The Exquisite Comparison of Shale Mineralogical-Geochemical Characteristics between Chang 7 Member and Chang 9 Member in Yanchang Formation, Ordos Basin

Zhang, Wang; Liang, Xinping; Li, Peng; Liu, Guoheng

doi:https://doi.org/10.1155/2023/5039604

Geofluids

On this page

Abstract Introduction Results Discussion Conclusion Data Availability Conflicts of Interest Acknowledgments References Copyright Related Articles

Special Issue

New Challenges and Advances in the Unconventional Oil/Gas Reservoirs Characterization and Development

View this Special Issue

Research Article | Open Access

Volume 2023 | Article ID 5039604 | https://doi.org/10.1155/2023/5039604

The Exquisite Comparison of Shale Mineralogical-Geochemical Characteristics between Chang 7 Member and Chang 9 Member in Yanchang Formation, Ordos Basin

Wang Zhang,¹Xinping Liang,²Peng Li,³and Guoheng Liu⁴

Academic Editor: Jin Qian

Received10 Oct 2022

Revised27 Mar 2023

Accepted25 Jul 2023

Published16 Aug 2023

Abstract

Significant amounts of unconventional oil and gas resources have been discovered in the Yanchang Formation of Ordos Basin. Shale layers deposited in Chang 7 member (divided into Chang 7-2 submember (C7-2SM) and Chang 7-3 submember (C7-3SM) and Chang 9 member (C9M)) are the main source rocks. Based on the comparison of mineralogical and geochemical characteristics, it is concluded that (1) in terms of mineralogical characteristics, the C7-3SM shale possesses the largest content of illite/smectite mixed layer and reducing minerals and the least quantity of quartz. The C9M shale shows the highest percentage of quartz and illite and the least amount of K-feldspar and Kaolinite. In C7-2SM and C9M shale, amorphous silica surrounded tightly by clay minerals is easily observed by the scanning electron microscopy. Besides the drilling orientation, the small content of quartz contributed to the lowest porosity for the C7-3SM shale. (2) In terms of geochemical characteristics, the C7-3SM shale exhibits high productivity due to type II₁ kerogen. The organic matter in the C7-2SM and C9M shale contains mainly type II₂ and possibly type III kerogen. The C9M shale exhibits the highest organic thermal maturity. The C7-3SM shale was formed in a relatively higher salinity of sedimentary water.

1. Introduction

Successful exploration of shale gas in previous years has aroused wide public concern about the shale reservoir [1–4]. In recent years, the lacustrine shale gas exploration also succeeded in the Permian Lucaogou Formation of Junggar Basin, the Mesozoic Yanchang Formation of Ordos Basin and the Upper Cretaceous Qingshankou Formation of Songliao Basin. Along with these exploration practices, a lot of research findings have been produced [5–8]. The lacustrine shale is different from marine shale in many aspects, including the structural and depositional setting, pore and fracture networks, geochemical and reservoir characteristics, shale gas genetic types, and accumulation model [9–12].

Globally, only 1.2% of Phanerozoic source rocks are Triassic in origin. However, the Triassic Yanchang Formation of the Ordos Basin having the large abundant shale oil resources in China [13, 14]. Shale layers, the most important source rock in the Ordos Basin, are primarily deposited in Chang 9 and Chang 7 members. In recent years, the Chang 7 member shale has drawn much attention, especially the C7-3SM shale has been regarded as an integrated whole to compared with marine shale [4, 15]. Because in this period, the basin’s area and the water body’s depth reached the peak [16]. However, the C7-2SM and C9Ms shale were neglected. The deposition time of C7-2SM and C7-3SM is similar. Due to changes in the sedimentary environment, they show significant differences in their shale quality. In the C9M sedimentary period, the lake basin development was still in the early stage, which was a semideep lake sedimentary environment [17]. Both Chang 7 and C9Ms shale had similar compositions, with abundant type II organic matter and major minerals such as quartz, clay minerals, and feldspars [15, 18]. They are generally less mature than the marine shale, and the relatively larger amount of clay minerals in Chang 7 and C9M shale affects the methane sorption of bulk rocks under dried conditions [15]. Comprehensively comparative research about different layers of Yanchang Formation shale is much imperative. Based on the previous work [19], the latest research results of Chang 9, systematically comparing C7-2SM, C7-3SM, and Chang 9, were presented in this research.

