A key objective for any completion process is to avert troubletime and minimize unplanned events. The novel cleanup systems discussed in this paper were designed to work within the planned completion program, which means they do not need special tanks, lines, or equipment. One of the cleanup systems acts as its own spacer and can also be used to displace oil-based mud (OBM) from the wellbore. The system provides a delay so that operations can proceed and subsequently clean up the residual filter cake. The other system is a brine-based system that also provides a delay. Both have been successfully applied to production and injection wells. Developers of the systems gave consideration during the R&D process to optimizing openhole displacements. This paper discusses the engineering and chemistry of both systems with respect to providing a "delay" so the completion can proceed as planned.

System development in both cases included testing and simulations performed to meet pre-planning criteria that included the need to effectively displace the lateral section while maintaining positive well pressure during the completion phase. Other critical criteria were effective cleanup of the residual OBM filter cake and the ability to mitigate system upsets upon initial production.

Field results presented in this paper are from several recent openhole completions offshore Cabinda, West Africa, where the new cleanup systems were applied to alleviate post cleanup of OBM filter cakes. The paper also explains the engineering of the displacements, impact on the completion operations phase, and the production results.

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