SPE 119242 How to Use and Misuse Proppant Crush Tests – E i th ...

SPE 119242
How to Use and Misuse
Proppant Crush Tests –
EExposing i the th Top T 10 Myths M th
John Kullman, CARBO Ceramics
T. T. Palisch, M. Chapman, R. Duenckel, and S.
Woolfolk Woolfolk, CARBO Ceramics Ceramics, Inc Inc.
M. C. Vincent, Insight Consulting

Outline
• Introduction/Motivation
• Crush Test Procedure
• MMyths ths
–Misuse/misapplication pp
• Summary

The Big Picture
• Fracs must provide:
– Reservoir contact (length, height) to contact and
collect oil and gas
• Related to volume of proppant
– Flow capacity to carry oil and gas to the wellbore
• Related to proppant permeability and frac width –
described as conductivity
• Other Important Proppant Characteristics
– Durability
– Temperature Resistance
– Transportability
– Fluid Compatibility
– Flowback Control
– Environmentally Benign

• GGas Well W ll
– 7500 psi stress
Question…
– You can successfully place a 16/20 or 16/30
sized proppant
• Two choices of proppant
– Proppant A – 16/20 Ceramic, 14% Crush (7.5k)
– Proppant B – 16/30 Ceramic, 7.5% Crush (7.5k)
– Which proppant would you choose?
– What if I told you y that they y had the same MPD?
– What would you be willing to pay for your choice?

Introduction/Motivation
• API RP56 & 60 original – updated in ISO
13503-2 (2006)
– “improve quality…delivered proppants”
– “enable…to compare physical properties”
– OOriginal i i l iintent t t tto help h l qualify lif sand d sources
• “Crush results” and proppant selection
– “ “qualified lifi d engineering i i analysis….required l i i d ffor
their application to a specific situation”
– SPE 11634 – Conductivity comparisons cannot
be made on the basis of crush tests
**Yet Yet many still choose their proppants based on
crush results **

ISO 13503-2 Crush Test Procedure
• PProppant t is i pre-sieved i d tto
remove particles outside of
stated mesh range.
• DDry proppant t placed l d iin steel t l
cell at ~4 lb/sq ft (sand
equivalent)
• Room temperature
• Proppant evenly distributed
with level surface
• LLoad d applied li d at t uniform if rate t
• Constant stress maintained for
two minutes
• Proppant is sieved. The weight percent which falls
below the primary screen is reported.
– For 16/20 proppant all material < 20 mesh is reported as “fines” fines
– For 30/50 proppant all material < 50 mesh is reported as “fines”

ISO 13503-2 Crush Test Procedure
Do these reflect realistic conditions?
• Proppant is pre-sieved.
• Proppant Loading – sand/RCS/LWC ~4 lb/ft2 ,
IDC 4.8 lb/ft2 , Bauxite ~5.2 lb/ft2 • Smooth, steel plates – embedment?
• “Carefully y loaded”
• Dry, room temperature
• 2000 psi/min, psi/min relaxed after 2 minutes
• Only the particles smaller than bottom screen
are considered “fines” fines or “crush” crush

Are the results repeatable/reliable?
Crush Cell Loading critical
• “variance in crush results….associated with
method of loading…”
• Significant efforts ongoing on ISO Committee
and StimLab to alleviate variations in results
– Loading technique thought to be the cause
– Lab to lab, technician to technician, equipment to
equipment

Perrcent
Crushh
26
24
22
20
18
16
14
12
10
8
6
4
2
0
9.118
10.663
10.995
Are the results repeatable?
16/30 Brown Sand Hand Loaded Weight Percent Crush at 4000psi
25.221
23.660
24.229
16.770
14.660
16.770
24.552
14.771
17.886
15.774
17.552
18.445
9.220
9.880
10.110
23.226
23.229
24.775
6.004
5.992
6.442
14.8% Avg
8.440
8.990
8.660
Test#1
Test#2
Test#3
17.778
19.888
18.443
9.110
9.550
9.110
1 2 3 4 5 6 7 8 9 10 11
Lab Number ISO Subcommittee Results

Perrcent
Crushh
18
16
14
12
10
8
6
4
2
0
9. .79
9. .40
9. .26
Are the results repeatable?
16/30 Brown Sand Mechanical Loaded Weight Percent Crush at
4000psi
Test#1
8. .96
16. .66
11. .41
12. .00
12. .00
12. .80
10. .32
10. .89
10. .79
10.
9.
9.
.53
.07
.85
7. .80
8. .40
7. .76
10. .49
10. .22
9. .94
10.0% Avg
No data
reported
8. .40
8. .20
8. .40
7. .50
7. .50
9. .23
Test#2
Test#3
10. .10
10. .80
10. .60
1 2 3 4 5 6 7 8 9 10 11
Lab Number ISO Subcommittee Results

