EFFECT OF RHEOLOGY ON OIL WELL PLUGGING PROCESS

The process of oil well plugging is largely used in oil industry. In this process, a cement plug (higher density fluid) is placed over the drilling fluid (lower density) to seal and abandon the well. The success of the operation depends on several aspects, such as the density ratio and the rheology of the fluids. A numerical analysis of the transient flow just after the cement placement in vertical wells is performed, using Fluent software (Ansys Inc.). The conservation equations of mass and momentum are solved using the finite volume technique. The volume of fluid method is used to deal with the multiphase flow cement / drilling fluid. Both the drilling fluid and the cement paste are viscoplastic liquids, modeled by the Herschel-Bulkley equation. The analysis of flow displacement and interface configuration between these fluids is an important tool for the process optimization. The effects of the density ratio and yield stress on the flow pattern are investigated. It is shown that the flow is highly unstable and that the above mentioned parameters strongly affect the process.