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Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
ide
—1/
24
Tight Gas/Shale Gas Well Performance Analysis —Present and Future Views
Presentation at Shell (Houston) 02 September 2009 — Houston, TX
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
ide
—2/
24
Tight Gas/Shale Gas Well Performance Analysis:
Present Views
Presentation at Shell (Houston) 02 September 2009 — Houston, TX
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
ide
—3/
24
Decline Analysis — Arps Relations: Base Relations
Case Rate-Time Relation Cumulative-Time Relation
]exp[ tDqq igig −=
)/1()(1 bi
gig
tbD
+=
)(1 tDq
qi
gig +=
Exponential: (b=0)
Hyperbolic: (0<b<1)
Harmonic: (b=1)
]]exp[[1 tDDq
G ii
gip −−=
])(1[1 )(1
)/1(1 bi
i
gip tbD
Dbq
G −+−−
=
)ln(1 tDDq
G ii
gip +=
Loss Ratio:
Loss Ratio Derivative:
]exp[ /
1 tDqqdtdq
qD igig
g
g −=→−≡
)/1()(1
/ bi
gig
g
g
tbD
dtdqq
dtdb
+=→
⎥⎥⎦
⎤
⎢⎢⎣
⎡−≡
Trans., AIME (1945) 160, 228-247.Analysis of Decline CurvesJ.J. Arps
Question(s):●How were the Arps' rate relations derived?
The BASIS for the Arps' relations — i.e., the behavior of the D- and b- parameters, is derived from OBSERVATIONS. These are empirical results.
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
ide
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24
x
yPressure
MonitoringPoint No. 1
PressureMonitoringPoint No. 2
HydraulicFracture
Wellbore
X
X
x
y
x
yPressure
MonitoringPoint No. 1
PressureMonitoringPoint No. 2
HydraulicFracture
Wellbore
X
X
Numerical Model Considers:●Reservoir Layering.●kv/kh ratio.●Fracture Length, xf.●Fracture Conductivity, FcD.Analysis/Validation Approach:●Fit q(t) with Arps' hyperbolic relation.●Compare reserves to model at 30 years.
Decline Analysis: Tight Gas SystemsSPE 109625 (2007)Estimating Reserves in Tight Gas Sands at HP/HT Reservoir Conditions: Use and Misuse of an Arps Decline Curve MethodologyJ.A. Rushing, A.D. Perego, R.B. Sullivan, Anadarko Petroleum, and T.A. Blasingame, Texas A&M U.
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
ide
—5/
24
Exponential: (b=0)
Hyperbolic: (0<b<1)
Harmonic: (b=1)
⎥⎦
⎤⎢⎣
⎡
−≡⎥
⎦
⎤⎢⎣
⎡−= −
i
gibpgig Db
qG
GG
qq)(1
1 )1(1
⎥⎥⎦
⎤
⎢⎢⎣
⎡−= pgii
gig GqDqq exp
Case Plotting Function
pGgq versus
⎥⎥⎦
⎤
⎢⎢⎣
⎡−GpG
gq 1log versus)log(
pGgq versus)log(
⎥⎥⎦
⎤
⎢⎢⎣
⎡≡−=
i
giDq
GpGiDgiqgq
Decline Analysis: EUR Plots (Arps' relations)SPE 98042 (2005)A Production-Based Method for Direct Estimation of Gas-in-Place and ReservesT.A. Blasingame, Texas A&M U. andJ.A. Rushing, Anadarko Petroleum.
Question(s):●Graphical extrapolations of EUR? Family of "EUR
plots" derived from the Arps' exponential and hyperbolic relations. Hyperbolic "EUR plot" requires a modular computing environment (e.g., a spreadsheet), as multiple variables are established simultaneously.
