A 40-million-year-old chemical signature
Approximately 60 kilometers off the coast of Myanmar, beneath 110 meters of water in the Bay of Bengal, lies the Shwe gas field. The natural gas extracted here is almost entirely biogenic, meaning it was produced by the decomposition of ancient organic matter. Geochemical analysis points to its origin: marine organisms that lived and died during the Oligocene Epoch, roughly 40 million years ago. The organic-rich shales formed from these organisms are now buried four kilometers beneath the seafloor, where temperature and pressure converted the biological material into methane.
The gas itself is described as "lean," with a methane content of 99%. This high purity results from its biogenic origin. The gas migrated upwards from the deep Oligocene source rocks and accumulated in much younger Pliocene-aged sandstone reservoirs. These reservoirs are located at depths between 2,900 and 3,300 meters below the seabed. The trapping mechanism is a combination of anticlines (upward-folding rock layers) and stratigraphic seals, where porous sandstone layers are covered by impermeable rock.
The discovery well, Shwe-1, was drilled in late 2003, and the field was confirmed in 2004. The reservoirs consist of two main series, the G5.2 and the G3.2, which are characterized as Pliocene-aged turbidite sands. These sands were deposited by underwater avalanches of sediment flowing from the massive Bengal Fan to the northwest. The geology is more complex by sedimentary injection features, or injectites, where over-pressured sand was forced upwards, creating vertical connections between different reservoir layers.
Tapping an ancient reservoir
The Shwe project, which also includes the smaller Shwe Phyu and Mya fields, began production in July 2013. The integrated fields initially held proven reserves estimated at 9.1 trillion cubic feet of natural gas. The central processing platform, a 40,000-tonne structure, stands in 110 meters of water and handles the gas from multiple subsea wells. From this platform, a 110-kilometer, 32-inch diameter subsea pipeline transports the gas to an onshore terminal at Kyaukphyu on Ramree Island.
From the terminal, the gas enters the Myanmar-China gas pipeline. This extensive pipeline network travels 793 kilometers across Myanmar before entering China. The full pipeline extends over 2,500 kilometers in total, delivering gas to China's Yunnan Province. It has a design capacity to transport up to 12 billion cubic meters of gas annually.
The Shwe field's production is significant, with daily output around 700 million cubic feet. The majority of this gas—about 80%—is exported to China, with the remaining 20% reserved for domestic use in Myanmar. The project is a joint venture operated by South Korea's POSCO International (51%), with partners including the state-owned Myanma Oil and Gas Enterprise (MOGE) (15%), India's ONGC Videsh (17%) and GAIL (8.5%), and the Korea Gas Corporation (KOGAS) (8.5%).