Perforating Design for

Sand Control Applications

Types of Perforators

Perforating Guns

Shaped Charge Detonation

• Detonating Cord: 25,000 - 30,000 ft/sec

• Shaped Charge Jet Develops 4 - 7 Million psi At It’s Tip Before Making Contact With The First Target

• Liner Material Provides The Mass Necessary For Penetration

• Perforating event takes no more than 1/32,000th of a second.

• Jet pressure parts steel, cement, and formation rock, creating a “crushed zone” of reduced permeability.

• Proper underbalance is required to remove perforating skin.

Perforating Charge Prior To Detonation

Initial Jet Formation Penetrating Steel

Perforation Sequence Complete

Shaped Charge Standoff And Clearance

CN03197

CEMENT

CASING

CLEARANCE

VANNGUN

STANDOFF

Vanngun Phasing 0° PHASING

1 ROW OF HOLES

140/160° PHASING

4 ROWS OF HOLES

60° PHASING

6 ROWS OF HOLES

45° PHASING

8 ROWS OF HOLES

72° PHASING

5 ROWS OF HOLES

30° PHASING

12 ROWS OF HOLES

90° PHASING

4 ROWS OF HOLES

180° PHASING

2 ROWS OF HOLES

51.4° PHASING

7 ROWS OF HOLES

60° PHASING

2 ROWS OF HOLES

CN02310

Determining the Proper Underbalance

Productivity Ratio As A Function Of Penetration And Shot Density

CN03199

0

3

6 9 1 1

5 18

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1

2

4

6 8

1

2

PERFORATION LENGTH -

INCHES

SH

OT

S P

ER

FO

OT

PR

OD

UC

TIV

ITY

RA

TIO

NO CRUSHED ZONE NO FLUID DAMAGE 6" DIAMETER HOLE EXTRAPOLATED DATA

Spiral 90 phased

90 phased

180 phased

0 phased

1 spf

2 spf

4 spf 6 spf 8 spf

12 spf

.7

1.0

1.2

10

Shot Density Selection

• Marathon and Conoco stated that in most completions, only 25% of the perforations flowed at maximum potential.

• Choose a shot density that will give a Productivity Ratio of 1, even with 50% of the perforations plugged.

• If total skin is removed, depth of penetration is less important than shot density.

• Choose a shot density and phasing that will promote Laminar flow to the well bore.

Consolidated Formation

Unconsolidated Formation

A. Sonic Log Shale = 100 ms/ft. or Less

B. Density Log Shale = 2.4 gm/cc or More

A. Sonic Log Shale = Greater than 100

ms/ft.

B. Density Log Shale = Less than 2.4

gm/cc

150 100 50

100 5800

5400

100 150 50

110

120

Microsec/Ft.

Microsec/Ft.

Underbalance Pressure Used On Tubing Conveyed Perforating In Oil

Zones In Sandstone

CN03202

100 1000 10,000 TOTAL

UNDERBALANCE

PSI

FO

RM

AT

ION

PE

RM

EA

BIL

ITY

MD

0.1

1

10

100

Courtesy - George King, SPE 14321

Acid did not improve production

Acid did improve production

Legend

l

.1

1.0

100

1,000

10

Acid did not improve production Acid did improve production

.01

Underbalance Pressure Used On Tubing Conveyed Perforating In

Gas Zones In Sandstone

CN03203

100 1000 10000

TOTAL

UNDERBALANCE

PSI

FO

RM

AT

ION

PE

RM

EA

BIL

ITY

MD

0.01

0.1

1

10

100

100

0

Acid did not improve production

Acid did improve production

Problems

Legend

l

Stuck Packer

Casing Collapse

Problem Acid did not improve Acid did improve .1

1.0

10

100

1,000

VannSystems Chart-Density Data

CN03204

0 250 500 750 1000 1250 1500 1750 2000 2250 2500

MAXIMUM PRESS. UNDERBALANCE - PSI

FOR UNCONSOLIDATED SANDS

2.40

2.30

2.20

2.10

2.00

1.90

1.80

BU

LK

DE

NS

ITY

OF

AD

JA

CE

NT

SH

AL

E -

gra

ms/c

c.

USING DENSITY DATA TO DETERMINE

PERFORATING UNDERBALANCE PRESSURE

Oil Sand

Gas Sand

180

170

VannSystems Chart-Acoustic Data

CN03205

0 250 500 750 1000 1250 1500 1750 2000 2250 2500

MAXIMUM PRESS. UNDERBALANCE - PSI

FOR UNCONSOLIDATED SANDS

100

110

120

130

140

150

160

²T A

DJ

AC

EN

T S

HA

LE

- M

ICR

OS

EC

ON

DS

PE

R F

OO

T

USING ACOUSTIC DATA TO DETERMINE

PERFORATING UNDERBALANCE PRESSURE

170

Oil Sand

Gas Sand

90

170

130

Managing Pressure Drop

• Perforator Penetration is of lesser importance provided that the perforation communicates with the reservoir.

