SPE 119242

How to Use and Misuse Proppant Crush Tests –

E i th T 10 M thExposing the Top 10 Myths

John Kullman, CARBO Ceramics

T. T. Palisch, M. Chapman, R. Duenckel, and S. Woolfolk CARBO Ceramics IncWoolfolk, CARBO Ceramics, Inc. M. C. Vincent, Insight Consulting

Outline• Introduction/Motivation• Crush Test Procedure

M ths• Myths–Misuse/misapplicationpp

• Summary

The Big Picture• Fracs must provide:

– Reservoir contact (length, height) to contact and collect oil and gas

• Related to volume of proppantFlow capacity to carry oil and gas to the wellbore– Flow capacity to carry oil and gas to the wellbore

• Related to proppant permeability and frac width –described as conductivityy

• Other Important Proppant Characteristics– Durabilityy– Temperature Resistance– Transportability– Fluid CompatibilityFluid Compatibility– Flowback Control– Environmentally Benign

Question…G W ll• Gas Well – 7500 psi stress– 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 that they had the same MPD?y y– 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”

O i i l i t t t h l lif d– Original intent to help qualify sand sources• “Crush results” and proppant selection

“ lifi d i i l i i d f– “qualified engineering analysis….required for their application to a specific situation”SPE 11634 Conductivity comparisons cannot– SPE 11634 – Conductivity comparisons cannot be made on the basis of crush tests

**Yet many still choose their proppants based onYet many still choose their proppants based on crush results **

ISO 13503-2 Crush Test ProcedureP t i i d t• Proppant is pre-sieved to remove particles outside of stated mesh range.D t l d i t l• Dry proppant placed in steel cell at ~4 lb/sq ft (sand equivalent)Room temperature• Room temperature

• Proppant evenly distributed with level surfaceL d li d t if t• Load applied at uniform rate

• 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”For 16/20 proppant all material 20 mesh is reported as fines – For 30/50 proppant all material < 50 mesh is reported as “fines”

ISO 13503-2 Crush Test ProcedureDo 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 loaded”y• Dry, room temperature• 2000 psi/min relaxed after 2 minutes2000 psi/min, relaxed after 2 minutes• Only the particles smaller than bottom screen

are considered “fines” or “crush”are considered fines or crush

Are the results repeatable/reliable?Crush Cell Loading critical• “variance in crush results….associated with

method of loading…” • Significant efforts ongoing on ISO CommitteeSignificant efforts ongoing on ISO Committee

and StimLab to alleviate variations in resultsLoading technique thought to be the cause– Loading technique thought to be the cause

– Lab to lab, technician to technician, equipment to equipmentequipment

16/30 Brown Sand Hand Loaded Weight Percent Crush at 4000psi

Are the results repeatable?16/30 Brown Sand Hand Loaded Weight Percent Crush at 4000psi

22

24

26Test#1Test#2

18

20

22

h

Test#3

12

14

16

rcen

t Cru

sh 14.8% Avg

6

8

10Per

10.9

24.2

16.7

17.8

18.4

10.1

24.7

6.4

8.6

18.4

9.1

10.6

23.6

14.6

14.7

17.5

9.8

23.2

5.9

8.9

19.8

9.5

9.1

25.2

16.7

24.5

15.7

9.2

23.2

6.0

8.4

17.7

9.1

2

4

6

95 29 70 86 45 10 75 42 60 43 1063 60 60 71 52 80 29 92 90 88 5018 21 70 52 74 20 26 04 40 78 10

01 2 3 4 5 6 7 8 9 10 11

Lab Number ISO Subcommittee Results

16/30 Brown Sand Mechanical Loaded Weight Percent Crush at 18

Are the results repeatable?4000psi

16

18Test#1Test#2

12

14

h

Test#3

8

10

rcen

t Cru

sh 10.0% Avg

4

6

8

Per

9.

11.

12.

10. 9. 7. 9. 8. 9.

10.9.

16.

12.

10. 9. 8.

10. 8. 7.

10.9. 8.

12.

10.

10. 7.

10. 8. 7.

10.

