四川盆地北部长兴组生物礁地震响应特征与分布规律

井下钻探结果和地震资料表明四川盆地北部上二叠统长兴组生物礁发育,通过对典型井长兴组岩性与电性资料的分析,明确了生物礁的岩性与储层发育特征。根据井下生物礁及围岩岩性与电性资料并结合过井地震剖面反射波的几何特征,建立台地边缘生物礁的地震正演数值模型,通过对比生物礁模型地震正演记录与实际生物礁地震剖面,建立针对研究区台地边缘生物礁的地震响应特征模式。依据生物礁的地震响应特征对该地区连片二、三维地震测线开展地震相分析,通过已有钻井地震相与沉积相对应关系分析,指出了长兴组生物礁在该地区的分布规律。四川北部地区地震相与沉积相带具有良好的对应关系,存在环台棚-海盆相的台地前缘斜坡-台地边缘生物礁相-开阔台地相沉积体系,地震剖面上生物礁的外部形态呈丘状或透镜状,内部为杂乱反射特征;礁盖白云岩具有亮点反射特征,生物礁底界面出现上凸或者下凹反射现象,生物礁的上部地层具有披覆反射结构,四川盆地北部地区长兴组台地边缘生物礁相在台棚-海盆相东、西两侧沿北西向呈条带状展布,分布面积大于2000km~2,生物礁气藏勘探潜力巨大。

The seismic response characteristics and distribution of the reefs in the Changxing Formation, northern Sichuan Basin

The reefs that developed well on Upper Permian Changxing Formation in the northern Sichuan Basin were confirmed by the seismic and down hole drilling data. The development features of lithology and reservoir about reef are confirmed by way of analysis between the lithologic and electric information with typical well. The seismic forward digital modeling of platform margin reef can be built and analyzed on the basis of the lithologic and electric information combined with reflected event geometric features that between the reef and adjoining rock. The seismic response feature of organic reef can be confirmed via the method of comparing the sections between the seismic forward modeling and real seismic datum. The Seismic facies analysis can be got according with the seismic response feature of reef in the two-dimension seismic line system. The reef distribution in this region is analyzed by means of corresponding relationship of seismic facies and sedimentary facies. The depositional system named platform edge slope facies-platform edge reef facies-open platform facies which distribute around the platform-shelf and marine basin has a good correspondence with Northern Sichuan basin. The reef shows a hummocky facies or lens facies external and a disorder seismic reflection inside on the seismic section. A bright reflection can be found in the reef crest dolomite. There are humped and undercut reflection events on the bottom of reef interface. Also a draping structure can be traced on the upside of reef. The platform edge reef existed in the east and west of platform-continental shelf-sea basin on both sides that located on the northern Sichuan Basin which formed as a banding. The potential area of this reef comes to more than 2000km² which has a excellent potential exploration.