Influencing factor of Chang 7 oil shale of Triassic Yanchang Formation in Ordos Basin: Constraint from hydrothermal fluid

You, Jiyuan; Liu, Yiqun; Li, Yijun; Zhou, Dingwu; Zheng, Qi; Yong-ming, Yang; Jian, Shi; Gao, Haofeng

doi:10.1016/j.petrol.2021.108532

Cited by 17 publications

(3 citation statements)

References 23 publications

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“…The corresponding TOC content is as high as 40%. You et al’s (2021) research also show that the greater the hydrothermal input intensity is, the greater the TOC content of the oil shale is. In the lower portion of the first organic matter enrichment layer, Al/(Al + Fe + Mn) = 0.41; however, based on other conditions, we speculated that there may be hot water activity in this area.…”

Section: Discussionmentioning

confidence: 69%

Organic matter heterogeneity and shale oil significance in Triassic Zhangjiatan shale, Ordos Basin, China

Tuo

et al. 2021

Energy Exploration & Exploitation

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Organic matter heterogeneity exerts an important impact on the generation, evaluation, and exploitation of shale oil resources. In the past, only a limited number of analytical samples that represented the contribution or influence of high or low organic matter abundance intervals were used to represent an entire set of thick source rocks, and based on this limitation, occasionally researchers have reached incorrect conclusions. Here, the heterogeneity of organic matter and its significance to shale oil in the Triassic Zhangjiatan shale of the Ordos Basin were discussed based on sedimentary and geochemical analyses. Our results indicate that (1) the Chang 73 shale within the study area is characterized by high abundance, good quality, strong heterogeneity, and segmented enrichment in the vertical profile. The primary organic matter type was type II1, and this was followed by types I, II2, and III that exhibited three changing trends in the vertical profile. Organic matter maturity is primarily at the immature stage. (2) Additionally, we observed that the organic matter heterogeneity of Chang 73 shale was related to changes in lithology, sedimentary environment, paleoproductivity, terrigenous influence, and event action (such as volcanism and hydrothermal processes). The abundance of organic matter is the result of the coupling control of these processes. In the process of organic matter deposition, if volcano or hydrothermal activities occurred, the organic matter was abnormally enriched, and the total organic carbon content exceeded 20% and could even be as high as 40%. (3) Finally, we observed at least nine enrichment layers that were controlled by the coupling of different geological factors, and there were four potential target resource layers corresponding to the hydrothermal sedimentary area.

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Section: Discussionmentioning

confidence: 69%

Organic matter heterogeneity and shale oil significance in Triassic Zhangjiatan shale, Ordos Basin, China

Tuo

et al. 2021

Energy Exploration & Exploitation

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“…The Upper Triassic Yanchang Formation is divided into 10 oil layers from bottom to top, which are called Chang 10 to Chang 1. The lake basin had the largest area during the Chang 7 period after experiencing the process of water inflow and outflow during lake basin expansion [34,35], shrinkage and disappearance, and the lake basin in the Chang 6 period was in the shrinking stage [36] (Figure 1c). Gravity flow deposits were mainly developed in the study area [37], and the scale of sand body deposits is large, forming favourable reservoirs.…”

Section: Geological Settingmentioning

confidence: 99%

Research on Fractal Characteristics and Influencing Factors of Pore-Throats in Tight Sandstone Reservoirs: A Case Study of Chang 6 of the Upper Triassic Yanchang Formation in Huaqing Area, Ordos Basin, China

Nan,

Lin,

Lai

et al. 2023

Minerals

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In recent years, tight sandstone oil and gas have been an important area for unconventional oil and gas exploration and development in China. It is of great significance to clarify the pore-throat structure characteristics of tight sandstone reservoirs to guide production practices. This study takes the tight sandstone of the sixth member of the Yanchang Formation in the Huaqing area, Ordos Basin, as an example, based on experimental methods such as high-pressure mercury intrusion, cast thin sections and scanning electron microscopy. At the same time, the pore-throat structure of tight sandstone reservoirs is divided into three types using the tube-bundle and spherical fractal models. The corresponding pore and throat radius distribution, pore-throat combination mode and influencing factors of various pore-throats are studied. The results show that the fractal dimension of type I pore-throats is the smallest, and the distribution of their pore-throat radii is the most uniform. They are dominated by intercrystalline pores and dissolution pores with tube-bundle throats and small pores with small throats. Type II pore-throats have the largest fractal dimension and the worst pore-throat uniformity. They are dominated by residual primary intergranular pores with necked throats and large pores with small throats. The type III pore-throat fractal dimension is in the middle, mainly composed of residual dissolved intergranular pores with pore-reduced throats, sheet-like and curved sheet-like throats, and large pores with large throats. The influence of different pore-throat combinations on the reservoir is reflected in the different characteristics of mercury injection parameters. The main influencing factors for the differences in the fractal dimensions of different pore-throats are diagenesis, rock composition and pore-throat combination type. Diagenesis and rock composition, in turn, affect the type and development degree of pore-throats, as well as the combination of pore-throats. The purpose of this study was to clarify the internal connection modes of different homogeneous pore-throats and their influencing factors, enrich the theoretical basis for the study of tight sandstone reservoirs and provide theoretical guidance for their exploration and development.

