1. Well test analysis research at Imperial College http://www.jipimperial.co.uk
Alain C. Gringarten
Professor of Petroleum Engineering
Director of the Centre for Petroleum Studies

2. Prerequisite: actual well test data
Objectives
explain complex well test behaviours
provide practical methods for interpreting them
assess uncertainties and limitations of the corresponding analysis results as a function of the information available
Prerequisite: actual well test data

3. JIP: Investigation of Alternative Methods for Testing Oil and Gas Wells to Eliminate Emissions
: BP, Conoco, Norsk Hydro and Schlumberger
Objective: evaluate options for testing exploration and appraisal wells without producing fluids to the surface
closed-chamber testing
harmonic testing
re-injection in a different layer
Outcome: Deconvolution
3 SPE publications, 3 MSc theses, 1 PhD thesis

4. 22 SPE publications, 55 MSc theses, 10 PhD theses
JIP: Well test analysis in gas condensate and volatile oil reservoirs below saturation pressure
: Anadarko, Burlington, BHP Billinton, Britannia Operator Ltd, ConocoPhillips, GdF, RERI, Total and UK DTI
: BG Group, Burlington, ConocoPhillips, ENI, Petro SA, Petrom and Total
Objectives: explain well test behaviours below saturation pressure
22 SPE publications, 55 MSc theses, 10 PhD theses

5. Well test analysis in gas condensate and volatile oil reservoirs below saturation pressure
Outcome:
2-phase bank develops below saturation pressure
Well productivity evaluation requires capillary number effect
2 or 3-region composite well test behaviour with 1-phase pseudo-pressures for gas condensates or pressures for volatile oil
Homogeneous behaviour with 2-phase pseudo pressure
In sandstone reservoirs, reservoir effective k = arithmetic average core k
Correct 2-phase bank total compressibility is required to estimate the bank outer radius
Fracturing vertical wells or drilling horizontal wells is equally effective for improving productivity
skin vs. rate is the same above and below saturation pressure with 2-phase pseudo pressures below saturation pressure.

6. CDFi (pdew= 3040 psia) Wellbore skin effect Gas rate, MMscf/D 12 10 86 4 2 Q
Above pdew
Below pdew
2-j m(p)
FP18
FP20
FP36
FP30
1-j m(p)
S = -0.9 Q
FP36
Wellbore skin effect
FP30
FP18
FP20
S = 0.3 Q
FP13
S = 0.3 Q
FP3
FP5
Gas rate, MMscf/D

7. JIP: Well Test Analysis in Complex Systems
Complex Fluids, Complex reservoirs, and Complex Wells
: BG Group, BHP Billiton, Eon-Rurhgas, Petro SA and Schlumberger
Gas condensate and volatile oil below saturation pressure
Shale gas:
Molecular Modelling
Macro-scale experimental studies
Darcy scale modelling
Well test analysis
Geologically complex reservoir geometries
Semi-infinite channels with non-parallel boundaries
Meandering channels
Pinch-out boundaries
9 SPE publications, 26 MSc theses

8. Well Test Analysis in Complex Systems
Complex Fluids, Complex reservoirs, and Complex Wells
Shale gas outcome:
Stable storage of methane is impossible in the kerogen itself
High CH4 molecule concentrations are trapped by K+ ions on illite faces in kerogen-illite or illite-illite interfaces with apertures h lower than or equal to 8 Å
Two partial storage sites exist in larger interfaces h ≥ 10 Å, due to irreversible anti-adhesion processes
The density of the stored gas in illite-illite interfaces is very high compared to pressured free gas (up to several thousands of CH4 moles per cubic meter of interface).
The total gas-in-place can be evaluated by measuring the distribution and size of mineral interfaces.
The amount and rate of gas that can be extracted depends on the ability of enlarging clay mineral interfaces at depth (for instance by hydraulic fracturing).

