Monitoring and Risk Management

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Monitoring and Risk Management

• Maurice Dusseault

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Why Monitor?

• To increase efficiency of oil production
• To make intelligent workover decisions
• Process control enhancement (higher recovery)
• Well rate enhancement, field management
• To improve our understanding of the physics
• To test model predictions
• To provide verification of scaling approaches
  between lab, theory, and the field
• For safety environmental purposes
• All of these reduce risk

3
The Optimization Loop
In situ state (p,s Science studies Behavioral
laws Simulations Experience
Better physics Better models Predictions Other
applications New processes
DESIGN
OPTIMIZATION
MONITOR
PRODUCE
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Classification of Approaches

• Proximal methods (in well, at the flow line)
• Remote methods (generally geophysics)
• Passive methods (e.g. T, p, MS emissions)
• Active methods (4D seismic, electrical surveys)
• Snapshot methods (e.g. an InSAR image)
• Continuous methods (e.g. electronic tiltmeters)
• Offshore/onshore (e.g. seafloor pressure gauges
  offshore, vs. survey points onshore)

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Special Well Monitoring
5 of wells in a heavy oil field can be specially
monitored
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Manual Volumetric Analysis

• E.g. Dean-Stark for oil and water content
• Sand settling tubes for sand volume percent
• To measure gas cut, the flow line is opened to a
  vacuum bomb, sealed, and sent for analysis
• Clay as well?
• Requires hand work!

Dean-Stark for oil content and water percent
BSW
Risk management requires measurements, and some
of them are made by hand
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Sand Granulometry for Sanding

• Establish a type gran-ulometry from cores
• Precise granulometry bulk average samples
• Frequency of large grain occurrence
• Clay (lt2 or 5 mm)
• Correlate to type data
• See where sand is coming from
• Other inferences

? units
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Monitoring Logging Cased Wells

• g-g (r) log casing collar locators (Dz)
• CNL phase analysis to estimate porosity changes
  behind casing
• Multi-arm caliper log to track casing shape
• Dipole sonic log to assess velocity and
  attenuation state farther from the wellbore
• T logs and tracers behind the casing logs
• Borehole gravimeter log (half-space effect)
• Other useful logs? Saturation changes, acoustic
  logs for microannulus, and so on

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Measuring Reservoir Changes

• Before CHOPS f 30
• After f changes, k,
• Top cavity or gas zone
• Shaley streaks are gone
• Thin cemented beds too
• Yielded zone f 40
• Lower zones less so
• We can use logs to help understand CHOPS
• Various logs, used at different times

Neutron porosity log
Influence radius
porosity
shale caprock
cavity or gas zone
shaley zone
shale gone
cemented siltstone
f before
f after
30
36-44
unaffected
shale baserock
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Remote Monitoring - Geophysics

• 2-D VSP
• 3-D (4-D) seismic velocity, Quality tomography
• Cross-hole seismic tomography
• Surface and deep deformation measurements
• Microseismic monitoring of shearing events
• Electrical monitoring of DW - tomography
• Multipurpose monitor wells
• Gravimetry, others, but we cant do all of them
• so lets look at deformation measurements

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Temperature Changes ?V
?p 0
fn.-gr. ss
shale
convection
ss
shale
?T 100ºC
cs.-gr. ss
?T 0
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Temperature Changes

• Conductive-convective heat transport
• But, ?T causes rock ?V as well!
• ß 3-D thermal expansion coefficient
• The ?V acts against the surrounding rock
• This alters the effective stress
• So what?? What does this mean??

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Reservoir Volume Change
?T generates expansion of the zone. This means
that it pushes against the world, and radial
stresses rise, tangential stresses drop.
Expanding region from DT
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A Pure Volume Change - ?V
Surface deformation shapes
Z
?V
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A Pure Shear Displacement - ?S
Surface deformation shapes
Z
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?V ?S Deformations
Surface deformation shapes
?zV ?zS
Z
?S
?S
?V
?V
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Consequences Shear Dilation
?T??V??s' In weak rocks, shear occurs. This is a
process of dilation
hot region expansion
?V
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So What Happens Now?

• ?T causes ?V (expansion)
• ?V pushes against the rock ? ?s'
• However, the radial stress rises, the tangential
  stress drops, and shear occurs
• This is a process of dilation. Dilation ?V is 5
  to x10 times larger than ?T effect
• Some consequences
• f?, k?, all transport properties change
• Stresses change, fracture pressures (PF),
• And so on

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Dilation and Recompaction
Cold Lake 40 m thick zone
Almost full ?z recovery observed in later cycles
Cycle 1
Cycle 2
Cycle 3
Cycle 4
1.00
injection soak production
0.75
Dz
Vertical heave Dz - m
injection soak production
0.50
injection soak production
0.25
Limited recovery of Dz in first production cycles
?V from ?T
0
initial ground elevation
time
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Shear Dilation from ?T

• Assume ?T 250ºC throughout zone
• For a 40 m thick reservoir, ?z 6 - 9 cm
• ?z of 15-30 cm observed in a single cycle
• Also, after many cycles, a permanent ?z of 50-80
  cm has been observed!
• Clearly, most of this is shear dilation
• How do you couple these processes?
• How do you quantify and calibrate?
• MONITORING AND ANALYSIS!!!

