proppants objective • to hold the fracture open and provide a highly
TRANSCRIPT
Proppants
Objective
• To hold the fracture open and provide a
highly conductive path for fluid to flow into
the wellbore.
Proppants
Physical properties of proppants
1. proppant strength
2. grain size
3. sphericity
4. quality
5. proppant density
Proppants
Proppant Selection
• Goal to achieve maximum fracture conductivity
Selection based on physical properties of proppants
Proppants
Proppant Selection
1. Higher proppant strength to withstand closure pressure
and avoid crushing or embedment
Response of propping agents to fracture closure pressure
Proppants
Proppants
Types of Proppants
1. Sand, Sp. Gr. = 2.65, – low cost
2. Resin-coated sand, 2.55 – improves
proppant strength
3. Intermediate Strength Proppants (ISP),
2.77-3.3, - fused ceramics
4. High Strength Proppants (Bauxite), >3.4 -
expensive
Proppants
Effect of closure stress on permeability of various propping agents
Proppants
Proppant Selection
1. Higher proppant strength to withstand closure pressure
and avoid crushing or embedment
2. Increase grain size to acquire higher permeability but
transport problems, fines migration, and susceptible to
crushing
Proppants
Effect of proppant size on the permeability of northern white sand
Proppants
Proppant Selection
1. Higher proppant strength to withstand closure pressure
and avoid crushing or embedment
2. Increase grain size to acquire higher permeability but
transport problems, fines migration, and susceptible to
crushing
3. Spherical grains distribute high loads before failure.
4. Impurities reduce conductivity
Proppants
Proppant Selection
Roundness and sphericity
[Pettijohn, et al.,1973]
0.01
0.1
1
0 2 4 6 8 10
Frac
ture
co
nd
uct
ivit
y, D
arcy
-ft
Stress, (1000 psi)
Proppants
Proppant Selection
1. Higher proppant strength to withstand closure pressure
and avoid crushing or embedment
2. Increase grain size to acquire higher permeability but
transport problems, fines migration, and susceptible to
crushing
3. Spherical grains distribute high loads before failure.
4. Impurities reduce conductivity
5. Higher proppant density is more difficult to suspend in the
frac fluid and to transport in the fracture.
settling
suspension Pad Volume
Created
length
Bed growth
Increasing bed
height
Constant
Propped
length
Angle of
repose
Equilibrium bed height
Increase in length
Proppant Transport
•Convection of proppant
while pumping
•Settling of proppant
Proppants
Proppants
Proppant Failure (Screenout)
• Proppant blockage in the fracture due to
premature bridging (wf ~ 3*dprop)
• and/or slurry dehydration
Proppants
Proppant Design
1. Pad Volume,Vp,
2. Ramped Proppant Schedule,
cp(t);
where Vi - injected volume
cf - final proppant concentration, ppg
ti - total injection time, min.
tpad - time to pump pad, min.
η1
η1iVpV
η1
η1
padtit
padttfc(t)pc
time 0
0
Pad
slurry
Slu
rry c
on
cen
trati
on
ti
cf
Proppants
3. Propped length, Lp (equilibrium bank condition)
Where
mp - amount of proppant in lbm
rp - proppant density, lbm/ft3
4. Relation of propped width to proppant concentration
where w is width in inches, Cp is proppant concentration
(lb/ft2), fp is proppant porosity, and rp is density of the
proppant in lb/ft3.
wfhpρ
2pm
12
pL
pp
pC
wrf )1(
12