Simple Charts To Determine Hole Cleaning Requirements in Deviated Wells

Abstract

IADC Members Abstract Optimization of hole cleaning remain. one of the major challenges when planning and drilling high angle and extended reach wells. in this paper, a simple rig-site graphical technique is presented for determining hole cleaning requirements for a range of hole sizes. This method uses a set of charts which have been derived from a computer model based on both laboratory and field measurements. Access to the technology at the rig-site has been greatly improved by the development of the simplified charts. Examples are presented which illustrate how the charts can be applied to determine the influence of the major drilling variables on hole cleaning requirements. Mud rheology is shown to be a key variable for optimising hole cleaning in deviated wells. The charts can also be used to quantIfy the effect of hole enlargement which adversely affects hole cleaning. In addition, the paper discusses the detailed methodology behind the development of the charts from the original physically-based model. The charts presented in the paper are valid for the typical North Sea drilling conditions. Introduction When planning or drilling a deviated well, one of the key parameters which must be determined is the minimum flow rate required to transport drilled cuttings up to surface and keep the the hole clean. This minimum flow rate is called the critical flow rate (CFR). If inadequate flow rate is used, cuttings will settle on the low-side hole and form a large stationary bed which may result in severe drilling problems such as high drag and torque, hole packing-off and stuck pipe. All these may subsequently require expensive remedial operations and thus incur substantial increases in drilling cool, It Is crucial to know the CFR when planning and drilling a deviated well so that the adequate and economical drilling equipment can be selected and optimum parameters determined. This has become Increasingly Important over recent years as the demands of field developments have dictated more higher angle and extended-reach wells. Hole cleaning has been investigated by numerous researchers. In the early studies, the effects of a range of variables on cuttings transport and bed formation In deviated wells were investigated. The later studies have tended to concentrate upon developing mathematical models for predicting the CFR. Most of the models have been based on small-scale experiments. In a previous paper, a physically based model for predicting the CFR in deviated wells was pressed. This was developed based on the analysis of forces acting upon the cuttings and the associated dimensionless groups. The model was validated initially with experimental data obtained from an r wellbore simulator, and further validated with actual drilling data from six different sized holes from 8-½" up to 17-½". In this paper a set of charts is presented. These can be used by drilling engineers at the rig-site to optimise hole cleaning for drilling various hole sections of a deviated wall. P. 499^