Pore characteristics differences between clay-rich and clay-poor shales of the Lower Cambrian Niutitang Formation in the Northern Guizhou area, and insights into shale gas storage mechanisms

Wu, Chenjun; Tuo, Jincai; Zhang, Leifu; Zhang, Mingfeng; Li, Jing; Liu, Yan; Qian, Yu

doi:10.1016/j.coal.2017.04.009

Cited by 78 publications

(30 citation statements)

References 46 publications

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“…Hence, free gas is closely related to the porosity, whereas adsorbed gas is controlled and could be characterized by specific surface area (Montgomery et al, 2005;Ross and Bustin, 2007;Mosher et al, 2013). For the Permian shales studied, they have a high specific surface area of 1.05-49.25 m 2 /g, with an average of 15.70 m 2 /g, which is greater than that of marine Lower Cambrian shale in northern Guizhou region Wu et al, 2017) and approximate to the Longmaxi Formation shale in the Middle Yangtze region, central China . Hg-porosities of 32 shale samples, ranging between 0.68% and 8.9% with most less than 4%, are higher than the Lower Cambrian shale in north Guizhou (Wu et al, 2017;Xia et al, 2017) and…”

Section: Comparison Of Physical Property Between Permian Intervalsmentioning

confidence: 99%

Characteristics and controlling factors of pore structure of the Permian shale in southern Anhui province, East China

Cao

Deng

Song

et al. 2018

Journal of Natural Gas Science and Engineering

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The Permian shale reservoir in southern Anhui province, East China is regarded as a promising target for shale gas exploration. In order to investigate the characteristics of shale pore structures and their controlling factors, total organic carbon (TOC), Rock-eval, organic petrology, X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), nitrogen gas adsorption (N 2 GA), mercury intrusion porosimetry (MIP) and helium pycnometry were conducted on the Permian shales collected from two shale gas parameter wells. The results indicate that the BET surface areas determined by N 2 GA method vary between 1.05 and 49.25 m 2 /g. The porosities derived from MIP and helium pycnometry tests are in the range of 0.68%-8.9% and 1.15%-9.79%, respectively. FE-SEM reveals that organic matter (OM) pores and cracks are well developed in the Permian shales, though some OM grains contain few pores, which might be related to the maceral composition. At a high maturity stage, vitrinite do not develop secondary OM pores, and sapropelinite generally develop abundant OM (H. Luo).the shales of the Gufeng and Dalong Formations display a higher TOC content and a better physical property than the Longtan Formation shales and appear to be superior prospective shale gas exploration potential.

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Section: Comparison Of Physical Property Between Permian Intervalsmentioning

confidence: 99%

Characteristics and controlling factors of pore structure of the Permian shale in southern Anhui province, East China

Cao

Deng

Song

et al. 2018

Journal of Natural Gas Science and Engineering

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“…Mineral composition was considered as an important parameter for evaluating shale reservoirs and shale gas exploitation (Chen, Sun, et al, ; Wu et al, ). Generally, shale gas reservoirs that have economically effective usually contain the conditions described below: TOC > 2.0%, brittle minerals content > 40%, and continuous shale thickness > 30–50 m (Jarvie, Hill, Ruble, & Pollastro, ).…”

Section: Discussionmentioning

confidence: 99%

“…Chen, Han, et al, observed that the surface porosity of organic matter is similar to that of clay minerals in Longmaxi shale by selecting randomly SEM photos, but the latter shows a strong heterogeneity. Clay‐rich shales contain higher pore volume, specific surface area, porosity, and maximum nitrogen quantity absorbed than clay‐poor shale for Niutitang shale in the same conditions of TOC (Wu et al, ). In our data, Longmaxi shales in UY have the highest clay mineral contents and show benign economically effective, whereas Niutitang shales in LY contain the lowest clay mineral contents and have not got creationary achievement in the field of shale gas.…”

Section: Discussionmentioning

confidence: 99%

Mineralogy and geochemical investigation of Cambrian and Ordovician–Silurian shales in South China: Implication for potential environment pollutions