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“…In addition, China has great potential for shale oil resources, with recoverable resources reaching 131.8 × 10 8 t [7]. For example, the Chang 7 shale oil in the Ordos Basin [8], middle Permian Lucaogou Formation shale oil in the Junggar Basin [9] and Eocene Kong 2 member shale oil in the Bohai Bay Basin are all major areas of production [10], but the shale oils mentioned above are hybrid or interlayer shale oils. The Gulong shale in the Songliao Basin is a pure oil reservoir, which shows the development of laminar structures and foliation fractures in this study area.…”

Section: Introductionmentioning

confidence: 99%

Pore Characteristics, Oil Contents and Factors Influencing Laminated Shale in the First Member of the Qingshankou Formation in the Gulong Sag, Northern Songliao Basin

Zhang,

Pan,

Bai

et al. 2023

Minerals

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To clarify the reservoir characteristics of laminated shale, the occurrence mechanism of shale oil and its influencing factors in the Gulong Sag, northern Songliao Basin, are studied to better guide the exploration and development of shale oil there. First, X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) are used to characterize the pore types, pore geneses and factors influencing the pore volume in the study area. Second, the organic matter of the samples is extracted with a mixture of dichloromethane and methanol. Total organic carbon (TOC), nitrogen adsorption and Rock-Eval tests are performed on the samples before and after extraction to reveal the pore size distribution after extraction. The factors influencing free and adsorbed shale oil and the lower limit of pore size are discussed in detail. The results show that interparticle pores (interP pores), intraparticle pores (intraP pores), organic matter pores (OM pores) and microfractures can be found in the laminated shale (Q1) in the Gulong Sag, Songliao Basin, and that the interP pores and intercrystalline pores in clay minerals are the main pores. The FE-SEM results show that the diameters of interP pores vary from several hundred nanometers to several microns, and their morphologies are mainly triangular, strip-shaped or irregular. The morphology of the intercrystalline pores in the clay minerals is generally irregular, depending on the crystal type and arrangement of clay minerals. According to the characteristics of the nitrogen adsorption and desorption curves, the pore morphologies are mainly slit-shaped pores, parallel-plate-shaped pores and ink-bottle-shaped pores. The pore size distribution is mostly bimodal, and the pore volume contribution is the greatest in the pore size range of 10~20 nm. Before and after extraction, the overall characteristics of the pore size distribution change only slightly, but the number of micropores increases significantly. Different minerals have different degrees of influence on the proportions of micropores, mesopores and macropores. Quartz mainly inhibits the formation of micropores, while the overall effect on mesopores and macropores is positive depending on the diagenetic period. Feldspar has a strong positive correlation with the micropore and mesopore proportions but is not highly correlated with the macropore proportions. The influence of the carbonate mineral content on the pore volume is not obvious because of its complex composition. The TOC content and vitrinite reflectance (Ro) are the two most important factors controlling free oil and adsorbed oil, and the contents of mineral components, such as felsic minerals, carbonate minerals and clay minerals, have no obvious correlation with shale oil content. With increasing pore volume, the contents of free oil and adsorbed oil increase, but the proportion of adsorbed oil decreases gradually. The correlation between the specific surface area and adsorbed oil content is poor. At normal temperatures and pressures, the lower limit of the pore diameters that can contain free oil is 4 nm, and the lower limit of the pore diameters that can contain movable oil is 10 nm.

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Influencing factor of Chang 7 oil shale of Triassic Yanchang Formation in Ordos Basin: Constraint from hydrothermal fluid

Cited by 17 publications

References 23 publications

Organic matter heterogeneity and shale oil significance in Triassic Zhangjiatan shale, Ordos Basin, China

Organic matter heterogeneity and shale oil significance in Triassic Zhangjiatan shale, Ordos Basin, China

Research on Fractal Characteristics and Influencing Factors of Pore-Throats in Tight Sandstone Reservoirs: A Case Study of Chang 6 of the Upper Triassic Yanchang Formation in Huaqing Area, Ordos Basin, China

Pore Characteristics, Oil Contents and Factors Influencing Laminated Shale in the First Member of the Qingshankou Formation in the Gulong Sag, Northern Songliao Basin

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