Characterizing the pore structure in the Silurian and Permian shales of the Sichuan Basin, China

Cao, Taotao; Song, Zhiguang; Wang, Sibo; Cao, Xinxing; Li, Yan; Xia, Jia

doi:10.1016/j.marpetgeo.2014.12.007

Cited by 217 publications

(99 citation statements)

References 31 publications

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“…However, the pore size distribution in shale matrix is generally characterized by bimodal instead of unimodal characteristics [10,16,[53][54][55][56], and from the analysis of SEM images (Figure 3), the pore size distribution of shale samples involved in this study are heterogeneous instead of homogeneous. Additionally, in the experimental approach used here, the gas concentration is not constant due to methane adsorption on the surface of shale powder sample throughout the single adsorption process (Figure 7).…”

Section: Methane Adsorption Rate Data: Application Of Unipore Modelmentioning

confidence: 89%

“…Previous studies [3,16] have shown that the gas adsorption rate behavior of coal or shale samples may be significantly affected by the pore size distribution and, thus, the sample which is homogeneous with respect to pore size distribution can be fitted well by the adsorption rate models based upon a unimodal pore structure. However, the pore size distribution in shale matrix is generally characterized by bimodal instead of unimodal characteristics [10,16,[53][54][55][56], and from the analysis of SEM images (Figure 3), the pore size The failure of applying the unipore diffusion model to describe gas adsorption and diffusion processes over the entire time range in coal or shale samples has also been reported. For example, in an early study conducted by Clarkson and Bustin [3] on coal samples, they found that both analytical and numerical unipore models developed by themselves failed to predict the methane and carbon dioxide adsorption rate data over the entire time range.…”

Section: Methane Adsorption Rate Data: Application Of Unipore Modelmentioning

confidence: 98%

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Methane Adsorption Rate and Diffusion Characteristics in Marine Shale Samples from Yangtze Platform, South China

et al. 2017

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Knowledge of the gas adsorption rate and diffusion characteristics in shale are very important to evaluate the gas transport properties. However, research on methane adsorption rate characteristics and diffusion behavior in shale is not well established. In this study, high-pressure methane adsorption isotherms and methane adsorption rate data from four marine shale samples were obtained by recording the pressure changes against time at 1-s intervals for 12 pressure steps. Seven pressure steps were selected for modelling, and three pressure steps of low (~0.4 MPa), medium (~4.0 MPa), and high (~7.0 MPa) were selected for display. According to the results of study, the methane adsorption under low pressure attained equilibrium much more quickly than that under medium and high pressure, and the adsorption rate behavior varied between different pressure steps. By fitting the diffusion models to the methane adsorption rate data, the unipore diffusion model based upon unimodal pore size distribution failed to describe the methane adsorption rate, while the bidisperse diffusion model could reasonably describe most of the experimental adsorption rate data, with the exception of sample YY2-1 at high pressure steps. This phenomenon may be related to the restricted assumption on pore size distribution and linear adsorption isotherm. The diffusion parameters α and β/α obtained from the bidisperse model indicated that both macro-and micropore diffusion controlled the methane adsorption rate in shale samples, as well as the relative importance and influence of micropore diffusion and adsorption to adsorption rate and total adsorption increased with increasing pressure. This made the inflection points, or two-stage process, at higher pressure steps not as evident as at low pressure steps, and the adsorption rate curves became less steep with increasing pressure. This conclusion was also supported by the decreasing difference values with increasing pressures between macro-and micropore diffusivities obtained using the bidisperse model, which is roughly from 10 −3 to 10 0 , and 10 −3 to 10 −1 , respectively. Additionally, an evident negative correlation between macropore diffusivities and pressure lower than 3-4 MPa was observed, while the micropore diffusivities only showed a gentle decreasing trend with pressure. A mirror image relationship between the variation in the value of macropore diffusivity and adsorption isotherms was observed, indicating the negative correlation between surface coverage and gas diffusivity. The negative correlation of methane diffusivity with pressure and surface coverage may be related to the increasing degree of pore blockage and the decreasing concentration gradient of methane adsorption. Finally, due to the significant deviation between the unipore model and experimental adsorption rate data, a new estimation method based upon the bidisperse model is proposed here.

