古气候和海平面变化对浅水碳酸盐岩高频层序及有利储层的控制——以川中地区龙王庙组为例  

Controls of paleoclimate and sea-level changes on the high-frequency sequence of shallow-water carbonates:A case study of the Longwangmiao Formation in the central Sichuan Basin

作　　者：赵玉茹 高达[1] 胡明毅[1] 郑超 李佳 谢武仁[5] ZHAO Yuru;GAO Da;HU Mingyi;ZHENG Chao;LI Jia;XIE Wuren(School of Geosciences,Yangtze University,Wuhan 430100,Hubei,China;South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,Guangdong,China;University of Chinese Academy of Sciences,Beijing 100049,China;Research Institute of Exploration and Development,PetroChina Southwest Oil and Gas Field Company,Chengdu 610000,Sichuan,China;Research Institute of Petroleum Exploration and Development,PetroChina,Langfang 065007,Hebei,China)

机构地区：[1]长江大学地球科学学院,湖北武汉430100 [2]中国科学院南海海洋研究所,广东广州510301 [3]中国科学院大学,北京100049 [4]中国石油西南油气田勘探开发研究院,四川成都610000 [5]中国石油勘探开发研究院,河北廊坊065007

出　　处：《中国地质》2024年第2期577-591,共15页Geology in China

基　　金：国家自然科学基金(41502104);湖北省自然科学基金(2017CFB533);油气资源与勘探技术教育部重点实验室开放基金(K2018-06)联合资助。

摘　　要：【研究目的】阐明古气候和海平面变化对浅水碳酸盐岩高频层序及有利储层的控制机制,对明确储层成因和分布规律具有重要意义。【研究方法】以川中地区龙王庙组为例,在沉积相及层序地层分析的基础上,通过全井段取心的碳氧同位素、主量和微量元素测试,恢复了海平面和古气候变化并开展了综合讨论。【研究结果】龙王庙组主要发育云质潟湖、滩间海、颗粒滩和云坪4种沉积微相,可清晰识别可区域对比的两个四级层序。龙王庙组的δ^(13)C具有两个变化周期,指示两次海平面升降,这与Al_(2)O_(3)、TiO_(2)、B和V元素变化所反映的古水深变化一致。碳和氧同位素估算的古海水Z值和温度,以及Mg、Ca良好的相关性,共同反映干旱炎热气候和亚热带海洋环境;MgO/CaO、MnO_(2)、Fe_(2)O_(3)/MnO_(2)和Al_(2)O_(3)/MgO的规律性变化,指示两个层序早期的气候短暂过渡为温暖潮湿;Sr/Ba值反映沉积晚期海水盐度明显增高。【结论】气候温暖潮湿和海平面快速上升期形成海侵体系域;气候炎热干旱时,颗粒滩和云坪快速沉积构成高位体系域。高位域上部的滩—坪体系是优质储层的物质基础,在海平面下降和干热气候控制下发生的早期溶蚀和白云化作用是储层改善的关键。[Objective]Clarifying the control mechanisms of ancient climate and sea level changes on high-frequency sequences and favorable reservoirs of shallow water carbonate rocks is of great significance for clarifying the genesis and distribution patterns of reservoirs.[Methods]Microfacies and sequence stratigraphy analysis and geochemical analysis including carbon and oxygen isotopes,major and trace elements with core samples were used.[Results]The Four types of microfacies including dolomitic lagoon,inter-shoal,grain shoal and tidal flat were identified in the Longwangmiao Formation.The Formation was subdivided into two fourth-order sequences which was regionally correlated.Theδ^(13)C of the Longwangmiao Formation vertically shows two periodical changes,which indicates two episodes of sea-level changes.This trend of sea-level change is consistent with the change of water depth reflected by the variations of Al_(2)O_(3),TiO_(2),B and V values.Using carbon and oxygen isotopes coupled with the well-correlated Mg and Ca values,the estimated Z values and seawater temperaturesduring the deposition of the Formation collectively reflect arid and hot climates and a subtropical marine environment.Systematic variations in MgO/CaO,MnO_(2),Fe_(2)O_(3)/MnO_(2),and Al_(2)O_(3)/MgO values indicate a brief transition to warm and humid conditions during the early stages of the two successions,and the Sr/Ba values reflect the marked increase in late-stage seawater salinity during deposition.[Conclusions]A warm and humid climatecoupled with a rapid rise in sea level,led to the formation of transgressive systems tracts.During the hot and arid climates,rapid deposition of grain shoals and dolomitic tidal flat constitutes the highstand systems tracts.The grain shoal and dolomitic tidal-flat deposits serves as the material basis for high-quality reservoirs.Early dissolution and dolomitization processes occurring during sea-level fall and a hot and arid climate are crucial for reservoir development.

关 键 词：高频层序 元素地球化学 碳、氧同位素 海平面变化 古气候 龙王庙组 油气勘查工程 四川盆地 

分 类 号：P618.13[天文地球—矿床学]