摘要： 埃迪卡拉(震旦)系是元古代第2次大氧化事件(NOE)后形成的具有良好生储盖条件的碳酸盐岩沉积组合,已在四川盆地获得原生气藏勘探重大突破,但德阳—安岳台内裂陷及周缘区灯影组划分对比尚不统一,制约了对台缘带丘滩体横向分布特征的认识。基于露头、钻井和地震资料,通过岩石学、电性和地球化学特征分析,开展了灯影组地层层序重新厘定,在此基础上对灯影组岩相古地理进行了重建,取得以下研究成果: (1)建立了宁强胡家坝灯影组典型剖面,明确了灯影组分段岩性组合特征,指出高石131X、中江2、蓬探1井原划分的灯二段应归属灯四段,台缘带灯四段具有三分性,特征明显,并构建了等时地层格架。 (2)明确了等时地层格架内丘滩体迁移规律,即德阳—安岳台内裂陷东段灯四段台缘丘滩体垂直相带展布方向呈由东向西进积、平行相带方向呈由南向北迁移特征,灯四下亚段丘滩体发育于南部的川中古隆起一带,灯四中亚段丘滩体发育于中部太和区块,灯四上亚段丘滩体则发育于北部的宁强区块。(3)根据灯四下、中、上亚段构造-岩相古地理特征,预测了德阳—安岳台内裂陷及周缘灯影组有利储集层展布,对指导天然气勘探具重要意义。川中古隆起、太和区块和宁强区块均位于震旦纪同一台缘带上,南部的川中古隆起已探明安岳万亿立方米大气田,中部的太和区块含气规模达万亿立方米的大气区已初步明朗,北部的宁强区块也具备形成万亿立方米大气区的有利条件。

关键词: 等时地层格架, 台缘丘滩体, 岩相古地理, 灯影组, 德阳—, 安岳台内裂陷, 四川盆地

Abstract: The Ediacaran(Sinian)stratum is a carbonate sedimentary assemblage with good source-reservoir-cap conditions formed after the Proterozoic Second Great Oxidation Event(NOE),where a major breakthrough had been made in the exploration of primary gas reservoirs in the Sichuan Basin. The stratigraphic division and comparison of the Dengying Formation in the Deyang-Anyue intra-platform rift and the surrounding area are not uniform,which restricts the understanding of the lateral distribution characteristics of the mounds and shoals in the platform margin. Based on drilling,outcrop and seismic data,through petrological,electrical and geochemical analysis,this paper carried out the re-determination of the Dengying Formation stratigraphic sequence. On this basis,the lithofacies palaeogeography of the Dengying Formation was reconstructed,and the followings were concluded: (1)The Dengying Formation standard profile and segmented lithologic assemblages in Hujiaba(Ningqiang County, Shaanxi Province) area were established,and it was pointed out that the strata in Wells Gaoshi-131X, Zhongjiang-2 and Pengtan-1 were originally classified as the Member 2 should belong to the Member 4 of Dengying Formation,and the Member 4 on the platform margin is trichotomous with distinctive features,and the isochronous stratigraphic framework was constructed. (2)The migration law of the mounds and shoals within the isochronous stratigraphic framework was clarified,that is,in the eastern segment of the Deyang-Anyue intra-platform rift,the Member 4 of Dengying Formation platform margin mounds and shoals prograde from east to west,while in a direction perpendicular to the facies belt,they shifted from south to north. The mounds and shoals of the lower,middle and upper sub-member of the Member 4 of Dengying Formation are developed in the south of central Sichuan paleo-uplif,in the Taihe area in the center of the basin,and in the Ningqiang area in the north of basin,respectively. For this,three tectonic-lithofacies palaeogeographic maps were compiled for the lower,middle and upper sub-members of the Member 4 of Dengying Formation. (3)The above understanding is of great significance for the prediction of favorable reservoir distribution in the Deyang-Anyue intra-platform rift and the surrounding Dengying Formation and for guiding natural gas exploration. Central Sichuan paleo-uplift,Taihe area and Ningqiang area are all located on the same platform margin belt in Sinian. In the Central Sichuan Paleo-uplift in the south,the Anyue trillion cubic gas field has been discovered,and a gas block at a scale of one trillion cubic meters has been preliminarily determined in the Taihe area in the center,and the Ningqiang area in the north also has favorable conditions to form a trillion-cubic-meter gas large block,which is worth looking forward to.

Key words: isochronous stratigraphic framework, platform margin mounds and shoals, lithofacies palaeogeography, Dengying Formation, Deyang-Anyue intra-platform rift, Sichuan Basin

中图分类号: 

• P531

• P534