Implementing Acid Gas Injection at an Existing Gas Processing Plant to Reduce Emissions
Funded in 2020 through ERA Call #3: Industrial Efficiency, this project focused on converting TAQA North Ltd.’s East Crossfield Gas Plant from sulphur recovery to acid gas injection (AGI).In addition to the successful conversion, the project included several other initiatives designed to significantly reduce plant emissions and improve overall efficiency.
Acid gases are associated with some types of natural gas production. They form an acidic solution when combined with water and must be removed from the natural gas as part of theproduction process before it can be sold. Midstream natural gas plants like the Crossfield Gas Plant are designed to do just this. Prior to this project, the acid gas stream at the Crossfield Gas Plant was mixed with supplemental fuel gas and incinerated to yield stable sulphur for sale, but this process resulted in significant quantities of SO2, a greenhouse gas.
Instead of sulphur recovery, this project involved directing all the acid gas to compression then injection back into the underground sour gas reservoir from which it originated, i.e. acid gas injection. AGI eliminates the need for sulphur processing, thus eliminating sulphur production and the associated emissions from the incinerator stack. Supplemental fuel gas, which was burned in the incinerator, is no longer required. This new process is achieved by combingseveral existing technologies including:
- Drilling a new wellbore directionally from a surface location on the plant site toward a bottomhole, leveraging optimal reservoir characteristics.
- Installing a new compression system designed to handle acid gases and compress the acid gas to the conditions required by the downstream piping, wellbore and reservoir.
- Reconfiguring the internals of the amine regeneration tower to reduce fuel gas consumption and the associated emissions.
- Reconfiguring sales gas compression to optimize for current and forecast throughput rates, resulting in reduced fuel gas consumption and associated emissions.
During its term from 2020 to 2021, this project resulted in an initial reduction of approximately 51,500 tonnes of CO2e per year which is anticipated to result in a cumulative emissions reduction of between 700,000 and 1,300,000 tonnes of CO2e by the year 2045. The current natural gas feedstock available to the Crossfield Gas Plant suggests that operations could continue beyond 2045, limited only by economics.
Ensuring Success Through Meticulous Planning
Many considerations and choices contributed to the technical success of this project. The first was reservoir selection. After identifying the reservoir criteria, the Wabamun A Pool reservoir was chosen for its large capacity, low pressure and secure geological sealing. Next, the well was carefully designed and drilled with specialized materials such as corrosion-resistant coatings to handle the acid gas safely. The compression systems were also redesigned to improve energy efficiency and reduce fuel gas consumption. Finally, expected injection pressures and rates were modeled to ensure safe, predictable reservoir behavior.
Additionally, several lessons were identified throughout the project that will help guide other facilities. TAQA took extra time at the front end of this project to review prior projects for this facility to understand any potential challenges from the regulatory perspective. As a result, this project had adequate time and did not experience material delays. Other operators contemplating such a project should allow for protracted regulatory review and approval processes to ensure the execution schedule remains intact. Additionally, to reduce any delays due to stakeholders, TAQA developed a project website, and robust project descriptions were communicated to local area residents and businesses ahead of requesting project consent. The result was a public stakeholder that was supportive of this project and understood its intent and benefits.
What’s next?
This project was completed in 2021, and the AGI system is currently operational, safely sequestering acid gases into a depleted underground reservoir approximately 2.7 kilometers below the surface. This initiative has not only extended the operational life of the Crossfield Gas Plant, but also reduced total greenhouse gas emissions by approximately 70 per cent. AGI is now in commercial operation at a number of facilities across Alberta and other facilities considering changing to AGI may benefit from the lessons learned from this project.