“Red” vs. “Green” Scale Inhibitors For Extending Squeeze Life – A Case Study From North Sea, Norwegian Sector – Part II

摘要

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 resulted 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. However 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 who approved the use of the phosphonate scale inhibitor and field applications started. The squeeze lifetimes for the “red” phosphonate chemistry were shown to be significantly better than the existing “yellow/green” inhibitors. During the following months other scale inhibitors with improved environmental characteristics were developed and evaluated. One such molecule was shown to have similar coreflood retention than the applied “red” phosphonate and presented no formation damage. This paper presents the laboratory evaluation of the new scale inhibitor, illustrates the improvement observed with this new inhibitor via field squeeze treatment results from a well treated with both the “red” and new “yellow” environmental profile inhibitor chemicals. This paper outlines the challenges with environmental legislation and how it has been possible to develop technical solutions (both in terms of environmental vs. safety issues and with new inhibitor chemicals) to meet the challenges of offshore scale control.