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Determining Optimum Well
Locations & Well Paths
Predicting or delineating fracture sweet
spots with high fracture intensity and/or
good connectedness
Predicting or delineating dominant open
fracture direction to plan deviated well
paths to encounter the best fractures Plan well paths that optimize fracture &
matrix properties
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Mechanical Stratigraphy
Subtle changes in rock character
(petrologic & petrophysical) control rock
deformation. Variations in deformation type and
intensity mimic subtle changes in rock
character.
Nelson (1985)
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Mechanical Predictions
Relative rock strength can be used to
predict fracture intensity.
Stronger rocks generally contain closer
spaced fractures.
Above usually works because most
shallow reservoir rocks are brittle &show little variation in stain at failure.
(fracture toughness)Nelson (1985)
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Composition
Rocks composed of predominately strong
and brittle components are stronger and
generally contain closer spaced fractures
Nelson (1985)
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Sun (2001)
Fracture Intensity as a Function of Rock Type (Mechanical Properties)
Cooper & Wharbaton Basins,
S. Australia
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Strength vs Composition
Dev. Antrim Sh
Michigan BasinStrength increases with
% brittle minerals
Nelson (1985)
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Rock Properties vs Depth, Texaco 17#2
0
2
4
6
8
10
12
14
16
17200 17300 17400 17500 17600 17700 17800 17900 18000 18100
Depth, ft
RockProperty
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Young's Mod. E06psiPoisson's Ratio
Youngs Modulus and Poissons Ratio
Logs for a Well in the Permian Basin
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Porosity
Lower porosity rocks are stronger and
more brittle and generally contain closer
spaced fractures
Nelson (1985)
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Nelson (1985)
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Ward (1987)
Fracture Intensity vs Porosity
Ls, Tectonic Fracures
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All Fracture Intensity vs AH Depth, MOW-4 Core
0
0.5
1
1.5
2
2300
2400
2500
AH Depth, m
A
llFractureIntensity,
#/0.5m
Fracture Intensity Curve
(core based, 89% cemented)
SS Carb
MFI = 0.483 MFI = 1.003
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Fracture Intensity vs Porosity with Depth, MOW-4 Core
0.0
5.0
10.0
15.0
20.025.0
30.0
35.0
76
00
76
50
77
00
77
50
78
00
78
50
79
00
79
50
80
00
80
50
81
00
Measured Depth, ft
WholeCorePor
osity,
%
0
0.2
0.4
0.6
0.81
1.2
1.4
AllFractureInte
nsity,
#/0.5
ftPorosity, %
FIC, #/0.5 ft
Inverse Relationship Between Porosity &
Fracture Intensity
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Grain Size
Finer grained rocks are generally stronger
and more brittle and generally contain
closer spaced fractures
Nelson (1985)
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Strength vs Grain Size, Navajo Ss
Nelson (1985)
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Ward (1987)
Fracture Intensity vs Grain Size
Ls, Carbonates
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Bed Thickness
For bed-contained fractures, closer
spaced fractures in thinner beds
Nelson (1985)
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After Sowers (1970)
Fracture Spacing vs Bed Thickness
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