Effects of Fluid Flow in a Porous Cuttings-Bed on Cuttings Transport Efficiency and Hydraulics

摘要

The study of effective cuttings transport and accuraternprediction of drilling hydraulics has been a major concern forrndecades in the drilling industry. It is inevitable for deviatedrnwells and long horizontal wells to have a considerable amountrnof cuttings-bed in the annuli. Common problems with most ofrnthe existing models are that they do not consider the drillingrnfluid flow through a cuttings-bed.rnA new mathematical model is proposed to identify therneffects of fluid flow in porous cuttings-bed and the differencesrnof relative velocities between cuttings and carrier fluid onrndrilling hydraulics. The carrier fluid flows through therncuttings-bed, forming a porous matrix in which porous mediarnitself is moving or stationary depending on the force balances.rnThis model also considers the pressure losses of carrier fluidrnflowing through porous media in a cuttings bed layer. Thisrnpaper specifically describes the model development (includingrnchanges in axial forces in continuity and momentum equationsrndue to changes in a deviated well angle), the solution, andrnsimulation results. In order to ensure a comprehensivernunderstanding of the effects of parameters affecting cuttingsrntransport efficiency, a simulation of the hole cleaning mode isrnperformed. This study provides a method to predict cuttingsrntransport efficiency accurately, and to precisely estimaternfriction pressure losses in deviated wells (hole deviation angle:rn30 to 60 o ), which have the most unstable cuttings bedrncharacteristics.