Foamed Co2 Fracturing: Enhancing Productivity in Carbonate Formations in High Pressure High Temperature Wells in Middle East

The primary purpose of pumping foamed CO2 fluids during fracturing operations is to aid in post-fracturing flowback especially in tight and(or) low pressure formations, where reservoir is not supporting sufficient energy to flowback the fracturing fluids. This type of treatment has shown to be beneficial in deep and tight carbonate formations together with a tailored set of acid systems. The pumping schedule was typically designed with three primary treatment fluids to be pumped in a series of cycles. These fluids include a linear gel, 28% HCl, and a viscoelastic self-diverting acid based on 15%-20% HCl. The target range for bottom hole foam quality was 55-65%. Since CO2 is pumped as a liquid, standard hydraulic fracturing pumps could be utilized. Vertical single stage, vertical multi-stage and horizontal multistage completions were successfully utilized during the multi-year CO2 fracturing campaign across one of the World's largest conventional fields. This paper will present an evolution of the hi-tier CO2 pumping operations in the extreme geological environment of tight HPHT carbonate formations. Evolution of the CO2-based foam fracturing technology is provided with support from engineering and implementation teams throughout the campaign since the start of the first CO2 job. Significant progress has been made in well completions to accommodate the CO2 technology treating low pressure wells. Such wells once treated with normal fluids, nitrogen lifting is used resulting in additional operational efforts. Technology is particularly helpful in reducing the water consumption and polymer residues by replacing fluids with CO2 up to 60% per stage. This allowed to leave a significantly cleaner reservoir with additional energy to start hydrocarbons production faster, resulting in significant increase in wells productivity when compared to conventional fracturing method. Quality of the CO2 foam fracturing operations was under control without any issues occurred during the campaign (outperforming average conventional operations efficiency). Comprehensive study that includes logistics, mixing and execution side of these treatments as well as engineering and field development aspects will be of vital interest to stimulation experts in conventional gas resources and extend this expertise to unconventional resources.