北部湾盆地海中凹陷流体动力场特征及油气成藏意义

Characteristics of Fluid Dynamic Field and Its Significance to the Accumulation of Hydrocarbons in Haizhong Sag of Beibuwan Basin

王修平 李倩 陈晶

WANG Xiuping LI Qian CHEN Jing

中国石油化工股份有限公司上海海洋油气分公司勘探开发研究院, 上海 200120; 中国石油化工股份有限公司上海海洋油气分公司, 上海 200120

Institnte of Exploration and Development, SINOPEC Shanghai offshore Oil & Gas Company, Shanghai 200120, China; SINOPEC Shanghai Offshore Oil & Gas Company, Shanghai 200120, China

海中凹陷位于北部湾盆地北部坳陷南部，油气成藏条件优越，具有良好的勘探前景。此文以油气成藏动力学理论为指导，采用盆地数值模拟与油气地质综合分析相结合的研究方法，分析了海中凹陷温度场、压力场、势能场及应力场等流体动力场特征，剖析了流体动力场与油气成藏的关系，为油气成藏动力学深入研究奠定了基础。结果表明，海中凹陷具有较高的今、古地温场，埋藏较深的洼槽带流沙港组中深湖相泥岩段存在异常超压，其形成及演化具有良好的继承性；洼槽带为高势能区，成熟烃源岩生成的油气在势能差的驱动下向斜坡区等相对低势区运移、汇聚及成藏；古近纪时期，张性正断层发育，有利于油气的垂向运移，晚中新世挤压反转作用强烈，有利于油气的保存。

Haizhong Sag, located in the south part of North Depression of Beibuwan Basin, is considered to be quite good in the geological conditions for hydrocarbon accumulation and favorable for the exploration. Under the guidance of the dynamic theory for hydrocarbon accumulation, the authors, based on the integrated study of basin modeling technique and petroleum geology, analyzed the characteristics of fluid dynamic field including geothermal field, pressure field, fluid potential field and stress field, dissected the relationship between the fluid dynamic field and hydrocarbon accumulation, laid a foundation for the deep understanding on dynamics of hydrocarbon accumulation in Haizhong Sag. The study indicates that both of the present geothermal field and paleo-geothermal field are characterized with relative higher temperature in the Haizhong Sag. The abnormal high pressure is mainly distributed in the deeply buried mudstone interval of middle-deep lacustrine facies Liushagang Formation of the sag, and the abnormal high pressure evolution was successive in the geological history. The potential energy difference could drive hydrocarbon generated from mature source rock from high potential area in the sag to the lower potential area and accumulate. There are many normal faults in Middle Eocene, which are beneficial to the hydrocarbon vertical migration. The strong compressional inverse occurred in late Miocene is favorable to the hydrocarbon preservation.

https://doi.org/10.3969/j.issn.1008-2336.2017.03.001