Volume Requirements for Aerated Mud Drilling

Summary Aerated mud drilling has been recognized as having many advantages over conventional mud drilling, such as higher penetration rate, less formation damage, minimized lost circulation, and lower drilling cost. In some areas, the use of aerated mud as a circulating medium for drilling oil and gas wells is becoming an attractive practice. Maintaining an optimum combination of liquid and air flow rates is important in aerated drilling operations. However, most drilling operators are unclear on what constitutes the "optimum combination of the liquid and air flow rates." Guo et al. presented a mathematical approach to determining the flowing bottomhole pressure (BHP) for aerated mud drilling. This paper addresses the use of Guo et al.'s mathematical model to determine liquid and air volume requirements considering wellbore stability, pipe sticking, and formation damage as well as the cuttings-carrying capacity of the aerated mud. From a formation-damage-prevention point of view, the liquid fraction in the fluid stream should be as low as possible. However, a sufficient mud flow rate is always required to make the hole stable and to maintain the cuttings-carrying capacity of the aerated mud without injecting much air volume. This paper provides a simple approach to determining the liquid and air volume requirements for aerated mud drilling.