Evaluation And Forecast Of Lengthwise Vibration Fatigue Intensity Of Deep Well Drillstring

The whole drillstring is taken as research object in this paper. Mechanics model for lengthwise vibration analysis of deep well drillstring is established. Deep well drillstring is scatter to umpty dimensional beam unit along axes. Lengthwise vibration equation of whole drillstring is found with three-dimensional dynamic finite element method. With this equation and improved Ritz Vectors, dynamic response analysis and calculation of drillstring is carried out, also, the method of vibration model splice is used. In the model, the influence of friction damp between drillstring and well wall is taken into account, as well as paste damp of slop and structure damp. On this basis, fatigue intensity condition of deep well drillstring is established, which provides theoretics gist for the mensurable evaluation and forecast of fatigue intensity of drillstring.Lengthwise vibration and fatigue intensity analysis software of deep well drillstring is worked out with Delphi Language. With theories listed above and the software , according to the engineering design of No. ShengShen 7, No. LinShen 2, No. MiaoShen 1, No. ChaoShen 5, No. SongShen 101, the evaluation and forecast of lengthwise vibration and fatigue intensity of the drillstrings in which are carried out. The analysis shows that the results from the software and practical measurement are inosculated. Fatigue intensity and safety assessment of drillstring can be analyzed and predicted not only in the course of engineering design before drilling with this software, but also after drilling. It is helpful to the analysis of rupture accident, as well as to advance improved measure. The software is valuable in engineering.