With A Kinetic Mechanism Of Drill Stem Failure. Piedmont Nappe Study

Piedmont tectonic belt of the west region where there is the favorable condition of petroleum formed. However, the accident of drill string damage happened easily in the overthrust nappe belt of these regions in the drilling. The paper bases on the circs of the quiet a few accidents of drill string damage in the piedmont nappe belt. A accomplished well in the YanQi basin is regarded as the study object. The study content as following:Firstly, the datas of drill string damage is analyzed. The drilling datum in this well is collected and analyzed. The analysis indicates that the damage position of drill string focuses on the compression position of BHA. The master reason is the harder rigidity of the formation rock, and the badder drill ability of rock, and the better rock abrasiveness. Drill string receives the complicated stress which is tension-compression stress, torsion stress, bending stress, etc.Secondly, the different model bits affect the rule of the vibration sources, which is studied. The rock rigidity, the rock abrasiveness, and the drill ability of rock of the studied formation rock patterns are determined by having experiment. On the basic of analyzing these parameters, the table-plate test of the different model bits chiseling in the granite is done in indoor, The result indicates that the bit structure affects at first hand the undulation of the bit weigh. In the same formation condition, the undulation swing of the bit weigh which the soft formation brings is bigger than those the soft formation brings. The undulation scope of the bit weigh can change with the changing of the bit weigh, but the average of the undulation and the average of the bit weigh are unconverted. The weight of bit is looked as the bottom vibration sources in the instant dynamics analysis of the BHA.Thirdly, the modality analysis and the harmonic response analysis of the holistic drill strings are done. The dynamics finite element model of the whole drill string is founded. The natural frequency, the response displacement and the response axial force of drill string are calculated. The result indicates that the reasonable emplacing position and the amount of the vibration damper which has the obvious effects for debasing the response displacement and the response axial force of the drill string axial vibration.Fourthly, the instant dynamics analysis of the BHA is carried through. The mutative bit weight is looked as the bottom vibration sources. The action of the wellbore and the drilling liquid is considered. By the transient dynamical finite element analysis, the coupling vibration character of the axial vibration and the transverse vibration is studies primarily. The stress distributing and the distortion circs of drill string are known. The...