Research On Drillstem Mechanic Analysis And Extension Capacity Of Extended Reach Well

Extension capacity is an essential parameter in design and cunstruction of extended reach well, but it is always neglected. Whether the wellhole length exceed the drilling capacity need to been made sure. On the other hand, the research on which factors affect the extension of well trajectory of extended reach well is important. The drilling of extended reach well is related to the drill string stress, therefore to understand the extension capacity of the extended reach well, the research on drill string mechnics, especially the friction drag on the drill string of extended reach well need to be done. With the systematic research on these aspects, some results have been achieved in this paper.The researches on well trajectory design and calculation of extended reach well have been done. Through the analysis on the design category and principle of the extended reach well trajectory, the extended reach well design model and equations are introduced in this paper. The optimization model is proposed based on the consideration on well trajectory length, friction drag and cost. Besides that the obstacle detouring problem need to be taken into considerition in designing extended reach well. Double plane detouring obstacle well trajectory design theory and model are proposed in this paper to deal with complex situation and multi-obstacle detouring design. This theory does not have the limitation to obstacle quantity, shape or position and it provide an effective way to design and calculate extended reach well in complex situation.The research on drill string mechanics of extended reach well is done. Since drill string mechanics is unlinear, a drillstring static gap element mechanical analysis model for extended reach well is proposed to obtain the stiffness equation and solution based on finite element and gap element method. Boudary layer theory is used to analyse and calculate the torque and drag of drill liquid on extended reach well.The viabration of extended reach well is researched as well. Fratigue damage of drill string is the essential damage due to the drill string viabration. With the mechanical model for whole drill string, a mechanical model for drill string vibration analysis of extended reach well is built up and the solution to fatigue strength is given out.The research on extension limit of extended reach well is done. Considering the field drilling practice, the prediction principle of extended reach well extension limit is proposed based on the mechanical analysis on drill string. It shows that the extension of extended reach well is limited by the facters such as borehole friction coefficient, threshold weight, weight on bit, rotate speed, hole diameter enlargement rate, make up of string, etc.The research on drill string mechanics of extended reach well has practicability. It is not only corcerning with the mechanical analysis, but also the design and calculation of extended reach well. The research on extension capacity of extended reach well provides a reference to design and construction of extended reach well. With this application it is helpful to improve the oilfield economic benefit.