A Novel Single-Stage Sandstone Acid System for Low-Temperature Applications

Abstract Sandstone matrix acidizing treatments traditionally rely on multi-stage designs involving solvent and acid preflush, main acid, and post-flush fluids. These sequences often result in induced formation damage, especially in clay- and carbonate-rich formations. This challenge becomes more pronounced at low reservoir temperatures, where slow reaction rates necessitate the use of stronger mineral acids, increasing the risk of secondary and tertiary reactions and leading to compatibility issues with acid-sensitive clays. A new low-temperature, single-stage sandstone acidizing fluid (LT-SSAF) has been developed to deliver effective sandstone stimulation in the low-temperature range of 63 to 210 °F (17 to 99 °C). This paper presents the laboratory and field evaluation of the new system and compares its performance with that of legacy acid formulations.The fluid system was developed through extensive laboratory testing of mineral dissolution efficiency, ion compatibility, and cleanup characteristics. Batch reactor tests quantified the dissolution of aluminosilicates and evaluated calcium ion tolerance in spent acid. Coreflow experiments on Berea and field sandstone samples assessed permeability enhancement under low-temperature conditions. Laboratory results confirmed superior aluminosilicate dissolution and over 100% higher calcium-ion tolerance compared with standard mud acid systems. Coreflow tests showed 27–36% permeability improvement across representative sandstone samples. The fluid was deployed in nine matrix-acidizing jobs across onshore and offshore assets, all executed in a single stage without an acidic preflush, covering formations with permeability ranging from 0.3 to 300 md. Post-job performance was evaluated using production data, surface pressure response, and qualitative operator feedback. Wells with available data showed oil rate increases of up to 230% compared with prestimulation levels. All operators provided positive feedback, and no mixing or pumping issues were reported. Overall LT-SSAF demonstrated consistent performance, reliable cleanup, and operational robustness under low- to moderate-temperature conditions, while reducing treatment complexity and chemical volume. This system extends single-stage sandstone acidizing into the low-temperature domain below 160 °F (71 °C) and complements existing systems developed for higher bottomhole temperatures (Zhao et al. 2022; Okpalla et al. 2025). It reduces treatment volume, operational complexity, and risk, and its performance has been confirmed through comprehensive laboratory testing and nine field deployments.