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Monitoring and Risk ManagementMonitoring and Risk Management

Maurice Dusseault

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Why Monitor?Why Monitor?

To increase efficiency of oil productionTo make intelligent workover decisionsProcess 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

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The Optimization LoopThe Optimization Loop

DESIGN

MONITOR PRODUCE

In situ state (p,s…Science studiesBehavioral laws

SimulationsExperience

OPTIMIZATION

Process Control

Better physicsBetter models

PredictionsOther applications

New processes

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Classification of ApproachesClassification 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 WellSpecial Well”” MonitoringMonitoring

7” casing, cemented to surface

Optimization of pump based on production rate, downhole pressure, and pump torque

Rods to drive pump

PC Pump

Producing Stratum

Cable to surface

BHP transducer, in tubing, in annulus

Ports for vacuum sample bottles and bulk production samples

Densimeter, flow velocity

Annular oil level (acoustic device)

Foam?

Annular gas rates, pressures

Accelerometer

Behind-the-casingtransducers?

span span span

ref. ref.ref.

12.0 12.0 12.0

FrequencyAmplitude

5% of wells in a heavy oil field can be specially monitored

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Manual Volumetric AnalysisManual 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!

vacuum flask% gas,& type

% sand

+ Dean-Stark foroil content and water percent

BS&W

Risk management requires measurements, and some of

them are made by hand…

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Sand Granulometry for SandingSand Granulometry for Sanding

Establish a type gran-ulometry from cores

Precise granulometry: bulk average samples

+Frequency of large grain occurrence

+Clay % (<2 or 5 µm)

Correlate to type data

See where sand is coming from…

Other inferences…

0

5

10

15

20

25

30

-5 -3 -1 1 3

TypeCut

φφφφ units

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Monitoring: Logging Cased WellsMonitoring: Logging Cased Wells

γ−γ (ρ) log + casing collar locators (∆z)

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 ChangesMeasuring Reservoir Changes

Before CHOPS φ ~ 30%

After: φ changes, k, … Top cavity or gas zone

Shaley streaks are gone

Thin cemented beds too

Yielded zone φ ~ 40%

Lower zones less so

We can use logs to help understand CHOPS

Various logs, used at different times

0 10 20 30 40 50

shaleyzone

cementedsiltstone

shale baserock

φ before φ after

unaffected

shale“gone”

cavity or gas zone

~30% 36-44%

porosity

Neutron porosity log

shale caprock

Influence radius

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Remote Monitoring Remote Monitoring -- GeophysicsGeophysics

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 ∆Ω − tomography

Multipurpose monitor wells

Gravimetry, others, but we can’t do all of them…

…so let’s look at deformationmeasurements

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Temperature Changes & Temperature Changes & ∆∆VV……

shale

cs.-gr. ss

ss

fn.-gr. ss

shale

∆p = 0

∆T = 0

∆T = 100ºC

conduction convection

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Temperature ChangesTemperature Changes……

Conductive-convective heat transport

But, ∆T causes rock ∆V as well!

β = 3-D thermal expansion coefficient

The ∆V acts against the surrounding rock

This alters the effective stress…

So what?? What does this mean??

TVV ∆β=∆

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Reservoir Volume ChangeReservoir Volume Change

Expandingregion

from + ∆∆∆∆T

+∆T generates expansion of the zone. This means that it “pushes”against the world, and radial stresses rise, tangential stresses drop.

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A Pure Volume Change A Pure Volume Change -- ∆∆VV

Z

Surface deformation shapes

∆z]V

∆V∆V

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A Pure Shear Displacement A Pure Shear Displacement -- ∆∆SS

Z

Surface deformation shapes

∆S

∆z]S

∆S

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∆∆V + V + ∆∆S S DeformationsDeformations

Z

Surface deformation shapes

∆V ∆S

∆z]V + ∆z]S

∆V ∆S

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Consequences: Shear DilationConsequences: Shear Dilation

hot regionexpansion

σθ

σr

triaxial test analogy

∆T→∆V→∆σ′In weak rocks, shear

occurs. This is a process of dilation

+∆V

cool region

extensional σθ

compressional σr

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SoSo…… What Happens Now?What Happens Now?

