利用流体历史分析技术研究渤海海域黄河口凹陷北部陡坡带油气成藏过程

基于流体历史分析技术的成藏过程反演对含油气系统的持续勘探具有重要意义。本文应用包裹体岩相学、均一温度、储层定量荧光等技术和方法,对渤海海域黄河口凹陷北部陡坡带沙河街组储层中的流体包裹体进行了深入研究,在此基础上,剖析了油水界面变迁,再结合生烃史和有机地球化学资料研究了北部陡坡带沙河街组储层的油气成藏史。结果显示,黄河口凹陷北部陡坡带具有2期源自沙河街组烃源岩的油气充注,第Ⅰ期充注时间为7 Ma,表现为褐色低熟的轻-中质单一液相烃类包裹体;第Ⅱ期开始于2Ma,沙河街组烃源岩大量生烃,表现为浅蓝色荧光的中质气液两相烃类包裹体,为主要成藏期。储层定量荧光样品QGF大多体现古油层荧光光谱特征,油藏规模较大,后期由于构造活动油藏泄漏,形成现今3885 m典型的油水界面。黄河口凹陷北部陡坡带的构造活动与烃源岩生排烃史的时间匹配决定了研究区两期充注,后期为主的成藏特点。新构造运动后期,古油藏规模减小,形成了现今油藏格局。

Restore the Hydrocarbon Accumulation Process by Using Fluid Inclusion Analysis Techniques in the Northern Steep Slope Belt of Huanghekou Sag, Bohai Sea

Hydrocarbon accumulation process obtained from fluid history analysis techniques is of great significance to the continuous exploration of petroleum system. Based on the observation of reservoir petrography, homogeneous temperature and quantitative grain fluorescence technique, the fluid inclusion characteristics, oil-water interface and charging history of northern steep slope belt of Huanghekou Sag have been studied comprehensively, combined with hydrocarbon geochemical analysis and burial history reconstruction.The result shows that there are two period hydrocarbon accumulations from the source rocks of the Shahejie Formation. The beginning of the first phase of hydrocarbon accumulation is about 7 Ma, represent by brown colors and single liquid phase hydrocarbon inclusion and without fluorescence, low maturity and light-medium density. The second stage of hydrocarbon charging represented as gas-liquid two phase hydrocarbon inclusions, medium density and show pale blue fluorescence colors, which is the main hydrocarbon charging phase of northern steep slope belt of Huanghekou Sag .The quantitative grain fluorescence (QGF) index of most quantitative grain fluorescence samples are greater than 4 which shows large scale reservoir, while the palaeo-oil zones leaked recently and the oil - water interface down to 3 885 m by quantitative grain fluorescence on extract (QGF-E) data. The tectonic evolution background of steep slope zone in the north of huanghekou sag controls the evolution characteristics of hydrocarbon source rocks to some extent.The characteristics of charging history of study area is two periods of filling, mainly the at late stage and adjusted recently, which determined by the matching of tectonic activity period and hydrocarbon generation and expulsion history.