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

Abstract

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.

The state of the art in scale inhibitor squeeze treatment

“…Therefore, quaternary amine types of chemicals are proposed to be used in both preflush and overflush as a bridging agent for inhibitor retention (Selle et al 2003;Heath et al 2012;Sitz et al 2012). Amine groups are also incorporated into the anionic polymer to improve the anionic inhibitor retention in the formation rock in squeeze treatments (Jordan et al 2011b;Chen et al 2011). Jordan and his collegues reported a phosphorus-containing polymer amine chemical (PCPA) which have both the properties of ease of detection from the P tag and desired chemical retention release characteristics from the amine tag and the retention is comparable to that of phosphonate (Jordan et al 2011b;Sutherland et al 2018).…”

“…The nonaqueous scale treatment is generally more expensive and might induce formation damage because the chemicals, such as mutual solvents, surfactants, and additives, can induce other damages and costs. In a review of various types of non-aqueous delivery systems, a majority of over 30 treatments produced acceptable treatment life with no measurable change in the productivities (Jordan et al 2011b). Many of these non-aqueous systems use the same type of scale inhibitors, and the retention mechanism appears to be similar to that of the aqueous system.…”

“…Many new inhibitors have been developed for better monitoring and tracking, such as the P containing inhibitors (e.g., phosphorus end cap inhibitor) (Selle et al 2003) and fluorescence tagged inhibitors (Poynton et al 2012;Vuori et al 2016). In addition, there are multifunctional inhibitors such as one with either or both the phosphorus and the amine tags (Montgomerie et al 2009;Jordan et al 2011b), where the amine tag increases the scale inhibitor retention. An innovative time-resolved fluorescence (TRF) method has been developed (Johnstone et al 2014(Johnstone et al , 2015Heath et al 2019) for scale inhibitor analysis.…”

Laboratory investigation of co-precipitation of CaCO3/BaCO3mineral scale solids at oilfield operating conditions: Impact of brine chemistry

“…Scale formation is a ubiquitous phenomenon in nature and in daily life. However, massive scale formation and subsequent precipitation can lead to throughput reduction and eventually pipe/conduit blockage in various industrial processes (Bukuaghangin et al, 2016;Ghaderi et al, 2009;Jordan et al, 2012;Kan and Tomson, 2012;Lecerf et al, 2005;Rostami et al, 2019;Vazquez et al, 2016;Zhang et al, 2018b). Scale associated operational issues are particularly challenging in oilfield operations and especially in deepwater productions (Fink, 2011).…”

Environmentally Focused Crosslinked-Gel System Results in High Retained Proppant-Pack Conductivity

“…Some of these efforts focused on replacing certain chemicals with alternative "greener" chemicals that have similar performance (El-Monier and Nasr-El-Din 2011;Jordan et al 2011;Mahmoud et al 2010;Gomez 2010). Engineering advances have been made to remove or reduce the reliance on chemicals altogether.…”