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Section: Methane Adsorption Rate Data: Application Of Unipore Modelmentioning

confidence: 89%

Section: Methane Adsorption Rate Data: Application Of Unipore Modelmentioning

confidence: 98%

Methane Adsorption Rate and Diffusion Characteristics in Marine Shale Samples from Yangtze Platform, South China

et al. 2017

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“…To directly observe and obtain image by means of optical microscope, transmission electron microscope (TEM), scanning electron microscope (SEM), and other micro zone observation technologies in order to get the size, shape and distribution of pores and other qualitative informations in shales (Chalmers et al, 2012;Curtis et al, 2012;Loucks et al, 2012;Gu et al, 2015;Klaver et al, 2015Klaver et al, , 2016Li et al, 2015b;Tang et al, 2016;; (2) Indirect method. Mainly by means of probe gas adsorption techniques to quantitatively characterize the pore size and pore structure, including neutron scattering, high pressure mercury intrusion, low pressure gas adsorption and so on (Mastalerz et al, 2012(Mastalerz et al, , 2013Clarkson et al, 2013;Cao et al, 2015;Hu et al, 2015). Due to the complexity of sample preparation and limited observation area, microscopic observation method has a certain limit and generally only be used for qualitative analysis (Jiao et., 2014;Yang et al, 2016a,b;Zeng et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Neutron scattering is not ready yet for general use due to its high costs. Compared with the above methods, low pressure gas adsorption technology can avoid man-made macropore, and can also provide pore parameters such as pore distribution and specific surface area, therefore it has been widely used in the shale nanopore size analysis (Tian et al, 2013Cao et al, 2015;Pan et al, 2015;Zhang et al, 2015;Yang et al, 2016a,b,c;Zeng et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Quantitative characterization of micropore structure for organic-rich Lower Silurian shale in the Upper Yangtze Platform, South China: Implications for shale gas adsorption capacity

Chen

Jiang

Liu

et al. 2017

Adv. Geo-Energ. Res.

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The pores in shales are mainly of nanometer-scale, and their pore size distribution is very important for shale gas storage and adsorption capacity, especially micropores having widths less than 2 nm, which contribute to the main occurrence space for gas adsorption. This study is focused on the organic-rich Lower Silurian black shale from four wells in the Upper Yangtze Platform, and their total organic carbon (TOC), mineralogical composition and micropore characterization were investigated. Low pressure CO2 adsorption measurement was conducted at 273.15 K in the relative pressure range of 0.0001-0.03, and the micropore structure was characterized by Dubinin-Radushkevich (DR) equation and density functional theory (DFT) method and then the relationship between micropore structure and shale gas adsorption capacity was discussed. The results indicated that (1) The Lower Silurian shale have high TOC content in the range of 0.92-4.96%, high quartz content in the range of 30.6-69.5%, and high clays content in the range of 24.1-51.2%. The TOC content shows a strong positive relationship with the quartz content which suggests that the quartz is mainly biogenic in origin. (2) The micropore volume varies from 0.12 cm 3 /100 g to 0.44 cm 3 /100 g and micropore surface area varies from 4.97 m 2 /g to 17.94 m 2 /g. Both of them increase with increasing TOC content, indicating TOC is the key factor to control the micropore structure of the Lower Silurian shale. (3) Low pressure CO2 adsorption measurement provides the most suitable detection range (0.3-1.5 nm) and has high reliability and accuracy for micropore structure characterization. (4) The TOC content is the key factor to control gas adsorption capacity of the Lower Silurian shale in the Upper Yangtze Platform.

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“…The permeability was measured as pulse-decay permeability with a confining pressure 8 MPa and pore pressure 5 MPa. The rocks exhibit a bimodal pore-size distribution of both micropores and nanopores that vary in size from 30 m to 60 m and from 1.7 nm to 20 nm, respectively [27]. Figure 1 shows shale backscattered electron images.…”

Section: Introductionmentioning

confidence: 99%

Ion Diffusion Behavior between Fracturing Water and Shale and Its Potential Influence on Production

Shen

Zhu

Shi

et al. 2017

Journal of Chemistry

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Water imbibition, conductivity measurements, and ion identification were performed to investigate ion diffusion behavior between slick water and shale for large-scale hydraulic fracturing. The results indicated that there was strong ion exchange between water and shale. The ion concentration in water increases with fracture complexity and is dependent on the salinity of fracturing fluids. This implies that fracturing effects could be forecast from flow-back fluid ion concentrations after large-scale slick water fracturing. Higher levels of ion diffusion imply the presence of larger fracturing areas and higher level of fracture density for a similar reservoir. The mechanism of ion diffusion and the corresponding effects on IOR (increased oil recovery) based on a field example are discussed.

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Characterizing the pore structure in the Silurian and Permian shales of the Sichuan Basin, China

Cited by 217 publications

References 31 publications

Methane Adsorption Rate and Diffusion Characteristics in Marine Shale Samples from Yangtze Platform, South China

Methane Adsorption Rate and Diffusion Characteristics in Marine Shale Samples from Yangtze Platform, South China

Quantitative characterization of micropore structure for organic-rich Lower Silurian shale in the Upper Yangtze Platform, South China: Implications for shale gas adsorption capacity

Ion Diffusion Behavior between Fracturing Water and Shale and Its Potential Influence on Production

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