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• Since the pay zone is sealed off by the production casing and cement, perforations must be made in order for oil or gas to flow into the wellbore.
• Perforating incorporates shaped-charge explosives which creating a jet of high-pressure, high-velocity gas.
• It can be overbalance or underbalance perforation, and wireline conveyed perforation (WCP) or tubing conveyed perforation (TCP).
PERFORATION
4
• Perforating gun (WCP type) is lowered into the hole at the depth where the oil or gas formation is found (A).
• After the gun is lined up properly, powerful explosive charges are fired (B) from the control panel at the surface. These explosives blast a hole in the steel casing and cement, up to several feet out into the rock.
• Finally, the oil and gas fluids flow into the holes and up the well to the surface (C).
Perforating History
•Mechanical, prior to 1932
•Bullet Gun, 1932 to present
•Hydraulic, 1958 to present
- Abrasive jetting
•Shaped Charge, 1946 to present- Most popular
Types of Perforators
• Bullet Perforators
• Hydraulic Perforators
• Mechanical Perforators
• Jet Perforators
• Perforation using laser technology
BULLET GUN PERFORATOR
GUN GUN
CEMENT
CASING
INWARD BULGING JUST
ABOVE AND BELOW
PERFORATION
(A)
SOFT ROCK
(B)
HARD ROCK
Bullet guns were the technique of choice until the jet (shaped
charge) perforator was developed in the 1950’s. Most bullet
guns were manufactured 3 1/4 inch outside diameter or larger
and were effective in penetrating materials with 600 psi
compressive strength and lower.
Bullet Perforation
• Bullets lose velocity when gun clearance > 0.5 in.
• Often use in a unconsolidated formations
• Cheaper to use, rarely been used today
• Bullets plug the end of the flow channel
(A) - HYDRAULIC (B) - MECHANICAL
Hydraulic: Sand laden
fluid is pumped
through a tubing
installed jet and holes
are horizontally cut
out of the formation
Mechanical Perforator:Mechanical perforators are circular cutters which
have been devised to cut through the casing into
the target material. The application of mechanical
cutters has been limited to the initiation of
horizontal fractures or other specific operations.
• Wireline
conveyed
perforating (WCP)- Wireline casing
perforating
- Thru Tubing
perforating (TTP)
• Tubing conveyed
perforating (TCP)
Perforating Techniques
Tubing-
Conveyed
Gun
Wireline
Casing Gun Through-
Tubing
Gun
Perforating Guns
• A device used to perforate oil and gas wells in preparation for production.
• It has different shapes of explosive charges.
• Different range of sizes and configurations.
• The diameter of the gun used is determined by the presence of wellbore restrictions or limitations imposed by the surface equipment.
• Create holes in a casing string.
• Casing guns are typically 3 to 5-in. in diameter and carry up to four perforating charges per foot (shot per foot (spf))
• Allow perforation through production casing using larger diameter gun assembly.
Wireline Casing gun
• It is retrievable from the wellbore after firing.
• It generates minimal debris
• Minimum distortion of the gun body to help ensure easy retrieval.
Retrievable gun
THRU’ TUBING GUN• Expendable gun: A perforating gun
assembly that disintegrates upon firing, thereby reducing the volume and dimensions of retrieved components.
• Expendable guns are typically used
where wellbore restrictions allow only limited access, as in through-tubingapplications. The distortion caused to the gun assembly during firing would typically prevent recovery of a conventional gun design through the limited clearances.
• The expendable gun assembly breaks
into small pieces that drop to the bottom of
the well (?) , leaving only a relatively small
subassembly that is easily recovered to surface.
SEE
DETAILED
SECTION
PRODUCING
INTERVAL
WELL
REMOTE
CONTROLLED
WELL HEAD
GOOSENECK - 5ft
RADIUS
SEA SURFACE
FLOATING GATHERING
PLATFORM
TWO FLOW LINES
(UP T0 7000 - 8000 ft
IN GULF COAST)
SEA FLOOR
PRODUCTION
TUBING
BATTERY CARRIER
PACKER
"NO-GO" NIPPLE
CONTROL HEADS
7" CASING
GUN POSITIONER
PRODUCING INTERVAL
GUN
CIRCULATING PORT
CIRCULATING STRING
DETAILED SECTION
Semi and fully expendable guns are run through tubing due
their flexibility.
TUBING CONVEYED PERFORATING (TCP)
The use of tubing, drillpipe or coiled tubingto convey perforating guns to the required depth.
