利川复向斜长兴期台缘礁相带的地震预测

Seismic Prediction for Lichuan Synclinorium Platform Margin Reef Facies Belt in Changxing Period

利川复向斜位于鄂西渝东区,该区晚二叠世长兴期处于川东台地与鄂西盆地的结合部位,该区见天坝等地表出露台缘生物礁,证实该区发育台缘礁滩相带。基于该区域长兴组沉积模式,建立地质模型,开展地震正演分析各沉积相、生物礁地质体的地震响应特征。充分利用该区二维地震资料,利用"相面法"分析长兴组地震相类型,编制地震相平面图,解释沉积相,预测了台地边缘沉积相带展布。同时开展地震属性分析、波阻抗反演等地震预测,进一步确定台缘相带展布。地震预测认为该区南、北部长兴组台缘相沉积特征不同,该区南部台缘相为缓缓坡沉积,主要受开江-梁平陆棚控制,陆棚水体较浅;中北部为镶边台地沉积,主要受东面鄂西深水盆地控制。同时,通过地震预测,初步识别了该区南部台缘相带内生物礁异常体5个,总面积60.35km2。

.. Lichuan synclinorium is located in West Hubei and East Chongqing. The Late Permian in Changxing period is at the joint part of highland of East Sichuan and Basin of West Hubei. There appears platform margin reef in Jian- tianba and other regions, which confirms a well--developed platform margin reef flat fades belt in Lichuan synclinorium. Geologic model is established based on sedimentary pattern of Changxing formation; each sedimentary facies and seismic response characteristic of bioherm geologic body are analyzed with the help of seismic forward; 2D seismic data and phase--plane solution are used to analyze seismic facies type; seismic facies plane plot is drawn to inter- pret sedimentary facies and predict its belt distribution in platform margin. In addition, seismic prediction methods such as seismic attribute analysis, wave impedance inversion are used to further confirm the distribution of platform margin facies belt. On the basis of seismic prediction, it is believed that the sedimentary characteristics of platform margin fades in southern Changxing formation are different from those in northern Changxing. Platform margin facies in the south belong to gentle--slope deposition mainly controlled by Kaijiang--Liangping shelf with shallower wa- ter while north central one belongs to edge platform deposition mainly controlled by deepwater basin in western Hu- bei to the north and at the same time it is tentatively identified that there are five anomalous bioherm bodies inside platform margin facies belt with total area of 60. 35kmz.