On conducting the modified ‘Slug’ test in tight formations

The method introduced by Bredehoeft and Papadopulos (1980) for conducting a modified ‘slug’ test in tight formations does not assure the condition of approximate equilibrium necessary at the start of the test. In addition, compressibility in the shut-in well can be significantly larger than the compressibility of water, which Bredehoeft and Papadopulos indicate should be used in the calculations. Errors that may result from using the original test procedure are discussed, and a modified procedure and testing arrangement are presented.