Preparation and Foam Stabilization Mechanism of an Ultrahigh-Temperature Colloidal Gas Aphron (CGA) System Based on Nano-SiO2

Abstract

Recently, colloidal gas aphron (CGA) drilling fluids have successfully solved the problem of drilling low-pressure depleted oil and gas reservoirs. However, with the increase in the drilling depth and the development of geothermal resources, high-temperature stable CGA drilling fluids need to be developed urgently. This research reports a highly stable nano-SiO2-based CGA system with a temperature resistance of 200 °C. Waring-Blender tests show that 1.5-3% nano-SiO2 greatly improves the high-temperature stability of the CGA system, and the half-life of foam aged at 120-200 °C can reach 6-12 h. Also, the nano-SiO2-based CGA system aged at 200 °C can maintain an independent and stable morphology during the observation period (60 min), and there is no obvious drainage and merger in the system. The stabilizing mechanism of nano-SiO2 has been revealed, which can be summarized as the comprehensive effect of adsorption, viscosity increase, and cross-linking. In other words, the addition of nano-SiO2 enhanced steric hindrance and liquid film strength by reducing the surface tension, increasing fluid viscosity, and forming a network-like structure.