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5/13/2018 Chap 14- PVT - slidepdf.com
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PVTPVTPressure Volume TemperaturePressure Volume Temperature
Adrian C Todd Adrian C Todd
Heriot-Watt University Heriot-Watt University
DEPARTMENT OF PETROLEUM ENGINEERING
Heriot-Watt University Heriot-Watt University
DEPARTMENT OF PETROLEUM ENGINEERING
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PVT - ScopePVT - Scope
q
Reservoir fluid analysis provides key data toReservoir fluid analysis provides key data tothe petroleum engineer.the petroleum engineer.
q Quality of the testing is important to ensureQuality of the testing is important to ensure
realistic values used in design.realistic values used in design.
q Sample quality is the first quality issue.Sample quality is the first quality issue.
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PVT AnalysisPVT Analysis
q Provides data for field evaluation and designProvides data for field evaluation and design
® Reservoir calculationsReservoir calculations
® Well flow calculationsWell flow calculations
® Surface facilitiesSurface facilities
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PVT AnalysisPVT Analysis
q Correlation between pressure and volume atCorrelation between pressure and volume atreservoir temperature.reservoir temperature.
q Various physical constants in reservoir Various physical constants in reservoir
calculations; viscosity, density, compressibility.calculations; viscosity, density, compressibility.q Effect of separator conditions on Bo & GOR. etc.Effect of separator conditions on Bo & GOR. etc.
q Chemical composition of the volatile components.Chemical composition of the volatile components.
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PVT AnalysisPVT Analysisq Scope of the analysis depends on the nature of the fluid.Scope of the analysis depends on the nature of the fluid.
q Dry gasDry gas::
®composition, specific gravity, Bg, z, and viscositycomposition, specific gravity, Bg, z, and viscosity
q Wet gasWet gas::
®as above plus information on liquid drop out, quantities andas above plus information on liquid drop out, quantities and
compositions.compositions.
q Oil system:Oil system:
®Bubble point pressure, composition of reservoir and producedBubble point pressure, composition of reservoir and producedfluids, Bo, GOR, Bt and viscosity. All as function of pressure.fluids, Bo, GOR, Bt and viscosity. All as function of pressure.
Co.Co.
®Below Pb considerations.Below Pb considerations.
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PVT AnalysisPVT Analysis
q Gas condensate:Gas condensate:
®Reflect wet gas and oil.Reflect wet gas and oil.
®Dew point pressureDew point pressure
®Compressibility above Pd.Compressibility above Pd.
®Impact of dropping below PdImpact of dropping below Pd
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SamplingSampling
q Clearly the sample has to representative of Clearly the sample has to representative of
the reservoir contents or the drainage area.the reservoir contents or the drainage area.
q Desirable to take samples early in the life of Desirable to take samples early in the life of
the reservoir.the reservoir.
q Either sub-surface or surface sampling.Either sub-surface or surface sampling.
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Sub-Surface SamplingSub-Surface Sampling
q Can only beCan only be
representative whenrepresentative whenpressure at samplingpressure at sampling
point is above or equal topoint is above or equal to
the saturation pressure.the saturation pressure.
q At pressure close to At pressure close tosaturation pressuresaturation pressure
serious possibility of serious possibility of
sample integrity beingsample integrity being
lost.lost.q In recent yearsIn recent years
considerable advance inconsiderable advance in
downhole fluid samplingdownhole fluid sampling
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Surface SamplingSurface Sampling
q Samples of oil and gas taken from separator Samples of oil and gas taken from separator connected with the well.connected with the well.
q Fluids recombined in the laboratory on theFluids recombined in the laboratory on the
basis of the produced GORbasis of the produced GOR
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Vertical andVertical and
HorizontalHorizontalSeparatorsSeparators
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Separator Gas SamplingSeparator Gas Sampling
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Separator Liquid Sampling by GasSeparator Liquid Sampling by Gas
DisplacementDisplacement
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Separator Liquid Sampling by Water Separator Liquid Sampling by Water
DisplacementDisplacement
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Wellhead samplingWellhead sampling
q A low cost option. A low cost option.
q Only possible for veryOnly possible for very
undersaturatedundersaturated
sytsems.sytsems.
q Still single phase atStill single phase at
wellhead.wellhead.
