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The depth of failure wellbore stability approach provides a risk assessment for drillers. The yellow

-The slip failure gradient ("pw-slip" in the figure) caused

Shows the minimum MW for well W-1 using three different rock failure criteria:

llustrates the relationship of mud weight, wellbore stability, and various rock failures. When

GEOMECHANICAL STUDY OF WELLBORE STABILITY -VIDIT MOHAN; 2.

Wellbore stability analyzed by Drill works Geo-stress software showing the pore pressure gradient (

Mud weight window versus wellbore inclination at the constant azimuth of 67° applying a Mohr

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Geomechanics Figure 2 – Depth of failure ...

Schematic relationship between mud weight and wellbore failure (Zhang et al. 2008)

The wellbore enlargement (half wellbore section) modeled by the finite element method at a

Polar chart of wellbore-breakout limit with respect to wellbore inclination (radial coordinate)

Stress polygon at depth of 2470 m and pore pressure equal to 16.5 MPa. (

demonstrates the rock strengths (UCS) from core tests in sandstones, shales, and

Shows the minimum MW for well W-9 using three different rock failure criteria:

-Predrill wellbore stability analysis for the target well with consideration of depletion. The chart

Shows the minimum MW for well W-12 using three different rock failure criteria:

a) Red dot showing the depth of study in DH. (b) Stereonet

a) Red dot showing the depth of study in DH. (b) Stereonet

Schematic relationship of wellbore failure (Zhang, 2013).

Shrinkage rates of borehole under different horizontal stress difference (Well-1).

Applications of formation stresses in well planning, wellbore stability and reservoir management.

Mud weight window versus depth determined by Mohr–Coulomb and Mogi–Coulomb criteria for

ariation of the wellbore-breakout limit vs. inclination angle for the wellbore drilled along

Schematic view of tensile wall fracture. 17

Mesozoic-Cenozoic stratigraphy correlation chart of the Zagros basin. 25

Pre-drill and post-drill wellbore stability analysis results for well A-1

Flow chart for calculating shear and tensile failure

-A typical leak-off test showing the relationships between leak-off pressure,

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-Real-time pore pressure and wellbore stability surveillance and modification of the predrill analysis

Theoretical wellbore stability modeling for the fracturing failure mode.

-Wellbore stability and strength (UCS) results for BP02 well. Uniaxial compressive strength

Temporal evaluation of pore pressure distribution around the wellbore at depth of 2500 m. T

Effects of mudcake on the mudweight window at t = 1 day.

Breakout orientations for Mishrif formation; (a) Shows the breakout orientations obtained from the

Real-time pore pressure and wellbore stability surveillance and modification of the predrill analysis. The left track shows the real-time gamma ray; ...

Bottom Up Casing Design Pore Pressure Fracture Pressure; 33.

Summary of results from 3-D Finite Element simulations for horizontal wells drilled along East

Test plug bedding plane as related to wellbore position. (Source: Aadnoy, B

COMPRESSIONAL AND TENSILE WELLBORE FAILURES; 11.

Generalized stress transformation system for deviated borehole

The revised well plan to drill through the weak bedding zone below the target depth and

Mishrif Formation stress polygon analysis showing that the inferred stress magnitudes document a normal faulting stress

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Wellbore Stability Analysis | Stress (Mechanics) | Cartesian Coordinate System

Displacement vectors around well-model number 2 at depth of 2470 meters in direction of

Base case input parameters used for bore- hole stability modelling, Glauconitic Formation sand

Types of yielding occurring around a vertical wellbore

Global Breakdown of Drilling Related NPT ($ Billions)

Flow chart for calculating shear and tensile failure

State of stress in the borehole local coordinate for 70 of borehole inclination.

Chemoporoelastic simulation of distribution of pore-pressure in Zubair Shale with time elapsed since drilling

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Stress polygon of the depth understudy after 5 years of production with a decrease in pore

Stuck pipe problem due to borehole collapse. (a) Hole pack-off.

Testing cross-plot (actual ROP vs. ANN-predicted ROP).

Wellbore instability problems in Nahr Umr.

ariation of the borehole wall temperature with well depth and circulation time

͑ a ͒ Mean and octahedral stresses and ͑ b ͒ octahedral stress versus octahedral strain

Brief summary of wellbore instability from deviated and horizontal wells in Zubair

Workflow chart illustrating 1-D MEM of wellbore instability and sand production prediction. Three

The E Field mud pressure window is based on interpolated pore pressure and formation breakdown pressures

Borehole Stability - Comparing the Deviation Sensibility of Different Failure Criteria | Deformation (Mechanics) | Elasticity (Physics)

Measured neutron porosity versus V p /V s ratio in Green Canyon subsalt well 1

Effects of mudcake on the stress cloud evolution.

Log data of Well B used for the purpose of this study.

Key is to control the width of failure zones; 7.

Relationship between global and borehole coordinate systems.

Pore Pressure measurements by RFT

Temporal evaluation of pore pressure distribution around the wellbore at depth of 2500 m. T

Typical occurrences of wellbore instability in shales

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Training cross-plot (actual ROP vs. ANN-predicted ROP).

12. VON MISES FAILURE ...

Schematic view of wellbore breakout. 17

PORE PRESSURE ESTIMATION; 18. EQUIVALENT DEPTH METHOD ...

Pore-pressure variation at different formations obtained from MDT tests run in different wells including

Displacement vectors around well-model number 2 at depth of 2470 meters in direction of

Cauchy's stress tetrahedron and projection of the traction vector ~ T onto the plane of weakness

Stress transformations in polar systems

Mishrif Formation stress polygon analysis showing that the inferred stress magnitudes document a normal faulting stress

Distribution of cavings at different depths.

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n situ stress and pore pressure used in this study

Range of parameters used in ANN

Top Down Casing Design Pore Pressure Fracture Pressure ...

The confining pressure's influence on the permeability of the bedding plane.

Depicted 1D MEM Flowchart

Calculation model for a vertical wellbore.

Predict predrill pressure and stress

wellbore stability analysis