Integrated Wireless Barrier Monitoring Prevents Greenhouse Gas Emission During Extended Well Suspension in Carbon Capture and Storage (CCS) Field
Authors: Paluruan Firman , Azevedo Vinicios 
Published: October 2023

The operator of an Australian liquefied natural gas (LNG) plant needed to shut-in and suspend two injector wells containing extremely high CO2 (up to 99%) to perform maintenance and perform Xmas tree removal. Downhole double barriers were necessary in addition to barrier verification to ensure zero leakage across the well isolation barriers. Maintaining well barrier integrity and monitoring pressure and temperature below the tubing hanger plug were key.

To achieve a proper barrier and verify the installed barriers, a service company delivered an engineered solution involving a unique combination of proprietary retrievable bridge plug (RBP) and a downhole telemetry system with wireless acoustic communication capability. Displayed real-time data enabled the operator to confirm the well was successfully isolated and barriers were safely set.

This downhole telemetry system deploys surface-powered equipment for monitoring pressure below the RBP to evaluate barrier integrity quickly and accurately throughout the well suspension process. It achieves this using acoustic wireless transmission of downhole information to the surface for interpretation without the need for e-logs. This field-proven well communication system can monitor well integrity for extensive suspension durations (more than 500 hours for two wells), delivering valuable, reliable verification data while simultaneously setting the barrier and testing for leaks in a single run. The simple integrity verification accommodated safe X-mas tree removal in a critical HSE environment.

Downhole wireless telemetry was continuously maintained throughout the entire well maintenance operation. Costs related to "dry" wellhead operations were reduced by eliminating the need for wireline mobilization and rig up to secure the well, while also reducing time to verify the barrier. Cost savings were significant per well.

Using the service company's proprietary pressure verification system eliminated the need for compressing large volumes of gas to conduct a positive test. It also mitigated risks associated with personnel in the well bay area by performing real-time wireless diagnostics, as well as buildup before equalizing and retrieving the bridge plug. Demonstrating the validity of the lower barrier and deep-set plug, this downhole acoustic telemetry technology proved its superiority to traditional isolation monitoring methods; thus, the operator performed the same procedure during regular maintenance in its other wells.

When two wellbore barriers are installed in close proximity, it can be difficult to ensure the integrity of the upper barrier. By measuring the pressure difference over the barriers, the integrity of the shallower barrier can be verified. Traditional practice is to use an anchoring or plug device to build a barrier above, which requires multiple slickline/e-log runs and pressure tests/controls for correct barrier placement. An alternative method is presented involving a unique combination of proprietary RBP and robust downhole acoustic telemetry system for real-time time monitoring, highlighting its success, cost savings, and continued use in additional wells.