Utilizing BiSN’s wel-lok™ Seal Through Casing (STC) tool to achieve a permanent barrier.
See Tool SpecificationThe operator had previously attempted to set multiple plugs for well abandonment using conventional cement and resin methods but faced challenges in achieving effective barriers through 4.00” tubing. To overcome this, a dual-section milling window campaign was executed using a specialist milling tool, providing access from inside the 4.00″ liner to outside the 5½” casing to set a formation-to-formation BiSN bismuth alloy barrier in the 8.50” open hole.
To set a thru tubing permanent, gas-tight barrier in a dual casing section milled window against open hole, using BiSN’s bismuth alloy technology – reducing window length while creating a gas tight barrier.
Low downhole temperatures and thru tubing application required heating of fluid to maximize heater efficiency.
Close coordination between field engineers, operations, and engineering was needed to ensure success.
The wel-lok™ STC Heater and Beads tool was deployed across the section-milled windows to form a V0 gas-tight barrier on top of existing cement plugs.
The bismuth alloy was deployed from surface as free-flowing beads through the drill pipe, followed by activation of the chemical reaction heater using a timer-based running tool.
The molten bismuth alloy, with its low viscosity and high density, flowed into the open hole section and solidified into a single, homogeneous metal plug — creating a full-metal, V0 gas-tight barrier across the formation.
The bismuth alloy barrier was placed on a cement base provided by the operator.
The heaters were checked at surface and deployed on drill pipe, with well fluids preheated to improve the efficiency of the heater, which was designed for through-tubing deployment.
Following timed activation, a pressure increase was observed at surface, confirming successful deployment. The heater was then retrieved from the molten alloy and pulled out of hole, leaving a full cross-section bismuth alloy barrier in place.
Visual confirmation using downhole cameras and tag-backs, followed by surface pressure monitoring, verified plug height, integrity, and the successful deployment of a gas-tight barrier against the formation.
“Those of you who have worked around me long enough have probably heard me joke about how P&As are 5% of my budget and 70% of my headaches. One of the recent successes we’ve achieved is the bismuth barrier placed across a milled window. It delivered the sealing performance of a larger cement or resin barrier while requiring a significantly shorter window, with plug lengths as short as 5 feet.”
– Completions Manager, US Land Operator
The wel-lok™ STC (Seal Through Casing) has been developed to achieve a gas tight V0 seal well annuli that cannot be achieved by traditional cement balance plugs. Run on electric line, coil tubing or drill pipe, this tool does not need surface pumping equipment to circulate the alloy in place. Due to its viscosity and density, once melted the liquid alloy will flow with gravity into the annulus. When it cools below its melting point it solidifies, expands and creates a gas tight seal across the entire wellbore. The entire process, from melting to solidification, takes place in minutes and the seal is ready to test within an hour.
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