Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Petroleum Reservoir Engineering
----Basic Concepts
Pennsylvania 1859
S.K.Pant
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Outline
§ Introduction
§ Reservoir Properties
ú
ú
ú
ú
ú
ú
§
§
§
§
Porosity
Permeability
Capillary Pressures
Wettability
Relative Permeability
Reservoir Pressure
Basic PVT data
Reservoir fluid type
Drive Mechanism
Numerical simulation
Mar-2009
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Is the Party over ??
“I should stress that we are not facing
a re-run of the Oil Shocks of the
1970s. They were like the tremors
before an earthquake. We now face
the earthquake itself. This shock is
very different. It is driven by resource
constraints, …”
(Dr Colin. J. Campbell)
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Cum Discovery, Gb
The law of Diminishing return
50 Hyperbolic Creaming Curve-North sea
45
40
35
30
25
20
15
10
Actual
Hyperbolic Model
5
0
0
500
1000
1500
2000
2500
3000
3500
Cum Wildcat wells
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
The Hydrocarbon….
§ Hydrocarbons are the
simplest of the organic
compounds. As the name
suggests, hydrocarbons
are made from hydrogen
and carbon. The basic
building block is one
carbon with two
hydrogens attached,
except at the ends where
three hydrogens are
attached.
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
The Hydrocarbons…
§ When the chain is
between 5 and 9
carbons, the hydrocarbon
is gasoline.
§ About a dozen carbons
and it is diesel.
§ Around 20 carbons is
motor oil.
§ A chain of hundreds to
thousands of carbon and
hydrogens make plastic.
This particular plastic is
polyethylene.
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Definition-Reservoir Engineering
§ “Application of scientific principles to the
drainage problems arising during the
development and production of oil and gas
reservoirs”
§ “The art of developing and producing oil
and gas fluids in such a manner as to
obtain a high economic recovery.”
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Broad Functions
Reservoir Simulation
Therefore the Ultimate goal is…..
•Hydrocarbon in place
•Recoverable hydrocarbons reserves
•Rate of exploitation
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Data Type
§ Data that pertains to the reservoir rock and
its extent
ú Geologic & seismic data
ú Well Log data
ú Well test data
ú Core data
§ Data that pertains to the properties of
reservoir fluids
ú Composition of HC
ú PVT
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
The Traps
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Porosity
Porosity of rock is the ratio of pore volume to bulk
volume and is usually expressed as percentage
Vp is pore volume
Vb is bulbk volume
Vg is grain volume
Interconnected
pores
Isolated
pores
Total or Absolute Porosity:
It is the ratio of the volume of all the pores to the bulk
ú
volume of the material,
Effective porosity
ú
It is the ratio of the interconnected pore volume to the
bulk volume
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
A Pore
Elements of Pore
Throat
Size & freq distribution-uncorrelated,
correlated
Connectivity of pores and throat-No of pore
throat connecting to pores
Spatial arrangement-Arrangement of pores
of different sizes w.r.t each other
The texture of a rock consists of it's
grain or mineral crystal size, the
arrangement of the grains or crystals, and
the degree of uniformity of the grains or
crystals.
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
The role of Rock Texture…
Soi=(1-Swi)
high
Soi=(1-Swi)
low
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Pore Network-Reconstructed using thin section IMAGE
Analysis
Porosity intergranular- 0.23
Porosity total0.28
Absolute Permeability- 426md
Porosity intergranular- 0.37
Porosity total0.39
Absolute Permeability- 5600md
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Saturation
§ Saturation of a phase is the fraction of the
pore volume occupied by the phase
So+Sg+Sw=1
Connate water saturation (Swc)
Critical Oil Saturation (Soc)
Critical gas Saturation (Sgc)
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Permeability
§
Permeability is a measure of ‘ ease of flow’ or
the capacity of formation to transmit fluids.
§
Its unit is Darcy named after a French scientist
Henry Darcy in 1856.
