1
 Introduction
 What is Pvti used for ?
 Lunching Pvti
 The Main Panel
 Define Components
 Characterisation of Plus Fraction
 The Fluid Model
 Samples In Pvti
 Phase Plot
 Exercises
2
 Fluid Properties Estimation
 Creating a Fluid System
 Simulating Experiments
 Regression
 Exporting Eclipse Pvt Table
3
Fluid Flow Simulation Data
Grid & Geometry
PVT Model
Property Model
Geocellular Model SCAL Model
Eclipse Model
Production History
Well Test
4
Different Sections In a Eclipse Data File
5
 Pvti is a compositional pvt
equation of state based
program used for
characterizing a set of fluid
samples for use in our
Eclipse simulators.
 We need Pvti because it is
vital that we have a realistic
physical model of our
reservoir fluid samples
before we try to use them in
a reservoir simulation.
6
•
 Require knowledge of fluid behavior in reservoir, well and at surface
 Over a wide range of pressures, temperatures and compositions
7
 Need to predict:
 Composition of well stream v.s. time
 Completion design (wellbore liquids)
 Gas injection or re-injection
Specification of injected gas- how much C3, 4, 5’s to
leave in
separator configuration and conditions
Miscibility effects
8
 To match an Equation of State to
observations
 This is done to compensate for the inability to
measure directly all the things we need to know
about the hydrocarbons
 To Create
 “Black-Oil” PVT tables for a Black Oil model
 “Compositional PVT parameters for a
Compositional Model
9
 The Main panel
 Systems: Define Fluids and
Samples
 Simulate: Experiments and
Observations
 Regress : Match EoS
 Export : Results to Simulators
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Edit
 Fundamentals





Fluid Model
Samples
Properties Estimation
Experiments
Observation
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16
Edit
Fundamentals

Fluid Model
Samples
Properties Estimation
Experiments
Observation
17
 Equation of State
 Components
 Binary Interaction Coefficients
 Volume Shifts
 Thermal Properties
 LBC Viscosity Coefficients
 Split
 Group
18
 An Equation of State (EOS) is
an analytic expression relating
pressure to volume and
temperature
 Best method for handling large
amounts of PVT data
 Efficient and versatile means
of expressing thermodynamic
functions in terms of PVT data
 None completely satisfactory
for all scientific and
engineering applications
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20
Equation of State
 Components
Binary Interaction Coefficients
Volume Shifts
Thermal Properties
LBC Viscosity Coefficients
Split
Group
21
22
 Library Component
 User Component
 Characterized Component
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If you use characterization
components, you must generally
specify at least two out of the
following:
Molecular weight Mw
Specific gravity , Sg
Normal boiling point temperature
, Tb
Watson characterization factor ,
Kw
27
Two strings which specify the
characterization procedure
required for:
Critical properties.
Kessler-Lee (K), Cavett (C),
Riazi-Daubert (R), Winn (W) or
Pedersen (P)
Acentric factor.
Kessler-Lee (K), Edmister (E),
Thompson (T) or Pedersen (P).
28
 Properties increasing with
increasing molecular weight
 Tc Critical Temperature
 Tb Normal Boiling Point
 Vc Critical Volume
  Acentric Factor
 o Liquid Density
 Pa Parachor
29
 Properties decreasing with
increasing molecular weight
 Pc Critical Pressure
 Zc Critical Z-Factor
Having defined our
components and pseudocomponents, we can define
what our sample is made of.
30
 Equation of State
 Components
Binary Interaction Coefficients
 Volume Shifts
 Thermal Properties
 LBC Viscosity Coefficients
 Split
 Group
31
 Strictly, binary interaction
coefficients are interpreted as
accounting for polar forces between
pairs of molecules.
 Many authors have suggested that
binaries are the obvious Equation of
State parameter to adjust to match
Equation of State to laboratory
results, especially the Methane to
plus-fraction binary. However,
Pedersen et al., have shown that
this is problematic.
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33
• Katz and Firzoobadi
• Experimentally determined for Non-Hyd:Hyd
• Hyd:Hyd all zero except between C1 and CN+
kC1-CN+=0.14  - 0.06
• Cheuh-Prausnitz
• Theoretical consideration
ki , j
  2(V V )1/ 6
c ,i c , j
 A1   1/ 3
  Vc ,i  Vc1,/j3