+∆T causes +∆V (expansion)

+∆V pushes against the rock → +∆σ′ 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:φ↑, k↑, all transport properties change

Stresses change, fracture pressures (PF),…

And so on…

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Dilation and RecompactionDilation and Recompaction……

time

Cycle 1 Cycle 2 Cycle 3 Cycle 4in

ject

ion

soak

prod

uctio

n

inje

ctio

nso

akpr

oduc

tion

Limited recovery of ∆z in first production cycles

1.00

0.75

0.50

0.25

inje

ctio

nso

akpr

oduc

tion

0

Ver

tical

hea

ve –

∆z -

m

Almost full ∆z recovery observed in later cycles

∆z

Cold Lake – 40 m thick zone

∆V from ∆Tinitial ground elevation

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Shear Dilation from Shear Dilation from ∆∆TT

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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ent Deformation Monitoring MethodsDeformation Monitoring Methods

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Deformation MonitoringDeformation Monitoring

Shear and ∆V generate a deformation field

This field can be sampled: ∆z, ∆θ (tilt)

With enough quality data, inversion possibleAn 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 MeasurementsDeformation Measurements……

Some technologies… Satellites – INSAR

Surface surveys

Aerial photography

Laser ranging

Precision tiltmeters

Extensometers

Casing strain gauges

Fibre optics methods

Geophysical logging

…Time

6 hours

Pre

ssur

e or

sur

face

tilt

pressure

∆tilt at

one point

“event”

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Radioactive BulletsRadioactive 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 (∆T),

and the difference in gamma peaks is measured

Strain = ∆L/L, accuracy ~1-2 cm over a 10 m base

“stable” reference

L L-∆L

“baseline” log“repeat” log

∆L

com

pact

ing

zone

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Casing Collar LogsCasing 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, can’t run the log

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Borehole ExtensometersBorehole 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 can’t be run in the hole

Other instruments can be installed in the same hole

wire 1wire 3

wire 2

W

anchor 3

anchor 1

anchor 2

sheaves

casing

∆L

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Casing DeformationCasing Deformation

“Wedging” Shear

Courtesy Trent Kaiser, noetic Engineering

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Other Borehole MethodsOther 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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RealReal--Time GPS Monitoring SystemTime GPS Monitoring System

antenna

site

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Site Monitoring ArraySite 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

wellsites

at depth

186 benchmark array

#8

#7

#6

#5

#4

#3

#2

#1

Wellrows

benchmarks

1 kilometre

limits of array

limits

of a

rray

Alberta example, steam injection pilot

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Measurement ParametersMeasurement 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 ArraysDeformation Arrays

∆z: Surface surveys, satellite imagery, aerial photography

shallow tiltmeters

deep tiltmeters

∆z, ∆θ at surface ∆θ: tiltmeters

∆V in reservoir

also, displacement measurements in holes can be used

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Fracture Monitoring as WellFracture Monitoring as Well

depth

Z

0.41Z

~1.0Z

-uplift linked to aperture-shape linked to geometry-skewness linked to asymmetry

fracture

surface deformation

tilt maxima

verthorz

Must use tiltmeters for fracturing because deformations are small

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More About Deformations and Coupling More About Deformations and Coupling Flow and GeomechanicsFlow and Geomechanics

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Example of Example of ““ The Coupling IssueThe 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 A Pure Volume Change -- ∆∆VV

Z

Surface deformation shapes

∆z]V

∆V∆V

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A Pure Shear Displacement A Pure Shear Displacement -- ∆∆SS

Z

Surface deformation shapes

∆S

∆z]S

∆S

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∆∆V + V + ∆∆S S DeformationsDeformations

Z

Surface deformation shapes

∆V ∆S

∆z]V + ∆z]S

∆V ∆S

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Aerial PhotographyAerial Photography

Typically - 9-fold photogrammetric overlap, then, digital and statistical analysis to give 1-5 mm precisions

flight path

aircraft

special targets for precision

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Various Other MethodsVarious Other Methods

InSAR

surveys

tiltmeters borehole tilt

extensometers logging methods

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Earthquake Movements, Bam, IranEarthquake Movements, Bam, Iran

Differenced ground movements due to 2003 earthquake at Bam, Iran

Note the quadrupole configuration associated with the shear displacement event

InSAR Example

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InSAR InterferogramInSAR Interferogram

•ERS1/2 SAR data•18-frame time series

•eight-year period 1992-2000

ground-subsidence for Phoenix, AZ

time series of transects

40 cm

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mod. Stancliffe & van der Kooij, AAPG 2001

