Defining the Right Application Range for the Nitrified Acid Fracturing

Abstract Hydraulic fracturing in tight and depleted high-pressure high-temperature (HPHT) gas carbonate reservoirs presents unique challenges, particularly due to insufficient reservoir pressure to support post-fracturing flowback. This paper explores the use of nitrogen in the fracturing process to ensure effective recovery of fracturing fluids and enhance overall stimulation success. In conventional acid fracturing of depleted wells, nitrogen lifting is typically required to initiate flowback. By integrating nitrogen directly into the treatment, this step is eliminated, leading to reduced operational time and cost, and better resource efficiency. As nitrogen is pumped in gaseous form, high-pressure equipment is necessary. Its chemical inertness allows it to be compatible with most fluid systems, making it suitable for standard pumping schedules. The use of energized fluids introduces specific safety considerations that must be addressed. The paper outlines equipment specifications, treatment designs, fluid types, and execution protocols. Field experience over recent years has demonstrated that the advantages of this method outweigh the minor adjustments needed in equipment and procedures. Proper candidate selection is critical, with reservoir conditions playing a key role in determining suitability. The study highlights operational improvements over traditional nitrogen lifting methods and reports productivity gains of up to 48% in depleted zones. It also offers guidelines for selecting between standard and nitrified acid fracturing based on productivity index evaluations. While the research centers on applications in the Middle East, the methodology is applicable to tight and depleted carbonate formations globally. The operational insights, treatment strategies, and field development outcomes discussed will be valuable to stimulation engineers and professionals across the industry.