Black shale formation environment and its control on shale oil enrichment in Triassic Chang 7 Member, Ordos Basin, NW China

Zhang, Bin; Mao, Zhiguo; ZHANG, Zhongyi; Yuan, Yilin; CHEN, Xiaoliang; Shi, Yuxin; LIU, Guanglin; Shao, Xiaozhou

doi:10.1016/s1876-3804(21)60288-4

Cited by 27 publications

(15 citation statements)

References 24 publications

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“…Similar results have been reported for other places [76]. In this study, shales containing a high proportion of terrigenous organic matter may be more favorable for the formation of light oil than those containing aquatic organic matter [23,77]. Thus, there is strong shale oil exploration potential in the Chang 7 3 sub-member and its adjacent horizons in the Ordos Basin.…”

Section: Geofluidssupporting

confidence: 88%

“…The Chang 7 member was principally deposited in a semideep-deep lake environment and can be subdivided into three sub-members: Chang 7 3 , Chang 7 2 , and Chang 7 1 , from the bottom to the top. The Chang 7 3 sub-member was deposited in the maximum stage of lake basin evolution, and then the lake basin began to shrink and decrease during the Chang 7 2 period until the center of the lake basin retreated to the Jiyuan, Huachi, and Fuxian areas at the end of the Chang 7 1 interval [23].…”

Section: Geological Backgroundmentioning

confidence: 99%

“…Thus, the area was affected by the surrounding terrigenous input, resulting in regionally specific organic matter abundance and type. For example, the higher C 19 TT/C 23 TT and C 24 TeT/C 26 TT ratios of biomarkers in the adjacent well Feng75 in the Tianhuan Depression suggest that the abundance of terrigenous organic matter in the Chang 7 3 sub-member is significantly higher than that in the Chang 7 1 and Chang 7 2 submembers [23]. In the well DP1 area, more terrigenous detrital components were also observed in the thin section of the Chang 7 3 sub-member, which indicates that the study area might have been subjected to a relatively strong input of terrigenous organic matter.…”

Section: Geofluidsmentioning

confidence: 99%

“…However, since the Mahuangshan area is located at the margin of the provenance region, it might have been impacted by the transient delta front detrital input, thus appearing as an oxic-suboxic environment in partial layers. For instance, during the Chang 7 3 interval, the redox state of the bottom water near the study area (wells Y56 and Feng75) was weakly oxic-suboxic, rather than strongly anoxic [16,23,30,51]. In contrast, the southeast and southwest regions of the lake basin usually presented a redox state of strong reduction or even euxinic, indicating that the lake water was stratified [52][53][54][55].…”

Section: Geofluidsmentioning

confidence: 99%

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Extremely High Primary Productivity and Organic Matter Enrichment in Lacustrine Sediments: Late Triassic Chang 73 Sub-Member, Western Ordos Basin

Liao

Chen

et al. 2022

Geofluids

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The 7th member of the Late Triassic Yanchang Formation is the most important Mesozoic source rocks and shale oil reservoir in the Ordos Basin. The hydrocarbon potential and organic matter enrichment mechanism of this organic-rich member are questioned because of the high heterogeneity of continental sediments. In particular, the lack of drilling in the Chang 73 sub-member of the western Ordos Basin (central Tianhuan Depression) hinders this understanding and the progress of shale oil exploration in this region. In this study, 87 samples were collected from the well DP1 in the Tianhuan Depression, western Ordos Basin, and analyzed for sedimentology and geochemistry to unravel the paleoenvironment, paleo-productivity, and hydrocarbon potential of the Chang 73 sub-member. The results show that the Chang 73 shale is characterized by ultra-high organic matter abundance (up to 10.60%), type II kerogen, and good hydrocarbon generation potential. An intermediate chemical weathering intensity suggests that this set of organic-rich shale was deposited in a warm and humid paleoclimate setting. Extreme organic matter enrichment in study area may be attributed to ultra-high productivity (hypereutrophic lake), superimposed terrigenous organic matter input, and transgression, rather than volcanism and anoxic bottom water. This model is different from those of Chang 73 interval with higher organic matter content in the central and southern parts of the Ordos Basin. Therefore, this study proposes that the Chang 73 shale in the central Tianhuan Depression is not a good target layer for shale oil exploration and that the favorable area may be located in an undisturbed deep lake with higher organic matter abundance (e.g., southwestern Ordos Basin).

