-
FRACTURE DESIGN VARIABLESTIP EFFECTS
H , E , C , KIc-App m , Q
-
Laboratory Toughness (KIc) Values
0 1000 2000 3000 4000 50000
1000
2000
3000
4000Mesaverde
SS
Berea SS
Indiana LS
Mesaverde
Mudstone
Confining Pressure (psi)
K (p
si
in)
Ic
-
Basic Physics Tip EffectsPTip
)(24)()(
ftHinchpsiKpsiP AppIcTip
20 40 60 80
20
40
60
80
100
120
140
160
180
Ne
t P
res
su
re (
ps
i)
H (ft)
K-Ic = 4000
K-Ic = 2000
K-Ic = 1000
-
Does A Hydraulic FractureEven Form in Unconsolidated Media
Rock & Fracture Mechanics Laboratory
Georgia Tech University
hydraulic fracturing in (unconsolidated)
particulate materials is not only possible,
but even probable if leak-off is minimized
(e.g., high flow rate, high viscosities, )
-
Does A Hydraulic FractureEven Form in Unconsolidated Media
Yes, BUT(Tip mechanisms totally different, but does it
matter?)
Courtesy Leonid Germanovich, Georgia Tech University
-
Apparent Fracture Toughness
Very Low Modulus
Formations
Radial Fracture, No
Height Confinement
Very Low Fluid
Viscosity (water)
Normal Modulus Formation
Treatments Using
Frac Fluid
Some (not
necessarily perfect)
Height Confinement
May Be Important Much Less Important
-
Fracture Design Variables
H (Height or Geometry) = f (PNet/DsSand-Shale)
E (Youngs Modulus, a pure rock property)
C (Fluid Loss)
KIc-App (PTip or Tip Effects)
-
Basic Physics Net Pressure, PNet
4/1
4
2
4
4
'
'
O
Ic
O
NetH
K
E
LQ
H
EP
m
Viscous Tip
-
Basic Physics Net Pressure, PNet
)(),(),(),(),(),('
576'
'015.0)(
4/1
2
42
4
4
inpsiKftLbpmQcpftHpsiE
H
K
E
LQ
H
EpsiP
ICO
O
Ic
O
Net
m
m
Viscous Tip
-
PNet Behavior Confined Height
0.2 0.5 1 2 5 10 20 50 100
20
50
100
200
500
1,000
Pump Time (min)"Time 0" When Gel On Perfs
Net
Pre
ss
ure
(p
si)
Data
Confined H
m Dominated
Confined HTip Dominated
West Africa Frac Pack1+ Darcy Permeability
-
PNet Behavior - Radial
0.2 0.5 1 2 5 10 20 50 100
20
50
100
200
500
1,000
Pump Time (min)"Time 0" When Gel On Perfs
Net
Pre
ssu
re (
psi)
Tip Dominated
m Dominated
Nolte-Smith BehaviorSimulations
4/1
4
2
4
4
'
'
O
Ic
O
Net
H
K
E
LQ
H
E
P
m
-
Basic Physics
4/1
2
4
4
4
'
'
O
Ic
O
NetH
K
E
LQ
H
EP
m
Viscous Tip
HwHSTHC
TQL
PPPP
P
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