Hole Cleaning Evaluation And Hydraulics Optimization On Extended-reach Wells

This paper is based on the study of drilling fluid rheological model discrimination andcuttings transportation mechanism. Firstly, as the effect of drill string’s eccentric and rotationbeen considered, an annulus pressure loss calculation model on extended reach wells has beenbuilt. Secondly, combining with the cuttings transfer mechanism, an annular cuttingsconcentration calculation model has been established with the annular cuttings concentrationas an evaluation standard of cleanliness. Using the theory of solid-liquid two-phase flow andanalyzing mechanical balance of cutting bed and the start of cuttings particles, cuttingsparticles diffusion equation has been introduced and the a hydraulic model of three layers hasbeen established. Thirdly, combining with the characteristics of extended reach wells,modification and supplement to the traditional hydraulic parameters optimization theory havebeen made, and a set of hydraulic parameters design method suitable for extended reach wellshas been established.On the basis of the established mathematical models, a hydraulic parametersoptimization design program for ERW has been compiled using VisualBasic6.0. This programhas many functions, for example, general hydraulic parameters design, the hydraulicparameters of nozzle design, calculating circulating pressure loss and analysis of boreholecleaning, etc. With calculation examples, the hole cleanliness status of someone well has beenanalyzed, and sensitivity analysis of Influencing factors has been made. At last, we have got aset of power-law model and H-B model hydraulic parameters design results, and theconclusions are consistent with the experiment and the field experience.