Buoyancy-driven flows of two immiscible Newtonian liquids in a vertical tube
Priscilla Ribeiro Varges1; Fernanda Nascentes1; Paulo Roberto de Souza Mendes1; Mônica Feijó Naccache1; Bruno da Silva Fonseca1
1 PUC-Rio
doi:10.20906/CPS/COB-2015-1805
Resumo
Plug cementing is an essential operation performed under a variety of well conditions. In general, cement plugs are set for the following four purposes: sidetracking, lost-circulation control, zonal isolation, and well abandonment. Placing properly cement plugs is a difficult task to oil industry for decades. The cement plugs rarely are found at the intended depth because the cement slurry usually is heavier than the well fluid. Failures are due primarily to migration of the denser fluid downward through the well fluid upon which it is placed. If the displacement occurs in excess, a contamination between fluids will result in an unsuccessful operation. The aim of the research reported in this paper is to develop an understanding of the process of plugging operation in vertical wells. To this end, we performed an experimental and theoretical study of the buoyancy-driven flow of two immiscible Newtonian fluids initially placed in a vertical tube such that the heavier and more viscous one is on top. Since both fluids are Newtonian, the situation is always unstable. i.e. the fluid on top will always flow downward and displace the bottom fluid upwards, so that the relative positioning tends to invert. The influence of the governing parameters on the interface stability and on the speed of inversion was investigated. Flow visualization was performed with a digital camera, and inversion velocities were obtained through image analysis. Preliminary results show that inversion speed decreases as the tube diameter is increased, increases as the viscosity ratio is increased, and also increases as the density ratio is increased.
Palavras-chave: Cement plug; Buoyancy-driven flow; Interface stability; Speed of inversion