Analysis of drilling fluid flow in the annulus of drill string through computational fluid dynamics

Abstract

During an oil and gas well drilling the drilling fluids are pumped through the drill string to cool and lubricate the drill bit. This also serves the purpose of bringing the rock cutting back to surface and serves various other purposes also like pressure control and maintain well bore stability. As the well is drilled the casing are lowed from the well from caving in. This results in a situation where there is an annular flow of drilling fluid where the inner pipe is rotating while the outer pipe is stationary. The understanding of fluid dynamics of such situation is extremely important and detailed investigations are required. Though experimental investigation will reflect the actual behavior but with the advancement is the numerical techniques such experimentation can be avoided with the application of computational fluid dynamics. Therefore, the present study employs the homogeneous model to simulate a single-phase fluid flow and predict pressure loss variation in eccentric vertical annuli as a function of varying drilling parameters: fluid velocity, inner pipe rotation speed

Three-dimensional nonlinear coupling vibration of drill string in deepwater riserless drilling and its influence on wellbore pressure field

“…Krishna et al studied the influence of the axial movement of the drill string on downhole pressure fluctuation during the tripping of the drill string and found that with the increase of the tripping speed, the diameter ratio had a significant influence on the differential pressure [15]. Joshi et al estimated the influence of eccentricity on annular pressure loss through numerical simulation, and the results showed that the pressure loss was directly related to the inlet velocity and rotational speed, and the pressure loss of concentric tube was smaller than that of fully eccentric tube [16]. Wang et al established a coupling model of offshore platform, heave compensation and drill string axial vibration, to analyze the influence of drillstring heave motion on bottomhole pressure, and found that the upward movement of drill string would lead to the decrease of bottomhole pressure, while the downward movement would lead to the increase of bottomhole pressure [17].…”