The paper presents a generalized buoyancy model for application in wells, called the generalized law of Archemedes.
There exist confusion in the oil industry about buoyancy effects as related to the force-area method (also known as piston force) or the principle of Archimedes, the stability force in buckling and axial forces during well intervention operations. This paper will present a general model called the generalized law of Archimedes, which is valid for all cases.
The paper also presents examples of application to ordinary drilling operations, deviated wells and different fluid densities inside and outside the pipe. For well intervention scenarios, the effects of wellhead shut-in pressures on buoyancy are demonstrated. This simple model, not requiring use of a "stability force", can also analyze buckling.
Using the generalized law of Archimedes, 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.