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
ide
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24
⎥⎥⎦
⎤
⎢⎢⎣
⎡≡−=
i
giDq
GpGiDgiqgq⎥⎦
⎤⎢⎣
⎡
−≡⎥
⎦
⎤⎢⎣
⎡−= −
i
gibpgig Db
qG
GG
qq)(1
1 )1(1
Hyperbolic Decline: (0<b<1) Exponential Decline: (b=0)
a. "Hyperbolic Plot:" (log-log format) —Provides a straight-line for ALL cases.
b. "Hyperbolic Plot:" (Cartesian format) —Provides a straight-line ONLY for b=0 case.
Decline Analysis: Blasingame-Rushing EUR PlotSPE 98042 (2005)A Production-Based Method for Direct Estimation of Gas-in-Place and ReservesT.A. Blasingame, Texas A&M U. andJ.A. Rushing, Anadarko Petroleum.
Question(s):● Is there a distinctly unique mechanism for
establishing the validity of the hyperbolic relation? Yes, the "hyperbolic" decline "type curve" plot yields straight-line trends.
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
ide
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24
Theory:●pi < 6000 psia.●pwf = constant.
Rate-Cumulative Result:
Gzpzp
qD
GGD
GDqq
ii
wfwf
gii
pi
pigig
⎥⎥
⎦
⎤
⎢⎢
⎣
⎡⎥⎦
⎤⎢⎣
⎡−
=
+−=
2
2
//
1
2
where21
) (gas 1
eq.) flow ( 22
MBEGG
zp
zp
PSSzp
zpCq
p
ii
wf
wfg
⎥⎥⎦
⎤
⎢⎢⎣
⎡−=
⎥⎥⎥
⎦
⎤
⎢⎢⎢
⎣
⎡
⎥⎥⎦
⎤
⎢⎢⎣
⎡−⎥⎦
⎤⎢⎣⎡=
Buba Gas Reserves Estimation Plot:
a. The "Buba" method utilizes only rate-time data (cumulative is cal-culated) in order to create a series of semi-analytical plotting functions for the estimation of gas reserves.
b. The "Buba" approach is based on the Ansah et al result for a semi-analyti-cal gas flow solution.
Decline Analysis: Buba Rate-Cumulative RelationM.S Thesis, Texas A&M University, College Station, TX (2003)Direct Estimation of Gas Reserves Using Production DataI.M. Buba, Texas A&M U.
Question(s):● Is there a semi-rigorous mechanism for correlating
qg and Gp? Yes, the "Buba" relation and associated plots provide a unique extrapolation of gas-in-place.
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
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24
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.
Decline Analysis: "Flowing Material Balance" PlotJCPT (June 1997), 52-55.The 'Flowing' Gas Material BalanceL. Mattar and R. McNeil, Fekete Associates
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.
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
ide
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24
Transient Stems: (left)Numerical or analytical model (pwf = constant).q(t) is concave up.
Depletion Stems: (right)q(t) is concave down.b=0: pwf = con.b=1: qo = con. (qo/Δp).b>1: transient flow or external drive energy.λ: numerical gas flow solutions (λ =f(pwf/(pi)).
Reservoir Properties:k — y-axis match.G — x&y-axis matches.s — reD match.
a. Original format Fetkovich-Carter type curve — most important observation is that 0<b<1. For cases where b>1; either transient flow OR external energy is being added to the reservoir system.
swwa
wae
gigi
wfiDd
wae
wewtigi
Dd
err
rrB.
ppkhtqq
rr
rrrc
kt.t
−=
⎥⎥⎦
⎤
⎢⎢⎣
⎡−⎥
⎦
⎤⎢⎣
⎡
−=
⎥⎥⎦
⎤
⎢⎢⎣
⎡−⎥
⎦
⎤⎢⎣
⎡⎥⎥
⎦
⎤
⎢⎢
⎣
⎡−⎥
⎦
⎤⎢⎣
⎡=
21ln 2141
)( )(
21ln 1
21
1 006330 22
μ
φμ
Variables for the Carter Decline Type Curve
Decline Analysis: Fetkovich-Carter Type CurveSPEJ (October 1985) 719-728.Type Curves for Finite Radial and Linear Gas Flow Systems: Constant Terminal Pressure CaseR.D. Carter, Amoco Production
JPT (June 1980) 1065-1077.Decline Curve Analysis Using Type CurvesM.J. Fetkovich, Phillips Petroleum
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
ide
—10
/24b. "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) )(
⎥⎥⎦
⎤
⎢⎢⎣
⎡≈
⎥⎥⎦
⎤
⎢⎢⎣
⎡Δ
g
ppss,g
transg qG
m̂qpm
(1) )(
⎥⎥⎦
⎤
⎢⎢⎣
⎡≈
⎥⎥⎦
⎤
⎢⎢⎣
⎡Δ
g
ppss,g
bdfg qG
m̂qpm
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).