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Sampling Wet Gas and Gas CondensateSampling Wet Gas and Gas Condensate
SystemsSystems
q Use and value of any PVT study dependantUse and value of any PVT study dependant
on the quality of the sample collected.on the quality of the sample collected.
q
Sampling wet gas and gas condensate fluidsSampling wet gas and gas condensate fluidscan give rise to errors.can give rise to errors.
q During sampling procedure it is possible toDuring sampling procedure it is possible to
alter the conditions so that samples are notalter the conditions so that samples are not
representative.representative.
q An important consideration is the phase An important consideration is the phase
behaviour.behaviour.
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Phase Behaviour.Phase Behaviour.
q
Fluids uniquelyFluids uniquelydescribed by phasedescribed by phase
diagram.diagram.
q
Within the phaseWithin the phase
diagram system isdiagram system is
two phase.two phase.
q Whereas outsideWhereas outside
the phase envelopethe phase envelopesingle phasesingle phase
Single phase
Two phase
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Phase Behaviour.Phase Behaviour.q The separation of oilThe separation of oil
and gas as predictedand gas as predicted
by the phase diagramby the phase diagramresults in each phaseresults in each phase
having its own phasehaving its own phase
diagram.diagram.
q The oil exists at itsThe oil exists at itsbubble point .bubble point .
q The gas exists at itsThe gas exists at its
dew point.dew point.
q This behaviour hasThis behaviour has
important implicationsimportant implications
on well samplingon well sampling
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Sampling WetSampling Wet
Gas and GasGas and Gas
CondensateCondensate
ReservoirsReservoirs
q
Potential locationsPotential locationsfor reservoir for reservoir
samplingsampling
S GS li W t G d
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Sampling Wet Gas andSampling Wet Gas and
Gas CondensateGas Condensate
ReservoirsReservoirsq LocationLocation
q 1. Reservoir 1. Reservoir
q 2.Bottom-hole2.Bottom-hole
q 3.Well Head3.Well Head
q 4. Separator 4. Separator q For.
q 1. Ideal
q 2. 1-phase
q 3. Cost
q 4. Cost, 1-phase,
buffer,sampling volume
q Against Against
q 1. Impossible1. Impossible
q 2. Representative ? Technology, Cost, Handling.2. Representative ? Technology, Cost, Handling.
q 3. 2-phase ? Representative ?,3. 2-phase ? Representative ?,
q 4.Gas/liquid volumes,, separator conditions,4.Gas/liquid volumes,, separator conditions,
Representative ?,Representative ?,
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Sampling Wet Gas andSampling Wet Gas and
Gas CondensateGas Condensate
Reservoirs-Flowing well.Reservoirs-Flowing well.
q Well behaviour canWell behaviour can
significantly influencesignificantly influence
nature andnature and
characteristics of fluidscharacteristics of fluidsproduced.produced.
q Flowing well gasFlowing well gas
condensate - mist flowcondensate - mist flow
S li W t GS li W t G
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Sampling Wet GasSampling Wet Gas
and Gas Condensateand Gas Condensate
Reservoirs-Shut in wellReservoirs-Shut in well
after flow.after flow.q Well acts as a separator Well acts as a separator
q Liquid rains down andLiquid rains down and
accumulates at bottomaccumulates at bottom
of well.of well.
q Pressure builds up inPressure builds up in
the well and disturbedthe well and disturbed
formation.formation.q Some gas goes backSome gas goes back
into solution.into solution.
