Colloidal gas aphrons (CGAs) are a thick shell bubbles generated by Sebba in 1971. They have unique properties and many studies have been done to use them in various processes since then. The most recent application of CGAs is to use them in the oil and gas well drilling as one of the major problems in the drilling operation is drilling fluid loss. This means that part of the drilling mud is lost during drilling operation in the formation’s pores. In addition, penetration of drilling mud into the formation’s pores makes them to be blocked permanently. CGAs are a good candidate for preventing pores blockage. The mechanism is that CGAs can fill completely the formation’s pores because of drainage. However, this blockage of pores is temporary and they reopened later after foam collapsed. Hence, the stability issue of CGAs is vital in drilling operation. This research aims to investigate the effect of important factors on stability of CGAs performance. To achieve this goal the drainage curve method has been employed for interpreting experimental results. The examined parameters were: concentration and type of surfactant, stirring time, aphron generator’s disk, distance between shaft and baffle (baffle position), and the effect of nanoparticles. Two types of surfactants, namely Nonylphenol Ethoxylate (NPE) and Sodium Dodecyl Sulfate (SDS), were used to generate CGAs in the presence of nanoclay. The experimental results showed that the presence of nanoclay has a dramatically effect on the stability of CGAs generated from the surfactant SDS while the effect of nanoclay on the stability of CGAs generated from non-ionic surfactant NPE was not observed. In this regard, the aphron suspension generated from SDS has a half life time (which is a measure of stability of CGAs) of 250 s in the absence of nanoclay but the same CGAs dispersion has a half life time of 305 s in the presence of nanoclay. This finding has been reported in this thesis for the first time. The various aspects of contribution of nanocaly in stability of the aphron dispersion was explained. It was found that the presence of nanoclay reduces the surface tension of the SDS solution. The maximum stability of aphron suspension was observed when the surface tension of the base fluid was the minimum (36 mN/m for formulation of 0.1%w SDS and 0.5%w nanoclay). Effect of geometric of aphron generator on the stability of aphron suspension was also investigated and it was found that stirrer’s disk diameter plays a more effective role than the baffle position on the stability of CGAs. The details of full experimental results can be found in this thesis. Keywords: Colloidal gas aphron, Stability, Drainage curve, Gas holdup, Nanocaly