Advancements in Annular-Pressure-Buildup Mitigation for Thunder Horse Wells

Abstract

SummaryA wide variety of annular-pressure-buildup (APB) -mitigation techniques has been deployed in the past 2 decades. In the early 2000s, BP focused efforts on the development and implementation of rupture disks, nitrified foam spacers, syntactic-foam modules, and vacuum-insulated tubing (VIT). Initiatives to simplify operations while maintaining well integrity have led to innovative techniques that expand the APB-mitigation toolkit.BP's Gulf of Mexico (GOM) Thunder Horse drilling team recently pursued three APB-mitigation techniques. One method is to fully cement the annulus, thereby removing the fluid that is subject to thermal expansion in a trapped annulus. A second method uses a qualified port collar to equalize pressure across a casing string. The third method focuses on better acquisition and use of mud pressure/volume/temperature (PVT) data for a more precise prediction of the APB-design loads.These methods and techniques have led to the removal of syntactic foam from some wells in the Thunder Horse field. The design change reduces installation time and operational complexity during well construction and abandonment.This paper provides a description and technical details concerning the planning and job execution for the fully cemented annulus and the use of port collars for pressure equalization. It also discusses the motivation behind acquiring PVT data specific to a particular mud system, and provides interpretation of laboratory data. The work may be useful for other operators as they plan and execute wells subject to the potential for APB.