Abstract: The vast distribution of natural gas in southern Songliao basin brings fame to more than 150 wells with commercial gas flow in 63 spots of 16 horizons in proved 8 gas fields and 5 gas caps to date. This paper analyzes in detail these spots, gas fields and caps,sums up the vertical and lateral distribution of the gas pools and associated relationship among gas pool, oil reservoir and gas cap as well as gas controlling factors and reservoir features.Study shows that the gas can be vertically classified into 5 gas-bearing assemblages, of which deep coal-related gas is dominant, and long-term developed and inherited large scale structures normally give rise to forming multiple sets oil-gas bearing strata with gas cap reservoirs gradually changing into gas pools from the bottom to top. The lateral distribution of gas is divided into 2 zones and 6 belts, and from center toward circumferential terrace of Songliao basin,the gas changes from solution gas into coexistence of solution gas,cap gas and gas-pool gas. In some regional monoclinal structures, gas distribution assumes characteristic by oil reservoir gradually changing into gas-cap reservoir and gas pool from bottom toward top with the structure rising. The gas pools are proved to be most lithologic-structural complex ones, with porous-type porosity and low permeability . In addition, south part of Songliao basin is rich in advantaged CO₂ resources.

Key words: natural gas, gas field, distribution, gas pool type, Songliao basin