker-Prager
Modified Lade
Underestimate
Highly underestimate
Overestimate
A bit overrated
(Modified from Zhang et al., 2016)
Zhang R, Shi X, Zhu R, Zhang C, Fang M, Bo K and Feng J (2016) Critical drawdown pressure of sanding onset for offshore depleted and water cut gas reservoirs: Modeling and
application. Journal of Natural Gas Science and Engineering 34:159-169

59. ©DSB2023
Modified Lade
62
Failure criteria for carbonate
Modified Wiebols & Cook
Mohr-Coulomb
Hoek-Brown
Drucker-Prager
Mogi 1967 & 1971
(Modified from Colmenares & Zoback, 2002)
Colmenares LB and Zoback MD (2002) A statistical evaluation of intact rock failure criteria constrained by polyaxial test data for five different rocks. International Journal of
Rock Mechanics & Mining Sciences 39:695-729

60. ©DSB2023
Modified Lade
63
Failure criteria for carbonate
Modified Wiebols-Cook
Mohr-Coulomb
Hoek-Brown
Drucker-Prager
Mogi 1967 & 1971
Overestimate
Overestimate
Overestimate
Underestimate
(Modified from Colmenares & Zoback, 2002)
Colmenares LB and Zoback MD (2002) A statistical evaluation of intact rock failure criteria constrained by polyaxial test data for five different rocks. International Journal of
Rock Mechanics & Mining Sciences 39:695-729

61. ©DSB2023
64
Simple Breakout (Collapse) Pressure Calculation
𝐏𝐂 =
𝟑𝐒𝐇𝐌𝐚𝐱 − 𝐒𝐡𝐦𝐢𝐧 − 𝐔𝐂𝐒 + 𝐐 − 𝟏 𝛂𝐏𝐩
𝐐 + 𝟏
UCS =
2C cos θi
1 − sin θi
Q =
1 + sin θi
1 − sin θi
θi = sin−1
Vp − 1
Vp + 1
Where:
PC Collapse (Breakout) Pressure
SHMax Maximum Horizontal Stress
Shmin Minimum Horizontal Stress
UCS Uniaxial Compressive Strength
α Biot’s Coefficient
Pp Pore Pressure
C Cohesion of rock
θi Internal Friction Angle (IFA)
Vp Compressive Velocity
Zoback MD, Moos D, Mastin L & Anderson RN (1985) Wellbore breakouts and in-situ stress, J. Geophys. Res., 90, 5523

62. ©DSB2023
65
Leak Pressure (or Fracture Pressure) → tensile failure
Geomechanics → Leak pressure = seepage loss to partial loss during drilling operations, fracture
pressure = total loss (formation breakdown pressure)
Drilling Engineering → Fracture pressure = loss (seepage, partial loss or total loss)
Leak or fracture pressure = tensile failure → least principal stress → Shmin in normal regime
𝐒𝐡𝐦𝐢𝐧 =
𝛖
𝟏 − 𝛖
𝐒𝐯 − 𝛂𝐏𝐩 + 𝛂𝐏𝐩
Uniaxial strain theory with anisotropic poroelastic → linear elasticity, no tectonic stress, no
horizontal strain:
(Ahmed et al., 1991)
Anisotropic poroelastic with tectonic stress and horizontal strain:
𝐒𝐡𝐦𝐢𝐧 =
𝛎
𝟏 − 𝛎
𝐒𝐯 − 𝛂𝐏𝐩 + 𝛂𝐏𝐩 +
𝐄𝛆𝐲
𝟏 − 𝛎𝟐 +
𝛎𝐄𝛆𝐱
𝟏 − 𝛎𝟐 +
𝟏 + 𝛎𝐄
𝟏 − 𝛎𝟐 𝛂𝐭𝚫𝐓 (Blanton & Olson, 1999)
E → Young’s modulus
εx, εy → tectonic horizontal strain
αt → expansion thermal coefficient
ΔT → temperature change (temperature at depth – surface temperature)
Ahmed U, Markley ME, Crary SF (1991) Enhanced in-situ stress profiling with microfracture, core, and sonic-logging data. SPE Form Eval 6(02):243–251
Blanton TL, Olson JE (1999) Stress magnitudes from logs: effects of tectonic strains and temperature. SPE Reserv Eval Eng 2(1):62–68

