珠江口盆地文昌A凹陷烃源岩特征及热成熟演化史

在烃源岩分布特征及有机质丰度、类型和成熟度分析的基础上,运用含油气盆地数值模拟技术,定量恢复了烃源岩热成熟演化史.研究表明,文昌A凹陷各层系烃源岩分布广,厚度大,有机质丰度高;有机质类型文昌组偏II1型,恩平组偏III型,二者现今多处于高成熟—过成熟阶段.凹陷内烃源岩成熟时间早(文昌组约45.5 Ma),成熟度高,以干气生成为主;凹陷边缘烃源岩成熟时间较晚(文昌组约30.0 Ma),成熟度相对较低,以石油生成为主.凹陷内气藏及凹陷边缘油藏的分布格局受制于有机质类型差异和不同的热演化史.气藏的天然气来自文昌组石油裂解气以及恩平组自身生成的天然气,油藏的石油来自文昌组和恩平组,且油气勘探的方向:凹陷内以天然气为主,边缘以石油为主.

CHARACTERISTICS AND THERMAL EVOLUTION HISTORY OF SOURCE ROCKS IN THE WENCHANG-A SAG,PEARL RIVER MOUTH BASIN

In order to better understand the process and mechanism of hydrocarbon accumulation and identify the source rock potential of Wenchang-A sag in Pearl River mouth basin, this study uses the technique of basin modeling to reconstruct the thermal evolution history in the study area based on the analysis of source rock distribution, organic matter abundance, types and maturation. The result shows that each layer of source rock of the Wenchang-A sag is widespread, with a high organic matter abundance and a large thickness. The organic matter of Wenchang Formation is of type Ⅱ1; while that of Enping Formation, type Ⅲ. The source rocks are in the stages of middle maturity and over maturity. Inside the Wenchang-A sag, the source rocks reached oil threshold in earlier time with a high maturity. However, on the edge of the sag, they reached oil threshold later, and is still in low maturation stage. The distribution of oil and gas in the sag is constrained by the different organic matter types and maturities. The pools of oil and gas come from Wenchang and Enping formations. The inside of the sag is a priority of gas searching, and the edge of the sag is favorable for petroleum.