RPSEA Review Meeting April 6-7, 2010, Golden, CO 1 Optimizing In Fill Well Drilling - Wamsutter Field Mohan Kelkar The University of Tulsa Akhil Datta-Gupta Texas A & M University
Feb 25, 2016
RPSEA Review MeetingApril 6-7, 2010, Golden, CO
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Optimizing In Fill Well Drilling - Wamsutter Field
Mohan KelkarThe University of Tulsa
Akhil Datta-GuptaTexas A & M University
RPSEA Review MeetingApril 6-7, 2010, Golden, CO
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Outline
• Background• Objectives• Project Management• Project Deliverables• Progress to Date• Summary
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Wamsutter Field
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Wamsutter Field
•Over 2,000 square miles•Two main units – Lewis and
Almond• Tight gas reservoir, k < 0.1 md•Currently developed on 80 acre
spacing
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Wamsutter FieldStatic Continuity
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Static vs. Dynamic Continuity
• Static continuity appears to be strong indicating a significant and efficient drainage using 160 acre spacing
• Small scale heterogeneities in the reservoir indicate significant dynamic discontinuities
• The presence of small scale heterogeneities is verified by performance of 80 acre spacing wells
• Average performance of 80 acre spacing wells is 50 to 70 % of the performance of 160 acre spacing wells
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Objectives
• Determine and quantify the importance of small scale heterogeneities on the performance of wells
• Quantify the potential recovery from in fill wells using production data analysis as well as simulation
• Identify sweet spots for possible locations for 40 acre spacing wells
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Project Management
• Principal Investigator – The University of Tulsa
• SubcontractorsDevon EnergyTexas A & M University
• Based on the results of the study, Devon is planning to drill seven new wells in the field
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Project Deliverables
• Methodology to determine the incremental vs. acceleration gas production from in fill wells
• Methodology to account for and, preservation of, sand connectivity in coarse scale models
• Procedures for high and low grading areas for in fill well potential
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Progress to DateArea of Concentration
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Data Collected
• Area of interest is 3x3 sections in 16N 93 W township with one additional section on all sides which covers 5 x5 sections (total of 25 sections)
• A total of 83 wells are drilled in the area• Log data as well as production data are
available from most of the wells
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Production Data Analysis
University of Tulsa
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Introduction
• Homogeneous and heterogeneous reservoirs will exhibit different behavior when in fill wells are drilled: Initial production rates will indicate access
to new reservesDifference in decline rates from the
surrounding wells will indicate communication
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Homogeneous Reservoir
×: Original well○: Infill wells
0 5 10 15 20 25 30 35 400
1
2
3
4
5
6
7
Original well
Infill well
Drill new wells
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Heterogeneous Reservoir
×: Original well○: Infill wells
0 5 10 15 20 25 30 35 400
1
2
3
4
5
6
7
Original well
Infill well
Drill new wells
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Objectives
• Develop a methodology to predict the gas which is “stolen” by new wells.
• Using the existing production data, determine the in fill well EUR
• Determine the contribution of acceleration and incremental potential.
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Approach
• Determine an appropriate time function such that cumulative production is linearly related.
• Divide the data into chronological groups so that average behavior can be predicted.
• Plot cum production vs. time function and examine inflection in the graph as successive groups of wells are drilled.
• Compare EUR calculated from this method with the EUR reported by companies.
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Southwest Energy
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Type Curve ExtrapolationSouthwest Energy
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Chesapeake Energy
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Type Curve ExtrapolationChesapeake Energy
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Approach
• Determine a function of time such that cumulative production is directly related.
• Divide the data into chronological groups so that average behavior can be predicted.
• Plot cum production vs. time function and examine inflection in the graph as successive groups of wells are drilled.
• Compare EUR calculated from this method with the EUR reported by companies.
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Field Data
183050 183550 184050 184550 185050 185550 1860501434000
1434500
1435000
1435500
1436000
1436500
1437000
1437500
1438000
1438500
123456
7 8 9 10 11 12
131415161718
19 20 21 22 23 24
30 29 28 27 26 25
31 32 33 34 35 36
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Grouping
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Approach
• Determine a function of time such that cumulative production is directly related.
• Divide the data into chronological groups so that average behavior can be predicted.
• Plot cum production vs. time function and examine inflection in the graph as successive groups of wells are drilled.
• Compare EUR calculated from this method with the EUR reported by companies.
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Example
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Example
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Approach
• Determine a function of time such that cumulative production is directly related.
• Divide the data into chronological groups so that average behavior can be predicted.
• Plot cum production vs. time function and examine inflection in the graph as successive group of wells are drilled.
• Compare EUR calculated from this method with the EUR reported by companies.