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Well flow after shut in.Well flow after shut in.
q Large variations inLarge variations in
compositions of producedcompositions of producedfluids.fluids.
q Early period lean gasEarly period lean gas
produced. High GORproduced. High GOR
q When fluids produced fromWhen fluids produced from
bottom of well. Liquids muchbottom of well. Liquids much
lower GOR.lower GOR.
q
Then fluids from disturbedThen fluids from disturbedreservoir zonereservoir zone
q Eventually fluids fromEventually fluids from
undisturbed reservoir undisturbed reservoir
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Sampling Wet Gas and GasSampling Wet Gas and Gas
Condensate ReservoirsCondensate Reservoirs
q In assessing quality of samplesIn assessing quality of samples
important to know how long it willimportant to know how long it will
take for unrepresentative samples totake for unrepresentative samples to
be displaced from reservoir.be displaced from reservoir.
q Volumetrics required on wells,Volumetrics required on wells,
facilities and near well volumesfacilities and near well volumes
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Separator Sampling PointsSeparator Sampling Pointsq A very practical issue is A very practical issue is
the location of samplingthe location of sampling
points on separators.points on separators.
q Often located for Often located for
convenience for convenience for
accessibility.accessibility.
q Important to recogniseImportant to recognise
that the gas and liquid inthat the gas and liquid in
a separator are at their a separator are at their
saturation pressure.saturation pressure.q Small changes will resultSmall changes will result
in liquid drop out and gasin liquid drop out and gas
being producedbeing produced
Liquid in gas line
Gas in liquid line
Iso kinetic sampling
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Sampling DetailsSampling Details
q Important to record and keep note off following.Important to record and keep note off following.These records to go with samplesThese records to go with samples
q Date and timeDate and time
q Cylinder identificationCylinder identification
q Location of sampling points.Location of sampling points.
q
Temperature and pressureTemperature and pressureq GOR in separator GOR in separator
q Any special details ( H Any special details ( H22S in sample, etcS in sample, etc
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Equipment for PVT AnalysisEquipment for PVT Analysis
q Apparatus for transfer and recombination of Apparatus for transfer and recombination of separator oil and gas samples.separator oil and gas samples.
q Apparatus for measuring gas and liquid Apparatus for measuring gas and liquid
volumesvolumesq Apparatus for performing separator tests Apparatus for performing separator tests
q PVT cell and displacing pumps.PVT cell and displacing pumps.
q High pressure viscometer High pressure viscometer
q Gas chromatograph or equivalent.Gas chromatograph or equivalent.
E i t f PVT A l i S b fE i t f PVT A l i S b f
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Equipment for PVT Analysis-SubsurfaceEquipment for PVT Analysis-Subsurface
SamplesSamples
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Equipment for PVT Analysis-Surface SamplesEquipment for PVT Analysis-Surface Samples
f G C
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Equipment for PVT Analysis-Gas CondensateEquipment for PVT Analysis-Gas Condensate
SamplesSamples
PVT T tPVT T t
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PVT TestsPVT Tests
q To provide data for reservoir calculationsTo provide data for reservoir calculations
q To provide physical property data for well flow calculationsTo provide physical property data for well flow calculations
q For surface facility designFor surface facility design
q The reservoir calculations are the main driving force for theThe reservoir calculations are the main driving force for the
various tests.various tests.
q Over recent years reservoir simulation capability has generatedOver recent years reservoir simulation capability has generated
the need to extend compositional description from C7+ to inthe need to extend compositional description from C7+ to in
some cases C29+.some cases C29+.
q PVT report provides source of all reservoir engineeringPVT report provides source of all reservoir engineering
properties for behaviour over exploration, development andproperties for behaviour over exploration, development and
productionproduction
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Main PVT TestsMain PVT Tests
q
Flash vaporisation or relative volume test.Flash vaporisation or relative volume test.q Differential vaporisation test.Differential vaporisation test.
q Separator tests.Separator tests.
q Viscosity measurements.Viscosity measurements.
q Compositional measurements.Compositional measurements.
q
Special studies: e.g. Interfacial tension.Special studies: e.g. Interfacial tension.
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Simple layout of a PVT FacilitySimple layout of a PVT Facility
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Flash Vaporisation ( Relative Volume ) TestFlash Vaporisation ( Relative Volume ) Test
q Determination of the correlation between pressureDetermination of the correlation between pressure
and volume at reservoir temperature.and volume at reservoir temperature.
q The system never changes during the test.The system never changes during the test.
q The gas remains in equilibrium with the oil throughThe gas remains in equilibrium with the oil through
out the test.out the test.
q The behaviour below the bubble point does notThe behaviour below the bubble point does not
reflect reservoir behaviour, where gas has greater reflect reservoir behaviour, where gas has greater
mobility than the oil.mobility than the oil.
q This test determines theThis test determines the Bubble Point Bubble Point pressurepressure
corresponding to the reservoir temperature.corresponding to the reservoir temperature.
