A Novel Scale Inhibitor Chemistry for Downhole Squeeze Application in High Water Producing North Sea Wells

Abstract

ABSTRACT This paper presents a novel scale inhibitor chemistry for achieving cost effective and extended squeeze lifetime in high water producers that can significantly reduce the number of treatments. The new and proprietary concept called Mobil Scale Inhibitor Process (MSI) is based on additives in the scale inhibitor solution that activate the phase separation of up to 85% of the total injected inhibitor during the well shut-in period following afterflush. Such an inhibitor retention is much higher than obtainable by conventional adsorption or precipitation mechanisms. The activation is temperature, time and pH driven and allows the inhibitor slug to be safely displaced into the formation before phase separation occurs. Furthermore, this squeeze chemistry am be applied to most of the commonly used scale inhibitors such as phosphino-polyacrylic acids (PPAA), polyacrylic acids and phosphonates to improve their squeeze performance. MSI is environmentally friendly and has an OCNS (Offshore Chemical Notification Scheme ) category of zero. In corefloods with either PPAA or phosphonates under simulated North Sea reservoir conditions, this new chemistry resulted in a 2-12 fold increase in the squeeze lifetimes. Computer modeling predicts significant increase in inhibitor lifetime when applied in the field. To date, field trials by Mobil North Sea Limited support the laboratory work and well productivity was not damaged. This new technology is believed to be a significant advance in achieving long-lasting and cost-saving downhole squeeze treatments for preventing scale deposition, particularly for for high water producing wells. Furthermore, it does not increase complexity in field operation when compared with conventional treatments.