The UK supermajor's finance partners KMarin and ICBC Leasing are investing more than US$1 billion (A$1.28 billion) in the tankers, which will join existing tankers in BP Shipping's fleet in 2018 and 2019.
The vessels will help service a 20-year liquefaction contract with the Freeport LNG facility in Texas, as well as other international LNG projects in BP's global portfolio including Australia.
The move comes just a day after Australian junior Cue Energy Resources gave BP until December to acquire 42.5% of exploration permit WA-359-P which contains the 15 trillion cubic feet Ironbark prospect.
BP also has an 80% interest in the block next door, WA-409-P, where it needs to spend some $2 million to de-risk the prospect over the next few years.
The company is a one-sixth owner of the NWS which will have spare capacity from around 2021 and Woodside is trying to convince its partners to take undeveloped Browse gas as a priority.
BP Shipping CEO Susan Dio said the new vessels would significantly increase the oiler's ability to safely transport LNG to anywhere in the world, and would also will be among the most fuel-efficient and technically advanced LNG tankers ever built.
Equipped with next-generation engine technology, the new ships are designed to be about 25% more fuel efficient than their predecessors.
They also will be fitted with a reliquefaction plant, so evaporated natural gas in the cargo tanks can be returned to the tanks as LNG, allowing the ships to deliver more LNG to the market.
BP has a long-term contract for 230 trillion BTUs per year of LNG capacity in the Freeport LNG facility, where the LNG liquefaction facility is under construction and the first train is due to be operational by the end of next year.
BP also participates in LNG projects in Australia, the United Arab Emirates, Indonesia, Trinidad and Angola which includes a mix of long-term, mid-term and short-term supply to enable BP to best meet the ever-changing needs of its global portfolio of customers.
Tokyo Gas, Japan's biggest city gas supplier, said overnight that it would not accept new contracts for long-term LNG purchases that contain clauses that restrict where the gas can be sold, after the country's Fair Trade Commission said such clauses are anti-competitive.
Yet Alan Haywood, CEO of BP's global supply and trading business, said the oiler had built a diverse LNG portfolio spanning both established and emerging markets, and Freeport is the latest example of how it continues to expand the reach of its LNG business to deliver flexible solutions through leveraging its scale, connectivity and relationships.
The 2017 BP Energy Outlook forecasts that global LNG trade will grow seven times faster than pipeline gas trade, such that by 2035 it accounts for around half of all globally traded gas. The newly expanded BP Shipping fleet will deliver LNG volumes to a range of BP customers around the world.