Practical Approach to Volume Requirements for Air and Gas Drilling

Abstract

ABSTRACT Air, mist, foam, and other variations of aerated fluid drilling are utilized in various areas because of the improved penetration rate when compared to conventional mud drilling. Other proven advantages include immediate and continuous evaluation of cuttings for hydrocarbon shows, low cost, longer bit life, better control in cavernous and lost circulation areas, and minimum damage to liquid sensitive pay zones. The high compressibility of aerated drilling fluids and multiphase flow phenomena encountered when using these fluids have given rise to sophisticated engineering approach to achieve proper downhole cleaning and material transport. There have been several attempts to calculate the minimum volumetric requirements for air and gas drilling. The results of these studies are valid over limited ranges of drilling rates at best. The reason is that there are so many variables involved in an air or mist drilling situation that one general correlation has not been developed to explain what is happening downhole and predict appropriate air or gas injection rates in the field. The method described in this paper will permit the driller and drilling engineer to determine optimum fluid injection rates in the field. It eliminates the need for complicated flow calculations used to predict volumetric air requirements.