Acidification of Thick Highly Inhomogeneous Sandstone

Acidification fluid formulation and acidification technology are studied for the best results in the acidification of thick highly inhomogeneous sandstones. It is concluded that for reservoir formations with high shale content and that are poorly cemented, the concentration of the prepad acids shall be reasonably higher (for instance, the concentration of HCl shall be increased to 15%), and the main acid (for acidification) HF shall have its concentration reduced to, for instance, 1%. Slabbed cores in combination with SEM can be used to determine the damaging depths, providing clues for the amount of acids to be used in acidification. For thick porous reservoirs, a combination of packer, perforation with variable intensities and diverting acids can be used in reservoir reformation. For reservoir formations with developed fractures, high flowrate, large amount of fluid and high pump pressure together can be used in eliminating deep plugging of the reservoir.