Torque Analysis And Extension Limit Study Of High-angle Well Friction

With scarcity of resources,great difficulties have been confronted with oil companies during the process of exploration drilling of oil or gas and the complexity of drilling geological environment is now bottlenecking the development of drilling technology.In recent years,the reach of highly-deviated wells has increased releasing itself from complexity geographical conditions and it provides a larger producing of low porosity and low permeability reservoir.When highly-deviated well drilling,drilling string works in a very complex stressed environment down hole,abnormal vibration frequently happens,the stress of bottom drill string near the bit instable changes with large amplitude fluctuating by dynamic load,stress intensity in the drill string due to the cycle load results in decrease of metal fatigue life.The construction is quite difficult which is often caused by designed path has a great deviation angle and long open hole interval.Frequent contact-rubbing between bending drill string and bore hole wall has developed great friction,it put forward the higher requirements to drilling equipment.At the same time,it influences the transmission of drilling string axial load reducing effective Wob on the drill bit、torque,then drilling rate always is decreased,seriously restrict extension limit capacity of drilling tools.Overall,the research on calculation of torque and drag should be deeper and wider in highly-deviated wells,resulting in a lot of errors in the torque and drag parameters computed,which has demonstrated a significant gap against oil exploration and development with the increasingly rigorous situation,so the drill string dynamics and the contact or friction of drill pipe with borehole wall under the drill string action of dynamic are need more attention and urgent research work,its purposes is to study the drill string vibration rules and the reasons of drill string failure in highly-deviated wells,especially to understand the law of torque and drag and promote the development of new drilling technologies in special technology.Research on the status and application of relevant domestic and foreign drag and torque,in view of the above-mentioned problems commonly exist in highly-deviated wells,three-dimensional nonlinear dynamic model and dynamic friction torque model were established in highly-deviated well have been developed base on full-hole system dynamics,in which the finite element method is used to model the drill string used in rotational drilling operations,using cubic spline curve interpolation method to restore the initial configuration of borehole,the rubbing mechanism of the drill string and borehole wall in highly-deviated well is studied.Numerical simulation calculation method are adjusted and optimized in order to using dynamic drag and torque model to study friction torque characteristics in highly-deviated well,dynamic mechanics parameters of rotation drill string is studied systematically,friction torque of drill string under the service condition was evaluated systematically.The evaluation methods and indicators of drilling limit extension for highly deviated wells are established based on the dynamic friction torque model,then the ultimate extension drilling ability of the drill string is obtained.The results show that those models established in this paper have a complete adaptability for a complex three-dimensional borehole trajectory.For the actual well application,it will help to recognize the contact or friction law of drill pipe with borehole wall and evaluate security performance of drill string in complex working conditions.