Rock Mechanics 17'1

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Rock Mechanics17.1

• Serguei Jourine Jerome Schubert
• 19 June 2003

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Outline

• Model Description
• Near Wellbore Stress State
• Failure Modes
• Transport Problems
• Possible Completion Applications

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Models
Project 408
DEVELOPMENT OF A BLOWOUT INTERVENTION METHOD AND
DYNAMIC KILL SIMULATOR FOR BLOWOUTS OCCURRING IN
ULTRA-DEEPWATER
PHASE 1. A study of wellbore collapse and
bridging phenomena
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• Geomechanics
• EVALUATE STRESSES
• PREDICT FAILURE

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Stress State

• Near Wellbore Stress State

• Effective Stresses
• Stress Paths

• Principal Stresses
• Pore Pressure

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Stress State

• Near Wellbore Stress State

Geomechanics Problem at time T(i) to T(i1)
Fluid Flow Problem at time T(i) to T(i1)
Geomechanics Problem at time T(i) to T(i1)
Fluid Flow Problem at time T(i) to T(i1)
Geomechanics Problem at time T(i) to T(i1)
Fluid Flow Problem at time T(i) to T(i1)

• S. E. Minkoff et. al Coupled fluid flow and
  geomechanical deformation modeling
• Journal of Petroleum Science and Engineering 38
  (2003) 37 56

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Stress State

• Problem Definition

Inner Radius (Pw0 at tgt0)
Outer Radius (No Flow)
Initial Conditions PPi at t0
Plain Strain (No Vertical Displacements)
Constant Horizontal Total Stress
Geomechanics Problem at time T(i) to T(i1)
Fluid Flow Problem at time T(i) to T(i1)
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Stress State

• Transient Fluid Flow

Initial Conditions PPi at t0
Inner Radius (Pw0 at tgt0)
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Stress State

• Poro-Elastic Solution

Effective Stresses - Radial (horizontal)
- Tangential (horizontal)
- Axial (vertical)
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Stress State

• Stress Bounding

Effective Stresses - Radial (horizontal)
- Tangential (horizontal)
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Stress State

• FEA Subroutines

• Excel based pre-processor with default meshes
• Axisymmetrical and 3D problems solvers
• Simple postprocessor
• ASCII export format for FEA visualization
  (Tecplot 9.0)
• Low hardware demands PC, Windows, file sizes
  0.7MB executable 0.8MB output

Smith I.M. and Griffits D.V. Programming the
Finite Element Method, third edition, John Wiley
Sons, 1997.
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Stress State

• 1.Wellbore (axisymmetrical problem)

FEM mesh
Tangential Stresses
Tangential Stresses Concentration at the
Wellbore Bottom
Wellbore Bottom
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Stress State

• 2. Perforation (3D problem)

Perforation Bottom
FEM mesh
Perforation-Wellbore Connection
Perforation
Wellbore
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Stress State

• 2. Perforation (3D problem)

Wellbore
Perforation
Horizontal Stresses Concentration at Perforation
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Stress State

• Possible Applications

• Estimation of completion possibility and pressure
  drop magnitude
• Fluid property selection and optimization
• Fast estimation of the "end member" parameters
  with elastic solutions
• Stress state estimations for complex well
  geometry (open, inclined, cased, perforated,
  multilateral) at heterogeneous formations for
  arbitrary boundary stress conditions

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• Geomechanics
• EVALUATE STRESSES
• PREDICT FAILURE

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Failure Criteria

• Interpretation

• Failure surfaces in stress space - demarcation
  line between stability and failure
• Conventional triaxial and hollow cylinder tests

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Failure Criteria

• Brittle-Ductile Transition

Ductile gt Compaction gt Porosity Decreasing
Conventional triaxial tests
Brittle gt Dilatation gt Porosity Increasing
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Failure Criteria

• Intermediate Stress Influence

Hollow Cylinder tests
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Failure Criteria

• Failure Modes

• Modified Wiebols-Cook

• SPE 9328 N.Morita

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Failure Criteria

• Failure Modes

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Failure Criteria
Failure Evolution
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Failure Criteria

• Possible Applications

• Modified testing procedure for hollow cylinders
• Failure pattern prediction and stress path
  optimization
• Flexible procedure for maximum cavitation
  potential estimations
• Accurate failure prediction for heterogeneous
  formations with complex wellbore geometry (for
  example, roof stability).

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Transport EVALUATE SOLID LOAD
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Transport
Entrainment Potential
Wellbore PConst
Top Bottom No Flow
Entrainment velocity independent property of
material
Symmetry No Axial Flow
Formation Fluid Flow QConst
Terminal Velocity
2-D STEADY NAVIER-STOKES EQUATIONS Incompressible
Flows

• H.T.Bi and J.R.Grace K.S.Lim et al. M. Rhodes

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Transport
Entrainment Estimation
Elastic
Failed
Eintrainment Potential
Failed
Elastic
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Transport
Entrainment Rate
Total rate of entrainment
Elutriation rate constant
Composition at time

• Martin Rhodes

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Transport
Entrainment Rate

• Martin Rhodes

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Transport
Erosion and Wormholes
Elastic
Failed
Elastic

• I. Vardoulakis

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Transport
Erosion and Wormholes
Porosity (Erosion)
Concentration
Time
Time
Time
Porosity (Piping)

• I. Vardoulakis

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Transport
Total Solid Loads
Erosion
Entrainment
Concentration at wellbore
Time, sec

• Limited cavern size
• Peak solid loads
• Limited time of production.

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Transport

• Possible Applications

• Estimation
• the solids production rate,
• the duration of formation production,
• porosity change near failed regions
• Problems
• empirically defined constants
• steady state solutions

Solids Load ?W(t)/Q
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Bridging
Multiphase fluid-solid flow
Bridging dynamic bottom hole pressure exceeds
the formation pressure at any flow rate
Fluid frictional pressure drop
Solid frictional pressure drop
Inflow Performance Relationship (IPR)
Solids Load
Pressure drop caused by raising of fluid and
produced solids
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Bridging

• Underground Blowout

• Underground Blowout
• Bridge above weakest point
• Tensile stresses in all directions
• Highest shear stresses

• SPE 53974, IADC/SPE 19917

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Project 408

• Possible Applications

• Pressure drop and fluid property selection
• Stress state and failure pattern prediction for
  for heterogeneous formations with complex well
  geometry
• Estimation of solids production rate, and
  duration of formation production
• Bridging prediction

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Conclusions

• Results of our study of wellbore collapse and
  bridging could be used in planning and evaluation
  cavity-like completions.
• Models and FEA numerical procedures calculate the
  flow properties for a produced solid-fluid
  mixture and estimate the stress distribution
  within the borehole under pressure drawdown
  conditions.
• A formalized method estimates the solids
  production rate, the duration of formation
  production, and porosity change on the base of
  fluidization and erosion models.
• The potential risks of bridging and underground
  blowouts could be a realistic issue in some
  cavity operations.