Sistemas de pastas de cimento com filtrado ultra controlado para aplicação em poços com riscos de migração de gás

Abstract

In a process of cementing oil wells, we must consider several factors in the formulation of a cement slurry. One of the most studied factors is the migration of gas, however, there are still doubts about its causes, and how to solve them. Most of the problems involving gas migration can range from simple remediation (which has a high cost) to a blowout, which can cause irreparable damage, as in the case of the accident at the “Deepwater Horizon” field in 2010 in the Gulf of Mexico. Faced with these accidents, researchers are constantly developing new technologies to prevent gas migration, such as the addition of fluid loss controllers, where they realized that the slurry’s viscosity increased, helping to control gas migration. According to the scenario described above, in this project we use the fluid loss controller together with the SBR latex to control gas migration. As the two additives influence the increase in the viscosity of the slurry, we added dispersant so that there is no problem in the pumping of the slurry or in its dehydration. Thus, this work aims to develop cement slurry systems with ultra-controlled filtrate, for application in wells with risks of gas migration. We fix the concentration of the fluid loss controller and vary the concentration of latex and dispersant. With the increase in the concentration of latex, there was a decrease in the volume lost by filtration and, consequently, an increase in gas control. However, after the 1.5 gpc concentration, the latex formed a solid that made it impossible to add the cement, and to carry out the rheology and filtrate tests. This increase in viscosity is due to the fact that the latex particles are intertwined, as well as forming a polymeric film that buffer the channels and restrict the percolation of water and/or gas. In view of the results and the literature, we can infer that the latex has the capacity to be an ultra-controlled fluid loss agent, but for that, it is necessary to adjust the formulations, because, according to the literature, an ultra-controlled fluid loss agent must reach values of API filtrate less than or equal to 25 mL/30 min.