Abstract: Shallow gases are abundant within the J urassic in northwestern Sichuan. These gases are secondary in nature and pooled in structuralOlithologic traps within fluvialOlacustrine deltaic systems. The reservoir beds consist mainly of riverO mouth bars and distributary channel sandbodies which are small
in size , numerous in number , and typically lensiod in shape ,displaying strong sensitivity and nonhomogeneity. The single well productivity is low , and the pools can be put into the tight reservoir category. On the basis of detailed research of the reservoir geological characteristics , a series of techniques focusing on the exploration of these gas pools were established. The
techniques include log evaluation centered on lithology recognition and oil/ gas/ water beds discrimination , qualitativeOquantitative reservoir prediction based on seismic inversion tagged to wells , underbalanced drilling , and hydrologic fracturing with lowOtemperature breaker systems. Application of these tech niques witnessed an increase of explorationOwell success rate
from 40 % to 80 % in the Penglaizheng gas field and a total success rate of 77 % in the J urassic shallow formations in northwestern Sichuan for the past three years (of the 61 wells drilled , 44 hit gas) . As a result , two gas fields and five gasO bearing structures were found , a proved gas reserve of 286. 72×108m3 was established , and singleOwell productivity was increased by several to tens of times.

Key words: Sichuan basin, exploration, integrated techniques, log evaluation, reservoir prediction, underbalanced drilling, reservoir stimulation