Worley’s INTECSEA consultancy unit has partnered with the Oil & Gas Technology Centre (OGTC) to fund prototype testing of its pseudo dry gas (PDG) liquid removal system.
This technology has been developed to make long-distance subsea tiebacks, which are not typically economic or technically feasible, commercially viable. By reducing back pressure in the pipeline, the technology eliminates the need for topsides and compression, reducing carbon emissions and costs and allowing for much greater tie-back distances.
The prototype testing is based on a strong techno-economic concept study completed in March 2019, and also funded through the OGTC. The study demonstrated the system’s “unparalleled” recovery levels, the OGTC said, which could provide an additional US$10 billion in revenue over the alternatives. This could result in “the strongest economic performance for a known stranded gas basin” north of Shetland. The study also demonstrated that upstream CO2 emissions were reduced by 65-80%, significantly improving the environmental footprint. An additional application for PDG that was studied as part of the original OGTC scope was gas disposal for small oil pool developments.
Both these studies have driven the technology development forward with wider industry support, including a six-inch scaled prototype of the liquid removal unit, which will be tested over a six-month period at Cranfield University’s flow loop facilities. This will simulate expected flow conditions typically found within a gas/gas condensate subsea tie back system to demonstrate the liquid removal efficiencies and confidence in macro flow assurance.
INTECSEA engineering lead for PDG technology, Lee Thomas, anticipates that the prototype testing will raise the technology readiness level to the point where a pilot project can be considered viable via a programme of enhanced factory acceptance testing for an integrated unit. “The solution is elegantly simple; it uses multiple passive liquid removal units and a liquid disposal pipeline connected to proven standardised pumps,” he explained in a statement.
The team will also seek an operator willing to undertake a pilot project of an integrated unit. An ideal pilot would be maintaining gas production from an existing tieback post water breakthrough in a mono ethylene glycol (MEG) constrained environment. This would create a significant value impact, with a minimal downside. Given the range of applications for this technology across a broad spectrum and the positive underlying economics, the project team is hopeful an operator will step forward.