63. ©DSB2023
66
Tensile, Shear and Compaction Failure – Summary
Ferrill DA, Smart KJ and Morris AP (2019) Fault failure modes, deformation mechanisms, dilation tendency, slip tendency, and conduits versus seals. The Geological Society
of London, Special Publications.
(After Ferril et al., 2019)
𝑇𝑑 =
𝜎1 − 𝜎𝑛
𝜎1 − 𝜎3
Dilation tendency: Slip tendency:
𝑇𝑠 =
𝜏
𝜎𝑛

64. ©DSB2023
67
(and STRAIN…)

65. ©DSB2023
68
Why do we need to understand stress and strain?
Understanding limitation
to make prediction.
✓ What is the safe mudweight to
drill the well?
✓ Is the fault stable, going to fail,
or to be reactivated?
✓ Is the top seal breached?
✓ Where is the direction of my
hydraulic fracture?
✓ Which fracture set is more likely
to be permeable?
✓ Is sand production (sanding)
going to impact on production?

66. ©DSB2023
69
Stress and Strain
Measure
✓ Stress
✓ Strain
✓ Rock properties
Observe
✓ Strain
✓ Failure
Model
✓ Stress
✓ Strain
✓ Failure

67. ©DSB2023
L
70
Stress and Strain
Stress:
Load (force) per unit area that tends to deform
the body on which it acts.
𝐅𝐨𝐫𝐜𝐞
𝐀𝐫𝐞𝐚
=
𝑭
𝑨
Stress unit = Pressure unit
Strain:
Ratio of the change in length of a material to
the initial unstressed reference length, or the
apparent change in the shape, volume or
length of object caused due to stress.
∆𝐋𝐞𝐧𝐠𝐭𝐡
𝐋𝐞𝐧𝐠𝐭𝐡
Strain is unitless
ΔL ΔL

68. ©DSB2023
71
Different types of stress
https://media1.shmoop.com/images/physics/forces/physicsbook_forces_graphik_35.png accessed 8 September 2021
compression tension bending torsion shear

69. ©DSB2023
Strain
Strain is a normalized deformation, simply the measure of how
much an object is stretched or deformed.
Lateral Strain:
1
1
11
x
u


=

Axial Strain:
3
3
33
x
u


=

73

70. ©DSB2023
Strain
1
3
31
x
u


 =
ij =
1
2
ui
xj
+
uj
xi








Shear Strain:
ij =
1
2
ui
xj
+
uj
xi








Volumetric Strain:
33
22
11
00 
+

+

=

74

71. ©DSB2023
Robert Hooke
75
Stress-Strain relationship
Stress
(σ)
–
Pa
Strain (ε)
Brittle
Strong, not ductile
Ductile
Plastic
Stress
(σ)
–
Pa
Strain (ε)
●
●
Rise
Run
Yield point
Yield strength
Ultimate strength
Strain hardening Necking
Fracture/failure
E Rise
Run
= ratio of stress to strain
For relatively small deformations of an object, the displacement or size of the
deformation is directly proportional to the deforming force or load.
Hooke’s Law Law of elasticity
1678
ut tensio, sic vis (“the extension is proportional to the force”)
𝑭𝒔 = 𝒌𝒙 k = stiffness, x = very small deformation
Young’s modulus (E) = slope =
(stiffness)
Elastic Plastic
Area under curve = absorbed energy
Depends on material

