Use of Quantitative Risk Analysis Methods to Determine the
Expected Drilling Operating Window Prior to Operation Start
Eric Cayeux, IRIS
31 May 2017
Outline
1.Well construction life cycle
2.Risk based drilling operation plan
3.Type of risks
4.Factors Influencing a Drilling operations
5.Uncertainty Management and Propagation
6.Examples
7.Conclusion
Well Construction Life Cycle
Target
selection
Post Analysis
Well
Architecture
design
Well
Construction
Drilling
Engineering
Drilling
Operation
Planning
Well Construction Life Cycle
Target
selection
Post Analysis
Well
Architecture
design
Well
Construction
Drilling
Engineering
Drilling
Operation
Planning
Risk based drilling operation planning
A drilling operation plan:
• Is often a best case scenario with one or two
contingency plans
Risk based drilling operation planning
A drilling operation plan:
• Is often a best case scenario with one or two
contingency plans
• But in reality there is a lot of uncertainty
Risk based drilling operation planning
A drilling operation plan:
• Is often a best case scenario with one or two
contingency plans
• But in reality there is a lot of uncertainty
• Because of an uncertain geological
environment
• Structure and stratigraphy
• Geo-mechanics
Risk based drilling operation planning
A drilling operation plan:
• Is often a best case scenario with one or two
contingency plans
• But in reality there is a lot of uncertainty
• Because of an uncertain geological
environment
• Structure and stratigraphy
• Geo-mechanics
• That can lead to drilling incidents like
• Influx
• Wellbore instabilities
• Loss circulation
• And affect drilling performance (ROP)
Low pressure
Formation fluid influx
Low pressure
Formation collapse
High pressure
Formation fracturing
Risk based drilling operation planning
A drilling operation plan:
• Is often a best case scenario with one or two
contingency plans
• But in reality there is a lot of uncertainty
• Because of an uncertain geological
environment
• Because of variations around the initial
well design:
• Trajectory
• Drilling fluid
• Drill-string
• Sections’ TD
Risk based drilling operation planning
A drilling operation plan:
• Is often a best case scenario with one or two
contingency plans
• But in reality there is a lot of uncertainty
• Because of an uncertain geological
environment
• Because of variations around the initial
well design:
• Trajectory
• Drilling fluid
• Drill-string
• Sections’ TD
• That can impact:
• Performance
• Risk of drilling incidents
Spiraling due to
directional work
Direct straight
line from start to
end of section
Actual trajectory
Buckling
Stuck-pipe by tortuousity
Risk based drilling operation planning
A drilling operation plan:
• Is often a best case scenario with one or two
contingency plans
• But in reality there is a lot of uncertainty
• Because of an uncertain geological
environment
• Because of variations around the initial
well design
• Because of likely variations of
operational procedures
• Drilling parameters
• Connection procedures
Risk based drilling operation planning
A drilling operation plan:
• Is often a best case scenario with one or two
contingency plans
• But in reality there is a lot of uncertainty
• Because of an uncertain geological
environment
• Because of variations around the initial
well design
• Because of likely variations of
operational procedures
• Drilling parameters
• Connection procedures
• That impact
• Drilling performance
• Risk of drilling incidents
Cuttings beds
Large axial velocity
Pack-offs
Vibration
Risk based drilling operation planning
A drilling operation plan:
• Is often a best case scenario with one or two
contingency plans
• But in reality there is a lot of uncertainty with a
skewed distribution
• Ideally, we would like a drilling operation plan
that minimize risk and maximize performance
under the foreseeable uncertain conditions:
• This is an optimization problem
• The objective function is:
• Overall operation duration
• Drilling risk level
Type of risks
•Cuttings accumulation in beds
•High concentration of cuttings in suspension
(possible pack-off)
Along hole
depth (m)
Cuttings in
suspension
Cuttings in
bed
0
500
1000
1500
2000
2500
3000
3500
4000
4500
0
5
10 0
10
Proportion (%) Thickness (cm)
Type of risks
•Cuttings accumulation in beds
•High concentration of cuttings in suspension
(possible pack-off)
•Too low annulus pressure causing influx
•Too low annulus pressure causing hole
collapse
Collapse pressure
gradient or pore
pressure gradient
ECD
Hole collapse or influx
Type of risks
•Cuttings accumulation in beds
•High concentration of cuttings in
suspension (possible pack-off)