ú
Absolute Permeability:
When only one fluid is present in the rock. It is a
property of the rock and is independent of the
fluid used in the measurement. This assumes
that the fluid does not interact with the rock.(K)
ú
Effective Permeability:
Effective permeability occurs when more than
one fluid is present & is a function of the fluid
saturation & the wetting characteristics of the
rock. (Ko,Kw,Kg)
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Permeability
The permeability is measured by
flowing a fluid of known
viscosity µ through a core plug
of measured dimensions (A and
L) and then measuring flow rate
and pressure drop. Darcy
equation becomes
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Permeability
Establishing a perfect Ø-K transform still remains a major challenge
specially in ref to carbonates
The carbonates
The clastics
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Improved Permeability estimation
Phi Group - RQI Plot
Porosity - Permeability Plot
10.000
HU 7
HU 6
1.000
RQI, micron
HU 5
HU 4
HU 3
HU 2
0.100
HU 1
0.010
Core Permeability, mD
1000.00
HU7,
y = 8081.6x 2.5518
100.00
HU6,
10.00
1.00
HU3,
0.10
0.05
y = 37.476x1.8785
y = 30.796x 2.1428
HU2,
y = 18.846x 2.4585
HU1,
0.01
0.00
y = 1648.1x2.3492
y = 355.42x 2.0499
HU5,
y = 245.68x 2.212
HU4,
0.10
0.15
0.20
0.25
0.30
0.001
0.010
0.100
1.000
Core Porosity
Phi Group
Mar-2010
0.35
0.40
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Capillary pressure
§ Combined effect of surface and
IFT of the rock and fluid, pore size
and geometry & wettability of the
system.
• Major effect of Cap pres is the creation of
Transition Zone
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Capillary pressure
§ Drainage Process:
ú Non Wetting phase
displacing Wetting
phase
§ Imbibition Process:
ú Wetting phase
displacing Non wetting
phase
•Determination of Connate water
•Establish Saturation –height relation
Mar-2010
•Rock Typing
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Wettability
§ ‘The tendency of a fluid to spread or adhere to a solid surface in
presence of another immiscible fluid ‘
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Relative Permeability
§ When two or more phases flow simultaneously the ratio of
effective to absolute permeability is termed ‘Relative
permeability’
Kro= ko/k
Kre= kw/k
Krg= kg/k
Swc
Soc
NwP
WP
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Relative Permeability-Rock typing
§ The variation in Rock
Texture imparts
significant changes in
Rel perm estimates in
core plugs of same
formation
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Relative Permeability-Core Condition
§ Comparison of Relperms of cores with
natural reservoir
wettability preserved
against a plug
cleaned, dried and
resaturated.
§ Relative Permeability
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Relative Permeability-wettability
Type
No
Nw
Krw
Water
Wet
2-3
4-6
0.1-0.4
Mixed
Wet
3-5
2-4
0.5-0.9
Oil Wet
6-8
1.5-3
0.8-1.0
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Reservoir Pressure
§ Reservoir Pressure
§ The fluids confined in the pores of the reservoir rock occur
under certain degree of pressure, generally called reservoir
pressure
ú The maximum pressure is called the static bottom hole
pressure, the shut in pressure or static formation pressure
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Well testing
§ The response of the reservoir to change in production/
injection rates in a well is monitored
§ The reservoir response is measured in terms of ‘pressure’
response & is usually dependent on K, Skin, Well bore
storage, boundaries, fractures, dual porosity et.c
Evaluation: Deliverability, Properties, Size
ú Management: Refining forecast, Front movement
ú Description: Faults, barriers
ú
P
Res
K,s,C
T
qo
t
P
Model
K,s,C
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Radial Flow in a porous media :
For a single phase fluid flow (radial) in a constant
permeability and porosity for a fluid of small and
constant compressibility, the eauation is :
Pws= Pi-162.6qµB/kh*log((T+∆t)/ ∆t)
K= 162.6qµB
mh
S= 1.151[ P1hr-Pwf] –log (K / ФuCtrw2 )+3.23]
m
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Pressure Build-up analysis
§ Log-log Plot(Diagnostic plot):
Log ▲t Vs Log ▲P
§ Horner Plot or MDH Plot :
Log [(tp+ ▲t)/ ▲t] Vs Pwf
▲Pskin= 0.87mS
Jactual =
q
.
