Complex sentence: During the 1960s and 70s he spent most of his career in the petroleum (oil) sector and by the mid- 1980s he was vice minister of the Petroleum Industry and from 1996 General Manager of the China National Petroleum Corporation.
Split into simpler sentences: During the 1960s and 70s he spent most of his career in the petroleum industry. By the mid- 1980s he was vice minister of the Petroleum Industry, and from 1996 General Manager of the China National Petroleum Corporation.