9. INTERSECTING BOUNDARIES
105
104
103
102 10
80o
31o
Wedge 2
d1 = 32 m
d2 = 30 m
a = 31o
Wedge 1
d1 = 13 m
d2 = 27 m
a = 80o
nm(p) Change and Derivative (kPa)
Elapsed time (hrs)

10. nm(p) Change and Derivative (kPa)
MEANDERING CHANNEL
Elapsed time (hrs)
nm(p) Change and Derivative (kPa)
104
103
102 10 1
80o
Channel
d1 + d2 = 15 m
Wedge
d1 = 7 m
d2 = 4 m
a = 84o

11. 11 SPE publications, 19 MSc theses
JIP: Deconvolution
: BG Group, BHP Billiton, BP, Chevron, ConocoPhillips, ENI, GdF, Occidental, Petro SA, Saudi Aramco, Schlumberger, Shell, Total and Weatherford
: Anadarko, BG Group, Chevron, ConocoPhillips, Inpex, Petro SA, Saudi Aramco, Schlumberger, Shell, and Total
Objectives: assess the uncertainty in the well test interpretation model through deconvolution
extend deconvolution to multiple interfering wells
Outcome: Monte-Carlo Deconvolution
11 SPE publications, 19 MSc theses

12. Deconvolution
3800
4000
4200
4400
4600
4800
5000
5200
5400
-10 10 20 30 40 50 60 70 80 90
100
110
120
130
Pressure (psia)
Elapsed time (hrs)
-20
140
Gas Rate (MMscf/D)
3800
4000
4200
4400
4600
4800
5000
5200
5400
-10 10 20 30 40 50 60 70 80 90
100
110
120
130
Pressure (psia)
Elapsed time (hrs)
-20
140
Gas Rate (MMscf/D) 12

13. Deconvolution: boundary identification
Test 1 (Exploration)
FP06
Test 2 (Production)
FP35
Maureen A2 13

14. Deconvolution: boundary identification
100
FP 06 (Exploration build-up)
FP 35 (Production build-up) 10 1
Test duration
0.1
Derivative, psia
0.01
Maximum flow
period durations
0.001
Build-ups during exploration and production tests in Maureen well A2. Boundaries are not visible, whereas there are in the deconvolved derivative of the production test build-up. The deconvolved derivative confirms the analysis model.
0.0001
0.0001
0.001
0.01
0.1 1 10
100
1000
10000
100000
1E+06
1E+07
1E+08
Time, hrs 14

15. Deconvolution: boundary identification
100
Dimensionless unit rate pressure & derivative type curves
FP 06 (Exploration build-up)
FP 35 (Production build-up) 10
lambda = 1.e+05
lambda = 5e+05
lambda = 8e+05
lambda = 1.0e+06
Deconvolved derivative
for various smoothness values 1
Test duration
0.1
Derivative, psia
0.01
Maximum flow
period durations
0.001
Build-ups during exploration and production tests in Maureen well A2. Boundaries are not visible, whereas there are in the deconvolved derivative of the production test build-up. The deconvolved derivative confirms the analysis model.
0.0001
Knowledge gap
0.0001
0.001
0.01
0.1 1 10
100
1000
10000
100000
1E+06
1E+07
1E+08
Time, hrs 15

16. Monte Carlo deconvolution

17. The Atlantic Refining Co…)
JIP: New developments in well test analysis
SPE papers with WT 50
100
150
200
250
300
350
Year
1947
1949
1951
1953
1955
1957
1959
1961
1963
1965
1967
1969
1971
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
2007
2009
Number of publications
Horizontal
wells
Electronic
gauges
Permanent
Hardware/Completion
MHF
IKVF
Stehfest
Green’s
functions
Deconvolution
Laplace
transform
Mathematical tools
Horner
Derivatives
Methodology
Type
Curve
Analysis
MDH
MBH
Commercial
Software
Interpretation methods
IOC
Shell, Gulf Oil Corp,
The Atlantic Refining Co…)
UNIVERSITIES
Texas A&M, Stanford
SERVICE
Flopetrol
Schlumberger
NICHES
???????
DEVELOPERS

18. Value tied to power in Identification and Verification
New developments in well test analysis
Value tied to power in Identification and Verification
Poor
None
ANALYSIS METHOD IDENTIFICATION VERIFICATION
50’s
Straight lines
Fair ( limited)
Fair to Good
70’s
Pressure Type Curves
Very Good
80’s
Pressure Derivative
Much better
00’s
Deconvolution
Same as derivative
Next ?
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19. New developments in well test analysis
Multiwell deconvolution
Shale oil and gas
Molecular Modelling
Macro-scale experimental studies
Darcy scale modelling
Well test analysis

20. New developments in well test analysis
Multiwell deconvolution

21. New developments in well test analysis
Shale oil and gas

22. New developments in well test analysis
Shale oil and gas

23. New developments in well test analysis
Shale oil and gas
Fracture
Matrix