Nanoscale mechanical property variations concerning mineral composition and contact of marine shale

Li, Yong; Chen, Jianqi; Elsworth, D.; Pan, Zhejun; Ma, Xiaotian

doi:10.1016/j.gsf.2022.101405

Cited by 50 publications

(42 citation statements)

References 55 publications

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“…In addition to conventional reservoir pore research methods, theoretical methods of porous material characterization are also introduced to pore characteristics of shale, which can be roughly summarized as image analysis, fluid injection method, and nonfluid injection method [25][26][27][28][29]. Image analysis techniques such as scanning electron microscopy [25,30], field emission scanning electron microscopy [31,32], focused ion beam scanning electron microscopy [33], transmission electron microscopy, and atomic force microscopy can be used to intuitively observe and analyse the morphology and size of microscopic pores in shale [30][31][32][33][34][35].…”

Section: Geofluidsmentioning

confidence: 99%

The Pore Structure of Marine to Continental Transitional Shales in the Permian Shanxi Formation on the East Margin of the Ordos Basin, China

Wang

Tian²,

Deng

et al. 2022

Geofluids

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The pore structure is an important factor in determining the storage capacity for shale gas development. Twelve samples were selected from the marine to continental transitional shales in the Shanxi Formations on the eastern margin of the Ordos Basin, and their nanoscale pore structure was investigated by a variety of low-temperature N2 adsorption (LT-N2GA) and low-pressure CO2 adsorption (LP-CO2GA) and high-pressure mercury intrusion (HPMI) experiments. The shale pores are complex and are mainly mesopores, which range mainly from 10 nm to 40 nm and greatly contribute to the pore volume (PV), whereas pores with a diameter less than 0.8 nm greatly contribute to the specific surface area (SSA) of the shale. The pore structure is affected by the TOC content, organic matter maturity, and illite/smectite (I/S) mixed layer content. The total PV increases with the increase in TOC content, organic matter maturity, and I/S mixed layer content. The effects of pores on the occurrence shale gas were determined by high-pressure methane adsorption experiments. The maximum adsorption amount of methane was positively correlated with the SSA of the micropores, indicating that the micropores have a large SSA, which controlled the adsorbed gas content of the shale. The mesopores provide the majority of the PV, which mainly corresponds to the volume of free gas in the shale, and the macropores are mainly micron-sized pores, which can form the main migration channels for shale gas.

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Section: Geofluidsmentioning

confidence: 99%

The Pore Structure of Marine to Continental Transitional Shales in the Permian Shanxi Formation on the East Margin of the Ordos Basin, China

Wang

Tian²,

Deng

et al. 2022

Geofluids

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show abstract

“…It is favored by countries worldwide for its clean and efficient characteristics, wide distribution, and large reserves, which are considered major strategic resource reserves [5][6][7]. Nevertheless, the small pores (nanoscale pores) and low permeability of shale gas reservoirs have led to low shale gas recovery and extraction efficiency [8][9][10][11]. Additionally, due to the apparent tectonic stress activity in multiple phases, the spatial distribution of mineral components is anisotropic and inhomogeneous.…”

Section: Introductionmentioning

confidence: 99%

Fracture Propagation Modes of Lower Cambrian Shale Filled with Different Quartz Contents under Seepage-Stress Coupling

Wang

Chen

et al. 2022

Geofluids

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The content and spatial distribution of brittle minerals, such as quartz, are important factors in determining the fracture initiation mechanism induced by hydraulic fracturing in shale reservoirs. To further research the impact of quartz content in shales of the Lower Cambrian Niutitang Formation in northern Guizhou on the fracture expansion of its reservoir, 7 groups of randomly filling shale models with different quartz contents were established using rock failure process analysis (RFPA2D-flow) code for numerical test studies under seepage-stress coupling, and 5 samples were also subjected to uniaxial compression tests using the INSTRON 1346 electrohydraulic servo-controlled material testing machine (200T). The results show that the average growth rate of the compressive strength and the fracture proportion for a quartz content of 50% to 65% are 4.22 and 1.15 times higher than those for 35% to 50%, respectively. Fractures sprout, expand, and breakdown in the shale matrix or at the junctions of the shale matrix and quartz grains. The mechanical properties and pattern of the fracture extension of the shale in the physical tests are similar to those in the numerical tests, indicating the reliability of the numerical simulations. The fractal dimension curves at different stress levels are divided into three stages: flattening, increasing, and surging, and the fractal dimension value for a quartz content of 50%~65% at a 100% stress level is 1.02 times higher than that for 35%~50%. The high degree of natural fracture development in high quartz content formations in shale gas reservoirs is of some reference value for logging data. The research results provide a reference value for the content and spatial distribution of brittle minerals for the initiation mechanism and fracture propagation of hydraulic fracturing in shale reservoirs.

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“…As the largest superimposed basin in China, Ordos Basin has long been considered a multi-energy basin with abundant fossil energy and mineral resources. A set of upper Paleozoic coalbearing shales in the southeast Ordos Basin is widely considered a potential area for shale gas exploration and development (Li et al, 2022b;Zhang et al, 2022). The coal-bearing shale gas resources of the Shanxi-Taiyuan Formation are in the range of 2800-3200*10 8 m 3 in the Daning-Jixian block, southeastern Ordos Basin (Zeng et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Microstructure and heterogeneity of coal-bearing organic shale in the southeast Ordos Basin, China: Implications for shale gas storage

Wang²,

Liu³

et al. 2022

Front. Earth Sci.

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In recent years, the eastern margin of Ordos Basin has attracted much attention as a key base for unconventional natural gas exploration. The pore-fracture structure is an important physical property of shale and provides places and channels for methane storage and migration. In this study, an integrated method of X-ray diffraction, total organic carbon (TOC), vitrinite reflectance (Ro), scanning electron microscopy (SEM), and low-temperature N2 adsorption was performed to reveal the microstructure and heterogeneity of coal-bearing organic shale in the southeast Ordos Basin. The result indicated that the studied shale belongs to the category of organic-rich shale with an average TOC content of 8.1% and reaches the dry gas stage with a mean Ro value of 2.41%. Hysteresis loop suggests the shapes of pore structure in shale samples are dominated by inkbottle, cylindrical pores or parallel-plate. A positive correlation between kaolinite and pore surface area indicates that kaolinite contributes greatly to micropores with a large specific surface area. Intense hydrocarbon generation promotes gas to escape from organic components’ surfaces, thereby increasing the pore volume. Coal-bearing shales with high brittleness may contain more natural microfractures, increasing specific surface area and pore volume. The bocking effect of minerals in microfractures may reduce pore connectivity and connectivity and enhance shale heterogeneity. The pore volume and specific surface area of coal-bearing shale are closely related to the fractal dimensions. The high complexity of the shale microstructure may lead to the formation of more micropores, resulting in a decrease in the average pore size. Besides, organic and clay-hosted pores in coal-bearing shale with high maturity may well be the main storage space for methane, but the methane is mainly stored in organic pores in marine shale.

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Nanoscale mechanical property variations concerning mineral composition and contact of marine shale

Cited by 50 publications

References 55 publications

The Pore Structure of Marine to Continental Transitional Shales in the Permian Shanxi Formation on the East Margin of the Ordos Basin, China

The Pore Structure of Marine to Continental Transitional Shales in the Permian Shanxi Formation on the East Margin of the Ordos Basin, China

Fracture Propagation Modes of Lower Cambrian Shale Filled with Different Quartz Contents under Seepage-Stress Coupling

Microstructure and heterogeneity of coal-bearing organic shale in the southeast Ordos Basin, China: Implications for shale gas storage

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