Post on 12-Apr-2016
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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.
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
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.
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.
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
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.
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
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
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
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