台缘带特征、形成主控因素及其对油气成藏的控制：以四川盆地灯影组为例

谢武仁　杨　威　汪泽成　魏国齐　马石玉

郝　涛　苏　楠、李文正　武赛军　王小丹

（中国石油勘探开发研究院 北京 100083）

摘　要　通过大量二维地震和三维地震资料的解释，结合已钻井资料的分析，刻画了绵竹—长宁裂陷两侧台地边缘的形态变化，探讨了不同地区台缘带沉积模式，研究了不同类型台缘带形成分布的控制因素，建立了3种成藏模式。研究结果表明：1）绵竹—长宁裂陷两侧发育灯二段和灯四段台缘带，灯二段台缘带呈现U型展布，灯四段台缘带呈现近平行分布；2）灯影组受断裂控制，经历了灯一+二期双断裂陷及灯三+四期箕状裂陷两个阶段演化；结合台地边缘形态，可分为陡坡型和缓坡型2大类台缘带，进一步划分出陡坡带加积型、缓坡带退积型、缓坡带加积型等3种类型；3）台缘带类型差异主要与断裂发育的规模大小相关，断裂发育区，形成陡坡带台缘，断裂不发育区，形成缓坡带台缘；古隆起核部，形成加积型台缘，远离古隆起区，形成退积型台缘；4）裂陷两侧发育台缘丘滩岩溶型储层，裂陷内沉积优质的下寒武统筇竹寺组烃源岩，两者有机匹配，形成陡坡带、缓坡带台缘2类成藏模式。目前勘探主要集中在陡坡带台缘，缓坡带台缘分布范围广，是未来的勘探重点部位。

关键词　克拉通内裂陷　台缘带类型　形成主控因素　丘滩储层　成藏模式　灯影组　四川盆地

  doi: 10.12017/dzkx.2021.045

Characteristics and main controlling factors on the development of a platform margin belt and its effect on hydrocarbon accumulation: A case study of Dengying Formation in Sichuan Basin

Abstract：Based on the interpretation of two-dimensional and three-dimensional seismic data, combined with the analysis of drilling data, the geomorphologic changes of platform margins on both sides of Mianzhu-Changning rift are described, the various sedimentary models of platform margin at different locations are established, and the controlling factors on different types of platform margin belt are discussed. Eventually, three hydrocarbon accumulation models are proposed. The results show that: (1) Z2dn2 and Z2dn4 platform margin belts are developed on both sides of Mianzhu-Changning rift, the platform margin belt of Z2dn2 member is U-shaped, while the platform margin belt of Z2dn4 member is nearly parallel distributed; (2) The development of Z2dn Formation is controlled by faults, and has undergone two stages of development: the Z2dn1+2 double-rift stage and Z2dn3+4 asymmetrical half graben stage. According to the geomorphology of the platform margin, it can be divided into steep slope type and gentle slope type, and can be further subdivided into three types: the type of aggradation on steep slope, the type of retrogradation on gentle slope, and the type of aggradation on gentle slope; (3)The type of platform margin is mainly related to the degree of fault development; the steep slope belt platform margin develops in the area with fault development , while the gentle slope belt platform margin develops in the area without fault development; the aggradational platform margin develops near the core of the paleo-uplift, the retrogradational platform margin develops away from the paleo-uplift; (4)The karst reservoirs on platform margin are developed on both sides of the rift, , and the source rock of Є1q is deposited within the rift, the combination of them results in two types of hydrocarbon accumulation model on platform margin: steep slope belt type and gentle slope belt type. Currently, the exploration is mainly concentrated on the steep slope belt. However, the gentle slope belt platform margin is widely developed, which could be the key target of future exploration.

Keywords　Intracratonic rift，Types of platform margin belt，Main controlling factors，Mound-shoal reservoir，Hydrocarbon accumulation model，Dengying Formation，Sichuan Basin

   近年来，大量研究及钻探结果表明，碳酸盐岩台地类型、台缘带特征及叠置关系对储层的形成具有重要的控制作用，特别是台缘丘滩型白云岩是世界范围内油气勘探开发效果最好的领域之一，多位学者对此进行了研究和探讨（Droxler et al，2001；Isern and Anselmetti，2001；Cruz and Eberli，2008；顾家裕等，2009；彭博等，2010）。四川盆地震旦系油气勘探始于20世纪50年代，迄今已有70余年勘探历史，勘探历程曲折漫长（罗志立，1983；宋文海等，1996；李国辉等，2000；李晓清等，2001；姚建军等，2003；刘树根等，2012；汤济广等，2013），2011年在川中高石梯—磨溪地区部署的高石1井获突破后，通过大量的地震与钻井资料，发现绵竹—长宁大型克拉通内裂陷，裂陷内沉积厚层烃源岩，裂陷两侧发育碳酸盐岩台地边缘带，台地边缘带上发育厚层丘滩白云岩储层，源储对接，成藏组合优越，取得了一系列研究成果与认识（徐春春等，2014；张健等，2014；邹才能等，2014；周进高等，2015），但是对于裂陷两侧台缘带的沉积结构和构型的差异性及其控制因素研究相对较少，进而影响了对于台缘带精细认识和有利区带及成藏模式的划分。因此，本文在前人研究基础上，通过22口井岩心详细观察和28 000 km二维地震剖面、7 600 km²三维地震资料的精细解释，系统刻画了裂陷两侧台缘带的展布，分析不同地区台缘结构类型，探讨了川中古隆起与断裂对台缘带类型的控制作用，提出了不同类型台缘带的成藏模式，指出了四川盆地震旦系灯影组下一步有利的勘探区带。

图1　上扬子震旦纪—早寒武世克拉通内裂陷发育范围

Fig. 1　Development range of rifts in Sinian-Early Cambrian craton of Upper Yangtze

图2　灯影组连井沉积相对比剖面（龙王庙组顶界拉平）

Fig. 2　Correlation section of sedimentary facies of connecting wells in Dengying Formation（the top boundary of Longwangmiao Formation is flattened）

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