Assuming we have 2 gravel packs in the well. It will look something like this
Top packer
Bottom packer
Screens
Seal bore
Top packer
Bottom packer
Liner &Screens
Seal bore
If we want to produce through the bottom zone, we will close the sliding side door so that hydrocarbons from the top zone does not enter the production string
Seal bore
Hydraulic packer
Sliding side door
Seals Assembly
No Go Nipple
Bullet Perforators
Hydraulic Perforators
Mechanical Perforators
Laser
Jet Perforators
(A) - HYDRAULIC (B) - MECHANICAL
GUN GUN
CEMENT
CASING
INWARD BULGING JUST
ABOVE AND BELOW
PERFORATION
(A)
SOFT ROCK
(B)
HARD ROCK
Perforating with Laser
• Conventional explosive charge perforation method reduces the rock permeability
• Laser perforation increase the rock permeability, hence, increase the oil or gas production rate of a well.
Jet Perforation
• It uses a shaped charges contained in a perforating gun assembly.
• Gun assembly is placed in wireline, tubing or coiled tubing, depending on the application and the wellbore conditions.
• High-pressure jet will penetrates the casing or liner to shoot into the reservoir formation to form channels.
Jet Perforation: Shaped Charge
MAIN EXPLOSIVE
CHARGE
PRIMER CHARGE
CASE or CONTAINER
LINER
DETONATION CORD
GROOVE - POINT OF
INITIATION
PORT PLUG
AIR CUSHION STEEL CARRIER ELECTRONIC DETONATOR
MAIN CHARGE PRIMER
SHAPED CHARGE
ASSEMBLYDETONATING CHORD
Jet Perforating Process
•High velocity -7,000 m/sec
•High Pressure -millions psi
•High speed -microseconds
•Particulated jet does the work
SHAPED CHARGE
SLUG
JET
V1
1"16
0.5"P1
PRESSURE ON TARGET P1 = 5 x 106 PSI
VELOCITY OF FORWARD JET V1 = 20,000 FT/SEC
PARAMETERS AFFECTING SHAPED CHARGE PERFORMANCE
a d
a
b
PENETRATIONSTANDOFF
ENTRY
HOLE
TARGET
SHAPED CHARGE
p
DV
t
LC
c
VOLUME
Industry Testing of Perforating Systems
1000 PSI
CORE PRESSURE
1200 PSI
CORE PRESSURE
(KEROSENE FLOW)
CEMENT
BEREA SANDSTONESTAINLESS STEEL
CANISTER
DP = 500 PSI
DP = 200 PSI
SALT WATER
ESTABLISH:
1500-PSI WELL
PRESSURE
(9.6 PPG SALT WATER)
PERFORATE & INFILTER:
1500-PSI WELL PRESSURE
BACKFLOW TO STABILIZATION:
1000-PSI WELL PRESSURE
KEROSENE VISCOSITY mo
Lo
DPo
AREA , Ao
Qo
HASSLER UNITBEREA CORE
QP
DP = 200 PSI
CORE OF CROSS SECTIONAL AREA
"A" MOUNTED IN CANNISTER,
PERFORATED AND KEROSENE
FLOWED, VISCOSITY mPi
P
oi
oP
Po
PPPP
oo
oooo
k
k
kk
kkCFE
PA
LQk
PA
LQk
==
D
m=
D
m=
DETERMINE ORIGINAL ko:
CALCULATE PERFORATION
kP FROM TEST:
CALCULATE CORE FLOW
EFFICIENCY:
ki/k
o REPRESENTS THE RATIO OF THE EFFECTIVE
PERMEABILITY OF A TARGET CONTAINING AN IDEAL
(DRILLED) PERFORATION (OF THE SAME DEPTH &
DIAMETER AS THE PERFORATED ONE) TO THE ORIGINAL
TARGET PERMEABILITY ko
Industry Testing of Perforating Systems
• Major effects
– Gun clearance
– Casing and formation strength
– Effective formation stress
– Wellbore Fluid
– Temperature (selection of explosive)
Downhole Parameters That Affect Performance
Problem with Perforation
• The main problem is the plugging after Perforation, these caused by:–Charge liner residue slugs
–Mud solids & crushed/compacted rock particles
• Solution to the problem: Cleanout of Plugged Perforations, these include:–Back surge perforations if consolidated
formations
–Use ‘wash tools’ if unconsolidated formations
–Breakdown with fluid or acid, and ball sealers
VARIABLE
CLEARANCE
1 11/16"
GUN
1 11/16"
GUN
CONTROLLED
CLEARANCE
7" DIAMETER CASING
MULTI DIRECTIONAL POSITIONED
Gun Clearance
CONCLUSIONS
• Different perforation guns have specific application. Examples: casing gun, retrievable gun, high-shot density gun, & expendable gun.
• Methods of perforation, these include: Bullet, Jet, hydraulic, & laser.
• Problems from perforating operations should be overcome.