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Underbalanced Perforating. Underbalanced Perforating. Early tests by Exxon showed that flow patterns and perforation geometry prevent the cleaning out of an appreciable percentage of mud-or silt-plugged perforations by simple production from a well - PowerPoint PPT Presentation
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Underbalanced Perforating
Underbalanced Perforating Early tests by Exxon showed that flow
patterns and perforation geometry prevent the cleaning out of an appreciable percentage of mud-or silt-plugged perforations by simple production from a well
Published studies of the flow rate necessary to remove damage observed that serious perforation plugging occurred whenever the pressure was higher in the wellbore than in the formation
Early tests by Exxon showed that flow patterns and perforation geometry prevent the cleaning out of an appreciable percentage of mud-or silt-plugged perforations by simple production from a well
Published studies of the flow rate necessary to remove damage observed that serious perforation plugging occurred whenever the pressure was higher in the wellbore than in the formation
Underbalanced Perforating
Plugs that formed when perforating in heavy mud were almost impossible to remove by reversing pressure.
"Permanent plugging of a high percentage of perforations may result from killing a well with mud or dirty fluid during well completion, servicing, or workover."
"When perforating in mud with a pressure differential into the formation, perforations are filled with mud solids, charge debris, and formation particles." Not easily removed.
Plugs that formed when perforating in heavy mud were almost impossible to remove by reversing pressure.
"Permanent plugging of a high percentage of perforations may result from killing a well with mud or dirty fluid during well completion, servicing, or workover."
"When perforating in mud with a pressure differential into the formation, perforations are filled with mud solids, charge debris, and formation particles." Not easily removed.
Underbalanced Perforating
Differential pressure required to initiate flow through each plugged perforation, varies.
When a few perforations requiring low differential pressures open up, flow into these perforations makes it difficult to create the higher pressure drawdown needed to open additional perforations.
“Crushed and compacted rock around the perforation has essentially zero permeability and further reduces the probability of perforation cleanout.”
Differential pressure required to initiate flow through each plugged perforation, varies.
When a few perforations requiring low differential pressures open up, flow into these perforations makes it difficult to create the higher pressure drawdown needed to open additional perforations.
“Crushed and compacted rock around the perforation has essentially zero permeability and further reduces the probability of perforation cleanout.”
Underbalanced Perforating
The post-shot flow into the wellbore (a function of the formation-wellbore pressure differential, the formation fluid viscosity and the formation permeability) helps remove the crushed formation from the perforation and provides improved flow channels.
High post-shot formation to wellbore flow generally provides optimum perforation cleanup and minimum skin.
The post-shot flow into the wellbore (a function of the formation-wellbore pressure differential, the formation fluid viscosity and the formation permeability) helps remove the crushed formation from the perforation and provides improved flow channels.
High post-shot formation to wellbore flow generally provides optimum perforation cleanup and minimum skin.
Underbalanced Perforating
Underbalance perforating followed by flow has been shown to be the best method for cleaning perforations and establishing high flow capacity from natural completions in moderate to high permeability core
Even when compared to surging and washing, underbalance perforating followed by flow can be superior
Underbalance perforating followed by flow has been shown to be the best method for cleaning perforations and establishing high flow capacity from natural completions in moderate to high permeability core
Even when compared to surging and washing, underbalance perforating followed by flow can be superior
The Level of Underbalance
Must balance perforation cleanup and well performance potential enhancement against the downside aspects of mechanical problems such as perforators or wireline sticking in the wellbore, near-wellbore rock formation disintegration, downhole tubulars and equipment damage, etc.
Must balance perforation cleanup and well performance potential enhancement against the downside aspects of mechanical problems such as perforators or wireline sticking in the wellbore, near-wellbore rock formation disintegration, downhole tubulars and equipment damage, etc.
The Level of Underbalance
The pressure differentials necessary to achieve the flow rates required to remove perforation and/formation-skin damage are affected by:
Formation pressure
Reservoir permeability
Perhaps limited by formation integrity
Usually range from approximately 500 psi to over 5000 psi
Have been established by trial and error in many fields
The pressure differentials necessary to achieve the flow rates required to remove perforation and/formation-skin damage are affected by:
Formation pressure
Reservoir permeability
Perhaps limited by formation integrity
Usually range from approximately 500 psi to over 5000 psi
Have been established by trial and error in many fields
Implementation
Downhole and surface mechanical equipment to achieve desired underbalance and maintain the integrity of the well
Control the well during deployment, perforating and retrieval,
Deploying the perforating device(s) to the proper downhole position,
Activating the perforating mechanisms, Monitoring the downhole perforating process, Retrieving the perforating system
Downhole and surface mechanical equipment to achieve desired underbalance and maintain the integrity of the well
Control the well during deployment, perforating and retrieval,
Deploying the perforating device(s) to the proper downhole position,
Activating the perforating mechanisms, Monitoring the downhole perforating process, Retrieving the perforating system
Precautions!
It is more costly to employ than conventional perforating.
Safety and well control is a primary issue. It requires the appropriate combination of
reservoir pressure, reservoir fluid properties and formation permeability to achieve the required underbalance for effective application.
