四川盆地长兴组-飞仙关组礁、滩分布的控制因素及有利勘探区带

四川盆地二、三叠系长兴组-飞仙关组礁、滩气藏勘探的不断突破需要更进一步弄清其礁、滩体分布及其控制因素。为此，在对比分析各种过井资料及三维地震资料的基础上，研究了晚二叠世区域古地貌格局、拉张作用、长兴组-飞仙关组体系域等对开江-梁平海槽形态和礁、滩分布、发育的影响。结论认为：①晚二叠世末，四川盆地呈“三隆三凹”的古地貌格局，其对礁滩的分布起到了重要的控制作用；②拉张作用的不均衡性使得环开江-梁平海槽台缘斜坡带坡度陡缓存在差异，这一差异影响着礁滩发育的早晚和连续性；③层序演化结果表明龙潭期以海侵体系域为主，长兴组中后期为高水位体系域，体系域的变迁使得近台缘地区可能发育多期礁体。此外，还对台缘地区微古地貌的刻画方法进行了探讨，认为台缘生物礁的分布形态可以是沿台地边缘弯曲展布的串珠状礁体，也可能是与海槽斜交的斜列式分布的礁体。最后根据研究结果，划分出了有利勘探区带。

Factors controlling reef-bank reservoirs in the Changxing-Feixianguan formations in the Sichuan Basin and their play fairways

Breakthroughs in gas exploration of reef-bank reservoirs in the Permian-Triassic Changxing-Feixianguan formations,Sichuan Basin,make it necessary to delineate the distribution of reef-banks and their controlling factors.Based on the comparative analysis of various well data and 3D seismic sections,the impact of various factors is studied on the geometry of the Kaijiang-Liangping trough and the distribution of reef-banks,such as the Late Permian regional palaeogeomorphologic framework,tectonic extension,system tracts of the Changxing-Feixianguan formations.The following conclusions were drawn.(1) At the end of Late Permian,the palaeogeomorphologic framework of the Sichuan Basin was "three depressions separated by three uplifts" which played a key role in controlling the distribution of reef-banks.(2) The unevenness of extension caused the differences in the angles of slope on platform margin around the Kaijiang-Liangping trough,which determined the time of reef-bank development and their continuity.(3) The evolution of sequences reveals that transgressive systems tract(TST) deposits dominated the Longtan period and highstand system tract(HST) deposits dominated the mid-late Changxing period.(4) The change of system tracts made it possible to develop multistage reefs near the platform margin.In addition,the methods are studied for characterizing the micro-palaeogeomorphology on the platform margin.It is believed that the bioherms on the platform margin can occur as beaded reefs in curved distribution along the platform margin,or occur as echelon reefs oblique to the trough.Play fairways were identified based on the study results.Oolitic beach reservoirs may occur on the transgressive slope margin in the Kaijiang-Liangping trough,while the oolitic beach on the aggradational platform margin of the Feixianguan Formation is the most favorable play fairway.