井下钻探和地震资料显示表明四川盆地北部下三叠统飞仙关组发育多套鲕粒滩储层,该套储层也是飞仙关组主要的天然气产层。通过鲕粒滩储层发育段井震标定,并结合鲕粒滩储层地震正演数字模型分析结果,建立了飞仙关组不同层段鲕粒滩储层发育所对应的4种地震响应模式,总结了不同地区鲕粒滩储层地震响应的异常特征。在此基础之上分别对飞仙关组一段、二段、三段开展连片二维地震测线地震相分析,通过地震相与沉积相对应关系分析,恢复四川盆地北部地区飞仙关组一段、二段、三段沉积相特征,综合鲕粒滩储层地震异常特征与沉积相分布区,预测了飞仙关组鲕粒滩储层在该地区的分布特征。飞仙关组一段、二段存在环陆棚相的台地前缘斜坡一台地边缘鲕滩相一开阔台地相沉积体系,台地边缘鲕滩相在陆棚相东、西两侧沿北西向呈条带状展布,分布面积大于4400km2,飞仙关组三段全区演变成开阔台地沉积,鲕粒滩分布广阔,主要分布在龙岗一元坝、剑阁、九龙山、河坝一黑池梁、普光一铁山坡等大部分地区,面积达15000km2,因此,四川盆地北部下三叠统飞仙关组鲕粒滩气藏勘探潜力巨大。
Downhole drilling and seismic data showed that multiple sets of oolitic beach reservoir were found in Lower Triassic Feixianguan Formation in northern Sichuan Basin, which was the main natural gas reservoir of Feixianguan Formation. Through well-seismic calibration of oolitic beach reservoir section and combined with analysis of seismic forward digital modeling, four seismic response patterns of corresponding various oolitic beach reservoir were established and anomalous characteristics of seismic response in different parts of the oolitic beach reservoir were summarized. Two-dimensional seismic facies analyses of 1st, 2nd and 3rd Members of Feixianguan Formation were analyzed respectively. Based on corresponding relations betweenseismic and sedimentary facies, sedimentary facies features of 1st, 2nd and 3rd Members of Feixianguan Formation were recovered. Integrating seismic anomaly characteristics of oolitic beach reservoir and sedimentary facies distribution range, distribution characteristics in the region were predicted. The sedimentary system of platform foreslope-platform margin-open platform facies mainly developed in 1st and 2nd Members of Feixianguan Formation. Platform margin oolite beach facies in the east and west on both sides showed banded distribution along the north-west shelf with more than 4 400 km2 distribution area, while 3rd Member of Feixianguan Formation turned into open platform deposits in targeted area. The oolitic beach were mainly distributed in Longgang-Yuanba, Jiange, Jiulong Mountain, Heba-Heichiliang, Puguang-Tieshanpo and other regions with a total area of 15 000 km2. Therefore, exploration potential of oolitic beach reservoir in Lower Triassic Feixianguan Formation in northern Sichuan Basin is tremendous.