Does Fracture Width Affect Crush?
• Interior grains loaded “evenly”
• Exterior grains g have fewer
load points
• Crush increases significantly
as proppant loading
decreases
• For a 20/40 proppant, there are approximately
24 layers of proppant in standard crush test. test
– 8% are exterior grains
1 lb/ft2 • 1 lb/ft i 6 l f 20/40 t
2 is ~6 layers of 20/40 proppant
– 33% are exterior grains

Crush Depends p Upon p Frac Width!
Crush
Percent
30
25
20
15
10
5
0 4 lb/sq ft 2 lb/sq ft 1 lb/sq ft 0.5 lb/sq ft 0.25 lb/sq ft
Monolayer
~ 0.2 lb/sq ft

% Crush
100%
90%
80%
70%
60%
50%
Crush vs # Layers
Crush at 10,000 psi
20/40 Proppants
40%
1lb/ft 2
1 lb/ft 2
40% B it 1 lb/ft 2
Bauxite
ELWC
30%
20%
10%
0%
1 lb/ft 2
Sand &
RCS
White Sand
ELWC
RCS
BBauxite it Ceramic C i
0 1 2 3 4 5 6 7 8 9 10
# of Layers

% Crushh
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Crush vs # Layers
Crush at 1000 psi
All 20/40 Proppants
1 lb/ft 2
Bauxite
1 lb/ft 2
ELWC
White Sand
RCS
ELWC
Bauxite Ceramic
1 lb/ft 2
Sand &
RCS
0 1 2 3 4 5 6 7
# of Layers
Partial
Monolayer

RANGE OF FRACTURE COMPLEXITY
SPE 77441
Simple p Fracture Complex p Fracture
Very Complex Fracture Network
Complex fracs are
believed to provide less
cumulative conductivity
than simple, simple wider
fractures

16
Vertical Complexity
DDue TTo Joints J i t
Physical evidence of
fractures nearly
always complex
NEVADA TEST SITE
HYDRAULIC FRACTURE
MINEBACK

Uniform Packing
Is this ribbon laterally y
extensive and
continuous for
hundreds or
thousands of feet?
17
Arrangement?
Pinch out, proppant
pillars, ill iirregular l
distribution?

Are Large Particles weaker than Small?
Pounds P of Force F to CPF cru ush one pell let
80.00
70.00
60.00
50.00
40.00
30.00
20 20.00 00
10.00
Si y = l 1488 1488.2x P 2 2ll - 18 18.714 t C 714 h
R 2 y = 1488.2x - 18.714
R = 0.7765
2 y = 1488.2x - 18.714
R = 0.7765
2 Single Pellet Crush
= 0.7765
18
16
20/40
16/20
12/18
0.00
14
0.0000 0.0100
12
0.0200 0.0300 0.0400 0.0500 0.0600
Proppant Size inches Courtesy Stim-Lab
Percent
Crush
10
8
6
4
2
0
NO!!
30/50 LWC 20/40 LWC 16/20 LWC 12/18 LWC

For all proppant types, larger grains have
greater individual strength strength.
CPF
160
140
120
100
80
60
40
20
0
20/40
12/18
0 0.02 0.04 0.06 0.08 0.1 0.12
Proppant pp Size, , inches
Source: Stim-Lab Consortium, July 2001 1.8-16
CarboLite
Hi Hickory k
Interprop
CoSilica
Jordan
ResinPR

Another Look at Single Grain Strengths…
CPF
160
140
120
100
80
60
40
20
0
20/40
12/18
0 0.02 0.04 0.06 0.08 0.1 0.12
Proppant pp Size, , inches
Source: Stim-Lab Consortium, July 2001 1.8-16
CarboLite
Hi Hickory k
Interprop
CoSilica
Jordan
ResinPR
Note that application of
resin does not improve p
grain strength, but rather
improves distribution of
stress between grains
and encapsulates fines.

So why does crush increase
• Strength in numbers?
with ith llarge proppants? t ?

