| Resumo : |
The present research exposes one and two-dimensional numerical phase change analysis performed to investigate the melting and solidification processes through a multi-layer hollow cylinder medium. Furthermore, this work performs a quantitative study of the application of a new Plug and Abandonment (P&A) technology using a thermite chemical reaction to generate heat and melt one or more layers of a singular annulus well structure. Ideally, a cylindrical container filled with reactants should descend to desirable depths (usually placed at the geological sealing height) along the borehole and be ignited in order to start an exothermic chemical reaction. The resultant temperature fields and the distance traveled by the phase change front will be determined by application of the Eulerian Multiphase approach and Volume of Fluid Method - VOF (a surface tracking approach used in a fixed Eulerian mesh) applied by means of Star-CCM+® commercial code. The solution is developed by solving the energy equation (for static phase change investigated cases), momentum, and continuity equations (in the higher complexity investigated cases) for each phase as well as calculating the respective liquid volume fraction at each layer by the applying the enthalpy method. Thermal properties and heat flux profiles are assumed to vary with temperature and time (depending on referenced data availability), respectively, in order to enhance realism and increase solution accuracy. The main objective of this study is to relate the input data that describes the heat generated by the thermite reaction over time to the output temperature profiles and liquid volume fraction scalar as parameters that describe the overcoming of the design melting point of any of the cylindrical layers, thus creating a well seal mainly composed of an iron-aluminum reaction product. This new technology may represent a great achievement for the oil industry, since the thermite tamponing method can become an alternative to traditional cementation techniques for abandoning offshore wells, as well as building a path to new financially attractive operations such as the removal of the production column by fusion, which can reduce the time required to conclude tamponing activities. |