B




34
 Equation of State
 Components
Binary Interaction Coefficients
Volume Shifts
 Thermal Properties
 LBC Viscosity Coefficients
 Split
 Group
35
The volume shift corrections applied to the
three-parameter PR3 and SRK3 equations
of state assume that the mis-match in
predicted and measured liquid density at
some reference conditions on a componentby-component basis can be used to correct
volumes at all other pressures and
temperatures. In an attempt to account for
the known temperature dependence, two
methods are available for modifying the
volume shifts.
36
No Temperature Dependence
Temperature Dependence
 Linear Expansion Only
 Polynomial correlations
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38
 Equation of State
 Components
Binary Interaction Coefficients
Volume Shifts
 Thermal Properties
 LBC Viscosity Coefficients
Split
 Group
39
 Insufficient description of heavier
hydrocarbons reduces the accuracy
of PVT predictions” (Whitson C.H.,
SPEJ, p. 683, Aug. 1983)
 Condensates and Volatile Oils are
particularly sensitive to plus fraction
composition and properties
 Laboratories tend to give very limited
analysis to the plus fraction, i.e., MN+,
N+
40
 The plus fraction often has an
importance that appears to far
outweigh its relatively
 small mole fraction of a fluid sample.
In particular, saturation pressure
calculations can be extremely
sensitive to the mole fraction and
properties of the plus fraction. More
 accurate predictions requiring less
regression of equation of state
parameters can be achieved if a
thorough description of the plus
fraction can be made.
41
This menu allows for the
automatic splitting of the plus
fraction in to a required
number of sub fraction for
subsequent use in a large
regression or for output to a
compositional simulator such
as one in Eclipse.
There are four methods
available from this option for
splitting the plus fraction ,
which must be the last
component :
42
Constant mole fraction
splitting (CMF)
Whitson
Multi feed split, or
semi continuous
thermodynamic
splitting
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 Equation of State
 Components
Binary Interaction Coefficients
Volume Shifts
 Thermal Properties
 LBC Viscosity Coefficients
Split
Group
44
This menu allows for the automatic
grouping of the sub fraction for
subsequent use in a large regression
or for out put to a compositional
simulator such as the one in Eclipse.
There are three methods available
from this option for grouping the
components :
Mole fraction
Molecular weight
Mixing Rule
45
 Compositional simulator
uses same EOS model as
PVTi
Flash calculations can take
50% of simulation time
 Reduce number of
equations  reduce
number of components
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 Basis for grouping
 similar properties, eg MW
 same log(K) versus p trend
 insensitivity of experiments to trial
grouping
 Obvious candidates
 iC4 and nC4  C4
 iC5 and nC5  C5
 Add N2 to CH4, CO2 to C2H6 (at low
concentrations)
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Edit
Fundamentals
Fluid Model

Samples
Properties Estimation
Experiments
Observation
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View
 Samples
 Observation
 Library
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53
Finger plot give an idea of the
nature that is condensate or
volatile oil, of a given fluid sample
providing a reasonable split of the
heptanes plus, then condensate
typically has straight line or down
tuning, slope proceeding towards
the heavier fractions whilst a
volatile oil has an upturning ,slope
as it usually contains more heavy
fraction
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Utilities / Units
Edit / Fundamentals
Edit / Fluid Model

Equation of state
57
This Exercise describes how to use PVTi for Fluid Properties Estimation.Fluid properties estimation
can provide quick-look PVT tables at the well site.A saturation pressure (bubble or dew-point)
together with a reservoir composition are sufficient inputs to provide a quick-look simulation, giving
an initial estimation of fluid properties in advance of a full fluid analysis in the lab.After completing
this Exercise you should be able to use PVTi as a simulation tool for fluid properties estimation.
CO2
0.91
N2
0.16
C1
36.47
Unit :Field
C2
9.67
Temp Unit : Fahrenheit
C3
6.95
Percentage
IC4
1.44
NC4
3.93
IC5
1.44
Pb = 2516.7 psig
NC5
1.41
Temp = 220 F
C6
4.33
C7+
33.29
Mw C7+
218
Spg C7+
0.8515
Gage Pressure
58
Split The C7+ Component to 4
Components By :
Whitson Method
Draw the phase and finger plot
Compare the Phase Plots