2

4

No data reported.26

.41

.80

.79

.85

.76

.94

.40

.23

.60

.40

.66

.00

.89

.07

.40

.22

.20

.50

.80

.79

.96

.00

.32

.53

.80

.49

.40

.50

.10

01 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 have fewer g

load points• Crush increases significantlyCrush increases significantly

as proppant loading decreasesdecreases

• For a 20/40 proppant, there are approximately 24 layers of proppant in standard crush test24 layers of proppant in standard crush test.– 8% are exterior grains

1 lb/ft2 i 6 l f 20/40 t• 1 lb/ft2 is ~6 layers of 20/40 proppant– 33% are exterior grains

Crush Depends Upon Frac Width!p p

30

25

30

15

20

Cru

sh

10

15

erce

nt

5

P

04 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

100%

Crush vs # LayersCrush at 10,000 psi

20/40 Proppants

80%

90%White SandELWCRCSB it C i

60%

70%

Bauxite Ceramic

1 lb/ft2

40%

50%

60%

% C

rush

1 lb/ft21 lb/ft2

B it

Sand & RCS

20%

30%

40% 1 lb/ft2

ELWCBauxite

10%

20%

0%0 1 2 3 4 5 6 7 8 9 10

# of Layers

100%

Crush vs # LayersCrush at 1000 psiAll 20/40 Proppants

80%

90%White SandRCSELWCBauxite Ceramic

60%

70%

h

40%

50%

% C

rush

20%

30%1 lb/ft2

Sand & 1 lb/ft2 1 lb/ft2

0%

10%RCSELWCBauxite

0 1 2 3 4 5 6 7# of Layers

Partial Monolayer

RANGE OF FRACTURE COMPLEXITYSPE 77441SPE 77441

Simple Fracture Complex Fracturep p

Very Complex Fracture NetworkComplex fracs are

believed to provide less cumulative conductivity

than simple widerthan simple, wider fractures

Vertical Complexity D T J i tDue To Joints

Physical evidence of fractures nearlyfractures nearly always complex

NEVADA TEST SITENEVADA TEST SITEHYDRAULIC FRACTURE

MINEBACK16

Uniform Packing Arrangement?Arrangement?

Pinch out, proppant ill i lpillars, irregular distribution?

Is this ribbon laterally yextensive and continuous for hundreds orhundreds or

thousands of feet?17

Are Large Particles weaker than Small?1488 2 18 714

80.00

let

1488 2 18 714

80.00

1488 2 18 714

80.00

let

Si l P ll t C h NO!!y = 1488.2x - 18.714

R2 = 0.7765

50.00

60.00

70.00

ush

one

pell y = 1488.2x - 18.714

R2 = 0.7765

50.00

60.00

70.00 y = 1488.2x - 18.714R2 = 0.7765

50.00

60.00

70.00

ush

one

pell Single Pellet Crush

20 00

30.00

40.00CP

F

12/18Forc

e to

cru

20 00

30.00

40.00CP

F

12/1820 00

30.00

40.00CP

F

12/18Forc

e to

cru

141618

0.00

10.00

20.00

20/4016/20

12/18

Pou

nds

of F

0.00

10.00

20.00

20/4016/20

12/18

0.00

10.00

20.00

20/4016/20

12/18

Pou

nds

of F

81012

nt C

rush0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600

Proppant Size inches

P 0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600Proppant Size inches

0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600Proppant Size inches

P

Courtesy Stim-Lab

468

Perc

e

02

30/50 LWC 20/40 LWC 16/20 LWC 12/18 LWC

For all proppant types, larger grains have greater individual strength

140

160

greater individual strength.

100

120

140

CarboLiteHi k

12/18

20/40

60

80

100

CPF

HickoryInterpropCoSilicaJordan

20

40

ResinPR

00 0.02 0.04 0.06 0.08 0.1 0.12

Proppant Size, inchespp ,

Source: Stim-Lab Consortium, July 2001 1.8-16

Another Look at Single Grain Strengths…

140

160

100

120

140

CarboLiteHi k

12/18

20/40

60

80

100

CPF

HickoryInterpropCoSilicaJordan

20

40

ResinPR

Note that application of resin does not improve

00 0.02 0.04 0.06 0.08 0.1 0.12

Proppant Size, inches

pgrain strength, but rather improves distribution of stress between grains pp ,

Source: Stim-Lab Consortium, July 2001 1.8-16

and encapsulates fines.

So why does crush increase ith l t ?with large proppants?

