reservoir engineering aspects of unconventional reservoirs
DESCRIPTION
Presentation at SPE GCS Reservoir Study Group Houston, TX (USA) — 27 October 2011. Reservoir Engineering Aspects of Unconventional Reservoirs. Tom BLASINGAME Department of Petroleum Engineering Texas A&M University College Station, TX 77843-3116 (USA) +1.979.845.2292 [email protected]. - PowerPoint PPT PresentationTRANSCRIPT
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Reservoir Engineering Aspects ofUnconventional Reservoirs
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]
Reservoir Engineering Aspects ofUnconventional Reservoirs
Brief Biography — Tom Blasingame
Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Short Bio: Blasingame
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Reservoir Engineering Aspects ofUnconventional Reservoirs
Start-Up
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]
Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Start-Up: Unconventional Reservoir Systems are DIFFERENT●Flow mechanisms
(…nano-scale flow mechanisms)●Fluids are often at critical state
(…uniqueness? cause?)●Overpressure is good
(…stresses are poorly understood)●Clean-up phase must be managed
(…no "choke cowboys")●Shales are generally dessicated
(…low water recovery)●Fracture patterns poorly understood
(…rock mechanics)●Hydrocarbon liquid production
(…artificial lift)●Simultaneous Exploration/Development
(…fast track)●"Completions can't Trump Geology"
(…but we try)●Unconventional Plays are "Statistical"
(…lots of wells)●Stimulation → Multi-Fracture Horizontal Wells
(…future?)
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Reservoir Engineering Aspects ofUnconventional Reservoirs
Overview
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]
Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Overview:●Orientation●Nano-Scale Flow Behavior●Time-Rate Analysis: (aka Decline Curve Analysis)●Time-Rate-Pressure Analysis: (aka Production Analysis)●Practical Aspects●Challenge Points for Unconventional Reservoirs●Questions/Discussions
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Reservoir Engineering Aspects ofUnconventional Reservoirs
Orientation
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]
Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Orientation: Reservoir Engineering Aspects of UR
●Where we want to be: (or so we think)■ Fit for purpose stimulation
(... oil/gas/condensate/geology)■ Effective reservoir monitoring
(... this is important!)■ Early EUR (months? years?)
(... prediction/correlation)■ Minimum Well Spacing
(... geology + PVT + modeling(?))
●How do we get there…■ Better understanding of flowback/dewatering
(... optimization)■ Pressure-dependent properties…
(... k, FcD, desorption?)■ Understanding of the pore-scale
(... what flows/when/how)■ Petrophysics
(... conventional petrophysics not adequate)■ PVT
(... oil/gas/condensate/water — HP/HT)
●Facts of life…■ Analogs
(... need to understand uncertainty (very high))■ EUR
(... minimum of 12-18 months for high confidence)■ IP
(... may be uncorrelated with EUR)■ Early Productivity
(... poor wells don't get better)■ Time-Rate Analysis
(... not representative? (chaotic operations))
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Reservoir Engineering Aspects ofUnconventional Reservoirs
How Small is Small?(nano-scale pores)
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]
Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
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?
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
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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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
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 4tan
15128
121
2121
0
0
4.0
01-
2
aa
m
aa
m
aa
m
a
kp
ak
pak
pa
kk
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Reservoir Engineering Aspects ofUnconventional Reservoirs
Time-Rate Analysis
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]
Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
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 (other methods needed).
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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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Time-Rate: Flow Regimes — Multi-Fracture Horizontal Well
Discussion:●Very high permeability case (30 md?) → blame graduate student.●Exhibits various flow regimes.●Note square-root time approximation … poor man's EUR (too high).
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
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 ][1/ )( 4 tatq BLFBLF
Time-Rate: Flow Regimes — Multi-Fracture Horizontal Well
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
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
q
tq
i
bi
i
dtdq
qtD 1)(
constant )(
1 )(
tDdtd
tb
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
of D
(t) a
nd
b(t)
q(t)
D(t)
b(t)
1:2 slope
b(t) ≈ 2
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
PLE Rate Relation:
Decline Function: D(t)
Hyperbolic Function: b(t)
Function: (t)
Time-Rate: Power-Law Exponential Rate Relation
]ˆexp [ˆ)( nii tDtDqtq
)1(ˆ
1)(
nitDnD
dtdq
qtD
nn
i
i ttDDn
nDn
tDdtd
tb
2)1( ] ˆ[
)1(ˆ
)(1
)(
)1(ˆ ni tDnD
)( 1)( tDtdtdq
qtt 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.
Logarithm of Production TimeLo
garit
hm o
f D(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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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Discussion:●EUR is computed at each "time step" (cumulative or incremental).●EUR estimated for each model.●EUR comparison plots probably min/max trends.
d. CEUR master summary plot (all results).
Time-Rate: Continuous EUR
a. Continuous EUR (CEUR) process plots.
b. CEUR hyperbolic, PLE, and q-Gp summary plots.
c. CEUR governing equations.