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Flash VaporisationFlash Vaporisation
(Relative Volume ) Test(Relative Volume ) Test
q Liberated gas remains inLiberated gas remains in
equilibrium with oilequilibrium with oil
Fl h V i ti (R l ti V l ) T tFl h V i ti (R l ti V l ) T t
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Flash Vaporisation (Relative Volume ) TestFlash Vaporisation (Relative Volume ) Test
By plotting P versus V, a break in the slope is obtained at
the Bubble Point pressure.
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Flash VaporisationFlash Vaporisation
(Relative Volume ) Test(Relative Volume ) Test
q Tests at constant pressureTests at constant pressure
and varying temperatureand varying temperature
enables thermal expansionenables thermal expansion
coefficient to be obtained for coefficient to be obtained for
well flow calculations.well flow calculations.
( )12
2 2 1
1 1 2 2
V VThermal expansion,V T T
V volume at T , V volume at T
−β =−
= =
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Flash Vaporisation (Relative Volume ) TestFlash Vaporisation (Relative Volume ) Test
q Above bubble point compressibility of Above bubble point compressibility of oil at reservoir temperature can beoil at reservoir temperature can be
determined.determined.
q No free gasNo free gas
( )2 1
2 1 2
2 2
1 1
V Vc
V P P
V =volume at pressure P
V =volume at pressure P
−=
−
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Flash Vaporisation (Relative Volume ) TestFlash Vaporisation (Relative Volume ) Test
q Main objectives:Main objectives:
® Reservoir bubble pointReservoir bubble point
pressure.pressure.
® Together withTogether withinformation from separator information from separator
tests, formation volumetests, formation volume
factor above bubble point.factor above bubble point.
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Differential VaporisationDifferential Vaporisation
q Below bubble point in reservoir gas liquidBelow bubble point in reservoir gas liquid
separation in the reservoir is a constantseparation in the reservoir is a constantchanging system.changing system.
q A test has been design to attempt to simulate A test has been design to attempt to simulate
this process.this process.q In theIn the differential vaporisationdifferential vaporisation test liberatedtest liberated
gas is removed from the cell step wise.gas is removed from the cell step wise.
q At each step below bubble point, volumes At each step below bubble point, volumesdensities , gas expansion and compressibilitydensities , gas expansion and compressibility
determined.determined.
q
Bubble point starting point.Bubble point starting point.
Differential VaporisationDifferential Vaporisation
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Differential VaporisationDifferential Vaporisation
Differential liberation process
Flash liberation process
Differential VaporisationDifferential Vaporisation
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Differential VaporisationDifferential Vaporisation
Differential VaporisationDifferential Vaporisation
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Differential VaporisationDifferential Vaporisation
ff
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Differential VaporisationDifferential Vaporisationq 8-10 pressure reduction steps at reservoir temperature.8-10 pressure reduction steps at reservoir temperature.
q
Final step to 60Final step to 60oo
F.F.q Remaining oilRemaining oil Residual Oil Residual Oil
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Differential Vaporisation vs.Flash VaporisationDifferential Vaporisation vs.Flash Vaporisation
q
Flash liberation considered to take placeFlash liberation considered to take placebetween reservoir and surface.between reservoir and surface.
q Differential liberation considered to beDifferential liberation considered to be
representative of the process in the reservoir representative of the process in the reservoir below bubble point pressure.below bubble point pressure.
q Differential tests carried out to obtain oilDifferential tests carried out to obtain oil
formation volume factors and GOR’s toformation volume factors and GOR’s to
predict behaviour below bubble pointpredict behaviour below bubble point
pressure.pressure.
