气候变化领域集成服务门户(CCPortal): Oil retention and intrasource migration in the organic-rich lacustrine Chang 7 shale of the Upper Triassic Yanchang Formation; Ordos Basin; central China

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DOI	10.1306/01301917052
	Oil retention and intrasource migration in the organic-rich lacustrine Chang 7 shale of the Upper Triassic Yanchang Formation; Ordos Basin; central China
	Zou C.; Pan S.; Horsfield B.; Yang Z.; Hao S.; Liu E.; Zhang L.
发表日期	2019
ISSN	0149-1423
起始页码	2627
结束页码	2663
卷号	103 期号:11
英文摘要	The Zhang 22 well was drilled in the Ordos Basin, penetrating the Chang 7 Member of the Triassic Yanchang Formation, which, cumulatively, has more than 80m(>260 ft) of black organic-rich shale of oil window maturity. Using 76 samples collected every 1 m (3 ft) from the well, the effects of stratigraphic fractionation and petroleum expulsion within five intervals of the Chang 7 shale were qualitatively and quantitatively documented. The organic-rich intervals 1, 2, and 5, having an average total organic carbon (TOC) of 6.79 wt. % and pyrolyzable hydrocarbon potential of 9.40 mg/g rock (i.e., the amount of hydrocarbons generated by pyrolysis between 300°C and 650°C [S2]), are defined as "generative units"in the Chang 7 shale system, compared to the "in-source reservoirs"or "sweet spots"(i.e., the third and fourth intervals), which contain a lower average TOC of 4.19 wt. % and an average S2 value of 7.17 mg/g rock, but the highest amount of free oil (average total oil of 7.35 mg/g rock). Geochemical and molecular compositions display distinctive differences between samples from these source and reservoir groupings. For example, bitumens from the generative units proportionally possess lower saturated hydrocarbons (56%-66%) than those from the insource reservoirs (up to 81%). The proportions of aromatic and polar compounds in the generative units are accordingly higher than in their counterpart. The individual molecular weight distribution of sample extracts displays more light-end moieties being enriched in the generative units. By applying the compositional mass balance calculation, the overall and compoundspecific expulsion efficiencies in the in-source reservoirs are abnormally negative compared to the positive values in the generative intervals. This finding, in conjunction with the effects of the preferential retention of aliphatic hydrocarbons and the differential expulsion of light molecular weight compounds in the in-source reservoirs, indicates a short-distance intrasource migration of generated petroleum into the sweet-spot intervals (intervals 3 and 4) from the overlying units (intervals 1 and 2) and the underlying interval 5. Furthermore, when quantifying the total amount of retained petroleum in the shale system, an amended assessment has been introduced to overcome the systematic misestimations if only unextracted values for the amount of thermally extractable hydrocarbons volatilized at 300°C (mg HC/g rock) were considered. Thus, the oil crossover effect, temperature at which the rate of S2 generation is at maximum shift phenomenon, and the hydrogen index being shifted to higher values after extraction all account for identifying intervals 3 and 4 as the in-source reservoirs. In this study, we have not only identified a set of promising insource targets for shale oil exploration and production, but we also presented the chemical and molecular composition for these shale oils.We have additionally speculated for the intrasource migration model and further discussed the different expulsion efficiencies in the shale system upon the compositional mass balance calculation as well as the stratigraphic fractionation on differentiating the chemical compositions during migration. The improved oil quality by fractionation, the extra storage potential derived from microfossil quartz, the weak adsorptive affinity of oil to organic matter, and the good shale susceptibility to hydraulic fracturing all give a promising prospective for exploring and producing shale oil from the Chang 7 shale system in the Ordos Basin. © 2020 The American Association of Petroleum Geologists/Division of Environmental Geosciences
语种	英语
scopus关键词	Aliphatic hydrocarbons; Efficiency; Gasoline; Metamorphic rocks; Molecular weight distribution; Oil well drilling; Organic carbon; Shale oil; Stratigraphy; Chemical compositions; Hydrocarbon potential; Mass-balance calculations; Molecular compositions; Organic-rich shales; Saturated hydrocarbons; Total Organic Carbon; Yanchang Formation; Petroleum prospecting; carbon storage; chemical composition; extraction method; fractionation; hydraulic fracturing; hydrocarbon migration; hydrocarbon reservoir; hydrogen; lacustrine deposit; mass balance; microfossil; organic matter; quartz; shale; China; Ordos Basin
来源期刊	AAPG Bulletin
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/143757
作者单位	Research Institute of Petroleum Exploration and Development (RIPED), PetroChina, Beijing, China; Section 3.2 Organic Geochemistry, GFZ Telegrafenberg, Potsdam, Germany; College of Marine Science and Technology, China University of Geosciences, Wuhan, China
推荐引用方式 GB/T 7714	Zou C.,Pan S.,Horsfield B.,et al. Oil retention and intrasource migration in the organic-rich lacustrine Chang 7 shale of the Upper Triassic Yanchang Formation; Ordos Basin; central China[J],2019,103(11).
APA	Zou C..,Pan S..,Horsfield B..,Yang Z..,Hao S..,...&Zhang L..(2019).Oil retention and intrasource migration in the organic-rich lacustrine Chang 7 shale of the Upper Triassic Yanchang Formation; Ordos Basin; central China.AAPG Bulletin,103(11).
MLA	Zou C.,et al."Oil retention and intrasource migration in the organic-rich lacustrine Chang 7 shale of the Upper Triassic Yanchang Formation; Ordos Basin; central China".AAPG Bulletin 103.11(2019).