Role of multiple fracturing of vertical and Horizontal ......• Hydraulic fracturing is an integrated part of field development • Behavior of a hydraulic fractures are affected

$Page 1: Role of multiple fracturing of vertical and Horizontal ......• Hydraulic fracturing is an integrated part of field development • Behavior of a hydraulic fractures are affected$
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HGS Applied Geoscience Conference (AGC) “Drilling and Completion Through the Life of the Field” November 2019

Role of multiple fracturing of vertical and Horizontal Wells in Maximizing production and extending life of the field

M. Y. Soliman, Ali Rezaei, Fahd Siddiqui, University of Houston


Outline• Hydraulic fracturing and field development • Hydraulically‐fractured systems: design and arrangement

– Why multiple fractures – Effect on production– Geomechanical consequences

• Fracturing and reservoir depletion– Low permeability formations– Naturally‐fractured formations– Effect of pore pressure depletion on local stresses

• Re‐fracturing and infill well fracturing– Is it required? – Vertical well: re‐fracturing– Horizontal well: re‐fracturing, infill well fracturing– Geomechanical considerations for infill drilling and refracturing

• Summary

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Hydraulic Fracturing and Field Development

Horizontal well fracturing Pad drilling

Haynesville Shale


Fracturing Low Permeability Formation

• High density fracturing is important to maximize fluid flow

• Re‐fracturing may be necessary

• Both have Geomechanics consequence

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Oil Phase Pressure, Permeability = 1 md


Oil Phase Pressure, Permeability = 0.1 md

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5




Fracturing Naturally‐Fractured Formations

Kazemi et al, 1992

• Model consists of matrix and fracture (other than hydraulic fractures)

• Flow from both matrix and fractures

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Oil Phase Pressure, Fracture System


Oil Phase Pressure, Matrix

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0

1

2

3

4

5

6

7

8

9

10

0 500 1000 1500 2000 2500 3000

Cumulative Gas Production, B

scf

Time, days

Fractured

Fractured After 2 Years

Fractured After 4 years


Un‐Fractured

Cumulative Gas Production


0

10

20

30

40

50

60

70

0 500 1000 1500 2000 2500 3000

Cumulative Condensate

Production, 1000 STB

Time, days

Fractured


Fractured After 4 years


Un‐Fractured

Cumulative Condensate Production

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Hydrocarbon Recovery at 10 Years; Permeability vs. Well Type

VerticalVerticalFraced Horizontal

HorizontalAxial Frac Horizontal 5

Transv.Fracs

Horizontal11 Transv.Fracs Incr

Lf

5

0.5

0.05

0.005

0%

5%

10%

15%

20%

25%

30%

Recovery at 10 Years (Cum/OOIP)

Well Type

Permeability md

Oil Well

VerticalVerticalFraced Horizontal

HorizontalAxial Frac Horizontal

5 Transv.Fracs

Horizontal11 Transv.Fracs Incr

Lf

0.5

0.05

0.005

0.0005

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Recovery at 10 Years (Cum/OGIP)

Well Type

Permeability md

Gas Well


Fractured Systems

• Design and arrangement• Effect on production• Geomechanical consequences

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Effect of Fracturing and Refracturing

All fractures Some fractures Re‐fracturing


Multiple Fracturing of Vertical Wells

• Proposed for – Low perm formation

– Declining fracture productivity

• Observed during drill cutting re‐injection

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1000

2000

3000

4000

5000

6000

0 10 20 30 40 50 60 70 80 90

Str

ess,

psi

Theta, degree

Tangential Stress No Fracture

Tangential Stress after One Fracture

Tangential Stress at Wellbore Wall


Tangential Stress at Wellbore Wall

Tangential Stress along the Wellbore Wall

-10000

-5000

0

5000

10000

15000

20000

0 10 20 30 40 50 60 70 80 90

o

Tan

gen

tial

Str

ess,

psi

W Frac, SH=Sh W/O Frac, SH=Sh W Frac, SH=1.5Sh W/O Frac, SH=1.5Sh

W Frac, SH=2Sh W/O Frac, SH=2Sh W Frac, SH=3Sh W/O Frac, SH=3Sh

Sh=3000 psi

Pw=6000 psi

Pf =2000 psi

rw=4.25 inch

Lf=6 inch

E=1,090,000 psi=0.225

Wang, et al, SPE 201719

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Multiple Fractures in Vertical Wells

Cumulative production comparison for one and two fractures

0

100

200

300

400

500

600

700

800

900

1000

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Time, days

To

tal

Pro

du

ctio

n,

mm

cfSingle Frac

Two fracs


Multiple Fractures in Horizontal Wells

Alternating Fracturing

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Propagation of Multiple Fractures (Clusters) from a Horizontal Well