72. ©DSB2023
76
Stress – Basic
The stress at any point in an object, assumed as a continuum,
is completely defined by the nine stress components σij of a
second order tensor of type (2,0)
Introduced by Augustin-Louis Cauchy in 1827 → Cauchy stress
tensor
Cauchy A-L (1827) De la pression ou tension dans un corps solide [On the pressure or tension in a solid body]. Exercices de Mathématiques, vol. 2, p. 42
𝜎𝑧
x
z
𝜎𝑥
𝜎𝑦
Principal stress is the maximum normal stress
Principal plane defined by the principal stress is
perpendicular and acts as a free surface (no shear stress)
There are 3 principal stress axes. Each axis is orthogonal to
the other two.
y

73. ©DSB2023
77
Overburden stress (lithostatic pressure) → Sv
Air gap = 14.7 psi
Water depth
Formations
“Overburden stress is the pressure exerted on a
formation at a given depth due to the total weight of the
rocks and fluids above that depth.” – Peter Aird
(After Zhang, 2013)
𝑺𝒗−𝒛 = 𝑷𝟎 + 𝒈 න
𝟎
𝒛
𝝆 𝒛 𝒅𝒛
𝐎𝐁𝐆 = 𝟎. 𝟒𝟑𝟑 𝟏 − 𝝓 𝝆𝒎 + 𝝆𝒇𝝓
Where:
Sv-z = Lithostatic Pressure at depth z, psi
(overburden/vertical stress)
OBG = Overburden gradient, psi/ft
P0 = Datum pressure, i.e. surface pressure, psi
ρ(z) = Overlying rock density at depth z, g/cm3
ρm = Matrix density, g/cm3
ρf = Fluid density, g/cm3
𝜙 = Porosity, fraction
g = Gravity acceleration
Referred as vertical stress (Sv)
in geomechanics

74. ©DSB2023
Horizontal Stresses – Poroelastic Model
𝝈𝒉𝒎𝒊𝒏 =
ν
𝟏 − ν
∙ 𝝈𝒗 − 𝜶𝑷𝒑 +
𝑬
𝟏 − ν𝟐
∙ 𝜺𝒉𝒎𝒊𝒏 +
𝑬ν
𝟏 − ν𝟐
∙ 𝜺𝑯𝑴𝒂𝒙 + 𝜶 ∙ 𝑷𝒑
Component from vertical load (ν) Tectonic component (E)
𝝈𝑯𝑴𝒂𝒙 =
ν
𝟏 − ν
∙ 𝝈𝒗 − 𝜶𝑷𝒑 +
𝑬
𝟏 − ν𝟐
∙ 𝜺𝑯𝑴𝒂𝒙 +
𝑬ν
𝟏 − ν𝟐
∙ 𝜺𝒉𝒎𝒊𝒏 + 𝜶 ∙ 𝑷𝒑
78
Thiercelin MJ, and Plumb RA (1994). A Core-Based Prediction of Lithologic Stress Contrasts in East Texas Formations. SPE Formation Evaluation, 9(04), 251–258
(After Thiercelin & Plumb, 1994)
Poroelastic component (α)

75. ©DSB2023
79
Minimum Horizontal Stress (Shmin) Estimation
Direct measurements:
✓ Leak-off and Extended Leak-off Tests (LOT and XLOT)
✓ Micro-hydraulic fracturing
Indirect measurements:
✓ Pore pressure (lower bound)
✓ Mud loss data
✓ Wellbore deformation
✓ Rock properties (lower bound
✓ Geomechanical modeling

76. ©DSB2023
80
Maximum Horizontal Stress (SHMax) Estimation
Direct measurements?