P*- Pwf
Jideal =
q
.
P*-Pwf- ▲Pskin
Flow Efficiency = Jactual/ Jideal
D(distance of fault)=
(0.00105K ▲t/ ФuCt)1/2
Where
▲t = point at the time of intersection
between two
straight lines
Horner Plot
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Field Example
XYZ
2222-2250.5m (B2)
3 distinct slopes
K:588md, kh:17105 mdft
Nearest distance to heterogeneity: 130ft
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Field Example
XYZ
2222-2250.5m (B2)
3 distinct slopes
K:588md, kh:17105 mdft
Nearest distance to heterogeneity: 130ft
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
More data More Refinement
Fig-4
L-II RFT Pressure Data
920
1983-84
1993-94
940
1997-98
tvds s (m )
960
980
1000
1020
1040
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
Normalised pressures ( psi)
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Differing Aquifer Support
I4
MDT pressure of layer-II
P3
I5
MDT pressure of layer-IV
I4
P2
I2
I5
well P3-2/06
well P2-3/06
2150
well P3-2/06
well I5-9/06
well I2-10/06
well I1-06/08
Well I6-07/08
D1-14-10/07
Well P5-9/08
well p6 11/08
2260
well P4-4/06
well I5-9/06
2160
well I2-10/06
2270
31%
well I1-06/08
Well I6-07/08
2170
D1-14-10/07
2280
wELL p5-9/08
well p6-11/08
2180
2290
well p1-12/08
Mar-2010
3560
3540
3520
3500
3480
3460
3440
3420
3400
2360
3380
2250
3360
2350
3340
2240
3320
2340
3300
2230
3280
2330
3260
2220
3240
2320
3220
2210
3200
2310
3180
2200
2920
2940
2960
2980
3000
3020
3040
3060
3080
3100
3120
3140
3160
3180
3200
3220
3240
3260
3280
3300
3320
3340
3360
3380
3400
3420
3440
2300
3160
15%
2190
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Data - Fluid Properties
§ Expressing HC in
place in surface
conditions
§ Estimation of
Pb,FVF,Rs,Bg,
Viscosity
§ Laboratory or
empirical relations
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Basic PVT
Properties
Mar-2010
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Reservoir Fluid Types
Tr<Tc
Tc<Tr<Tct
Tr>Tct
§Black oil
§Retrograde
§Wet gas
§Low shrinkage oil
condensate
§Dry gas
§Volatile oil
§Near Critical Cond
gas
Mole Comp.
Black Oil
Volatile Oil
Gas. Cond
Dry gas
C1
48.83
64.36
87.07
95.85
C2
2.75
7.52
4.39
2.67
C3
1.93
4.74
2.29
0.34
C4
1.6
4.12
1.74
0.52
C5
1.15
2.97
0.83
0.08
C6
1.59
1.38
0.60
0.12
C7+
42.15
14.91
3.80
0.42
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
The Role of Heavy Components….