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Edit




Samples
Properties Estimation
Experiments
Exercises
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 Define Sample 1 (ZI) as
Separator Oil
 Define Sample 2 (Gas) as
Separator Gas
 Mixing Type By : Gas/Oil Ratio
 New Sample Name:Recomb
 System Temp: 205 F
 System Press: 2000 Psia
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Single Point
Pressure Depletion
Injection Study
Separators
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69
Feed this container with N moles of fluid composition CO2 N2 C1 C 2-3C 4-6 C 7-10 C 11-15
C 16-20 C 20+ (know Zi mole fraction feed)
Flash: Determine amount, properties
and composition of the vapor and
liquid at EQUILIBRIUM
Temperature and
Pressure Set
70
K-values = Equilibrium Constants
yi
Ki 
xi
V yi
L xi
71
Specify temperature
and feed composition
of OIL
PVTi returns pressure
where phase transition
occurs.
72
Specify temperature
and feed composition
of GAS
PVTi returns pressure
where phase transition
occurs.
73
 Definition: The intensive
properties of the vapor
and liquid become equal
 Intensive properties independent of the
amount of component
 Extensive properties dependent on the amount
of substance in the
system, e.g. heat content,
volume internal energy.
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Simulation Section
Defining Fluid System
of GAS5
MAKE DEW POINT
CALCULATION
77
78
 Specify a temperature and a
series of pressures
 Pick: OIL, GAS or SIN (true
one-phase system, such as
dry gas above the
cricondontherm)
 Saturation volume will be
used as a normalization
volume
79
 At p > psat there are no compositional changes and
CVD and DL are equivalent to CCE
Vapor
liquid
Cell
Volume at
Bubble Point
liquid
Liquid
p>pb
Vapor
pb
p<pb
Liquid
p<<pb
80
 Specify a temperature and a
series of pressures.
 Applied to liquid/oil systems only
 All gas is removed at each
pressure step
 Last pressure step will be a
reduction to standard conditions automatic.
81
Schematic Diagram of
Differential Liberation
Withdrawn
Gas
Withdrawn
Gas
Vapor
Vapor
Liquid
Liquid
Liquid
Liquid
Liquid
p>pbub
pbub
p<pbub
p<<pbub
Cell
Volume at
Bubble Point
82
 Separator tests are conducted to determine
the changes in the volumetric
behavior of the reservoir fluid as the fluid
passes through the separator
(or separators) and then into the stock tank.
The resulting volumetric
behavior is influenced to a large extent by the
operating conditions, i.e.,
pressures and temperatures, of the surface
separation facilities. The primary
objective of conducting separator tests,
therefore, is to provide the
essential laboratory information necessary for
determining the optimum
surface separation conditions, which in turn will
maximize the stock-tank
oil production.
Liquid
Liquid
p>pbub
pbub
83
Separator Separator
Pressure Temperature
o
Barsa
C
Gas/Oil Ratio
50
91.46
50
Formation
Volume
Factor
Molar fraction
to Liquid
Stream
Density Density
of Liquid of Vapor
Fraction Fraction
0.642
697.41 44.614
to
1.0132 30
105.78
2.0441
0.344
787.22 1.623
Cumulative for
Separator Train
232.38
2.0441
0.344
795.25 1.260
1.0132 15.5556
240.81
2.0925
0.336
797.48 1.280
25
133.89
0.583
731.70 22.646
25
to
1.0132 5
53.23
1.8629
0.418
783.37 1.612
Cumulative for
Separator Train
187.86
1.8629
0.418
777.25 1.064
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 Cannot predict viscosities from EOS:
phase flow property
 Two most widely used correlations
Lohrenz-Bray-Clark (LBC)
Pedersen et al
 LBC OK for gases and volatile oils, very
poor for heavier oils
 Pedersen better for gases and oils, but
not good for heavy oils (presence of
asphaltenes)
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92
 Based on Corresponding States Method
(CSM)
A group of substances obey CSM if functional
dependence of “reduced” quantity on other
reduced quantities is the same for all
components in the group
Pedersen
mr = f(Tr, Pr)
 Alternative Ely and Hanley
mr = f(Tr, r)
93
 Viscosity a parameterized function of reduced
density

