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Water hammer dissipation in pneumatic slug tests

TitleWater hammer dissipation in pneumatic slug tests
Publication TypeJournal Article
Year of Publication2007
AuthorsOstendorf DW, Degroot DJ, Dunaj PJ
Volume43
Issue2
Start Page1
Pagination1-10
Date Published02/2007
Abstract

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 m2 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.

DOI10.1029/2005WR004817