Decline Analysis: Palacio 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.
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
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SPE 116731: Inadequacy of Arps' Rate RelationsASSUMPTION: The Arps decline para-
meter, b, defines the decline behavior...
REALITY: Difficult to identify the correct b-parameter during the early decline period —greatly impacts reserve estimates.
b. (Log-log plot) Production forecast of a tight gas well.a. (Semilog plot) Production forecast of a tight gas well.
SPE 116731 (2008)Exponential vs. Hyperbolic Decline in Tight Gas Sands — Understanding the Origin and Implications for Reserve Estimates Using Arps' Decline Curves.D. Ilk, Texas A&M U., J.A. Rushing and A.D. Perego, Anadarko Petroleum, and T.A. Blasingame, Texas A&M U.
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
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●Rate Function Definitions:– Loss Ratio:
– Derivative of Loss Ratio:
– Exponential and Hyperbolic Rate Relations:
●Cause and Effect:– Hyperbolic relation is mis-applied to transient data.– What is the "characteristic behavior" of the D and
b-parameters? Evaluate continuously using data.
or /
1⎥⎦
⎤⎢⎣
⎡−≡−≡dQdqD
dtdqq
D
⎥⎦
⎤⎢⎣
⎡⎥⎦⎤
⎢⎣⎡≡⎥
⎦
⎤⎢⎣
⎡−≡⎥⎦
⎤⎢⎣⎡≡
DdQdqb
dtdqq
dtd
Ddtdb 1or
/1
)/1(][1 con or ; ]exp[ con b
i
iii
tbD
qqbtDqqD
+=→=−=→=
SPE 116731: Definitions of Rate Functions
(Exponential Decline) (Hyperbolic Decline)
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
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[ ]Bni AtDtDnD
dtdq
qD −
∞−−
∞ +≈+≈−≡ ˆ1 )1(
●Observed Behavior of the "Decline" Parameter [D(t)]:
●Solving for Flowrate [q(t)] Using the D(t) Relation:
] ˆ exp[ ˆ nii tDtDqq −−= ∞
●Solving for the "Hyperbolic" Parameter [b(t)]:
nn
i
i ttDDn
nDnb −
−∞+
−= 2)1( ] ˆ[
)1(ˆ
SPE 116731: "Power-Law Exponential" Rate Result
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
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●Discussion: Small "Waterfrac" Gas Well■ Liquid loading effects are obvious in the latter portion of the flowrate data.■ The onset of the boundary-dominated flow regime is observed.■ We observe a very good match of the flowrate data using D∞=0.
SPE 116731: q-D-b Plot — Small WF Tight Gas Well
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
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●Discussion: Large "Waterfrac" Gas Well■ Erratic rate behavior caused by liquid loading is seen at late times.■ Outstanding matches of the computed D- and b-parameters with the
power-law exponential model are observed.
SPE 116731: q-D-b Plot — Large WF Tight Gas Well
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
ide
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/24
Tight Gas/Shale Gas Well Performance Analysis:
Future View
Presentation at Shell (Houston) 02 September 2009 — Houston, TX
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
ide
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/24
b. Elliptical flow type curve solution — high fracture conductivity case.
a. Elliptical flow type curve solution — low fracture conductivity case.
Vertical TG/SG Wells: Elliptical Flow Domination
c. Elliptical boundary configurations (finite con-ductivity fracture case [Amini, et al (2007)].
