Perforating Requirements New

For Fracturing Stimulations

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Perforating Requirements

Perforations •  Communication between the welbore and the reservoir

•  Should minimize the near-wellbore pressure drops due to perforation friction, micro-annulus pinch points, multiple competing fractures and fracture turtuosity.

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•  In a fractured-stimulated wellbore, is the conduit between the fracture and the wellbore

Micro-annulus pinch points (SPE 30506) Schlumberger Private

Near-wellbore fracture turtuosity (SPE 30506) Schlumberger Private

Underbalance perforating   Insufficient underbalance does not remove all sand debris from the   This debris creates an external “filter cake” in the perforation during the injection.

  High pressure drops can be expected.

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perforations.

Micro-annulus Perforating can create micro-annulus Schlumberger Private

(SPE 59480)

Micro-annulus width due to perforating

width (in) Poisson ratio Micro-annulus pressure (psi) Reservoir pressure (psi) well diameter (in) Young modulus (psi)

For, dw = 8-1/2-in, Pm-PR = 2000 psi ν=0.25, E = 1E06 psi w = 0.0106-in which, for a fluid velocity of 3.28 ft/s corresponds to a rate of 99 bpd (for a viscosity of 1 cp)

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w ν Pm PR dw E

Hard-rock hydraulic fracturing (I) (no micro-annulus, vertical wells)

  Dry gas wells, no liquid in wellbore,

Preferred Fractured Plan

75º, → short clusters (less than 3 ft, multiple phases angles).

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Perforated interval PFP PFP well

well 10 ft

100 ft 6º

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middle of the interval multiple factures induced decreased width

Penetration depth   4 to 6 inches into the formation (maximum).

  In practice, hole should be > 10 to times the larger proppant diameter.

  Large stress contrast favor 60º phase.

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  In theory, hole should be > 6 times proppant diameter.

Shots and hole size   Pressure drop is a function of the injection rate per perforation and

     

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viscosity of the fracturing fluid. During the treatment, hole size increases due to erosion by the fluid and, mainly, by the proppant. For 0º and 180º phases, all the holes contribute to the fracture. For 120º, only two-thirds contribute to the fracture and for 60º only one-third is connected. Pressure drop across perforations should be less than 25 psi.