SINGAPORE, July 8 (Reuters) - Hengli Group, privately-controlled Chinese oil refiner and petrochemicals producer, said on Monday it will invest 9.2 billion yuan ($1.3 billion) in shipbuilding in northeast China, two years after it acquired South Korean shipyard STX's assets.

The group's unit Hengli Heavy Industry expects to build annual steel processing capacity of 1.8 million metric tons as well as 7.1 million tons annually of shipbuilding capacity in Changxing island of Dalian city, according to a posting on the company's official WeChat platform.

The company said it will expand building super tankers carrying oil and liquefied petroleum gas, container vessels and offshore floating storage facilities as well as wind power-fuelled drilling rigs.

In mid-2022, Hengli bought shipbuilding and offshore engineering assets of STX Dalian, the Chinese unit of South Korea's STX Group for 1.729 billion yuan ($237.9 million).

Separately, Hengli Heavy Industry last week agreed to build six 325,000-tonnage super ore tankers for Singapore's shipping firm Winning International Group.

($1 = 7.2690 Chinese yuan) (Reporting by Chen Aizhu; Editing by Jacqueline Wong)