Theory and application of buoyancy in wells

Abstract

The paper presents a generalized buoyancy model for application in wells, called the generalized Archimedes' principle. There exists confusion in the oil industry about buoyancy effects as related to the force-area method (also known as piston force method) or the Archimedes' principle, the stability force in buckling and axial forces during well intervention operations. This paper will present a general model called the generalized Archimedes' principle, which is valid for all cases. Using the generalized Archimedes' principle, a correct assessment of the real axial load of the pipe is obtained, a critical factor for tubular work in petroleum wells. The model is also significant as it is simple and can be applied to all well operations. The paper presents examples of application to ordinary drilling operations, deviated wells and different fluid densities inside and outside the pipe. Two field cases are presented to demonstrate the use of the generalized Archimedes' principle in torque and drag analysis.