+285 mm

+200

-210

+260

+130 mm

-165

km

+100 Vertical displacements

(mm)over 86 days

subsidence

heave

Imperial Oil Imperial Oil –– Cold LakeCold Lake

mega-rowCSS

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Belridge FieldBelridge Field, CA, CA -- SubsidenceSubsidence30-40 cm per year

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BelridgeBelridgeSubsidenceSubsidenceRateRate

over 18 months

0.0 in./yr

12.5

25.0

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Shell Oil Canada Shell Oil Canada –– Peace RiverPeace River

ref. Nickle’s New Technology Magazine, Jan-Feb 2005

Surfaceuplift / tilt

data

reservoir inversion gridwith 50x50m grid cells

Multi-lateralCSS

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Phase A

Deflection (mm) Deflection (mm)-10 0 10 20 -20 -10 0 10

120

140

DEPTH (m) WELL AGI3WELL AGI1

Mudstone& Sand

Oil Sand

ref Collins (1994); insert ref. Ito & Suzuki (1996)

160

180

Limestone

Expansive Lateral StrainsExpansive Lateral Strains

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ent Microseismic MonitoringMicroseismic Monitoring

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Microseismic MonitoringMicroseismic Monitoring

Large σ′ redistributions during production

σ′v changes in some zones

σ′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 FractureShearing Near a UCS Fracture

σ

σ

Shearing occurson the flanks ofthe fracture.

At the tip, parting occurs, little ∆energy

Shearing during HF of SWR has been detected microseismically in the field on the fracture flanks.

Shearing is the major energy release process in HF!!

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Waterfrac Vs Gel StimulationWaterfrac Vs Gel Stimulation

Observation Well

Observation WellFrac Well

Perf zones

Geophone array

Craig CipollaPinnacle

Barnett Shale Microseismic Monitoring While Fracturing

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Waterfrac Vs Gel StimulationWaterfrac Vs Gel Stimulation

X-Link Gel Frac

Waterfrac Craig CipollaPinnacle

Barnett Shale Microseismic Monitoring While Fracturing

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Waterfrac Vs Gel StimulationWaterfrac Vs Gel Stimulation

Craig CipollaPinnacle

Barnett Shale Microseismic Monitoring While Fracturing

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Waterfrac Vs Gel StimulationWaterfrac Vs Gel Stimulation

Craig CipollaPinnacle

Barnett Shale Microseismic Monitoring While Fracturing

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Arching of StressesArching of Stresses

“soft” region

Regions of high lateral

shear potential

Regions of high shear and dilation

Microseismic emissions from high shear regions

Compressive stress trajectories

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MS Activity in CompactionMS Activity in Compaction

slip along near-horizontal,weak bedding planes

region oflateral

unloadingslip on curved

bedding planes

compaction

region of increasedlateral stresses

Note, the reservoir curvature is greatly exaggerated, x10 vertically,and the relative compaction is also greatly exaggerated

reservoir

MS emissions will delineate slip planes and activation of high-angle slip

In Ekofisk, MS monitoring helped elucidate mechanisms

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MS Tracking of a Fireflood (1992)MS Tracking of a Fireflood (1992)

x

x

x

x

x x

x

x

xx x x

xx x

x x xx

x

x

x

x

xx

xx

x

x

xx

x

xx

xx

x

x

x

x

x

x

x x

x

xxx

x

x

x

x

x

x

x

x

x

x

xx

x

x

x x xx

x x

x

x

x x

x

xxx

x x

xx

x

x

xx

x

x

xx

xx

A

B

C

D

?? ?

?

A: good oilproduction

B: heatedchannel

C&D: poorproduction

injector plus four producers

stable front

unstablefront

no discrete front

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MS & Integrated MonitoringMS & Integrated Monitoring……

Shell Oil, Peace River

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Parallel Processing in MS ArraysParallel Processing in MS Arrays

sensorszone ofinterest

fibre-optics or telemetryworkstation

localprocessors1 2 3 4 5

monitoring or future production wells

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Time Lapse Seismic Time Lapse Seismic –– 4D Seismic4D 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 WellsIntegrated Monitor Wells

monitoring well

data acquisition Multiple functionsin a single well give

cost-effectivemonitoring capability

pressure sensors

temperature sensors

triaxial accelerometers

process well

Multiplexing and event detection algorithms make the collection and analysis of large data streams tractable

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CommentsComments

In conventional reservoir engineering, p and T measurements are needed

In coupled geomechanics, we need other types of measurementsDeformations

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