October 27, 2025 • 2 min read
Simplifying subsea tiebacks with pseudo dry gas in Australia
How we reduced costs and improved overall performance for a long shallow water tieback system.
Faced with the challenge of optimizing an existing gas flow system, a customer came to us looking for a solution that could reduce costs and enhance production reliability.
While working with a customer in Australia on a new onshore plant, our Offshore Energy team was approached to investigate if a Pseudo Dry Gas (PDG) solution could reduce expenditure and improve production risks on their existing gas flow system.
Statistic Cards
Balancing cost and operations for smarter performance
The project involved connecting an offshore gas source to an onshore facility, but it came with some major cost and operational hurdles.
Due to the length of the pipeline to shore, the customer had to invest in expensive liquid management equipment, such as a large slug catcher to handle rapid surges of liquid. There was also a risk that water could start flowing from the well earlier than expected, which could reduce total gas production capacity.
We also discovered that the performance of the corrosion inhibitor system was being pushed beyond comfortable industry practice. This raised concerns of a higher corrosion rate, risking a design change to a corrosion resistant alloy.
Pivoting to deliver better production capability
The customer’s original plan involved moving gas over an almost 300km underwater pipeline at a specified flow rate.
A section of a lined pipe at the start of the system was routed to a 2,000m3 slug catcher onshore, while a remote offshore platform and high-integrity pressure protection system were placed infield to provide the necessary power and communications systems. This solution, however, was proving to be complex and expensive.
We designed a PDG solution to provide an affordable alternative. By adding a smaller liquid flowline piggyback connected to special pumps, we were able to reduce the slug catcher size to 100m3 and increase gas throughput by almost 30 percent without a change of diameter – reducing costs from day one.
The new design also made production more reliable, reducing back pressure and corrosion inhibitor availability for a system better designed to handle produced water, achieving higher overall gas recovery.
Reducing complexity, increasing reliability
Our PDG solution simplified operations, reduced pigging requirements and mitigated the use of compression, helping to lower Scope 1 and 2 emissions compared to the customer’s original design. The result: a safer, more reliable system with significantly lower capital cost and higher production performance.