77. ©DSB2023
81
Maximum Horizontal Stress (SHMax) Estimation
Indirect measurements:
✓ Sonic scanner (LWD or wireline)
✓ Break down pressure interpretation → hydraulic fracturing
✓ Wellbore deformation modeling
✓ Rock properties constraint (upper bound)
✓ Geomechanical modeling

78. ©DSB2023
83
Andersonian Classification
3 Stress Regimes
Normal Fault Regime Strike Slip Fault Regime Reverse Fault Regime
Anderson EW (1951) The Dynamics of Faulting and Dyke Formation with Applications to Britain, 2nd ed. Oliver and Boyd, Edinburgh, UK. 206 pp.
Sv > SHMax > Shmin SHMax > Sv > Shmin SHMax > Shmin > Sv

79. ©DSB2023
Fundamentals Concept of Wellbore Stability
84

80. ©DSB2023
85
Wellbore Stability Workflow
Density
OBG (Sv)
Pp analysis
Interpreted Pp
Pfrac
Calibrate to LOT
Interpreted Pfrac
Calculate SHMax
Interpreted PC
Stable Mudweight Window
Calculate IFA (θi)
Calculate UCS
Calculate Q
Validate with
caliper log
Sen S, Kundan A, and Kumar M (2020) Modeling Pore Pressure, Fracture Pressure and Collapse Pressure Gradients in Offshore Panna, Western India: Implications for Drilling
and Wellbore Stability. Natural Resources Research, International Association for Mathematical Geosciences 01 January. DOI: 10.1007/s11053-019-09610-5
(Modified from Sen et al., 2020)
𝑄 = Τ
1 + sin 𝜃𝑖 1 − sin 𝜃𝑖

81. ©DSB2023
Mud Weight Window – Geomechanics Perspective
Borehole Geometry
“STABLE WINDOW”
“SAFE WINDOW”
PPore PFrac
Shmin
Relative Mud Weight or ECD High
Low
Severe
Compressional
Failure
Kick
Borehole
Breakout
Good and
Stable
Wellbore
Mud loss
High angle
shear failure
DITF
Breakdown
Loss Circulation
Seepage and
partial loss
Breakout
Collapse
SFG
Tensile failure
Shear failure
86
Breakdown
Drilling
Geomechanics
Kick Loss Circulation
Total loss

82. ©DSB2023
Mud Weight Window
Kick
Seepage Loss
Breakdown
Breakout
87
©Schlumberger

83. ©DSB2023
Wellbore instability indicators
88
Direct Indicators
High torque and drag (friction)
Hanging up of drillstring, casing, or coiled tubing
Increased circulating pressures
Stuck pipe
Excessive drillstring vibrations
Drillstring failure
Deviation control problems
Inability to run logs
Poor logging response
Annular gas leakage due to poor cement job
Keyhole seating
Excessive doglegs
Indirect Indicators
Oversize hole
Undergauge hole
Excessive volume of cuttings
Excessive volume of cavings
Cavings at surface
Hole fill after tripping
Excess cement volume required

84. ©DSB2023
89
Identifying Wellbore Failure on the Rig
Evidence of geomechanical problems:
❖ Large volume of cavings across the
shakers
❖ Operational problems:
➢ Tight hole (need to ream constantly)
➢ Stuck pipe
➢ Pack-off
➢ Fill on the bottom of the hole
➢ Trouble running casing, logging tools,
drill string
➢ Excessive mud losses

85. ©DSB2023
90
Wellbore instability – Mitigation
Preventing wellbore
instability
1
Limiting failure of the
formation
2

86. ©BP
Somewhere in Gulf of Mexico

87. ©DSB2023
92
Drilling into shale → Shale characteristics
Lamination
Clay content
Extremely low permeability
In tectonic environment
Strength anisotropy
Reactive, swelling, weakening
Pore pressure storage
Micro-fractured
Shale is more susceptible to failure → ~75% of wellbore instability challenge

88. ©DSB2023
93
Shale instability
Shale instability
Mechanical
Physico-
Chemical
Time independent Time dependent
Related to drilling
operations, mud weight,
wellbore stresses, rock
strength
Shale-WBM interaction →
swelling shale → reduced
wellbore strength → bit
balling, sloughing, pack
off, stuck pipe, loss of well

