lesson 16 risk management and problems
TRANSCRIPT
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Harold Vance Department of Petroleum Engineering
Risk Management and
Downhole Problems
Risk ManagementRisk Identification
Quantitative Risk Analysis
Risk Mitigation Planning
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Downhole Problems andTroubleshooting
Wellbore Instability
Excessive Vibration
Fluid Influxes
Stuck Pipe and Fishing
Corrosion
Risk Management and
Downhole Problems
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Risk Management
A major success factor in UBD ishow effectively the designers andimplementers identify risks and
develop an effective plan to dealwith the risks.
Introduction
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Risk Management
Before implementing the finaldesign, the selected equipmentand operating procedures should
be subjected to an exacting riskanalysis.
Introduction
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Risk IdentificationQuantitative Risk Analysis
Risk Mitigation PlanningRisk Response
Risk Management
Stages
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Risk IdentificationQuantitative Risk Analysis
Risk Mitigation Planning
Risk Management
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Source of Risk.
Probability of Occurrence.Potential Impact.
Action to Mitigate.
Cost to Mitigate.
Probability Mitigation Succeeds.
Risk Identification
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Probability of Occurrence
Can be on a scale of:1 to 10 or
High, Medium, and Low
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Potential Impact
High, Medium, or Low.
May be referred to asConsequenceCan be defined by dollar amounts or
other criteria, such as severity ofinjuries or death, or any combination
of dollar amount and injury.Probability * Consequence = Risk
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Action to Mitigate
Next, the decision whether to live
with the risk or if risk mitigation isin order.
Mitigation involves reducing the
probability of occurrence or thepotential impact of a given risk.
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Risks can be mitigated by:
Choose substitute equipment types.
Upgrade specifications such as
materials strength, ratings, etc.Modify the basic design.
Transpose steps in the procedure.
Change mud systems, completionoptions, etc.
Include backup equipment.
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Cost to Mitigate
The relative cost to mitigatemust be estimated, based onrough approximations, in order
to evaluate the viability of themitigation actions.
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Probability MitigationSucceeds
Estimate the probabilitywill succeed.
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Risk Mitigation Table
Description of
Risk
Sourceof Risk
Probabilityof
occurrence
PotentialImpact
Action tomitigate
Cost toMitigate
ProbabilityMitigationSucceeds
Hurricane strikeswhile drilling andrequires shut downof operations
E Low Medium
Create plan fortemporary shut-inof well andabandonment ofoffshore platform.
Low High
Drill string failure I Medium Medium
Institute tubulartesting programthat includespressure testing
and magneticscanning of micro-fractures
Medium High
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Risk IdentificationQuantitative Risk Analysis
Risk Mitigation Planning
Risk Management
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Quantitative Risk Analysis
What is Uncertainty?
Risk Analysis and Decision-Making.What is Quantitative Risk Analysis?
When should I use Quantitative
Risk Analysis?Why should I use Quantitative riskAnalysis?
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What is Uncertainty?
Dictionary definition:
the estimated amount orpercentage by which an observed orcalculated value may differ from thetrue value
Benjamin Franklin pointed out:
In this world nothing can be said tobe certain, except death and taxes
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Risk Analysisand Decision-Making
Risk analysis and decision making arefundamentally related.
A key component of Risk Analysis isto provide support for a particulardecision.
In our industry, the decision that
requires risk analysis is usuallysubject to acceptance by a team oftechnical professionals and approvalby management.
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What isQuantitative Risk Analysis?
Any technique for analyzinguncertainty and quantifying theeffects of that uncertainty on
factors that will significantlyeffect decision making.
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A method of quantifying the consequencesof the risks identified by intuition through a
structured approach to decision makingbased on:
what you think you know and dont
know.What you can do.
What you want the outcome to be.
What isQuantitative Risk Analysis?
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When should I useQuantitative Risk Analysis?
Risk analysis can be usedthroughout an UB project toimprove the quality of technical
evaluations and improve riskmitigation techniques.
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Probabilistic methods providebetter decisions than deterministicmethods because a full range ofpotential outcomes is examined.
Why should I useQuantitative Risk Analysis?
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Quantitative Risk
AnalysisThe Process
Problem Identification.
Deterministic Analysis.
Probabilistic Analysis.
Evaluation andCommunication.
Decision and Action.
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Problem Identification
Identify the problem, the reason
that a solution is required, andproject desires.
Collect and review data.
Verify accuracy of data, and ensureit is pertinent to the issue at hand.
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Deterministic Analysis
Construct a model relating inputs
and possible outcomes.Perform a sensitivity analysis and
present the results in graphs and
tables.Identify key variables and examine
them in more detail.
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Probabilistic Analysis
Assign key variables a range andprobability distribution.
Conduct an assessment using
Monte Carlo simulation.
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Evaluation andCommunication
Check if the results make sense,determine if additional informationis needed, and create graphs andtables to communicate the results of
the analysis.
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Decision and Action
Recommend the best alternativeconsistent with the analysis andproject desires.
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How to do a HAZOP
HAZOP
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Essential Elements
Procedure/System Layout.
HAZOP Form.
