Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Schlumberger CONDENFEST Webinar — 03 September 2013Analysis of Reservoir Performance for
Unconventional Gas Condensate Reservoirs
Tom BLASINGAMEPetroleum Engineering — Texas A&M University
College Station, TX 77843-3116 (USA)+1.979.255.8808 — [email protected]
Reservoir Engineering Aspects of Unconventional Reservoirs
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Brief Biography: Tom Blasingame●Role:
■ Professor, Texas A&M U.■ Holder of the Robert L. Whiting Professorship ■ B.S., M.S., and Ph.D. degrees from Texas A&M U. (PETE)
●Counts: (Sep 2013):■ 51 M.S. (thesis) Graduates and 30 M.Eng. (report, non-thesis) Graduates ■ 10 Ph.D. Graduates■Over 120 Technical Articles
●Recognition:■ Distinguished Member of the Society of Petroleum Engineers (2000)■ SPE Distinguished Service Award (2005)■ SPE Distinguished Lecturer (2005-2006)■ SPE Uren Award (2006)■ SPE Lucas Medal (2012)■ SPE DeGolyer Distinguished Service Medal (2013)
●Current Research Activities:■ Nano-Scale Flow Phenomena■ Reservoir Engineering of Near-Critical, "Liquids-Rich" Shale Systems■ Evaluation of Well Performance Data for Shale/Liquids-Rich Systems■ Numerical Modeling of Ultra-Low Permeability Reservoir Systems
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Tom BLASINGAMEPetroleum Engineering — Texas A&M University
College Station, TX 77843-3116 (USA)+1.979.255.8808 — [email protected]
Reservoir Engineering Aspects of Unconventional Reservoirs
Orientation
Schlumberger CONDENFEST Webinar — 03 September 2013Analysis of Reservoir Performance for
Unconventional Gas Condensate Reservoirs
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
●Liquids-Rich Systems?■ Fluid-Flow Mechanisms (what is really flowing where?)■ PVT (near-critical fluids are not trivial)■ Improved Recovery (we all know this is coming…)■ Fit-for-Purpose Stimulation (higher FcD, more complexity)■ Artificial Lift (fact of life…)
●Never-Ending Arguments…■ SRV (... what is it, really?)■ Desorption (... significance? timing? relevance?)■ Stimulation Fluids (... where does it go? does it matter?)■ Microseismic (... crystal ball, roulette wheel, or roadmap?)■ Pressure-Dependent Whatever (... so what?)■ Natural Fractures (... if/when/why/what?)■ Dual Porosity/Dual Permeability (... what about the physics?)■ Well Placement (vertically) (... when does it matter?)
Orientation: (Focus on Liquids-Rich Systems)
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Tom BLASINGAMEPetroleum Engineering — Texas A&M University
College Station, TX 77843-3116 (USA)+1.979.255.8808 — [email protected]
Reservoir Engineering Aspects of Unconventional Reservoirs
How Small is Small?(nano-scale pores)
Schlumberger CONDENFEST Webinar — 03 September 2013Analysis of Reservoir Performance for
Unconventional Gas Condensate Reservoirs
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Pore-Scale: Nelson Pore/Molecule Size ChartQuestion(s):●How small are pores in shale gas? Note
that the size of the pores is on the order of 5-10 times the size of the fluid molecule.
AAPG Bulletin, v. 93, no. 3 (March 2009)Pore-throat Sizes In Sandstones, Tight Sandstones, and ShalesP.H. Nelson, USGS
Perspective:●The concept of pores and
pore throats begins to break down at these scales.
●The flow path can be as small as 10-20 molecular diameters (or less).
Issues:●How do the fluids move?— Darcy flow?— Dispersion (gases)?— Knudsen flow?
●How are the fluids stored?— In the organic matter?— Adsorbed?— Another mechanism?
← Each green line is x10 SMALLER scale.
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Pore-Scale: Shale Pore Space (Barnett Example)Question(s):●Where is/are the gas/liquid stored? There
is porosity, often in the organic materials.●Why is the phase behavior of many
shales "near critical"? Nanopores?
