PETE 689 UBD

1
PETE 689 - UBD

• Lesson 16
• Risk Management and
• Downhole Problems

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Risk Management and Downhole Problems

• Risk Management
• Risk Identification
• Quantitative Risk Analysis
• Risk Mitigation Planning

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Risk Management and Downhole Problems

• Downhole Problems and Troubleshooting
• Wellbore Instability
• Excessive Vibration
• Fluid Influxes
• Stuck Pipe and Fishing
• Corrosion

4
Risk Management
Introduction

• A major success factor in UBD is how effectively
  the designers and implementers identify risks and
  develop an effective plan to deal with the risks.

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Risk Management
Introduction

• Before implementing the final design, the
  selected equipment and operating procedures
  should be subjected to an exacting risk analysis.

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Risk Management
Stages

• Risk Identification
• Quantitative Risk Analysis
• Risk Mitigation Planning
• Risk Response

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Risk Management

• Risk Identification
• Quantitative Risk Analysis
• Risk Mitigation Planning

8
Risk Identification

• Source of Risk.
• Probability of Occurrence.
• Potential Impact.
• Action to Mitigate.
• Cost to Mitigate.
• Probability Mitigation Succeeds.

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Source of Risk

• Internal risks that the designer can control.
• External risks that the designer cannot
  control.

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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 as Consequence
• Can be defined by dollar amounts or other
  criteria, such as severity of injuries 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 is in order.
• Mitigation involves reducing the probability of
  occurrence or the potential impact of a given
  risk.

13
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, completion options, etc.
• Include backup equipment.

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Cost to Mitigate

• The relative cost to mitigate must be estimated,
  based on rough approximations, in order to
  evaluate the viability of the mitigation actions.

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Probability Mitigation Succeeds

• Estimate the probability will succeed.

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Risk Mitigation Table
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Risk Management

• Risk Identification
• Quantitative Risk Analysis
• Risk Mitigation Planning

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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 risk Analysis?

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What is Uncertainty?

• Dictionary definition
• the estimated amount or percentage by which an
  observed or calculated value may differ from the
  true value
• Benjamin Franklin pointed out
• In this world nothing can be said to be certain,
  except death and taxes

20
Risk Analysis and Decision-Making

• Risk analysis and decision making are
  fundamentally related.
• A key component of Risk Analysis is to provide
  support for a particular decision.
• In our industry, the decision that requires risk
  analysis is usually subject to acceptance by a
  team of technical professionals and approval by
  management.

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What is Quantitative Risk Analysis?

• Any technique for analyzing uncertainty and
  quantifying the effects of that uncertainty on
  factors that will significantly effect decision
  making.

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What is Quantitative Risk Analysis?

• A method of quantifying the consequences of the
  risks identified by intuition through a
  structured approach to decision making based on
• what you think you know and dont know.
• What you can do.
• What you want the outcome to be.

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When should I use Quantitative Risk Analysis?

• Risk analysis can be used throughout an UB
  project to improve the quality of technical
  evaluations and improve risk mitigation
  techniques.

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Why should I use Quantitative Risk Analysis?

• Technical professionals overrate their ability to
  predict specific variables and even a simplistic
  approach to risk analysis will lead to superior
  forecasting and decision making.

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Why should I use Quantitative Risk Analysis?

• Probabilistic methods provide better decisions
  than deterministic methods because a full range
  of potential outcomes is examined.

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Quantitative Risk Analysis

• The Process
• Problem Identification.
• Deterministic Analysis.
• Probabilistic Analysis.
• Evaluation and Communication.
• Decision and Action.

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Problem Identification

• Identify the problem, the reason that a solution
  is required, and project desires.
• Collect and review data.
• Verify accuracy of data, and ensure it 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 and probability
  distribution.
• Conduct an assessment using Monte Carlo
  simulation.

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Evaluation and Communication

• Check if the results make sense, determine if
  additional information is needed, and create
  graphs and tables to communicate the results of
  the analysis.

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Decision and Action

• Recommend the best alternative consistent with
  the analysis and project desires.

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HAZOP
How to do a HAZOP
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Essential Elements

• Procedure/System Layout.
• HAZOP Form.
• Small Group.
• Recorder.
• Co-ordinator.

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Procedure
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System Layout
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System Layout
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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.

40
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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Qualify Consequence
NOTE These are possible consequences of hazards
that can develop even with existing Safeguards
in Place prior to modifications resulting from
the HAZOP.
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Establish Probability
NOTE This is the probability of a given hazard
occurring even with existing Safeguards
in Place prior to modifications resulting from
the HAZOP.
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Risk
Risk ConsequenceProbability
For Well Control, Risk must be at Low Level.
46
With Risks Assessed

• Fill Out the Form.
• Final Entries in Risk Column.
• Only Low Risks Acceptable.