• Strength in numbers?

“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

• SandQ t t l t d t lt i t b f fi h d– Quartz crystals tend to result in a greater number of fine shards

• Ceramics– Tend to cleave or part into relatively few, larger piecesp y , g p

• Resin Coated Products– Resin does not significantly change single grain strength, but

improves distribution of stress If the particles can beimproves distribution of 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?When they failWhen they fail…– Sands shatter like a glass

C i l lik b i k– Ceramics cleave like a brick– Resin Coated products

“deform”; fines captured

Brown Sand t 6k i

deform ; fines captured

at 6k psi.

IDC at 8k psi. RCS at 8k psi.

R b

Do fines affect all proppants similarly?Remember…• All proppants do not fail in the same manner

– The fines generated by one proppant may look drastically different than those generated by

thanother.• 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 t t bl tdifferent even at comparable stresses.

Post Crush Sieve Distribution

98100

ize

75

ent i

n Si

ge

After crushing 20/40

EconoProp at 6000 psi

25

50

ht P

erce

Ran

g Standard API technique

1.18 0.43 0.2 0.13 0.08 0

0

25

Wei

g

Source: CARBO Analyses Nov 1998

0-20/+40 -40/+50 -50/+70 -70/+100 -100/+200 -200/+325 Pan

A Closer Look at the Crushed FractionA Closer Look at the Crushed Fraction “2% fines” reported with standard

testing could mean 2 cleaved grains

1.181.00

1.20

Immobile cleaved grains

testing could mean 2 cleaved grains per 100 (4 immobile pieces), or it could represent 400 mobile fragments in the

100-mesh range

0.80

Cru

sh

Immobile cleaved grains It makes a difference!

0.43

0.20.40

0.60

Perc

ent C Potentially mobile in 20/40 pack

(SPE 24008)

0.13 0.0800.20

P

0.00-40/+50 -50/+70 -70/+100 -100/+200 -200/+325 Pan

Source: CARBO Analyses Nov 1998

Fluid Effects• Crush testing is performed dry. What if the proppant

is saturated?is saturated?

6

7Modified Crush Test Results

E P t 6000 i

4

5

t Cru

sh

EconoProp at 6000 psi

2

3

Perc

ent

0

1

Dry API Moisten in cell Moisten in cell Moisten with Moisten with

Source: CARBO Tech Brochure 3/4/96

Dry API Moisten in cellwith water

Moisten in cellwith min. oil

Moisten withwater, thenadd to cell

Moisten withmin. oil, then

add to cell

Is one set of Test Conditions superior to another?Dry, wet, hot, room temperature, water or oil…

6k Crush @ 2#/ft2

y, , , p ,is one method more realistic than another?

30

35SandELWC

20

25

ush

%

RCS

5

10

15

Cru

0

5

StandardLoading

Load byhand and

Load byhand and

Standardthen tap

Standardthen wet

Standardthen wet

Wet withwater then

Wet withmineral oil

Standardbut heat to

Standardbut heat tog

rotatepiston

do notrotatepiston

pcell with water with

mineral oilload into

cellthen loadinto cell

200F dry 200F wet

Can Crush results be Correlated to Conductivity?

More Realistic Conditions in a Conductivity TestWhat’s the Difference?

• Proppants evaluated as receivedpp• Tests equivalent mass loading, and 2 lb/ft2• Utilizes Sandstone shimsUtilizes Sandstone shims• Flow water through pack• Elevated temperatures (150° or 250° F)Elevated temperatures (150 or 250 F)• Stress held for at least 50 hours

Disassembled API Proppant Cell

Ports for MeasuringDifferential Pressure Temperature Port

Proppant Bed

Sandstone CoresFlow ThroughProppant Bed

Long Term Conductivity Cells

Can Crush results be Correlated to Conductivity?The “crush” measured after a Conductivity test

6k Crush Results vs Crush after Conductivity Testing at 6k psi45

significantly higher than Crush test.

