Underbalanced perforation characteristics as affected by differential pressure
Underbalanced, tubing-conveyed completions are increasing because of the apparent advantages of cleaner perforations, reduced completion times, and stimulation treatments. Radial-flow Berea sandstone core specimens are used to determine the perforation characteristics resulting from time-dependent pressure differentials between core pressure and wellbore pressure during the completion process. The primary perforation characteristic studied (radial flow ratio (RFR)) is defined as the ratio of the perforated flow rate to the flow rate of the unperforated core. The perforation flow tests included pressure differentials from 500 psi (3450 kPa) overbalanced to 1,000 psi (6900 kPa) underbalanced, with immediate or delayed surging. The RFR was affected most by the 500-psi and 1,000-psi (3450- and 6900-kPa) underbalance. The surged RFR's were from 50 to 58% greater than the no-surge RFR's. Perforation hole volumes were increased as much as 55% by the surge, indicating some elimination of the compacted, damaged-zone material. Underbalanced surge conditions (1,000 psi (6900 kPa)) increased hole volume to four times that resulting from 500 psi (3450 kPa) overbalanced, no-surge conditions. Underbalanced surging, either at the instant of perforation or subsequently, appears to improve the flow characteristics of shaped-charge perforations by simultaneously reducing the thickness of the low-permeability crushed zone and increasing the perforation surface area.
- Research Organization:
- Jet Research Center Inc. (US)
- OSTI ID:
- 7041204
- Journal Information:
- SPE (Society of Petroleum Engineers) Product. Eng.; (United States), Vol. 3:1
- Country of Publication:
- United States
- Language:
- English
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