Nonlinear Mechanic Analysis And Application Of Drillstring For Stairs Horizontal Well

The nonlinear static mechanic model of drillstring is established according to the whole drillstring, the gap between the drillstring and hole wall, the contact state and hole curvature and so on . This model can comparatively accurately describe the force and deformation state of drillstring. Meanwhile, aiming at this nonlinear mechanics problem that the contact between drillstring and borehole wall occurring randomly at different depth of well and different circumference directions, "multi direction gap element"and spatial beam element are taken to do nonlinear finite element unit analysis of drillstring. The method of calculating the critical rotate speed of rotary table is established at the base of finite work time of drill tools ,which is calculated by use of the mechanic analytic result of whole drillstring and the material and the structure of drill tools. According of researching nonlinear finite itoration method, "node displacement coupling"idea is a beneficial grope for accelerating constringerncy. In view of inclining capability of motor tools in horizontal well, taked inclination and azimuth of start point's and end point's in the stairs horizontal segment as the controlled factors and take vertical depth or closed distance as restricted terms, three dimension well trajectory planning mathematical model and calculating method in stairs horizontal well is presented. With "mechanic static analysis and trajectory planning for the stairs horizontal well"software compiled by Delphi software, the user can analyze the friction and the strength of drillstring to evaluate the passing ability of drillstring through mechanics analysis of whole drillstring, calculate critical rotate speed of rotary table to guide drilling and design two spatial curves for up-down ,steering clear of obstacle and spatial target in the stairs horizontal well through different drill components. Through application to eight stairs horizontal well at Daqing oil field, it can get the well trajectory with short closed distance and low cost at drilling, evaluate the passing ability of the drillstring which the user choose, and that validate the accuracy and reliability of the model and the theory. This software offer a applied technical method for reasonably planning drillstring makeup ,calculating critical rotate speed of rotary table and planning well trajectory of stairs horizontal well.