The aphron-based drilling fluids are designed to minimize formation damage by blocking the pores of the rock with micro-bubbles, which can later be easily removed when the well is open for production. Micro-bubbles behave like tough, yet flexible bridging materials, and form an internal seal in a pore-structure. Proper sizing of the micro-bubbles with respect to pore size distribution is essential for developing an aphron-based drilling fluid with effective sealing ability. The properties like rheology and compatibility with oils also need to be better understood. In this study, the size distribution of aphrons as well as the change in the aphron size with time was determined using a visual imaging technique. Formation fluid compatibility was conducted to evaluate the compatibility between the aphron-based drilling fluids with four oils. The effects of pressure and temperature on the rheological properties of aphron-based drilling fluids were also investigated, and the regression analysis method was used to establish the constitutive equations of tested liquids under various temperatures.