J. Sedimentary Research, v. 79/12 (2009)Morphology, Genesis, and Distribution of Nanometer-scale Pores in Siliceous Mudstones of the Mississippian Barnett ShaleLoucks, R.G., R.M. Reed, S.C. Ruppel, and D.M. Jarvie
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
a. Gas Slippage — Kundt, A. and Warburg, E.: "Über Reibung und Wärmeleitung verdünnter Gase, " Poggendorfs Annalen der Physik und Che-mie (1875), 155, 337.
Pore-Scale: Petrophysics/Permeability
c. Microflow model and correlation, "fully implicit" formulation.b. Knudsen "microflow" model (Modified from Karniadakis and Beskok, 2002).
SPE 107954Improved Permeability-Prediction Relations for in Low Permeability SandsF.A. Florence, Occidental Petroleum Corp., J.A. Rushing, Anadarko Petroleum Corp., K.E. Newsham, Apache Corp., and T.A. Blasingame, Texas A&M U.
vx
vy
Gas Flow
1 /11
41 1 1 4tan151281
21
2121
0
0
4.0
01-
2
aa
m
aa
m
aa
m
a
kp
ak
pak
pa
kk
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
● Knudsen number is typically used to classify fluid flow regimes.
Pore-Scale: Continuum vs. Molecular (Knudsen Number)
→Representative physical length scale.→Mean free path — average distance
travelled by a fluid particle.
0.01 0.1 10 1000 Kn 0.001
CONTINUUM SLIP FLOW TRANSITION MOLECULAR
NON-DARCY FLOW
DARCY FLOW
From: Gonzalez, K.: Current and Evolving Practices for Simulation of Compositional Flow in Nano-Systems, Petroleum Engineering 631 Assigned Report, Texas A&M University (Spring 2013).
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Pore-Scale: Phase Behavior at the Nano-Scale
From: Zarragoicoechea, G.J. and Kuz, V.A. 2002. Van Der Waals Equation of State for a Fluid in a Nanopore. Physical Review E 65 (2): 021110.Zarragoicoechea, G.J. and Kuz, V.A. 2004. Critical Shift of a Confined Fluid in a Nanopore. Fluid Phase Equilibria 220 (1): 7-9.
Intuitive, but Zarragoicoechea and Kuz show by derivation and data that there is a shift in critical temperature due to pore
size, they also postulate a similar relation for critical pressure but note that no data existed (at that time) to
validate the pressure relation.
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Tom BLASINGAMEPetroleum Engineering — Texas A&M University
College Station, TX 77843-3116 (USA)+1.979.255.8808 — [email protected]
Reservoir Engineering Aspects of Unconventional Reservoirs
Schematic Time-Rate Analysis
Schlumberger CONDENFEST Webinar — 03 September 2013Analysis of Reservoir Performance for
Unconventional Gas Condensate Reservoirs
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Time-Rate: Schematic Production Performance Plot
●Discussion: Schematic Production Performance Plot■ The schematic represents the most common approach to EUR.■ Used CAREFULLY, this should be valid.
Loga
rithm
of R
ate
Production Time
Hyperbolic Rate
Exponential Rate
"Switch Point"from Hyperbolicto Exponential Economic Limit (in rate — qlimit)
= Estimated Ultimate Recovery (EUR)[The area under the hybrid (hyperbolic-exponential rate curves]
Economic Limit (in time — tlimit)
(tlimit)
(qlimit)
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Time-Rate: Schematic — Multi-Fracture Horizontal Well"Plug and Perf" System: Each STAGE has a certain number of perforation "clusters" (typically 4)
Cluster Cluster Cluster Cluster1 2 3 4
Stage 2
Cluster Cluster Cluster Cluster1 2 3 4
Stage n
Cluster Cluster Cluster Cluster1 2 3 4
Stage 1
"FracPoint" (and other such) Systems: Each STAGE is isolated and stimulated
Stage 1 Stage 2 Stage n
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
1:4 Slope (low FcD)
1:2 Slope (high FcD)
1:1 SlopeDepletion
(SRV?)
Compound Linear Flow Regime
Formation Linear Flow Regime
TransitionRegime
Bilinear FlowRegime
EllipticalFlow Regime
Logarithm of Production Time
Loga
rithm
of P
rodu
ctio
n R
ate
])(1[/)( )/1( bii tbDqtq
Early-Time Regimes are HYPERBOLIC?
