Xinchang gas field in western Sichuan depression is a large superimposed gas field characterized by multiple layers and various reservoir types

with a vertical span of over 4000 m

and is composed of the shallow structural-lithologic gas reservoirs

the middle structural-diagenetic gas reservoirs and the deep structural-fracture gas reservoirs.Vertically

its major gas reservoirs include the shallow layer Upper Jurassic Penglaizhen Formation

the middle layer Middle Jurassic Upper Shaximiao Formation and the deep layer Upper Triassic 2nd member of Xujiahe Formation.The main control factors of Penglaizhen Formation gas reservoirs are the channel sandstone subfacies in the nose-like anticline

the main control factors of the Upper Shaximiao Formation gas reservoirs are the favorable diagenetic facies in the sandstones of superimposed mouth bar and distributary channel microfacies on the palaeohigh

while that of Xujiahe Formation gas reservoirs are the fracture systems developed in the large palaeohigh strucutral zone.The key technology for prediction of prolific zone in the shallow gas reservoirs is bright spot identification of seismic response with "low frequency but strong amplitude";the key technology for prediction of prolific zone in the middle gas reservoirs is multi-disciplinary comprehensive reservoir model building;while the key technology for prediction of the prolific zone in the deep gas reservoirs is the comprehensive prediction technology through geology-seismic-logging integration and gas-bearing property detection technology.