Gas storage and controlling factors in an over-mature marine shale: A case study of the Lower Cambrian Lujiaping shale in the Dabashan arc-like thrust–fold belt, southwestern China

Han, Hwataik; Zhong, Ningning; Ma, Yong; Huang, Caixia; Wang, Qi; Chen, Shijia; Lu, Jungang

doi:10.1016/j.jngse.2016.06.027

Cited by 46 publications

(33 citation statements)

References 51 publications

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“…OM pores are intraP pores that are found within OM, which are the most important storage space for shale gas, especially in over maturation marine shales in South China [10,32,62,72]. Organic matter pores in the LM shales can be commonly found on FE-SEM images ( Figure 5).…”

Section: Organic Matter Poresmentioning

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: Organic Matter Poresmentioning

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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“…The effects of in situ temperature and reservoir pressure on the adsorption capacity were also significant. Adsorption capacity decreasing with increasing temperature, while the opposite effect was the case with reservoir pressure (Han et al, 2016;Rexer et al, 2013). Free gas content is mainly controlled by in situ temperature and reservoir pressure, water saturation, and matrix porosity, and shows positive correlations with reservoir pressure and matrix porosity, while negative correlations are observed with temperature and water saturation .…”

Section: Introductionmentioning

confidence: 89%

“…Effects of mineral components on adsorption capacity. Previous studies have shown that minerals have significant impacts on the adsorption capacity (Han et al, 2016;Ji et al, 2015;Zhang et al, 2014). Clay and quartz minerals are the main mineral components in marine-terrigenous shale, with respective average values of 54.3% and 36.9%.…”

Section: Analysis Of Influencing Factors On Adsorption Capacitymentioning

confidence: 99%

Geological models and controlling factors of gas content in marine–terrigenous shale in the Southern Qinshui Basin, China

Hou

Zhu

Jiang

et al. 2018

Energy Exploration & Exploitation

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Geological prediction models for gas content in marine-terrigenous shale under the effects of reservoir characteristics and in situ geological conditions, were established using methane isothermal adsorption, high temperature/pressure methane isothermal adsorption, total organic carbon, X-ray diffraction, mercury porosimetry, porosity in net confining stress, and field desorption methods. Results indicated that the adsorption capacity of marine-terrigenous shale has a linearly positive correlation with total organic carbon content and maturity. Clay and quartz minerals are the two main components of inorganic minerals in marine-terrigenous shale, with an average content of 54.3% and 36.9%, respectively. Adsorption capacity of marine-terrigenous shale is slightly positive correlated with clay content, while it exponentially decreases with increasing quartz content. The effects of in situ temperature and reservoir pressure on adsorption capacity in marine-terrigenous shale are also significant. The adsorption capacity of marineterrigenous shale shows a clear decreasing trend as temperature increases, while it increases with increasing reservoir pressure. The porosity of marine-terrigenous shale is characterized by highly stress-sensitive, decreasing exponentially with increasing effective stress, which results in a more complex occurrence of free gas in deep shale reservoirs. In addition, gas saturation for the shale samples was calculated based on the results of field desorption, after which geological prediction models of total gas, adsorbed gas, and free gas were established while considering the coupled

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“…Organic-rich shale currently produces commercial unconventional hydrocarbons and exhibits a wide variation in nano-and microscale geological attributes and geochemical properties [1][2][3][4][5]. The lower Cambrian Lujiaping Formation marine, organic-rich shales in the Dabashan Thrust-fold Belt of South China are being studied for their potential as shale gas reservoirs [6][7][8][9][10]. Several studies have discussed structural style and conditions of shale gas enrichment [6,10], while other studies have characterized microstructures and associated reservoir quality [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…The lower Cambrian Lujiaping Formation marine, organic-rich shales in the Dabashan Thrust-fold Belt of South China are being studied for their potential as shale gas reservoirs [6][7][8][9][10]. Several studies have discussed structural style and conditions of shale gas enrichment [6,10], while other studies have characterized microstructures and associated reservoir quality [7][8][9]. Such investigations concentrate on nano-to microscale pore systems in the Lujiaping Shale using high-pressure methane sorption analysis, mercury injection capillary pressure (MICP), low-pressure nitrogen adsorption (LPNA), low-field nuclear magnetic resonance (NMR), and focused ion beam-scanning electron microscope imaging (FIB-SEM).…”

Section: Introductionmentioning

confidence: 99%

Tectonic and Thermal Controls on the Nano-Micro Structural Characteristic in a Cambrian Organic-Rich Shale

Zhu

Huang

et al. 2019

Minerals

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Until recently, the characteristics of nano-microscale structures in the naturally deformed, overmature, marine shales were poorly known. Thermally overmature Lujiaping shales in the complex tectonic area of the northeast part of the upper Yangtze area, China have experienced strong tectonic deformation and are considered as potentially important strata for shale gas exploration. Naturally deformed samples from the main source rocks are selected from the Lower Cambrian Lujiaping Formation in the Dabashan Thrust-fold Belt to investigate nanometer- to micrometer-sized structures. A combination of scanning electron microscope (SEM), low-pressure nitrogen adsorption (LPNA), and low-field nuclear magnetic resonance (NMR) suggests that the pore types are dominantly fracture-related pores with a lesser abundance of mineral-hosted pores. These two pore types account for the 90% of total pore space. Organic matter (OM)-hosted pores are rare and make up a small part of the pore systems (less than 10%) due to high thermal maturity and intensive tectonic compression. Overall, the Lujiaping deformed, overmature samples have abundant nanometer- to micrometer-sized inorganic pores. High-resolution SEM images provide direct evidence of the formation of nano- and microsized structures such as OM–clay aggregates and silica nanograins. OM–clay aggregates are commonly observed in samples, which also exhibit abundant open microfractures and interparticle pores. Quartz can occur as silica nanograins and botryoids typically 20–100 nm in size, which may influence porosity through the creation or occupying interparticle pore space.

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Gas storage and controlling factors in an over-mature marine shale: A case study of the Lower Cambrian Lujiaping shale in the Dabashan arc-like thrust–fold belt, southwestern China

Cited by 46 publications

References 51 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 models and controlling factors of gas content in marine–terrigenous shale in the Southern Qinshui Basin, China

Tectonic and Thermal Controls on the Nano-Micro Structural Characteristic in a Cambrian Organic-Rich Shale

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