Flow-Rate Predictions for Cleaning Deviated Wells

Abstract

ABSTRACT A new physically based model is described in this paper which has been developed based on the analysis of forces acting on the cuttings and the associated dimensionless groups. The model can be used to predict the critical (minimum) flow rate (CFR) required to remove, or prevent the formation of, stationary cuttings beds on the low-side of the wellbore in deviated wells. The model has been validated with the experimental data obtained from an 8″ wellbore simulator located at BP Research Centre Sunbury, and with field data from 8-1/2″, 12-1/4″ and 17-1/2″ holes. By using the model, the effects of major drilling variables on cuttings transport are evaluated and compared with experimental and actual field data. The results show that the model accurately predicts the effects of the major variables such as: hole angle, penetration rate, mud properties and flow regime. In particular, the model provides a mechanism to support the use of both low and high viscosity pills, and mud low-shear enhancers - which have been widely used during drilling operations to improve hole cleaning. The model has been incorporated into a computer program which can predict the CFR under the specified drilling conditions. A series of simplified hole cleaning charts have also been developed which enable the optimum hole cleaning parameters to be determined at the rig-site.