“There’s Strength in Numbers”
Smaller mesh sizes distribute the load to across
more particles compared to larger mesh sizes

Proppant Type
• Natural quartz crystals (sand), manufactured ceramics, and
resin-coated proppants crush differently
• Sand
– QQuartz t crystals t l tend t dt to result lti in a greater t number b of ffi fine shards h d
• Ceramics
– Tend to cleave or part p into relatively y few, , larger g ppieces
• Resin Coated Products
– Resin does not significantly change single grain strength, but
improves distribution of stress stress. If the particles can be
encapsulated, they will not be measured as “crush” regardless of
whether the substrate fails
SPE 11634 - conductivity comparisons cannot be made on the basis of
crush tests.

Do all Proppants Fail in the Same Manner?
Brown Sand
at t6k 6k psi. i
RCS at 8k psi.
When they fail fail…
– Sands shatter like a glass
– CCeramics i cleave l lik like a bbrick i k
– Resin Coated products
“deform”; deform ; fines captured
IDC at
8k psi.

Do fines affect all proppants similarly?
RRemember… b
• All proppants do not fail in the same manner
– The fines generated by one proppant may look
drastically different than those generated by
another. th
• The packing arrangement for similarly sized
proppants are not the same for all types of
proppants.
– i.e. the packing arrangement for a 20/40
ceramic, 20/40 RCS and 20/40 Sand will be
diff different t even at t comparable bl stresses.
t

ht Perceent
in Siize
Rangge
Weig
Post Crush Sieve Distribution
100
75
50
25
0
98
After crushing 20/40
EconoProp at 6000 psi
Standard API technique
1.18 0.43 0.2 0.13 0.08 0
-20/+40 -40/+50 -50/+70 -70/+100 -100/+200 -200/+325 Pan
Source: CARBO Analyses Nov 1998

A Closer Look at the Crushed Fraction
Percent P Crush C
1.20
1.00
0.80
0.60
0.40
0.20
0.00
1.18
“2% fines” reported with standard
testing could mean 2 cleaved grains
per 100 (4 immobile pieces), or it could
represent 400 mobile fragments in the
100-mesh range
Immobile cleaved grains It makes a difference!
0.43
0.2
Potentially mobile in 20/40 pack
(SPE 24008)
0.13
0.08
-40/+50 -50/+70 -70/+100 -100/+200 -200/+325 Pan
Source: CARBO Analyses Nov 1998
0

Fluid Effects
• Crush testing is performed dry. What if the proppant
is saturated?
Percentt
Crush
7
6
5
4
3
2
1
0
Modified Crush Test Results
EEconoProp P at t 6000 psi i
Dry API Moisten in cell
Moistenincell Moisten in cell Moisten with
Moisten with
with water with min. oil water, then min. oil, then
add to cell add to cell
Source: CARBO Tech Brochure 3/4/96

Is one set of Test Conditions superior to another?
Cruush
%
35
30
25
20
15
10
5
0
Standard
Loadingg
Dry, y, wet, , hot, , room temperature, p , water or oil…
is one method more realistic than another?
Load by
hand and
rotate
piston
Load by
hand and
do not
rotate
piston
6k Crush @ 2#/ft2
Sand
ELWC
RCS
Standard Standard Standard Wet with Wet with Standard Standard
then tapp
then wet then wet water then mineral oil but heat to but heat to
cell with water with load into then load 200F dry 200F wet
mineral oil cell into cell

Can Crush results be Correlated to Conductivity?
More Realistic Conditions in a Conductivity Test
What’s the Difference?
• Proppants pp evaluated as received
• Tests equivalent mass loading, and 2 lb/ft2
• Utilizes Sandstone shims
• Flow water through pack
• Elevated temperatures (150° (150 or 250° 250 F)
• Stress held for at least 50 hours

Disassembled API Proppant Cell
Proppant Bed
Ports for Measuring
Differential Pressure
Temperature Port
Sandstone Cores
Flow Through
Proppant Bed

Long Term Conductivity Cells

Can Crush results be Correlated to Conductivity?
Crush C %
45
40
35
30
25
20
15
10
5
0
Standard
Loading
The “crush” measured after a Conductivity test
significantly higher than Crush test.
6k Crush Results vs Crush after Conductivity Testing at 6k psi
Load by
hand and
rotate
piston
Load by
hand and
do not
rotate
piston
Standard Standard Standard
then tap then wet then wet
cell with water with
mineral oil
Wet with Wet with
water then mineral oil
load into then load
cell into cell
Sand
ELWC
RCS
Standard Standard
but heat to but heat to
200F dry 200F wet
All tests at 2 lb/ft 2 loading

