عنوان مقاله [English]
Preparing drilling fluids is the most important part of the drilling operation of oil and gas wells that the use of advanced and beneficial technologies in their production can be closer to their performance and efficiency than the ideal values. Colloidal gas Aphron (CGA) based drilling fluids with advanced technology of aphron micro-bubbles and particular for Under Balance Drilling (UBD) are one of the newest technology that is used in the drilling of low pressure reservoirs. With production of aphron oil-based drilling fluid can be achieved together positive and valuable properties of oil-based drilling fluids along with special properties such as lost circulation of aphron based drilling fluids. Stability over time is the most important characteristic of aphron based drilling fluids that can be influenced on desirable rheological properties and control of lost circulation in this type of fluids. In this study, aphronized fluid with 2.14 mole percent surfactant and 15.01 kg/m3 polymer concentration has the highest stability over time, lowest yield loss and the lowest bubble size changes that these concentrations are presented as optimal concentration of surfactant and polymer.