Aerated Fluids Drilling

This chapter outlines the steps and methods used to plan a successful aerated fluids drilling operation and discusses the application of these steps to deep drilling operations by assuming a performance drilling operation and using standard drilling mud and atmospheric air as aerated drilling fluids. The term “aerated fluids” describes the broad category of drilling fluids that are basically incompressible fluids injected with compressed air or other gases. Aerated drilling fluids are used to drill both shallow and deep boreholes. Aerated drilling operations use a variety of incompressible fluids and compressed gases to develop a gasified drilling fluid. The majority of the operations use standard fresh water-based drilling mud with injected compressed air or membrane- generated nitrogen. Several drill string and well configurations are used for aerated fluid drilling operations. These are divided into two general technique classes of air (or gas) injection operations: drill pipe injection and annulus injection. The drill pipe injection technique requires that both the incompressible drilling fluid injection and the compressible gas injection be suspended when connections and trips are made. The annulus injection technique requires that the incompressible drilling fluid injection be suspended when connections and trips are made. The analyses of aerated fluid vertical drilling problems are carried out by two distinct analytic methodologies. The first methodology ignores the major and minor friction losses due to fluid flow inside the drill string and in the annulus. The second methodology can include all the complexity of fluid flow friction losses.