Experimental investigation of the characteristics of organic matter pores in Chang 7 member lacustrine shale from the Ordos Basin due to organic matter evolution induced by hydrous pyrolysis

Chen, Jian; Jiang, Fujie; Hu, Tao; Wang, Zhifang; Xu, Ziyang; Peng, Junwen; Chen, Di; Li, Longlong

doi:10.1016/j.jngse.2016.08.069

Cited by 18 publications

(7 citation statements)

References 32 publications

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“…In addition, Chen et al proposed that tortuosity (τ), which can be calculated through mercury intrusion, can be used to evaluate pore connectivity and permeability [62], with higher τ values indicating poor connectivity and low permeability ( Figure 13a). As shown in Figure 13b, tortuosity (τ) had a positive relationship with the fractal dimension, indicating that shale with a higher fractal dimension D had poorer connectivity and lower permeability.…”

Section: Effect Of Fractal Dimension On Permeabilitymentioning

confidence: 99%

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Tang

Wang

et al. 2018

Minerals

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A suite of shale samples from the Lower Cambrian Niutitang Formation in northwestern Hunan Province, China, were investigated to better understand the pore structure and fractal characteristics of marine shale. Organic geochemistry, mineralogy by X-ray diffraction, porosity, permeability, mercury intrusion and nitrogen adsorption and methane adsorption experiments were conducted for each sample. Fractal dimension D was obtained from the nitrogen adsorption data using the fractal Frenkel-Halsey-Hill (FHH) model. The relationships between total organic carbon (TOC) content, mineral compositions, pore structure parameters and fractal dimension are discussed, along with the contributions of fractal dimension to shale gas reservoir evaluation. Analysis of the results showed that Niutitang shale samples featured high TOC content (2.51% on average), high thermal maturity (3.0% on average), low permeability and complex pore structures, which are highly fractal. TOC content and mineral compositions are two major factors affecting pore structure but they have different impacts on the fractal dimension. Shale samples with higher TOC content had a larger specific surface area (SSA), pore volume (PV) and fractal dimension, which enhanced the heterogeneity of the pore structure. Quartz content had a relatively weak influence on shale pore structure, whereas SSA, PV and fractal dimension decreased with increasing clay mineral content. Shale with a higher clay content weakened pore structure heterogeneity. The permeability and Langmuir volume of methane adsorption were affected by fractal dimension. Shale samples with higher fractal dimension had higher adsorption capacity but lower permeability, which is favorable for shale gas adsorption but adverse to shale gas seepage and diffusion.

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Section: Effect Of Fractal Dimension On Permeabilitymentioning

confidence: 99%

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Tang

Wang

et al. 2018

Minerals

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“…For example, Mastalerz et al [16] observed that total porosity increases with clay and quartz content and decreases with carbonate content. Ji et al [38] and Chen et al [39,40] concluded that the biogenic quartz in marine shale was typically accompanied by abundant pores, whereas the quartz in marine-continental transitional shale or continental shale had little influence on the pore structure. Milliken et al [17] proposed higher clay content may allow the collapse of OM pores and interparticle pores, especially for deeply buried shales that have undergone immense compaction [40].…”

Section: Introductionmentioning

confidence: 99%

Petrographic Characterization and Maceral Controls on Porosity in Overmature Marine Shales: Examples from Ordovician-Silurian Shales in China and the U.S.

et al. 2021

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The pore structure characterization and its controlling factors in overmature shales are keys to understand the shale gas accumulation mechanism. Organic matter in source rocks is a mixture of various macerals that have their own specific evolutionary pathways during thermal maturation. Pores within macerals also evolve following their own path. This study focused on petrographic characterization and maceral controls on porosity in overmature marine shales in China and the United States. Shale from Ordos Basin in China was also selected as an example of overmature transitional shale for maceral comparison. Organic petrology techniques were used to identify maceral types and describe morphological features in detail; scanning electron microscopy techniques were then used to document the abundance and development of pores within macerals. Helium measurement, mercury intrusion capillary pressure, and CO2 adsorption were especially applied to quantify the pore structure of Wufeng-Longmaxi shale from Sichuan Basin in China. The vitrinite reflectance equivalent of the studied overmature samples is ~2.4%. The macerals within the studied marine shales are composed mainly of pyrobitumen and zooclasts. At this maturity, pyrobitumen develops abundant gas-related pores, and their volume positively correlates to gas content. Three types of pyrobitumen and its related pore structure are characterized in Wufeng-Longmaxi shales. Zooclasts contribute to total organic carbon (TOC) content but little to porosity. When the TOC content is above 1.51% in Wufeng-Longmaxi samples, the TOC content positively correlates to quartz content. Organic matter strongly controls micropore development. Pores of diameter ~ 0.5 nm provide a significant amount of micropore volume. Clay mineral and quartz contents control micro- and macropore increments in organic-lean shales. MICP results indicate that pores within 3-12 nm and 900-2500 nm account for a major contribution to pore volume obtained. Determining the proportions of pyrobitumen to zooclasts within the total organic matter in pre-Devonian organic-rich marine shales is important in predicting porosity and gas storage capacity in high-maturity shales.

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“…Pyrolysis studies on organic-rich shales showed that a large number of nanopores are formed from organic matter as maturity increases. ,− With an increasing pyrolysis temperature, the number, volume, and surface area of micro-, meso-, and macropores increase in organic-rich shales . The number of nanoscale pores in organic-rich mudstone and shale increases with increasing temperature and pressure, and the peak temperature is consistent with the yield peak temperature of gaseous and liquid hydrocarbons.…”

Section: Introductionmentioning

confidence: 75%

Nanoscale Pore Changes in a Marine Shale: A Case Study Using Pyrolysis Experiments and Nitrogen Adsorption

et al. 2018

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Nanoscale pores have an important role in the accumulation of gas in shale gas reservoirs. Indeed, the formation of nanopores is critical for the characterization and evaluation of a shale reservoir. Moreover, the effect of pyrolysis on the modification of nanopores is not clear. Therefore, this paper focuses on pyrolysis and nitrogen adsorption experiments to examine the nanoscale pore structure and evolution in marine shale strata with low total organic carbon content. All of the examined samples contain micro-, meso-, and macropores. The results show that the number of micropores increased as a result of artificial maturation (i.e., pyrolysis), which resulted in a significant increase in the surface area and the total pore volume. The openness of the pores significantly increased when the maturity was higher than 2.5% R o (vitrinite reflectance). The 1.5–7.5 and 60–70 nm pores are the most pronounced to change after pyrolysis. Furthermore, liquid hydrocarbons produced during heating were shown to influence pores of approximately 41 nm width. In the overmature stage (R o = 2.77%), the number of pores and pore volume significantly increased during pyrolysis. The pore structure of the overmature shale was different from that of the shale during the mature and high-maturity stages. Pores less than 20 nm wide nearly provided 90% of the surface area and at least 50% of the pore volume. The transformation of organic matter from the solid state to the liquid and gas states is most closely related to the number of mesopores. The pores with sizes less than 10 nm in width have the greatest change in the proportion of the surface area to pore volume with increasing maturation.

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Experimental investigation of the characteristics of organic matter pores in Chang 7 member lacustrine shale from the Ordos Basin due to organic matter evolution induced by hydrous pyrolysis

Cited by 18 publications

References 32 publications

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Petrographic Characterization and Maceral Controls on Porosity in Overmature Marine Shales: Examples from Ordovician-Silurian Shales in China and the U.S.

Nanoscale Pore Changes in a Marine Shale: A Case Study Using Pyrolysis Experiments and Nitrogen Adsorption

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