• Deep Penetrating Charges: Small entry hole, large pressure drop = sand and/or fines production

• Big Hole Charges reduce the pressure drop through the gravel pack. Flow area is critical in reducing turbulent flow.

• Shot Phasing creates laminar flow thereby reducing sand production.

• Centralize Vannguns when perforating with BH charges.

Managing Pressure Drop

• If 2/3’s of the perforations cross sectional area is filled with gravel, then a well perforated @ 12 spf has an effective flow area of only about 4 spf.

• Chose a perforator with the largest hole size and the greatest number of shots available.

• Keep in mind that after 18 spf, a point of diminishing returns is reached.

Useful Formulae

Equations for Underbalanced

Perforation Design

Minimum Underbalance from Permeability

• Pub=2,500/k psi, for k<1 md (gas)

• Pub=2,500/k^.18 psi, for k > 1md (gas)

• Pub=2,500/k^.30 psi, for oil

Maximum Underbalance from Adjacent Shale

For DTas > 90 mu s/ft.

• P umax gas = 4,800-25(DTas), psi (gas)

• P as max oil = 3,500-19(DTas), psi (oil)

To Find the Recommended Underbalance

Maximum Underbalance

If DTas < 90 mu s/ft

• P u max tub.= max safe pressure of down hole tools and cement.

Recommended Underbalance

If there is no history of sand production

• P u rec..= 0.2 * Pu min + 0.8 * P u max

If there is a history of sand production

• P u max =0.8 * P u min+ 0.2 * P u max

Well Clean Up

• A good rule of thumb is to flow back 12 gallons of formation fluid per perforation. If the proper underbalance was used, this should clean up all of the perforations.

– So: 60 feet X 18 spf =979

shots

– 979 * 12 gals. = 11,748 gal.

– Or 261 Bbls.

Case Histories

• Australia: DST’s @ 3.2 MMCFD. Perf’d with Thru Tubing Guns, well produced @ 150 MCFD. Reperforated with TCP guns @ 6 spf, 3,000 psi drawdown. Well flowing @ 4.5 MMCFD.

• Indonesia: Typical Completions perforated with 500 psi Drawdown. Wells flowed between 2-5 MMCFD. Began program of high underbalance shoots, wells now flowing @ 12-15 MMCFD.

Marathon / Halliburton Perforation Damage

Study

What You Want

CN03159

What You Get

CN03116

Perforating...

• Each Shaped charge exerts up to 4-6 million psi on the reservoir.

• This force crushes and compacts the reservoir rock.

• You cannot “shoot through” perforating damage.

• Some remedial action is required:

– Underbalance Perforate

– Extreme Overbalance

Perforate

Perforating

The worst thing to do in most cases is to perforate in a balanced state.

Perf A - Cu/Zn 4.625” Gun Perforation Tunnel

Undisturbed Sand Grains

Particle Size Analysis Undisturbed Sand

Damaged Sand From Zone 1

Damaged Sand From Zone 2

Particle Size Analysis Zone 1

Conclusions

• The rock grains cannot withstand the shock loads associated with perforating

– (A function of both peak pressure and

loading rate)

• The damage patterns are different in shape in DP and BH charges.

– Can create an excellent filter cake to limit

injectivity : even DP charges (EOB results)

• Larger explosive weight charges may not be a wise choice in many instances

• Centralize perforating guns

• In hard rock, expect 40% of API published data, sometimes even less.

Kiss Charge

How Much Fluid Loss Should be Expected After

Perforating?

• Offshore Well

– 500 md perm

– 50’ interval

• 200 psi overbalance

• What is typical?

– 0 - 20 BPH (at balance)

– 40 - 60 BPH (with

underbalance & flow)

• RISKY/Expensive

Q = (200 psi)( 500 md)( 50 ft)

141.2 (.5 cp)(( ln (660/.25))

Q = 8,990 BPD Fluid Loss

or

375 BPH Fluid Loss

We are lucky to see 10% of this

number

Darcy’s Law - Fluid Loss

Perf G - “Minimal Penetrator Design” 4.625

Gun System (KISSTM Charge)

Cement Puncture

Imbedded Debris

Perf G - “Minimal Penetrator Design” 4.625

Gun System (KISSTM ) Charge)

Perforation Tunnel

Perf D - 7” Aluminum Liner Charge

Zero Clearance Perforation Tunnel

Outer Propellant

Cylinder

“Combination” Perf/Propellant

Assembly

Conventional

Perforating

Carrier

System

Modified

Charge

Designs

“StimGunTM” Assembly

General Mechanism

• The propellant is positioned and fired over the completion interval.