89. ©DSB2023
94
Shale instability mechanisms
✓ Pore pressure
diffusion
✓ Plasticity
✓ Anisotropy
✓ Capillary effects
✓ Osmosis
✓ Physicochemical
alterations
1. Movement of fluid
between interlayers
of shales
2. Changes within the
stress and strain
regime during
filtration
3. Softening and
erosion caused by
mud invasion
Hydrable (swelling)
shale
Brittle shale
Abnormally
pressurized shale
Tectonically stressed
shale
Gholami R, Elochukwu H, Fakhari N, and Sarmadivaleh M (2018) A review on borehole instability in active shale formations: Interactions, mechanisms and inhibitors. Earth-
Science Review 177:2-13
(Adapted from Gholami et al., 2018)

90. ©DSB2023
95
Signs of Chemically Unstable Shale
➢ Increase in cavings volume
➢ Drill cutting samples are “mushy” and rounded
➢ Tight hole
➢ Gradually torque increases
➢ Bit balling, BHA balling
➢ ECD increases
➢ Usually in WBM
➢ Changes in mud system properties, rheology, solid
content and type

91. ©DSB2023
Chemical wellbore instability
Failure: Due to stress and time-dependent swelling and/or water penetration into and out of
shale. Gumbo shales typically comprise a high proportion of smectite-rich clays. This clay
mineral tends to swell and become soft and sticky when exposed to water, particularly water in
the drilling fluid that has a lower salt concentration than that occurring in-situ.
Mud Type: ‘Swelling shales’ – water-based mud worse than oil/synthetic-based mud. Osmotic
effect – oil/synthetic-based mud worse than water-based mud
Solutions: Raise mud weight, alter mud chemistry, change mud type
96

92. ©DSB2023
Chemo-Thermo-Poroelastic Concept
GEOMECHANICS
Force equilibrium
Hooke’s Law
GEOCHEMISTRY
Reaction kinetics
FLUID FLOW
Mass balance
Darcy’s Law
HEAT
TRANSPORT
Heat conservation
Fourier’s Law
Diagenesis
Pressure solutions
Advective heat transport
Density, Viscosity
(Modified from Gaucher et al. 2015)
Thermo-hydro-mechanical-chemo-poroelastic
concept
Time dependent???
+Chrono…
97
Chemical instability
Gaucher E, Schoenball M, Heidbach O, Zang A, Fokker PA, van Wees J-D, and Kohl T (2015) Induced seismicity in geothermal reservoirs: A review of forecasting approaches.
Renewable and Sustainable Energy Reviews 52:1473-1490
✓ nucleo (nuclear)
✓ electro (electric)
✓ magneto (magnetic)
PLUS

93. ©DSB2023
98
Expanding Clay – Haryana, India
https://www.linkedin.com/posts/geology-
science_geology-science-india-ugcPost-
6825060977558470656-eRzP, accessed 1 August 2021
Montmorillonite
(Smectite group) expands
due to water adsorption
(osmotic hydration)
(After van Oort 2003)

94. ©DSB2023
99
Time-dependent instability – The signs during drilling
http://www.drillingformulas.com/shale-instability-causes-stuck-pipe/
During drilling was fine, when not on bottom drilling and on trips:
✓ Torque and drag, overpull
✓ Standpipe pressure increases
✓ Present of cavings
✓ Drilling mud becomes thicker (PV and YP increase)
If not mitigated soon and properly….

