CO2 Sequestration – Operations and Maintenance at the Aquistore Site

  • 2019 Technical Conference Program
  • May 29, 2019
  • 3:00 pm - 3:30 pm

WBPC 2019 Abstract #35

CO2 production at the Boundary Dam Unit 3 CCS Facility can vary from day to day depending on a number of factors.  This includes production goals set by management, cleaning and maintenance cycles of varying pieces of equipment, and health of the amine inventory at any given time.  The majority of captured CO2 is compressed and sold to an off-taker for enhanced oil recovery and then what’s left is sent for sequestration at the Aquistore injection site.  This causes the injection rate to significantly vary from month to month or even week to week and daily.  Operators monitor the capture rate throughout the day and adjust variables within the capture process (usually flue gas diversion rate and amine flow) to ensure the total CO2 captured for a given day will meet the target.  The split between what is sold and how much is injected is handled through a control valve located at the Aquistore site.  If there is an upset or sudden change to the capture rate from the power plant, the aquistore well is the first that will get adjusted to ensure that CO2 sold to the off-taker is maintained at a consistent level.  A highly variable injection rate can cause some complications for the deep well.  Pressures and temperatures within the tubing string and down-hole will fluctuate with injection.

In 2016, it was noticed that pressure was building up in the annulus of the well.  As the base fluid of the annulus was water, this lead to some concern regarding corrosion of the steel components.  This was monitored closely over the next year and a half, leading up to spring 2018, where the tubing string was removed to repair the suspected location of the leak, replace down-hole instrumentation, verify the integrity of the casing, and remove and replace the water from the annulus.  This workover was successfully completed, but not without some lessons learned.