The Bohai Sea or Bo Sea, also known as Bohai Gulf, Bo Gulf or Pohai Bay (Chinese: 渤海; literally: "Bo Sea"), is the innermost gulf of the Yellow Sea and Korea Bay on the coast of Northeastern and North China. It is approximately 78,000 km2 (30,116 sq. mi) in area and its proximity to Beijing, the capital of China (PRC), makes it one of the busiest seaways in the world.
Until the early 20th century, Bo Hai was often called the Gulf of Chihli (Chinese: 直隸海灣; pinyin: Zhílì Hǎiwān) or the Gulf of Pechihli or Pechili (北直隸海灣; Běizhílì Hǎiwān). Zhili and Beizhili were historic provinces in the area surrounding Beijing.
The Bohai Sea is bounded by the Changshan Islands chain between the Liaodong and Shandong Peninsulas. It has become one of busiest sea routes in recent times. There are three major bays inside the Bohai Sea: Laizhou Bay to the south, Liaodong Bay to the north, and Bohai Bay to the west. At the easternmost end of the Bohai Sea, between the southernmost end of the Liaodong Peninsula and northernmost end of the Shandong Peninsula, is the Bohai Strait (渤海海峡). A few of the rivers entering the gulf include the Yellow, Hai, Liao, and Luan Rivers. There are a few important oil reserves in the vicinity of the gulf, including the Shengli Field. Important island groups or islands in the gulf include the Changshan Islands (长山列岛), Changxing Island (长兴岛), and Xizhong Island (西中岛). The PRC provincial-level divisions that have a Bohai Sea coastline are, from the south, going clockwise: Shandong, Hebei, Tianjin, Hebei again, and Liaoning.
There are five major ports along the Bohai Sea rim, with throughputs over 100 million tons, though the port of Tangshan is further subdivided into Jingtang and Caofedian:
Caofeidian and Jingtang are usually treated as one port for statistical purposes. The ports of Dalian and Yantai are also traditionally considered part of the Bohai rim, even though strictly speaking they lie outside the limits of the sea. The Port of Longkou reached 70 million tons of cargo in 2013, and is expected to reach the 100 million ton landmark in the near future.
The Bohai Bay contains significant oil and gas reserves, providing much of China's offshore production. The main field in the region is named Shengli and has been exploited since the 1960s. It is still producing about half a million barrels a day, but is declining. Production is dominated by Chinese majors (China National Offshore Oil Corporation was mostly created for this region) but foreign companies are also present, like ConocoPhilips, Roc Oil, and others.
The Gudao Field, located in the Zhanhua sedimentary basin, was discovered in 1968, based on gravity, magnetic and seismic surveys between 1963-1964. The reservoir includes the Guantao (Miocene) and Minghuazhen (Pliocene) geologic formations within the dome-like anticline. The Suizhong 36-1 Oil Field was discovered in 1987, and produces from Oligocene fluvial-deltaic and lacustrine sandstones.:459
Oil spills have been reported frequently in this region: three spills occurred in a two-month timeframe in 2011.
In February 2011, the PRC announced that it would build a road and rail tunnel across the Bohai Strait to connect the Liaodong and Shandong peninsulas. When completed, the tunnel would be 106 kilometres (66 mi) long. This plan seems have been superseded as of July 2013, with a modified plan involving a 123-kilometre (76 mi) tunnel between Dalian, Liaoning and Yantai, Shandong.
The overall concept had its origins in a 1994 plan, which had been intended for completion by 2010 at a cost of $10 billion.