TOT-3P Design: Technical Fluid Solutions for Producing and Injecting Wells

Abstract The TOT-3P concept was developed to optimize the construction of post-salt wells, including drilling three sections and installing the completion assembly in a single trip. This work presents the technical fluid solutions developed to enable this scenario, with extensive application in the Marlim Revitalization project, considering the challenges associated with the presence of an extensive section of shales followed by a sandstone reservoir, as well as the specificities of the producing and injecting wells. The proposed technical solution aimed at enabling the construction of TOT-3P wells in post-salt fields consists of using an oil based mud for the drilling of the final phase and a solid-free oil base mud in the completion stage. These fluids were developed with the purpose of providing sufficient chemical inhibition to the shale and minimizing damage to the sandstone reservoir. Additionally, a drilling strategy using a water based mud system is being developed for the construction of injecting wells, as the required injectivity in these projects is incompatible with the successful oil base muds alternative adopted for producing wells. The use of oil based mud in the drilling of the final phase and completion stage has provided excellent performance for the execution of producing wells by reducing rock-fluid interactions, thus minimizing the risks of collapse and swelling of wellbore walls that can result in operational issues during drilling and completion operations. Additionally, completion with solid-free oil based mud helps mitigate formation damage caused by fluid base exchange and prevents equipment and valve blockages. The development of a water based mud system presents itself as a suitable alternative for injecting wells, as it allows for traditional completion with saline fluid and promotes the formation of an acid-soluble filter cake during drilling, favoring the required injectivity for these projects. The experiences obtained through the implementation of this strategy in the field have shown that, despite some operational impacts, it is possible to successfully complete the drilling and completion stages without abnormalities. The future vision for injecting wells involves the possibility of using filter cake breakers that enable drilling with an oil based mud and completion with saline fluid, combining the significant operational and economic advantages of using these two fluids. This work has developed technical solutions capable of enabling the drilling of an extensive shale followed by a sandstone reservoir in producer and injecting wells, through the development of a solid-free oil based mud for completion and a strategy for the use of a water base mud system. In addition to enabling a faster and more cost-effective well design for mature post-salt fields, the application of these solutions can be evaluated for other well construction scenarios.