桦甸盆地桦甸组油页岩成烃生物组成及生烃潜力

摘要

A set of high-quality oil shales developed in the Eocene Huadian Formation in the Huadian Basin,Jinlin Province.Twenty-two rock samples were collected from the Guanglangtou district for bio-precursor and hydrocarbon generation potential analyses.Two samples containing different types of algae were chosen for thermal simulation.The Huadian shale has a high TOC content(10.6%-39.6%)and a high Rock-Eval hydrogen index(HI)value (887 mg/g),suggesting a good hydrocarbon generation potential. Detailed bio-precursor analyses demonstrated that the organic matter was dominated by phytoplankton,such as lamalginite and telalginite(including botryococcus and diatom),and fragments from benthic macroalgal rhodophyte were found in some thin layers. Higher plants mainly include detrital vitrinoids,fungi and detrital plastids,and sporophytes. The sample HD-20 with more benthic algae produced the maximum amount of hydrocarbon(427 mg/g)at 400℃C(Ro=1.02%),while the sample HD-21 dominated by planktonic algae produced the maximum amount of hydrocarbon(909 mg/g)at 425℃C(Ro=1.18%). Thermal simulation experiments showed that the sample HD-21 had a much higher hydrocarbon generation poten-tial than the sample HD-20,even though the TOC content of HD-20 was much higher,indicating that the benthic macroalgal macerals have a much lower capacity to generate oil when thermally mature.%桦甸盆地始新统桦甸组中发育一套优质油页岩.利用显微镜及扫描电镜对该盆地光榔头矿区22个样品进行分析,并对2个含不同藻类的样品进行生烃热模拟实验,研究其成烃生物特征及生烃潜力.桦甸油页岩有机碳含量很高(10.6%~39.6%),氢指数含量高达887 mg/g,显示该套油页岩具有很好的生烃潜力.生物来源主要是蓝细菌组成的层状藻类体,其次结构藻类体较发育(以硅藻和葡萄球藻为主,底栖宏观藻类在部分样品中较多),高等植物主要包括碎屑镜质体、碎屑壳质体、孢子体等.生烃模拟实验结果显示,含较多底栖藻类的HD-20号样品在400 ℃(Ro=1.02%)时生烃量达到最大值(427 mg/g);而以浮游藻类为主的HD-21号样品,在425℃时(Ro=1.18%)达到最大生烃量(909 mg/g).虽然HD-20号样品具有很高的有机碳含量(39.6%),但其生烃量较浮游藻类为主的HD-21号样品(有机碳含量29.8 %)差,指示底栖藻类具有较低的生烃潜力特征.