2. Geological Setting

The Ordos Basin, as one of the most petroliferous and gas-bearing lacustrine basin, is located in the central part of North China [11, 20]. Because of the wrench movement around the basin in the Cenozoic era, the Ordos Basin is now an asymmetric huge north-south syncline with a wide-gentle east limb and a narrow-abrupt west one. The Ordos Basin can be divided into six tectonic units [21, 22], namely, the Northern Yimeng uplift, south Weibei uplift, eastern Jinxi flexural zone, western Xiyuan obduction zone with Tianhuan hollow zone closely next to it, and Yishan ramp region in the center. Yishan ramp region is the main part of the wide-gentle east limb. The research area is located in the southeast of Yishan ramp region and is a western-leaning monocline with lower stratigraphic dip (<1°), gentle average slope (7-8 m/km), and simple internal structure (Figure 1).

The Triassic strata consist of fluvial and lacustrine deposits [23]. The Yanchang Formation was deposited in the late Triassic age and is divided into 10 members from top to bottom according to marker beds and sedimentary cycles. The seismites were widely developed in the whole Yanchang Formation [22], but the shale layers, as the main source rock in the area, were primarily deposited in the Chang 7 and C9Ms (Figure 2). The C9M formed in the early stage of the late Triassic, and the shale layers only occurred in the upper part and mainly consist of lacustrine organic-rich black shale (commonly known as “Lijiatan” shale in China) [24]. The Chang 7 member developed in the period of flooding lake in Ordos Basin. The shale layers, as the main body of Chang 7 member, mostly consist of organic-rich black shale and oil shale (commonly known as “Zhangjiatan” black shale in China) [25].

The Yanchang Formation shale (shale in Chang 9 and Chang 7 members) was deposited in a freshwater lacustrine sedimentary environment, developing obvious organic matter lamina, pyrite framboids, and nanofossils [26, 27]. The Yanchang Formation shale strata is about 80 m thick in average with the thickest area about 100 m, and is now buried in depth ranging from 832 m-1700 m with the average of 1288 m. Lamina mainly develops in Chang 7 member shale indicating stronger anisotropy than C9M shale (Figure 2). Pyrite framboids in C9M shale grow separately rather than gathering to aggregate (Figure 2). Heavy minerals, such as barite and phosphorite, can be observed occasionally both in Chang 7 and C9M shale (Figure 2). The organic-rich shales in the Chang 7 member of the Yanchang Formation are self-generation and self-accumulation production systems with oil in fine-grained sedimentary rocks [28].

The Chang 7 member can be divided into three submembers (SM) according to the sedimentary cycle [25, 29]. The lithology of Chang 7-1 SM mainly consists of sandstone and siltstone, which do not belong to the section of Chang 7 member shale reservoir. The Chang 7 member shale can be divided into C7-2SM and C7-3SM (Figure 2). The two SM shale appears to be similar in the gamma readings, with upper possessing relatively higher gamma value as a result of containing volcanic debris with radioactive substances [30] but display a significant difference in the acoustic time data, with C7-2SM presenting low frustration in AC data and C7-3SM displaying relatively higher and increasing AC values with progressive burial depth.

3. Samples Preparation and Experimental Methods

3.1. Samples Preparation

A series of experiments were conducted, including X-ray diffraction, total organic carbon analysis, rock pyrolysis, and vitrinite reflectance. Shale samples of the C7-2SM, C7-3SM, and C9M cannot be acquired from any individual well so far. The shale sample numbers for each and matching experimental method are presented in detailed in Table 1.

3.2. Experimental Methods

3.2.1. X-Ray Diffraction Analysis and Scanning Electron Microscope Observation

A total of 60 shale samples from Chang 7 and C9M shales were ground to powder finer than 200 mesh (i.e., <75 μm) and then analyzed for whole-bulk and clay fraction (<2 mm) mineralogy by quantitative X-ray diffraction (XRD) analysis by Rigaku automated powder diffractometer (D/MAX-RA) equipped with a Cu X-ray source (40 Kv, 35 mA), following the two independent processes of the CPSC procedure [31]. First, the bulk mineral composition of the powder sample was determined over an angular range of 4-70°2θ at a scanning speed of 1°2θ/min. Second, the clay mineral content was determined over an angular variations of 3-65°2θ at a scanning speed of 1.5°2θ/min after the clay fractions being separated from the rock powder sample. The scanning electron microscope (SEM) observation was also conducted using a Leica microscope with a CRAIC Microscope photometer and FEI Quanta-200F apparatus with an energy-dispersive spectrometer (EDS) in the State Key Laboratory of Petroleum Resources and Prospecting (Beijing) to ascertain image analysis of minerals.

