南海珠江口盆地流花地区珠江组碳酸盐岩埋藏酸性流体溶蚀机理初探

Initial Exploration Mechanism of Dissolution of Zhujiang Carbonates by Acid Fluids Under the Burial Condition in the Liuhua Area of the Pearl River Mouth Basin,South China Sea

以流花地区珠江组碳酸盐岩储集层抽提物GC、GC/MS分析为基础,结合区域构造运动史、地层水动力特征等,分析了该区埋藏酸性流体的成因与来源,探讨了"白垩状"灰岩的形成以及该区的埋藏酸性流体溶蚀模式。研究认为,埋藏酸性流体主要来自惠州凹陷文昌组烃源岩热演化成因有机酸,原油生物降解成因有机酸,岩浆活动生成的CO2等酸性流体。"白垩状"灰岩是在活跃油田底水环境下,主要由有机酸性流体长期溶蚀、浸泡和淘洗作用的结果。埋藏酸性流体以东沙构造运动形成的深大断裂及伴生的复杂裂缝网络为运移通道和物质交换空间,在流花低势汇流的强水动力条件下,与碳酸盐岩发生强烈的酸—岩反应,造成地层溶蚀垮塌,形成了现今流花地区灰岩坑的分布面貌。研究还排除了该区灰岩坑大气淡水溶蚀作用和白云岩化溶蚀作用成因的可能性。

This paper discussed the origin and source of acid fluids under burial condition,brought forward the new understanding of chalky limestones and the scheme model of burial dissolution by using GC and GC/MS to analyze extracts from Zhujiang carbonates,and investigated the regional tectonics and the dynamic characteristics of the formation water.We concluded that the acid fluids originated mainly from （1） pyrolysis of source rock from Huizhou depression（ 2 ）biodegradation of crude oil （3）CO2 and other acid fluids released from magmatism.The forming of chalky limestone was related to the continuous corrosion,soaking and washing by organic acid fluids.The burial acid fluids took the faults and complex fracture networks caused by the Dongsha movement as the migration channel and space for mass exchange,the strong acid-carbonate rock reaction took place under the active ground water condition of the Liuhua area,and then carbonate strata collapsed and the distribution of sink holes of the Liuhua area were formed. In addition,the possible causes of sinkholes-meteoric corrosion and dolomitization corrosion had been excluded after a systematic discussion.