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Deformation Monitoring Methods
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Deformation Monitoring

• Shear and ?V generate a deformation field
• This field can be sampled ?z, ?? (tilt)
• With enough quality data, inversion possible
• An inversion is a calculation of what is
  happening at depth, based on remote measurements
• Inversions give the magnitude and location of
  shearing and volume change
• These factors are linked to inj./prod. history
• Reservoir management decisions, such as
  inj./prod. strategy, based on interpretations

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Deformation Measurements

• Some technologies
• Satellites INSAR
• Surface surveys
• Aerial photography
• Laser ranging
• Precision tiltmeters
• Extensometers
• Casing strain gauges
• Fibre optics methods
• Geophysical logging

pressure
6 hours
Pressure or surface tilt
?tilt at one point
event
Time
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Radioactive Bullets

• Zone of interest selected
• Before casing, radioactive bullets are fired into
  the strata (not too deep!)
• Casing is placed
• Baseline gamma log run
• Logging is repeated (DT), and the difference in
  gamma peaks is measured
• Strain ?L/L, accuracy 1-2 cm over a 10 m base

baseline log repeat log
DL
compacting zone
L
L-DL
stable reference
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Casing Collar Logs

• Casing moves with the cement and the rock
• The casing collar makes a thicker steel zone
• This can be detected accurately on a log
  sensitive to the effect of steel (magnetic)
• Logs are run repeatedly, strain ?L/L
• Similar to previous diagram
• Short casing joints can be used for detail
• If casing slips, results not reliable
• If doglegged, cant run the log

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Borehole Extensometers

• Wires anchored to casing
• Brought to surface, tensioned (max 1000 m?)
• Attached to a transducer or to a mechanical
  measuring tool
• Readings taken repeatedly
• Resistant to doglegging
• Logs cant be run in the hole
• Other instruments can be installed in the same
  hole

wire 3
wire 1
sheaves
wire 2
DL
W
anchor 3
casing
anchor 2
anchor 1
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Casing Deformation
Shear
Wedging
Courtesy Trent Kaiser, noetic Engineering
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Other Borehole Methods

• Strong magnets outside fibreglass casing are used
  (fibreglass just over the interest zone) give a
  strong magnetic signal
• Strain gauges bonded to the casing, inside or
  outside (best), wire leads to surface
• Gravity logs (downhole gravimeter)
• Other behind-the-casing logs which are sensitive
  to the lithology changes
• Tiltmeters can be placed in boreholes

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Real-Time GPS Monitoring System
antenna
site
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Site Monitoring Array

• 1.5 km2 site
• 25 inj/prod wells
• Progressive CSS
• Start at bottom, move up row by row, soak, then
  produce till H2O
• 186 benchmarks placed
• Surveyed every 4-6 wk
• Deformations in the elapsed time analyzed

Alberta example, steam injection pilot
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Measurement Parameters

• Precision must be acceptable (5 of ?zmax)
• No systematic errors if possible (random only)
• The number of measurement stations must be chosen
  carefully, depending on goals
• If inversion needed, array designed rigorously
• Array must extend beyond reservoir limits to
  capture the subsidence bowl
• Stable remote benchmark needed, etc.

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Deformation Arrays
Dz Surface surveys, satellite imagery, aerial
photography
Dq tiltmeters
Dz, Dq at surface
shallow tiltmeters
deep tiltmeters
DV in reservoir
also, displacement measurements in holes can be
used
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Fracture Monitoring as Well
Must use tiltmeters for fracturing because
deformations are small
1.0Z
surface deformation
0.41Z
Z
tilt maxima
vert
horz
fracture
-uplift linked to aperture -shape linked to
geometry -skewness linked to asymmetry
depth
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More About Deformations and Coupling Flow and
Geomechanics
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Example of The Coupling Issue

• ?T changes stresses
• Stress changes lead to general shear
• Shearing changes transport properties
• Changed transport properties change the
  temperature distribution!
• And so on
• We can make similar conclusions about ?p
• So Everything is coupled
• How do we handle this?