30

35

40 SandELWCRCS

20

25

30

Cru

sh %

RCS

5

10

15

C

0

5

StandardLoading

Load byhand and

rotate

Load byhand and

do not

Standardthen tap

cell

Standardthen wet

with water

Standardthen wet

with

Wet withwater thenload into

Wet withmineral oilthen load

Standardbut heat to200F dry

Standardbut heat to200F wetrotate

pistondo notrotatepiston

cell with water withmineral oil

load intocell

then loadinto cell

200F dry 200F wet

All tests at 2 lb/ft2 loading

EmbedmentEmbedment

More width retained, but lower perm

Spalling

SpallingSpalling

Example of Conductivity Loss CO N D U CT IV IT Y V S . CLO S U R E S T R E S S

100000YME=5E6psi

10000S t im - L a b In c .

P re d k F 0 2

YME=5E6psiYME=1E6psiYME=.5E6psiYME=.1E6psi

1000`

10

100

100 2000 4000 6000 8000 10000 12000

C L O S U R E S T R E S S - P S I

1 0lb/ ft 20/40B d 150°F 1 0lb/ ft 20/40B d 150°F1.0lb/s qft 20/40Badger150°F 1.0lb/s qft 20/40Badger150°F

1.0lb/s qft 20/40Badger150°F 1.0lb/s qft 20/40Badger150°F

Source: Stim-Lab Consortium, Feb 2002 1.6-46

Proppant DurabilityIn the real world:

- Fractures are subjected to high stressesFractures are subjected to high stresses (increasing) for extended periods of time

- Stress levels fluctuate (cyclic stress) with ll k d h i liwellwork and changes in line pressure

Therefore:Therefore:

• All proppants appear to lose conductivity over titime

• Traditional resins do not appear to protect proppants from degradation.p oppa s o deg 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 Fig 4 SPE 16415laboratory expense and accuracy. Fig 4, SPE 16415

1000

d-ft) 20/40 Jordan sand,

8000 psiLonger test captures a portion of

ctiv

ity (m

d 8000 psiLonger test captures a portion of the time-dependent decline. We

know degradation continues beyond this, but modern “50 hour”

100Con

ducy ,

tests include correction for initial repacking/etc.

This phenomenon occurs even0 25 50 75 100

Hours at Constant Stress

This phenomenon occurs even with silica saturation

Reference: SPE 16415 Norton and Stim-Lab

Extended duration tests:1984

(75 & 250F)API “short term” cell: Metal plates, continuous flowing 2% KCl,

Non silica saturated

Fig 19, SPE 12616 between metal plates100

vity

Non-silica saturated

60

80

Con

duct

iv 20/40 Sand at 75F10/20 Sand at 250F

20

40

Orig

inal

C

00 30 60 90 120 150 180 210 240 270 300

% O

Reference: SPE 12616 by Montgomery, Steanson, Schlumberger

Days at Constant Stress, 5000 psi

40

Published extended duration tests:19861986

93C (200F)All non-corrodible surfaces, prop in

Teflon tube, continuous flowing 2% KCl 1986(300F)

Fig 4, SPE 14133

0.8

1

Rat

io

(300F)Teflon tube, continuous flowing 2% KCl,

Non-silica saturated

0.4

0.6

mea

bilit

y R

CarboPROP at 10,000 psi (69 MPa)CarboLITE at 10,000 psi (69 MPa)

SPE Drilling, April 1986, page 510000

md-

ft)

0

0.2

0 15 30 45 60 75

Perm CarboLITE at 10,000 psi (69 MPa)

Sand at 5000 psi (35 MPa)1000

nduc

tivity

(mInterpropProflow

Days at Constant Stress100

0 10 20 30 40 50

Days at Constant Stress, 8500 psi

Con RCS

Ottawa Sand

References: SPE 14133 by CARBO, SPE Drilling article by Norton-Alcoa Proppants and TerraTek Research

41

Temperature Correction for White SandAt 6500 psi and 250F, 20/40 White Sand loses

40% f it d ti it d t 150F

1

20/40 Premium White Sand

r

40% of its conductivity compared to 150F.

