Enhanced the permeability of water invasion sandstone by effectively inhibiting the swelling and dispersion of montmorillonite

Abstract

The long-term effect of protecting water-sensitive reservoirs and enhancing permeability of water invasion reservoir is still an urgent practical problem to be solved. Here, an imidazolium Gemini ionic liquid (IL), PEG-DC8Im, with octyl as tail chain and polyoxyethylene chain as bridging group, was synthesized to inhibit the hydration, swelling and dispersion of clay minerals. The PEG-DC8Im could exert excellent anti-swelling ability (93.82 %) and outstanding washable capacity (cumulative decrease of anti-swelling rate after being washed five times: 1.32 %) at the concentration of 60 mmol/L. The inhibition effect of 20 mmol/L PEG-DC8Im was significantly better than that of 250 mmol/L KCl at 90 °C. And the PEG-DC8Im could intercalate into the interlayer space of MMT through cation exchange to play an inhibition effect, where zeta potential of MMT particles was reduced and then the dispersion ability of MMT was weakened. Subsequently, the anionic polymer poly(AM/AA) was found to cooperate with PEG-DC8Im to improve the inhibition effect for MMT swelling and dispersion, in which poly(AM/AA) was not intercalated into the interlayer of MMT, and only adsorbed on the surface of the particles to encapsulate the MMT particles. Simultaneously, the apparent viscosity and thixotropy of the composite solution were enhanced. Besides, after the treatment of PEG-DC8Im, the displacement pressure decreased and the permeability of sandstone cores increased due to the inhibition of clay mineral hydration, revealing the enhancement of injectivity. Finally, the pore connectivity of the core increased and the water wettability was weakened. The treatment of PEG-DC8Im was conducive to the discharge of invasive water in reservoir and the improvement of the reservoir permeability. Overall, PEG-DC8Im has a good application prospect as permeability-enhancing clay stabilizers.