DTE Energy Risk Assessment

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DTE Energy Risk Assessment Safety
ValvesReservoir Engineering and Storage
Services
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Otis Safety Valve Background

• Designed in the late 1960s for MichCon
• Used in 75 wells in Belle River Mills, Columbus,
  West Columbus, Washington 10 and 28 Fields
• Used in 150 other wells in non-DTE operated
  fields in Michigan
• Infrequent use outside of Michigan

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Otis Safety Valve
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Columbus Storage Well
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Otis Safety Valve

• Non-API Design
• Safety Issues During Installation, Removal and
  Daily Operations
• Low Reliability

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Otis Safety Valve Record

• Plug not properly set numerous cases
• Plug blowout during performance testing BRM 9
  well
• Ray Field
• One example in 30 years where the valve closed in
  the well during a fire. A surface safety valve
  would have also worked.

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Safety Assessments

• 1996 PB-KBB Report
• ...expressed concern for using the Otis valve
  due to a non-operable mastergate.
• 1997 DuPont Report
• ...reliability of the Otis valves was only 90.
  A minimal standard for reliability of safety
  devices should be at least 99.
• 1998-1999 MichCons Internal Review
• Substantial risk reduction with surface valves
• Site reviews with API specification manufacturers

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Operator Survey
Company Location Type Valve

• SYCON Sweden Lined Rock Surface
• InterGen England Salt Cavern Surface
• Gas de Franz France All Sub-Surface
• Bay Gas Alabama Salt Cavern Surface
• PB-KBB Inter- Salt cavern Surface
• national

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DuPont Matrix
Extreme - Flowrate over 120 MMcfd Serious -
Flowrate over 6 MMcfd Very Serious - Flowrate
over 60 MMcfd Hazardous - Flowrate below 6 MMcfd
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(No Transcript)
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DuPont Matrix
Otis Safety Valve
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Mitigating Controls

• Administrative/Management
• Training
• Engineering/Maintenance
• Evaluate all Wells
• Safety Valves
• Meeting Standards
• Posts/Fencing

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Design Change Impacts

• Higher Reliability
• Higher Safety During Installation, Removal and
  Daily Operations
• API Approved
• Well Work Risk Reduced by 67

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Surface Safety Matrix
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Surface Safety Valve
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Surface Configuration
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Otis Safety Valve