Research and Application of Temporary Plugging and Acid Diversion Technique for Horizontal Wells in Tight Sandstone Reservoirs

The development of Triassic low-permeability tight sandstone reservoirs in the Changqing Oilfield faces challenges such as poor reservoir properties, thin sand bodies, and interbedded layers, hindering effective development. Horizontal wells combined with hydraulic fracturing have been the primary completion method. However, the disparity in permeability between artificial fractures and matrix permeability leads to scaling deposition after years of production, resulting in significant yield reduction. Furthermore, contradictions between interlayers and fractures exacerbate production challenges. Conventional acidization techniques have proven ineffective in achieving uniform acid distribution within long horizontal sections, often leading to water breakthrough due to excessive acidization of high-permeability zones. This study introduces a novel approach using an acid-resistant, self-degradable temporary plugging agent combined with a self-diverting acid system. The temporary plugging agent withstands pressures up to 33 MPa and degrades completely within 72 h at a rate of 3.3% in 2 h. The self-diverting acid employs dual thickening mechanisms based on reaction and pH value, achieving a 95% dissolution rate of scale samples. The integrated technique achieves an overall diversion efficiency of 85.2%, effectively preventing acid from entering high-permeability channels and optimizing acid distribution within horizontal well sections and fractures. Field application across 22 horizontal wells demonstrated a success rate of 95.4%, with an average daily oil production increase of 3.14 tons per well. Compared to neighboring wells treated with conventional acidization, daily oil production increased by 41.6% per well, accompanied by a 12.3% decrease in water content post-acidization. This innovative method offers a promising strategy for controlling water breakthrough and enhancing production in heterogeneous or low-permeability fractured sandstone reservoirs, marking a significant advancement beyond traditional acidization techniques.