Scale inhibitor squeeze treatments based on modelling studies

Scale inhibitor treatment programs for crude producers in Saudi Aramco have been exceptional in the oil industry. Development and application of various scale inhibitor treatment programs that incorporate the latest university industry-funded research findings improved the treatment lives over ten plus years for lowest possible cost. Phosphonate based scale inhibitor squeeze treatments provide the most effective means of preventing CaCO₃ scale formation in our carbonate fields. Based on the mathematical scale inhibitor squeeze (SIS) model for horizontal wells, we applied a simple bullheaded squeeze treatment avoiding expensive coiled tubing application. Conventional squeeze treatments with acidic scale inhibitors and an aqueous overflush generally resulted in initial high watercut and occasionally productivity decline. Recent research on phosphonate-carbonate interactions, and modelling of these interactions, and the impact of two-phase flow by the FAST group at Heriot-Watt University (HWU) - described in SPE 87448, SPE 100515 and SPE 114105 - led to improved squeeze treatment performance. Based on the above studies, significant changes were introduced to the main scale inhibitor formulation and the overflush stages. These treatments were performed on both vertical and horizontal wells in our largest carbonate oilfield. The new modifications have resulted in better well response compared to earlier acidic scale inhibitor treatments. There was either a small drop in water-cut or else the wells maintained the same value, instead of the increase in water mobility observed with earlier treatments. Similarly, productivity changes are better with the modified treatment compared to the old program. This paper describes the theoretical background in selecting simple bullhead treatment for horizontal wells, partially neutralized phosphonate based scale inhibitor and the overflush formulations and the resulting field productivity changes after treatment. © 2010, Society of Petroleum Engineers.