Pore structure of transitional shales in the Ordos Basin, NW China: Effects of composition on gas storage capacity

Xiong, Fengyang; Jiang, Zhenxue; Li, Peng; Wang, Xiangzeng; Bi, He; Li, Yirun; Wang, Ziyuan; Amooie, Mohammad Amin; Soltanian, Mohamad Reza; Moortgat, Joachim

doi:10.1016/j.fuel.2017.05.083

Cited by 107 publications

(78 citation statements)

References 55 publications

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“…Unlike conventional reservoirs, shales commonly exhibit a complex and heterogeneous pore system and a wide pore size distribution with low porosity and permeability [1,11,12], so it is difficult for pore structure characterization. At present, research works associated with pore system mainly focus on shale pore observation, the classification of pores, the characterization of pore size distribution, factors influencing pore development, and its effect on gas storage and enrichment [13][14][15][16]. Due to the variety and complexity of shale pores, several pore system classification schemes have been proposed by researchers to describe various pore types in shale [13,[17][18][19]].…”

Section: Introductionmentioning

confidence: 99%

Full-Scale Pore Structure and Fractal Dimension of the Longmaxi Shale from the Southern Sichuan Basin: Investigations Using FE-SEM, Gas Adsorption and Mercury Intrusion Porosimetry

et al. 2019

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Pore structure determines the gas occurrence and storage properties of gas shale and is a vital element for reservoir evaluation and shale gas resources assessment. Field emission scanning electron microscopy (FE‐SEM), high‐pressure mercury intrusion porosimetry (HMIP), and low‐pressure N2/CO2 adsorption were used to qualitatively and quantitatively characterize full‐scale pore structure of Longmaxi (LM) shale from the southern Sichuan Basin. Fractal dimension and its controlling factors were also discussed in our study. Longmaxi shale mainly developed organic matter (OM) pores, interparticle pores, intraparticle pores, and microfracture, of which the OM pores dominated the pore system. The pore diameters are mainly distributed in the ranges of 0.4–0.7 nm, 2–20 nm and 40–200 μm. Micro‐, meso‐ and macropores contribute 24%, 57% and 19% of the total pore volume (PV), respectively, and 64.5%, 34.6%, and 0.9% of the total specific surface area (SSA). Organic matter and clay minerals have a positive contribution to pore development. While high brittle mineral content can inhibit shale pore development. The fractal dimensions D1 and D2 which represents the roughness of the shale surface and irregularity of the space structure, respectively, are calculated based on N2 desorption data. The value of D1 is in the range of 2.6480–2.7334 (average of 2.6857), D2 is in the range of 2.8924–2.9439 (average of 2.9229), which indicates that Longmaxi shales have a rather irregular pore morphology as well as complex pore structure. Both PV and SSA positively correlated with fractal dimensions D1 and D2. The fractal dimension D1 decreases with increasing average pore diameter, while D2 is on the contrary. These results suggest that the small pores have a higher roughness surface, while the larger pores have a more complex spatial structure. The fractal dimensions of shale are jointly controlled by OM, clays and brittle minerals. The TOC content is the key factor which has a positive correlation with the fractal dimension. Clay minerals have a negative influence on fractal dimension D1, and positive influence D2, while brittle minerals show an opposite effect compared with clay minerals.

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Section: Introductionmentioning

confidence: 99%

Full-Scale Pore Structure and Fractal Dimension of the Longmaxi Shale from the Southern Sichuan Basin: Investigations Using FE-SEM, Gas Adsorption and Mercury Intrusion Porosimetry

et al. 2019

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“…7. High kaolinite (clay) content of the carboniferous and Permian mudstone was also reported by Xiong et al (2017). The mineral compositions are distinct from those of marine shales, which commonly have more carbonate, quartz, and illite (Bu et al, 2015;Lyu et al, 2018).…”

Section: Sample Features and Optical Microscopic Imagesmentioning

confidence: 72%

Geological Controls on High Production of Tight Sandstone Gas in Linxing Block, Eastern Ordos Basin, China

Meng

et al. 2020

Acta Geologica Sinica (Eng)