3.2.2. Total Organic Carbon and Rock-Eval Analysis

156 samples were used in TOC and Rock-Eval analysis, using laboratory apparatus LECO TOC (CS-230HC) and the ROCK-EVAL.II methodology, which were conducted in the State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing. The samples used in TOC measurement were immersed in 5% HCl solution for two days in order to eliminate the carbonate minerals and then dried in a stoving oven at 65°C for 1.5 days. Rock-Eval pyrolysis is an established method for characterizing the type and thermal maturity of organic matter in sedimentary rocks as well as their petroleum generation potential [32]. The samples were subjected to programmed heating in an inert atmosphere to determine the amount of volatile gas and residual hydrocarbons (S₁ peak) and the amounts of nonvolatile hydrocarbons and oxygen-containing organic compounds released during thermal cracking of the remaining organic matter in the rock (recorded as S₂).

3.2.3. Vitrinite Reflectance and Trace Element Analysis

The thermal maturity reflected by the experimental vitrinite reflectance values was acquired by full-automatic microscope photometer (MPV-SP). A total of 60 samples were employed for trace element analysis. Samples were crushed into mm-size fragments and washed in 10-percent HCl to leach soluble secondary material (e.g., calcite), followed by agitation in reverse osmosis water prior to powdering. Each sample was heated in 30% H₂O₂ until all organic matter had been digested. The concentration of trace elements in minerals was obtained with laser-ablation microprobe linked with inductively coupled plasma mass spectrometer (LAM–ICP–MS) in the Beijing Research Institute of Uranium Geology, which is the geological experiment research department of the China National Nuclear Corporation (CNNC). Detection limits were typically in the range 100–500 ppb for Sc, 10–100 ppb for Sr, Zr, Ba, Gd, and Pb, 1–10 ppb for Y, Nb, La, Ce, Nd, Sm, Eu, Dy, Er, Yb, Hf, and Ta, and usually 1 ppb for Pr, Th, and U.

3.2.4. Porosity and Permeability Analysis

The cylinder shale samples with a diameter of 2.5 cm and a length of 5 cm for each were analyzed for porosity and permeability in the Reservoir Porous Flow Laboratory of RIPED-Langfang PetroChina. These samples were definitely without factitious microfracture on the surface formed during the drilling process. It is hard to identify artificial microfracture formed in the sample interior before porosity and permeability analysis, which explains aberrant data point appearance.

4. Results

4.1. Mineral Composition and SEM-EDS

There are scarcely any carbonate minerals in both the Chang 7 and C9M shales (Figure 3) compared with the Barnett shale [2, 33]. Illite-smectite mixed layer is the main composition of clay minerals. The C7-2SM exhibits a little bit higher content of clay minerals than the C7-3SM and C9M shale and detrital minerals (Table 2, Figure 4). The C9M shale owns the highest percentage of quartz (36.22%) and illite (26.17%) while possesses the least amount of K-feldspar (1.33%) and kaolinite (0.06%) (Figure 4). The C7-3SM shale possesses much larger content of illite/smectite mixed layer and less quantity of quartz, which exhibits great dissimilarity with C7-2SM and C9M shales. In C7-2SM and C9M shales, some amorphous silica was observed, which cannot be measured by XRD (Table 2). They are surrounded tightly by clay minerals, and there is no space for them to grow into authigenic microquartz (Figure 5).

(a)

(b)

(c)

(d)

4.2. Geochemical Characteristics

4.2.1. Organic Matter Richness

The TOC data points of the C7-2SM and C9M shales are more scattered, mainly ranging from 2% to 12% (Table 3). Most of the TOC values of the C7-2SM shale distribute in the range of 2%~6% and C9M shale in the range of 4%~8%, while that of the C7-3SM shale is chiefly in the variation range of 4%~6%. The C7-3SM shale possesses the highest content of residual bitumen and oil, as indicated by the largest values, which are approximately equal between the C7-2SM and C9M shales (Figure 6(a)). The TOC of both the Chang 7 and Chang 9 shales exhibits good positive correlation with values. But the slope value of the line on behalf of the C7-3SM shale is much higher than the other two sections of shale (Figure 6(b)). According to the principle of laboratory apparatus LECO TOC (CS-230HC) analysis, TOC includes the contribution from kerogen and residual bitumen and oil. The C7-3SM shale possesses the highest content of residual hydrocarbon and kerogen.

