China is steadily expanding its oil and gas activities in the East China Sea, adding new offshore platforms, exploratory drilling operations, and geological surveys near disputed waters also claimed by Japan. The developments, which Tokyo views as part of a broader effort to establish a sustained Chinese presence across strategically important maritime spaces, come amid widening Chinese coast guard and naval operations across the first island chain and the western Pacific.
Satellite imagery and ship-tracking data cited by the U.S.-based Center for Strategic & International Studies’ (CSIS’) Asia Maritime Transparency Initiative (AMTI), as well as the Japanese government’s official statements, show Beijing has constructed three new permanent offshore platforms over the past year while simultaneously conducting exploratory drilling and geological surveys closer to areas previously designated for joint development with Japan.
The latest activity comes amid a decades-old dispute over maritime boundaries in the East China Sea, where both countries claim overlapping exclusive economic zones and continental shelves. Japan advocates a median-line approach that would divide the waters equally, while China rejects the line altogether, arguing its continental shelf extends much farther east.
According to analysis by the AMTI, China completed three new fixed platforms between August 2025 and April 2026 at locations that correspond with exploratory drilling conducted between 2022 and 2025. The installations were built using heavy-lift vessels including Lan Jing 7500 and Tiejian Qizhong 5000, and are now supported by jack-up drilling rigs such as Zhenhai 6, Haiyang Shiyou 942, and Dongfang Faxian.
The development adds to an existing network of Chinese infrastructure in the area. Between 2013 and 2015, Beijing built a dozen platforms along the median line, just south of a previously agreed joint development zone, prompting repeated protests from Tokyo.
The dispute was partially addressed in June 2008, when both countries reached an agreement to jointly develop gas resources in parts of the East China Sea while shelving their sovereignty disagreements. However, negotiations later stalled, and the arrangement was never operationalised. Tokyo has repeatedly called for its implementation, while Beijing has continued unilateral development activities.
Recent exploratory operations suggest China may now be pushing into even more geopolitically sensitive waters.
AMTI identified mobile drilling activity between December 2025 and May 2026 near the edge of the dormant China-Japan joint development zone. Although the drilling rig itself did not broadcast Automatic Identification System (AIS) signals, support vessels including Kantan 303 and Haiyang Shiyou 642 were tracked operating alongside it, while satellite imagery confirmed its presence for several months.
China has also expanded geological surveying efforts. The survey vessels Haiyang Dizhi 8 and Haiyang Dizhi 9 conducted three seabed surveys over the past year, including one significantly farther north near the joint development zone. Experts view these surveys as potential indicators of future infrastructure construction because exploratory work has historically preceded the installation of permanent platforms.
Meanwhile, Japan has been registering diplomatic protests with China.
In January, Japan said it had confirmed that China had fixed a mobile drilling vessel on the Chinese side of the median line and issued navigation warnings through its coast guard. Chief Cabinet Secretary Minoru Kihara described the activity as “deeply regrettable”, saying China was attempting to create faits accomplis in waters whose boundaries remain unresolved.
“It is deeply regrettable that China continues its unilateral development activities and attempts to make them an established fact in these waters despite repeated protests from Japan,” Mr. Kihara said on January 8th. “We immediately strongly protested through diplomatic channels.”
Japan lodged another formal protest in April after confirming the installation of an additional structure, once again urging China to resume negotiations on implementing the 2008 agreement.
While China has so far kept its East China Sea energy infrastructure narrowly on its side of the disputed median line, the combination of new platforms, exploratory drilling and expanded geological surveys suggests Beijing is gradually widening the scope of its activities.
Japan, however, argues that hydrocarbon reservoirs beneath the seabed may straddle both sides of the median line, allowing China to potentially extract resources that extend into areas claimed by Japan.
Also, for Japan, the concern extends beyond energy extraction itself. Tokyo increasingly sees the sustained presence of Chinese industrial assets as part of a broader strategy to establish enduring control over contested maritime spaces through incremental actions that stop short of outright confrontation but steadily alter realities on the ground, or in this case, at sea.
And, Tokyo’s concerns may not be unfounded because the aforeaid East China Sea developments do appear to form part of a broader expansion of Chinese maritime activity across the western Pacific, when viewed together with Beijing’s efforts to extend China’s coast guard and naval presence across strategically important waters of the first island chain.
As previously reported by Unraavelling Geopolitics, in recent weeks, China dispatched its coast guard vessels east of Taiwan in direct response to planned Japan-Philippines maritime boundary negotiations, framing the talks as an infringement on Chinese sovereignty.
In that report, the Author had pointed out that these maritime operations which Beijing said were ‘special law-enforcement patrols’ follow China’s routine incursions into Taiwan’s restricted waters around Pratas Atoll/Dongsha Islands since February 2025, and argued that they signal a broader effort to establish a sustained presence across strategically important waters linking the South China Sea, the East China Sea, and the Pacific Ocean, allowing Beijing to gradually normalise its operational footprint across critical sections of the first island chain.
Also, before that, Japan’s defense ministry said in a bulletin that China’s aircraft carrier Liaoning and its accompanying warships conducted exercises in the western Pacific east of the Philippines between May 26 and May 28, underscoring Beijing’s expanding naval footprint beyond the first island chain.
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Per the bulletin, carrier-based aircraft and helicopters carried out around 170 take-offs and landings as the strike group operated east of the Philippines’ Luzon island and sailed to within 590 km (367 miles) of Japan’s Miyakojima island before continuing southeastward along the Philippines in the Pacific Ocean.
A month earlier, Taiwan had also reported the Liaoning’s transit through the Taiwan Strait in April, marking its first such passage since December.
Tanmay Kadam is a geopolitical observer based in India. He has experience working as a Defence and International Affairs journalist for EurAsian Times. He can be contacted at tanmaykadam700@gmail.com.
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