Drillstem Mechanic Analysis Of Horizontal Multi-branched Well

A 3D model of horizontal multi-branched well borehole trajectory design has been established and a mechanic model of drillstring has been built up with the static force balance theory through differntial equations in this paper, With which the mechanic analysis and checking could be done to ensure the safe and effective operation in raising and lowering the drillstring.With the research on the horizontal multi-branch well trajectory design, the essential parameters calculation method could be achieved and the branched-holes design could be optimized with the analysis to the relation between main hole and branched holes. With the design theory of inclined plane, the 3D horizontal branched wellbore trajectory design calculation method has been achieved.Using flexed beam theory to analyze wellbore deformation of horizontal multi-branched well, and the calculation model of flexure line and street corner of drill string with different horizontal uniform load, horizontal concentrated force and end load is got, meanwhile the diagnostic condition of contact angle is got.According to the complexity and peculiarity of horizontal multi-branched well, considering the stress of drill string and contact character, a mechanic theory that applied drill string of horizontal multi-branched is built.With the research on the mechanic analysis of the horizontal multi-branched well, the drag/torque model of drill string could be established and the method for calculation of other mechanic parameters could be achieved. The stress of drill string in various conditions for the main hole and the branched holes has been analyzed to ensure the safe and fast drilling. In order to prevent the drill string damage on the dangerous section, the section stress analysis has be done to achieve the checking method to the string strength with the fourth strength theory. The safety analysis to the tensile strength, wrest resistant strength, axial load, buckling deformation and friction torque of the horizontal section and branched sections has been done to insure the safe operation to reach the target. With the mechanic analysis to the field application of the horizontal multi-branch wells, it shows that the solution has great realistic significance to field operation.