(a)

(b)

4.2.2. Organic Matter Maturity

Both the Chang 7 and C9M shales are mainly in the oil window at the present time with ranging from 0.8% to 1.2% (Figure 7, Table 4). standing for hydrocarbon newly generated during the Rock-Eval process has better positive correlation with TOC than representing residual hydrocarbon in shale samples, which indirectly indicates the relatively low thermal maturity. Exquisitely compared with each other, the organic matter in Chang 9 shale exhibits the highest thermal maturity, and that in the C7-3SM shale samples the lowest. The C9M shale is buried about 100 m deeper than the Chang 7 member shale, which makes the highest thermal maturity easily understandable. However, the thermal maturity of C7-3SM shale is lower despite being buried deeper than C7-2SM shale, which implies the existence of other controls on thermal maturity.

4.2.3. Organic Matter Types

According to Rock-Eval data, kerogen in both C7-2SM and C9M shales contains mainly type II₂ and possibly type III, especially for C9M shale (Figure 8). Approximately half of the C7-3SM shale samples show the type II₁ kerogen, but the other half of the samples present the type II₂ kerogen, and the data points are distributed a little far away from the type III threshold line (Figure 8). It can be an explanation of possessing the highest values of and with medium content of TOC and the lowest thermal maturity.

4.3. Trace Element Analysis

Element B is regarded as a common parameter that possesses a positive linear correlation with salinity of sedimentary water [34, 35]. In Yanchang Formation shale, B was not determined at all, indicating a freshwater sedimentary environment. The Sr/Ba is another parameter sensitively reflecting the salinity of sedimentary water. It represents freshwater sedimentary environment when the Sr/Ba value is less than 1 [36, 37], which is exactly describing the Yanchang Formation shale samples (Figure 9). The Sr/Cu is a parameter employed to express the dry-humid degree of sedimentary environment. It represents warm-moist climate when the Sr/Cu values range from 1 to 10 [34, 37], which is exactly describing most of the Yanchang Formation shale samples.

The dry-humid degree of the sedimentary environment has a great influence on the salinity of sedimentary water. The Yanchang Formation shale presents a linear correlation between Sr/Ba and Sr/Cu (Table 5). The slope value of the line on behalf of the C7-3SM shale is much lower than those of the lines representing the C7-2SM shale and C9M shale, which means relatively higher salinity of sedimentary water for the C7-3SM shale (Figure 9).

A large quantity of parameters have been used to reflect the reducibility or oxidability of sedimentary environment, such as Ce/La, Th/U, Cr/V, Cr/Cu, V/Sc, V/(V+Ni), and (Cu+Mo)/Zn [38–41]. All the parameters mentioned above indicate a reduced environment for the Yanchang Formation shale. But only the parameters of Ce/La, (Cu+Mo)/Zn, V/Sc and Cr/Cu satisfy our requirement to exquisite comparison among C7-2SM, C7-3SM and C9M shale (Figure 10). Compared with C7-2SM and C9M shales, the Ce/La, (Cu+Mo)/Zn, and V/Sc values of the C7-3SM shale are much larger and the Cr/Cu values smaller (Figure 11), which represents a stronger reducing environment. It was also indicated indirectly by much larger percentage of reducing minerals, pyrite and siderite, in Figure 4.

(a)

(b)

(c)

(d)

4.4. Porosity and Permeability

The Chang 9 member shale possesses the highest porosity followed by the Chang 7-2 SM shale. Although two samples from the Chang 7-3 SM shale display higher permeability, in general, no apparent difference of permeability occurs among the three sections of shale (Table 6).

5. Discussion

Sedimentation and diagenesis are the main controlling factors for the differences among the three members and also lead to the enrichment of organic matter and the potential of oil and gas resources. According to the trace element analysis, the C7-3SM shale developed under much deeper and stratified water. The relatively larger amount of reducing minerals in C7-3SM shale, pyrite and siderite, implies a different sedimentary environment from the C7-2SM and C9M shales. Furthermore, much deeper water represents further away from the sediment provenance, which explains the much larger content of illite/smectite mixed layer and less quantity of quartz.