• As the propellant burns it produces a pressure load on the formation below the formation rock’s compressive yield strength.

General Mechanism

• As the propellant burn pressure increases strain energy is accumulated in the rock matrix until the circumferential stress around the wellbore exceeds the strength of the rock.

• At this point fracturing occurs.

Propellant vs. Perforating

- 1 5 0

- 1 0 0

- 5 0

0

5 0

1 0 0

1 5 0

2 0 0

Pre

ssu

re L

oad

ing

Rate

- G

Pa/s

Propellant - 1,258 - 1,260m

- 1 0 0 0

- 5 0 0

0

5 0 0

1 0 0 0

Pre

ssu

re L

oa

din

g R

ate

- G

Pa

/s

Perforating Gun - 1,258 - 1,260m

0 5 10 15 20 25 30

Time - milliseconds

49

Laboratory Test Examples

Propellant Explosive

Summary

• Traditional “Big Hole” charges

– Yield a tunnel approximately 7 - 8“

long by 0.5 - 1.5 inches in diameter.

– Tunnel volume can be as much as 42

ci

– All total ~5 lbs of damaged material is

present in the tunnel and well mixed

• Lower explosive load charges reduced damage (29 ci)

• Minimal Penetrator Design - KISSTM charges

– 7 ci of damage, near the front face

Conclusions

• Our current approaches can be improved

– low injectivity, low productivity, perf

breakdown

• Re-think Conventional Big Hole Charges

– Large volumes of formation rock is

damaged

– Perforating through cement is not difficult

– Kiss Charge strategy is worth consideration

• Will not be effective alone

• Use Propellant to insure connection

• StimGunTM Assembly:

– Perf Breakdown: ~95% success

– Stand-alone near wellbore stimulation: ~

45% success

Vannguns

Vanngun Systems 1 9/16” to 7”

4 SPF to 18 SPF

7.00”

6.00”

5.125”

4.00”

3.375”

2.75”

2.00”

1.562”

CN02311

5.00”

4.625”

3.125”

2.50”

Vanngun Phasing 0° PHASING

1 ROW OF HOLES

140/160° PHASING

4 ROWS OF HOLES

60° PHASING

6 ROWS OF HOLES

45° PHASING

8 ROWS OF HOLES

72° PHASING

5 ROWS OF HOLES

30° PHASING

12 ROWS OF HOLES

90° PHASING

4 ROWS OF HOLES

180° PHASING

2 ROWS OF HOLES

51.4° PHASING

7 ROWS OF HOLES

60° PHASING

2 ROWS OF HOLES

CN02310

3.125” & 3.375” 12 SPF Omni

GROOVED TANDEM

CONNECTOR

CHARGE HOLDER TUBE

SHAPED CHARGE

SCALLOPED GUN BODY

XHV PRIMACORD

BOX & PIN CONNECTOR

POLYMER ALIGNMENT INSERT

BI-DIRECTIONAL BOOSTER

CN02452

4.625” 12 SPF Omni Super

Hole GROOVED

TANDEM

CONNECTOR

SHAPED

CHARGES

SCALLOPED GUN

BODY

XHV PRIMACORD

BOX & PIN

CONNECTOR

CN02451

POLYMER ALIGNMENT

INSERT

BI-DIRECTIONAL

BOOSTER

CHARGE

HOLDER TUBE

4.625” 18 SPF 45Þ/135Þ Phasing

GROOVED TANDEM

CONNECTOR

CHARGE

HOLDER TUBE

SHAPED CHARGE

SCALLOPED

GUN BODY

XHV PRIMACORD

POLYMER

ALIGNMENT INSERT

BI-DIRECTIONAL

BOOSTER

BOX & PIN CONNECTOR

CN02468

FracPac™SuperHole™

VannGun® Assembly

CN03150

GROOVED TANDEM

CONNECTOR

SHAPED CHARGES

SCALLOPED GUN BODY

XHV PRIMACORD

BOX & PIN CONNECTOR

4.625” 11 SPF 140°/160° Low Side Phasing

CN02287

GROOVED TANDEM CONNECTOR

SHAPED CHARGES

SCALLOPED GUN BODY

XHV PRIMACORD

BOX & PIN CONNECTOR

6.00” 12 SPF 51.4° Phasing

CN02286

GROOVED TANDEM

CONNECTOR

SHAPED CHARGES

SCALLOPED GUN BODY

XHV PRIMACORD

BOX & PIN CONNECTOR

7.00” 12 SPF

72° Phasing

CN02285

GROOVED TANDEM CONNECTOR

SHAPED CHARGES

SCALLOPED GUN BODY

XHV PRIMACORD

BOX & PIN CONNECTOR