Analysis Of The Drill Moment And Description Of The Window Shape For The Casing Side Tracking

Casing sidetrack drilling is an important means of improving the success rate of exploratory wells, oil-gas recovery and output in oil exploration and development process. This technology is a less investment and quicker returns on the increase of oil production. It can not only shorten the drilling cycle, but also save drilling cost. With the technology of casing sidetrack drilling, oil fields have carried out a variety of different types of well drilling construction side, and have achieved good results. Casing sidetrack drilling can make dead and old wells resurrection, and regulate and perfect well network construction; can enhance oil recovery, extend oil reservoir life, and improve final oil recovery; can take full advantage of the old wells, save construction investment, and protect the environment; also can gain new geological data to provide a basis of re-understanding of reservoirs.In the process of sidetrack drilling, the formation of borehole is the result of the interaction between drill bit and casing-wall as well as layer. Therefore, the meticulous and in-depth force analysis of the drill bit is of great meaning. In the past, when people analysed the bottom whole assembly, the force condition of bit was often just simplly processed. Usually the bit was considered as supported with a hinge and the displacement was zero. In this assumption, the drill bit has zero moment. Considering the actual drill bit size, shape and the operating fact, during the process of cutting window by sidetrack drilling, the drill bit must be subjected to the drill pipe, guided ramp device, casing, formation and other aspects of the role. Based on reasonable assumptions and combined mechanical analysis with drill bit, a mathematical model is established and the calculation is solved. The knowledge and understanding of the shape of the casing-window can guide the site construction and guarantee reasonable parameters application. Therefore, the analysis and calculation of window shape are of important practical significance. It provides a theoretical analysis to design operating width and length of the actual window, and also creats a good beginning for further sidetrack drilling. According to the theoretical analysis of window shape, not only is the general situation of the actual shape of the window indirectly recognized and understood, but also reference foundation is provided for reasonable selection downhole tools in the actual process of sidetrack drilling.