The C9M shale is buried deeper than Chang 7 member shale and has experienced stronger diagenesis, which explains the nearly disappearance of kaolinite. In addition, more K-feldspar was dissolved for the C9M shale during the burial diagenesis to provide K⁺ for smectite-illite transformation, reducing the most amount of illite and the least content of K-feldspar. The smectite to illite reaction is a dissolution–precipitation reaction [42, 43]. This reaction releases locally high silica supersaturation in the pore water, which probably provides silica source for the authigenic microquartz crystals [44, 45]. According to the experiment [46], about 18% of the silica (1101.1 g of the products produced by the reaction, including 197.7 g of silica) will be released during the conversion of montmorillonite to illite. The chemical reaction formula adopted is as follows:

It was another contribution to the larger content of quartz in C9M shale.

In fact, the drilling orientation was the major factor to porosity and permeability. Samples with drilling orientation perpendicular to sedimentary stratification (“vertical” samples) display relatively lower porosity and permeability than samples with drilling orientation parallel to sedimentary stratification (“parallel” samples) because of the existence of lamina, which improves porosity and permeability in the research about the Yanchang Formation shale of Ordos Basin. Regardless of the degree of compaction and diagenesis, the laminar zone, where different mineral zones come into contact with each other, is always the weakest zone in the sample and has gaps that are difficult to close. “Vertical” samples are lack of lamina. Alternatively, the striations developed in the sample are perpendicular to the flow direction of the gas used in the permeability test. In permeability tests, gas is more likely to pass through the gap between the two different laminates. If the laminar is perpendicular to the direction of gas flow, it is equivalent to gas from one medium into another medium, and the flow velocity must be reduced. Lamina is the main contribution to bedding fissure development, which is the key factor to induce cylinder shale samples fragmentation when being drilled perpendicularly to sedimentary stratification.

Besides, porosity displays a positive correlation with the content of quartz, no matter for “vertical” samples or “parallel” samples (Figure 12). Compaction of soft muds to hard shale during progressive burial involves both mechanical and chemical processes causing significant changes of the physical mudstone rock properties. In the shallow parts (<2 km) of sedimentary basins, the sediments compacted mostly mechanically. The Yanchang Formation shale strata is buried in depth ranging from 2730 ft to 5577 ft (832 m-1700 m) with an average of 4225.7 ft (about 1288 m), which means mechanical compaction dominates the changes of shale physical properties. Hence, the special mineral composition of the Chang 7-3 SM, a small percentage of quartz and large quantity of illite/smectite mixed layer, exactly explains the lowest porosity.

6. Conclusion

Based on mineralogical and geochemical characteristics, this work compared C7-2SM, C7-3SM, and Chang 9 shales: (1)All three section of shales developed in a freshwater sedimentary environment. But the C7-3SM shale samples formed in deeper sedimentary water of relatively higher salinity and stronger reducibility, inducing the largest content of illite/smectite mixed layer and the least quantity of quartz. The C7-2SM and C9M shale formed in similar sedimentary environment according to the trace element characteristic and mineral composition in view of mineral evolution during diagenesis(2)The C7-3SM shale owns higher values and productivity of hydrocarbon per gram TOC due to type II₁ kerogen. Kerogen in C7-2SM and C9M shale contain mainly type II₂ and possibly type III, organic matter, especially for C9M shale(3)The C7-3SM shale samples display the lowest porosity. The drilling orientation and the small content of quartz contributed to the lowest porosity for the C7-3SM shale

Data Availability

The data used to support the findings of this study are included within the article and available from the corresponding author upon request.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

This work was performed under financial support of the State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development (Grant No. 33550000-22-ZC0613-0006).

