| A theoretical analysis of couette flow of power-law fluids for surge and swab pressure was conducted. Equations for both slot flow and concentric annular flow were developed for a stationary outer pipe and a steady axial motion of a concentric inner pipe. The inner pipe is assumed to be either: (1) plugged and of uniform geometry, or, (2) open at the bottom, and of non-uniform sectional geometry. The solutions of the developed equations for both the slot flow and concentric annular flow are presented in the form of families of curves which can be readily used by field personnel to predict the surge or swab pressure.;In order to use the charts presented in this study, one only needs to know the mud properties, hole and pipe geometry, and the pipe velocity. Numerical examples of the application of the developed equations are presented for both plugged pipe and open-end drill string. |
