南海流花碳酸盐岩台地珠江组礁灰岩埋藏溶蚀作用  

BURIAL DISSOLUTION OF ZHUJIANG REEF LIMESTONE ON THE LIUHUA CARBONATE PLATFORM,SOUTH CHINA SEA

作　　者：江凯禧[1] 何文祥[2] 彭丽 陈祖林[2] 朱俊章 向念[1] 

机构地区：[1]中海油能源发展股份有限公司工程技术分公司非常规技术研究院,天津300452 [2]长江大学地球环境与水资源学院,武汉430100 [3]中海油实验中心,天津300452 [4]中海石油有限公司深圳分公司技术部,广州510240

出　　处：《海洋地质与第四纪地质》2015年第2期61-71,共11页Marine Geology & Quaternary Geology

基　　金：国家科技重大专项大型油气田及煤层气开发(2011ZX05033004-003)

摘　　要：南海流花碳酸盐岩台地近年来利用高精度3D地震资料处理解释技术,新发现珠江组礁灰岩地层发育数量众多的灰岩坑,平面上沿NWW向断层分布。由于灰岩坑的形成导致该区储层非均质性增强,油气成藏更加复杂,给油气勘探带来诸多困难和挑战。以岩心抽提物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,分析该区埋藏酸性流体的成因与来源;并对"白垩状"灰岩成因提出新的认识,探讨了研究区埋藏酸性流体溶蚀模式。研究认为,埋藏酸性流体主要来源于:(1)烃源岩内有机质热演化作用及其生成的烃类与矿物和水的有机无机氧化作用,(2)原油运移过程中在输导层内的有机无机氧化作用,(3)油藏内原油的生物降解作用等形成的有机酸性流体。研究表明原油生物降解成因有机酸浓度可达4 300μg/g油以上。流花碳酸盐岩台地上发育的"白垩状"结构灰岩,是在活跃地层水动力条件下,由有机酸性流体长期溶蚀、浸泡和淘洗形成。在含油层段内发育的致密夹层,仅外部受酸性流体溶蚀改造而内部未受影响部分仍保留致密结构而未能形成"白垩状"灰岩。埋藏可溶性有机酸性流体在活跃的地层水动力条件下,通过复杂的裂缝网络发生运移,在断层和裂缝最发育区岩体破碎,酸-岩反应空间最大,速率最高,造成碳酸盐岩地层溶蚀垮塌,从而形成沿NWW向断裂体系分布的灰岩坑。A number of sinkholes have been discovered in the Zhujiang reef limestone on the Liuhua carbonate platform,South China Sea,by high resolution 3Dseismic survey.Most of the sinkholes occur along the faults in NWW direction.The high heterogeneity of reservoir caused by sinkholes has much increased the complexity of hydrocarbon distribution,and thus the difficulties and challenges in exploration.In this paper,we discussed the origin of the sinkholes in the chalk-like limestone and the source of acid fluids after burial,studied the burial dissolution based upon the GC,GC/MS extracts from the Zhujiang reef limestone as well as the regional tectonics and the dynamic characteristics of formation water.It is concluded that the acid fluids are mainly from：①pyrolysis of organic matter and interactions of organic-inorganic matters with hydrocarbon in source rocks;②oxidation of oil compounds and generation of organic acids in the process of migration;③biodegradation of oil in reservoirs,and the concentration of organic acids generated by biodegradation may reach the value of 4 300μg/g oil.The chalky limestone is formed by the continuous corrosion,soaking and washing by organic acid.Tight limestone layers found in the oil-bearing zone are caused by partial solution of the external part by acidic fluid with the inner part remaining unaffected.The acid fluids migrated together with active formation water along complex fracture networks.Therefore,along the faults and fractures and in the areas of broken strata,there is more space and highest acid-rock interaction.With the collapse of carbonate strata,sinkholes are formed.

关 键 词：酸性流体 埋藏溶蚀作用 礁灰岩 流花碳酸盐岩台地 

分 类 号：P744[天文地球—海洋科学]