Discussion:●1:2 Slope → b=2 (HIGH fracture conductivity) .●1:4 Slope → b=4 (LOW fracture conductivity).●This is a schematic, it overly simplifies the system.
][1/ )( tatq LFLF
Time-Rate: Flow Regimes — Multi-Fracture Horizontal Well
][1/ )( 4 tatq BLFBLF
For Shales: | days | weeks | months | years | decades | … |
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Tom BLASINGAMEPetroleum Engineering — Texas A&M University
College Station, TX 77843-3116 (USA)+1.979.255.8808 — [email protected]
Reservoir Engineering Aspects of Unconventional Reservoirs
Discussion — Reserves for Shale Gas
Schlumberger CONDENFEST Webinar — 03 September 2013Analysis of Reservoir Performance for
Unconventional Gas Condensate Reservoirs
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Comment:Left plot yields time required to estimate EUR (~12-32 months).The "hyperbolic" (or "constant b") flow regime is required to estimate EUR.
[all data obtained from publicly available sources — Dry Horizontal Shale Gas Wells ONLY]
Modern Decline Analysis: Statistical Analysis
From
:H
eckm
an, T
.L.,
et a
l (20
13):
Bes
t Pra
ctic
es fo
r Res
erve
s Es
timat
ion
in
Unc
onve
ntio
nal R
eser
voirs
—Pr
esen
t and
Fut
ure
Con
side
ratio
ns,
Key
note
pre
sent
atio
n pr
esen
ted
at th
e 20
13 S
PE U
ncon
vent
iona
l R
esou
rces
Con
fere
nce,
The
Woo
dlan
ds, T
X (U
SA),
10-1
2 A
pril
2013
.Sl
ide
—16
/28
Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Comment:Results vary when segregated by geological area, completions, spacing, etc. Analyses represent an attempt to quantify the RANGE of values.
Modern Decline Analysis: Statistical Analysis
From
:H
eckm
an, T
.L.,
et a
l (20
13):
Bes
t Pra
ctic
es fo
r Res
erve
s Es
timat
ion
in
Unc
onve
ntio
nal R
eser
voirs
—Pr
esen
t and
Fut
ure
Con
side
ratio
ns,
Key
note
pre
sent
atio
n pr
esen
ted
at th
e 20
13 S
PE U
ncon
vent
iona
l R
esou
rces
Con
fere
nce,
The
Woo
dlan
ds, T
X (U
SA),
10-1
2 A
pril
2013
.
[all data obtained from publicly available sources — Dry Horizontal Shale Gas Wells ONLY][P90/P50/P10 EUR Comparisons (Modified Hyperbolic Model with 30 year max life)]
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Tom BLASINGAMEPetroleum Engineering — Texas A&M University
College Station, TX 77843-3116 (USA)+1.979.255.8808 — [email protected]
Reservoir Engineering Aspects of Unconventional Reservoirs
"Unconventional" Time-Rate Analysis
Schlumberger CONDENFEST Webinar — 03 September 2013Analysis of Reservoir Performance for
Unconventional Gas Condensate Reservoirs
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Modified Hyperbolic Rate Relation:
Decline Function: D(t)
Hyperbolic Function: b(t)
Function: (t)
Time-Rate: Modified Hyperbolic Rate Relation
)( ]exp[
)( )1()(
limexp,
/1hyp,
t*ttDq
t*ttbD
qtq
i
bi
i
dtdq
qtD 1)(
constant )(
1 )(
tDdtdtb
Discussion:●qDb functions are DIAGNOSTIC.●D(t), b(t), and (t) are evaluated continuously (at all points).●This shale gas case exhibits b=2 behavior → q = a√t (Linear Flow).●Appears to be "hyperbolic," but this is just the Linear Flow portion.
)( 1)( tDtdtdq
qtt
Logarithm of Production Time
Loga
rithm
of P
rodu
ctio
n R
ate,
q(t)
Loga
rithm
ofD
(t)an
d b(
t)
q(t)
D(t)
b(t)
1:2 slope
b(t) ≈ 2
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Discussion:●qDb functions are DIAGNOSTIC.●Power-law exponential relation is derived from:●No direct analog to hyperbolic case.●This is a "tight gas" reservoir case.
