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Water hammer dissipation in pneumatic slug tests
Author(s) -
Ostendorf David W.,
DeGroot Don J.,
Dunaj Philip J.
Publication year - 2007
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2005wr004817
Subject(s) - casing , slug test , geotechnical engineering , aquifer , dissipation , water hammer , mechanics , elasticity (physics) , geology , pore water pressure , materials science , groundwater , petroleum engineering , composite material , physics , thermodynamics
We model and measure the dissipation of water hammer induced by well casing and water elasticity with rapid valve opening at the start of a pneumatic slug test. The higher‐frequency water hammer can obscure slower, aquifer‐controlled, underdamped oscillations of the rigid water column, so a quantitative description of the elastic motion improves the ability of a slug test to calibrate the aquifer permeability k . Internal friction attenuates the water hammer, subject to a known headspace pressure at the air/water interface and equilibrium pressure at the top of the well screen. An analytical elastic solution is presented and matched to an existing rigid motion analysis, with matching predicated on k exceeding 7 × 10 −14 m 2 and appreciable water hammer dissipation during the first cycle of the slug test. The model is accurately calibrated with data from underdamped slug tests in a PVC monitoring well in the Plymouth‐Carver Aquifer. The calibrated casing elasticity value suggests that effective lateral soil stress appreciably stiffened the casing.