Squeeze Chemical for HT Applications – Have We Discarded Promising Products by Performing Unrepresentative Thermal Aging Tests?

Abstract

Abstract Selecting an effective scale inhibitor for squeeze application at 170°C is no simple task. The traditional thermal stability test by aging the chemical in bulk is often perceived to be too harsh. This results in many promising products being rejected due to their apparent degradation at temperature. The alternative of conducting aging test inside core materials, hence more representative to the downhole conditions, is NOT a novel idea. However, no definitive data is available to date that can substantiate such argument and quantify the difference between the two methods. This is mainly due to the difficulties and complexity to conduct such an experiment at high temperature over a long period of time. In this paper, the results from a recent investigation are presented. It describes the detailed procedures during the planning and execution stages, lessons learnt and pitfall to avoid. A scale inhibitor was aged using two different methods, one in bulk as commonly practiced in the industry and one inside a sandstone core. The aging period varied between 45 days as in the bulk and 110 days as for the last desorbed sample from the core. The samples which were aged inside the core retained much of their inhibition efficiency whilst that aged by the traditional method (bulk) lost nearly all its effectiveness. These results CLEARLY demonstrate that the conventional method of thermal aging in bulk is unrepresentative and that the loss in performance can be quantified. A NOVEL finding from this study is the evidences of an unexpected relationship between desorption and inhibition effectiveness. The findings from this study will have great impact on selecting chemicals for HT applications. More so in those environmental sensitive regions where the use of ‘yellow’ (biodegradable) squeeze chemicals are mandatory. Many of these have been discarded due to their apparent thermal degradation which is now proved to be unrepresentative.