r 
c
where critical density
1

1 
c    xi Vc ,i 
Vc  i 1

 To give
2
3
4
  a1  a2  r  a3  r  a4  r  a5  r
N
94
95
 A Reliable Prediction of The
Pressure Performance of a
Gas Condensate Reservoir is
Necessary in Determining
Reserves And Evaluating Field
Separation Methods.
96
 Specify a temperature
(below cricondotherm) and
a series of pressures
 Applies to both oil and
condensate systems
 Vapor removed to restore
cell to original volume
 Relative volume reported is
the fraction of the cell filled
with liquid after the gas is
removed
97
Withdrawn
Gas
Withdrawn
Gas
Vapor
Vapor
Cell
Volume at
Dew Point
Vapor
Vapor
Vapor
p>pdew
pdew
Liquid
Liquid
p<pdew
p<<pdew
98
 It should be performed on all
Condensates and volatile oils as
these are the fluids which are going
to undergo the greatest
compositional changes if the
reservoir pressure is allowed to drop
below the saturation pressure.
 As the pressure drops below the
bubble point/dew point pressure, the
following calculations and
procedures are taken:
99
Simulation Section
Defining Fluid System of GAS5
Simulating Dew Point Pressure
Calculation
Simulating CCE Experiments
Simulating CVD Experiments
Observed Data:Vap-Z FactorLiquid sat – Moles Recoverd
Plotting Results
100
Simulation Section
Defining Fluid System of
GAS5
Split Heavy component to 3
,Using Multi Feed Method.
Simulating CCE Experiments
Simulating CVD Experiments
Observed Data:Vap-Z FactorLiquid sat – Moles Recovered
Plotting Results
101
102
103
 Why Regress EOS parameters?
 Incomplete fluid description
 Limitations of cubic EOS
 Problems of regression
 Multi-variable
 Non-linear
104
 Check measured data for
consistency and quality
 Compositions sum to 100%?
 Pressure-dependent data: correct
trends?
 Material balance on CVD?
 Property definitions?
 Consistent units?
 Plus fraction description?
 EOS: Use three-parameter
model - extra degree of
freedom in si (Volume Shift
Parameter)
105
 Vary properties of poorly
defined components, i.e., plus
fraction(s)
 Choose as few properties as
possible
 “Bounding” Rms or
 Variables  limits 
 Redundancy in variable set: “trial and
error” to find optimum set or
sensitivity matrix Aij = ri/xj
 Ensure variable monotonicity
106
 (Tc, pc), or Omegas of plus
fraction(s): saturation pressure,
liquid dropout, etc.
 Volume shift: Z-factors, densities,
etc.
 Zc or Vc for LBC viscosity
 Consider
 Experiment set
 Observation set and weights
 Variable set and limits
107
 Don’t Use Library Component As
Regression Parameter
Pc, Tc & w of any Non Library
Component
Pc , Tc & w of any Component With
Molecular Weight of C7 or Heavier
OmegA & OmeagB of Any
Component With Molecular weight of
C7 or Heavier
108
 Set of variables:
x  ( x1 , x2 ,..., x N )
T
 Define Residuals:
ri ( x)  yiobs  yicalc ( x)
(i  1,2,..., M )
 where M < N
 then, “Rms Error”
1 M 2
f ( x)   ri ( x)
2 i 1
109
110
 Experiments and observations
 Laboratory Measurements
 CCE
 CVD
 DL
Separator Test
 Regression: which variables?
When? How?
 Regression weights
111
112
113
114
Regression
 Using Fluid Model of Exercise-7
Fitting an EoS by regression
Regression using the normal
Variables
Plot The Results
115
 Oil based muds are widely used in offshore drilling
applications. Of concern however is the resulting
contamination associated with obtaining high quality samples
of formation hydrocarbons. The filtrate of oil based muds is
highly soluble in formation hydrocarbon fluids, therefore, any
contamination of the sample with oil based mud filtrate can
significantly affect the composition and phase behavior of the
formation fluids. The reservoir fluid samples for PVT tests can
either be collected by bottom hole and/or surface sampling
techniques as and when appropriate. During the drilling
