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

Liu, Guoheng; Zhai, Gangyi; Yang, Rui; He, Tingpeng; Wei, Bin

doi:10.1007/s11430-020-9718-2

Cited by 16 publications

(14 citation statements)

References 40 publications

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“…As shown in Figure 10(b), the porosity is positively correlated with quartz content of shales. On the one hand, such a positive correlation may be resulted from widespread development of biological quartz fragments in marine shales [181][182][183][184]. The presence of biogenic silica 12 Geofluids can indirectly denote high TOC values [122], which can help increase porosity of shales, especially for OM pores.…”

Section: Tectonic Deformationmentioning

confidence: 99%

Lower Cambrian Organic-Rich Shales in Southern China: A Review of Gas-Bearing Property, Pore Structure, and Their Controlling Factors

Gao

Xiao

et al. 2022

Geofluids

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The Lower Cambrian shales are widely developed in southern China, with greater thicknesses and higher TOC contents. Although the shale gas resource potential has been suggested to be huge, the shale gas exploration and development is not satisfactory. At present, the gas-bearing property evaluation of the Lower Cambrian shale is still a hot spot of concern. According to previous works, this paper systematically summarizes the gas-bearing characteristics and controlling factors of the Lower Cambrian shales in southern China. The buried depth of Lower Cambrian shales mainly ranges from 3000 m to 6000 m, and the thickness of organic-rich shale intervals ( TOC > 2 % ) varies from 20 m to 300 m. The TOC content and EqVRo value are generally up to 2%-10% and 2.5%-6.0%, respectively. The gas content of the Lower Cambrian shales in the Weiyuan-Qianwei block of the Sichuan Basin and the western Hubei area generally exceeds 2 m3/t, and gas composition is dominated by CH4. In southeastern Chongqing, northwestern Hunan, and northern Guizhou areas, the gas content of the Lower Cambrian shales is generally <2 m3/t, and the N2 content is generally >60%. In the Lower Yangtze region, the Lower Cambrian shale reservoirs basically contain no gas. Higher maturity, lower porosity, and less-no organic pores are suggested to be responsible for low gas contents and/or the predominate of N2 in shale gas reservoirs. Strong tectonic deformation is an important factor leading to the massive gas loss from shale reservoirs, thus resulting in no gas or only a small amount of N2 in the Lower Cambrian shales. In a word, the Lower Cambrian shale gas plays with low maturity and relatively stable tectonic condition, especially deep-ultradeep zones, may be the favorable targets for shale gas exploration.

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Section: Tectonic Deformationmentioning

confidence: 99%

Lower Cambrian Organic-Rich Shales in Southern China: A Review of Gas-Bearing Property, Pore Structure, and Their Controlling Factors

Gao

Xiao

et al. 2022

Geofluids

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“…The simulation experiments demonstrated that the charging front of the migration layer was basically flat (i.e., planer; see Figures 4d-f and 6b-d). Some scholars believe that charging occurs in a branch-like manner [23][24][25]; however, the core displacement imaging experiment cannot prove whether the charging occurs in a branch-like way or not. The results support the idea that the driving front is flat, with gradual changes in water saturation.…”

Section: Sample A25 Experimental Results and Discussion Of Driving Fr...mentioning

confidence: 99%

Gas–Water Characteristics of Tight Sandstone in Xihu Sag, East China Sea Basin under Different Charging Models

Chen

Huang

et al. 2023

Processes

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The Xihu sag has two main oil−gas fields: Huagang Gas Field and Pinghu Oil Field. The Huagang formation is the reservoir of the Huagang Gas Field in the Central Tectonic Zone, while the Pinghu formation is the reservoir of the Pinghu Oil Field in the Western Slope Zone. In this paper, which mainly focusses on the Huagang formation, we conducted gas-driven water displacement–magnetic resonance imaging (GWD-MRI) experiments to simulate the charging characteristics of the sandstone migration layer, centrifugal magnetic resonance (Cen-NMR) experiments to simulate the short-term rapid trap charging process, and semi-permeable baffle (SPB) charging experiments to simulate the slow trap accumulation process. The results indicate that a start-up pressure exists for migration layer charging, where the start-up pressure for a core with a permeability of 0.3 mD is about 0.6 MPa. Our experimental simulations confirm that a planar front of changing water saturation exists, which has a width of about 1–1.5 cm. Migration layer charging is mainly influenced by two actions: the drive effect and the carrying effect. The drive effect can reduce the water saturation to 70–80%, while the carrying effect can further reduce the water saturation by 5–10%. The water saturation in the rapid charging scenario is mainly affected by the petrophysical characteristics of the rock: if the porosity is high, the water saturation is low. The water saturation decreases significantly with the increase in centrifugal force when the centrifugal force is small; however, when the centrifugal force is greater than 0.8 MPa, the water saturation decreases slowly. In the slowly charging trap experiment, the water saturation was basically stable at 40–50%, which matched the measured water saturation of the airtight cores well (ranging from 40–55%), and the petrophysical characteristics of the rock did not have a significant effect on the final water saturation.

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“…Successful exploration of shale gas in previous years has aroused wide public concern about the shale reservoir [1][2][3][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.…”

Section: Introductionmentioning

confidence: 99%

“…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].…”

Section: Introductionmentioning

confidence: 99%

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

Zhang,

Liang,

et al. 2023

Geofluids

Self Cite

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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.

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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

Cited by 16 publications

References 40 publications

Lower Cambrian Organic-Rich Shales in Southern China: A Review of Gas-Bearing Property, Pore Structure, and Their Controlling Factors

Lower Cambrian Organic-Rich Shales in Southern China: A Review of Gas-Bearing Property, Pore Structure, and Their Controlling Factors

Gas–Water Characteristics of Tight Sandstone in Xihu Sag, East China Sea Basin under Different Charging Models

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

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