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Hydrologic Characterization of Fractured Rocks for DFN Models. Useful Definitions and Concepts. Transmissivity -- Properties of a conductor (aquifer, reservoir, single fracture, fracture zone) ( L 2 /T ) Permeability, Hydraulic Conductivity -- Property of material inside conductor ( L/T ). - PowerPoint PPT Presentation
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Hydrologic Characterization of Fractured Rocks for DFN
Models
Useful Definitions and Concepts
• Transmissivity -- Properties of a conductor (aquifer, reservoir, single fracture, fracture zone) (L2/T)
• Permeability, Hydraulic Conductivity -- Property of material inside conductor (L/T)
Definitions, continued
• Storativity -- Storage of a conductor or conducting feature (dimensionless)
• Specific Storage -- Property of material in a conductor (1/L)
• Hydraulic Diffusivity -- Ratio of T/S (L2/T)– Controls speed of propagation of pressure
effect of a disturbance– Very (!!!) important for scaling results
Overview
• Useful Concepts• Steady Flow Methods
– Packer Tests– Flow Logs
• Transient Flow Methods– Boundary effects– Dimension effects
Steady Flow Methods
• Packer Testing– Falling Head Test– Constant Pressure/Lugeon Test
• Flow Logging– Heat pulse– Spinner– Hydrophysical
Steady Radial Flow
• Pressure and flow constant
• Only exists with constant pressure boundary
• Generally under-estimates due to skin
R
rw
hQ
hQrRT w
π2)ln(
Packer Test (Fixed Interval Length)
• Used in Civil Engineering
• Testing at fixed interval lengths
• Some zones have no fractures; some zones have multiple fractures
• Efficient testing has some no flows but not too many
LPP n )ln(
10
Pn - # of no flows/# of tests
L - length of test zone
Oxfilet (Osnes Extraction of Fixed Interval Length Evaluation of Transmissivity)
• Guess T and P10 of Fractures• Oxfiet generated fracture along hole• Oxfilet calculates packer test
transmissivities• Oxfilet compares measured and
simulated pacer test transmissivities
Oxfilet Interface Data and Simulated PDF’s
Data and Simulated CDF’s
Fracture Network Stats
Packer Test Stats
Oxfilet Challenges
• Results non-unique but constrained (range of combinations of distributions of T and frequency that will fit a test
• Flow logging preferred method
Flow Log Types
• Spinner• Heat pulse• Hydrophysical• Induced electromagnetic
Spinner Hydrophysical Log(1) Replace fluid with deionized water
(2) Log fluid resistivity while pumping
UCM (Electromagnetic Log)Well Name: KI0025F02File Name: C:\WELLMAC\WELLDATA\ASPO\TRUE\KI025F02.HDRLocation: ASPO HRL, TRUE Block ScaleElevation: 0 Reference: Ground Surface
Date: 98-09-01UCM Probe:9302
Metres Flow(l/min)0 60
Temp(Deg C)16.2 16.8
Fluid_Res(ohmm)0.75 2
0
-50
-100
-150
-200
Flow
Fluid Resistivity
Temp
FLO W RATE AN D SIN GLE PO IN T R ES IS TAN C E LO GSD E P TH S OF L E AK Y FR A C TU RESÄS P Ö , K I002 5F03
1E +1 1E +2 1E +3 1E +4 1E +5 1E +6
Flo w ra te (m l/h)
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
Dep
th (m
)
1E +1 1E +2 1E +3
S in gle po int resistanc e (o hm)
12 5 .45
12 4 .65
1 33.3
1 31.1
1 28.3
Heat Pulse Log Posiva (Finland) Heat Pulse Flow Log (Äspö)
Thoughts on Flow Logging
• Cumulative logging methods fast and easy
• Discrete interval logging methods provide better detail and wide range of distribution
• Complementary temperature and fluid resistivity can be useful
Image LoggingBorehole TV (BIPS) FMI (micro-resistivity)
Hydro-Testing Work Flow
• Steady tests (flow log) to identify conductors
• Image log or core analysis to geo-logically characterize conductors
• Transient tests to characterize network away from hole
-3.00E+00
-2.00E+00
-1.00E+00
0.00E+00
1.00E+00
2.00E+00
3.00E+00
4.00E+00
-2.00E+00 -1.00E+00 0.00E+00 1.00E+00 2.00E+00 3.00E+00 4.00E+00 5.00E+00 6.00E+00 7.00E+00
Dimensioness Time
Dim
ensi
onle
ss P
ress
ure
3
1
2
Transient Well Tests
Overview of Transient Tests
• Important source (most important?) of geometric information on fracture plumbing system
• Cylindrical flow and beyond• Dimensions, boundaries, and reading
derivative curves
Radial Diffusion Equation(Radial Cylindrical Flow)
1 1r r
r hr
ht
Exponential Integral:
p r t qT
ex
dx qT
rt
x
r t
( , )/( )
4 4 42 4
2
Ei -
Semilog Approximation of the Exponential Integral
Ei( u u uu u u
) . ln! ! !
