1. E EFFECTS OF PERFORATING ON H
WELL PERFORMANCE:
WILMINGTON OIL FIELD CASE ST
PresentedBy
Michael Okuneye
In Partial Fulfillment of the Requirements for Degree o1
3. OBJECTIVES
• Investigate the effects of selective perforating
on horizontal well performance
• To identify suitable and simple method in
modeling perforated horizontal well
performance
• To investigate how perforation parameters
affects horizontal well productivity
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4. WHY DO WE NEED PERFORATION?
• Establish communication between the
wellbore & the formation.
• This is achieved by making holes through the
casing, cement & into formation.
• The inflow capacity of the reservoir must not
be inhibited.
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5. BACKGROUND
• Well Productivity & Injectivity depends
primarily on near wellbore pressure drop
called Skin
• Skin is a function of:
Completion type
Formation damage
Perforation
• Skin is high & productivity reduced when:
Formation damage is severe (drilling & completion fluids
invasion ranges from several inches to a few feet)
Perforations do not extend beyond the invaded zone.
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7. Shaped charged perforation
• The shaped charge evolved from the WW2
military bazooka.
• Perforating charges consist of:
A primer
Outer case
High explosive
Conical liner connected to a detonating cord.
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9. 9
• The detonating cord initiates the primer &
detonates the main explosive
• The liner collapses to form the high-velocity jet
of fluidized metal particles that are propelled
along the charge axis through the well casing &
cement & into the formation.
• The detonator is triggered by:
Electrical heating when deployed on wireline
systems or,
A firing pin in mechanically or hydraulically
operated firing head systems employed on
tubing conveyed perforating (TCP) systems
10. • The jet penetrating mechanism is one of
“punching” rather than blasting, burning,
drilling or abrasive wearing.
• This punching effect is achieved by extremely
high impact pressures –
3 x 106 psi on casing
3 x 105 psi on formation.
• These jet impact pressures cause steel, cement,
rock, & pore fluids to flow plastically outward.
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13. EXPLOSIVES
• Explosives used in perforation are called
Secondary high explosives.
Reaction rate = 22,966 – 30,000 ft/s.
Volume of gas produced = 750 – 1,000 times original
volume of explosive.
• These explosives are generally organic compounds
of nitrogen & oxygen.
• When a detonator initiates the breaking of the
molecules' atomic bonds, the atoms of nitrogen
lock together with much stronger bonds, releasing
tremendous amounts of energy. 13
15. • RDX is the most commonly used explosives
• In deep wells when extreme temperature is required &
where the guns are exposed to well temperatures for
longer periods of time HMX, PS, HNS or PYX is used.
• It is important to respect the explosives used in
perforating operations.
• They are hazardous.
• Accidents can occur if they are not handled carefully or
if proper procedures are not followed.
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16. Perforating guns/ Methods
• Perforating guns are configured in several
ways.
• There are four main types of perforating guns:
Wireline conveyed casing guns
Through-tubing hollow carrier guns
Through-tubing strip guns
Tubing conveyed perforating guns
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19. Through-tubing Strip Guns
• Semi-expendable
type guns consisting
of a metal strip into
which the charges
are mounted.
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20. Tubing Conveyed Perforating Guns
(TCP)
TCP guns are a variant
of the casing gun
which can be run on
tubing.
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21. WELL/RESERVOIR CHARACTERISTICS
• Pressure differential between a wellbore and
reservoir before perforating can be described
by:
Underbalanced
Overbalanced
Extreme overbalanced (EOB)
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22. Underbalanced Perforating
• Reservoir pressure is substantially higher than
the wellbore pressure.
• Adequate reservoir pressure must exist to
displace the fluids from within the production
tubing if the well is to flow unaided.
• If the reservoir pressure is insufficient to
achieve this, measures must be taken to
lighten the fluid column typically by gas lifting
or circulating a less dense fluid.
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24. Overbalanced Perforating
• Perforating when the wellbore pressure is
higher than the reservoir pressure.
• This is normally used as a method of well
control during perforating.
• The problem with this method is it introduces
wellbore fluid into the formation causing
formation damage.
• Use clean fluid to prevent perforation
plugging.
• Use of acid in carbonates.
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27. Extreme Overbalanced Perforating
• The wellbore is pressured up to very high
pressures with gas (usually nitrogen).
• When the perforating guns are detonated the
inflow of high pressure gas into the formation
results in a mini-frac, opening up the
formation to increase inflow.
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28. CALCULATIONS
• A mechanism to account for the effects of
perforations on well performance is through
the introduction of the perforation skin effect,
sp in the well production equation.
• For example, under steady-state conditions:
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141.2 ln
e wf
e
p
w
kh P P
q
r
B s
r
29. • Karakas and Tariq (1988) have presented a semi-
analytical solution for the calculation of the
perforation skin effect, which they divide into
components:
The plane-flow effect, sH
The vertical converging effect, sV
The wellbore effect, swb
• The total perforation skin effect is then:
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p H V wbs s s s
33. • a1, a2, b1 & b2 are obtained from the table
above.
• kH = horizontal permeability
• kV = vertical permeability
• rperf = radius of perforation (ft)
• sV is potentially the largest contributor to sp.
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34. The Wellbore Effect
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• c1 & c2 are obtained from the table above.
1 2expwb wDs c c r
w
wD
perf w
r
r
l r
38. References
• Gatlin, C.: “Drilling Well Completion,” Prentice-
Hall Inc., New Jersey, 1960.
• ENI S.p.A. Agip Division: “Completion Design
Manual,” 1999.
• Halliburton: “Petroleum Well Construction,”
1997.
• Ott, W. K. and Woods, J. D.: “Modern Sandface
Completion Practices Handbook,” 1st Ed.,
World Oil Magazine, 2003.
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39. 39
Schlumberger: “Completions Primer,” 2001.
Golan, M. and Whitson, C. H.: “Well Performance,”
2nd Ed., Tapir, 1995.
Karakas, M. and Tariq, S.: “Semi-Analytical
Productivity Models for Perforated Completions,”
paper SPE 18271, 1988.
Clegg, J. D.: “Production Operations Engineering,”
Petroleum Engineering Handbook, Vol. IV, SPE,
2007.
Bellarby, J.: “Well Completion Design,” 1st Ed.,
Elsevier B.V., 2009.
40. FUTURE WORK/RECOMMENDATION
• 4-Dimensional space should be explored to better
improve the 3-Dimensional projection of complex
grid geometry in the structure of the reservoir.
• Future reservoir simulation can also be carried
out using the integrated 3-Dimensional reservoir
model results for history matching and sensitivity
analysis for effective well performance.
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41. REFERENCES
• Gatlin, C.: “Drilling Well Completion,” Prentice-
Hall Inc., New Jersey, 1960.
• ENI S.p.A. Agip Division: “Completion Design
Manual,” 1999.
• Halliburton: “Petroleum Well Construction,”
1997.
• Ott, W. K. and Woods, J. D.: “Modern Sandface
Completion Practices Handbook,” 1st Ed.,
World Oil Magazine, 2003.
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42. • Schlumberger: “Completions Primer,” 2001.
• Golan, M. and Whitson, C. H.: “Well
Performance,” 2nd Ed., Tapir, 1995.
• Karakas, M. and Tariq, S.: “Semi-Analytical
Productivity Models for Perforated
Completions,” paper SPE 18271, 1988.
• Clegg, J. D.: “Production Operations
Engineering,” Petroleum Engineering Handbook,
Vol. IV, SPE, 2007.
• Bellarby, J.: “Well Completion Design,” 1st Ed.,
Elsevier B.V., 2009.
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