Petrophysical properties of the major marine shales in the Upper Yangtze Block, south China: A function of structural deformation

Zhu, Hongtao; Ju, Yi‐Hsu; Huang, Cheng; Qi, Yu; Ju, Liting; Yu, Kun; Li, Wuyang; Feng, Hongye; Qiao, Peng

doi:10.1016/j.marpetgeo.2019.08.003

Cited by 25 publications

(36 citation statements)

References 95 publications

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“…The positive correlation between porosity and quartz content has been reported in studies of major marine shale in south China [55] and Devonian gas shale in northern Canada [56]. Many studies attribute this correlation to rigid matrix minerals with high compressive strength, a high Young's modulus, and a low Poisson's ratio, which can create stress shadows that shield adjacent nanopores, especially the pores related to non-loadbearing minerals from compaction [48,57].…”

Section: Geological Controls On Pore Structure In Shale Samples From ...mentioning

confidence: 81%

Pore Structure in Shale Tested by Low Pressure N2 Adsorption Experiments: Mechanism, Geological Control and Application

et al. 2022

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The N2 adsorption experiment is one of the most important methods for characterizing the pore structure of shale, as it covers the major pore size range present in such sediments. The goal of this work is to better understand both the mechanisms and application of low-pressure nitrogen adsorption experiments in pore structure characterization. To achieve this, the N2 adsorption molecular simulation method, low-pressure N2 adsorption experiments, total organic carbon (TOC) analysis, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and a total of 196 shale samples from the Wufeng–Longmaxi formations in the Sichuan basin have been employed in this study. Based on the analytical data and the simulations, two parameters, the connectivity index and the large pore volume index, are proposed. These parameters are defined as the connectivity of the pore system and the volume of large nanopores (>10 nm) respectively, and they are calculated based on the N2 adsorption and desorption isotherms. The experimental results showed that TOC content and clay minerals are the key factors controlling surface area and pore volume. However, in different shale wells and different substrata (divided based on graptolite zonation), the relative influences of TOC content and clay minerals on pore structure differ. In three of the six wells, TOC content is the key factor controlling surface area and pore volume. In contrast, clay minerals in samples from the W202 well are the key factors controlling pore volume, and with an increase in the clay mineral content, the pore volume increases linearly. When the carbonate content exceeds 50%, the pore volume decreases with an increase in carbonate content, and this may be because in the diagenetic process, carbonate cement fills the pores. It is also found that with increasing TOC content the connectivity index increases and SEM images also illustrate that organic pores have better connectivity. Furthermore, the connectivity index increases as quartz content increases. The large pore volume index increases with quartz content from 0 to 40% and decreases as quartz increases from 40% to 100%. By comparing the pore structure of shale in the same substrata of different shale gas wells, it was found that tectonic location significantly affects the surface area and pore volume of shale samples. The shale samples from wells that are located in broad tectonic zones, far from large-scale faults and overpressure zones, have larger pore volumes and surface areas. On the contrary, the shale samples from shale gas wells that are located in the anticline region with strong tectonic extrusion zones or near large-scale faults have relatively low pore volumes and surface areas. By employing large numbers of shale samples and analyzing N2 adsorption mechanism in shale, this study has expanded the application of N2 adsorption experiment in shale and clarifies the effects of sedimentary factors and tectonic factors on pore structure.

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Section: Geological Controls On Pore Structure In Shale Samples From ...mentioning

confidence: 81%

Pore Structure in Shale Tested by Low Pressure N2 Adsorption Experiments: Mechanism, Geological Control and Application

et al. 2022

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“…It is worth noting that the observation of the shale cores from several wells in the Jiaoshiba anticline shows that O 3 w has more structural fractures and calcite and quartz veins filled in the fractures compared to the Longmaxi Formation 37 . In the middle‐lower part of O 3 w , compressed fractured layers and structural phenomena reflecting the layered compressional decollement (such as secondary detachment surface scratches, microdetachment folds, and imbricate structures) are also developed 56,57 . This may indicate that against the background of the tectonic stress of the regional compressive nappe, O 3 w is located at the bottom of a set of soft formations of the O 3 w ‐S 1 l 1 shales, which are located above the underlying hard strata of carbonates, and the bottom of the O 3 w shale is the main detachment surface.…”

Section: Discussionmentioning

confidence: 99%

Structural characteristics and porosity estimation of organic matter‐hosted pores in gas shales of Jiaoshiba Block, Sichuan Basin, China

Zhang

et al. 2020

Energy Science & Engineering

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“…For example, compared with the Antrim shale in the United States and Yangxin shale in the Jiyang Depression of Shandong Province, the types and sizes of reservoir spaces have different characteristics [15]. The reservoir spaces of Antrim shale and Yangxin shale gas reservoirs in the Jiyang Depression are dominated by natural fractures, while the pores of shale in the Sanhu area are relatively developed (porosity can reach 10~35%) and the physical properties are better, which are more suitable for the formation of shale gas (Table 1) [16,17]. Therefore, the study and analysis of the formation conditions of biological shale gas reservoirs are of the most practical significance for the increase of natural gas reserves and production in the Qinghai Oilfield [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Dynamic Accumulation of the Quaternary Shale Biogas in Sanhu Area of the Qaidam Basin, China

Shao

Hou

et al. 2022

Energies

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Biogas resources in the Sanhu area of the Qaidam Basin have great potential, but there are few studies on biogas from shale, especially on the accumulation conditions of shale biogas. The study of biogas accumulation conditions of quaternary shale in the Sanhu area is of great significance to the theory of biogas accumulation and the guidance of exploration and development. This paper takes Quaternary shale in the Sanhu area as the research object. It is analyzed from multiple perspectives of shale hydrocarbon generation conditions, reservoir conditions, as well as hydrodynamic and structural conditions. Through the experiments of soluble organic carbon analysis and porosity and permeability analysis, the accumulation conditions of shale biogas reservoirs are clarified. The results show that the quaternary shale has a high soluble organic carbon content and high salinity formation water, which is conducive to late methane biochemical generation. Quaternary shale has the characteristics of high porosity and low permeability, mainly developing intergranular pores and intragranular pores. The large pore volume and specific surface area provide a lot of storage space for free gas and adsorbed gas, and the reservoir conditions are good. Under the structural characteristics of high in the south and low in the north and the action of formation hydrodynamics, biogas migrated from the south and deep to the north of the basin. The north slope is the main biogas-rich zone. On the whole, the quaternary shale in the Sanhu area has the characteristics of continuous hydrocarbon generation and dynamic accumulation, which has huge resource potential and exploration and development value.

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Petrophysical properties of the major marine shales in the Upper Yangtze Block, south China: A function of structural deformation

Cited by 25 publications

References 95 publications

Pore Structure in Shale Tested by Low Pressure N2 Adsorption Experiments: Mechanism, Geological Control and Application

Pore Structure in Shale Tested by Low Pressure N2 Adsorption Experiments: Mechanism, Geological Control and Application

Structural characteristics and porosity estimation of organic matter‐hosted pores in gas shales of Jiaoshiba Block, Sichuan Basin, China

Dynamic Accumulation of the Quaternary Shale Biogas in Sanhu Area of the Qaidam Basin, China

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