Drillstem Mechanic Analysis Of Slimhole Sidetracking Horizontal Well

A slimhole sidetracking horizontal well has the characteristics such as small size, lowrigidity, and poor anti-torsion ability. Friction and torque increases sharply due to the highcurvature, small annular tolerance, and the difficulty of cuttings bed removing. Pipe-stucking,if happened, is very difficult to deal with. These problems bring about severe challenges tothe drilling process and later work. Therefore, on condition that meeting the boreholetrajectory need, how to reduce friction drag, torque and the possibility of the drilling toolproblems is the key of drill string mechanics analysis, which is also very important for welldrilling design and drilling construction.Different borehole tracks will have different effect on drillstem mechanics analyticalresults. This paper firstly has researched the wellbore trajectory design and calculation ofslimhole sidetracking horizontal well, expounded and analyzed the preparation work ofslimhole sidetracking, conducted the common slimhole sidetracking horizontal well2-D and3-D wellbore trajectory design and calculation. Because the well deviation and azimuthdrifting law is difficult to master due to small size in real work progress, this paper hasconducted the forecast and calculation of true wellbore trajectory, by3-spline interpolationmethod. The true wellbore trajectory has fit and gained any point coordinate calculation oftrue wellbore trajectory; in order to realize safe and fast drilling, safety of drillstem in anyconditions, this paper has analyzed and researched static stress of drill string in slimholesidetracking horizontal well. The drill string mechanics analysis model has been established,the drill string mechanics equations has been calculated and the detailed solving methods ofthe established drill friction and torque model have been provided. Meanwhile, it alsoanalyzed the dangerous cross-section stress, on the basis of the fourth strength theory,strength calibration and safety analysis of drill string have done, thereby, ensured the safe andfast drilling underground. Field practice indicates that the research in this paper is beneficialto the design and safe construction of slimhole sidetracking horizontal well, and it hassignificant application value to improve the whole economy of oil field.