Under Balance

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 CEMENT

CASING CLEARANCE VANNGUN

STANDOFF

CN03197

Vanngun Phasing 0° PHASING 1 ROW OF HOLES

180° PHASING 2 ROWS OF HOLES

90° PHASING 4 ROWS OF HOLES

60° PHASING 6 ROWS OF HOLES

60° PHASING 2 ROWS OF HOLES

140/160° PHASING 4 ROWS OF HOLES

45° PHASING 8 ROWS OF HOLES

51.4° PHASING 7 ROWS OF HOLES

30° PHASING 12 ROWS OF HOLES

72° PHASING 5 ROWS OF HOLES CN02310

Determining the Proper Underbalance

Productivity Ratio As A Function Of Penetration And Shot Density 1.3

Spiral 90 phased

1.2

1.1

1.0

4

90 phased

2

2 spf

1.0 1

180 phased 0.9

0 phased

0.8

.7

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

0.7

0

6

3

9

1

10 PERFORATION LENGTH INCHES

1

5

1 spf SHOTS PER FOOT

PRODUCTIVITY RATIO

1.2

12 spf 8 spf 6 spf 4 spf

1 28 6

18 CN03199

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 A. Sonic Log Shale = 100 ms/ft. or Less B. Density Log Shale = 2.4 gm/cc or More

5800

100 100 50 Microsec/Ft.

150

Unconsolidated Formation A. Sonic Log Shale = Greater than 100 ms/ft. B. Density Log Shale = Less than 2.4 gm/cc

5400

120 110 150

100

50

Microsec/Ft.

Underbalance Pressure Used On Tubing Conveyed Perforating In Oil Zones In Sandstone

FORMATION PERMEABILITY MD

1,000

100 100

10

10 l

1.0

.1

1

0.1

Legend

Acid improve Acid diddid not improve production production Acid did improve production Acid did not improve production

.01

100

1000

TOTAL UNDERBALANCE PSI

Courtesy - George King, SPE 14321

10,000

CN03202

Underbalance Pressure Used On Tubing Conveyed Perforating In Gas Zones In Sandstone 1,000100 0

FORMATION PERMEABILITY MD

100 100

l

Stuck Packer

10

10 Casing Collapse

1

1.0

.1

0.1

Legend Aciddid did not improve production Acid improve Acid did improve production Acid did not improve Problems Problem

0.01

100

1000

10000

TOTAL UNDERBALANCE PSI CN03203

VannSystems Chart-Density Data USING DENSITY DATA TO DETERMINE PERFORATING UNDERBALANCE PRESSURE BULK DENSITY OF ADJACENT SHALE - grams/cc.

170 180

1.80

1.90

2.00

Gas Sand 2.10

Oil Sand

2.20

2.30

2.40 0

250

500

750

1000 1250

1500

1750

2000

2250

MAXIMUM PRESS. UNDERBALANCE - PSI FOR UNCONSOLIDATED SANDS CN03204

2500

²T ADJACENT SHALE - MICROSECONDS PER FOOT

VannSystems Chart-Acoustic Data USING ACOUSTIC DATA TO DETERMINE PERFORATING UNDERBALANCE PRESSURE 170 170 160

150

140

130

Oil Sand

130

Gas Sand

120

110

90 100 0

250

500

750

1000 1250

1500 1750

2000

2250

MAXIMUM PRESS. UNDERBALANCE - PSI FOR UNCONSOLIDATED SANDS CN03205

2500

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 1md (gas) • Pub=2,500/k^.30 psi, for oil Maximum Underbalance from Adjacent Shale For DT > 90 mu s/ft. • P umax gas = 4,800-25(DT ), psi (gas) • P as max oil = 3,500-19(DT ), psi (oil) as

as

as

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 @ 1215 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

Darcy’s Law - Fluid Loss 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

Perf G - “Minimal Penetrator Design” 4.625 Gun System (KISS Charge) Cement Puncture TM

Imbedded Debris

Perf G - “Minimal Penetrator Design” 4.625 Gun System (KISS TM )

Charge) Perforation Tunnel

Perf D - 7” Aluminum Liner Charge Zero Clearance Perforation Tunnel

“Combination” Perf/Propellant Assembly

“StimGun ” Assembly TM

Conventional Perforating Carrier System

Modified Charge Designs

Outer Propellant Cylinder

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.

1000

Perforating Gun - 1,258 - 1,260m

Propellant vs. Perforating

Pressure Loading Rate - GPa/s

500

0

-500

-1000

200

Propellant - 1,258 - 1,260m

Pressure Loading Rate - GPa/s

150

100

50

0

-50

-100

-150

0

5

10

15

20

Time - milliseconds

25

30

Laboratory Test Examples Propellant

Explosive

49

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 • StimGun Assembly: TM

– 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” 5.00” 4.625”

4.00” 3.375” 3.125” 2.75” 2.50”

2.00” 1.562”

CN02311

Vanngun Phasing 0° PHASING 1 ROW OF HOLES

180° PHASING 2 ROWS OF HOLES

90° PHASING 4 ROWS OF HOLES

60° PHASING 6 ROWS OF HOLES

60° PHASING 2 ROWS OF HOLES

140/160° PHASING 4 ROWS OF HOLES

45° PHASING 8 ROWS OF HOLES

51.4° PHASING 7 ROWS OF HOLES

30° PHASING 12 ROWS OF HOLES

72° PHASING 5 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

GROOVED TANDEM CONNECTOR

4.625” 12 SPF Omni Super Hole

CHARGE HOLDER TUBE

SHAPED CHARGES SCALLOPED GUN BODY

XHV PRIMACORD

BOX & PIN CONNECTOR

POLYMER ALIGNMENT INSERT BI-DIRECTIONAL BOOSTER CN02451

4.625” 18 SPF 45Þ/135Þ Phasing

GROOVED TANDEM CONNECTOR

CHARGE HOLDER TUBE

SHAPED CHARGE

SCALLOPED GUN BODY

XHV PRIMACORD

BOX & PIN CONNECTOR

POLYMER ALIGNMENT INSERT BI-DIRECTIONAL BOOSTER

CN02468

FracPac™SuperHole ™ VannGun® Assembly GROOVED TANDEM CONNECTOR

SHAPED CHARGES

SCALLOPED GUN BODY

XHV PRIMACORD

BOX & PIN CONNECTOR

CN03150

4.625” 11 SPF 140°/160° Low Side Phasing GROOVED TANDEM CONNECTOR

SHAPED CHARGES

SCALLOPED GUN BODY

XHV PRIMACORD

BOX & PIN CONNECTOR

CN02287

6.00” 12 SPF 51.4° Phasing GROOVED TANDEM CONNECTOR

SHAPED CHARGES

SCALLOPED GUN BODY

XHV PRIMACORD

BOX & PIN CONNECTOR

CN02286

7.00” 12 SPF 72° Phasing GROOVED TANDEM CONNECTOR

SHAPED CHARGES

SCALLOPED GUN BODY

XHV PRIMACORD

BOX & PIN CONNECTOR

CN02285