A Study of the Rheology, Stability and Pore Blocking Ability of Non-Aqueous Colloidal Gas Aphron Drilling Fluids

Colloidal gas aphrons (CGAs) recently used as part of water-based drilling fluids have been found effective in controlling the filtration rate by bridging the pores of the reservoir rock and therefore, reducing the formation damage. This research aims to generate colloidal gas aphrons (CGA) in oil based drilling fluids; to study stability, rheology and the filtration loss characteristics of CGAs and to investigate formation damage properties of CGAs as a drilling fluid.;Aphrons were generated in mineral oil using a polymer-surfactant mix. Based on how changing the polymer and surfactant concentration affects the physico-chemical characteristics of the fluid, an optimum formulation for the aphron drilling fluid was suggested.;The stability of microbubbles was investigated by looking at the effects of time, temperature and pressure on the aphron yield and bubble size distribution. Effects of temperature and pressure on the density of the oil-based aphron fluids have been investigated. Based on the PVT analysis results, an equation of state was proposed.;Finally, the performance of the oil-based aphron fluid in porous media was investigated. The effects of changing the CGA fluid injection rate, the type of saturating fluid and the wettability of the porous media on the pressure drop were examined. An assessment of the formation damage following the oil-based CGA fluid injection was also made.