Embedment
More width retained,
but lower perm

Spalling

Spalling

Example of Conductivity Loss
100000
10000
1000
100
10
CONDUCTIVITY VS. CLOSURE STRESS
Stim -Lab Inc.
P redkF02
`
YME=5E6psi
YME=1E6psi
YME=.5E6psi
YME=.1E6psi
0 2000 4000 6000 8000 10000 12000
CLOSURE STRESS - PSI
11.0lb/sqft 0lb/ ft 20/40B 20/40Badger150°F d 150°F 11.0lb/sqft 0lb/ ft 20/40B 20/40Badger150°F
d 150°F
1.0lb/sqft 20/40Badger150°F 1.0lb/sqft 20/40Badger150°F
Source: Stim-Lab Consortium, Feb 2002 1.6-46

In the real world:
Proppant Durability
- Fractures are subjected to high stresses
(increasing) for extended periods of time
- Stress levels fluctuate (cyclic stress) with
wellwork ll k and d changes h iin li line pressure
Therefore:
• All proppants appear to lose conductivity over
ti time
• Traditional resins do not appear to protect
proppants p oppa s from o deg degradation. ada o
• Many data suggest degradation is a mechanical
failure, not chemical attack. 38

Proppant Durability
• Traditional “long term” conductivity tests maintain
stress on proppant for 50 hours
– It is known that proppants continue to degrade beyond
50 hours, but this was a practical compromise between
laboratory expense and accuracy accuracy. Fig 4, 4 SPE 16415
Longer test captures a portion of
the time-dependent decline. We
know degradation continues
beyond y this, , but modern “50 hour”
tests include correction for initial
repacking/etc.
This phenomenon occurs even
with silica saturation
Reference: SPE 16415 Norton and Stim-Lab
Conducctivity
(mdd-ft)
1000
100
20/40 Jordan sand,
8000 psi
0 25 50 75 100
Hours at Constant Stress

% Original O Conductiv
C vity
Extended duration tests:
1984
(75 & 250F)
API “short term” cell: Metal plates, continuous flowing 2% KCl,
Non Non-silica silica saturated
100
80
60
40
20
0
Fig 19, SPE 12616 between metal plates
20/40 Sand at 75F
10/20 Sand at 250F
0 30 60 90 120 150 180 210 240 270 300
Days at Constant Stress, 5000 psi
Reference: SPE 12616 by Montgomery, Steanson, Schlumberger
40

Permmeability
Ratio R
Published extended duration tests:
1986
93C (200F)
All non-corrodible surfaces, prop in
Teflon tube, continuous flowing 2% KCl
1
0.8
0.6
0.4
0.2
0
Fig 4, SPE 14133
CarboPROP at 10,000 psi (69 MPa)
CarboLITE at 10,000 psi (69 MPa)
Sand at 5000 psi (35 MPa)
0 15 30 45 60 75
Days at Constant Stress
Connductivity
(mmd-ft)
1986
(300F)
Teflon tube, continuous flowing 2% KCl,
Non-silica saturated
10000
1000
100
SPE Drilling, April 1986, page 5
Interprop
Proflow
RCS
Ottawa Sand
0 10 20 30 40 50
Days at Constant Stress, 8500 psi
References: SPE 14133 by CARBO, SPE Drilling article by Norton-Alcoa Proppants and TerraTek Research
41

Temperature Correction for White Sand
Connductivity
Correction C from f 150 deeg
F, factorr
1
0.8
0.6
0.4
0.2
0
150 deg F
200 degF
250 deg F
300 deg F
350 deg F
At 6500 psi and 250F, 20/40 White Sand loses
40% of f it its conductivity d ti it compared d to t 150F. 150F
20/40 Premium White Sand
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Stress, psi StimLab PredictK

Cyclic Loading of Proppant Packs
• All proppants appear to be damaged by
continued stress cycling
Connductivity
(mmd-ft)
5,000
4,000
3,000
2,000
1,000
-
Effect of Stress Cycling on Proppants
Three cycles, 6000 to 1000 psi
CARBO Tech Rpt 99-062
50 hrs at 6000 psi
3 cycles, 6000 to 1000
23% loss
32% loss
Source: CARBO Tech Rpt 99-062
15% loss
RCS #1 RCS #2 EconoProp
Proppant Type (all 20/40)

Condductivity
(md-ft) (
10,000
9,000
88,000 000
7,000
66,000 000
5,000
4,000
3,000
2,000
1,000
-
Effect of Stress Cycling on Proppant Conductivity
(Stim-Lab July 2000 data)
St Stress (psi) ( i)
LWC
RCS
Ceramic loses 26%, 26%
RCS loses 35% due to 25 cycles
0 100 200 300 400
Hours