References

J. B. Curtis, “Fractured shale-gas systems,” AAPG Bulletin, vol. 86, no. 11, pp. 1921–1938, 2002.
View at: Publisher Site | Google Scholar
D. M. Jarvie, R. J. Hill, T. E. Ruble, and R. M. Pollastro, “Unconventional shale-gas systems: the Mississippian Barnett shale of north-Central Texas as one model for thermogenic shale-gas assessment,” AAPG Bulletin, vol. 91, no. 4, pp. 475–499, 2007.
View at: Publisher Site | Google Scholar
G. Liu, B. Liu, K. Liu, G. Zhai, and Z. Guo, “Silica crystallinity: characteristics and controlling factors in marine shale of the upper Yangtze area, China,” Marine and Petroleum Geology, vol. 143, article 105833, 2022.
View at: Publisher Site | Google Scholar
G. Liu, G. Zhai, R. Yang, T. He, and B. Wei, “Quartz crystallinity index: new quantitative evidence for biogenic silica of the late Ordovician to early Silurian organic-rich shale in the Sichuan Basin and adjacent areas, China,” Science China Earth Sciences, vol. 64, no. 5, pp. 773–787, 2021.
View at: Publisher Site | Google Scholar
S. Han, J. Zhang, Y. Li et al., “Evaluation of lower Cambrian shale in northern Guizhou Province, South China: implications for shale gas potential,” Energy & Fuels, vol. 27, no. 6, pp. 2933–2941, 2013.
View at: Publisher Site | Google Scholar
T. Hu, X. Pang, F. Jiang et al., “Movable oil content evaluation of lacustrine organic-rich shales: methods and a novel quantitative evaluation model,” Earth-Science Reviews, vol. 214, article 103545, 2021.
View at: Publisher Site | Google Scholar
T. Hu, X. Pang, F. Jiang et al., “Dynamic continuous hydrocarbon accumulation (DCHA): existing theories and a new unified accumulation model,” Earth-Science Reviews, vol. 232, article 104109, 2022.
View at: Publisher Site | Google Scholar
G. Liu, B. Liu, Z. Huang et al., “Hydrocarbon distribution pattern and logging identification in lacustrine fine-grained sedimentary rocks of the Permian Lucaogou formation from the Santanghu basin,” Fuel, vol. 222, pp. 207–231, 2018.
View at: Publisher Site | Google Scholar
R. G. Loucks, R. M. Reed, S. C. Ruppel, and D. M. Jarvie, “Morphology, genesis, and distribution of nanometer-scale pores in siliceous mudstones of the Mississippian Barnett shale,” Journal of Sedimentary Research, vol. 79, no. 12, pp. 848–861, 2009.
View at: Publisher Site | Google Scholar
J. F. W. Gale, R. M. Reed, and J. Holder, “Natural fractures in the Barnett shale and their importance for hydraulic fracture treatments,” AAPG Bulletin, vol. 91, no. 4, pp. 603–622, 2007.
View at: Publisher Site | Google Scholar
M. Yang, L. Li, J. Zhou, X. Qu, and D. Zhou, “Segmentation and inversion of the Hangjinqi fault zone, the northern Ordos basin (North China),” Journal of Asian Earth Sciences, vol. 70-71, pp. 64–78, 2013.
View at: Publisher Site | Google Scholar
G. Liu, Z. Huang, Z. Jiang, J. Chen, F. Chen, and J. Xing, “Gas adsorption capacity calculation limitation due to methane adsorption in low thermal maturity shale: a case study from the Yanchang Formation, Ordos Basin,” Journal of Natural Gas Science and Engineering, vol. 30, pp. 106–118, 2016.
View at: Publisher Site | Google Scholar
H. Klemme and G. Ulmishek, “Effective petroleum source rocks of the world: stratigraphic distribution and controlling depositional factors,” AAPG Bulletin-American Association of Petroleum Geologists, vol. 75, no. 12, pp. 1809–1851, 1991.
View at: Publisher Site | Google Scholar
W. Zhao, S. Hu, L. Hou et al., “Types and resource potential of continental shale oil in China and its boundary with tight oil,” Petroleum Exploration and Development, vol. 47, no. 1, pp. 1–11, 2020.
View at: Publisher Site | Google Scholar
H. Guo, W. Jia, P. Peng et al., “The composition and its impact on the methane sorption of lacustrine shales from the Upper Triassic Yanchang Formation, Ordos Basin, China,” Marine and Petroleum Geology, vol. 57, pp. 509–520, 2014.
View at: Publisher Site | Google Scholar
