Numerical study of vug effects on acid-rock reactive flow in carbonate reservoirs

Matrix acidizing is one of the most practical stimulation technologies for carbonate reservoirs, which effectively improve the region permeability near the wellbore. In addition to solid matrix, vugs are also very common in carbonate reservoirs. However, a few studies have been addressed with existence of vugs on carbonate acidizing process. In this work, a two-scale model is developed using dual domain method and discrete vugs model to study effect of vugs on acidizing process. Darcy equation is employed in solid matrix region. Navier Stokes equation is adopted for free flow region in vugs. The two regions are coupled by modified Beavers-Joseph-Saffman boundary condition. Numerical cases are conducted to present the effect of vug characteristics on acid-rock reaction process. The results show that acid solution has the largest effective reducing distance and the smallest breakthrough volume in circular vugs. Dominant wormhole is created when acid injection direction is parallel or vertical to the azimuth angle of vugs. Increasing amount of vugs in horizontal effectively reduces the flow distance and breakthrough volume of acid solution. Vugs with random distribution increases effective flow distance and breakthrough volume of acid solution compared to vugs with orderly distribution. Cited as: Huang, Z., Xing, H., Zhou, X., You, H. Numerical study of vug effects on acid-rock reactive flow in carbonate reservoirs. Advances in Geo-Energy Research, 2020, 4(4): 448-459, doi: 10.46690/ager.2020.04.09