Abstract
In downhole drilling systems, self-excited torsional vibrations caused by the bit-rock interactions can affect the drilling process and lead to the premature failure of components. Especially self-excited oscillations of higher-order modes lead to critical dynamic loads. The slim drill string design and the naturally limited drilled borehole diameter limit the installation space, power supply and lead to numerous potentially critical self-excited torsional modes. Consequently, small and robust passive damping concepts are required. The variety of possible downhole boundary conditions and potential damper designs necessitates analytical solutions for effective damper design and optimization. In this paper, two nonlinear passive damper concepts are investigated regarding design and effectiveness to reduce self-excited high-frequency torsional oscillations in drill string dynamics. Based on a finite element model of a drill string, a suitable minimal model based on the identified critical mode is generated and solved analytically using the Multiple Scales Lindstedt-Poincaré (MSLP) method. The advantages of MSLP compared to conventional MS methods are shown for this example. On the basis of the analytical solution, parameter influences are determined, and design equations are derived. The analytical results are transferred to self-excited drill string vibrations and discussed using time domain simulations of the drill string model.
Highlights
In deep drilling applications, unwanted vibrations can reduce reliability, lead to premature failures of components, reduce the drilling efficiency and increase nonproductive time
Daluloewtostdhierevcatriceotnycoluf psiootnesntaiablolyutcrtihteicadlymnaomdeicsa,fofefcdteridll bsytridnagmapnedrsd.aDmupeetromthoedevlasr(ie.tgy.,odf epsoigtennatinadllypocsritiocanl) manoddeths e(eb.go.u, nfrdeaqruyencocyndaintidonmsoidnedseheappde)r,ilolifndgr,ilsluscthrinangaalnydticdaalmsopluertimonosdaerlesdaensdigtnhaenbdouopntdimariyzacotinodniotifodnasminpderesepinddreilelipngd,rislulicnhgasnyastlyemticsa.lIsnoaludtdioitniosnarteo etshseenintivaelsftoigr athtieoneffoefcitnivfleudeensciignngapnadraompteitmerizsaotniotnhoefddyanmapmeircsminodtieoenpodfrtihlliendgasmysptemrs,s.thIne addition to the investigation of influencing parameters on the dynamic motion of the dampers, the analytical results are simulatively validated using self-excited drill string models
The equations derived from the analytical solutions with the aim of analytical results are simulatively validated using self-excited drill string models
Summary
In deep drilling applications, unwanted vibrations can reduce reliability, lead to premature failures of components, reduce the drilling efficiency and increase nonproductive time. Due to improved and new measuring tools, high-frequency oscillations have been identified as the cause of numerous drill string failures and have been intensively investigated over the last years with studies [9,10], simulations [8,11] and experiments [12,13]. The harmonic balance method [23,24,25] is one possibility to approximate nonlinear parts of a differential equation that has been used for drill string dynamic [22]. The harmonic balance method [23,24,25] is one possibility to approximate nonlinear parts of a differential equation that has been used for drill string dyn3aomf 2i2c [22]. Umsoindgest.hUe spirnegditchteivpercerditiectriivoen cdreitreivrieodninde[r8i]vaenddinde[t8e]ramnidnidnegttheermScin,kivnagluthee, the, BHvaAlucea, nthbeeBreHdAucceadntobearseidnuglceedmtoodaalsdinegglreeemoofdfraeleddeogmrereepofrefsreenedtionmg trheeprceristeicnatlinhgigthhefrcerqituiecanlcyhimghodfree.qTuheinscmy omdoadl ree. dTuhcitsiomnoodfatlhreedtourcstiioonnalodf ythneamtoircsioofnaadl driyllsntarimngiciosfdaedsrpiiltlestirtisncgoims dpelsepxiittey istsuictoamblpe,lebxeitcyaususeitawbhlee,nbeHcFauTsOe wochceunr,HmFoTsOtlyococnuer,cmriotisctalyl monoedcerditoicmalinmatoedsethdeoemnitniraetetosrtshioeneanltsiryestteomrsidoynnaal msyisctoemf thdeyBnHamAi.cInofatdhdeiBtioHnA, t.hIne laadrgdeitbiount, stlhime ladregseigbnuot fsltihme ddreislilgsntroinfgthweidthrilliltstlterianvgawilaitbhleliitntlsetaalvlaatiiloabnlespinacsetallelaatdiosntosploawcerleeaacdtisvteo eloffwecrtseaocftidvaemefpfeecrtss oonf dthame ptoerrssioonnatlhdeytonrasmioincaslodfytnhaemdircisllosfttrhinegd.riIlnl s[t8ri,n16g,.1I9n],[8a,1s6im,19il]a, ra reduction method was used to characterize downhole vibrations and in [5,19,22] ‘it is used to investigate vibration reduction strategies
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