process, due to over-balance pressure in mud column, mud
filtrate invades the formation. If an oil-based mud is used in the
drilling, it can cause major difficulties in collecting high quality
formation fluid samples. As the filtrate of oil-based
 drilling mud is miscible with the formation fluid, it could
significantly alter the composition and phase behavior of the
reservoir fluid. Even the presence of small amount of oil-based
filtrate in the collected sample, could significantly affect the
PVT properties of formation fluid.
116
 Oil based muds are in widespread
use and often contaminate PVT
samples taken at the well site.
 PVTi offers two methods for
cleaning oil based muds :
 Removing oil based mud
contamination by skimming
method.
 Removing oil based mud
contamination by subtraction
method.
117
118
119
120
MW C25+ =400
SPG =.89857
121
Mud composition
122
123
One objective of PVT Analysis
Produce data for simulation
Type of model to use
Blackoil Model
Compositional
All assume that EOS has been
tuned to reliable measured data
124
Different Sections In a Eclipse Data File
125
126
127
128
129
130
131
132
133
134
135
136
137
Region 1
Region 2
138
PB = 2516.7 PSIG
Temp = 220 F
139
140
141
Exporting
Eclipse 100 PVT
tables
Changing the unit
system
Generating Eclipse
100 PVT tables
142
Exporting Eclipse 100 PVT
tables
Changing the unit
system
Generating Eclipse 100
PVT tables
143
144
When can you use a
Black-Oil model?
When should you use
a compositional
Model?
145
 PVTi has several simulations
available for investigating gas
injection processes.The three
that correspond closely to
laboratory experiments are:
 Swelling Test
 Vaporization Test
 Multiple Contact Test
146
147
148
149
150
151
152
Moles of Injected
Gas
Sat.Press
Injected Gas : CO2
Temp : 302 F
153
Moles of Injected
Gas
Relative vol.
154
155
 An oil-gas displacement is immiscible if
the oil and gas segregate into separate
phases.
Oil-gas relative permeabilities and
capillary pressures are used.
 A displacement is miscible if the
mixture of oil and gas forms a single
hydrocarbon phase.
Oil-gas relative permeabilities and
capillary pressures are not needed.
156
 Under normal conditions, oil & gas
reservoir fluids form distinct, immiscible
phases
 Immiscible phases are separated by an
interface
associated with inter-facial tension (IFT)
when IFT=0, fluids mix => MISCIBILITY
 residual oil saturation to gas (and water)
directly proportional to IFT
 miscible displacement characterized by
low/zero residual oil saturations
157
 Establishment of miscibility
depends on
pressure (MMP)
fluid system compositions
 Miscibility normally
determined by laboratory
measurement
 Miscibility difficult to predict
analytically
complex phase behavior
derivation of surface tension
158
Three basic types of
miscible process
first-contact miscibility
condensing-gas drive
vaporizing-gas drive
159
Example Oil:
C1 - 31%
Injection gas: C1
nC4 - 55%
C10 - 14%
Pressure/Composition Diagram
for Mixtures of C1 with C1/nC4/C10 Oil.
4000
Pressure
Psia
Plait point
Cricondenbar (3250 psig)
Bubble Pts
Dew pts
0
0
50
100
Volume % Methane
160
 Rule 1:
 For 1st Contact Miscible Pressure of Displacement
must be above
Cricondenbar
161
 Pressure > MMP
 All points between solvent and
reservoir oil lie in single phase
region
 Need high concentrations of
solvent - expensive
162
 Injection gas is enriched with
intermediate components such as:
 C2, C3, C4 etc
 Mechanism:
 Phase transfer of intermediate MW hydrocarbons
from the injected gas into the oil. Some of the gas
“Condenses” into the oil.
 The reservoir oil becomes so enriched with these
materials that miscibility results between the
injection gas and the enriched oil.
163
Injection Gas
Injection Gas
Injection Gas
Injection Gas
oil
