Colloidal gas aphron (CGA) consists of spherical gas microbubbles with diameters ranging from 10-100m. Unlike regular foams, CGAs have a thin aqueous protective shell which makes them useful as a component of drilling fluid for practical applications. This paper reports on physicochemical properties of fluids containing CGAs. To this end, various laboratory tests of CGA generation, microscopic visualization, density measurement, API filtration loss, and rheological characterization with varying concentrations of biopolymer and surfactant were carried out. Three rheological models, namely the Bingham plastic, Casson, and Power-law, were also employed to quantitatively describe the shear flow behaviour of CGA-based fluids. Moreover, the CGAs performance as a filtrate-reducing component was examined thorough a standard API filter press. The results of this study are helpful for better understanding the characteristics of CGA-based fluids.