Foamed Acid Plug-Removal Technique for Horizontal Wells in Heavy Oil Reservoirs

In this paper, a series of studies was conducted on the foamed acid plug-removal technique used to to remove near wellbore contaminants in horizontal wells in heavy oil reservoirs .The studies were conducted drilling and production to improve plug removal effects. Based on foam performance evaluation experiments and near wellbore contaminant corrosion tests, the formula of foamed acid system was optimized with the heavy oil reservoirs in the west of Block Zheng 411 as the examples. The sand pack core flooding experiment and foamed acid viscosity test were conducted on foamed acid to study its sand carrying and suspending capacities. The optimized formula was good in foaming properties with foaming volume of 380 mL and half-life time of 450 s. It was excellent in terms of sand carrying and suspension capacity. Its maximum viscosity was 2 629 mPa·s, and the sand settling velocity in the foamed acid could be ignored. This technique was applied in 12 wells in the west of Block Zheng 411. Thus, production cycle was extended by 71 d and the oil incremental per cycle averaged 1 080 t. It was shown that this technique could remove the near wellbore contaminants of horizontal wells in heavy oil reservoirs efficiently and greatly increase oil production.