])(1[/)( )/1( bigi tbDqtgq
]ˆexp [ˆ)( nigi tDtDqtgq
]/[ )( ig i DqGpGiDg iqtgq
[hyperbolic]
[PLE]
[qg(t) vs. Gp(t)]
From: SPE 132352 (2009) Continuous Estimation of Ultimate Recovery, S. Currie, D. Ilk, and T. Blasingame, Texas A&M U.
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Reservoir Engineering Aspects ofUnconventional Reservoirs
Time-Rate-Pressure Analysis
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]
Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Theory:● Palacio and Blasingame [1993]● Mattar and McNeil [1997]● Agarwal et al [1999]
Advantages:● Straightforward and intuitive.● Shut-in pressures NOT required.● Direct estimation of contacted
gas-in-place.
Limitations:● Boundary-dominated flow regime
must exist.
"Flowing Material Balance" Plot:
a. The "Flowing Material Balance" (Normalized Rate-Cumula-tive Function Plot) formulation is derived using the solution for the diffusivity equation during boundary-dominated flow regime. This formulation provides a direct estimate of the contacted gas-in-place using time, flowing wellbore pres-sure, and flowrate data.
Time-Rate-Pressure: Flowing Material Balance Plot
JCPT (June 1997), 52-55.The 'Flowing' Gas Material BalanceL. Mattar and R. McNeil, Fekete Assoc.
Question(s):●What is the "Flowing Material Balance" plot? In
simple terms, pwf(t) data are "converted" to pavg(t) data using the pseudosteady-state flow equation, then plotted as a straight-line extrapolation function and "solved" for gas-in-place.
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
b. "Transformed" data shows fractured well response at early times, very strong evidence of closed system at late times.
a. Raw (daily) rate and pressure data — bottomhole pressures are calculated, note the effect of liquid loading.
(1/4) )(
g
ppss,g
transg q
Gm̂
qpm
(1) )(
g
ppss,g
bdfg q
Gm̂
qpm
Boundary-DominatedFlow
TransientFlow
Question(s):●Can the well-reservoir model be inferred
from such data? Yes.● Is diagnosis sufficient? No, we must
also be able to model/history match data with a model (complete process).
Time-Rate-Pressure: Material Balance Time
? )(1 )/1( bi
gig
tbD
SPE 25909 (1993)Decline Curve Analysis Using Type Curves — Analysis of Gas Well Production DataJ.C. Palacio and T. Blasingame, Texas A&M U.
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Time-Rate-Pressure: Flowback AnalysisSPE 135607A Comprehensive Workflow for Early Analysis and Interpretation of Flowback Data from Wells in Tight Gas/Shale Reservoir SystemsD. Ilk and S.M. Currie, Texas A&M U., D. Symmons, Consultant, J.A. Rushing, Anadarko Petroleum, N.J. Broussard, El Paso, and T.A. Blasingame, Texas A&M U.
a. Crossplot — All wells: qg versus qw.
c. Crossplot — All wells: p2/qg versus t.b. Crossplot — All wells: pcf versus t.
[DI]
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
)ln()ln(
)(, dtdq
qt
tdqd
tcpq
Time-Rate-Pressure: Time-Rate DiagnosticsSPE 135616Hybrid Rate-Decline Models for the Analysis of Production Performance in Unconventional ReservoirsD. Ilk and S.M. Currie, Texas A&M U., D. Symmons, Consultant, J.A. Rushing, Apache, and T.A. Blasingame, Texas A&M U.
a. -derivative — Holly Branch Wells.
)ln()ln()(, dt
dqqt
tdqd
tcpq
)ln()ln()(, dt
dqqt
tdqdtcpq
b. -derivative — "Shale Gas Field C" Wells. c. -derivative — All Models (Holly Branch Well).
[DI]
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
"Shale Gas Field C"
ˆ
ˆ nEUR
Time-Rate-Pressure: Integration of ResultsSPE 140556 (2011)Integration of Production Analysis and Rate-time Analysis via Parametric Correlations — Theoretical Considerations and Practical ApplicationsD. Ilk, DeGolyer and MacNaughton, J.A. Rushing, Apache, and T.A. Blasingame, Texas A&M U.
a. Correlation plot — kcal versus kmeas.
b. Correlation plot — EURcal versus EURmeas.
Horizontal well with multiple vertical fractures:
)1(ˆ1)( ni tDnD
dtdq
qtD
] ˆ e xp [ ˆ)( nii tDtDqtq
Power-Law Exponential Relations:
"Shale Gas Field C" ˆˆ d
ici
b qDnak
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Reservoir Engineering Aspects ofUnconventional Reservoirs
Practical Aspects
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]
Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Practical Aspects: Stimulation
Discussion:● Maximizing SRV (Stimulated Reservoir Volume)
■Build Complexity →Slickwater■Build Conductivity →Hybrid/Gel Systems
● Future Stimulation Challenges:■Can we "rubblize" the reservoir?■Can we "pulverize" the reservoir?■Can we do this with little or no water?
