四川盆地德阳——安岳裂陷震旦系灯影组台缘结构特征与勘探方向

Structural features and exploration targets of platform margins in Sinian Dengying Formation in Deyang-Anyue Rift,Sichuan Basin,SW China

基于地震、测井及钻井等资料,对德阳—安岳裂陷及周缘震旦系灯影组台缘展布、结构类型、丘滩体成藏特征进行研究。研究表明:(1)德阳—安岳裂陷及周缘灯影组发育单阶断控型、多阶断控型、缓坡型和多期叠置型共4种台缘结构。(2)高石梯西—威远东地区灯影组二段(简称灯二段)发育单阶断控型台缘,呈近北东东向展布,受断裂和泥岩遮挡,形成断控-岩性圈闭。(3)乐至—蓬莱地区灯二段发育相互独立、多阶断控型台缘,呈北东向排列式展布,受同沉积断裂控制,丘滩体沿断裂上盘加积建隆,被滩间致密带和下寒武统烃源岩多方位遮挡,形成断控-岩性等复合圈闭。(4)威远—资阳地区灯二段发育缓坡型台缘,呈北西向展布,丘滩体多为薄互层连片带状,受上倾方向滩间致密带遮挡,形成岩性圈闭。(5)高石梯—磨溪—盐亭地区,灯影组二段、四段发育叠置型台缘,丘滩体加积叠置呈巨厚台缘建隆,受上倾方向滩间致密带和下寒武统泥岩封盖,在川中古隆起北斜坡形成规模岩性圈闭。蓬莱—中江区块、磨溪北—盐亭地区及威远—资阳地区的灯影组台缘丘滩体规模大,估算资源量1.58×1012m3,是四川盆地灯影组未来拓展勘探方向。

Based on the seismic,logging,drilling and other data,the distribution,structural types and mound-shoal hydrocarbon accumulation characteristics of platform margins of the Sinian Dengying Formation in the Deyang-Anyue Rift and its periphery were analyzed.Four types of platform margins are developed in the Dengying Formation,i.e.,single-stage fault-controlled platform margin,multi-stage fault-controlled platform margin,gentle slope platform margin,and overlapping platform margin.In the Gaoshiti West-Weiyuan East area,single-stage fault controlled platform margins are developed in the Deng 2 Member,which trend in nearly NEE direction and are shielded by faults and mudstones,forming fault-controlled–lithologic traps.In the Lezhi-Penglai area,independent and multi-stage fault controlled platform margins are developed in the Deng 2 Member,which trend in NE direction and are controlled by synsedimentary faults;the mound-shoal complexes are aggraded and built on the hanging walls of the faults,and they are shielded by tight intertidal belts and the Lower Cambrian source rocks in multiple directions,forming fault-controlled–lithologic and other composite traps.In the Weiyuan-Ziyang area,gentle slope platform margins are developed in the Deng 2 Member,which trend in NW direction;the mound-shoal complexes are mostly thin interbeds as continuous bands and shielded by tight intertidal belts in the updip direction,forming lithologic traps.In the Gaoshiti-Moxi-Yanting area,overlapping platform margins are developed in the Deng 2 and Deng 4members;the mound-shoal complexes are aggraded and overlaid to create platform margin buildup with a huge thickness and sealed by tight intertidal belts and the Lower Cambrian mudstones in the updip direction,forming large-scale lithologic traps on the north slope of the Central Sichuan Paleouplift.To summarize,the mound-shoal complexes on the platform margins in the Dengying Formation in the Penglai-Zhongjiang area,Moxi North-Yanting area and Weiyuan-Ziyang area are large in scale,with estimated resources of 1.58×1012m~3,and they will be the key targets for the future exploration of the Dengying Formation in the Sichuan Basin.