The Establishment Of Optimization Model For Slimhole Drilling Hydraulic Parameters And Software Development

Due to the characteristics of small annular space and the high-speed rotation of the drilling string in the slimhole drilling,slimhole drilling and conventional borehole drilling has the very big difference in hydraulics. One of the important points is that the slimhole annular pressure loss was significantly higher than that of conventional well. The factors of drilling string rotation and eccentricity which influence the annular pressure loss can’t be neglected in slimhole annular pressure loss calculation. The conventional method of hydraulic parameters optimization is also can’t be fully applicable to the slimhole. Besides, the existing model for slimhole annular pressure loss don’t comprehensively consider the influence factors and the prediction accuracy is low. So it is urgent to set up a precise slimhole annular pressure loss model and the optimization model of the hydraulic parameters suitable for slimhole wells.Based on the research at home and abroad of slimhole drilling hydraulics data, the hydraulics difference between slim hole and conventional wells is analyzed; On the basis of annulus pressure loss calculation for conventional well, a new calculation model is deduced,which is applicable to many kinds of reheology models such as Bingham, power law, Herschel-Bulkley and so on and considers the comprehensive influence of drilling string rotation, eccentric, tool-joint, wall roughness.Then this paper analyzes the effect of different drilling fluid rheological model and other influence factors on annular pressure loss. Verified by measured data, it shows that the slimhole annular pressure loss model is with high accuracy; for slim hole well annular pressure loss is sensitive to the selection of drilling fluid rheological model, a new calculation method of rheological parameters and optimization method of rheological model are established; Finally the optimization theory of hydraulic parameters for slimhole drilling is perfected, and optimization model is established by optimizing the rheological model of drilling fluid, annular pressure loss calculation and the nozzle diameter calculation, and develop a software of hydraulic parameters optimization for slimhole.