摘要
四川盆地中部地区下寒武统龙王庙组混合沉积较发育,但相关的研究和认识尚显薄弱。通过岩心观察描述和岩石学分析,对川中地区下寒武统龙王庙组混合沉积特征和地质意义进行研究。研究结果表明,研究区龙王庙组混合沉积主要为混积型碳酸盐岩,发育碳酸盐岩-混积岩层系与混积岩层系,具有渐变式混积和复合式Ⅱ型混积两种类型。纵向上,混合沉积受海平面变化控制,主要发育在三级海平面旋回的海侵期和海退早期,与风暴事件密切相关,且海侵期混积程度明显高于海退期;横向上,高石梯地区混积强度大于磨溪地区。通过四川盆地中部与北部地区龙王庙组混合沉积特征的对比,发现川北地区与古秦岭洋、摩天岭古陆相接,混积强度与混积颗粒粒度均大于川中地区,指示风暴潮流携带陆源碎屑经川北进入川中地区。四川盆地中部地区龙王庙组混积岩指示高石梯地区处于古地貌斜坡部位,粉砂级石英颗粒卸载形成混积中心。龙王庙组有利储层主要发育在弱混积或未混积颗粒滩微相中,混合沉积不利于优质储层的发育。
The mixed siliciclastic and carbonate sediments that prevail the Lower Cambrian Longwangmiao Formation in the central Sichuan Basin are poorly understood.Their characteristics and geological significances are therefore focused in this study through core description and petrologic analysis.The results show that mixed carbonate-siliciclastic deposition dominates the formation as carbonate-mixed carbonate-siliciclastic sequences and mixed carbonate-siliciclasitic sequences in gradually mixing or type II composite mixing styles.Vertically,the sediments are clearly storm-related and controlled by sea level variations in transgression and early regression stages of the third-order eustatic cycle with the mixing range much larger in transgression than that in regression stage.Horizontally,the sediments show higher mixing intensity in the Gaoshiti area than in the Moxi area.A characteristic comparison between the sediments of the formation in the central and northern Sichuan Basin reveals that sediments in the northern part of the basin have higher mixing intensity and greater granular size due to its adjacency to the Qinling Palaeocean and Motianling Palaeoland and a possible influx of terrigenous debris brought by storms through the north part to the center.The mixed sediments in the central Sichuan Basin indicate that Gaoshiti area was lying on a palaeo-slope where silty quartz grains were unloaded to form a mixing deposition center.It is also highly possible that quality reservoirs in the formation occur mostly in the weakly to non-mixing sediments of shoal facies,since highly mixed sediments are not suitable for the formation and development of such reservoirs.
作者
宋金民
张亚雄
尹柯惟
刘树根
陈宗于
李智武
田艳红
孙玮
刘颖
金鑫
赵玲丽
Song Jinmin;Zhang Yaxiong;Yin Kewei;Liu Shugen;Chen Zongyu;Li Zhiwu;Tian Yanhong;Sun Wei;Liu Ying;Jin Xin;Zhao Lingli(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Petroleum Exploration and Production Research Institute,SINOPEC,Beijing 100083,China;Exploration and Development Research Institute of Huabei Oilfield Company,PetroChina,Renqiu,Hebei 062552,China;Xihua University,Chengdu,Sichuan 610039,China;Southwest Branch Company of East Geophysical Company,CNPC,Chengdu,Sichuan 610213,China;Sichuan Geology and Mineral Exploration and Development Bureau of 405 Geological Team,Chengdu,Sichuan 611830,China)
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2021年第3期627-638,701,共13页
Oil & Gas Geology
基金
国家自然科学基金项目(41872150,41472107)
四川省科技厅重点研发项目(2018JZ0078)
中石化前导性项目(P16109)
成都理工大学中青年骨干教师培养基金项目(10912-KYGG201505)。
关键词
混合沉积
沉积环境
地质意义
龙王庙组
寒武系
四川盆地
mixed sediment
sedimentary setting
geological significance
Longwangmiao Formation
Cambrian
Sichuan Basin
作者简介
第一作者:宋金民(1983-),男,博士、副教授,碳酸盐岩沉积储层。E-mail:songjinmin@sohu.com。
