Characteristics of lacustrine shale porosity evolution, Triassic Chang 7 Member, Ordos Basin, NW China

Wu, Souheng; Zhu, Rixiang; Cui, Jinggang; Cui, Jingwei; Bai, Baojun; Zhang, Xiangxiang; Xu, Jin; Zhu, Desheng; You, Jianchang; Li, Xiaohong

doi:10.1016/s1876-3804(15)30005-7

Cited by 110 publications

(42 citation statements)

References 12 publications

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“…Negative correlations of micropores, mesopores, and macropores with quartz are presented in Figure 11D-F. The Shahezi shales are deeply buried (Table 1), therefore, under the effect of compaction, the primary pores between brittle grains gradually shrink and even disappear [52], indicating the siliceous minerals generally have a limited effect on the pore development. With the increase of clay mineral content, the pore volumes of micropores, mesopores and macropores all increase, indicating the various development of clay related pores in different pore size ranges ( Figure 11G-I and Table 4).…”

Section: The Impacts Of Lithofacies On Pore Structurementioning

confidence: 98%

The Impacts of Matrix Compositions on Nanopore Structure and Fractal Characteristics of Lacustrine Shales from the Changling Fault Depression, Songliao Basin, China

Liang

Jiang

et al. 2019

Minerals

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The Lower Cretaceous Shahezi shales are the targets for lacustrine shale gas exploration in Changling Fault Depression (CFD), Southern Songliao Basin. In this study, the Shahezi shales were investigated to further understand the impacts of rock compositions, including organic matters and minerals on pore structure and fractal characteristics. An integrated experiment procedure, including total organic carbon (TOC) content, X-ray diffraction (XRD), field emission-scanning electron microscope (FE-SEM), low pressure nitrogen physisorption (LPNP), and mercury intrusion capillary pressure (MICP), was conducted. Seven lithofacies can be identified according to on a mineralogy-based classification scheme for shales. Inorganic mineral hosted pores are the most abundant pore type, while relatively few organic matter (OM) pores are observed in FE-SEM images of the Shahezi shales. Multimodal pore size distribution characteristics were shown in pore width ranges of 0.5–0.9 nm, 3–6 nm, and 10–40 nm. The primary controlling factors for pore structure in Shahezi shales are clay minerals rather than OM. Organic-medium mixed shale (OMMS) has the highest total pore volumes (0.0353 mL/g), followed by organic-rich mixed shale (ORMS) (0.02369 mL/g), while the organic-poor shale (OPS) has the lowest pore volumes of 0.0122 mL/g. Fractal dimensions D1 and D2 (at relative pressures of 0–0.5 and 0.5–1 of LPNP isotherms) were obtained using the Frenkel–Halsey–Hill (FHH) method, with D1 ranging from 2.0336 to 2.5957, and D2 between 2.5779 and 2.8821. Fractal dimensions are associated with specific lithofacies, because each lithofacies has a distinctive composition. Organic-medium argillaceous shale (OMAS), rich in clay, have comparatively high fractal dimension D1. In addition, organic-medium argillaceous shale (ORAS), rich in TOC, have comparatively high fractal dimension D2. OPS shale contains more siliceous and less TOC, with the lowest D1 and D2. Factor analysis indicates that clay contents is the most significant factor controlling the fractal dimensions of the lacustrine Shahezi shale.

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Section: The Impacts Of Lithofacies On Pore Structurementioning

confidence: 98%

The Impacts of Matrix Compositions on Nanopore Structure and Fractal Characteristics of Lacustrine Shales from the Changling Fault Depression, Songliao Basin, China

Liang

Jiang

et al. 2019

Minerals

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“…Therefore, an integrated use of SANS and fluid-invasion techniques can distinguish accessible and inaccessible pores and provide a feasible approach to calculating closed porosity 19 , 23 , 28 , 37 . Nano-CT is another method capable of examining closed pores; however, it has a limitation of a voxel size of 50 nm for a sample size of only 65 μm 38 .In this study, the pore structure of four samples from typical American shale oil reservoirs (Niobrara, Wolfcamp, Bakken and Utica Formations; in the order of increasing geological age) was investigated using SANS, low-pressure nitrogen physisorption (LPNP), and MICP methods. The main purposes of this work are to (1) interpret porosity, pore-size distribution, and multiple-scale inaccessible porosity through multiple methods; and (2) compare the results for different oil shales and discuss the implications of different methods in studying pore structure of shale.…”

