Abstract：Limited by complicated geology conditions and low seismic data resolution,there are only a very few successful study cases for the distribution of Changxin Group reefbeach facies in YB area of Northwest of Sichuan.Based on available drilling data,the geological data and seismic data,the sediment characteristics of the reef-beach facies reservoir in this area were described in detailed,the relation between the elastic parameters and the oilgas bearing property of the reservoir was analyzed,the spatial distribution of the reef-beach facies were fully understood,and the following conclusions were obtained:(1)There are upper set and lower set of reservoirs for the reefbeach facies reservoir in the margin of the platform in YB area,the upper one is mainly a reef top dolomite,the lower set is mainly consist of the backreef biological beach debris reservoir and the early biological beach debris reservoir;(2)The gas bearing reservoir for Changxin Group shows low P-wave velocity,low elastic modulus and low Passion Ratio,the non-gas bearing reservoir is just opposite,with increase of the porosity,the P-wave velocity,the elastic modulus and Passion Ratio all decrease in different extent.For most wells which were drilled based on the reservoir prediction results industry gas was obtained,the Changxin reservoir sections all show low Passion ratio characteristic,which match the classification basis for first type and second type gas-bearing reservoir.