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EUR Comparison
0 1 2 3 4 5 6 70
1
2
3
4
5
6
7
EUR(TU), Bscf
EUR
(Ope
rato
r), B
scf
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Group EUR Comparison
EUR(ours) EUR(Operator)
1st group 3.31 3.32
2nd group 3.01 3.07
3rd group 2.32 2.34
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Approach
• For every “child” well, calculate average Incremental and Acceleration components.
• Plot Acceleration percentage, Incremental percentage and total EUR as a function of spacing.
• Recommend potential sections where in fill well potential is the greatest.
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Calculation
• Acceleration vs. IncrementalTotal EUR for 2nd group per well = 3.57 BCFAcceleration EUR for 2nd group per well = Decreased EUR = 0.24 BCF Incremental EUR for 2nd group per well= Total EUR - Acceleration EUR = 3.57 - 0.24 = 3.33 BCF
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Approach
• For every “child” well, calculate average Incremental and Acceleration component.
• Plot Acceleration percentage, Incremental percentage and total EUR as a function of spacing.
• Recommend potential sections where in fill well potential is the greatest.
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Wamsutter FieldMultiple Section Analysis
225352.784699999 226902.709091999 228452.633483999 230002.557875999 231552.482267999 233102.40665999974851.19
76511.995457
78172.800914
79833.606371
81494.411828
83155.217285
1 2 3 4 5
6 7 8 9 10
11 12 13 14 15
16 17 18 19 20
21 22 23 24 25
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ACC vs. INCE-W direction
120 175 384 6400.000
0.500
1.000
1.500
2.000
2.500
3.000
3.500
4.000
4.500
5.000
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
EW-7,8,9ACC+INC
ACC%
INC%
Spacing, acre
AC
C+I
NC
,bsc
f
AC
C&
INC
%
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ACC vs. INCN-S direction
91 128 320 4800.000
1.000
2.000
3.000
4.000
5.000
6.000
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
NS-9,14,19ACC+INC
ACC%
INC%
Spacing, acre
AC
C+I
NC
,bsc
f
AC
C&
INC
%
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Extrapolation at 80 acrespacing
Result:1.35 bscf
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Approach
• For every “child” well, calculate average Incremental and Acceleration component.
• Plot Acceleration percentage, Incremental percentage and total EUR as a function of spacing.
• Recommend potential sections where in fill well potential is the greatest.
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Extrapolation Results
Total (bscf) %(ACC) %(INC)
EW-7,8,9 1.350 88% 12%
EW-12,13,14 2.300 43% 57%
EW-17,18,19 2.140 84% 16%
NS-7,12,17 0.900 70% 30%
NS-8,13,18 1.750 91% 9%
NS-9,14,19 2.150 64% 36%
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Recommended Sections
Total (bscf) %(ACC) %(INC)
EW-7,8,9 1.350 88% 12%
EW-12,13,14 2.300 43% 57%
EW-17,18,19 2.140 84% 16%
NS-7,12,17 0.900 70% 30%
NS-8,13,18 1.750 91% 9%
NS-9,14,19 2.150 64% 36%
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Summary
• Using a newly developed methodology, we determined the acceleration and incremental contributions for in fill wells
• We have developed user friendly VBA program which is given to Devon for testing
• We validated our method in Wamsutter and Pinedale gas fields.
• Based on our recommendation, Devon would drill seven wells in Wamsutter field starting August.
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Streamlines to Determine Connected Volume
Texas A & M University
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Advantages of streamline tracing for gas reservoir characterization Easier and less expensive Better visualization of flow in the reservoir
Calculating drainage volume based on streamlines Optimizing well spacing Optimizing well completion design and fracturing specially for tight
gas reservoirs
Why Streamline?
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Diffusive TOF
• DTOF is similar to the TOF but it uses diffusivity coefficient instead of velocity in TOF equation.
• : Diffusive Time of flight can be analytically calculated with single flow simulation. Front of DTOF represents the volume drained.
• DTOF is more efficient if Multi-well testing is needed.
• : The sensitivities are calculated in each well with single simulation, so drainage volume is calculated without perturbation or shutting wells down.
• DTOF can be used in compressible flow
• : Diffusive Time of flight calculated based on flux, so we can easily use it for compressible flow.
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,~,~,~
0,,
2 xxxxx
xx
xxxx
PkkPPi
kc
tPkttPc
t
t
xx
xx
x
x
0
0
,~
,~
AeP
i
AeP
i
kk
ki
wave of amplitude the to relatethat functions real :
wave gpropagatin a of phase the :xx
kA *
Fourier transform of diffusivity equation
Asymptotic solution (Vasco et al. 2000)
: From this solution we just keep the high frequency part which implies
propagation of the sharp front (Only K=0)
Diffusive TOF formulation
... (1)
... (2)
... (3)
... (4)
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xx
xxx
xxx
dc
k
t
1
Diffusive TOF
TOF
xv
xxxv dˆ1ˆ
Diffusive TOF
: Diffusive TOF is the function of model parameters (Invariant with time)
: TOF is the function of given velocity field (function of time)
... (5)
... (6)
... (7)
:Substitute equation 4 in equation 2 and equate coefficients:
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Peak Arrival Time
6)(
04
)(23
2)(,
2
)(,
2
max
2
223
25
4)(
0
4)(
30
2
2
xt
txttexA
ttP
et
xAtP
tx
tx
xx
xx
Constant rate production at the producer When derivative of the pressure in a grid block
reaches to a maximum is assumed as pressure peak arrival time for that grid block.
