LAUSR

Abstract Colloidal gas aphron (CGA) based fluids have recently been introduced to develop depleted hydrocarbon reservoirs due to their ability in controlling fluid losses. Bubbles size of CGAs plays an important role in pore blockage ability as the controlling mechanism in fluid invasion reduction. However, fundamental understanding of how bubble size distribution is controlled by polymer and surfactant concentrations is not well discussed in the available literature. Almost all reported experiences on CGAs sizing were conducted on single bubble behavior, and little attention has been given to the variation of bubble size distribution (BSD) of CGAs at different levels of polymer/surfactant concentration. Here, an experimental study was conducted to investigate the role of surfactant, Sodium Dodecyl Benzene Sulfonate (SDBS), as well as polymer, Xanthan Gum (XG), concentrations on BSD of CGAs using optical microscopy. The results revealed that with increasing polymer and surfactant concentrations, BSD of CGAs shifted to lower and higher diameters, respectively. As time goes by, inter-bubble gas diffusion phenomena affects CGAs bubble size, and distribution curves will shift toward higher diameters. Closer investigation of distribution curves at later times showed that with increasing polymer and surfactant concentrations, the effect of inter-bubble gas diffusion became weaker, and hence fewer changes in distribution curves were observed. For the range of tests conducted here, the most stable CGAs were formed at 6810 ppm of XG and 799 ppm of SDBS concentrations. The results of this work provide an insight into appropriate formulations for CGA fluids for possible applications in drilling operations.