Small Group.
Recorder.Co-ordinator.
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Conventional MudLift with SAC and DSV (SS Pump on Inlet Pressure)
Shut In-Drlg
1. Raise kelly/top drive until the drivebushing clears the rotary.
2. Stop pumps and check for flow.3. Open choke line fail safe valve (with
choke closed).
4. Close upper annular. (Someoperators may prefer to shut-in on
rams instead)
5. Check for leaks, notify supervisor,record SIDPP, SICP, Pit Gain, Time,
Date.6. Close upper pipe rams. (Depending
upon the stack, could be middle rams)7. Reduce closing pressure on upperannular, and lower drillstring untiltool joint rests on closed upper pipe
ram.8. Open upper annular and restore
closing pressure to normal.9. Prepare for kill.
1. Raise kelly/top drive until the drive bushing clears the rotary.2. Isolate SAC from wellbore.3. Stop rig pumps (DP pressure falls to DSV opening pressure); SS pump maintains
seawater hydro. If SS pump keeps running, well flow is verified.4. Stop subsea pump. Record SS inlet pressure (excess above sea hydro is SICP.)
Pump slowly on DP until pressure flattens (DSV opens). SIDP is increase above
pre-recorded DSV opening pressure.
5. Close upper annular. (Some operators may prefer to shut-in on rams instead)6. Check for leaks, notify supervisor, record SIDPP, SICP, Pit Gain, Time, Date.7. Close upper pipe rams. (Depending upon the stack, could be middle rams)8. Reduce closing pressure on upper annular, and lower drillstring until tool joint
rests on closed upper pipe ram.
9.
Open upper annular and restore closing pressure to normal.10.Prepare for kill.Discussion:
The use of the DSV will allow faster shut in and flow measurements. Closure of the DSV after mud circulation is stopped will make measurement of SIDPP
more complicated.
There must be a means of isolating the SAC from the wellbore pressures upon shut-in. Isolation of SAC will slightly complicate the shut-in procedure relative to
conventional riser drilling.
Procedure
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System Layout
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Date: ______________
HAZOP(RISK ASSESSMENT)
WC-1_
MUDLIFT MODE: WC-1 Drilling with SAC and DSV with Shut-In (Base Case) Page: ofACTIVITY: Kick Detection, Stop Flow/Shut-In, Measurement, Drillers Method
REASON: Probably preferred MODE and procedures for most participants
ASSUMPTIONS: Hangoff @ SI; SS Pump on Inlet Pressure = Sea Hydro Before Kick; DSV set for Positive Opening Pressure
Probability (H,M,L) RISKHazard Consequence (H,M,L) Existing Safeguards
Avg C x P
Shut-In, Pit Gain,
SIDP, KCP, DP Sch.
Description
1.2.3.4.5.6.7.8.9.10.11.12.Put Participants names in shaded boxes for individual assessment of Probability. Put weighted Average in Avgcolumn.
HAZOP Form
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Small Group
Large groups unwieldy.
4 to 8 about right.
All should take active part.
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Recorder
Act as Wordsmith.
Good with a Laptop.
LCD Projector handy.
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Co-ordinator
Familiar with HAZOP process.
Monitors discussion.
Keeps focus.
Dampens noise level.Helps Recorder.
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What-If for Hazards
Unobserved Event.
Equipment Failure.
Unworkable Procedure.
Unrealized Expectation.
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With a Hazard Named:
Figure Out Consequences.
Decide Probability.
Calculate Risk.
Stick to Agreed Definitions.
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Consequence Effect
HIGH
Fatality
Or
Damage $ 1-10 MM
MEDIUM
LTI-Disability
Or
Damage $ 25K-1 MM
LOW
Non-LTI Injury
Or
Damage < $ 25K
NOTE: These are possible consequences of hazards that can develop even with existing Safeguards inPlace prior to modifications resulting from the HAZOP.
Qualify Consequence
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RISK MATRIX
PROBABILITY
LOW MEDIUM HIGH
CONSEQUENCE
HIGH H*L = M H*M = M H*H = H
MEDIUM M*L = L M*M = M M*H = M
LOW L*L = L L*M = L L*H = L
For Well Control, Risk must be at Low Level.
Risk = Consequence*Probability
Risk
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With Risks Assessed
Fill Out the Form.Final Entries inRiskColumn.
OnlyLowRisks Acceptable.
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Now What?
Here
Wrap it up!!Real World
Three more steps.
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Final Steps
MitigationRevised Risk
Proposed Action
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Slow process.
Both constructive & destructive.
Side issues can mess it up.
Probably not right the first time.Consequence vs. Catastrophe.
Perils & Pitfalls
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Problem withQuantitative Risk Analysis
Determining the probabilities.
Mis-understanding of the innerworkings of the model.
Lack of reality checks.
Ignoring relationships betweenvariables.
Use of subjective judgments.
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Risk IdentificationQuantitative Risk Analysis
Risk Mitigation Planning
Risk Management
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Risk Mitigation Planning
Risk Mitigation Plan
Risk Response
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Risk Mitigation Plan
Should be incorporated into theindividual well program for each well.
