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1SINTEF Petroleum Research
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Location: Trondheim
OsloHoustonHirtshalsMo i Rana
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(!!!!$230 million)
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SINTEF Petroleum Research Organization 1969 IKU established
in Oslo
1975Moved to
Trondheim
1985IKU Petroleum
ResearchPrivatized.
SINTEF (100%)Shareholder
1999Changed name
to SINTEF Petroleum Research
2004Offices in
Houston, Bergen and Stavanger
ReservoirTechnology
FormationPhysics
Basinmodelling
Administrativesupport
President
Well and ProductionTechnology
Seismics
Multiphase FlowTechnology
Drilling & WellArchitecture
Solutions Oil & Gas
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Wellbore Stability and Data Acquisition in Fractured Formations
Johan TronvollResearch Director
SINTEF Petroleum Research
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Outline
" Fractured formations" Drilling problems in fractured rocks" Data required to diagnose wellbore stability problems" Tools required to diagnose wellbore stability problems" Mudlosses as a means of reservoir characterization" Summary
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Typical fractured & fluid loss formations
" Carbonate reservoirs & large anticlines" Formations in the vicinity of salt domes" Specific brittle & laminated formations" Fault zones" High permeability channel sands" …
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Drilling problems
" Mudlosses limits mudweight" Too low mudweight or severe mudlosses may induce
kicks" Kicks may result in loss of hydrostatic head, poor hole
cleaning and wellbore instabilities" Weighing up of mud may result into further losses" LCM may harm fracture conductivity in productive layers
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Data to diagnose wellbore instabilities
" Rock mechanical data" Stresses (density log, LOT, ELOT, Minifracs) – may be difficult to
obtain" Rock strength & stiffness (MWD/LWD, cuttings & cavings, cores)
" Formation porosity, permeability & mineralogy (MWD/LWD, cuttings & cavings, cores)
" Mud chemistry & temperature" Downhole P, T" Well orientation & architecture
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Tools to analyze wellbore instabilities
" Formation strength" FORMEL, LMP" Shale database -ShaCal, rock strength database
" Wellbore collapse" PSI, FEM analysis, empirical models
" Pore pressure" Basin modeling – PRESSIM" Seismic modeling" NMR
" Mudlosses" 2D analytical fracture model
" Wellbore dynamics" Kick simulator, hole cleaning simulator
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0 0.02 0.04 0.06 0.08 0.1 0.120
100
200
S cra tch le ngth [m]
UC
S [M
Pa]
0 0 .02 0.04 0.06 0.08 0.1 0.120
50
100
You
ngs
mod
ulus
[GP
a]
Geomechanical Data- from cores
Continuous Strength and stiffness log from scratch measurements -
- on a real layered core material
SCRATCH measurements
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Geomechanical Data- from cuttings and debris
SAMSS tool for measuring strength and stiffness -
- on mm size samples
CWT tool for measuring sound velocity -
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Geomechanical Data- from downhole measurements
Constitutive model
Porosity, Density, Sonic, . . . .
Simulates rock mechanical test on fictitious core
0
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-5 0 5 10 15
Strain (mStrain)
Stre
ss (M
Pa)
Strength
Constitutive modelConstitutive modelConstitutive model
Porosity, Density, Sonic, . . . .Porosity, Density, Sonic, . . . .
Simulates rock mechanical test on fictitious core
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-5 0 5 10 15
Strain (mStrain)
Stre
ss (M
Pa)
Simulates rock mechanical test on fictitious core
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-5 0 5 10 15
Strain (mStrain)
Stre
ss (M
Pa)
Strength
Correlations for shales Strength and Stiffness from sonic logs
FORMEL and LMP Strength and Stiffness from well logs
#
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Wellbore StabilityStability problems in shales during drilling
Time-Delayed Instabilities Mud Chemistry Effects
PSI – Preventing Shale InstabilitiesModelling of operable Mud-Weight Window
#
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Modeling of fracture growthin hollow cylinder tests
with boundary-element code DIGS
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How can mud loss be monitored?
Electromagnetic flowmeterResolution 10 l/min
www.geolog.it
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Mud loss dynamics in fractured rock(Beda & Carugo 2001)
Mud loss measurements
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Why mud loss should be modeled?
" More efficient handling of mud loss problems during drilling
" Formation characterization based onmud loss measurements
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1. Information on reservoir properties is gathered ’accidentally’ during normal drilling operation.
2. Rock is characterized in situ.
3. Properties can be evaluated that aredifficult to obtain from cores(e.g. fracture properties).
Key industrial benefits:
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Analytical mud loss model
xL
Borehole wall
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Mud Loss into a Single FractureSINTEF Mud Loss Demo
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Summary
" Fractured formations require understanding of the complexity of the well & formation dynamics
" Unconventional data acquisition is needed" Models have to be flexible in terms of input data – most
classical models are too ‘rigid’" Mudlosses or influx during drilling may be modeled to
diagnose wellbore instabilities or as a reservoir characterization method
" A lot of R&D is ongoing – more field data required
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