Abstract:

In order to effectively control the diffusion of H⁺ in the liquid phase to the rock surface， reduce the reaction rate of acid rock， and thus achieve the purpose of deep acidification etching， a foam retarded acid with excellent foam stability， temperature resistance and slow speed performance is prepared by studying the synergistic effect of nanoparticles， foam stabilizer and surfactant. By comparing the dispersion properties of different nano materials in acid solutions and the effect of particle size on the retarded acid properties of foam， hydrophilic SiO₂ nano-materials with d=25 nm are selected. The self-made amphoteric surfactant MAC is used as foaming agent， and the self-made acid thickener （SY-1） is added as the foam stabilizer to achieve foam stabilization. When w（SiO₂）=1.5%， w（MAC）=1.0%， w（SY-1）=0.08%， the formed foam is dense， the liquid film thickness is enhanced， the foam stability is improved， and the half-life was prolonged from 7 min to 69 min. SY-1 improves the high temperature resistance of the foam， so that the half-life of the system can still reach 29 min at 90 ℃. The core dissolution rates under different conditions are compared and the average core dissolution rate of 20% HCl solution is 1.148×10^-3 mg/（cm²·s） while the average core dissolution rate of self-made foam retarded acid solution system in the laboratory is reduced to 7.142×10^-5 mg/（cm²·s） which is reduced by 93.7%. The addition of SiO₂ nanoparticles and foam stabilizer improves the temperature resistance of the system and reduces the acid rock reaction rate， which provides an important theoretical basis for the implementation of acidification process.

Key words: Foam stabilizer, Amphoteric surfactant, Nanomaterials, Foam retarded acid, Heat resistance, Retarded rate