Should include a brief description ofthe operations risks identified andanalyzed in the previous phases and
suggested mitigation measures thatwere derived.
Keep is simple.
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The plan should include:
Emergency phone numbers.
Engineering drawings andsketches.
Risk mitigation procedures.
Risk Mitigation Plan
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Risk Response
Field personnel must be ready toimplement emergency responses.
Inspections, audits and field visitswill assist in ascertaining theability of operations personnel torespond to a particular risk.
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Downhole Problems andTroubleshooting
Wellbore Instability
Excessive VibrationFluid Influxes
Stuck Pipe and FishingCorrosion
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Wellbore Instability
Causes of Instability
Symptoms
Prevention
Solutions and Treatments
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Causes of Instability
Mechanical - Most are related to mudweight, more specifically, to mud
weight reduction while attempting toget underbalanced.
Abnormal pressure, tectonic stress,
and unconsolidated formations areall causes of mechanical wellboreinstability.
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Chemical - related to reactivityof shale and/or clay that may bepresent in other formations.
Most causes by exposure to freshwater.
Causes of Instability
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Symptoms
Most symptoms are due to rock failureand excessive amounts of formation in
the wellbore. Include:
increased torque/drag.
increase fill on bottom duringconnections/trips.
increased annular pressure.
excessive cuttings at the surface.
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Prevention
Determine the cause.Adequate mud density.
Proper chemical make-up of
the drilling fluid.
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Solutions and Treatments
Increase circulation rate.
Keep pipe moving at all times.
Use inhibitive fluids.
h l bl d
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Downhole Problems andTroubleshooting
Wellbore Instability
Excessive VibrationFluid Influxes
Stuck Pipe and Fishing
Corrosion
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Excessive Vibration
Causes of Excess Vibration.
Symptoms of Vibration.
Prevention and Solution to
Excessive Vibration.
C f E
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Causes of ExcessVibration
Drilling rough, highly fractured orabrasive rocks.
Hard rocks.
Improper handling of percussiontools.
Gas drilling does not dampenvibrations as much as liquids.
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Symptoms of Vibration
Drillstring damage noticed throughinspection.
High incidence of downhole toolfailure.
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Prevention and Solution to
Excessive VibrationKeep the drillpipe in tension.
All compressive forces should becontained in the BHA.
Calculate the neutral point so thatwhen the maximum WOB isapplied, the neutral point is in theBHA.
D h l P bl d
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Wellbore Instability
Excessive VibrationFluid Influxes
Stuck Pipe and FishingCorrosion
Downhole Problems andTroubleshooting
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Fluid Influxes
Causes
Symptoms of Unwanted Influxes
Prevention of Influxes
Solutions to Unwanted Influxes
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Causes
Major cause is UBD.
Three requirements for influx.some measurable porosity.
Permeability.
wellbore pressure < formationpressure.
Symptoms of
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Symptoms ofUnwanted Influxes
Fluids being returned to the surface thatare not pumped into the wellbore.
Damp cuttings when drilling with drygas.
Reduction in the number of cuttings at
the surface. Increased injection pressure.
Loss of returns.
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Prevention of Influxes
Only real prevention is to drill
overbalanced.
But this is not possible if ourgoal is to purposefully drillunderbalanced.
Solutions to
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Solutions toUnwanted Influxes
Control influx rate.
When drilling with gas or air,
attempt to unload the liquids fromthe hole. May require a switch tomist drilling.
Increase EMW in stages.
Carefully weighting up the system.
Do hole P oble d
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Wellbore Instability
Excessive VibrationFluid Influxes
Stuck Pipe and Fishing
Corrosion
Downhole Problems andTroubleshooting
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Stuck Pipe and Fishing
Causes
Symptoms
Prevention
Solutions
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Causes
All causes of stuck pipe can
occur during UBD exceptdifferential sticking.
Keyseating.
Excessive cuttings due towellbore instability.
Mud rings.
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Symptoms
Cannot pick up the drillstring.
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Prevention
Proper design of thedrillstring.
Adequate hole cleaning.
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Solutions
Fishing.
Downhole Problems and
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Wellbore Instability
Excessive VibrationFluid Influxes
Stuck Pipe and FishingCorrosion
Downhole Problems andTroubleshooting
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Corrosion
Requirements for Corrosion.
Causes and Factors EffectingCorrosion.Symptoms.Prevention.Solution.
Requirements for
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Requirements forCorrosion
Requires the presence of four
components:an anode (component that corrodes).
a cathode.
an electrolyte.an external connection.
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Simple Corrosion Cell
Causes and Factors
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Causes and FactorsEffecting Corrosion
Fluid utilized is the single largestsource of corrosion. The fluidbecomes the electrolyte.
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Corrosion Rate Factors
Oil content.
Conductivity of electrolyte.
pH of the fluid. Temperature and Pressure.
Fluid velocity.
Bacteria.
Internal and External stressconcentrations.
Presence of dissimilar metals.
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Symptoms
Generalized corrosion.Pitting.
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Prevention
Corrosion cannot be stopped,but it can be slowed.
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Solution
Avoidance
Inhibition
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END