Shallow Clastics Field
SC Field F13WSC Wells Skin Analysis
Introduction • Three highly deviated wells (>80 degree): – Completed OHGP and equipped with down hole PDG – Completed in H1 sand
• The H1 sand is laminated sandstone • Four shut-ins for each well are analyzed in this work (i.e. 12 tests)
Procedure • To eliminate effect of interference between wells, only the first 4 hours of the shut-in period for each test was used. (Confirmed from derivative plot that pseudo-radial flow period exists within this period) • Evaluate S and K from three specialized plots: Horner, MDH and Semi-log plot • Results from the three plots are used to estimate the best fit regression model • S due to turbulence, geometry, and pressure drop to gauge from top perforation are estimated • By subtracting these skins from total skin, we can get skin due to damage + gravel pack together (Sd+GP) • For each well, by comparing Sd+GP in different times, damage can be detected (assuming SGP is constant)
Process to Analyze Hz Well Skins 1. Match pseudo-radial flow period with vertical well model to get thickness-based pseudo-radial skin. 2. Determine geometric skin: • •
Determine # of beds. Use # of beds to determine geometric skin from Philplot.
3. Determine skin due to turbulence 4. Correct for gauge-depth effects (friction). 5. Skin due to (Damage+Gravel Pac) = Pseudo-radial – geometric – turbulence – correction for gauge depth Derivative
Rate-Dependant Skin
Geometric Skin Estimation
Pressure Drop to gauge-depth
Results Well Name
F13WSC-1
F13WSC-2
F13WSC-3
Date
St
Sturb
Sgeo
Jun-06 Nov-06 Feb-07 Apr-08 Jun-06 Nov-06 Feb-07 Apr-08 Jun-06 Nov-06 Feb-07 Apr-08
39.00 41.60 34.50 32.45 10.00 8.85 12.30 11.34 28.27 22.00 26.06 28.00
0.86 1.06 0.54 0.43 0.83 0.67 0.71 1.20 0.81 0.81 0.76 1.06
-3.80 -3.80 -3.80 -3.80 -3.39 -3.39 -3.39 -3.39 -3.74 -3.74 -3.74 -3.74
Correction to Gauge Depth DP, psi 46.80 68.12 16.74 11.24 30.98 20.98 25.04 68.98 31.99 30.57 29.66 59.52
S 24.76 27.22 7.79 4.41 5.83 4.60 5.92 8.35 10.13 8.35 10.16 12.81
Sd+GP
kh, md.ft
17.18 17.12 29.98 31.40 6.73 6.97 9.06 5.18 21.07 16.58 18.88 17.87
117150 106425 56348 38198 34000 31800 38300 34000 63600 53600 67500 60000
• • •
• •
• •
Conclusion &recommendations
From Sd+GP, F13WSC-1 seems to be badly damaged with time. From KH analysis, F13WSC-1 seems to loose some of its producing intervals with time (assuming K is constant) F13WSC-2, the Sd+GP is not stable, almost constant (about 7) till Nov 06, increased in Feb 07 to 9 and then decreased to 5in Apr 08. Generally we can say no damage. F13WSC–3 looks OK also. Although starting with high Sd+GP, but it is almost constant after this (17-19). Based on Sd+GP values obtained at the initial life of the wells, skin due to gravel seems to be high in F13WSC-1 and –3 (Longer AHD wells), compared to F13WSC-2 (Shortest AHD well) which has relatively low skin. A stimulation job in F13WSC-1 is recommended to improve its productivity and bring the lost intervals back to production Future build-up analysis should be investigated to keep close eye on skin performance.
Back-up
F13WSC-1 F13WSC1_Jun06_BU.ks3 - skin F13WSC1_Nov06.ks3 - skin F13WSC1_Feb07_BU.ks3 - skin F13WSC1_Apr08_BU.ks3 - skin (ref)
1E+7
RF 1E+6
1E+5 1E-5
1E-4
1E-3
0.01
0.1
Compare files: dm(p) and dm(p)' [psi2/cp] vs dt [hr]
1
F13WSC-2 F13WSC2_Jun06_BU.ks3 - Analysis 2 F13WSC2_Nov06.ks3 - Analysis 10 F13WSC2_Feb07_BU.ks3 - Analysis 2 F13WSC2_Apr08_BU.ks3 - Analysis 1 (ref)
1E+7
RF 1E+6
1E+5 1E-4
1E-3
0.01
0.1
Compare files: dm(p) and dm(p)' [psi2/cp] vs dt [hr]
1
F13WSC-3 F13WSC3_Jun06_BU.ks3 - skin F13WSC3_Nov06.ks3 - skin F13WSC3_Feb07_BU.ks3 - skin F13WSC3_Apr08_BU.ks3 - skin (ref)
1E+7
RF 1E+6
1E+5 1E-4
1E-3
0.01
0.1
Compare files: dm(p) and dm(p)' [psi2/cp] vs dt [hr]
Back to Process
1
Geometric Skin Estimation
-Number of zones is given by PP -Sgeo from Fair Plot
Geometric-Skin Factors for Slant Wells 0 -1 -2 -3
Skin
-4 -5 -6 -7 -8 -9
SPE 104480 by P.S. Fair
-10 0.1
1
10
30
1000
10000
hbed/rw
Back to Process 15
100
45
60
75
80
84
86
88
89
89.5
89.9
Non-Darcy Skin Rate-Dependant Skin
Back to Process
Equivalent Skin Due to Pressure Drop to gauge-depth
DPF is estimated from tubing lift curves correlations (Prosper)
Back to Process
Introduction • Three highly deviated wells (>80 degree): – Completed OHGP and equipped with down hole PDG – Completed in H1 sand
• The H1 sand is laminated sandstone • Four shut-ins for each well are analyzed in this work (i.e. 12 tests)
Procedure • To eliminate effect of interference between wells, only the first 4 hours of the shut-in period for each test was used. (Confirmed from derivative plot that pseudo-radial flow period exists within this period) • Evaluate S and K from three specialized plots: Horner, MDH and Semi-log plot • Results from the three plots are used to estimate the best fit regression model • S due to turbulence, geometry, and pressure drop to gauge from top perforation are estimated • By subtracting these skins from total skin, we can get skin due to damage + gravel pack together (Sd+GP) • For each well, by comparing Sd+GP in different times, damage can be detected (assuming SGP is constant)
Process to Analyze Hz Well Skins 1. Match pseudo-radial flow period with vertical well model to get thickness-based pseudo-radial skin. 2. Determine geometric skin: • •
Determine # of beds. Use # of beds to determine geometric skin from Philplot.