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A Pure Volume Change - ?V
Surface deformation shapes
Z
?V
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A Pure Shear Displacement - ?S
Surface deformation shapes
Z
38
?V ?S Deformations
Surface deformation shapes
?zV ?zS
Z
?S
?S
?V
?V
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Aerial Photography
aircraft
special targets for precision
flight path
Typically - 9-fold photogrammetric overlap, then,
digital and statistical analysis to give 1-5 mm
precisions
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Various Other Methods
InSAR
surveys
tiltmeters
borehole tilt
extensometers logging methods
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Earthquake Movements, Bam, Iran
InSAR Example
Differenced ground movements due to 2003
earthquake at Bam, Iran
Note the quadrupole configuration associated with
the shear displacement event
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InSAR Interferogram
ground-subsidence for Phoenix, AZ
time series of transects

• ERS1/2 SAR data
• 18-frame time series
• eight-year period 1992-2000

40 cm
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Imperial Oil Cold Lake

• mega-row
• CSS

285 mm
200
-210
100
Vertical displacements (mm) over 86 days
260
130 mm
-165
km
heave
subsidence
mod. Stancliffe van der Kooij, AAPG 2001
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Belridge Field, CA - Subsidence
30-40 cm per year
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BelridgeSubsidenceRate

• over 18 months

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Shell Oil Canada Peace River
Multi-lateral CSS
Surface uplift / tilt data
reservoir inversion grid with 50x50m grid cells
ref. Nickles New Technology Magazine, Jan-Feb
2005
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Expansive Lateral Strains
DEPTH (m)
WELL AGI3
WELL AGI1
120
Mudstone Sand
140
Oil Sand
160
Phase A
Limestone
180
-10 0 10 20
-20 -10 0 10
Deflection (mm)
Deflection (mm)
ref Collins (1994) insert ref. Ito Suzuki
(1996)
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Microseismic Monitoring
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Microseismic Monitoring

• Large ?? redistributions during production
• ??v changes in some zones
• ??h as well, sometimes massively
• The formation shear strength is locally exceeded,
  perhaps on a weak plane
• Shearing in geological materials is a stick-slip
  phenomenon, acoustic energy is emitted
• This can be used to track fronts and processes to
  optimize in real-time

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Shearing Near a UCS Fracture
Shearing is the major energy release process in
HF!!
s
s
Shearing during HF of SWR has been detected
microseismically in the field on the fracture
flanks.
At the tip, parting occurs, little Denergy
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Waterfrac Vs Gel Stimulation
Barnett Shale Microseismic Monitoring While
Fracturing
Craig Cipolla Pinnacle
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Waterfrac Vs Gel Stimulation
Barnett Shale Microseismic Monitoring While
Fracturing
Craig Cipolla Pinnacle
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Waterfrac Vs Gel Stimulation
Barnett Shale Microseismic Monitoring While
Fracturing
Craig Cipolla Pinnacle
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Waterfrac Vs Gel Stimulation
Barnett Shale Microseismic Monitoring While
Fracturing
Craig Cipolla Pinnacle
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Arching of Stresses
Microseismic emissions from high shear regions
Regions of high lateral shear potential
soft region
Regions of high shear and dilation
Compressive stress trajectories
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MS Activity in Compaction
MS emissions will delineate slip planes and
activation of high-angle slip
region of increased lateral stresses
region of lateral unloading
slip on curved bedding planes
slip along near-horizontal, weak bedding planes
compaction
reservoir
Note, the reservoir curvature is greatly
exaggerated, x10 vertically, and the relative
compaction is also greatly exaggerated
In Ekofisk, MS monitoring helped elucidate
mechanisms
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MS Tracking of a Fireflood (1992)
C
A
x
x
stable front
x
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x
x
x
x
x
x
x
x
x
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x
x
unstable front
x
x
x
x
x
x
x
x
x
x
x
x
x
x
A good oil production B heated
channel CD poor production
x
x
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x
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x
?
x
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?
x
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?
x
x
no discrete front
x
?
x
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D
x
B
x
x
x
x
x
x
x
x
injector plus four producers
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MS Integrated Monitoring
Shell Oil, Peace River
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Parallel Processing in MS Arrays
fibre-optics or telemetry
workstation
local processors
1
2
3
4
5
monitoring or future production wells
zone of interest
sensors
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Time Lapse Seismic 4D Seismic

• The geomechanics coupled model is based on the
  mechanical earth model
• The mechanical earth model comes from seismics,
  logs, cores, an correlations
• Stress predictions are made from incorporating
  ?T, ?p over time ?t
• Time Lapse seismic gives us ?(V, Q)
• We try to use this to calibrate and clarify the
  geomechanics model so it becomes predictive in
  nature.

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Integrated Monitor Wells
data acquisition
Multiple functions in a single well
give cost-effective monitoring capability
monitoring well
process well
pressure sensors
temperature sensors
triaxial accelerometers
Multiplexing and event detection algorithms make
the collection and analysis of large data streams
tractable
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Comments

• In conventional reservoir engineering, p and T
  measurements are needed
• In coupled geomechanics, we need other types of
  measurements
• Deformations
• Changes in seismic attributes
• Microseismic emissions mapping and analysis
• Allow us to calibrate and perfect models
• Which give us predictive capabilities
• Which allows us to protect our value chain