南海油气藏类型及分布规律

Types and distribution of oil and gas reservoirs in the South China Sea

通过对南海周边新生代板块活动的分析,认为南海构造演化由太平洋板块、欧亚板块和印度板块等3大板块间的相互作用所控制,并可分为断陷阶段(E)、断拗转换阶段(N11—N12)和区域性沉降阶段(N13—现今)。将南海已发现油气藏归纳为构造圈闭型、岩性圈闭型和复合型3大类,进一步将构造圈闭型分为背斜型、断背斜型、断块(鼻)型3个亚类,将岩性圈闭型分为生物礁滩型和深水水道型2个亚类,将复合型分为构造-岩性型和基岩潜山型2个亚类,并对典型油气藏特征进行了分析。总结了南海油气藏在平面和纵向上的分布特征,认为南海演化的不同阶段形成了不同的圈闭类型和不同的储层,从而控制了3大类油气藏的分布。平面上,构造型油气藏主要分布在南海的南北两侧靠近大陆边缘地区,以油为主;生物礁滩型油气藏分布在远陆缘区,以气为主;而西部的走滑断陷盆地除了发育构造型油气藏,还发育复合型油气藏,西北部以构造-岩性型为主,西南部基岩潜山型占优势。纵向上,构造型、生物礁滩型油气藏发育均有北早南晚的特点;西部走滑盆地复合型油气藏发育层位北部比南部更新;深水水道型油气藏集中在上中新统—上新统,发育层位最新。

Based on the analysis of the Cenozoic plate activity around the South China Sea(SCS),it is considered that the tectonic evolution of the SCS is controlled by the interaction among the three plates of the Pacific,Eurasia and India,and can be divided into three stages:rifting stage(E),fault-depression transition stage(N11—N12)and regional subsidence stage(N13—present).The discovered oil and gas reservoirs in the SCS can be divided into three types:structural type,lithologic type and composite type.Futher,the structural type can be divided into anticline type,fault-anticline type and fault block(nose)type;the lithologic type can be divided into reef beach type and deepwater channel type;the composite type can be divided into structural-lithologic type and bedrock buried-hill type.It is considered that the three stages of tectonic evolution control the formation of different types of traps and reservoirs,thus controlling the distribution of three types of oil and gas reservoirs.Structural reservoirs are mainly distributed in the southern and northern sides of the SCS near the continental margin,most of which are oil fields;reef-beach reservoirs are distributed far from the continental margin,most of which are gas fields.In strike-slip fault basins in the west of SCS,not only structural reservoirs but also complex reservoirs developed.The structural and reef-beach reservoirs have the characteristics of forming early in north and late in south.In the west strike-slip basin,many composite oil and gas reservoirs developed,with structure-lithology being dominant in northwest,with the bedrock buried-hill being dominant in southwest,which developed early in the south than in the north.Deep-water channel reservoirs are concentrated in the Upper Miocene—Pliocene latest.