Wellbore Design A Safety Critical Process

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Wellbore Design - A Safety Critical Process

• Human and Software Factors

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The Human Factor
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Tubular Design Issues

• More complex, with increased number of HPHT
  wells.
• Higher Temperatures represent one of the main
  causes of this increased complexity.
• Stress Analyses Temperature profiles for both
  Initial Conditions and Final Conditions (Load
  Cases) were traditionally assumed/estimated. For
  many challenging projects, such as HPHT wells,
  this is not accurate enough.

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Increased Complexity

• Computer based models are used in performing
  thermal simulations
• Complex Wellbore Design gt More Complex Computer
  Apps
• Harder to learn
• Harder to maintain knowledge
• Easier to use wrongly, to select wrong options

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The Designing Engineer

• Must master 3 things
• Domain Expertise
• Actual Operations to prevent from presenting a
  theoretical solution without practicality
• In-depth knowledge of the Computer App that is
  being used in the design.
• Most satisfy A B, but are deficient in C.

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Deficiency in Mastering the App

• Most engineers tasked with designing the well are
  using the app only once every 6 to 12 months
• Lack of adequate training
• Hard to maintain expert knowledge
• Easy to make usability mistakes

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The Risks of App Deficiency

• Computer App Results are used in real life
• It is here that one simulates real life
  situations within the world of the software. It
  requires all of A, B C to make sure that the
  two realities are in sync.
• The designer must understand what the app is
  capable of doing and how it should be used
  correctly

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Misusing the App - Example

• Simulating a Hydrocarbon Gas Production
  Operation, to be used for stress analysis of
  tubular strings.
• The user must choose the proper theory for
  modeling the hydrocarbon flow Black Oil or VLE
• Incorrectly, the VLE model was used
• Consequently, the resulting temperatures were too
  low

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Produced Fluid Temperature
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The Actual Mistake

• The designer, more than likely because he did not
  properly understand how the app works, did not
  investigate the Design Parameters diagram
• Flow Parameters were outside the contour lines
• For the App employed, this causes an
  extrapolation during the calculations, and thus
  the results are less accurate.

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Phase Diagram
Flow Parameters were outside the contour lines
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The Software Factor
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Landmark Initiative

• In 2002 Landmark put in place a Safety Critical
  Systems Network of Excellence
• Details about this can be found in SPE papers
• SPE 73893
• SPE 84152
• Landmark has a process for managing safety
  critical defects reported on released versions of
  applications.

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Defect Tracking System SC option
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How will you know about it?

• The defect will immediately be available on the
  LGC web site (http//www.lgc.com/)
• Via the monthly Critical Defects Report, sent to
  clients via e-mail
• The Product Manager in consultation with the
  Systems Development Director may issue a special
  note to clients.

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Critical Bugs Report - Example
WellCat Defect 149715 WellCat 2003.0.1.0
Severity SC PEF 21 Reported on 12/9/2002 Index
MultiString Results MultiString AFE Summary
Current Status In Progress
Current Design allows for wrong MultiString APB
pressures to be calculated   PROBLEM Incorrect
(by a significant margin) MultiString AFE
pressures are obtained if the final conditions of
the analysis is linked to a Prod operation which
has a significant annular (A annulus) pressure
defined in addition to the pressure from initial
conditions.   This problem exists in
SP3.   WORKAROUND In such a situation, the user
will have to edit the input file prior to
calculating the MultiString AFE calculation. To
do this you have to select Diagnostics from the
Calculate dialog and select the Edit Input File
check box. Scroll down to the IPRES cards and
notice the IPRES data grouped with headers 0 2
1 2 2 2 3 3, etc. Edit the second set of
data labeled as 1 2. In all subsequent rows of
each group, the first column represents depth, in
feet, while the second column represents
pressure, in psi. Make sure that the pressures
at the top and at the bottom of the string are
the same as the pressures shown in the FPRES card
for the same group of data (1 25). You can now
select OK from the input file dialog. This
should give you the correct answer.    
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The Apps connection to Real World

• Input actual well data settings selections
  in the app
• The App is composed of algorithms that are based
  on certain theories

Input
The App
Results
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When should we call a defect SC?

• If the Results do not correspond to the actual
  theory (existing within the algorithms of the
  app) applied with the set of input data as
  defined and selected in the app.

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How to Catch SC Defects?

• SC defects can mostly be identified by proper
  Interpretation of results, performed by an
  experienced design engineer (ABC)
• Look for Suspect results
• Hand checking some results when possible
• The Human Factor can be key in catching Software
  SC defects.

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The Data Base
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Integrated DB Mandates Sophisticated Security
Systems

• Integrated DB (such as EDM) are deployed at
  corporate level.
• There are Multiple Users for one large DB
• Each User customized access to appropriate data
• Customized level of control, based on skill level

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Effects of Integration in One DB

• No specialized standalone communities
• No personalized versions of the data
• All engineers using the same data
• Data in the DB must be of high and dependable
  quality.

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DB Owners Must Have

• Excellently designed security systems
• Well understood ADMINISTRATION of the security
  especially User Creation. This should be approved
  as a policy by business managers.
• High quality and varied training courses for DB
  users to continuously amend their security access
  as life goes on

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Recommendations

• The design should be performed by an engineer
  with proper experience in all A, B, and C.
• Each design should be reviewed by another
  engineer who also has proper experience in all A,
  B, and C.
• DB - professionals, with a mix of both DB admin
  skills and technical domain knowledge, are needed
  in constructing security systems within any
  environment with centralized technical DB. (DB
  admin skills generally fall outside the domain of
  engineers)