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Now What?
Here Wrap it up!! Real World Three more steps.
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Final Steps

• Mitigation
• Revised Risk
• Proposed Action

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Perils Pitfalls

• Slow process.
• Both constructive destructive.
• Side issues can mess it up.
• Probably not right the first time.
• Consequence vs. Catastrophe.

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Problem with Quantitative Risk Analysis

• Determining the probabilities.
• Mis-understanding of the inner workings of the
  model.
• Lack of reality checks.
• Ignoring relationships between variables.
• Use of subjective judgments.

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Risk Management

• Risk Identification
• Quantitative Risk Analysis
• Risk Mitigation Planning

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Risk Mitigation Planning

• Risk Mitigation Plan
• Risk Response

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Risk Mitigation Plan

• Should be incorporated into the individual well
  program for each well.
• Should include a brief description of the
  operations risks identified and analyzed in the
  previous phases and suggested mitigation measures
  that were derived.
• Keep is simple.

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Risk Mitigation Plan

• The plan should include
• Emergency phone numbers.
• Engineering drawings and sketches.
• Risk mitigation procedures.

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Risk Response

• Field personnel must be ready to implement
  emergency responses.
• Inspections, audits and field visits will assist
  in ascertaining the ability of operations
  personnel to respond to a particular risk.

56
Downhole Problems and Troubleshooting

• Wellbore Instability
• Excessive Vibration
• Fluid Influxes
• Stuck Pipe and Fishing
• Corrosion

57
Wellbore Instability

• Causes of Instability
• Symptoms
• Prevention
• Solutions and Treatments

58
Causes of Instability

• Mechanical - Most are related to mud weight, more
  specifically, to mud weight reduction while
  attempting to get underbalanced.
• Abnormal pressure, tectonic stress, and
  unconsolidated formations are all causes of
  mechanical wellbore instability.

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Causes of Instability

• Chemical - related to reactivity of shale and/or
  clay that may be present in other formations.
• Most causes by exposure to fresh water.

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Symptoms

• Most symptoms are due to rock failure and
  excessive amounts of formation in the wellbore.
• Include
• increased torque/drag.
• increase fill on bottom during connections/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.

63
Downhole Problems and Troubleshooting

• Wellbore Instability
• Excessive Vibration
• Fluid 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.

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Causes of Excess Vibration

• Drilling rough, highly fractured or abrasive
  rocks.
• Hard rocks.
• Improper handling of percussion tools.
• Gas drilling does not dampen vibrations as much
  as liquids.

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Symptoms of Vibration

• Drillstring damage noticed through inspection.
• High incidence of downhole tool failure.

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Prevention and Solution to Excessive Vibration

• Keep the drillpipe in tension.
• All compressive forces should be contained in the
  BHA.
• Calculate the neutral point so that when the
  maximum WOB is applied, the neutral point is in
  the BHA.

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Downhole Problems and Troubleshooting

• Wellbore Instability
• Excessive Vibration
• Fluid Influxes
• Stuck Pipe and Fishing
• Corrosion

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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 lt formation pressure.

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Symptoms of Unwanted Influxes

• Fluids being returned to the surface that are not
  pumped into the wellbore.
• Damp cuttings when drilling with dry gas.
• 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 our goal is to
  purposefully drill underbalanced.

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Solutions to Unwanted Influxes

• Control influx rate.
• When drilling with gas or air, attempt to unload
  the liquids from the hole. May require a switch
  to mist drilling.
• Increase EMW in stages.
• Carefully weighting up the system.

74
Downhole Problems and Troubleshooting

• Wellbore Instability
• Excessive Vibration
• Fluid Influxes
• Stuck Pipe and Fishing
• Corrosion

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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
  except differential sticking.
• Keyseating.
• Excessive cuttings due to wellbore instability.
• Mud rings.

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Symptoms

• Cannot pick up the drillstring.

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Prevention

• Proper design of the drillstring.
• Adequate hole cleaning.

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Solutions

• Fishing.

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Downhole Problems and Troubleshooting

• Wellbore Instability
• Excessive Vibration
• Fluid Influxes
• Stuck Pipe and Fishing
• Corrosion

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Corrosion

• Requirements for Corrosion.
• Causes and Factors Effecting Corrosion.
• Symptoms.
• Prevention.
• Solution.

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Requirements for Corrosion

• 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
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Causes and Factors Effecting Corrosion

• Fluid utilized is the single largest source of
  corrosion. The fluid becomes 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 stress concentrations.
• 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