Abstract Stimulation performance in tight carbonate formations remains highly sensitive to fluid selection and placement. This work investigates the effectiveness of acid systems—28% Hydrochloric Acid (HCl) and a 28% Lightweight Single-phase Retarded Acid System (SPRA)—in horizontal wells drilled in a complex tight carbonate reservoir of Kuwait's Wafra Field. Key objectives include characterizing fracture geometry, evaluating vertical growth into overlying barriers, and analyzing production behavior as a function of lateral landing strategy and fluid design using advanced diagnostics. A 23-stage Plug and Perforation acid fracturing program was executed using mechanical diversion and real-time data acquisition to improve stimulation efficiency. Microseismic monitoring and far field 3D sonic imaging using azimuthal sensors provided detailed insights into fracture orientation, height, and extent. Chemical tracers were deployed to quantify contribution from each interval. Comparative analysis between HCl and Lightweight SPRA focused on fluid placement efficiency and stimulated volume. Post-treatment evaluation incorporated geomechanical modeling and seismic interpretation to validate design assumptions and guide future stimulation strategies in the target tight carbonate's structurally heterogeneous, low-permeability environment. Fracture orientation across all observed stages aligned consistently at N45°E. Approximately 70% of the fracture propagation remained within the target zone, while 30% extended vertically into the barrier formation. Although both acid systems produced similar upward growth profiles, Lightweight SPRA-treated stages demonstrated significantly greater downward propagation and longer fracture lengths—nearly double those achieved with HCl—indicating superior penetration and reservoir contact. Tracer analysis confirmed broader stimulation coverage in all Lightweight SPRA stages, supporting improved fluid efficiency and treatment distribution. Microseismic and 3D sonic imaging results correlated strongly with pre-job geomechanical predictions, validating model accuracy and enhancing confidence in the design workflow. Operationally, the Lightweight SPRA system delivered more consistent performance in terms of fracture containment and connectivity in tight, variable rock properties. The findings highlight how optimized fluid selection, coupled with integrated diagnostics, can significantly improve stimulation outcomes in carbonate systems with complex geologic features. This case underscores the value of tailoring stimulation approaches based on real-time data and subsurface conditions, offering practical insights into acid system behavior and landing zone impacts—both of which are critical for future field development planning. This paper documents the first application of integrated 3D sonic imaging, microseismic monitoring, and tracer analysis in an acid fracturing campaign. It provides a unique and quantitative comparison of two acid systems in a carbonate reservoir, offering new insights into how fluid design influences fracture geometry and effectiveness. The results enhance geomechanical modeling accuracy and present a data-driven workflow that can be replicated in similar tight carbonate environments to improve stimulation design and reservoir connectivity.
Al-Qatari et al. (Mon,) studied this question.