吉木萨尔凹陷芦草沟组页岩油生烃母质及其生烃机理

doi:10.7657/XJPG20240301

摘要/Abstract

摘要：

为明确吉木萨尔凹陷芦草沟组上、下甜点段页岩油生烃母质差异和生烃机理，采用场发射扫描电镜、电子探针和傅里叶红外光谱实验，对芦草沟组烃源岩超微生物特征进行研究。上甜点段页岩油主要生烃生物为层状藻（微囊藻），母质以直链脂肪族为主；下甜点段以结构藻（塔斯马尼亚藻）为主，生烃母质富集富支链脂肪族、芳香族和亚砜官能团。由于长直链饱和烃断裂所需的活化能远高于分支链及碳硫和碳氮低键能，因此，下甜点段页岩油的生烃母质活化能低于上甜点段，发生早期生烃，在低成熟度下形成高非烃沥青质的高密度原油，是下甜点段原油性质偏重偏稠的主要原因。

关键词: 准噶尔盆地, 吉木萨尔凹陷, 芦草沟组, 页岩油, 藻类, 生物标志化合物, 活化能, 生烃机理

Abstract:

In order to clarify the differences in hydrocarbon-generating precursor and mechanism of the shale oil between the upper and lower sweet spots of the Lucaogou formation, the source rocks of the Lucaogou formation in the Jimsar sag were characterized ultra-microbiologically using field emission scanning electron microscopy, electron probe, and Fourier transform infrared spectroscopy experiments. The results show that the main hydrocarbon-generating precursor of the shale oil in the upper sweet spot is lamalginite (Microcystis), with straight-chain aliphatic series in dominance, and the main hydrocarbon-generating precursor in the lower sweet spot is telalginite (Tasmanian algae), which is rich in branched-chain aliphatic, aromatic, and sulfoxide functional groups. Due to the significantly higher activation energy required for the cleavage of long straight-chain saturated hydrocarbons than that for branched-chain hydrocarbons, as well as the lower bond energies of carbon-sulfur and carbon-nitrogen bonds, the activation energy of the precursor of the shale oil in the lower sweet spot is lower than that in the upper sweet spot. Consequently, early-stage hydrocarbon generation occurs, leading to the formation of high-density crude oil rich in non-hydrocarbon bitumen at low maturity, which is the primary reason for the relatively heavy and viscous nature of the crude oil in the lower sweet spot.

Key words: Junggar basin, Jimsar sag, Lucaogou formation, shale oil, algae, biomarker, activation energy, hydrocarbon generation mechanism

中图分类号:

TE122.11

王剑, 刘金, 潘晓慧, 张宝真, 李二庭, 周新艳. 吉木萨尔凹陷芦草沟组页岩油生烃母质及其生烃机理[J]. 新疆石油地质, 2024, 45(3): 253-261.

WANG Jian, LIU Jin, PAN Xiaohui, ZHANG Baozhen, LI Erting, ZHOU Xinyan. Precursor and Mechanism of Hydrocarbon Generation for Shale Oil in Lucaogou Formation, Jimsar Sag[J]. Xinjiang Petroleum Geology, 2024, 45(3): 253-261.

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井名	深度/m	显微组分	总有机碳含量/%	镜质体反射率/%	热解峰温/ ℃	游离烃含量/ （mg·g^-1）	热解烃含量/ （mg·g^-1）	生烃指数/ （mg·g^-1）
J10025井	3 506.8	结构藻	1.80	0.87	440	0.59	6.62	366
J10025井	3 530.8	层状藻	14.90	0.56	444	1.52	103.29	692
J10025井	3 569.2	层状藻	3.10	0.65	443	0.41	18.34	592
J10025井	3 576.6	层状藻	17.00	0.55	449	1.79	117.24	691
J10025井	3 624.3	层状藻	3.60	0.50	443	1.02	26.42	713
J10025井	3 679.5	结构藻	3.10	0.72	435	1.07	8.59	276
J10025井	3 696.9	结构藻	2.50	0.60	433	0.70	6.21	248
J10025井	3 708.3	结构藻	4.40	0.52	437	0.70	26.00	598

井名	深度/ m	生烃母质类型	生烃活化能/ （kJ·mol^-1）	主体活化能/ （kJ·mol^-1）	频率/ %
J10024井	3 510.3	层状藻	58~70	58	99.70
J10025井	3 530.8	层状藻	65	65	100
J10025井	3 576.6	层状藻	63~68	63	99.07
J10025井	3 624.3	层状藻	64~69	64	99.56
J10025井	3 547.8	结构藻	39~71	59	86.30
J10025井	3 679.5	结构藻	32~60	49	49.28
J10025井	3 696.9	结构藻	32~59	49	61.32
J10025井	3 708.3	结构藻	34~63	52	74.34