四川盆地东北部龙会场—铁山地区飞仙关组沉积演化与鲕滩储层分布规律

Sedimentary evolution and oolitic-shoal reservoir distribution of the Feixianguan formation in Longhuichang-Tieshan area,NE Sichuan basin

基于岩心、薄片、测井、地震等资料,研究四川盆地东北部龙会场—铁山地区下三叠统飞仙关组沉积相特征及演化过程,分析有利鲕滩储层分布规律。结果表明:飞仙关组时期,研究区具有西南高北东低、东陡西缓的古地貌特征,发育镶边碳酸盐岩台地沉积模式。受海平面持续下降的影响,台地沉积不断自西南向北东海槽方向扩展,飞一段晚期开始发育海退型鲕滩;飞二段时期围绕铁山地区、龙会场南部地区发育大面积台缘鲕滩及零星台内点滩;至飞三段台地稳定分布时期,台内鲕滩发育达到顶峰,主要分布于龙会场中北部井区,并在铁山地区以薄层、小范围分布。受沉积相及其演化控制,研究区发育多套台缘滩鲕粒云岩储层与台内滩溶孔鲕粒灰岩储层,储层发育位置随台缘及台内微地貌高地的迁移表现为横向迁移、纵向抬升的特征。有利储层多发育于飞二段台缘鲕滩亚相,铁山地区TS5、TS14井,与龙会场南部地区LH002-x2井及其周围沿NW—SE方向台缘带延展地带,是飞仙关组鲕滩储层最为有利的勘探区。

Based on cores,thin section,logging and seismic data,the sedimentary characteristics and evolution of the lower Triassic Feixianguan formation in Longhuichang-Tieshan area of northeastern Sichuan basin have been studied in detail,after which the distributions of favorable oolitic-shoal reservoirs have been analyzed.Results show that in the stage of the Feixianguan,a rimmed carbonate platform is developed in this area.The paleotopography of this area is featured by higher altitude in the southwest than that in the northeast and also steeper in the east than that in the west.Affected by the fall of relative sea level,carbonate platform continuously expands from southwest to northeast,during which regressive oolitic-shoals start growing in the late stage of T1 f1,then widespread platform marginal ooliticshoals distribute around Tieshan area and southern part of Longhuichang area in T1 f2.Sub-equently,the development of platform-interior oolitic-shoals peak in stage of T1 f3,mainly distributing in middlenorthern part of Longhuichang and locally in Tieshan area.Furthermore,multiple sets of reservoirs,including oolitic dolomite in platform marginal shoals and oolitic limestone in platform-interior shoals,are formed in the sedimentary evolution.Oolitic-shoal reservoirs uplift in vertical and spread in the direction along the migration of both platform marginal and platform-interior highlands.Comprehensive analysis demonstrates that favorable reservoirs often occur in platform marginal shoals of T1 f2.The area around wells TS5,TS14 in Tieshan,well LH002-x2 in southern Longhuichang and their surrounding stretch zones in platform margin region along NW-SE direction are the most favorable areas of oolitic-shoal reservoirs in Feixianguan formation.