Q. Liu, P. Li, Z. Jin et al., “Organic-rich formation and hydrocarbon enrichment of lacustrine shale strata: a case study of Chang 7 member,” Science China Earth Sciences, vol. 65, no. 1, pp. 118–138, 2022.
View at: Publisher Site | Google Scholar
W. Z. Zhang, H. Yang, S. T. Fu, and C. L. Zan, “On the development mechanism of the lacustrine high-grade hydrocarbon source rocks of Chang 91 member in Ordos Basin,” Science in China Series D-Earth Sciences, vol. 50, no. S2, pp. 39–46, 2007.
View at: Publisher Site | Google Scholar
X. Wang, S. Gao, and C. Gao, “Geological features of Mesozoic lacustrine shale gas in south of Ordos Basin, NW China,” Petroleum Exploration and Development, vol. 41, no. 3, pp. 326–337, 2014.
View at: Publisher Site | Google Scholar
G. Liu, Z. Huang, F. Chen et al., “Reservoir characterization of Chang 7 member shale: a case study of lacustrine shale in the Yanchang Formation, Ordos Basin, China,” Journal of Natural Gas Science and Engineering, vol. 34, pp. 458–471, 2016.
View at: Publisher Site | Google Scholar
Y. Yang, W. Li, and L. Ma, “Tectonic and stratigraphic controls of hydrocarbon systems in the Ordos basin: a multicycle cratonic basin in Central China,” AAPG Bulletin, vol. 89, no. 2, pp. 255–269, 2005.
View at: Publisher Site | Google Scholar
Q. L. Guo, Y. Yao, L. H. Hou, S. H. Tang, S. Q. Pan, and F. Yang, “Oil migration, retention, and differential accumulation in "sandwiched" lacustrine shale oil systems from the Chang 7 member of the Upper Triassic Yanchang Formation, Ordos Basin, China,” International Journal of Coal Geology, vol. 261, article 104077, 2022.
View at: Publisher Site | Google Scholar
J. Tian, Q. Liang, F. Wang, J. Li, W. Yu, and W. Chen, “Sedimentary records of seismic events in a lacustrine basin of continental depression: a case study of the Triassic Yanchang formation in the Ordos Basin, northern China,” Journal of Asian Earth Sciences, vol. 228, article 105128, 2022.
View at: Publisher Site | Google Scholar
S. Liu, “The coupling mechanism of basin and orogen in the western Ordos Basin and adjacent regions of China,” Journal of Asian Earth Sciences, vol. 16, no. 4, pp. 369–383, 1998.
View at: Publisher Site | Google Scholar
W. Z. Zhang, H. Yang, S. T. Fu, and C. L. Zan, “A discussion about the development of high quality lacustrine source rocks from Chang 9-1 member in Ordos Basin,” Science in China Series D: Earth Science, vol. 37, Supplements I, pp. 33–38, 2007.
View at: Google Scholar
H. Yang, W. T. Dou, and X. Y. Liu, “Analysis on sedimentary faces of member 7 in Yanchang formation of Triassic in Ordos Basin,” Acta Sedimentologica Sinica, vol. 28, no. 2, pp. 254–263, 2010.
View at: Google Scholar
Q. H. Chen and W. H. Li, “The deep lacustrine sedimentary and its importance of oil-gas accumulation of Yanchang formation in late Triassic of Ordos Basin,” Science in China Series D: Earth Science, vol. 37, no. 1, pp. 39–48, 2007.
View at: Google Scholar
W. Z. Zhang, H. Yang, and Y. H. Yang, “Petroleum and element geochemistry and development environment of Yanchang formation Chang-7 high quality source rocks in Ordos Basin,” Geochemica, vol. 37, no. 1, pp. 59–64, 2008.
View at: Google Scholar
C. N. Zou, Z. Yang, S. Z. Tao et al., “Continuous hydrocarbon accumulation over a large area as a distinguishing characteristic of unconventional petroleum: the Ordos Basin, North-Central China,” Earth-Science Reviews, vol. 126, pp. 358–369, 2013.
View at: Publisher Site | Google Scholar
H. Yang and W. Z. Zhang, “Leading effect of the seventh member high-quality source rock of Yanchang Formation in Ordos Basin during the enrichment of low-penetrating oil-gas accumulation: geology and geochemistry,” Geochimica, vol. 34, no. 2, pp. 147–154, 2005.
View at: Google Scholar
X. W. Qiu, C. Y. Liu, Y. H. Li, G. Z. Mao, and J. Q. Wang, “Distribution characteristics and geological significances of tuff interlayers in Yanchang Formation of Ordos Basin,” Acta Sedmentologica Sinica, vol. 27, no. 6, pp. 1138–1146, 2009.
View at: Google Scholar