0.8

1

eg F

, fac

tor

0.6

from

150

de

0.4150 deg F

Cor

rect

ion

f

0.2200 degF250 deg F300 deg F

nduc

tivity

C

00 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

350 deg F

Con

Stress, psi StimLab PredictK

Cyclic Loading of Proppant Packs• All proppants appear to be damaged by

continued stress cyclingcontinued stress cyclingEffect of Stress Cycling on Proppants

Three cycles, 6000 to 1000 psi15% loss

4,000

5,000

md-

ft) 50 hrs at 6000 psi3 cycles, 6000 to 1000

32% loss23% loss2,000

3,000

nduc

tivity

(m

3 cycles, 6000 to 1000

-

1,000Con

Source: CARBO Tech Rpt 99-062

RCS #1 RCS #2 EconoPropProppant Type (all 20/40)CARBO Tech Rpt 99-062

Effect of Stress Cycling on Proppant Conductivity(Stim-Lab July 2000 data)

St ( i)

8 000

9,000

10,000 Stress (psi)LWCRCS

6 000

7,000

8,000

(md-

ft)

Ceramic loses 26%

4,000

5,000

6,000

duct

ivity

( Ceramic loses 26%,RCS loses 35% due to 25 cycles

2,000

3,000Con

d

-

1,000

0 100 200 300 4000 100 200 300 400

Hours

Effect of Stress Cycling on Proppant Crush (6000 psi)on Proppant Crush (6000 psi)

25

300

Single Crush at 6000 psi

Triple Cycle Dry Crush

20

25

rush

th

an 4

0 Triple Cycle Dry Crush

Triple Cycle Crush in Long Term Cell

10.44

15.79

15

cent

Cr

mal

ler t

mes

h)

3 33 3.83 3 02

8.47

5

10Perc

(wt%

sm

1.373.33

1.921.523.02

-

5(

RCS #1 RCS #2 EconoPropProppant Type (all 20/40)CARBO Tech Rpt 99-062

Options to reduce crush: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 stressgInclude deformable “cushioning” agents

⇓ ⇓

The Correct Way to Test Proppant• Remember, proppant must achieve two goals:

– Reservoir contact (proppant volume)(p pp )– 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)– 50 hour duration (or longer)– Cyclic stress, embedment, fines migration, non-Darcy and

other issues can be investigated in specialized testsg p– Directly measures parameters of interest [frac width and

flow capacity]

SPE 119242SPE 119242

How to Use and MisuseHow to Use and Misuse Proppant Crush Tests –

Exposing the Top 10 Myths

Questions?

Darcy’s Law vs Forchheimer EquationDarcy s Law vs. Forchheimer Equation

Δ P/L / k• Δ P/L = μ v / k– Pressure drop is proportional to fluid

l itvelocity– Applicable only at low flowrates

• Δ P/L = μ v / k + β ρ v2

– Pressure drop is proportional to square of fluid velocityfluid velocity

– Applicable at realistic fracture flowrates

D F t Width Aff t C h?Does Fracture Width Affect Crush?

• Crush increases significantly in narrow fracturesfractures

Interior grains are loaded “evenly” on 6 sides

Exterior grains are not

evenly on 6 sides

Exterior grains are not stressed uniformly

Long Term Conductivity Test g yProcedure

• 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• Apply a vacuum for 45 minutes to remove air in

cells.• Flow 2% KCl solution through heated silica sand,

d lland cells.• 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 TestLong Term Conductivity Test Procedure

• Increase stress to 2,000 psi. • Flow fluid at rates of 3 4 and 6 ml/minFlow fluid at rates of 3, 4 and 6 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 2 000 psi increments for 50Increase stress in 2,000 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.

A B tt T t t S l t P tA Better Test to Select Proppant

• Long term conductivity testing• Direct measurement of flow capacity ofDirect measurement of flow capacity of

proppant pack• Can account for:Can account for:

– Embedment– TemperatureTemperature– Fluid Effects– Fines Migration (with appropriate flowrates)g ( pp p )

Is complexity solely attributed to “rock fabric”?to rock fabric ?

Unconsolidated 200 mesh sand, 35 lb XLG,Flow SPE 63233

Chudnovsky, Univ of Ill, Chicago

Many other examples! [TerraTek, Baker, Weijers, CSM FAST consortium]54

Frac Width – with CrossLinked GelDiffuse slurry

Low concentrationDiffuse slurry

Modest concentrationTSO + high concentration

2 ppa [240 kg/m3] sand slurry is

wfWe don’t envision thick

filtercakes in very tight rock, but it doesn’t take much to

damage a narrow frac!

pp [ g ] yabout 1 part solids to 7 parts liquid.

Final frac width could be ~1/7th the pumping width!

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