Optimized Sample Preservation for Monitoring Multiple Scale Squeeze Treatments in a Single Comingled Stream Utilizing a Novel Analytical Method

Abstract A crucial part of scale squeeze management in the oilfield is the ability to accurately and precisely monitor scale inhibitor residual concentrations. Reliable residual measurements are essential to determining the lifetime of deployed scale squeeze treatments. When a squeeze campaign is deployed to multiple wells that will comingle into a single flowline, the ability to monitor residuals becomes increasingly challenging and the need to effectively distinguish between the different inhibitors deployed comes into play. A method to differentiate multiple phosphorous-containing scale inhibitors in a single comingled stream has been developed and successfully implemented in the Gulf of Mexico. This analytical method does not require the use of inhibitor tagging for detection or quantification of the scale squeeze residuals. Ion Chromatography-Mass Spectrometry (IC-MS) is currently being used to accurately monitor residuals of three different scale inhibitors from three wells producing/comingling into a single flowline. This field proven method of residual monitoring will significantly reduce the amount of deferred oil production that is often associated with monitoring multiple squeezed wells in the same flowline. Choosing the correct method of sample preservation is a key part of inhibitor residual monitoring. It is well understood that maintaining the stability of ions is critical to determine the scaling potential, effectiveness of a treatment program and as outlined in this paper, the inhibitor molecules of interest. This paper discusses lessons learned when implementing the above mentioned novel analytical method to monitor field samples by highlighting the key optimizations to the current sample preservation methods. The optimized sampling methods used include samples stabilized with an acid, a polymeric scale inhibitor and the addition of a biocide to a polymeric scale inhibitor. The intent of this study was to evaluate the most effective way to preserve water samples being monitored for inhibitor residuals via an IC-MS method.