The dispute between Beijing and Tokyo over oil and gas fields in the East China Sea remains a persistent source of friction in the relationship, and contributes to broader maritime tensions between the two sides. The issue receives less attention than the dispute over the Senkaku Islands—much less the constantly evolving state of play in the South China Sea—but that does not mean that the situation on the disputed continental shelf is static. AMTI has previously tracked the expansion in the number of Chinese oil rigs in the area in recent years, which have been installed despite Tokyo’s objections. In 2017, China placed three new rigs in the area, which appear to have been accompanied by a spike in activity by Chinese service vessels.

The first new rig, Haiyang Shiyou 942, is owned by Drilling China Oilfield Services and was installed on or before February 18, 2017. The Kantan Qihao, a drilling jackup rig owned by Sinopec Offshore Oilfield Services, appears to have arrived on the scene between July 19 and 21. And most recently, the Kaixuan Yihao owned by CIMC Raffles Offshore was installed on approximately August 19.

These drilling platforms are meant to tap oil and gas basins that straddle the median line between the two countries, which Japan provisionally claims as the boundary between its continental shelf and that of China. China does not recognize that median line and instead claims an extended continental shelf that stretches much farther east. But from Tokyo’s perspective, Beijing is unilaterally draining resources that should be shared by both countries. In an effort to manage tensions, China and Japan reached an agreement in 2008 to establish a joint development area along the median line and to give Japanese companies preferential treatment in pairing with Chinese counterparts to exploit other areas nearby.

Unfortunately, tensions between the two states spiked after 2008 and the agreement has never been implemented. China has continued to install drilling platforms close to, but never over, the Japanese-claimed median line (and outside of the joint development area). This practice allows Beijing to insist it has not violated either the 2008 agreement or the UN Convention on the Law of the Sea, while flouting the principle of equity underpinning both. Many of these rigs appear to have begun operating, as evidenced by the tell-tale flaring of gas visible in satellite images (see the gallery at the bottom of the page) as well as the regular operation of Chinese service vessels operating between them and the shore (mainly from the coastal city of Zhoushan).

Between early July and early September, AMTI used automated identification system (AIS) data from Windward to monitor the activities of Chinese vessels operating around the rigs. The map below depicts the activity of ten vessels that appeared to be servicing the rigs during this time, with each dot representing an instance when a vessel’s AIS signal was picked up by a shore- or satellite-based receiver. This is an imperfect system with inevitable gaps in coverage when ships might have had transceivers turned off or signals were not received for any number of reasons, but it helps illustrate the flurry of activity in the area during this period. Each of the vessels in question is profiled below the map, based on the admittedly limited available data about them. It is entirely possible that there were other vessels operating between the rigs during this time that did not have their AIS transceivers on at all.

In the map below, zoom in and out to view a rig location or ship path more closely. The animation can be paused from the timeline, and all AIS data from a specific range of dates can be viewed by clicking and dragging on the timeline.


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