PLE Rate Relation:
Decline Function: D(t)
Hyperbolic Function: b(t)
b Function: b(t)
Time-Rate: Power-Law Exponential Rate Relation
]ˆexp[ˆ)( nii tDtDqtq
)1(ˆ
1)(
nitDnD
dtdq
qtD
nn
i
i ttDDn
nDn
tDdtdtb
2)1( ] ˆ[
)1(ˆ
)(1 )(
)1(ˆ nitDnD
)( 1)( tDtdtdq
qtt
Logarithm of Production TimeLo
garit
hm o
fD(t)
and
b(t)
q(t)
D(t)
b(t)
Loga
rithm
of P
rodu
ctio
n R
ate,
q(t)
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Tom BLASINGAMEPetroleum Engineering — Texas A&M University
College Station, TX 77843-3116 (USA)+1.979.255.8808 — [email protected]
Reservoir Engineering Aspects of Unconventional Reservoirs
Reservoir Modeling —Eagle Ford Case History
Schlumberger CONDENFEST Webinar — 03 September 2013Analysis of Reservoir Performance for
Unconventional Gas Condensate Reservoirs
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Analysis: ■Model: Horizontal well with multiple fractures, non-linear analysis.■ Input PVT lab data in the model (volatile oil).■Recommend tuning an EOS based on laboratory PVT data to create an EOS
model for generating black-oil properties which should be applicable for many wells.
■Excellent match of oil and gas rate data with models until shut-in.
Modeling Case History: Ilk — SPE 160076
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Forecast: ■Oil and gas rates are extrapolated using the model (80 acres).■EUROIL = 0.23 MMSTB, EURGAS = 1.05 BSCF.
Modeling Case History: Ilk — SPE 160076
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Forecast: ■Constant pressure simulation results are imposed on productivity index and
cumulative production plots.■No dominant straight line behavior is observed.■Forecast is different with respect to drainage area.
Oil productivity index andcumulative oil production plot.
Gas productivity index and cumulative gas production plot.
Modeling Case History: Ilk — SPE 160076
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Discussion: ■EUR is a function of well spacing for less than 100 acres drainage area,
assumption (not affected over 100 acres).■EUR values are estimated at 30 years of production.■ In our simulation runs, 100 acres drainage area corresponds to 738 ft
distance between two wells.
Modeling Case History: Ilk — SPE 160076
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Tom BLASINGAMEPetroleum Engineering — Texas A&M University
College Station, TX 77843-3116 (USA)+1.979.255.8808 — [email protected]
Reservoir Engineering Aspects of Unconventional Reservoirs
Summary
Schlumberger CONDENFEST Webinar — 03 September 2013Analysis of Reservoir Performance for
Unconventional Gas Condensate Reservoirs
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Summary:●Shale Gas/Shale Liquids Resources■ In-place resources are well understood.■ Flow mechanisms are NOT well understood.■ These systems MUST BE STIMULATED to yield economic rates.
●Practical Issues on Reserves■ Use sufficient data to make appropriate estimates (18-24 months).■ The equation does not really matter — use the DIAGNOSTICS!■ Reserves estimation must become more diagnostic (less analogs).
●Take-Aways on Reserves■ Reserves are defined by stimulation, geology, and fluid type.■ There are no clear alternatives to the multi-fracture horizontal well.■ You must use diagnostics (not statistics) to define reserves.
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Schlumberger CONDENFEST Webinar | 03 September 2013Reservoir Engineering Aspects of Unconventional Reservoirs
T.A. Blasingame | Texas A&M University
Tom BLASINGAMEPetroleum Engineering — Texas A&M University
College Station, TX 77843-3116 (USA)+1.979.255.8808 — [email protected]
Reservoir Engineering Aspects of Unconventional Reservoirs
End of Presentation
Schlumberger CONDENFEST Webinar — 03 September 2013Analysis of Reservoir Performance for
Unconventional Gas Condensate Reservoirs
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