World's Largest Non-Traditional Packer with Extreme Annulus Sealability

The historical use of packers in the oil and gas industry has primarily involved elastomers with hydraulic or mechanical operating systems. Bismuth alloy technology offers an alternative material with a distinct operating system. TDAP stands for thermally deformable annulus packer which is a non-traditional seal that aids in sealing leakages in an annulus with Sustained Casing Pressure as a preventative solution before the pressure is observed at the surface. The technology was developed with extensive lab, yard, and field testing to prove the reliability of this alloy, particularly for larger annulus spaces, such as 9 5/8″ × 13 3/8″. The objective is to proactively eliminate the risk of Sustained Casing Pressure (SCP) in the production and intermediate casing annuli. The method used to demonstrate this system's applicability involves having bismuth alloy disks on the exterior of one joint of the 9 5/8″ casing. The joint is positioned to achieve the intended depth for the packer. The packer is set above the 13 3/8″ shoe. After cementing, the disks are turned into a liquid using a heater run inside the 9 5/8″ casing. This heater is precisely controlled for temperature and optimized for heat transfer. When the heat source is removed, the bismuth alloy solidifies between the intermediate and production casing, creating a metal-to-metal annulus seal - steel to bismuth alloy to steel. Bismuth has minor expansion properties which give the packer gas tight qualities. To succeed in the field trial, this system underwent testing under full downhole conditions. The setup mimicked the pressure, temperature, casing design, and the medium in which the alloy is set downhole. The test included the heater deployment, the melting of the alloy, and pressure testing of the system up to 5,000 psi in hydraulic pressure. A unique sealing mechanism of bismuth alloy proactively prevents SAP B. The paper describes the results of the extensive R&D work undertaken, during which the annular bismuth alloy barriers were tested and withstood up to a 5,000-psi pressure differential, having been formed in drilling fluid, clear brine, and cement. The success of the implementation in the world's largest offshore field will be described. In particular, the innovative well design and deployment of the annular packer to be set in clear brine for maximum pressure integrity with a gas-tight rated seal will be highlighted. This is the industry's first downhole utilization of bismuth alloys for this size with this application. Its novelty lies not only in the size but also in the engineering required to achieve optimal heat transfer and alloy melting efficiency for such a large size, which entails carefully studying the behavior of this untraditional alloy.