Equation (8) is used to go from time of flight domain to physical time domain in 3-D model.
For 2-D case this equation changes to:
... (8)
4)(2
maxxt
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P1
P4P8P3
P6P5
P2P7P1
P4P8P3
P6P5
P2P7
*JongUk,Kim et al (2009)
Permeability Field DTOF
Peak Arrival Time (Oil Case)
This shows that we can use Diffusive TOF calculations to represent the peak arrival time to calculate drainage volume.
Time Derivative
0
0.004
0.008
0.012
0.016
0 20000 40000 60000 80000 100000
Time (sec)
dP/d
t
p1
p2p3
p4
p5p6
p7
p8
24,839 sec
Time Derivative
0
0.004
0.008
0.012
0.016
0 20000 40000 60000 80000 100000
Time (sec)
dP/d
t
p1
p2p3
p4
p5p6
p7
p8
24,839 sec
Peak Arrival Time
This is the time that pressure front reaches to producer #1.
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AdvancesTo be able to use this approach for gas fields same calculations
can be done based on the ( pressure square approach) . Accordingly we can show that the equation (1)-(8) still holds for gas reservoirs.
The only modification is that compressibility has to be addressed correctly, so we modified the diffusivity coefficient in each grid block as follow:- Previously : use constant oil compressibility
- Now : Calculate total compressibility from restart file
This modification allows to correctly calculate DTOF when multiple phases exist.
)1:()( dP
dBB
cccScScScc
k i
iirwwooggt
jtjj
jj
):()(
Constcc
kt
itjj
jj
2P
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Homogeneous Model
HeterogeneousModel
Diffusive TOF vs. Peak Time(2-D Single Phase GAS)
Diffusive TOF : DTOF
0.01 day
0.05 day
0.1 day
4)(2
maxxt
P.A.T DTOF P.A.T
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Field Case (Wamsutter Field- Tight Gas Reservoir) UPGRIDDING
Reduce the number of grid blocks from four million to about 700,000 (Faster Simulations)
Preserving the fine scale model dynamic behavior as good as possible.
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Field Case (Wamsutter Field)
• Statistical Upgridding of the field
• We use Pressure Based Method upgridding (CONNECT – UpGrid)
• This method is based on combining layers with similar pressure profile and minimum velocity difference
• In Design Factor graph we use the maximum points. (Biggest contrast to proportional model)
Original Size : 98 × 112 × 361
= 3,962,336
Coarse scale Size : 98 × 112 × 65
= 713,440 (18% of original size)
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Field Case (Wamsutter Field)
Section of the reservoir (18× 15× 65)
Original Size : 98 × 112 × 65
Permeability Field (0.0001-3 md)
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Section of Wamsutter Gas Field ( DTOF)
1 year
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5 year
Section of Wamsutter Gas Field ( DTOF)
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Drainage Volume Calculations
0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,0000
2,000,000
4,000,000
6,000,000
8,000,000
10,000,000
12,000,000
14,000,000
2114721148
Time ( Days )
Dra
inag
e Vo
lum
e
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Drainage Volume Calculations
0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,0000
2,000,000
4,000,000
6,000,000
8,000,000
10,000,000
12,000,000
14,000,000
16,000,000
18,000,000
20,000,000
211472114821147-Single WellIncerement
Time ( Days )
Drai
nage
Vol
ume
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Field Case (Wamsutter Field- Tight Gas Reservoir)
Southwest Wyoming ( Number of the Wells : 85)
Permeability Field
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Wamsutter Gas Field (Diffusive TOF)
25 year
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Total Drainage Volume Calculations
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Drainage Volume Whole Field
# 20222#
20032 # 20196
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Well location and Streamlines
# 20032
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Drainage Volume – # 20032
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Summary
• We can use streamlines to visualize the pressure propagation in the gas reservoirs.
• Diffusive time of flight is a useful tool to calculate the pressure front.
• By calculating the drainage volume changes, we can quantify effect of new infill wells on the current producers.
• DTOF can facilitate the integration of the high resolution pressure data into history matching process.
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Future Work
Optimized well placement based on the drainage volume
Optimized well completion based on the drainage volume
Including multi-stage fracturing
High resolution transient pressure history matching for
gas fields