sentences:  The company was initially known as Esso Standard Libya Inc., the first company to discover commercial quantities of crude oil in the Zelten oil field.In 1981, Exxon (parent company of Esso Standard) withdrew their Libyan operations, after which Sirte Oil Company was formed as a NOC subsidiary.It was established to operate the former Esso Sirte installation like the Marsa el-Brega refinery.