•Too low annulus pressure causing influx
•Too low annulus pressure causing hole
collapse
•Too high annulus pressure causing
formation fracturing
ECD
Fracturing pressure
gradient
Formation fracturing
Type of risks
•Cuttings accumulation in beds
•High concentration of cuttings in
suspension (possible pack-off)
•Too low annulus pressure causing influx
•Too low annulus pressure causing hole
collapse
•Too high annulus pressure causing
formation fracturing
•Too high hydrostatic pressure causing
permanent mud losses in case of fracturing
ESD
Min Hor. Stress
Risk of permanent mud losses
Type of risks
•Cuttings accumulation in beds
•High concentration of cuttings in suspension
(possible pack-off)
•Too low annulus pressure causing influx
•Too low annulus pressure causing hole
collapse
•Too high annulus pressure causing
formation fracturing
•Too high hydrostatic pressure causing
permanent mud losses in case of fracturing
•Drill-string buckling
Buckling limit
Tension along drill-string
Buckling
Type of risks
Pressure along drill-string
Max SPP
•Cuttings accumulation in beds
•High concentration of cuttings in suspension
(possible pack-off)
•Too low annulus pressure causing influx
•Too low annulus pressure causing hole collapse
•Too high annulus pressure causing formation
fracturing
•Too high hydrostatic pressure causing permanent
mud losses in case of fracturing
•Drill-string buckling
•Excessive pump pressure
Excessive pump pressure
Type of risks
•Cuttings accumulation in beds
•High concentration of cuttings in
suspension (possible pack-off)
•Too low annulus pressure causing influx
•Too low annulus pressure causing hole
collapse
•Too high annulus pressure causing
formation fracturing
•Too high hydrostatic pressure causing
permanent mud losses in case of fracturing
•Drill-string buckling
•Excessive pump pressure
•Excessive top-drive torque
Torque along drill-string
Max allowable torque
Excessive torque
Factors Influencing a Drilling operations
• Drilling parameters
• WOB/ROP
• Drill-string rotational speed
• Flow-rate
Influences:
• Cuttings production and transport
• Downhole pressures
• Temperature
• Torque
Drilling parameter domain that do not cause incidents
At start of section
At end of section
Uncertainty Management and Propagation
• Limits
• Pore pressure gradient
• Collapse pressure
gradient
• Min hor. Stress
• Fracturing pressure
gradient
17 ½ -in
Wellbore position
uncertainty
TD 17 ½ -in
12 ¼ -in
TD 12 ¼ -in
8 ½ -in
TD 8 ½ -in
Formation tops
Geo-pressure
limits
Uncertainty Management and Propagation
• Limits
• Performance
17 ½ -in
TD 17 ½ -in
Estimated ROP (P90)
12 ¼ -in
Top-drive speed (RPM)
Wellbore
position
uncertainty
TD 12 ¼ -in
8 ½ -in
ROP (m/h)
0,6
0,4
0,2
0
TD 8 ½ -in
Formation tops
Formation strengths
WOB (t)
0-0,2
0,2-0,4
0,4-0,6
Estimated ROP
Uncertainty Management and Propagation
• Limits
• Performance
• Temperature
17 ½ -in
Wellbore position
uncertainty
TD 17 ½ -in
Fluid thermo-physical
properties
12 ¼ -in
TD 12 ¼ -in
Estimated
temperatures
8 ½ -in
TD 8 ½ -in
Formation tops
Formation thermo-physical properties
Uncertainty Management and Propagation
•
•
•
•
Limits
Performance
Temperature
Estimated downhole
conditions
Example 1
• 12 ¼ section. 13 ½ enlargement.
• 4000mMD
Rheology
Shear Stress (lb/100ft2)
140
OBM 1
120
100
OBM 2
80
60
OBM 3
40
20
0
0
100
OBM #1
200
300
Fann 35 RPM
OBM #2
400
OBM #3
500
600
Example 1: Detailed analysis 1/3
OBM 1
Flow-rate vs RPM
cross section:
• Fixed WOB
• Start of section
OBM 3
Cuttings
transport
Cuttings
transport
Max SPP
Flow-rate
Limiting risks:
• Cuttings
transport
• Max. SPP
OBM 2
Cuttings
transport
RPM
RPM
WOB
Along depth projection:
• Flow-rate
• RPM
• WOB
• Two other parameters
fixed
Max. SPP
Flow-rate
Example 1: Detailed analysis 2/3
Cuttings
transport
Buckling
Mud 3 provides clearly
more operational
margins
RPM
Quick comparison of the
three mud systems
WOB
Along depth projections
Flow-rate
Example 1: Detailed analysis 3/3
OBM 1
OBM 2
OBM 3
Example 2
Section:
• 12 ¼ x 13 ½
Two DP alternatives
• 5 ½ inches
• 6 5/8 inches
Example 2: along depth projections
Flow-rate
Max. SPP
RPM
6 5/8 DP
Cuttings
transport
WOB
5 ½ DP
Buckling
Conclusion
• A method to estimate the risk level in drilling operational plan
• The presence of risks does not mean that the well cannot be drilled
• But an action plan should be ready to deal with the risk
• A method that accounts for problem description uncertainty
• Allow to evaluate which information matters to improve the control the risk
evaluation
• Either by acquiring more information or implementing better instrumentation
• A method that gives estimate of expected performance
Thank you
Any questions?