95. ©DSB2023
100
Possible Causes of Time-Dependent Wellbore Failure – Summary
Can be avoided with proper mud composition
(membrane efficiency, mud activity)
Chemo-poroelastic effect in shales
Elevation near-wellbore pore pressure
due to mud pressure invasion
Proper mud formulation to avoid mud invasion,
avoid excessive overbalance
Formation damage due to dynamic
pressure changes
Avoid excessive swabbing pressures – PWD
measurements allow to better control bottom
hole pressure changes
Chemical alteration and weakening of
cementation bonds
Mud chemistry – lab tests of rock strength as a
function of mud exposure can be used to
calibrate mud properties
Activating slip on geological features
➢ Slip on weak bedding planes – especially
problematic with synthetic based mud
systems.
➢ Slip on pre-existing fractures and faults –
mostly problem for completion engineers
but can be problematic for drilling as well

96. ©DSB2023
Coupling Instability Mechanisms
101
Mechanical Hydraulic
Chemical
Thermal
Biot’s Poroelasticity
Strain
Pore pressure
Osmotic
pore
pressure
Thermal
strain
Chemical potential

97. ©DSB2023
102
Shale Poromechanics Coupling Mechanisms
Thermal gradient
Thermal stress
Seebeck effect
Thermo-osmosis
Soret effect
Fourier’s Law
Electrical
gradient
Chemical
gradient
Hydraulic
gradient
Heat transfer
Coupled
thermoelasticity
Thermal
filtration
Dufour effect Peltier effect
Electric current
Piezoelectric
effect
Streaming
potential
Diffusive current Ohm’s Law
Species transport
Strain-induced
adsorption
Streaming
current
Fick’s Law Electrophoresis
Fluid flow
Skempton’s
effect
Darcy’s Law Chemo-osmosis Electro-osmosis
Displacement
gradient
(solid strain)
Solid stress Hooke’s Law
Effective stress
principle
Adsorption-
induced stress
Piezoelectric
effect
Elasticity Poroelasticity Porochemoelasticity
Porochemoelectroelasticity Porochemoelectrothermoelasticity
(After Mehrabian et al. 2020)
Mehrabian A, Nguyen VX, and Abousleiman N (2020) Wellbore Mechanics and Stability Analysis, in Dewers T et al. (eds.) Shale: Subsurface Science and Engineering
Geophysical Monograph 245. John Wiley & Sons, Hoboken NJ 07030 USA

98. ©DSB2023
103
Coupling mechanisms for a fully coupled system in shales
Electrical
Chemical Hydraulics
Thermal
Mechanical
Thermo-electricity
Seebeck effect
Peltier effect
Electro-phoresis
Diffusion
current
Chemo-electricity
Chemical osmosis
Advection
Chemodynamics
Thermodynamics
Conduction
Heat
transfer
Thermo
osmosis
Convection
heat
transfer
Joule-Thomson
effect
(Modified from Rafieepour et al., 2015)
Rafieepour S, Jalayeri H, Ghotbi C, and Pishvaie MR (2015) Simulation of wellbore stability with thermo-hydro-chemo-mechanical coupling in troublesome formations: an
example from Ahwaz oil field, SW Iran. Arab Journal of Geoscience 8:379-396. Original Paper published in 27 September 2013.

99. ©DSB2023
104
Instability in sandstone
“V-shaped” breakout “Fracture-like” breakout
(After Wu et al., 2018)
Wu H, Zhao J, and Guo N (2018) Multiscale Insights Into Borehole Instabilities in High-Porosity Sandstones. Journal of Geophysical Research: Solid Earth, 123, 3450-3473.
Modeling approach using coupling FEM (Finite Element Method) and DEM (Discreate Element
Method) pioneered by Guo & Zhao (2014).
Most common → progressive shear failure High porosity sandstones → compaction bands
FEM → used to solve the boundary value problem, whereby different loading/stress paths can be applied
DEM→ computations to feed the global FEM computations to examine the effects of material properties
from the microscale (grain scale), while avoiding unphysical, mostly complicated phenomenological
constitutive assumptions in conventional continuum-based modelling approaches
Guo N and Zhao J (2014) A coupled FEM/DEM approach for hierarchical multiscale modelling of granular media. International Journal for Numerical Methods in Engineering,
99(11), 789–818.

