Over the years environmental legislation has forced changes in the types of scale inhibitor molecule
that can be deployed in certain regions of the world. These regulations have results in changes from
phosphonate scale inhibitor to polymer based chemistry particularly in the Norwegian and UK
continental shelf where phosphonates have either been on the substitution list or phased out for many
applications. Over the past 10 years significant improvements in inhibitor properties of the so called
“Green” scale inhibitors have been made. For one particular operator the squeeze application of this
“green” scale inhibitor resulted in poorer than expected treatment lifetimes and significant operating
cost due to the frequency of retreatment. To overcome the increasing operating cost an evaluation
was made of the current treatment chemicals vs. the older more established phosphonate scale
inhibitors. The results for the laboratory evaluation suggested that the older chemistry would extend
treatment life and reduce operating cost. A case was made to the legislative authority and field
applications started. The squeeze lifetimes for the “red” phosphonate chemistry were shown to be
better than the “yellow/green” inhibitors. This paper presents the laboratory evaluation of the scale
inhibitors, outlines the rationale for the change back to phosphonate scale inhibitors and illustrates
the improvement observed via field results from the 2 wells treated so far.
Keywords: scale, squeeze, phosphonate scale inhibitor, polymer scale inhibitor, environmental