Equilibrium Oil Transferred to Next Cell
Condensing Gas Drive
164
Mixing 1:
Mixing 2:
Mixing 3:
Mixing 4:
Injection gas with Reservoir Oil
Mixture M1 splits into L1 and V1
(liquid and Vapor)
Injection gas with Liquid L1
Mixture M2 splits into L2 and V2
Injection gas with Liquid L2
Mixture M3 splits into L3 and V3
Injection gas with Liquid L3
Mixture M4 splits into L4 and V4
V1
V2
V3
injection gas
G
V4
The enriched Liquid Li position moves toward
the Plait Point until a line connecting the
injection gas and the enriched liquid lies
only in the single phase region.
M1
L1
reservoir oil
M M4
M2 3
L2
L3
Plait Point
L4
o
extension of critical tie line
165
Miscibility developed at the
trailing edge of the injection
gas
gas compositions with NO
multiple contact miscibility
gas compositions with
multiple contact miscibility
line from reservoir oil tangent
to 2 phase envelope
O
reservoir oil
gas compositions with
first contact miscibility
extension of critical tie line
166
 Pressure < MMP
 Solvent and oil not miscible
initially
 Solvent components transfer to
liquid oil phase
 Repeated contact between oil
and solvent moves system
towards plait (critical) point
(dynamic miscibility)
167
 For systems with oil composition
to left of tie line, solvent
composition must lie to right
 Field behavior is more
complicated
continuous, not batch, contact
both phases flow
actual phase behavior more complicated,
especially near plait point
168
169
• As P increases the two phase region becomes
smaller. At some point gas A is to the right of the
limiting tie line and MCM develops.
miscible
95-98%
X
X
X
X
X
X
X
X
Oil Recovery
%
X
X
Minimum Miscibility Pressure
(MMP)
P
• Results from slim tube displacements at various
pressures
170
171
172
 Injection Gas - Lean Gas, C1,
CO2, N2
 For vaporizing gas drive multiple contact miscibility
 Mechanism: Intermediate
hydrocarbon components in the
oil vaporize to enrich the gas.
 As the leading edge of the gas
slug becomes sufficiently
enriched, it becomes miscible
with the reservoir oil.
173
Injection Gas
Equilibrium Gas Transferred to Next Cell
oil
oil
oil
oil
oil
oil
174
injection gas
Mixing 1:
Mixing 2:
Mixing 3:
Mixing 4:
Mixing 5:
Injection gas with Reservoir Oil
Mixture M1 splits into L1 and V1
(liquid and Vapor)
Gas Mix V1 with reservoir oil
Mixture M2 splits into L2 and V2
Gas Mix V2 with reservoir oil
Mixture M3 splits into L3 and V3
Gas Mix V3 with reservoir oil
Mixture M4 splits into L4 and V4
Gas Mix V4 with reservoir oil
Mixture M5 splits into L5 and V5
The enriched Gas Vi position
moves toward the Plait Point
until a line connecting the
enriched gas and the
reservoir oil lies
only in the single
phase region.
G
M1
V1
o
V2
V3
o
M2
V4
o
M3
V5
M4
o
o
M5
L1
L2
L3
L4
L5
o
reservoir oil
175
injection gas
Miscibility developed at the
leading edge of the injection
gas
G
For MCM in a Vaporizing Gas Drive
The Reservoir Oil composition MUST
lie to the right of the limiting tie line
176
177
178
179
180
Typical uses of Black-Oil and
Compositional:
Black-Oil: Pressure Depletion,
Heavy to medium oils
Compositional: Gas injection,
Miscibility,Near-critical fluids,
Condensates
181
 Reservoir compositions xi, yi
from depletion experiment, i.e.,
CVD or DL
 Whitson and Torp: flash liquid
and vapour through separators
Blackoil properties ratio of
reservoir/separator volumes, etc.
 Coats: vapour as Whitson and
Torp
Liquid volumes by mass conservation
Satisfies reservoir oil density
182
First Contact Miscibility Pressure
Experiment
• Specify a temperature and two named samples
• Calculates the lowest pressure at which the samples
will be directly miscible (always one phase) in all
proportions.
183
Taking Exercise-11
Add First Contact & Multiple
Contact Miscibility Experiments
Compare The Results.
184