et al. 2019

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Rapid expansion of shale gas development in China raises environmental and human health concerns. Several studies present related information on these concerns in the United States and Canada, yet they are few in China at present. This paper presents a series of original and published mineralogical and trace elements data from two gas shales (Niutitang shale and Longmaxi shale) considered as producing gas shale in China. Mineralogical and geochemical data surveyed can be applied to evaluate the potential environment pollutions during shale weathering and hydraulic fracturing. After compilations of the mineralogical and trace elements data, we can conclude that (a) there is generally more pyrite compared with carbonate for Niutitang shales, indicating that Niutitang shales are more prone to generate the hydrogen ions than Longmaxi shales; (b) many of the environmental hazardous trace elements considered here show an association with organic matter and/or pyrite, indicating that these trace elements are prone to mobilize and release during shale weathering and hydraulic fracturing; (c) some environmental hazardous elements like As, Ni, and Ba that have extremely high concentrations in some regions as compared with the screening limits for soil and drinking water should attract more attention; and (d) clay-rich shale with abundant organic matter may be the most favourable shale gas reservoir for the Niutitang shale, especially for those shales in Lower Yangtze region. Moreover, more mineralogical and geochemical data will be required for a comprehensive environmental impacts assessment. KEYWORDS environmental and human impacts, mineralogy, pyrite oxidization, shale, South China, trace elements

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“…There are four common distributions which have been used in rock mechanics: power function distribution [40], Weibull distribution [41], normal distribution [42], and normal logarithmic distribution [43]. According to Wu et al [30], the power function distribution and Weibull distribution are chosen to model the stress-strain curves of shale samples.…”

Section: Statistical Damage Constitutive Models Of Rocks Undermentioning

confidence: 99%

“…However, expressions to define rock brittleness are various [29,30]. Considering all the proposed definitions, brittleness can be calculated by three categories: (1) stress-strain curvebased approach.…”

Section: Introductionmentioning

confidence: 99%

A Damage Constitutive Model for the Effects of CO₂-Brine-Rock Interactions on the Brittleness of a Low-Clay Shale

et al. 2018

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CO 2 is a very promising fluid for drilling and nonaqueous fracturing, especially for CO 2 -enhanced shale gas recovery. Brittleness is a very important characteristic to evaluate the drillability and fracability. However, there is not much relevant research works on the influence of CO 2 and CO 2 -based fluids on shale's brittleness been carried out. Therefore, a series of strength tests were conducted to obtain the stress-strain characteristics of shale soaked in different phases of CO 2 including subcritical or supercritical CO 2 with formation of water for different time intervals (10 days, 20 days, and 30 days). Two damage constitutive equations based on the power function distribution and Weibull distribution were established to predict the threshold stress for both intact and soaked shale samples. Based on the results, physical and chemical reactions during the imbibition cause reductions of shales' peak axial strength (20.79%~61.52%) and Young's modulus (13.14%~62.44%). Weibull distribution-based constitutive model with a damage threshold value of 0.8 has better agreement with the experiments than that of the power function distribution-based constitutive model. The energy balance method together with the Weibull distribution-based constitutive model is applied to calculate the brittleness values of samples with or without soaking. The intact shale sample has the highest BI value of 0.9961, which is in accordance with the high percentage of brittleness minerals of the shale samples. The CO 2 -NaCl-shale interactions during the imbibition decrease the brittleness values. Among the three soaking durations, the minimum brittleness values occur on samples with 20 days' imbibition in subcritical and supercritical CO 2 + NaCl solutions and the reductions of which are 2.08% and 2.49%, respectively. Subcritical/supercritical CO 2 + NaCl imbibition has higher effect on shale's strength and Young's modulus than on the brittleness. The low-clay shale still keeps good fracture performance after imbibition.

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Pore characteristics differences between clay-rich and clay-poor shales of the Lower Cambrian Niutitang Formation in the Northern Guizhou area, and insights into shale gas storage mechanisms

Cited by 78 publications

References 46 publications

Characteristics and controlling factors of pore structure of the Permian shale in southern Anhui province, East China

Characteristics and controlling factors of pore structure of the Permian shale in southern Anhui province, East China

Mineralogy and geochemical investigation of Cambrian and Ordovician–Silurian shales in South China: Implication for potential environment pollutions

A Damage Constitutive Model for the Effects of CO₂-Brine-Rock Interactions on the Brittleness of a Low-Clay Shale

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Pore characteristics differences between clay-rich and clay-poor shales of the Lower Cambrian Niutitang Formation in the Northern Guizhou area, and insights into shale gas storage mechanisms

Cited by 78 publications

References 46 publications

Characteristics and controlling factors of pore structure of the Permian shale in southern Anhui province, East China

Characteristics and controlling factors of pore structure of the Permian shale in southern Anhui province, East China

Mineralogy and geochemical investigation of Cambrian and Ordovician–Silurian shales in South China: Implication for potential environment pollutions

A Damage Constitutive Model for the Effects of CO2-Brine-Rock Interactions on the Brittleness of a Low-Clay Shale

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A Damage Constitutive Model for the Effects of CO₂-Brine-Rock Interactions on the Brittleness of a Low-Clay Shale