Long-term stability study of open-hole completions in a producing hydrocarbon field

The use of open-hole completions in the design of production wells is a particularly appealing choice for oil companies, since it can ensure a huge economic advantage compared to conventional cased-hole completions. In order to assess the feasibility of such a solution, it is necessary to evaluate the mechanical stability of the rock surrounding the borehole not only in the drilling phase, but also over the stress and pressure regimes that the well will experience along its lifetime. By making reference to a case of industrial interest, the paper describes how the problem can be tackled through numerical simulation based on the Finite Element method. Proper mechanical characterization and initial stress conditions have been evaluated on the basis of in situ and laboratory results. Then, numerical simulations have been implemented accomplishing for a range of possible well trajectories and imposing the pore pressure evolution in agreement with the development scenarios. As an engineering result, a handy table reporting the stability lifetime for the analyzed reference wells as a function of trajectory and failure mode has been redacted, allowing for a fast identification of the safest well deviation and azimuth.