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The paper focuses on application of multibody system approach for the torque and drag analysis of long drill strings. The approach is used to get improved results as compared with those obtained by soft-string models. The analysis is carried out by integration of equations of motion of the drill strings till reaching equilibrium under externally ap...
Citations
The cost and security of ocean drilling are directly related to the efficient exploration and development of ocean resources. The riserless drilling system is usually adopted in the ocean drilling. With the consideration of marine environment load, a dynamic analysis model of drill string in deep-water riserless drilling is established. This model aims to analyze the dynamic characteristics of drill string in the water and down hole during the process of deep-water riserless drilling. The research results are as follows. For the drill string in water, its displacement increase with the increase of ocean current velocity, water depth, rotation speed, and WOB. But the rotation speed and WOB have less influence. The drill string in down hole shows the same pattern. However, the drill string in down hole is only affected near the mud line and the bit, and the rest of the drill string is almost unaffected. In deep-water riserless drilling, stress on the drill string at the wellhead, near the mudline, and at the bottom hole assembly (BHA) is complex. The safety of drill string at these locations should be given great attention.
The study object is a “wheel - rail” system. The subject is the computer simulation of the system elements wear. The work objective is to investigate the wheel and rail wear dependence on the kinetic performance parameters. The problems solved here are analysis of the earlier proposed mathematical functions describing the kinetic performance for the presence of extremes, the functional behavior (growth, decrease, monotonicity, and unimodality, etc.) in various parameter ranges; implementation of the computer simulation of the wheelpair movement by rail with the quantitative estimation of the wheel and rail wear with various kinetic performance parameters; to determine qualitative influence patterns of the kinetic wear performance. The simulation is fulfilled by the software package “Universal Mechanism”. As a result, values of various characteristics related to wear (power, total and specific friction work) under different conditions of the kinetic friction performance are obtained. The conclusions are as follows. The kinetic friction performance parameters must be considered as they can significantly affect the wear within the range of the actual operating conditions in the course of the computer simulation. Under some conditions, there are cases when an increase in the friction coefficient is accompanied by a decrease in depreciation. It is proposed to continue the research in two main areas: determining the influence patterns on the kinetic friction performance and wear of the multiple actual factors, and studying the dynamic (at variable slip velocity) feature of friction effect on the parameter wear through the same procedure.
