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Hydraulic Re-Fracturing*

Neil Stegent1

Search and Discovery Article #40837 (2011)Posted November 14, 2011

*Adapted from presentation at AAPG Geoscience Technology Workshop, International Shale Plays, Houston, Texas, September 27-28, 2011

1Pinnacle-A Halliburton Service ([email protected])

Abstract

A discussion and review of re-fracturing of both vertical and horizontal wells. Discussion of basic fundamentals of hydraulic

fracturing, reasons to re-frac, candidate selection, operational considerations, and case histories.

Copyright AAPG. Serial rights given by author. For all other rights contact author directly.
mailto:[email protected]:[email protected]:[email protected]:[email protected]


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Hydraulic Re-Fracturing

Neil Stegent, P.E.

Technology Manager - Fracturing

v1


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Re-Frac Case History Papersnotall inclusive

Vicksburg, S. Texas SPE 4118Canyon Sand, Texas SPE 4800

Antrim Shale, MI SPE 29172Gray Sand, Cotton Valley, LA SPE 29554

scon o an s one, exas

J Sand, Wattenberg, CO SPE 7936Undisclosed low pressured field, SPE 14376Oak Hill, Cotton Valley E TX + LA SPE 14655Morrow, Red Fork, Atoka, OK SPE 18861

mon amsu e ,

Green River Frontier, WY+ Piceance Basin, CO SPE 55627Piceance Basin, CO and GGRB, WY SPE 56482Viking, Ferrier, Alberta Pet Society 99-60

Smackover, Mississippi SPE 19768Mesaverde Group, CO & NM SPE 24307McAllen Field, Vicksburg, S. Texas SPE 24872

Eastern Gas Shales-Antrim, MI and

Barnett Shale, TX SPE 63030Cotton Valley TX SPE 63241Codell, DJ Basin, CO SPE 67211, 71045, OGJ 2006

Medicine Hat, Milk River, Alberta SPE 81730

Mendota, Granite Wash, TX SPE 27933.

Refracs - Why do they work, and Why do they Failin 100 Published Field Studies?

-

2011 HALLIBURTON. ALL RIGHTS RESERVED.


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Hydraulic Fracture Design

McGuire & Sikora Curves

fraczone

fracfrac

rXk

wkC

fraczone

fracfrac

rXk

wkC



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What is a Hydraulic Fracture? overburden

w2

w1

max

h

L

min

v

Wellbore

file

m ax

StressP

r


min


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Whats Fractures Really Look l ike.........

Fracture

Bedding Planes



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Whats Fractures Really Look l ike.........

SPE 114173 and 77441



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Initial Hydraulic Fracture Completion:

3500

4000

4500

te,

Mscf/D

1500

2000

2500

3000

Averagegasproductionr

Frac Design

1000

0 20 40 60 80 100

Time, day

Production



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Reasons to Refrac:

Improve original fracture conductivity Alter fracture geometry Restoration fracture conductivity of Proppant Embedment SPE 135502

Embedment Stress cycling Dia enesis Scale/Fines

Restore near-wellbore conductivity Stimulatin b - assed a intervals Utilize new Technology Re-energizing or re-inflating natural fissures

refrac often contacts new rock



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Reasons to Refrac:







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ncrease r g na o ze



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Restimulation of Oil Wells

SPE 101821

40

100

120

s)

20

25

30

35

Proppant

Initial Frac 60

80

Pressure

(bar

Initial Frac

Refrac

5

10

15

Tonneso Refrac

0

20

40

Reservoir

Well A Well B Well C Well D Well E

Fig. 14 Restimulation Treatment Sizes were 135% Larger


Fig. 15 Reservoir Pressure declined approximately 15%

Despite pressure depletion of ~15%, refracs provided large benefits

Refracs were designed to improve conductivity, proppant mass increased by 135%.



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Restimulation of Oil Wells Increased Job Size

SPE 101821

120

)

80

100

onnes/da

Initial Frac

Refrac

40

60

nRate(t

20

Producti

0


Production from restimulated wells increased by an average of 37 t/da


(~ 275 bbls/Day)


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Re-fracture due to change in rock Stress

Stress Stress

Sand Depleted

Shale



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7820

7700

Stress Profile

Concentration of Proppant in Fracture (lb/ft)

Re-Fracture Treatment


8300

8180

8060

7940

Depth(ft)

esu s n onger

Fracture

8780

8660

8540

8420

Permeability Proppant Concentration (lb/ft)7900 Stress Profile

Concentration of Proppant in Fracture (lb/ft)


5000 6000 7000 8000 90008900

Closure Stress (psi)

Low High 0.00 0.30 0.60 0.90 1.2 1.5 1.8 2.1 2.4 2.7 3.0

0 300 600 900 1200

Length (ft)

8380

8260

8140

8020

(ft)

8860

8740

8620

8500

Permeabilit Pro antConcentration (lb/ft)

Depth

Original Fracture Grows


5000 6000 7000 8000 90009100

Closure Stress (psi)

Low High

0.00 0.30 0.60 0.90 1.2 1.5 1.8 2.1 2.4 2.7 3.0

0 300 600 900 1200

Length (ft)

pwar an s or


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Re-fracture to remove near wellbore damage

Refrac

Post-FracDecline

62%

Re-Frac placed 74,000 LBS5 PPG

Post-ReFracDecline

40%



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Reasons to Refrac: Candidate Selection







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New Technology: By-Passed Pay

kh Profile

0 0.5 1 1.5

kgh, md-ft

Low Res PayHigh Clay Content

1

2

3

4

5

6

7

Z

o

ne

9000 3000

LowClay

9

10

117000

8000

1500

2000

2500

cac ps

dP/dG

GdP/dG

Closure @ 6,085-psi

12

13

145000

6000

500

1000dP/dG = 750


0 1 2 3 4 5 6 7 8

G -function

DFIT Diagnostic Fluid Injection Test


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Increased Production: Re-frac by-passed Pay Zones

2500

20001,818 mcf/d Average

1000

1500

810 mcf/d Average

500

0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Well Test Number



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Reasons to Refrac: Candidate Selection







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Re-Frac with Different Frac Design: SPE 95568

Original Frac: Viscous Polymer Gel Fluid

30003000 2500

3000

Perforations

2000

2500

2000

2500

1500

2000

h

(ft)

Observation Well 1

1000

1500

rth

ing

(ft) Observation Well 1

1000

1500

uth

-North

(ft)

Observation Well 1

500

1000

South-Nort

0

500N

Perforations

0

500S

Observation Well 2 -1000

-500Observation Well 2

-1000

-500

-1000 -500 0 500 1000 1500 2000 2500

Observation Well 2

-1000

-500

-1000 -500 0 500 1000 1500 2000 2500

- -

West-East (ft)

Re-Frac: Low Viscosity Water Frac Fluid


Easting (ft)West-East (ft )


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Re-Frac with Different Frac Design: SPE 95568



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-



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Re-fracture Reorientation - Barnett Shale

-



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Original FractureOrientation

Re-FractureOrientation



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Reasons to Refrac:





SPE 134330 by Mike Vincent


e racs - y o t ey wor , an y o t ey ain 100 Published Field Studies?


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Thank You

30

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Re-frac job by HBT