Premier Oil is seeking buyers for a 25% stake in the Tuna Field development in Indonesia after reaching a gas sale deal with Vietnam, CEO Tony Durrant said Nov. 16.

Premier and SKK Migas signed on Nov. 10 an agreement to sell gas to Vietnam from the Tuna development, Premier said in a trading update. The field holds about 500 billion cubic meters of resource, Durrant said.

The offtake agreement “represents a significant step forward in the potential development of the field envisaging using a new cross-border pipeline to connect the Tuna area to the existing Nam Con Son Pipeline system in Vietnam,” Premier said.

Premier will conduct appraisal drilling for the project in 2019 and will likely make a final investment decision late that year or in early 2020, Durrant told Reuters in an interview.

The U.K.-focused oil and gas explorer owns a 65% stake in the field and will seek to sell up to a 25% stake to a partner in order to help finance the development, Durrant said.

“We would like to keep 40% of the field,” he said.

Production from the field, which Premier discovered in 2014, is expected to start in 2022, he added.

Premier Oil expects its $2.8 billion debt pile to start falling, with its flagship Catcher oil field in the North Sea set to begin production on time in December, the company said Nov. 16.