The Procedures that Time Forgot: Sample Preservation, Back to Basics

Abstract

A key part of the oilfield scale management toolbox is the ability to determine the concentration of residual scale inhibitors and scaling ions in produced waters. This data is essential to providing correct recommendations for how to manage and inhibit scale in a particular system, as well as monitoring the efficacy of scale management processes already in place. The progression of analytical techniques over the last two decades has provided enhanced methods for accurate detection of ions and scale inhibitors to low limits of detection, however, correct detection of analytes present in a sample in the laboratory does not necessarily equal characterisation of the analytes in-system as they were present at the point of sampling. The collation of a range of preservation techniques, each appropriate to a different group of analytes, forms the basis of this paper. The results of several field applications of incorrect sample preservation are outlined and the alternative preservation technique used to correct the analysis will be detailed. The implication of using the correct preservation technique will be clearly shown to have an impact on scale management where it would lead to reduction of over treatment, leading to increased revenue, whilst also eliminating incorrectly scheduled early well interventions.