Perforation Cleanup by Dynamic Underbalance

Clinton Quattlebaum, G. G. Craddock, Dennis HaggertyCraddock, Dennis Haggerty

Jet Research CenterAlvarado, Texas

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Dynamic Underbalance

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Selected DUB Bibliography

Terry Walker, et.al., “Maximum Differential Pressure Perforating,” 1969: One of the earliest Halliburton papers discussing DUB - SPE 2648

G E. King, et. Al., “A Field Study of Underbalance Pressures Necessary to Obtain Clean Perforations Using Tube-Conveyed Perforating,” 1986: Seminal presentation of DUB case studiesPerforations Using Tube Conveyed Perforating, 1986: Seminal presentation of DUB case studies and optimum underbalance

John A. Regalbuto and Robert S. Riggs, “Underbalanced Perforation Characteristics as Affected by Differential Pressure,” 1988: Defined metric of Perforated Flow Rate over Un-perforated Flow Rate and showed DUB improves flow characteristics

H. R. Crawford, “Underbalanced Perforating Design,” 1989: Provided design guidelines based on g g g gpressures for DUB using case histories

S. M. Tarig, “New, Generalized Criteria for Determining the Level of Underbalance for Obtaining Clean Perforations,” 1990: DUB requirements based on nonlinear flow equation. The required level of underbalance is when the nonlinear term in the flow equation becomes important. FEM suggest less strength at the tunnel tip.L A B h d B M D ld “U d b l E t O b l ” 1995 E t L. A. Behrmann and B. McDonald, “Underbalance or Extreme Overbalance,”: 1995: Extreme Overbalance is compared and contrasted with Underbalance. Best uses of each are drawn from case studies.

L. A. Behrmann, “Underbalance Criteria for Minimum Perforation Damage,” 1996: Set of underbalance equations are derived which have weak dependence on compressibility and viscosity These equations lead to an optimum underbalance condition different than King et Alviscosity. These equations lead to an optimum underbalance condition different than King, et. Al.

J. P Morris, et. Al., “Simulating Perforation Permeability Damage and Cleanup,” 2001: Permeability estimates based on hydrocode and equations derived for cleanup.

Russell L. Detwiler, et. Al., “Evaluation of the Relative Importance of Parameters Influencing Perforation Cleanup,” 2004: Continuation of above, with a more detailed model from the pressure surge right after perforation. The pressure is evolved diffusively. Noted experimental comparison g g p p y p pwas not so good.

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API 19B Section IV –Test Vessel

Simulated Formation

Simulated Wellbore

Gun Volume/Surge ChamberGun Volume/Surge Chamber

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Gun Volume – Dynamic Underbalance

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Gun Volume – Dynamic Underbalance

#11 #9

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Gun Volume – Dynamic Underbalance7

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Perforation Tunnel Fluid Velocity

0.000 0.020 0.040 0.060 0.080 0.100 0.120 0.140 0.160 0.180 0.200

11 Delta P ‐1 9 Delta P ‐1

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Gun Volume - Sensitivity

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Perforation Cleanup

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Alternative Modeling Direction

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Perforation Cavity

C h d 0 3 0 5

Bore Fluid

Crushed zone: 0.3 - 0.5 cm

Bore Fluid

Bore Fluid

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Mechanics of Perforation Cleanup

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Crushed Zone Thickness from CTH

.1 cm

.3 cm

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Perforation Cavity: Uniform Cleanup CasePerforation Cavity: Uniform Cleanup Case

Fluid Flow

Crushed zone material cleans up uniformly

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Uniform Cleanup Case

Kozeny-Carman model for flow in slab coordinates2 22 2d d

– time dependent crushed zone layer

2 2 2 23 1 3 1

s sd p d pv

p y– turbulent limiting– Solve time dependent equation for flow

Flow pressure must exceed tensile strength of layer for cleanup to occur

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Uniform Flow Model Flow from Measured Pressures

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Non-uniform Case

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Perforation Cavity: Non-uniform Fluid Jet CleanupPerforation Cavity: Non uniform Fluid Jet Cleanup

D

Aperture a

l

Fluid FlowFluid Jet

Aperture a

α

Fluid jet cleans up by eroding material close to aperture: FEM

δ

j p y g pSimulations have shown crushed zone is weakest at tip

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Fluid Jet Model

Jets are very unstable, laminar jets never exist, jets are turbulent

If mass flow out of aperture is and distance along axis is then inside jet

0Qx

DlQ -

1

02 2tan ( ) 2 cos( ) tan ( )

aperaturex

DluQua x ax

– Flow outside jet is: 1 1 cos( )2xout xu u

112.5 , 1 cos .11xu

Cleanup when fluid jet friction on perforation cavity walls exceeds crushed zone strength

,2 x

g

Note that best cleanup occurs for REF. -Fluid Mechanics by Landau and Lifshitz

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Conclusions

Based on laboratory tests, previous models are i d t i di ti DUB i d f f tiinadequate in predicting DUB required for perforation tunnel cleanup

Alternative velocity-weighted model offers promise of predicting the DUB pressure-time profile

Further laboratory testing coupled with physical understanding can identify best approach towardsunderstanding can identify best approach towards accurately quantifying DUB

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