Análise do desempenho de plugues de bentonita como barreira de segurança em poços de petróleo offshore.

Abstract

Bentonite pellets are an alternative to the use of cement plugs in the abandonment of oil wells, due to their advantages that include economic, environmental and safety and health aspects, in addition to being more reliable due to the plasticity of the material. However, its application in offshore wells requires the careful evaluation of several factors, such as the adequate disposition inside the well through an appropriate displacement fluid and the contact with formation fluids. Thus, the present study aimed to evaluate the performance of alternative barrier elements, obtained from bentonite pellets, aiming at the future integrity of offshore oil wells. For this purpose, the methodology used involved five steps: in the first, the pellets were characterized by means of X-ray diffraction (XRD), cation exchange capacity (CEC), specific area (SA), thermogravimetric analysis (TGA) tests. and differential thermal analysis (DTA); in the second stage, the behavior of the pellets in relation to swelling and expansion was evaluated; in the third, plugs were obtained and their mechanical behavior were evaluated through compressive strength and adhesion tests using the Haake Mars 60 rheometer; in the fourth stage, diesel and olefin were evaluated as displacement fluid; and, in the fifth stage, the resistance of the plugs to formation fluids was evaluated. The results indicated that the bentonite pellets have great swelling and expansion capacity, which is essential to obtain an effective seal and that the plugs formed by bentonite pellets showed satisfactory mechanical strength and adhesion, as well as resistance to formation fluids. In addition, the plugs formed by these pellets showed satisfactory mechanical strength and adhesion, as well as the ability to resist formation fluids. These discoveries highlighted the potential of bentonite pellets as a sealing material in oil wells. In addition, it was indicated that diesel can be used as a displacement fluid in the abandonment of offshore wells.