Tengiz (Turkic for “sea”) oil field is located in north-western Kazakhstan’s low-lying wetlands along the northeast shores of the Caspian Sea. It covers a 2,500 km² project license area which also includes a smaller Korolev field as well as several exploratory prospects. Tengiz reservoir is 19 km×21 km. Discovered in 1979, it is one of the largest discoveries in recent history, having recoverable reserves estimated at between 6-9 bln barrels.. The city of Atyrau, 350 km north of Tengiz, is the main transport hub of Tengiz oil. Many nations are involved in a large geopolitical competition to secure access to this source of oil.

The field was jointly developed in 1993 as a 40-year venture between Chevron Texaco (50%), KazMunayGas (20%), US ExxonMobil (25%) and LukArco (5%). The joint venture company is known as Tengizchevroil (TCO). Chevron is the operator of the TCO field.

The Tengiz oil fields entered a new phase of production with the construction of its Second Generation Project (SGP) and the introduction of sour gas injection (SGI). This onshore development, which has been in the planning and approval stage since 2002, began in 2004 and required a total investment of $7.4 bln. The integrated project was completed in the second half of 2008.