The impact of pre-flush additives on scale squeeze treatments: Application of modelling and new test methodologies to understand mechanisms of retention and optimise field treatment designs

One of the most common methods to prevent scale deposition in the near wellbore area is through the application of squeeze treatments which conventionally consist of pre-flush, main treatment, overflush, shut-in and back production stages. The use of additives such as polyamino acids and polyquatemary amines has often been successfully applied as part of the pre-flush stage of squeeze treatments to improve treatment lifetimes (Chen et al., 2006, Vazquez et al., 2011, Heat et al., 2012). However, although this technology has been successful applied in the field, there is still a lack of understanding of the prevalent retention mechanisms with different scale inhibitors and also a suitable test methodology and modelling techniques to optimize field treatment designs and lifetimes. A new sand pack methodology which provides a better simulation of field squeeze treatments than traditional corefloods has been designed to provide a better understanding of the scale inhibitor retention mechanisms when polyquatemary amines are applied in pre-flush treatments. This has enabled improved treatment modelling and the impact of these additives to be understood in field treatments. The performance of the polyquatemary amine is dependent upon scale inhibitor chemistry and the mechanisms of retention are addressed for both polymeric and phosphonate scale inhibitors. The adsorption isotherms were derived and compared in the absence/presence of the polyquatemary amine using specialized software, and applied to predict squeeze lifetime in field scenarios. This paper provides an understanding on the effects of polyquatemary amines on squeeze lifetime for both phosphonate and polymeric scale inhibitors supported by the application of a newly developed test methodology and computer modelling techniques. In addition, the combination of laboratory and computer modelling data coupled with field experience and a better understanding of the retention mechanisms involved now provides the ability to improve and optimize field squeeze treatment designs with polyquatemary amine pre-flush additives.