4d semilog analysis for oil wells-1
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8/3/2019 4d Semilog Analysis for Oil Wells-1
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Semilog AnalysisFor Oil Wells
8/3/2019 4d Semilog Analysis for Oil Wells-1
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Semilog Analysis
Instructional Objectives
1. Analyze constant-rate drawdown
2. Analyze buildup
8/3/2019 4d Semilog Analysis for Oil Wells-1
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Ei-Function Solution
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Reservoir Pressure Profile
500
1000
1500
2000
1 10 100 1000 10000
Distance from center of wellbore, ft
P r e s s u r e , p s
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s = -2
s = 0
8/3/2019 4d Semilog Analysis for Oil Wells-1
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Incorporating Skin into the
Ei-Function Solution
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Log Approximation to the
Ei-Function
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Estimating Permeability and Skin
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Drawdown Test Graph
700
800
900
1000
1100
1200
0.1 1 10 100 1000
Elapsed Test Time, hrs
P r e s s u r e , p s i
(t2, pwf2)
(t1, pwf1)
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Exercise 1
Determining permeability and skin factor
from a constant-rate flow test
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Exercise 1
3300
3350
3400
3450
3500
3550
3600
1 10 100
Time, hrs
P r e s s u r e , p s i
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Problems with Drawdown Tests
It is difficult to produce a well at a
strictly constant rate
Even small variations in rate distort thepressure response
There is one rate that is easy to maintain
± A flow rate of zero. A buildup test is conducted by shutting
in a producing well and measuring the
resulting pressure response.
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Buildup Test - Rate History
(t0
- q
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tp (t0
q
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Buildup Test - Pressure Response
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Buildup Test - Superposition
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Pressure Response for a
Buildup Test
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Buildup Test
Straight Line Analogy
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Buildup Test Graph
1400
1500
1600
1700
1800
1900
2000
110100100010000
Horner time ratio
P r e s s u r e , p s i
pi
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Estimating Skin Factor From A
Buildup Test
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Horner Pseudoproducing Time
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Exercise 2
Determining permeability and reservoir
pressure from buildup tests