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Tight sandstone gas in the Linxing Block, eastern Ordos Basin, has been successfully exploited. The high performance is mainly a result of the special geological conditions. The key geological controls for high production have been discussed on the basis of seismic data, field observation, sample features, mercury porosimetry, mechanical properties, and basin modeling. Firstly, the coal measures have good gas generation potential, not only because of the existence of coalbeds and organic‐rich shales, but also because coal laminae and microbial mats in the shales significantly increase their total organic carbon (TOC) contents. Secondly, except for the uplifted zone of the Zijinshan complex and the eastern fault zone, rare large faults develop in the Carboniferous–Permian sequence, ensuing the sealing capacity of cap rock. Small fractures generally concentrated in the sandstones rather than the mudstones. Thirdly, gas accumulation in the Linxing Block was controlled by the tectonic, burial and thermal histories. Gas accumulation in the Linxing Block started in the Late Triassic, followed by three short pauses of thermal maturation caused by relatively small uplifts; the maximum hydrocarbon generation period is the Early Cetaceous as a combined result of regional and magmatic thermal metamorphisms. Field profiles show abundant fractures in sandstone beds but rare fractures in mudstone beds. Mechanical properties, determined by lithostratigraphy, confine the fractures in the sandstones, increasing the permeability of sandstone reservoirs and retaining the sealing capacity of the mudstone cap rocks. The modern ground stress conditions favor the opening of predominant natural fractures in the NNW–SSE and N–S directions. These conclusions are useful for exploring the potential tight sandstone gas field.

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“…According to the interpretation process of adsorption isotherm proposed by (Sing et al, 1985), the isotherms type should be first identified; then the adsorption mechanism should be identified to be monolayermultilayer adsorption, capillary condensation or micropore filling; the last to be identified is the hysteresis loop type. These factors are all related to pore types and pore structure (Kuila et al, 2013;Labani et al, 2013;Xiong et al, 2017).…”

Section: N 2 Adsorption Resultsmentioning

confidence: 99%

Full‐Sized Pore Structure and Fractal Characteristics of Marine‐Continental Transitional Shale: A Case Study in Qinshui Basin, North China

Yin

Guo

2019

Acta Geologica Sinica (Eng)

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Based on 10 shale samples collected from 4 wells in Qinshui Basin, we investigate the full-sized pore structure and fractal characteristics of Marine-Continental transitional shale by performing organic geochemistry, mineralogical composition, Nitrogen gas adsorption (N 2 adsorption) and Nuclear Magnetic Resonance (NMR) measurements and fractal analysis. Results show that the TOC content of the shale samples is relatively high, with an average value of 2.44wt%, and the thermal evolution is during the mature-over mature stage. The NMR T 2 spectrum can be used to characterize the fullsized pore structure characteristics of shale. By combining N 2 adsorption pore structure parameters and NMR T 2 spectrums, the surface relaxivity of samples are calculated to be between 1.7877 um/s and 5.2272 um/s. On this basis, the T 2 spectrums are converted to full-sized pore volume and surface area distribution curves. The statistics show that the pore volume is mainly provided by mesopore, followed by micropore, and the average percentages are 65.04% and 30.83% respectively; the surface area is mainly provided by micropore, followed by mesopore, and the average percentages are 60.8004% and 39.137% respectively; macropore contributes little to pore volume and surface area. The pore structure characteristics of shale have no relationship with TOC, but strong relationships with clay minerals content. NMR fractal dimensions D micro and D meso have strong positive relationships with the N 2 adsorption fractal dimensions D 1 and D 2 respectively, indicating that D micro can be used to characterize the fractal characteristics of pore surface, and D meso can be used to characterize the fractal characteristics of pore structure. The shale surface relaxivity is controlled by multiple factors. The increasing of clay mineral content, pore surface area, pore surface fractal dimension and the decreasing of average pore size, will all lead to the decreasing of shale surface relaxivity.

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Pore structure of transitional shales in the Ordos Basin, NW China: Effects of composition on gas storage capacity

Cited by 107 publications

References 55 publications

Full-Scale Pore Structure and Fractal Dimension of the Longmaxi Shale from the Southern Sichuan Basin: Investigations Using FE-SEM, Gas Adsorption and Mercury Intrusion Porosimetry

Full-Scale Pore Structure and Fractal Dimension of the Longmaxi Shale from the Southern Sichuan Basin: Investigations Using FE-SEM, Gas Adsorption and Mercury Intrusion Porosimetry

Geological Controls on High Production of Tight Sandstone Gas in Linxing Block, Eastern Ordos Basin, China

Full‐Sized Pore Structure and Fractal Characteristics of Marine‐Continental Transitional Shale: A Case Study in Qinshui Basin, North China

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