S t T t
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Separator TestsSeparator Testsq Objective to determine impact of separator Objective to determine impact of separator
conditions on Bo, GOR, and produced fluid physicalconditions on Bo, GOR, and produced fluid physicalproperties.properties.
q Not the interest of facility designers.Not the interest of facility designers.
q Carried out to give an indication of oil shrinkage andCarried out to give an indication of oil shrinkage andGOR when fluids produced to surface.GOR when fluids produced to surface.
q There are not uniques values for Bo & GOR. TheyThere are not uniques values for Bo & GOR. They
depend on separator conditions.depend on separator conditions.q Starting point for the test is the bubble pointStarting point for the test is the bubble point
pressure.pressure.
q Fluid produced at surface conditons.Fluid produced at surface conditons. Stock tank oil Stock tank oil
S TS t T t
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Separator TestsSeparator Tests
PVT Cell pressure kept at
bubble point
S t T tS t T t
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Separator TestsSeparator Tests
PVT Cell pressure kept at
bubble point
S t T tS t T t
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Separator TestsSeparator Tests
PVT Cell pressure kept at
bubble point
S t T tS t T t
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Separator TestsSeparator Tests
PVT Cell pressure kept at
bubble point
S t T tS t T t
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Separator TestsSeparator Tests
PVT Cell pressure kept at
bubble point
q V resV res
Vi itVi it
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ViscosityViscosity
q
Measured at different pressures above andMeasured at different pressures above andbelow bubble point pressure.below bubble point pressure.
q Below bubble point pressure carried out under Below bubble point pressure carried out under
differential conditions.differential conditions.
q Rolling ball or capillary tube methods of Rolling ball or capillary tube methods of
measurementmeasurement
H d b l iH d b l i
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Hydrocarbon analysisHydrocarbon analysis
q Analysis from C1 to an upper C number based Analysis from C1 to an upper C number based
on paraffin series.on paraffin series.
q Historically C6 & C7+. Much higher analysisHistorically C6 & C7+. Much higher analysis
capability.capability.
q C+ characterised by specific gravity andC+ characterised by specific gravity and
apparent molecular weight.apparent molecular weight.
q Latter by depression of freezing point.Latter by depression of freezing point.
q Higher C+ characterisation helpful to processHigher C+ characterisation helpful to process
engineers re. solid phase formation.engineers re. solid phase formation.
W d A h h ltW d A h h lt
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Wax and AshphaltenesWax and Ashphaltenes
q
Solid phase formation series concern.Solid phase formation series concern.q Heavy components at low temperatures canHeavy components at low temperatures can
form solid phases.form solid phases.
q Wax in transfer lines and process facilities.Wax in transfer lines and process facilities.q Ashphaltene are larger molecules of hydrogen Ashphaltene are larger molecules of hydrogen
and carbon plus sulphur, oxygen or nitrogen.and carbon plus sulphur, oxygen or nitrogen.
q Ashphaltenes do not dissolve in oil but are Ashphaltenes do not dissolve in oil but aredispersed as colloids.dispersed as colloids.
WaxWax
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CrystallizationCrystallization
TemperatureTemperature
q Different tests used:Different tests used:
q Filtering and measuringFiltering and measuring
resistance to flow atresistance to flow at
different temperatures.different temperatures.q Appearance temperature Appearance temperature
is considered to beis considered to be
affected by super affected by super
cooling.cooling.
q The disappearanceThe disappearance
temperature istemperature is
considered to be theconsidered to be the
equilibrium value.equilibrium value. Core Laboratories
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WaxWax
CrystallizationCrystallizationTemperatureTemperature
Core Laboratories
Summary of results provided by an oil sampleSummary of results provided by an oil sample
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Summary of results provided by an oil sampleSummary of results provided by an oil sample
PVT test.PVT test.
q Saturation pressure, -bubble point.Saturation pressure, -bubble point.
q Compressibility coefficient.Compressibility coefficient.
q
Coefficient of thermal expansion.Coefficient of thermal expansion.q Relative total volume of oil and gas, VRelative total volume of oil and gas, Vtt
q Cumulative relative volume of gas. VCumulative relative volume of gas. Vgg
q
Cumulative relative volume of oil. VCumulative relative volume of oil. Voo
Summary of results provided by an oil sampleSummary of results provided by an oil sample
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Summary of results provided by an oil sampley p y p
PVT test.PVT test.
q
Gas formation volume factor or gas expansion factor Gas formation volume factor or gas expansion factor q Gas compressibility factor.Gas compressibility factor.
