Unlocking Reservoir Potential in Low Reservoir Pressure Through Efficient CO2 Foamed Acid Fracturing

Acid fracturing in challenging gas wells imposes multiple areas for improvement. The objective is to implement effective acid fracturing treatment with combination of CO2 foam and the use of dissolvable plugs to maximize diversion across the net pay and to improve overall operations efficiency. The scope of the paper shows improved well production and operations efficiency using CO2 foamed acid fracturing and dissolvable frac plugs compared to conventional acid fracturing. The area of improvement for acid fracturing is to ensure effective fluid diversion across target pay. Effective stimulation is through shorter interval with multiple stages using temporary isolation rather than through single stage and longer interval. The choice of dissolvable frac plugs for temporary isolation is to eliminate coiled tubing milling operations. The use of CO2 foamed technique provides good acid retardation for effective diversion and extended reaction with formation. CO2 foamed acid fracturing treatment uses lower stimulation fluid volume compared to conventional treatment. Volume reduction and the energized foam accelerates flowback for effective well cleanup. The combination of CO2 foamed fracturing technique and the use of dissolvable frac plugs were applied in gas Well-A, having high temperature and low reservoir pressure. Well (A) was completed with two stages treatment with temporary isolation using a dissolvable plug to ensure good stimulation across the pay. CO2 foam lowers the formation temperature which reduces acid reactivity on sand face resulting in deeper etched fracture length. Foaming agents are included in the stimulation fluid to maximize CO2 entrainment producing stable foam for effective diversion and energizing the fluid to accelerate well flowback. Reduction of flowback time and enhanced clean-up can be attributed to the CO2 energize assist and significant fluid volume reduction, up to 50% reduction compared to conventional treatment. The use of dissolvable frac plugs coupled with CO2 stimulation, eliminates the need of coiled tubing milling and N2 lifting intervention as a result of reducing the wellbore hydrostatic column. The effectiveness of this technique can be proven from higher production in gas rate compared to other reference wells that were not treated similarly. Overall operations efficiency is improved due to reduced logistics, reduced fluid mixing, enhanced flowback rate and eliminating the need of Coiled Tubing intervention.