Simplified Predictive Model for Downhole Pressure Surges During Tripping Operations Using Power Law Drilling Fluids

Abstract

<jats:title>Abstract</jats:title> <jats:p>Surge/swab pressure is a crucial parameter that provokes well-control problems such as fluid loss, fractured formations, fluid influx, and kick. Thus, a precise estimation of differential pressure is required to evade any unforeseen drilling difficulties. The existing predictive models are based on narrow-slot approximation methods and consider the effect of drilling string axial movement on downhole pressure surges. However, it ignores the impact on the boundaries of the annular fluid velocity zone by the tripping velocity. In this research, a simplified model is developed using the flow velocity profile generated in the annulus by the tripping operation and the concentric annular Couette fluid flow phenomena for power-law fluid. A comparative study is performed with the existing analytical models and the experimental data to validate the developed model. The obtained results are convincingly in good agreement with the analytical and experimental data. A parametric study is performed to identify the effect of various parameters on surge/swab pressure. It is found that the diameter ratio has a significant impact on pressure differential with the increase in the tripping velocity. The fluid behavior index exhibits a considerable effect, and fluid consistency index shows a minor effect on the surge pressure gradient. The simplified developed model requires less numerical analysis to determine the outcomes for varying industrial applications, especially petroleum drilling operations.</jats:p>

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

“…( 14) and Eqs. (15), the 3D nonlinear coupling vibration governing equations of the drill string system can be obtained and written as:…”

“…It was found that drill string eccentricity reduced the frictional pressure loss more significantly under high diameter ratio conditions [14]. 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].…”