Section: Introductionmentioning

confidence: 99%

Integrating SANS and fluid-invasion methods to characterize pore structure of typical American shale oil reservoirs

Zhao

Jin

et al. 2017

Sci Rep

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An integration of small-angle neutron scattering (SANS), low-pressure N 2 physisorption (LPNP), and mercury injection capillary pressure (MICP) methods was employed to study the pore structure of four oil shale samples from leading Niobrara, Wolfcamp, Bakken, and Utica Formations in USA. Porosity values obtained from SANS are higher than those from two fluid-invasion methods, due to the ability of neutrons to probe pore spaces inaccessible to N 2 and mercury. However, SANS and LPNP methods exhibit a similar pore-size distribution, and both methods (in measuring total pore volume) show different results of porosity and pore-size distribution obtained from the MICP method (quantifying pore throats). Multi-scale (five pore-diameter intervals) inaccessible porosity to N 2 was determined using SANS and LPNP data. Overall, a large value of inaccessible porosity occurs at pore diameters <10 nm, which we attribute to low connectivity of organic matter-hosted and clay-associated pores in these shales. While each method probes a unique aspect of complex pore structure of shale, the discrepancy between pore structure results from different methods is explained with respect to their difference in measurable ranges of pore diameter, pore space, pore type, sample size and associated pore connectivity, as well as theoretical base and interpretation.

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“…However, studies on the dynamic evolution of nanoscale porosity are relatively lacking. Based on the limited literature, those studies mainly focused on the pore evolution of shale reservoirs in large-scale deposit basins, such as the Sichuan Basin and Ordos Basin, and ignored the evolution of shale reservoirs in small- to moderate-size basins in the northwestern region of China (Chen and Xiao, 2014; Cui et al., 2013; Tang et al., 2015; Wu et al., 2015; Xue et al., 2015). The Minhe Basin is located in northwestern China and has the character of being small but fat oil reservoir.…”

Section: Introductionmentioning

confidence: 99%

Evolution of nanopore structure in lacustrine organic-rich shales during thermal maturation from hydrous pyrolysis, Minhe Basin, Northwest China

Yang

Chen

et al. 2017

Energy Exploration & Exploitation

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The nanometer-scaled pore systems of gas shale reservoirs have a prominent contribution for gas storage. To obtain information about the characteristics of the nanopore structure within lacustrine organic-rich shales during their thermal evolution, artificial shale samples with different thermal maturities were obtained from a hydrous pyrolysis experiment. Nitrogen adsorption, field emission scanning electron microscopy, and porosity tests were used to investigate the characteristic pore structures of lacustrine shales with different thermal maturities from the Minhe Basin. The results show that the total organic carbon content decreased from 41.89% (unheated) to 27.7% (370 C) and that organic pores, intragranular pores of pyrite, and intergranular pores of clay minerals began to form with an increase in the simulated temperature and pressure. The porosity increased from 3.57% (unheated) to 26.09% (350 C) and then decreased to 20% (370 C) on the whole. The pore sizes were distributed from 1.7 to 500 nm, and the average pore diameter first showed a decreasing trend and then an increasing trend. The cumulative pore volume and cumulative specific surface area both presented a slowly increasing trend from an unheated status to 325 C, exhibited a rapid increase at 350 C, and then showed a slow increase at 370 C. This study could provide a reference for the exploration of shale gas in lacustrine shales with different thermal maturities.

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Characteristics of lacustrine shale porosity evolution, Triassic Chang 7 Member, Ordos Basin, NW China

Cited by 110 publications

References 12 publications

The Impacts of Matrix Compositions on Nanopore Structure and Fractal Characteristics of Lacustrine Shales from the Changling Fault Depression, Songliao Basin, China

The Impacts of Matrix Compositions on Nanopore Structure and Fractal Characteristics of Lacustrine Shales from the Changling Fault Depression, Songliao Basin, China

Integrating SANS and fluid-invasion methods to characterize pore structure of typical American shale oil reservoirs

Evolution of nanopore structure in lacustrine organic-rich shales during thermal maturation from hydrous pyrolysis, Minhe Basin, Northwest China

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