The apparent loss of weight of an object immersed in a fluid.
If the object is floating, the immersed portion displaces a volume of fluid the weight of which is equal to the weight of the object.
The upward force acting on an object placed in a fluid.
The buoyancy force is equal to the weight of fluid displaced by the object.
Buoyancy can have significant effects in cases in which the wellbore and tubing string contain liquid and gas.
Any change in the relative volumes or fluid levels will change the buoyancy forces.