Gas fields are mainly distributed in coal-rich gas-forming depressions and surrounding timely paleo-uplift and paleo-slope areas.

Luzhou-Kaijiang ancient uplift in Sichuan basin is located in the coal-rich gas depression of Longtan coal measures in the late Permian, and it is the main distribution area of many gas fields in Longtan coal measures and upper Permian marine strata. The central Sichuan area on the northern slope of Luzhou-Kaijiang ancient uplift is a gas-rich depression of coal-bearing measures in the Late Triassic, and it is the main gathering area of coal-formed gas fields in the Upper Triassic. Western Sichuan depression is the main part of the late Triassic coal-rich gas-forming depression, and the gas fields are mainly concentrated in three paleo-uplifts (paleo-structural belts) and slope areas in the region. Zhongba gas field is controlled by the ancient anticline formed in Indosinian period, but not by the anticline reformed in Himalayan period (Figure 1 1-3).

Figure 1 1- 1 Large and extra-large gas fields in Ordos Basin and Carboniferous-Permian coal-rich gas depression.

(According to Dai Jinxing, 2007)

Figure 1 1-2 Natural gas intensity map of gas-rich depression in Kuqa depression, Tarim basin

(According to Dai Jinxing, 2007)

Large and super-large coal-formed gas fields in Ordos basin are distributed in the east of the central uplift, and the coal-formed gas fields in Xihu sag of the East China Sea shelf basin are mainly concentrated in the long-developed western slope area and the south of the central uplift structural belt. The Ya 13- 1 gas field in Qiongdongnan basin is an early-formed drape anticline, and the coal-formed gas in Kuche sag is mainly concentrated in the slope thrust belt near the orogenic belt, indicating the existence of coal-formed gas.

Figure 1 1-3 Profile of Zhongba gas field in western Sichuan of Sichuan Basin.