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

Abstract

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.

Full-Scale Pore and Microfracture Characterization of Deep Coal Reservoirs: A Case Study of the Benxi Formation Coal in the Daning–Jixian Block, China

“…There are many nanometre-scale pores and microfractures in the Benxi Formation coal samples. At present, classification schemes for coal reservoir pores have not been unified [14,20]. In this study, referring to the classification scheme proposed by Loucks et al [7], the pores in the Benxi Formation coal samples are divided into OM pores, inorganic pores, and microfractures.…”

“…Previous studies on coal pore structure have been carried out in many ways and can be divided into three categories according to experimental principles: fluid injection methods, image analysis methods, and nonfluid injection methods [14,15]. Fluid intrusion methods mainly include low-pressure CO 2 adsorption (LP-CO 2 GA), low-temperature N 2 adsorption (LT-N 2 GA), and high-pressure MIP methods [16][17][18][19][20].…”

Pore Structure and Fractal Characteristics of Coal-Measure Sedimentary Rocks Using Nuclear Magnetic Resonance (NMR) and Mercury Intrusion Porosimetry (MIP)

“…ergies 2023, 16,3812 12 of 17 increase with decreasing average pore diameters, indicating that rock samples with tiny average pore diameters may comprise more throats and micropores, resulting in increasing heterogeneity and more complex pore structures. The DS shows a better correlation with average pore diameters than DA.…”

“…According to Loucks's pore size scale [4], pores can be divided into five parts: picopore (<1 nm), nanopore (1 nm-1 µm), micropore (1 µm-62.5 µm), mesopore (62.5 µm-4 mm), and macropore (4 mm-256 mm). In recent years, a series of experimental methods, i.e., gas adsorption experiment (N 2 /CO 2 ) [5][6][7], X-ray computed tomography (CT) [8][9][10], field-emission scanning electron microscope (FE-SEM) [11][12][13][14], mercury intrusion porosimetry (MIP) [15,16], nuclear magnetic resonance (NMR) [17][18][19][20][21][22], and NMR cryoporometry (NMRC) [23], have been carried out to explore the micropore structure of common coal-measure sedimentary rocks. However, limited by the testing principles, each of the aforementioned experimental methodologies has certain restrictions.…”

Paleo-Environment Induced Full-Scale Pore Variation in the Low Matured Shale: A Case Study of the Third Member of the Jiufotang Formation at the Lujiapu Rift Basin, Northeast China

“…The dissolution of shale reservoirs by organic acids does not have an overall significance; it only occurs if organic acids move along fractures and dissolve adjacent minerals. Although dissolution pores in shales of the Wufeng Formation and the Longmaxi Formation at the Sichuan Basin are common [41], their size is too small compared to the primary interP pores. In addition, the negative correlation between TOC and Volume 1 demonstrates that organic matter had occupied some pore spaces and restrained the development of mesopores (Figure 4h).…”