Prospects must be thoroughly screened, and there are those that may not be, or are not, appropriate candidates.
It is more costly to employ than conventional perforating.
Safety and well control is a primary issue. It requires the appropriate combination of
reservoir pressure, reservoir fluid properties and formation permeability to achieve the required underbalance for effective application.
Prospects must be thoroughly screened, and there are those that may not be, or are not, appropriate candidates.
Jet PerforatingFormation Properties
Compressive strength, effective stress and specific rock characteristics can have significant impact
In unstressed rock, penetration decreases with increasing compressive strength
Pore fluid compressibility affects performance. Increasing liquid saturation improves
penetration Stress reduces penetration (other factors
being kept constant)
Compressive strength, effective stress and specific rock characteristics can have significant impact
In unstressed rock, penetration decreases with increasing compressive strength
Pore fluid compressibility affects performance. Increasing liquid saturation improves
penetration Stress reduces penetration (other factors
being kept constant)
Jet PerforatingFormation Properties
Effective Stress (ksi)
Pen
etr
ati
on
M
ult
iplie
r
Design
Perforator Type, Charge Strength and Gun Clearance
Conveyance Logistics, Surface and Downhole Equipment/Apparatus
Existing Wellbore Tubular/Cement-Sheath Limitations
Perforator Type, Charge Strength and Gun Clearance
Conveyance Logistics, Surface and Downhole Equipment/Apparatus
Existing Wellbore Tubular/Cement-Sheath Limitations
Design
Formation Mechanical Rock Properties and Characteristics
Reservoir Pressure and Fluid Flow Characteristics
Perforating Downhole Environment Conditions/Limitations
Formation Mechanical Rock Properties and Characteristics
Reservoir Pressure and Fluid Flow Characteristics
Perforating Downhole Environment Conditions/Limitations
Design (King’s Method)
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 500 1000 1500 2000 2500 3000 3500
Underbalance Pressure (psi)
Perf
ora
ting S
kin (
dim
ensi
onle
ss)
Gold SandstoneBerea Sandstone
Hsia and BehrmannHsia and Behrmann
1.0E-01
1.0E+00
1.0E+01
1.0E+02
1.0E+03
1.0E+04
1.0E-04 1.0E-03 1.0E-02 1.0E-01 1.0E+00 1.0E+01
Reynolds' Number (dimensionless)
Fric
tion F
act
or
(dim
ensi
onle
ss)
Laminar FlowDarcy's Law ValidDrag Not Enough
for Cleanup
Non-linear Laminar FlowDarcy's Law Invalid
Drag Enough for Cleanup
Turbulent Flow
TariqTariq
Cleanup Criterion Based on Reynolds Number
perfc
2c
2o
7
perf
cc
cperfi r
1r1
rv10244.1rr
lnrkv
94815pp
vk1031735.1N 12
Re
cperfcRe
perf
c
o2
c
cRe216
r1
r1
rNrr
lnk
rN101974.7p
Design
Of the factors influencing the determination of correct underbalance
for cleanup the fluid properties, especially viscosity, are important but
the key factor is the formation permeability
Of the factors influencing the determination of correct underbalance
for cleanup the fluid properties, especially viscosity, are important but
the key factor is the formation permeability
Efficiency
The major factors affecting the efficiency of a perforation include shot density (spf), penetration depth into the formation, angular phasing, and diameter
Injectivity increases as shot density increases?
Injectivity increases with increases in perforation penetration?
The effect is greater at shallow depths.
The major factors affecting the efficiency of a perforation include shot density (spf), penetration depth into the formation, angular phasing, and diameter
Injectivity increases as shot density increases?
Injectivity increases with increases in perforation penetration?
The effect is greater at shallow depths.
EfficiencyAngular phasing other than 0° increases injectivity
by reducing the interference with flow resulting from the presence of the wellbore.
Perforation diameter plays a relatively minor role in determining injectivity?
The strength, in-situ stress conditions and lithology can effect the penetration length, the extent and severity of the damage zone around the perforation, and the cleanup characteristics.
Angular phasing other than 0° increases injectivity by reducing the interference with flow resulting from the presence of the wellbore.
Perforation diameter plays a relatively minor role in determining injectivity?
The strength, in-situ stress conditions and lithology can effect the penetration length, the extent and severity of the damage zone around the perforation, and the cleanup characteristics.
Modular Gun System
Deployment systems for multiple guns.
Guns are loaded at the surface, deployed downhole individually, and stacked on each other at the perforating zone, with the lower-most gun module being supported by the gun hanger.
Deployment systems for multiple guns.
Guns are loaded at the surface, deployed downhole individually, and stacked on each other at the perforating zone, with the lower-most gun module being supported by the gun hanger.
Modular Gun System
An entire interval can be perforated over- or underbalanced
Gun sizes from 2 to 7-inch OD can be run for casing from 3 ½ to 8 5/8 inches,
Zone can be perforated and tested with no downhole restrictions below or above the packer.
An entire interval can be perforated over- or underbalanced
Gun sizes from 2 to 7-inch OD can be run for casing from 3 ½ to 8 5/8 inches,
Zone can be perforated and tested with no downhole restrictions below or above the packer.