Title: Effects of Fluid Flow in Porous Cuttings Bed on Cuttings Transport Effeciency and Hydraulics
Author(s): H. Cho, S. N. Shah, S.O. Osisanya, The University of Oklahoma
Presentation: 2001 SPE Annual Technical Conference and Exhibition
Date:
September 30-October 3, 2001
Abstract: The study of effective cuttings transport and accurate prediction of drilling hydraulics has been a major concern for decades in the drilling industry. It is inevitable for deviation wells and long horizontal drillings to have a considerable amount of cuttings-bed in annuli. Common problems with most of the existing models are that they do not consider the drilling fluid flow through a cuttings-bed.
A new mathematical model is proposed to identify the effects of fluid flow in porous cuttings-bed and the differences of relative velocities between cuttings and carrier fluid on drilling hydraulics. The carrier fluid flows through the cuttings-bed, forming a porous matrix in which porous media itself is moving or stationary depending on the force balances. This model also considers the pressure losses of carrier fluid flowing through porous media in a cuttings bed layer. This paper specifically describes model development (including changes in axial forces in continuity and momentum equations due to changes in a deviated well angle), the solution, and simulation results. To ensure a comprehensive understanding of the effects of parameters affecting cuttings transport efficiency, a simulation of the hole cleaning mode is performed. This study enables to predict cuttings transport efficiency accurately, and to precisely estimate friction pressure losses in deviated wells (hole deviation angle: 30-60o), which have the most unstable cuttings bed characteristics.