Hydrocarbon exploration engineering is a special technique, which integrates petroleum geology ,exploration techniques and related disciplines to best determine hydrocarbon reserves. This concept is resulted from the successive improvement of modern exploration theories, methods and techniques, and the modern exploration is based on the perfect combination of exploration theories, techniques and computer techniques. The emergence of hydrocarbon exploration engineering will change the traditional exploration which was a personal art to an explorationists' science.

Up till now, China (Taiwan province not included) has discovered 33 large and middle gas fields (each of them has a reserve of≥10×109m3).The total proved reserves of these fields count 72% of the national proved reserves. This paper chiefly discusses the main controlling factors of large and middle gas fields in China ,i.e., they are: developed in gas generating center and /Or its surrounding areas; occurred in paleo-uplifts within the gas generating area, and in buried low, middle coal series or related traps above or beneath them; of late reservoir-forming period possessing large-area porous reservoirs and good regional cap rock. Based on these controlling factors, this paper gives comprehensive evaluations for Tarim, Junggar, Turpan-Hami, Qaidam, Ordos, Sichuan, Yinggehai, Qiongdongnan and Donghai basins. It also points out the exploration plays for discovering large and middle gas fields.

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