A preliminary study on the characterization and controlling factors of porosity and pore structure of the Permian shales in Lower Yangtze region, Eastern China

Pan, Lei; Xiao, Xia; Tian, Hui; Zhou, Qinling; Ji, Chen; Li, Tengfei; Wei, Qiang

doi:10.1016/j.coal.2015.05.005

Cited by 111 publications

(84 citation statements)

References 41 publications

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“…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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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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“…As a clean and efficient energy source, shale gas has become an increasingly significant resource worldwide [2][3][4][5][6]. The exploration and exploitation of shale gas has accelerated in recent years, with significant progress made in the Sichuan Basin of Southern China [7,8].…”

Section: Introductionmentioning

confidence: 99%

Vertical Heterogeneity of the Shale Reservoir in the Lower Silurian Longmaxi Formation: Analogy between the Southeastern and Northeastern Sichuan Basin, SW China

et al. 2017

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Lower Silurian Longmaxi formation (LSL) shale is widely and continuously distributed in the northeastern Sichuan Basin and, based on structural analogies with the gas producing LSL formation in the southeastern Sichuan Basin, has significant potential for shale gas exploration. However, limited research has been performed to evaluate the shale gas potential in this region. Samples from a recently completed exploratory well (Well-WQ2) in the northeastern Sichuan Basin indicate that the LSL shale has a vertical property sequence that closely resembles the vertical property sequences in wells in the gas-producing sections of the southeastern Sichuan Basin. The continuous sampling and analyses of Well-WQ2 have allowed a detailed investigation of the vertical variations in lithofacies, mineral characteristics, pore structures, and organic geochemical characteristics. The Longmaxi formation was divided into two third-order sequences (SQ1 and SQ2) based on systematic core observations and well logging analyses. Both SQ1 and SQ2 include a transgressive system tract (TST) and a high-stand system tract (HST). The lithofacies exhibit an upward decrease in the organic content. From SQ1 to SQ2, the quartz content, in situ graptolite content, total organic carbon (TOC) content, and brittleness index decrease, but the clay mineral content increases. The LSL shale sections from depths of 1204 to 1214 m and from 1271 to 1282 m possess well-developed fractures and high permeability. Additionally, the average porosity and permeability in SQ1 are higher than those in SQ2. In addition, the positive correlation between the TOC and quartz contents of the assayed samples suggests that much of the quartz is of biogenic origin. Changes in the sedimentary and diagenetic environments during deposition are two key factors that contribute to the observed vertical heterogeneity of the Longmaxi formation. In conclusion, the shale sections of the lower part of the SQ1, like their analogs in the southeastern Sichuan Basin, are the most favorable targets for shale gas production in the northeastern Sichuan Basin.

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“…Therefore, the development and evolution of organic pores becomes an important factor affecting shale porosity. According to the data from literature, shale porosity has a clear positive correlation with TOC content when TOC is within a definite range (Milliken et al 2013;Pan et al 2015;Tian et al 2013;Wang et al 2013a). However, this positive correlation will be changed or even reversed to be negative when TOC is very high, over this range (Milliken et al 2013;Pan et al 2015;Wang et al 2013a).…”

Section: Geological Characteristics Of the Lower Paleozoic Shalementioning

confidence: 99%

“…According to the data from literature, shale porosity has a clear positive correlation with TOC content when TOC is within a definite range (Milliken et al 2013;Pan et al 2015;Tian et al 2013;Wang et al 2013a). However, this positive correlation will be changed or even reversed to be negative when TOC is very high, over this range (Milliken et al 2013;Pan et al 2015;Wang et al 2013a). The TOC turning point occurs at about 5.6 % for the Marcellus Shale (Milliken et al 2013), 5.0 % for the Lower Paleozoic shale from the southern area of the Sichuan Basin (Wang et al 2013a), and 12 % for the Upper Permian shale from the Lower Yangtze region .…”

Section: Geological Characteristics Of the Lower Paleozoic Shalementioning

confidence: 99%

“…The TOC turning point occurs at about 5.6 % for the Marcellus Shale (Milliken et al 2013), 5.0 % for the Lower Paleozoic shale from the southern area of the Sichuan Basin (Wang et al 2013a), and 12 % for the Upper Permian shale from the Lower Yangtze region . This is attributed to an easier compaction of organic nano-pores for shale with a higher TOC content than shale with a lower TOC content (Milliken et al 2013;Wang et al 2013a;Pan et al 2015). Compaction not only reduces total porosity, but also changes pore structure significantly.…”

Section: Geological Characteristics Of the Lower Paleozoic Shalementioning

confidence: 99%

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Main controlling factors and enrichment area evaluation of shale gas of the Lower Paleozoic marine strata in south China

et al. 2015

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The Lower Paleozoic shale in south China has a very high maturity and experienced strong tectonic deformation. This character is quite different from the North America shale and has inhibited the shale gas evaluation and exploration in this area. The present paper reports a comprehensive investigation of maturity, reservoir properties, fluid pressure, gas content, preservation conditions, and other relevant aspects of the Lower Paleozoic shale from the Sichuan Basin and its surrounding areas. It is found that within the main maturity range (2.5 % \ EqR o \ 3.5 %) of the shale, its porosity develops well, having a positive correlation with the TOC content, and its gas content is controlled mainly by the preservation conditions related to the tectonic deformation, but shale with a super high maturity (EqR o [ 3.5 %) is considered a high risk for shale gas exploration. Taking the southern area of the Sichuan Basin and the southeastern area of Chongqing as examples of uplifted/folded and faulted/folded areas, respectively, geological models of shale gas content and loss were proposed. For the uplifted/folded area with a simple tectonic deformation, the shale system (with a depth [ 2000 m) has largely retained overpressure during uplifting without a great loss of gas, and an industrial shale gas potential is generally possible. However, for the faulted/folded area with a strong tectonic deformation, the sealing condition of the shale system was usually destroyed to a certain degree with a great loss of free gas, which decreased the pressure coefficient and resulted in a low production capacity. It is predicted that the deeply buried shale ([3000 m) has a greater gas potential and will become the focus for further exploration and development in most of the south China region (outside the Sichuan Basin).

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A preliminary study on the characterization and controlling factors of porosity and pore structure of the Permian shales in Lower Yangtze region, Eastern China

Cited by 111 publications

References 41 publications

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

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

Vertical Heterogeneity of the Shale Reservoir in the Lower Silurian Longmaxi Formation: Analogy between the Southeastern and Northeastern Sichuan Basin, SW China

Main controlling factors and enrichment area evaluation of shale gas of the Lower Paleozoic marine strata in south China

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