南海南部陆缘地质流体类型及其油气成藏意义

Focused fluid flow systems and their implications for hydrocarbon accumulations on the southern margin of South China Sea

南海南部陆缘蕴藏着非常丰富的油气资源。为了解南海南部陆缘流体活动系统以及与油气藏之间的关系,以高精度2D地震资料为基础,对南海南部陆缘流体活动系统的类型、地震反射特征、以及对油气成藏的意义开展了研究。在南海南部陆缘发现了多种流体活动系统,包括:泥底辟/泥火山、气烟囱、管状通道、与构造断层相关的流体活动系统。这些流体活动系统具有不同的地震反射特征,常常出现含气强振幅异常带、弱振幅杂乱反射带以及"下拉"或者"上拱"地震反射形态等流体活动系统的标志特征。流体活动系统受到构造运动和沉积因素的影响,并且与深部高温高压塑性流体密切相关,流体活动系统优先发育在地层薄弱部位。流体活动系统及所伴生的断裂和裂隙常常作为油气富集区的运输通道;并且流体活动系统所运移的强溶蚀性流体和深部热液流体有利于油气储层的形成,特别是对于碳酸盐岩储层的改造尤为明显。因此,流体活动系统不仅能作为油气运移通道,也可以改善储层,对油气成藏具有重要意义。

The southern margin of South China Sea(SCS)has abundant hydrocarbon resources.Based on high-resolution2D seismic data,the authors conducted the research on various focused fluid flow systems and their seismic response,implications for hydrocarbon accumulations with the purpose of understanding the characteristics and their relations with hydrocarbon.Diverse focused fluid flow systems were identified,such as mud-diapir/mud-volcano,gas chimney,pipes and the focused flow fluid related fault.Different seismic characteristics are shown for these focused fluid flow systems,which include gas-bearing high-amplitude anomalous field,low-amplitude chaotic reflection,and“drop-down”/“arch up”reflections considered to be recognition marks of focused fluid flow systems that appear frequently.Focused fluid flow systems were affected by tectonic movement and sedimentation factors and were closely related to the deep high temperature and high pressure plastic fluid.Focused fluid flow systems were preferentially developed in the weak part of the strata.Focused fluid flow systems and associated faults and fractures were often used as transport channels for hydrocarbon accumulation zones.Moreover,the strong dissolved fluid and deep hydrothermal fluid transported by the fluid movement system were beneficial to the formation of reservoirs,especially the carbonate reservoirs.Focused fluid flow systems not only served as migration passage of hydrocarbons but also could improve reservoirs.Therefore,they are of great significance for hydrocarbon accumulation.