q Specific gravity of gasSpecific gravity of gas
q Liquid densityLiquid density
q Viscosity of liquids as a function of pressure.Viscosity of liquids as a function of pressure.
q Oil formation volume factor Oil formation volume factor
q Solution gas- oil ratio. Shrinkage of separator oil toSolution gas- oil ratio. Shrinkage of separator oil totank oiltank oil
q Hydrocarbon analysis of reservoir and produced fluidsHydrocarbon analysis of reservoir and produced fluids
Volumetric relationship of fluids in an oilVolumetric relationship of fluids in an oil
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pp
PVT testPVT test
Reference point
bubble point
Volumetric relationship of fluids in an oilVolumetric relationship of fluids in an oil
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Volumetric relationship of fluids in an oilVolumetric relationship of fluids in an oil
PVT testPVT test
Reference point
Stock Tank Conditions
Volumetric relationship of fluids in an oil PVTVolumetric relationship of fluids in an oil PVT
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Volumetric relationship of fluids in an oil PVTVolumetric relationship of fluids in an oil PVT
testtest
Interfacial Tension IFTInterfacial Tension IFT
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Interfacial Tension, IFTInterfacial Tension, IFT
q Impact of IFT now considered an importantImpact of IFT now considered an important
aspectaspect
q particularly for gas condensatesparticularly for gas condensates
q
IFT has a significant impact on the behaviour IFT has a significant impact on the behaviour of residual condensate saturation andof residual condensate saturation and
associated relative permeability.associated relative permeability.
q IFT is very low as critical point approachedIFT is very low as critical point approached
Interfacial Tension MeasurementsInterfacial Tension Measurements
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Interfacial Tension MeasurementsInterfacial Tension Measurements
q Most common method pendant dropMost common method pendant drop
( )2
ρ − ρσ = L V
e gd
l
( )2 ρ − ρσ =
L V
e gd
l
l = shape factor a function of ds/de
Interfacial Tension MeasurementsInterfacial Tension Measurements
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Interfacial Tension Measurementste ac a e s o easu e e tsq For very low IFT size of tube too small to suspend drop.For very low IFT size of tube too small to suspend drop.
q Thin wire can be usedThin wire can be used
q Light scattering has been used.Light scattering has been used.
q Heriot-Watt method -rising film methodHeriot-Watt method -rising film method
Retrograde CondensationRetrograde Condensation
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Retrograde CondensationRetrograde Condensation
q Saturation pressure is the dew point pressure.Saturation pressure is the dew point pressure.
q Gas condensate cells have a window toGas condensate cells have a window to
visualise dew point.visualise dew point.
q Not possible to determine by change of slopeNot possible to determine by change of slope
of compressibilities of gas and liquid..of compressibilities of gas and liquid..
Gas CondensateGas Condensate
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Gas CondensateGas Condensate
q
Main aspects of PVT study:Main aspects of PVT study:® Constant mass expansionConstant mass expansion
® Constant volume depletionConstant volume depletion
® Specialised tests ( IFT)Specialised tests ( IFT)
® Compositions of oil & gasCompositions of oil & gas
T Compositions of fluids are generally made by blowingCompositions of fluids are generally made by blowing
down samples and recombining the resultant liquid anddown samples and recombining the resultant liquid and
gas phase compositions.gas phase compositions.
Gas Condensate Constant Mass StudyGas Condensate Constant Mass Study
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Gas Condensate- Constant Mass StudyGas Condensate- Constant Mass Studyq No fluids removed from the cellNo fluids removed from the cell
q
Purpose to determine z value above dew point.Purpose to determine z value above dew point.q Determine dew point pressureDetermine dew point pressure
Dew point observed as drops on window
Gas Condensate- Constant Volume DepletionGas Condensate- Constant Volume Depletion
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pp
q Carried out to simulate condition below dew pointCarried out to simulate condition below dew point
q Series of pressure expansionsSeries of pressure expansions
q Volume of cell returned to original volumeVolume of cell returned to original volume
Gas Condensate Constant Volume DepletionGas Condensate Constant Volume Depletion
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Gas Condensate- Constant Volume DepletionGas Condensate- Constant Volume Depletion
q Liquid volume produced below dew pointLiquid volume produced below dew point
generates a liquid drop out curve.generates a liquid drop out curve.