SPE 106308 (2007)Evaluation of the Elliptical Flow Period forHydraulically-Fractured Wells in Tight GasSands — Theoretical Aspects and PracticalConsiderationsS. Amini, D. Ilk, and T. A. Blasingame,SPE, Texas A&M U.
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
ide
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a. Pressure profile at 0 year (0 hr).
b. Pressure profile at 1 year (8768 hr).
c. Pressure profile at 5.59 years (49,010 hr).
d. Pressure profile at 9.26 years (81,200 hr).
e. Pressure profile at 18.44 years (161,700 hr).
f. Pressure profile at 44.10 years (386,600 hr).
Results Generated Using:Ecrin Product Suite, Kappa Engineering, Sophia-Antipolis, France (2008).
Vertical TG/SG Wells: Elliptical Flow Domination
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
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a. Rate performance behavior for a horizontal well with 4 trans-verse fractures — infinite-acting reservoir (analog to van Kruysdijk and Dullaert work). Fine-scale numerical model .
Horizontal TG/SG Wells: Compound Linear Flow
c. Schematic diagram for the "compound linear flow" concept [van Kruysdijk and Dullaert (1989)].
Presented at the 2nd European Conference on the Mathematics of Oil Recovery, Cambridge, England (1989).A Boundary Element Solution of the Transient Pressure Response of Multiply Fractured Horizontal WellsC.P.J.W. van Kruysdijk and G.M. Dullaert, Shell
b. Specialized derivative plot (ref: van Kruysdijk and Dullaert) for a horizontal well with 4 transverse fractures — infinite- and finite-acting reservoir cases. Fine-scale numerical model .
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
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Base Simulation Modelfor Horizontal Well with Multiple Hydraulic Fractures
Top View HorizontalWell
MultipleVertical
Fractures
SPE 119897: Schematic Model for Simulation
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
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●Discussion: Horizontal Wells with Transverse Fractures■ Very high resolution simulation case.■ Very good D-parameter and good b-parameter computed from results.■ Excellent rate match using the new model (all regimes).
SPE 119897: q-D-b Plot — Numerical SimulationFinite-Acting
Reservoir Case
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
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●Discussion: Horizontal Wells with Transverse Fractures■ Very high resolution simulation case.■ Transient D- and b-parameters at late times (quasi-radial flow).■ Impossible to predict reserves.
SPE 119897: q-D-b Plot — Numerical SimulationInfinite-Acting
Reservoir Case
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
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Horizontal TG/SG Wells: Diagnostics?Q1.Compound Linear Flow Domination? (transient flow)A1. Possibilities for estimating reservoir properties:
a. Just give up — impossible to resolve anything. (default)b. "Lump" k, xf, and Lwell into a "parameter." ("mechanistic model")c. Develop testing practices to estimate properties. (maybe…)d. Other model concepts (e.g., propagating ellipse). (very tedious)
Q2.Estimating Reserves?A2. Issues:
a. Extremely long transition to boundary-dominated flow. (reality)b. Hyperbolic rate relation will overestimate reserves. (as always)c. Power-law/exponential rate relation? (more validation)
Q3.Role of simulation/modeling?A3. In the short-term, simulation/modeling is the primary
tool at our disposal — the analogy of using a hammer in place of a screwdriver comes to mind… (sometimes effective, but always a sub-optimal solution — particu-larly in the hands of children).
Presentation at Shell (Houston)02 September 2009 — Houston, TX
Tight Gas/Shale Gas Well Performance Analysis — Present and Future ViewsT.A. Blasingame (02 September 2009) Sl
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Tight Gas/Shale Gas Well Performance Analysis —Present and Future Views
End of Presentation
Presentation at Shell (Houston) 02 September 2009 — Houston, TX
Tom BLASINGAMEDepartment of Petroleum Engineering
Texas A&M UniversityCollege Station, TX 77843-3116 (USA)
+1.979.845.2292 — [email protected]