The construction and mechanisms of a O/W microemulsion acid blockage remover system for low permeability reservoirs

Segmental injection as well as high corrosion of the conventional matrix acidizing treatment is harmful to the environment. In this work, a new O/W microemulsion acid (MEA) blockage removal system was developed combining slow-release acid and microemulsion to address these problems. This system could further reduce corrosion, showed great blockage removing ability, and be injected uniformly. HLB and pseudo-ternary phase diagram methods were used to optimize the components of the MEA system and lab tests were used to measure its effective performances and mechanisms. The results indicated 1.5 wt% D-limonene, 0.9 wt% Sodium dodecyl sulfate (SDS), 0.6 wt% JFC, 3.5 wt% N-butanol and 30 wt% slow-release acid was the ideal formulation for the MEA system. The MEA system outperformed the traditional toluene-mud acid system in laboratory settings, with blockage removing efficiency exceeding 8%, and its corrosion rate was just 6.34% of pure mud acid. The blockage removal mechanisms for the MEA system were the synergistic effects of the dilution modification effects of the light oil phase, the emulsification carrying effect of the emulsifiers and slow-release acidification effects of the acid system.