Perccent
Crrush
(wt% ( smmaller
than t 400
mesh)
30
25
20
15
10
5
CARBO Tech Rpt 99-062
-
Effect of Stress Cycling
on Proppant Crush (6000 psi)
1.37 1.52
10.44
Single Crush at 6000 psi
Triple Cycle Dry Crush
Triple Cycle Crush in Long Term Cell
3333.83 3.33
15.79
302 3.02
1.92
8.47
RCS #1 RCS #2 EconoProp
Proppant Type (all 20/40)

Options to reduce crush:
Action Crush Conductivity
Rename 16/20 to 16/30
⇓ ~50% No change
Add 30 mesh material to 16/20 and rename to 16/30
⇓ ~60% ⇓ ~30%
Reduce average proppant size or produce broader distribution
⇓ ⇓
Sticky additive to agglomerate fines
⇓ ~100% ⇓
Pre-cured or curable resins
⇓ often ⇓ at low stress,
⇑ at high g stress
Include deformable “cushioning” agents
⇓ ⇓

The Correct Way to Test Proppant
• Remember, proppant must achieve two goals:
– Reservoir contact (proppant (p pp volume) )
– Ability to conduct hydrocarbons with minimal pressure loss
• These characteristics can be directly measured with
a conductivity test
– Proppant confined between sandstone core
– Realistic temperatures
– Flowing brine, oil, and/or gas
– 50 hour duration (or longer)
– Cyclic stress, embedment, fines migration, non-Darcy and
other issues can be investigated g in specialized p tests
– Directly measures parameters of interest [frac width and
flow capacity]

SPE 119242
How to Use and Misuse
Proppant Crush Tests –
Exposing the Top 10 Myths
Questions?

Darcy’s Darcy s Law vs vs. Forchheimer Equation
• Δ P/L = μ v /k / k
– Pressure drop is proportional to fluid
velocity l it
– Applicable only at low flowrates
• Δ P/L = μ v / k + β ρv 2
– Pressure drop is proportional to square of
fluid velocity
– Applicable at realistic fracture flowrates

DDoes FFracture t Width Affect Aff t Crush? C h?
• Crush increases significantly in narrow
fractures
Interior grains are loaded
“evenly” evenly on 6 sides
Exterior grains are not
stressed uniformly

Long g Term Conductivity y Test
Procedure
• Load 63 g (equivalent to 2 lbs/sq ft) of proppant in
each cell.
• Install cells in the press.
• Purge 2% KCl solution with oxygen-free nitrogen.
• Apply a vacuum for 45 minutes to remove air in
cells.
• Flow 2% KCl solution through heated silica sand,
and d cells. ll
• Ramp to an initial stress of 1000 psi and to a 500
psi fluid pressure.
• After checking equipment is working properly, heat
cells to 250ºF.

Long Term Conductivity Test
Procedure
• Increase stress to 2,000 psi.
• Flow fluid at rates of 33, 4 and 6 ml/min ml/min.
Measure Δ p 30 minutes after each step
change in flow rate.
• Measure frac width and temperature. Maintain
stress for 50 hr.
• Increase stress in 22,000 000 psi increments for 50
hours each.
• Continue measuring Δ p at 3, 4 and 6 ml/min of
fluid flow, frac width and temperature until
12,000 psi stress is reached.

AB A Better tt Test T tt to Select S l tP Proppant t
• Long term conductivity testing
• Direct measurement of flow capacity of
proppant pack
• Can account for:
– Embedment
– Temperature
– Fluid Effects
– Fines Migration g ( (with appropriate pp p flowrates) )

54
Chudnovsky, Univ of Ill, Chicago
Is complexity
solely attributed
to “rock rock fabric”? fabric ?
Unconsolidated 200 mesh sand, 35 lb XLG,
Flow � SPE 63233
Many other examples! [TerraTek, Baker, Weijers, CSM FAST consortium]

Frac Width – with CrossLinked Gel
Diffuse slurry
Modest concentration
w f
TSO + high concentration
We don’t envision thick
filtercakes in very tight rock,
but it doesn’t take much to
damage a narrow frac!
Diffuse slurry
Low concentration
2 ppa [240 kg/m3 pp [ g ] sand slurry y is
about 1 part solids to 7 parts liquid.
Final frac width could be ~1/7 th the
pumping width!
Navigation menu