Gas Condensate-Special tests IFT andGas Condensate-Special tests IFT and
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Full Compositional dataFull Compositional data
Hg
Condensate
Gas
Hg
Density cell
High pressure
sampling
Stirrer
Gas Condensate-Special tests IFT andGas Condensate-Special tests IFT and
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Full Compositional dataFull Compositional data
Hg
Condensate
Gas
Hg
Density cell
High pressure
sampling
Hg
Pendant drop
Interface
Rising film methodRising film method
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Rising film methodRising film method
Vapour
Liquid
1 cm
Rising film
thickness
Rising film method - near critical pointRising film method - near critical point
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Rising film method - near critical pointRising film method - near critical point
Very thin meniscus
height
Vapour
Liquid
1 cm
Understanding PVT Rep[ortsUnderstanding PVT Rep[orts
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Understanding PVT Rep[ortsUnderstanding PVT Rep[orts
q Purpose of the PVT report:Purpose of the PVT report:
q Although can be used for applications from Although can be used for applications from
reservoir to surface facilities. Reservoir engineeringreservoir to surface facilities. Reservoir engineering
provides the main basis.provides the main basis.
q Provides much of black oil information.Provides much of black oil information.
q Material balance equation basis for report.Material balance equation basis for report.
q PVT report provides main data for MB equation.PVT report provides main data for MB equation.
q Both flash and differential separation assumed.Both flash and differential separation assumed.
q Specific to a particular fluidSpecific to a particular fluid
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Example PVT report.Example PVT report.
Example PVT reportExample PVT report
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Example PVT report.Example PVT report.
E l PVT tE l PVT t
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Example PVT report.Example PVT report.
ExampleExample
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Examplea p e
PVTPVT
report.report.
S t T tSeparator Test
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Separator TestSeparator Test
SeparatorSeparator
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Separator Separator
TestTest
Separator TestSeparator Test
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Separator TestSeparator Test
READ THE FOOTNOTES
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Fluid Properties above bubble pointFluid Properties above bubble point
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Fluid Properties above bubble pointp p
q Relative Volume Test - Flash Vaporisation TestRelative Volume Test - Flash Vaporisation Test
RelativeRelative
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Volume Test -Volume Test -
FlashFlash
VaporisationVaporisation
TestTest
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P
V
Pb
Vsat
BB above bubble pointabove bubble point
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BBoo above bubble pointabove bubble point
ovol. reservoir oilB
vol. stock tank oil=
o
vol. bubble point oil vol. reservoir oil
B vol. stock tank oil vol. bubble point oil= ×
From separator
test
Above bubble point Above bubble point
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q Density above bubble point obtained byDensity above bubble point obtained by
combining data from separator test andcombining data from separator test andrelative volume tests.relative volume tests.
o
o ob rel
1 1v v vρ = =
o
o ob rel
1 1v v v
ρ = =
Above bubble point Above bubble point
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q
Compressibility above bubble point can beCompressibility above bubble point can beobtained from relative volume testobtained from relative volume test
o
T
1 vCv p δ= − δ o
T
1 vC
v p
δ
= − δ
o
avg T
1 vCv p ∆= − ∆
Total Formation Volume Below BubbleTotal Formation Volume Below Bubble
P i
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PointPoint
q
Total formationTotal formationvolume factor, Bvolume factor, B
tt
q Of littleOf little
significance, butsignificance, butsometimes used insometimes used in
MB basedMB based
calculationscalculations
Bo BT
Total Formation Volume Below BubbleTotal Formation Volume Below Bubble
P i tP i t
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PointPointq If we multiply BIf we multiply B
obob x vx vrelrel. we get B. we get B
tt over theover the
total pressure range above and below thetotal pressure range above and below thebubble point pressure.bubble point pressure.
