开江-梁平海槽区带南段飞仙关组层序-岩相古地理特征

Sequence-lithofacies paleogeographic characteristics of Feixianguan Formation in southern sector of Kaijiang-Liangping ocean trough

川东北飞仙关组蕴藏重要的油气资源,开江—梁平海槽区带南段地域广阔,具有较大的油气资源潜力。本文通过岩心观察、野外剖面、测井、录井以及室内薄片观察,对海槽区带南段飞仙关组层序-岩相古地理特征进行了研究。研究表明,该地区主要为连陆台地沉积模式,沉积相类型包括台地、斜坡、残留海槽;在层序界面识别基础上,将飞仙关组划分为3个三级层序,分别为SQ1、SQ2、SQ3,每个三级层序分别划分出TST、EHST、LHST 3个体系域;以体系域为编图单元,详细讨论了各个层序体系域时期岩相古地理特征及演化;层序-沉积演化上,飞仙关期随着海槽的缩小,台地范围不断扩大,台地边缘滩和台内滩逐步向海槽方向推进,控制整个海槽南段的储层空间展布。

There are many important oil-gas resources in Feixianguan Formation of northeast Sichuan. The south sector of Liangping- Kaijiang ocean trough is very extensive and has many important potential off-gas resources. Based on an analysis of rock core, field cross section, logging, well logging and thin-section observation data, the authors studied the sequence-hthofacies paleogeographic characteristics of Feixianguan Formation in south sector of Liangping-Kaijiang ocean trough. The result indicates that the sedimentary model of the study area belongs to the attached land platform which includes the platform, sloping ground, and residual ocean trough facies. Based on the sequence interface identification, the authors divided the Feixianguan Formation into three third-level sequences, namely SQ1, SQ2, and SQ3. Each of the sequence is divided into three system tracts, i.e., TST, EHST, and LHST. With the system tract as the unit of the sequence-hthofacies paleogeographic map, this paper discusses in detail the hthofacies paleogeographic characteristics and evolution of various sequence system tracts. With the reduction of the ocean trough, the attached land platform expanded gradually, the platform edge beach and intra-platform beach gradually advanced to the ocean trough, which controlled the reservoir distribution.