• Intra‐Well fracture Interaction (frac‐hits)– Interaction between active and passive fractures

• Inter‐Well fracture Interactions– Interaction between fracture and offsetting wells

• Stress Shadowing– Stress alteration caused by deformation due to fracturing


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Swain 1978, Pollard 1984, Atkinson 1987

Microcrack in Glass

A vein in granite Rock

a dikeOverlapping

spreading centers

Fracture Interactions in Nature

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Propagation of ClustersHorizontal well

Displacement, m Stress anisotropy, MPa

Shear stress, MPa Minimum horizontal stress, MPa Maximum horizontal stress, MPaY, m

Y, m

Y, m Y, m

Y, m

X (horizontal well direction), m X (horizontal well direction), m

X (horizontal well direction), mX (horizontal well direction), m X (horizontal well direction), m


Overlapping Zones of Two Interacting Fractures

Rezaei, et al 2015ARMA-2015-449

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Modified Zipper Frac (MZF), Non‐Symmetric

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Well A

Well B


Modified Zipper Frac, Symmetric

Rezaei, et al 2015ARMA-2015-449

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Six SurgiFrac Waterfracs performed consecutively for an Openhole Chert horizontal wellbore


Re‐Fracturing and Infill Fracturing• Purpose• Vertical wells: re‐fracturing• Horizontal wells: re‐fracturing, infill well fracturing• Geomechanical considerations

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Why is Re‐fracturing Needed?

Original Original + re‐fracturing

SPE 134330


Effect of Re‐Fracturing on Flow Rate

SPE 136757

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Example of a Successful Re‐Fracturing

SPE 136757


Re‐fracturing

• In Early 80’s

• Multiple fractures in different orientations from a vertical well– Perpendicular Fractures from late 80’s

– Testing and refrac of a vertical well

– Multiple fractures/application to drill cuttings injections

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Vertical Well Re‐fracturing

• Proposed for – Low perm formation

– Declining fracture productivity

• Improves reservoir access

• Restore production

• Reorientation is desirable– Stress reversal helps

• Usually one fracture exist in the wellbore

Figure Source:American Oil and Gas Reporter


Issues with Refrac of Horizontal Wells

• Plug existing fracs– Natural loss of conductivity with time

– Use plugging agent –chemical

– Multiple proppant sizes

– Perforate newer areas

• Drill Infill wells (Child Wells)

• Intra‐Well Interaction (frac‐hits)

• Inter‐Well Interactions

• Stress Shadowing and reversal

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Pore Pressure Depletion

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1 day 1 month 1 year 3 years

Rezaei et al (doi: nag.2792)


Changes of Magnitude and Direction of Stresses with Time

1 day 1 month 1 year 3 years

Black lines are the direction on top of pore pressure depletion Rezaei et al (doi: nag.2792)

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Effect of the Pore Pressure Depletion on Refarc Propagation

Rezaei et al (doi: nag.2792)


Infill Well Fracturing

SPE-181656-MS SPE-181767-MS

Parent well attracts the fractures that are initiated in the infill well Microseismic activity around parent well

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Infill Well Fracturing Problems

Fracture shadow

Direct hit

Variable pressure hit

SPE 171628


SPE 189853

Consequences of Frac‐Hit

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Safari et al, SPE 178513

Propagation Path for Infill Well Fracture

2ye

ars

6 months

1 ye

ar3

year

s

= 57 MPa

Bothparentandchildwellsarepressurized

Onlyinfillwellispressurized

Rezaei et al, 2019

URTeC 2667433


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Other Factors Affecting Propagation of Infill Well Fracture

Well spacing Parent well fracture spacing

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= 56 MPa

Stress anisotropy1.38 MPa

= 56 MPa

Stress anisotropy2 MPa

Stress anisotropy3 MPa

= 56 MPa

Other Factors Affecting Propagation of Infill Well Fracture. Cont.'s

Stress anisotropy

= 56 MPa

= 57 MPa

= 59 MPa

Pump pressure


Summary

• Hydraulic fracturing is an integrated part of field development• Behavior of a hydraulic fractures are affected by:

– Induced mechanical changes in stress regime (stress shadow)– Pore pressure depletion that causes redistribution of stress (stress

reversal)

• Stress shadow affects the fracture behavior in multi‐fracture systems• Stress reversal:

– Helps re‐fracturing vertical wells– Not desirable for horizontal wells

• Both stress shadow and reversal affect the final recovery from reservoir by influencing hydraulic fractures behavior.

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[email protected]

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Documents

Role of multiple fracturing of vertical and Horizontal ......• Hydraulic fracturing is an integrated part of field development • Behavior of a hydraulic fractures are affected