Differential liberation testsDifferential liberation tests
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Differential liberation testsDifferential liberation tests
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q Volume changes during differential liberationVolume changes during differential liberation
854-763=91scf/bbl residual oil
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Residual oil not the same
composition as stock tank oil
Calculation of Gas-Oil RatioCalculation of Gas-Oil Ratio
Below the Bubble pointBelow the Bubble point
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Below the Bubble pointBelow the Bubble point
q The GOR resulting from the separator tests andThe GOR resulting from the separator tests and
those from the differential test have differentthose from the differential test have different
values.values.
q 796 ft796 ft33/B STO & 854 ft/B STO & 854 ft33/B residual oil/B residual oil
q The difference a result of the differential process of The difference a result of the differential process of
pressure draw down over the total pressure.pressure draw down over the total pressure.
q In practise, reservoir pressure drop is a differentialIn practise, reservoir pressure drop is a differential
process but the pressure drop through the tubingprocess but the pressure drop through the tubing
and separator is a flash process.and separator is a flash process.
Calculation of Gas-Oil RatioCalculation of Gas-Oil RatioBelow the Bubble pointBelow the Bubble point
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Below the Bubble pointBelow the Bubble pointThe separator value is
correct.
We need to complete
GOR values below the
bubble point.
The GOR is made up of
two elements,
Differential in the
reservoir.
Flash in the wells and to
surface.
Differential liberation
Flash liberation
Calculation of Gas-Oil RatioCalculation of Gas-Oil Ratio
B l th B bbl i tBelow the Bubble point q Th diff ti l GOR iTh diff ti l GOR i
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Below the Bubble pointBelow the Bubble point q The differential GOR isThe differential GOR is
converted in the followingconverted in the following
manner:manner:
( )s diff R liberated gas-oil ratio by differential liberation∆ =
( )3
s diff
ftR
bbl residual oil∆ =
3 3ft bbl residual oil ft
bbl residual oil bbl bubble point oil bbl bubble point oil× =
3 3ft bbl bubble point oil ft
bbl bubble point oil bbl stock tank oil bbl stock tank oil
× =
( )3
s flash
ftR
bbl stock tank oil= ∆
( )s si s flashR R R
= ∆
Differential test Separator test
( ) ( ) ( ) obs sb sflash flash diff
b resid
BR R R
V / V= − ∆
Calculation of Formation Volume Factor Calculation of Formation Volume Factor
Below the Bubble pointBelow the Bubble point
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Below the Bubble pointBelow the Bubble point
q Formation volume factors between bubble point and surfaceFormation volume factors between bubble point and surface
also show a distinct difference between flash and differential.also show a distinct difference between flash and differential.
Calculation of Formation Volume Factor Calculation of Formation Volume Factor Below the Bubble pointBelow the Bubble point
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Below the Bubble pointBelow the Bubble point
q
V/Vresidual = relative volume at pressure, B/B resid.V/Vresidual = relative volume at pressure, B/B resid.
bbl Saturated oil bbl Residual oil bbl Saturated oil
bbl Residual oil bbl Bubble point oil bbl Bubble point oil× =
o
bbl Saturated oil bbl Bubble point oil bbl Saturated oilB
bbl Bubble point oil bbl Stock Tank oil bbl Stock Tank oil× = =
obo
resid b resid
BVB V . V /V=
obo
resid b resid
BVBV . V / V
=
Viscosity DataViscosity Data
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Pressures below bubble
point match differential
test
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ViscosityViscosity
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Composition of Reservoir FluidComposition of Reservoir Fluid
Composition of Separator Gas
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Composition of Separator Gas
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p p
GasGas
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CondensateCondensate
PVT ReportPVT Report
Gas
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Condensate
PVT Report
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Liquid Drop OutLiquid Drop Out
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CurveCurve
44%
High Pressure / High Temperature, HP/HTHigh Pressure / High Temperature, HP/HTFluidsFluids
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FluidsFluids
q Recent years exploration activity has moved deeper.Recent years exploration activity has moved deeper.
q High pressure and temperature accumulations foundHigh pressure and temperature accumulations found
q Conventional PVT facilities do not enable testingConventional PVT facilities do not enable testing
these fluids.these fluids.
q Ranges 250Ranges 250ooC and 20,000 psi.C and 20,000 psi.
q At these conditions role of water cannot be ignored. At these conditions role of water cannot be ignored.