Well collapse modeling & Norne & Heidrun well instability sensitivity studies

Abstract

Well collapse is a typical wellbore instability problem in brittle shale and unconsolidated formations. In this thesis, the thermal, chemical, mechanical, hydraulic, elastic and transient effects on the well collapse strength are studied. Single and combined parametric sensitivity studies of collapse pressure were carried out on two well programs, namely Norne and Heidrun. The result of the sensitivity study indicates that: • The most sensitive parameters were found to be the Biot’s coefficient, Poisson’s ratio and the water activity of the drilling fluid for steady state simulation and the uniaxial compressive strength for transient state simulation. • Parameters such as the coefficient of linear thermal conductivity, E-modulus, and the internal friction angle were found to be less responsive to collapse pressure. • The combined effect of chemical and transient state demonstrates positive and negative synergy depending on the osmotic outflow.