"You only produce from what you frac …"Anonymous
Individual Fractures fromIndividual Perforation Clusters
Complex Fractures fromIndividual Perforation Clusters Project Rulison (1971)
Stimulation using Atomic Weapons
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Practical Aspects: Clean-Up
Discussion:● Build choke profile slowly (2/64ths every 2-3 days).● Hold choke constant once rates peak.● For HPHT systems, start at 10-12/64ths, build to 12-16 64ths.
100 10110-5
102 103
10-4
10-3
Total Fluid Material Balance Time, days
Tota
l Flu
id P
rodu
ctiv
ity In
dex,
STB
/D/p
si
1:2 slopeFormation Linear Flow
(very high fractureconductivity)
Clean-upBehavior
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Dimensionless Time
Dim
ensi
onle
ss P
ress
ure
Practical Aspects: Pressure Transient Analysis
Discussion:● Multiple BHP pressure transient test data sets (5 wells).● Apparent 1:4 slope → low conductivity vertical fractures.● Data are "normalized" (dimensionless) in pressure drop and time.
Apparent 1:4 slope for pressure drop andpressure drop derivative functions
LOW CONDUCTIVITY VERTICAL FRACTURES.
Nearby wellis being stimulated.
1:4 Slope
Nearby wellis being stimulated.
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Reservoir Engineering Aspects ofUnconventional Reservoirs
Challenge Pointsfor Unconventional Reservoirs
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]
Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Challenge Points: "What Keeps Me Up at Night…"
●What we REALLY know…■ Tight gas is relatively easy
(... vertical wells, HP/HT, PVT)■ Gas shales are technically viable as a resource
(… economics?)■ Horizontal multi-fractured wells
(… (now) taken for granted)
●What we THINK know…■ The fracture geometry is
(... planar? complex? who cares?)■ The phase behavior
(… can be extremely complex)■ The ptf to pwf conversion(s)
(... early-time heavy water load?)
●What we may NEVER know…■ Distribution of natural fractures
(... impossible?)■ Transport of gas/liquids in shales
(... via organic matter?)
●What we SHOULD KNOW in the near future…■ Duration of data required for EUR
(... more is always better)■ Better understanding of phase behavior
(... not "conventional")■ Optimal well spacing/orientation/placement
(... do this early!)
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Challenge Points: "Conventional Wisdom…"●Estimated Ultimate Recovery (EUR)?
■ Early EUR?
(... can this be meaningful?)■ EUR = f(t)?
(... how do we incorporate this?)■ Well Spacing?
(... is this really the holy grail?)
●QUANTIFYING reservoir properties?■ Pressure Transient Analysis
(... ultra-low k ... issues?)■ Production Analysis
(... ptf may not be sufficient)■ Petrophysical analysis
(... theory ≠ application)
●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)■ Recovery
(... low to extremely low primary recovery?)
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
●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/Effect of Layering
(... when does it matter?)
●Things that SHOULD help…■ Production Logs
(... but just a snapshot in time)■ Optimal Proppant Design/Placement
(... obvious, but)■ Stimulation Stages/Perforation Clusters
(... geology + logs)
●Things that DEFINITELY WOULD help…■ Measured pwf
(... yes, this is my favorite song)■ Downhole Fluid Sampling
(... sooner or later)■ Horizontal Core
(... why not?)
Challenge Points: "Everybody Has An Opinion"
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Challenge Points: "My Crystal Ball Tells Me…"●EUR:
■ Time-Rate Analyses
(... may not be sufficient)■ Time-Rate-Pressure Analyses
(... requires reservoir model)■ Constraints
(... e.g., 15 years seems reasonable)
●Reservoir Modeling: (i.e., simulators)■ Present
(... conventional models with modifications)■ Near-Future
(... fundamental flow kinetics, complex geometries)■ Distant-Future
(... pore-scale phenomena, nano-scale PVT, ?)
●Reservoir Engineering Tools:■ Material Balance Methods
(... not applicable at reservoir-scale)■ Pressure Transient Tests
(... surprisingly good in cases [need k])■ Production Analysis
(... very good in cases [need good ptf data])■ Reservoir Fluids
(... very complex, near-critical liquids)■ EOR
(... not sure where to start — CO2, lean gas, ???)■ Ad-hoc Tools
(... e.g., Linear flow analysis — lack resolution)
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Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011
Reservoir Engineering Aspects of Unconventional ReservoirsTom Blasingame — Texas A&M University (27 October 2011)
Reservoir Engineering Aspects ofUnconventional Reservoirs
End of Presentation
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
Presentation at SPE GCS Reservoir Study GroupHouston, TX (USA) — 27 October 2011