Study of the main factors controlling the reservioring of large and medium gas fields and the exploration domain have important significance to development of gas industry in China.Large and medium gas fields with reserves of over 10 BCM have only been discovered in 11 basins in 4 gas-bearing regions in western

central

eastern and offshore China(excluding gas/oil bearing region in southern part of South China Sea and Taiwan province).In combination with the geologic conditions in China

ten main factors controlling the formation of large and medium gas fields are summarized

of which sufficient amount of gas generation

gas-rich sag with high gas generation intensity and good regional sealing and preservation conditions are the most important geologic factors.According to the situation of gas resources having been explored

the deep formations in Sichuan

Ordos

Tarim

Yingqiong

East China Sea

Qaidam

Junggar

Songliao and Bohai Bay basins should still be taken as the key exploration targets for a certain period of time.Gas exploration should be focussed on the foreland basins in west-central China

gas and coal-type gas in Meso-Paleozoic carbonates

(coal-and) gas/oil-bearing basins in eastern and offshore China and gas in deeply buried lacustrine mudstones

and Meso-Paleozoic coal measures and carbonates having the ability of secondary gas generation and good preservation conditions.Importance should also be attached to exploration and research of generalized biogas.