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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 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

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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 Approaches…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” MonitoringSpecial Well” Monitoring

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 m) 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

units

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Monitoring: Logging Cased WellsMonitoring: Logging Cased Wells

(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 ~ 30% After: changes, k, …

Top cavity or gas zone Shaley streaks are gone Thin cemented beds too Yielded zone ~ 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

before 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 - GeophysicsRemote 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 {tomography Multipurpose monitor wells Gravimetry, others, but we can’t do all of them… …so let’s look at deformation measurements

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Temperature Changes & Temperature Changes & ΔΔV…V…

shale

cs.-gr. ss

ss

fn.-gr. ss

shale

Δp = 0

ΔT = 0

ΔT = 100ºC

conduction convection

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Temperature Changes…Temperature Changes…

Conductive-convective heat transport But, ΔT causes rock ΔV as well!

β = 3-D thermal expansion coefficient The ΔV acts against the surrounding rock This alters the effective stress… So what?? What does this mean??

TV

V

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Reservoir Volume ChangeReservoir Volume Change

Expandingregion

from +T

+ΔT 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 - ΔΔVV

Z

Surface deformation shapes

Δz]V

ΔVΔV

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A Pure Shear Displacement - A Pure Shear Displacement - ΔΔSS

Z

Surface deformation shapes

ΔS

Δz]S

ΔS

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ΔΔV + V + ΔΔS S DeformationsDeformations

Z

Surface deformation shapes

ΔV ΔS

Δz]V + Δz]S

ΔV ΔS

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Consequences: Shear DilationConsequences: Shear Dilation

hot regionexpansion

r

triaxial test analogy

ΔT→ΔV→Δσ′In weak rocks, shear

occurs. This is a process of dilation

+V

cool region

extensional

compressional r

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So… What Happens Now?So… What Happens Now?

+ΔT causes +ΔV (expansion) +ΔV pushes against the rock → +Δσ′ However, the radial stress rises, the tangential

stress drops, and shear occurs This is a process of dilation. Dilation ΔV is ×5

to x10 times larger than ΔT effect Some consequences:

φ↑, k↑, all transport properties change Stresses change, fracture pressures (PF),… And so on…

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Dilation and Recompaction…Dilation and Recompaction…

time

Cycle 1 Cycle 2 Cycle 3 Cycle 4

inje

ctio

n

soa

kp

rod

uct

ion

inje

ctio

n

so

ak

pro

du

ctio

n

Limited recovery of z in first production cycles

1.00

0.75

0.50

0.25

inje

ctio

n

soa

kp

rod

uct

ion

0

Ve

rtic

al h

ea

ve –

z

- m

Almost full Δz recovery observed in later cycles

z

Cold Lake – 40 m thick zone

ΔV from ΔTinitial ground elevation

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Shear Dilation from Shear Dilation from ΔΔTT

Assume ΔT = +250ºC throughout zone… For a 40 m thick reservoir, Δz ≈ 6 - 9 cm Δz of 15-30 cm observed in a single cycle Also, after many cycles, a permanent Δz 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 MethodsDeformation Monitoring Methods

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Deformation MonitoringDeformation 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…Deformation 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

ssu

re o

r su

rfac

e ti

lt

pressure

Δtilt 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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Real-Time GPS Monitoring SystemReal-Time 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, at surface : 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 “The Coupling Issue”Example of “The Coupling Issue”

ΔT 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 Δp So… Everything is coupled… How do we handle this?

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A Pure Volume Change - A Pure Volume Change - ΔΔVV

Z

Surface deformation shapes

Δz]V

ΔVΔV

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A Pure Shear Displacement - A Pure Shear Displacement - ΔΔSS

Z

Surface deformation shapes

ΔS

Δz]S

ΔS

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ΔΔV + V + ΔΔS S DeformationsDeformations

Z

Surface deformation shapes

ΔV ΔS

Δz]V + Δz]S

ΔV ΔS

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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 – Cold LakeImperial Oil – Cold Lake

mega-row

CSS

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Belridge FieldBelridge Field, CA, CA - Subsidence- Subsidence30-40 cm per year

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BelridgeBelridgeSubsidenceSubsidenceRateRate

over 18 months

0.0 in./yr

12.5

25.0

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tShell Oil Canada – Peace RiverShell Oil Canada – Peace River

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

Surface

uplift / tilt

data

reservoir inversion grid

with 50x50m grid cells

Multi-lateral

CSS

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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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Microseismic MonitoringMicroseismic Monitoring

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Microseismic MonitoringMicroseismic 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 FractureShearing Near a UCS Fracture

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 FracWaterfrac Craig Cipolla

Pinnacle

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 oil production

B: heated channelC&D: poor

production

injector plus four producers

stable front

unstablefront

no discrete front

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MS & Integrated Monitoring…MS & 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 – 4D SeismicTime 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 ΔT, Δp over time – Δt

Time Lapse seismic gives us Δ(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-effective monitoring 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 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