Test and Evaluation Methodology for Scale Inhibitor Evaluations

Abstract

ABSTRACT This paper deals with an evaluation of scale inhibitor test methods used in the oil, gas and geothermal industries. To our knowledge there exists no other publication dealing with this subject of evaluating and analyzing the various test methods related to scale inhibitor evaluations. There are basically two different types of inhibitor test methods: Test methods aimed at solving a scale problem for routine, day-to-day field operations. Test methods aimed at solving a scale problem for temporary or intermittent field operations. Only the first type of test methods is described in this paper. Laboratory test procedures are used to evaluate and to rank scale inhibitors for field operations. Many of the tests use arbitrarily selected test conditions and many are based on unvarying test conditions. Others evaluate only the inhibitor efficiency without regarding other and simultaneously occuring problems that may dictate the application and usefulness of scale inhibitors in the field. Slight changes in test conditions will usually result in significant changes in the subsequent rankings of scale inhibitors. Each "standard" test may yield inhibitor data and rankings that are completely different from the data and rankings based on other "standard" tests. Any test procedure aimed at selecting an inhibitor for actual field use must consider actually encountered field conditions. Any test matrix should, as a minimum, include all the possible thermodynamic and at least some kinetic and hydro-dynamic conditions encountered by the inhibitor in an actual field. The present paper discusses the advantages and disadvantages of the various scale inhibitor evaluation methodologies suited for the field operator. The relevancy of various evaluation methods for field applications is described. The paper is not oriented toward data obtained through previously or newly conducted inhibitor evaluations or evaluating of specific chemicals. The object is to evaluate and compare known or newly tried inhibitor test methods for field applications.