Study on the Performance and Mechanism of the Acid-Oxidation Dual-Target Blocking Removing System

“Organic-inorganic composite blocking” (interweaving of reservoir polymer residue/biofilm and calcium carbonate scale) is the cause of pressure increase and rate of recovery decline in a water injection block in Yanchang oilfield. In this study, instead of focusing on blocking removal with a single method, a “synergy of acid oxidation with dual-targeting blocking removal technology” is presented. By constructing a ternary synergistic system of sulfamic acid (inorganic targeting)-persulphate (organic targeting)-glycoside surfactant (permeation targeting), full blocking removal by “scale breaking-degradation-unclogging” is realized. Studies show that targeting dissolution of calcium carbonate scale can be realized with sulfamic acid (8%) and hydrochloric acid (2%), the rate of dissolution reaches 85.96% and corrosion inhibition can be realized simultaneously (the rate of corrosion < 0.076 mm/a). Ammonium persulphate, after heat activated, releases radicals (SO₄⁻·/·OH) which precisely degrade polymers and biofilms. Alkyl polyglycoside (APG-12) can reduce surface tension and push the blocking removal agents to go deep into the micro pore throats. Field application has shown that after removing the blockages from the micro pores, the water injection pressure was reduced by 1.5 MPa and time for the blocking removing measures to remain effective exceeded 200 d. This technology provides an integrated solution, which is “mechanism-technology-application”, to the long-term effective treatment of injection well blocking problem.