After Mccain,W.D
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Bo v/rv
1.2-1.3
GOR-v/v
35-125
API°
15-40
Colour
BrownD.Green
API
GOR
Phase Envelop-Black Oil
T
T
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Phase Envelop-Low shrinkage Oil
Bo v/rv
<1.2
GOR-v/v
35
API°
<35
Colour
Black
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Phase Envelop-Volatile Oil
GOR
API
Bo v/rv
< 2.0
GOR-v/v
350-550
API°
45-55
Colour
GreenishOrange
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Phase Envelop-Near Critical Crude
Bo v/rv
> 2.0
GOR-v/v
> 550
API°
45-55
Colour
Light
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Phase Envelop-Retrograde Gas
Condensate
GOR
API
GOR-v/v
1400-16000
API°
> 50
Colour
Light
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Phase Envelop-Wet Gas
GOR
API
GOR-v/v
1100018000
API°
60
Colour
Light
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Phase Envelop- Dry Gas
GOR-v/v
>18000
API°
>
Colour
Light
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Drive mechanism
§ Depletion drive:
Expansion of gas
evolved from solution
ú
ú
ú
ú
ú
No free gas cap and no
active water drive
Rapid pressure decline
Water free production
Rapidly increasing GOR
Low ultimate oil recovery
(5-20%)
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Drive mechanism
§ Gas Cap drive:
Expansion of Gas cap
gas
ú Gas cap and no or small
ú
ú
ú
ú
active water drive
Less rapid pressure decline
Water free production
Rapidly increasing GOR in
structurally high wells
Moderate ultimate oil
recovery (25-40%)
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Drive mechanism
§ Water Drive:
Production of oil by
water displacing
process is & usually
most efficient process
Very gradual pressure
decline
ú Little change in producing
GOR
ú Early water production
from structurally lower
wells
ú High ultimate recovery
ú
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Drive mechanism
§ Gravity Drainage:
As a result of difference in reservoir fluid
densities
ú Low GOR in structurally low wells
ú Formation of Secondary GCG
ú High GOR in structurally high wells
ú Little or no water production
ú High ultimate recovery
ú Variable rate of pressure decline
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Asphaltene –The problem
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Scales for reservoir heterogeneity
MICRO
Thin sections
MACRO
Core
MEGA
Well logging
Well test
3D seismic
GIGA
Seismic
Basin studies
RSIN3
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Reservoir simulation
§ The dictionary meaning of the word
‘simulate’ is ‘to give an appearance of’
§ Forms an integral part of Reservoir
Management Functions (RMF)
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Reservoir simulation
§ Mimics the behavior of a real system through
a model (physical, analog, electrical or
numerical) based on realistic assumptions
§ Simulation can be close to reality but it is
never the reality ( should approach reality with
time)
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Disciplinary contributions to reservoir modeling
Seismic
Interpretation
Petrophysics
Fluid
Properties
Geological
Model
NUMERICAL
SIMULATION
MODEL
Surface
Facilities
Model Grid
Effects
Wells
Vertical
Horizontal
Multilateral
Economics
RSIN1
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Numerical Model
§ Mathematical models
System of equations describing the
physical behavior
These are complicated nonlinear partial
differential equations relating pressure
and saturation changes with time
Analytical solutions-generally impossible
Numerical solutions –generally the only
way
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Numerical Models
§ Basic equations for fluid flow
ú Conservation of mass
ú Conservation of momentum
ú Conservation of energy
ú Rate Equation
ú EOS
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Numerical Models
§ Numerical solution produces
answer at discrete points within
the system
§ Use of ‘finite difference’ for
transforming the continuous
differential equation to discrete
form-both space and time are
discretized (grid, timesteps)
§ Common solution procedures
• IMPES, Newton-Raphson
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Stochastic Modeling
§ Measures statistical variation in data
§
§
§
§
points-maps similar statistical properties
Better describes the heterogeneity of the
reservoir- (variograms-trends, direction)
Integrates independent measurements
Uncertainty in measured values-assessed
Algorithm-Kriging, Conditional
simulation,co-kriging
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
MICRO
Thin sections
Scales for reservoir heterogeneity
MACRO
Core
Grouping of fine layers for upscaling
1
100%
2
3
4
80%
60%
40%
20%
0%
1
3
5
7
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43
Fine layers of 'a' parasequence
<1
MEGA
Well logging
Well test
3D seismic
1 to 10
10 to 100
>100
RSIN3
GIGA
Seismic
Basin studies
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
History Match-First Realization
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
History Match -Final Realization
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Layer-9(c)
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Parallel Simulation
10 million cell
1 billion cell
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Role & Impact
ú Corporate impact-cash flow predictions
ú Insight to the various physical process
ú Sensitivity
ú Comparing different exploitation scenarios
ú Optimize project design to maximize economic
recovery
ú Real Time monitoring
Mar-2010
Generated by Foxit PDF Creator © Foxit Software
http://www.foxitsoftware.com For evaluation only.
Thanks for patient hearing
Mar-2010