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Section: Geofluidssupporting

confidence: 88%

Section: Geological Backgroundmentioning

confidence: 99%

Section: Geofluidsmentioning

confidence: 99%

Section: Geofluidsmentioning

confidence: 99%

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Extremely High Primary Productivity and Organic Matter Enrichment in Lacustrine Sediments: Late Triassic Chang 73 Sub-Member, Western Ordos Basin

Liao

Chen

et al. 2022

Geofluids

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“… , During the depositional period of the Yanchang Formation in the Late Triassic, a large inland freshwater lake basin with a wide water area formed in the basin. The basin reached its peak in the Chang 7 Member of the Yanchang Formation, forming the main source rock of the basin. , The Chang 7 Member of the Yanchang Formation is dominated by dark mudstone and shale . Shale mainly develops at the bottom of the Chang 7 Member of the Yanchang Formation and distributes in the NW-SE direction with 20–60 m thick.…”

Section: Geological Settingmentioning

confidence: 99%

Comparison of Geochemical Characteristics of Products from Thermal Simulation Experiments of Hydrocarbon Generation at Different Heating Rates in the Semiclosed System

Han

Lin

et al. 2023

ACS Earth Space Chem.

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Based on the thermal simulation experiment in a semiclosed system, the products of continental type II of the Chang 7 shale under slow and fast heating rates were studied. The results show that the yield of hydrocarbon gases (C 1 −C 5 ) increases under the fast heating rate. Under the slow heating rate, the heavy hydrocarbon gas (C 2 −C 5 ) begins to crack when the temperature exceeds 400 °C. The H 2 S and H 2 have similar variation rules with hydrocarbon gases. Under the slow heating rate, the expelled oil is larger than that of the fast heating rate. C 15+ constitutes the main component of retained oil, and the yield of retained oil at the fast heating rate is larger than that of the slow heating rate, which is different from the expelled oil. After 380 °C, the slow heating rate leads to the cracking of C 15+ , so the amount of C 15+ generated by the fast heating rate is larger than that of the slow heating rate. After 340 °C, the proportion of expelled oil to total expelled hydrocarbons at a slow heating rate is larger than that of the fast heating rate. This study confirms that the fast heating rate can lead to a retardation effect, making the slow heating rate more favorable for the generation and discharge of hydrocarbons. The experimental results verify the compensation effect of time on temperature in the process of hydrocarbon generation.

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The Geochemical Characteristics and Oil Source Correlation of Chang 8 Crude Oil in Huanxi Area, Ordos Basin

Luo,

Ma,

et al. 2024

Springer Series in Geomechanics and Geoengineering

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Black shale formation environment and its control on shale oil enrichment in Triassic Chang 7 Member, Ordos Basin, NW China

Cited by 27 publications

References 24 publications

Extremely High Primary Productivity and Organic Matter Enrichment in Lacustrine Sediments: Late Triassic Chang 73 Sub-Member, Western Ordos Basin

Extremely High Primary Productivity and Organic Matter Enrichment in Lacustrine Sediments: Late Triassic Chang 73 Sub-Member, Western Ordos Basin

Comparison of Geochemical Characteristics of Products from Thermal Simulation Experiments of Hydrocarbon Generation at Different Heating Rates in the Semiclosed System

The Geochemical Characteristics and Oil Source Correlation of Chang 8 Crude Oil in Huanxi Area, Ordos Basin

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