Drill String Finite Element Analysis On Coupled Vibration Of Direction Well

With the development of oil field, the continuous development of drilling technology, the traditional drilling methods can't meet the demand of current development in oil fields. And directional, horizontal and extended reach drilling have been widely applied in oil exploration and exploitation. With the rising well types, the changing ground and underground environment, the demands for the mechanical analysis and calculation of drillstring are increasing high, which relates to the success of the successful completion of wells. In the process of drilling direction wells, because of borehole trajectory being in the state of irregular changes in three-dimension space, the situation of drilling string lateral vibration during drilling are varied, which in severe cases may cause accidents such as bit bounce, drill string failure and so on, so it is necessary to study drillstring vibration of directional well and the problems can be satisfactorily resolved. The study is very important to directional well design and drilling tool optimization. The paper obtains some research achievements.First, the paper studies characteristic of directional well types in the drilling process, and Finite element theory. Combining with trajectory characteristics of directional well and the finite element theory, which is applied to analysis of drill string vibration, we can obtain the drill string vibration rule.Second, the paper according to characteristic of directional well types scatters drillstring, and a general model is developed to analyze drill string vibration considering the relations between longitudinal vibration, lateral vibration, and twisting vibration, with coupling the element matrix and solve full-hole coupling vibration characters.Taking into account the existence of conditions of drilling fluid, the drill string vibration regulation changes are analyzed,and coupled vibration rule of the drill string is obtained.Finally, Delphi was used to developing drillstring coupling vibration software, the software features vibration frequency, intensity and so on. The software interface is friendly and easy to operate. It has been applied in five wells at a drilling company, which can meet the drilling design requirements and satisfy the need of construction requests.The study of this paper has strong significance and usefulness for mechanics analysis in drilling operations of directional and horizontal wells, the research results can supply a reliable theoretical basis for drilling operations of directional wells. The study has important realistic significance and certain practical value in improving the field economics.