东海盆地西湖凹陷天然气及原油地化特征分析

Geochemical characteristicsof natural gases and crude oils in the Xihu Sag of East china Sea Basin

曹倩 徐旭辉 曾广东 周小进 江平 王岭

Cao Qian Xu Xuhui Zeng Guangdong Zhou Xiaojin Jiang Ping Wang Ling

中国石化 石油勘探开发研究院 无锡石油地质研究所, 江苏 无锡 214151 2. 中国石化 上海海洋油气分公司, 上海 200120

Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China 2. SINOPEC Shanghai Marine Petroleum Branch, Shanghai 200120, China

对西湖凹陷天然气组分、轻烃、碳同位素等特征进行了系统地分析,结果表明天然气类型以煤型气与油型气的混源气为主且偏煤型气,其演化成熟度较高,属于Ⅱ型偏煤型母质成熟—过熟阶段的产物,主要来源为平湖组及其下部的烃源岩。通过对原油的物性、饱和烃、碳同位素、轻烃等特征的研究表明,西湖凹陷原油可分为轻质原油与凝析油2种类型。这2种类型原油物性一致,母质来源均有煤的贡献,形成于弱还原的淡水湖沼环境;原油可以分为成熟(Ro<1.0%)和高熟—过熟(Ro=1.3%~2.0%)2种类型。

Studies of the composition, light hydrocarbons and carbon isotopes of natural gases from the Xihu Sag showed that the gases were a mix of coal-type (accounting for the major proportion) and oil-type gases havinghigh maturities.They were mainly derived from type II source rocks in the PinghuFormation and underlying formations during the mature and over-mature stages.Crude oils from the Xihu Sag were classified into light oils and condensates according to studies of their physical properties, saturated hydrocarbons, carbon isotopes and light hydrocarbons.These two types of crude oil showed similar physical properties suggestive of acoal origin, and were generated in fresh water lakeswith weakly anoxic conditions.Some of the crude oils were mature (Ro<1.0%)and some are high-to over mature (Ro=1.3%~2.0%).

中海石油(中国)有限公司科研项目"东海西湖凹陷中央背斜带成藏主控因素研究"(34000000-12-ZC0613-0004)资助。

https://doi.org/10.11781/sysydz201505627