Rheological and Filtration Loss Characteristics of Colloidal Gas Aphron Based Drilling Fluids

Colloidal gas aphron (CGA) fluids, consist of gas bubbles with diameters ranging from 10 to 100 μm, surrounded by a thin aqueous surfactant film. This fluid combines certain surfactants and polymers to create the systems of microbubbles. The function of surfactant in CGA is to produce the surface tension to contain the aphrons. Also a biopolymer needs to be considered in the formulation as a viscosifier as well as stabilizer. The aphron-laden fluid appears to be particularly well suited for drilling through depleted zones. The unique feature of aphron based fluids is to form a solid free, tough, and elastic internal bridge in pore networks or fractures to minimize deep invasion by means of air microbubbles. This microenvironment seal readily cleans up with reservoir flow back as production is initiated, thereby reducing cost associated with stimulation processes. This paper presents a comprehensive, comparative study of rheological behavior and filtration properties of CGA based drilling fluids with various concentrations of polymer and surfactant. Laboratory evaluations showed that the CGA based fluid is one of the ideal engineering materials which can control fluid loss or loss circulation during drilling operation, save cost and increase productivity which rheological characteristics and filtration properties of them are greatly influenced by the level of polymer and surfactant concentration.