Improving Bail-Down Testing of Free Product Wells

摘要

Bail-down testing of a well with free product is a good way to assess the type of free product recovery system tornuse in that well. Bail-down testing consists of removing a volume of free product and then monitoring the raternof free product recovery in the well. Recently, environmental regulators in Michigan stipulated that "bail-downrntests should be conducted in all monitoring wells with free product to assess the appropriate interim and finalrnrecovery methods" [MDEQ STD Operational Memo. No. 7 (Revised 2/26/01)]. Follow-up annual bail-downrntests are also recommended for all wells with free product. These test results are submitted to the state togetherrnwith qualitative analysis suggesting whether the free product recovery actions underway at the site arernappropriate. For example, if free product returns very slowly to a well following product removal, it would be arnmistake to install an expensive active-recovery system in that well. In contrast, if product flows readily into arnwell during a bail-down test, that is a good sign that a properly-designed and built active system would bernjustified. No recovery system should be installed until a bail-down test has been performed on the well inrnquestion.rnThis paper establishes test protocols for manual and automated (using an acoustic range finder and a pressurerntransducer) tests, shows examples of tests and their interpretations, and suggests improvements in thernpresentation and analysis of bail-down test data. Since standard bail-down tests are not generally repeatable, wernsuggest a protocol to achieve repeatable comparative tests pumping two wells simultaneously and show resultsrnfrom such tests. Finally, we propose a longer-term test similar in purpose to a bail-down test but which can berndone using information that often would have been gathered in the course of monitoring and periodically bailingrnfree product from a well.