World’s Largest Nontraditional Packer with Extreme Annulus Sealability
Authors: Al Marhoon Zahrah , Alshaarawi Amjad , Atiyah Abdullah , Carragher Paul , Nasser Mohmmed , Dearmon Jake 
Published: February 2025

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. Thermally deformable annulus packer (TDAP) is a nontraditional seal that aids in sealing leakages in annulus with sustained casing pressure as a preventative solution. The engineering of a unique metal alloy can provide solutions to that challenge.

The performance of the proposed system (TDAP) has been laboratory-tested under downhole conditions. In particular, a full-scale version of the packer has been set in a full-scale replica of the targeted casing-casing annulus (CCA; 9⅝×13⅜ in.) in the three potential fluid mediums for setting: (1) clear brine, (2) a typical fluid formula, and (3) a typical cement slurry. The sealing capacity of each packer was pressure tested with both a hydrotest and a gas test with the maximum pressure allowed by the casing strength.

The method used to demonstrate the applicability of this system involves having disks of bismuth alloy on the exterior of one joint of the 9⅝-in. casing. The joint is positioned to achieve the intended depth for the packer. The packer is set above the 13⅜-in. shoe. After cementing operations, the disks are turned into a liquid using a heater run inside the 9⅝-in. 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 gives the packer gas-tight qualities.

To achieve success 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 was 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 sustained annulus pressure. The paper describes the results of the extensive research and development work, 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 pressure rating of the bismuth-alloy packer, as well as its ability to seal gas, was shown to strongly depend on the medium in which the packer was set. The best performance was observed when the packer was set in clean brine. Under such conditions, the packer was able to hold the maximum pressure allowed by the casing strength with both the hydro and the gas pressure tests.

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.