四川盆地环开江—梁平海槽长兴组—飞仙关组沉积模式

A Sedimentary Model of Changxing and Feixianguan Reservoirs around Kaijiang-Liangping Trough in Sichuan Basin

在综合分析的基础上确定了环开江—梁平海槽长兴组—飞仙关组的层序划分方案,长兴组和飞仙关组均可划分出两个三级层序。在层序格架内进行了岩相古地理的编图及演化分析,认为在台地边缘不同地区具有不同的岩相古地理特征,发育不同类型的台地边缘。结合地震资料及钻井资料建立了台地边缘的三种沉积模式:(1)以剑阁地区为代表的"进积型台地边缘",生物礁及鲕粒滩呈进积型增生,储层单层厚度较薄,储集性能差;(2)以龙岗地区为典型的"加积型台地边缘",生物礁及鲕粒滩呈加积型增生,生物碎屑滩和鲕粒滩单层厚度大,白云石化程度高,发育优质储层;(3)开江—梁平海槽与城口—鄂西海槽之间的"孤立台地型台地边缘",长兴期为半局限台地环境,飞仙关期为蒸发台地环境,台地边缘生物礁及鲕粒滩规模大,白云石化程度高,是储层最有利的勘探区带。

Based on comprehensive analysis,the frame of sequence stratigraphy is confirmed.The Changxing Formation can be divided into two sequences and the Feixianguan Formation into two sequences.Under the control of sequence framework,the lithofacies palaeogeography is mapped and the evolution is analyzed.It is considered that different platform margins develop in different areas around Kaijiang-Liangping Trough.According to the logging data and seismic data,three models of platform margin are set up：（1） the ＂progradating platform margin＂ represented by the one in Jiange area,which is characterized by reef and oolite shoal progradation to the trough center but thin monolayers of reservoir beds with low-reserved capability;（2） the ＂aggradating platform margin＂representative in Longgang area,which is characterized by reef and oolite shoal aggradation and thick monolayers of biodetritus shoal and oolite shoal reservoir beds with high dolomitization,in which excellent reservoirs develop;and（3） the ＂isolated platform margin＂ located between Kaijiang-Liangping Trough and Chenkou-Exi Trough where the sedimentary environment was the half-restricted platform during late Permian Changxing phase and became into the evaporated platform during early Triassic Feixianguan phase,which brought in a large scale of reef and oolite shoal deposition and succedent high dolomitization so this kind of margin is the most potential area where excellent reservoirs may be discovered.