Research and Application of New Polybasic Acid

Sandstone reservoirs in Huabei Oilfield are characterized by low porosity, low permeability, high clay content, strong heterogeneity and high reservoir temperature. In order to solve the problems of rapid reaction, short effective penetration distance and secondary precipitation in conventional acid system, a new composite acid system is studied. The experimental results show that the acid-rock reaction speed of the new composite acid system is lower than that of the conventional acid system; the chelating ability of Ca2+, Fe3+ and Mg2+ ions is stronger; the corrosion rate of N80 steel is 1.57g/m2•h, far below the industry standard (10-20g/m2•h); the permeability of the core after acidizing increased by 3.5 times. This new type of composite acid system with slow reaction speed, scale inhibition and deep penetration is of great significance for acidizing low porosity and low permeability sandstone reservoirs in Huabei Oilfield.