100. ©DSB2023
105
Instability in carbonate
Reinecker J, Tingay M, and Müller B (2003) Borehole breakout analysis from four-arm caliper logs. Guidelines: Four-arm Caliper Logs. World Stress Map Project.
Talebi H, Alavi SA, Sherkati S, Ghassemi MR, and Golalzadeh A (2018) In-situ stress regime in the Asmari reservoir of the Zeloi and Lali oil fields, northwest of the Dezful
embayment in Zagros fold-thrust belt, Iran. Geosciences 106:53-56
Whaley J (2008) Improving Wellbore Stability. GEOExPro v.5 n.4, pp.58-61
(After Whaley, 2008)
(After Reinecker et al., 2003)
(Modified from Talebi et al., 2018)

101. ©DSB2023
106
Challenging Wells
➢Deepwater wells
➢Depleted reservoir wells
➢Deviated, Horizontal, Extended Reach wells
➢HPHT wells
➢Combination of the above wells

102. ©DSB2023
107
Lost Circulation – Possible Mechanisms
(After Magzoub et al., 2019)
Magzoub, M.I., Salehi, S., Husein, I.A., and Nasser, M.S. (2019) Loss circulation in drilling and well construction: The significance of applications of crosslinked polymers in
wellbore strengthening: A review, Journal of Petroleum Science and Engineering PETROL 106653

103. ©DSB2023
108
Lost Circulation – Diagnostic Mechanisms
(Modified from Lavrov, 2016)
Lavrov A. (2016) Loss circulation. Mechanisms and Solutions. Elsevier. Kidlington, Oxford, UK.
Mechanisms Diagnostic features
High-porosity rocks
Losses start gradually
Loss flow rates increase gradually and may then
gradually decrease as filter cake builds up
Vugular formations
Losses start suddenly
Impossible to cure with LCM
Losses in specific types of formations (carbonate,
karst)
Drill bit may drop a few meters when it hits the vugs
Natural fractures
Losses start suddenly as fractures are intersected by
the wellbore
Drilling-induced fractures
Losses often accompany pressure surges (e.g. when
running pipe in hole or starting the pumps)

104. ©DSB2023
109
Lost Circulation – Severity Levels
Seepage Losses
Static: 0.2 – 1.0 m3/hr
Dynamic: <10%
Partial Losses
Static: 1.0 – 10.0 m3/hr
Dynamic: 10 – 30%
Severe Losses
Static: >10.0 m3/hr
Dynamic: 60 – 95%
Total Losses
Dynamic: 95 – 100%

105. ©DSB2023
110
Lost Circulation – Preventive Action
✓ Identify potential loss/weak zone
✓ Monitor drilled formation closely when approaching loss/weak zone
✓ Add LCM as per recommended in drilling fluid system
✓ Use waiting method
✓ Reduce pump rate to minimum GPM for hole cleaning + 10%
✓ Reduce RPM to minimum for hole cleaning
✓ Reduce mud weight, increase drilling fluid viscosity,
✓ Use bit without nozzles.

106. ©DSB2023
111
Lost Circulation – Mitigations
Al-Hameedi A.T.T., Alkinani H.H., Dunn-Norman S., Flori R.E. and Hilgedick S.A. (2018) Real-time lost circulation estimation and mitigation. Egyptian Journal of Petroleum 27,
pp. 1227-1234.
(After Al-Hameedi et al., 2018)

107. ©DSB2023
112
Wellbore Strengthening
Controlled breakout
Fracture linking
Fracture plugging
Internal mud cake
Stress cage

108. ©DSB2023
2001
2001
113
Complex geologic conditions – BP Exploration Colombia, Cusiana Field
Challenges:
➢ Very bad wellbore instability issues
➢ Previous geomechanics model did not fit with actual
condition
Willson SM, Last NC, Zoback MD, and Moos D (1999) Drilling in South America: A Wellbore Stability Approach for Complex Geologic Conditions. SPE 53940
(After Willson et al., 1999)
(After Willson et al., 1999)