........057722 2 3 3 4 4
2 3 4
p r t qT
tr
( , ) . log .2 3026
42 246
2
(MKS units)
PressureDerivative: constantdpd t(log )
Exponential Integral Function
0
2
4
6
8
10
12
14
-2.00 -1.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00
log tD
pD
0
0
1
10
100
-2.00 -1.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00
log tD
log pD
Semilog Log-Log
Derivative Methods
• Plots P/log(t)• Intent to make semi-line unambiguous• Effect is a very powerful tool to interpret
geometry from tests• Derivative is a map of transmissivity versus
distance from the well• Shape of derivative constrains network
geometry
Exponential Integral and Derivative
0.01
0.1
1
10
100
0 5 10 15 20 25 30 35
log tD
log
pD
Calculating Pressure Derivative in Spreadsheets
A B CTime Head or Pressure Change Derivative
5 2.33E-02 6.15E+016 2.47E-02 6.37E+01 3.68E+017 3.16E-02 7.38E+01 4.47E+018 3.98E-02 8.52E+01 5.27E+019 4.67E-02 9.39E+01 5.72E+01
10 5.08E-02 9.86E+01 5.78E+0111 6.32E-02 1.13E+02 6.89E+0112 7.96E-02 1.30E+02 7.95E+0113 9.46E-02 1.44E+02 8.69E+0114 9.73E-02 1.46E+02 8.23E+0115 1.03E-01 1.51E+02 154.4430288
Formula in Cell C8: t p/ t, or approximately =a8*(b9-b7)/(a9-a7)
If the derivative is noisy, calculate derivative over a larger spread, for example, at C7 calculate using rows 10 and 4
Note: Averaging deteriorates at beginning and end of data especially if a larger is used
Dimensionless Variables(Radial Cylindrical Flow)
Dimensionless Time:
Dimensionless Pressure:
tu
tr
p Tq
p
D
D
1 4
2
2
Useful DefinitionsT kh L FT
T K h L T
S c h L T M
T S L T
FT L
c L F
S S h LT MK k
t
t
s
transmissibility = (
transmissivity =
storativity = (
diffusivity (
viscosity (porosity (-)
compressibility
specific storage = ( conductivity = g
/ / )
( / )
/ )
/ / )
/ )
( / )
/ / )/
* *
5
2
2 2
2
2
2
2
Generalized Radial Flow
p r tqr
Khv u
n
n
n n( , ) ( , )
/
/
2
2 341 2
Dimension Information from Well Tests
-3.00E+00
-2.00E+00
-1.00E+00
0.00E+00
1.00E+00
2.00E+00
3.00E+00
4.00E+00
-2.00E+00 -1.00E+00 0.00E+00 1.00E+00 2.00E+00 3.00E+00 4.00E+00 5.00E+00 6.00E+00 7.00E+00
Dimensioness Time
Dim
ensi
onle
ss P
ress
ure
3
1
2
Integer Flow Dimensions
Linear Flow:
erfc u
Cylindrical Flow
Ei
Spherical Flow
erfc
p r tqr
Khe
u
p r tqKh
u
p r tqKr
u
u
( , )
( , )
( , )
2
4
4
2
Linear (1-D), x-section area r0
Cylindrical (2-D)
x-section area r1
Spherical (3-D)
x-section area r2
Generalized Flow, x-section area rn-1
Log Slope and Dimension
Log Slope = = - /< <
Log Slope = = all
1 21 2
1 2
nn
nn
/For
For Log Plots of Pressure or Inverse Flow Verus Time
For Log Plots of Pressure or Inverse Flow Derivative
Boundary and Dimension Effects
1-D1-D 2-D2-D
3-D3-D
Reservoir geometryReservoir geometry Network/Flow geometryNetwork/Flow geometry
Fracture Intensity (Fracture Area/Rock Mass Volume) Can Influence Dimension
0.1
1
10
100
0.1 1.0 10.0 100.0 1000.0
Time, seconds
Hea
d, m
eter
s
0.175
0.5
.06
0.1
0.25
0.1
Boundary Effect
Geometric Information From Well Tests
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
-2 -1 0 1 2 3 4 5 6 7
Log Time (s)
Log
Dra
wdo
wn
(m)
High Intensity, Large Fractures = High Dimension, Good Boundary Connections
Near Field DomainDomainBoundaries
Lower Intensity, Smaller Fractures = Low Dimension, Compartments
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08
Dimensionless Time
Dim
ensi
onle
ss P
ress
ure
Linear Flow
Composite Boundary
Spherical Flow
Composite Dimension
Comments on Interference Tests
• Radius of Investigation (very handy !!!)• Estimate diffusivity from response time• Independent of dimension
tr 2
Important Notes on Tests
• Transmissivity can be determined only from pumping wells in fractured or heterogeneous rock without assuming uniform flow over region of influence
• Storativity (diffusivity) can only be obtained from observation responses
• Observation wells give geometric information for areas farther from pumping source than themselves
Composite Dimension
• Dimesional Variation Reflect Local Scale versus Larger Scale Effects
• May Reflect Borehole Geometry as Well as Conductive Geometry
Parts of Composite Dimension Curves
• Early Time Effects (Wellbore Storage, Finite Borehole)
• Inner Shell (n1)• Transition (changes in area, property)• Outer Shell (n2)• Boundary Effects
Composite Interference Response
• Response depends on relative distances of transition radius and observation well radius
• Inner zone not observed for observation points near or beyond the transition radius
Rd=1, n1=1.5, n2=2.5
1E-1
1E+0
1E+1
1E+2
1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08
Dimensionless Time
Dim
ensi
onle
ss P
ress
ure
Rd=85, RD1=100, n1=1.5, n2=2.5
1E-1
1E+0
1E+1
1E+2
1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07
Dimensionless Time
Dim
ensi
onle
ss P
ress
ure