SY/T 5163-2010, Analysis method for clay minerals and ordinary non-clay minerals in sedimentary rocks by the X-ray diffraction, China Petroleum Standardization Committee, 2010.
J. Espitalie, J. L. Laporte, M. Madec et al., “Rapid method for source rocks characrerysation and for determination of petroleum potential and degree of evolution,” Revue De L Institut Francais Du Petrole, vol. 32, no. 1, pp. 23–42, 1977.
View at: Publisher Site | Google Scholar
J. Yuqiang, D. Dazhong, Q. Lin, S. Yanfei, J. Chan, and H. Fuwei, “The basic characteristic and evaluation of shale reservoir,” Natural Gas Industry, vol. 30, no. 10, pp. 7–12, 2010.
View at: Google Scholar
G. Liu and D. S. Zhou, “Application of trace elements analysis in identifying sedimentary environment: taking Qianjiang Formation in the Jianghan Basin as an example,” Petroleum Geology and Experiment, vol. 29, no. 3, pp. 307–310, 2007.
View at: Google Scholar
E. L. Couch, “Calculation of paleo-salinities from boron and clay mineral data,” AAPG Bulletin, vol. 55, no. 10, pp. 1829–1837, 1971.
View at: Publisher Site | Google Scholar
R. C. Zheng and M. Q. Liu, “Study on palaeo-salinity of Chang-6 oil reservoir set in Ordos Basin,” Oil & Gas Geology, vol. 20, no. 1, pp. 20–25, 1999.
View at: Google Scholar
Y. H. Fan, H. J. Qu, H. Wang, X. C. Yang, and Y. W. Feng, “The application of trace elements analysis to identifying sedimentary media environment: a case study of late Triassic strata in the middle part of western Ordos Basin,” Geology in China, vol. 39, no. 2, pp. 382–389, 2012.
View at: Google Scholar
J. R. Hatch and J. S. Leventhal, “Relationship between inferred redox potential of the depositional environment and geochemistry of the Upper Pennsylvanian (Missourian) Stark Shale Member of the Dennis Limestone, Wabaunsee County, Kansas, U.S.A.,” Chemical Geology, vol. 99, no. 1-3, pp. 65–82, 1992.
View at: Publisher Site | Google Scholar
B. Jones and D. A. C. Manning, “Comparison of geochemical indices used for the interpretation of palaeoredox conditions in ancient mudstones,” Chemical Geology, vol. 111, no. 1-4, pp. 111–129, 1994.
View at: Publisher Site | Google Scholar
M. Alberdi-Genolet and R. Tocco, “Trace metals and organic geochemistry of the Machiques Member (Aptian-Albian) and La Luna Formation (Cenomanian-Campanian), Venezuela,” Chemical Geology, vol. 160, no. 1-2, pp. 19–38, 1999.
View at: Publisher Site | Google Scholar
W. H. Tonger and Y. C. X. Liu, “The discussion on anoxic environments and its geochemical identifying indices,” Acta Sedimentologica Sinica, vol. 22, no. 2, pp. 365–372, 2004.
View at: Google Scholar
P. H. Nadeau, D. R. Peacor, J. Yan, and S. Hillier, “I-S precipitation in pore space as the cause of geopressuring in Mesozoic mudstones, Egersund Basin, Norwegian continental shelf,” American Mineralogist, vol. 87, no. 11-12, pp. 1580–1589, 2002.
View at: Publisher Site | Google Scholar
B. Thyberg and J. Jahren, “Quartz cementation in mudstones: sheet-like quartz cement from clay mineral reactions during burial,” Petroleum Geoscience, vol. 17, no. 1, pp. 53–63, 2011.
View at: Publisher Site | Google Scholar
H. J. Abercrombie, I. E. Hutcheon, J. D. Bloch, and P. de Caritat, “Silica activity and the smectite-illite reaction,” Geology, vol. 22, no. 6, pp. 539–542, 1994.
View at: Publisher Site | Google Scholar
B. Thyberg, J. Jahren, T. Winje, K. Bjørlykke, J. I. Faleide, and Ø. Marcussen, “Quartz cementation in Late Cretaceous mudstones, northern North Sea: changes in rock properties due to dissolution of smectite and precipitation of micro-quartz crystals,” Marine and Petroleum Geology, vol. 27, no. 8, pp. 1752–1764, 2010.
View at: Publisher Site | Google Scholar
P. C. van de Kamp, “Smectite-illite-muscovite transformations, quartz dissolution, and silica release in shales,” Clays and Clay Minerals, vol. 56, no. 1, pp. 66–81, 2008.
View at: Publisher Site | Google Scholar

Copyright

Copyright © 2023 Wang Zhang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

PDF Download Citation

Download other formats

Order printed copies

Views

155

Downloads

211

Citations