Analysis of bending moment on the bit in sidetrack drilling

In the process of reservoir development, so as to achieve the purpose of enhanced oil recovery, many reservoirs applied sidetrack techniques and had achieved remarkable economic benefit. In the past, the stress analysis of the bottom hole assembly is indicated that the drill bit is hinged and no moment with formation. However, in the actual operating environment of drilling, the drill bit keeps touch eccentric with casing and formation, there must be moment on the drill bit. Therefore, given some of reasonable assumptions, the mathematical model is established through the method of numerical integration. The software of mechanical analysis is developed with Visual Basic 2008. At last, an application to field is provided. The results show: bending moment on the bit is gradually changing process with the drilling progress, the value of the moment is relatively large when the bit beginning to touch with the casing, with the contact area increasing, which will be reducing gradually. It is easy to know that bending moment on the bit is zero when the bit is completely in the formation.