Borehole Integrity

1
Borehole Integrity 10.1-1

• Serguei Jourine
• Texas AM University
• 1 April 2003

2
Outline

• Deep Water Blowouts and Bridging
• Wellbore Bridging Model
• Bridging Scenarios
• Current Activity
• Conclusions

3
Deep Water Blowouts

• 4 deepwater sustained underground blowouts
  controlled by Boots Coots
• 3 broached mud line gas flows (20 casing set
  BOPs installed)
• 1 BOP Failure Gas Blowout
• No oil blowout has reported to date

FOR MORE INFO...
Flak L. Control of Well Issues, Marine
Insurance Facing the Changed World,
International Union of Marine Insurance-NEW YORK
2002, on-line http//www.iumi-newyork
-2002.org/Flak.htm
4
Deep Water Blowouts

• Proposed practical solutions
• capping,
• relief well drilling,
• injecting solidified reactive fluids,
• inducing bridging

5
Fastest and Least Expensive
Duration Mode of
Control
FOR MORE INFO...
SPE 53974, IADC/SPE 19917, http//www.boots-coots
-iwc.com /references/ 02_Ultra-deepwater
20blowouts.htm
6
Bridging Models

• The known mechanisms that govern the bridging
  phenomenon are mostly qualitative
• None of the available simple simulators can
  directly model the bridging processes

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Outline

• Deep Water Blowouts and Bridging
• Wellbore Bridging Model
• Bridging Scenarios
• Current Activity
• Conclusions

8
Model Concept

• Wellbore will bridge if
• ALL CONDITIONS exist
• Unstable productive formation and/or open hole
• Total pressure drop exceed formation pressure or
  stable bridge is formed within wellbore
• Formation is strong enough to prevent underground
  blowout.

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Model Concept
10
Model Background

• Inflow Performance Jones equations for liquid,
  gas and gas condensate reservoirs Fetkovich
  (Normalized back pressure) equation.
• Outflow Performance
• Multiphase steady state liquid-gas flow analysis
  based on Beggs and Brill correlation and 3P
  flow analyser algorithm (M.Hein)
• Multiphase steady state solid-fluid flow analysis
  based on engineering correlations (G.Chase,
  M.Rhodes)

11
Model Background

• Stress-Strength Analysis Axisymmetrical linear
  elastic solution for heterogeneous formation
  (Finite Element Analysis)
• Hydro-Mechanical Failure Mass balance of the
  produced solids and flowing fluid (particle
  erosion and Darcy's law for fluid flow in porous
  media)

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Model Criteria
13
Subroutines and Implementation
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Subroutines and Implementation

• Excel VBA
• Fortran 90
• Excel-based unified interface
• Independent subroutines
• Default FEA meshes
• ASCII export format for FEA visualization
• Low hardware demands

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1
In-Situ Stresses
C2

• Data for Criterion 2
• BC for FEA

16
IPR
Pbh, psi
C1
q, MscfD

• Data for Criterion 1

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Outflow
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Outflow
C2

• Flow rate and pressure distribution along the
  blowing well
• Data for Criterion 2
• BC for FEA

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FEA Subroutines

• Excel based interface
• Preprocessor with default meshes
• Solver
• Simple postrocessor
• Export to common powerful postprocessors
• Visualization (Tecplot 9.0)

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FEA
21
Outline

• Deep Water Blowouts and Bridging
• Wellbore Bridging Model
• Bridging Scenarios
• Current Activity
• Conclusions

22
Bridging Scenarios
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1. Well is out of Control
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2. Wellbore Instability
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3. Solid Production
4
Massive Solid Production
5
Concentration
Time, sec
Distance, m
Negligible Solid Production
Stable Fluid Flow
Blowout
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4a. Wellbore Collapse
Total Wellbore Collapse
Massive Solid Production
6
5
Negligible Solid Production
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4b. Bridge Formation
6
7
Bridge
Stable Fluid-Solid Flow
Blowout
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5. Bridge Stability
7
Bridge
Formation Failure
Bridge Failure
Underground Blowout
Blowout
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Deep Water Tendency
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Outline

• Deep Water Blowouts and Bridging
• Wellbore Bridging Model
• Bridging Scenarios
• Current Activity
• Conclusions

31
Numerical Procedure

• Subroutines Debugging
• Default FEA Meshes
• - clean wellbore
• - bridged wellbore
• - wellbore bottom.

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Rock Properties
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Conclusions

• Model and numerical procedure calculate the flow
  properties for a produced solid-fluid mixture and
  estimate the stress distribution within the
  borehole under blowout conditions.
• Preliminary results of computer simulations
  provide insight into the predominant factors that
  control bridging in deep water environment.
• The model explains wellbore bridging at early
  time, possible restarting of fluid flow and
  increased probability of underground crossflow in
  bridged well

34
Conclusions

• Current activity
• - numerical procedures and code debugging
• - default meshes development for most probable
  scenarios
• Real data are still critical for model validation

35
Conclusions

• The investigation is the part of project
  "Development of a Blowout Intervention Method and
  Dynamic Kill Simulator for Blowouts Occurring in
  Ultra-Deepwater" conducted under Dr. J.J.
  Schubert and Dr. P.P. Valko supervision.