Novel Density-Controlled Acidizing Approach: Weighted Single-Phase Retarded Acid System in Conjunction with Light-Density Gel Slugs and Fluidic Oscillator Technology Shows a Two-Fold Oil Production Increase and 10% Water Cut Reduction in a Single Run

Abstract A novel strategy to optimize hydrocarbon recovery from low-permeability carbonate reservoirs under challenging high-pressure/high- temperature (HP/HT) conditions is discussed, along with water intrusion from higher-permeability layers. The strategy uses coiled tubing (CT), a tailored 60-cp gel slug, and a single-phase hydrochloric retarded acid (SPHRA) system, densified via the density control acidizing (DCA) principle. This approach was tailored to the reservoir complexities and an HP/HT environment. Rigorous simulation studies informed the acid solution formulation, focused on leakoff control in the upper high-permeability layer. The high gel load (60 cp) strategy combined with CT assistance facilitated precise placement and isolation of the water-bearing zone to mitigate reservoir challenges. Enhanced CT placement using a fluid oscillating tuned frequency and amplitude (FOTFA) tool, coupled with DCA for the hydrochloric retarded acid (HRA), resulted in deep penetration into the near-wellbore (NWB) region. Post-operation analysis confirmed successful mitigation of water intrusion from higher-permeability layers, with no increase in water cut observed. Strategic HRA deployment led to substantial and sustained improvements in hydrocarbon production. The strength of the HRA, combined with meticulous FOTFA deployment planning and a tailored DCA-enhanced acid solution, demonstrated adaptability and efficacy in extreme reservoir environments. This integrated methodology overcame challenges posed by layered reservoir structures and sets a new standard for precision in HP/HT reservoir management. The innovative synergy of a high-viscosity gel slug and the novel HRA with FOTFA placement, customized and densified via the DCA principle, are presented. The integration of DCA into the acid system ensures adaptability and optimal performance in extreme reservoir conditions, which marks a significant advancement in reservoir stimulation practices.