3. Determine skin due to turbulence 4. Correct for gauge-depth effects (friction). 5. Skin due to (Damage+Gravel Pac) = Pseudo-radial – geometric – turbulence – correction for gauge depth Derivative
Rate-Dependant Skin
Geometric Skin Estimation
Pressure Drop to gauge-depth
Results Well Name
F13WSC-1
F13WSC-2
F13WSC-3
Date
St
Sturb
Sgeo
Jun-06 Nov-06 Feb-07 Apr-08 Jun-06 Nov-06 Feb-07 Apr-08 Jun-06 Nov-06 Feb-07 Apr-08
39.00 41.60 34.50 32.45 10.00 8.85 12.30 11.34 28.27 22.00 26.06 28.00
0.86 1.06 0.54 0.43 0.83 0.67 0.71 1.20 0.81 0.81 0.76 1.06
-3.80 -3.80 -3.80 -3.80 -3.39 -3.39 -3.39 -3.39 -3.74 -3.74 -3.74 -3.74
Correction to Gauge Depth DP, psi 46.80 68.12 16.74 11.24 30.98 20.98 25.04 68.98 31.99 30.57 29.66 59.52
S 24.76 27.22 7.79 4.41 5.83 4.60 5.92 8.35 10.13 8.35 10.16 12.81
Sd+GP
kh, md.ft
17.18 17.12 29.98 31.40 6.73 6.97 9.06 5.18 21.07 16.58 18.88 17.87
117150 106425 56348 38198 34000 31800 38300 34000 63600 53600 67500 60000
• • •
• •
• •
Conclusion &recommendations
From Sd+GP, F13WSC-1 seems to be badly damaged with time. From KH analysis, F13WSC-1 seems to loose some of its producing intervals with time (assuming K is constant) F13WSC-2, the Sd+GP is not stable, almost constant (about 7) till Nov 06, increased in Feb 07 to 9 and then decreased to 5in Apr 08. Generally we can say no damage. F13WSC–3 looks OK also. Although starting with high Sd+GP, but it is almost constant after this (17-19). Based on Sd+GP values obtained at the initial life of the wells, skin due to gravel seems to be high in F13WSC-1 and –3 (Longer AHD wells), compared to F13WSC-2 (Shortest AHD well) which has relatively low skin. A stimulation job in F13WSC-1 is recommended to improve its productivity and bring the lost intervals back to production Future build-up analysis should be investigated to keep close eye on skin performance.
Back-up
F13WSC-1 F13WSC1_Jun06_BU.ks3 - skin F13WSC1_Nov06.ks3 - skin F13WSC1_Feb07_BU.ks3 - skin F13WSC1_Apr08_BU.ks3 - skin (ref)
1E+7
RF 1E+6
1E+5 1E-5
1E-4
1E-3
0.01
0.1
Compare files: dm(p) and dm(p)' [psi2/cp] vs dt [hr]
1
F13WSC-2 F13WSC2_Jun06_BU.ks3 - Analysis 2 F13WSC2_Nov06.ks3 - Analysis 10 F13WSC2_Feb07_BU.ks3 - Analysis 2 F13WSC2_Apr08_BU.ks3 - Analysis 1 (ref)
1E+7
RF 1E+6
1E+5 1E-4
1E-3
0.01
0.1
Compare files: dm(p) and dm(p)' [psi2/cp] vs dt [hr]
1
F13WSC-3 F13WSC3_Jun06_BU.ks3 - skin F13WSC3_Nov06.ks3 - skin F13WSC3_Feb07_BU.ks3 - skin F13WSC3_Apr08_BU.ks3 - skin (ref)
1E+7
RF 1E+6
1E+5 1E-4
1E-3
0.01
0.1
Compare files: dm(p) and dm(p)' [psi2/cp] vs dt [hr]
Back to Process
1
Geometric Skin Estimation
-Number of zones is given by PP -Sgeo from Fair Plot
Geometric-Skin Factors for Slant Wells 0 -1 -2 -3
Skin
-4 -5 -6 -7 -8 -9
SPE 104480 by P.S. Fair
-10 0.1
1
10
30
1000
10000
hbed/rw
Back to Process 15
100
45
60
75
80
84
86
88
89
89.5
89.9
Non-Darcy Skin Rate-Dependant Skin
Back to Process
Equivalent Skin Due to Pressure Drop to gauge-depth
DPF is estimated from tubing lift curves correlations (Prosper)
Back to Process
