东濮凹陷膏盐岩对烃源岩成烃演化的控制作用及其石油地质意义

东濮凹陷北部盐湖相膏盐岩极其发育，膏盐岩对烃源岩性质及生烃特征的影响研究薄弱。采用地质与地球化学相结合途径，探讨了含膏盐岩层系烃源岩特性及其成烃演化规律。结果表明，盐区与无盐区烃源岩的特性有很大差异，北部盐湖相含盐区深灰色、褐色等暗色页岩有机质丰度一般大于15%，有机质类型以Ⅱ1型和Ⅰ型为主，是区内主要的优质烃源岩；南部淡水湖相无盐区主要发育有利生气的Ⅱ—Ⅲ型干酪根，反映东濮凹陷烃源岩的质量及生烃潜能与膏盐岩的发育密切相关。观察到膏盐岩影响烃源岩的成烃演化进程，当膏盐层厚度为50 m时，生油窗的范围显著增加；随着盐岩厚度(>50 m)的增加，湿气窗的范围也逐渐增加；当膏盐岩厚度约400 m时，生油窗范围开始减小，湿气窗的范围仍有增加趋势。膏盐岩对烃源岩“生油气窗”的影响是基于其较高的热导率属性，通过影响地温场而实现。以地质解剖为依据，建立了文留地区含膏盐岩层系烃源岩成烃演化模式。东濮凹陷含膏盐岩层系烃源岩的演化特征对该凹陷及同类含膏盐岩盆地油气勘探具有重要指示意义。

Controlling Effects of Gypsum salt on Hydrocarbon Generation of Source Rocks in Dongpu Sag and Its Significance on Petroleum Geology

Gypsum salt rocks were extensively developed in the northern part of the Dongpu Sag, Bohai bay Basin.The effects of gypsum salt rocks on characteristics and hydrocarbon generation of source rocks are barely documented. Geological and geochemical methods were used to investigate such effects. Obvious differences were observed between the source rocks in the saline and non saline areas of the sag. Dark grey and brown shales in the north saline area are recognized as excellent source rocks with TOC content over 15%, dominated by kerogen type Ⅱ1 and Ⅰ of organic matter.Source rocks in the south fresh water lacustrine(non saline area) were dominated by kerogen type Ⅱ Ⅲ which is favourable for gas generation. This indicates that the property and hydrocarbon generation potential of the source rocks in the area are strongly controlled by gypsum salt rocks.It was also observed that hydrocarbon generation process of the source rocks is strongly influenced by gypsum salt rocks.Oil generation window would be expanded obviously when the thickness of gypsum salt is about 50 m.Both the oil and wet gas windows would be enlarged within a certain degree with increase of salt rocks thickness. The oil generation window would be narrowed when the thickness of salt rocks reached around 400 m,while wet gas window would be further enlarged. The effects of gypsum salt rocks on oil and gas generation windows of the source rocks were ascribe to their high thermal conductivity, which could influence geothermal field. Hydrocarbon generation modes for potential source rocks in the saline and non saline area were established based on a comprehensive study of geology and geochemistry. The models could have a great instructive significance to petroleum exploration in the Dongpu Sag and the similar salt bearing basins.