109. ©DSB2023
114
Complex geologic conditions – BP Exploration Colombia, Cupiagua Field
Willson SM, Last NC, Zoback MD, and Moos D (1999) Drilling in South America: A Wellbore Stability Approach for Complex Geologic Conditions. SPE 53940
Planned:
Revisited/reassessed geomechanics model
Findings:
✓ Strike-slip regime
✓ Laminated sand-shale sequence
✓ Anisotropic rock strength
✓ Weak bedding plane

110. ©DSB2023
115
Complex geologic conditions – BP Exploration Colombia, Cupiagua Field
Willson SM, Last NC, Zoback MD, and Moos D (1999) Drilling in South America: A Wellbore Stability Approach for Complex Geologic Conditions. SPE 53940
Planned:
Revisited/reassessed geomechanics model
Findings:
✓ Strike-slip regime
✓ Laminated sand-shale sequence
✓ Anisotropic rock strength
✓ Weak bedding plane
Mitigation:
✓ Trajectory optimization
✓ Wellbore strengthening technique for
weak formation
✓ Drilling optimization with downhole drilling
parameters sensor (LWD) tool
Result:
✓ Reduced NPT to minimum
✓ Save total drilling cost with shorter drilling time

111. ©DSB2023
116
Benefits of Geomechanics Study
Lower exploration risks
Improved drilling performance
Drilling safety
Save drilling CO$T
Reduce or eliminate NPT

112. ©DSB2022
George E.P. Box (1919 – 2013), a British Statistician
All models
are wrong,
some are
useful…
1976
117
Keep
It
Simple, and
Smart

113. ©DSB2023
Last one… Drilling success…?
Advanced
Geosciences
Advanced
Drilling Technology
118

114. ©DSB2023
Last one… Drilling success…?
Advanced
Geosciences
Advanced
Drilling Technology
119

115. ©DSB2022
END of Webinar – QUESTIONS?
120

116. ©DSB2022
121
Don Basuki
dsbasuki@gmail.com

117. ©DSB2022
Disclaimer
Copyright belongs to respected owners of the original slides
owners: Baker Hughes, GeoMechanics International, Ikon
Science, BRAVO GeoConsulting, Schlumberger, Pertamina
and others. All cartoon characters belong to their respective
copyright holders. No copyright infringement intended.
Other materials are taken from published papers, and cited
as such.
Slides are used in non-commercial, in house training in
scientific discussion.
122
Copyright Disclaimer under section 107 of the Copyright Act of 1976, allowance is made for “fair use” for purposes such as
criticism, comment, news reporting, teaching, scholarship, education and research.

118. ©DSB2022
123
Instructor – Don Basuki, MSc., CPG
An enthusiastic and highly motivated Certified Professional Geologist with a
wide range of worldwide experience in the petroleum exploration industry.
Don has nearly 30 years of industry experience in several countries with
various roles. Currently he’s an independent consultant for all geomechanics,
pore pressure, and drilling optimization projects. Has wide range of
experience in geomechanics and wellbore stability modeling using
petrophysical, drilling and geophysical data along with extensive wellsite
experience throughout many different geological environments such as
deepwater, extended reach drilling, HTHP, unconventional, and in complex
lithologies. Has various experiences in drilling engineering subjects such as
complex, multi-phase hydraulics analysis and calculation, casing design, well
trajectory design and drilling dynamics analysis. He was successfully involved
in some of record breaking projects, such as Poseidon (the deepest well in
Gulf of Mexico, 2001), Semberah-77 (the longest onshore horizontal well in
Indonesia, 2006) and Sakhalin-1 Z-12 Chayvo (the longest well in the world,
2008).
Enhancing this experience, Don is a certified OASIS Engineer in Pressure
Management and Performance Drilling. Don holds a Master of Science
degree in Structural Geology (1997) from Wichita State University, Kansas,
USA. Don was a recipient of various scholarships. He’s enjoying martial arts
and reading lots of books during his leisure times.
Speaker – Don Basuki, MSc., CPG