MODELLING OF SURGE AND SWAB PRESSURE

Surge and swab pressures have been for a while an issue in the drilling of oil wells. The drill string causes a flow for displaced fluid and a pressure change in the borehole when running in or pulling out of the hole. When the string moves upward creates a swab pressure and it creates surge pressures when moves downward. They will reduce the mud hydrostatic pressure below the formation pressure and induce a kick if swab pressures are high enough. The formation can be fractured by high surge pressures and lead to circulation loss. It is always important to remove the drill string during the drilling operations especially to change the bit. For other purposes, such as for conducting desired logging operations, it may also be appropriate to remove the drill string. The drill string must return to the borehole after the bit is replaced or after certain logging operations are performed. The main aim of the thesis is to show the models with the affecting parameters of surge and swab pressures, to explore their effect on the fluid behavior models. The Bingham plastic model, the Power Law model and the Herschel-Bulkley model are utilized to get the best outcomes. Generally speaking, surge and swab pressures depending on the speed of tripping of the drill pipe, the geometry of the wellbore, flow regimes, rheology of fluid, and whether the pipe is close or open. Various flow phenomena, including eccentricity of pipe, geometric irregularities, and dynamic effects, are attributed to the increase in surge or swab pressure.