Characterization of the Pore Structure and Fluid Movability of Coal-Measure Sedimentary Rocks by Nuclear Magnetic Resonance (NMR)

Zhang, Na; Wang, Shuaidong; Zhao, Fangfang; Sun, Xiaoming; He, Manchao

doi:10.1021/acsomega.1c03247

Cited by 7 publications

(8 citation statements)

References 29 publications

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“…This technique was widely used in the evaluation of various petroleum reservoirs, such as clastic rocks, carbonate rocks, and volcanic rocks, for nearly five decades [11,[22][23][24][25]. In recent years, it has become an indispensable tool for characterizing reservoir properties, such as PSD, porosity, permeability, wettability, fluid movability, and saturation, due to the nondestructive feature, convenience in sample processing, and short test time [6,[26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Pore Size Distribution Characterization by Joint Interpretation of MICP and NMR: A Case Study of Chang 7 Tight Sandstone in the Ordos Basin

Liu

You

et al. 2022

Processes

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Pore size distribution characterization of unconventional tight reservoirs is extremely significant for an optimized extraction of petroleum from such reservoirs. In the present study, mercury injection capillary pressure (MICP) and low-field nuclear magnetic resonance (NMR) are integrated to evaluate the pore size distribution of the Chang 7 tight sandstone reservoir. The results show that the Chang 7 tight sandstones are characterized by high clay mineral content and fine grain size. They feature complex micro-nano-pore network system, mainly composed of regular primary intergranular pores, dissolved pores, inter-crystalline pores, and micro-fractures. Compared to the porosity obtained from MICP, the NMR porosity is closer to the gas-measured porosity (core analysis), and thus can more accurately describe the total pore space of the tight sandstone reservoirs. The pore throat distribution (PTD) from MICP presents a centralized distribution with high amplitude, while the pore size distribution (PSD) derived from NMR shows a unimodal distribution or bimodal distribution with low amplitude. It is notable that the difference between the PSD and the PTD is always related to the pore network composed of large pores connecting with narrow throats. The PSD always coincides very well with the PTD in the very tight non-reservoirs with a much lower porosity and permeability, probably due to the pore geometry that is dominated by the cylindrical pores. However, a significant inconsistency between the PSD and PTD in tight reservoirs of relatively high porosity and low permeability is usually associated with the pore network that is dominated by the sphere-cylindrical pores. Additionally, Euclidean distance between PSD and PTD shows a good positive correlation with pore throat ratio (PTR), further indicating that the greater difference of pore bodies and pore throats, the more obvious differentiation of two distributions. In summary, the MICP and NMR techniques imply the different profiles of pore structure, which has an important implication for deep insight into pore structure and accurate evaluation of petrophysical properties in the tight sandstone reservoir.

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Section: Introductionmentioning

confidence: 99%

Pore Size Distribution Characterization by Joint Interpretation of MICP and NMR: A Case Study of Chang 7 Tight Sandstone in the Ordos Basin

Liu

You

et al. 2022

Processes

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“…Liu et al 24 aiming at the uncertainty of fractured rock mass structural plane, established a multivariable analysis system for fractured rock mass structural plane based on manifold learning and fractal theory, and proposed the analysis process of single fractal and multifractal. Zhang et al 25 conducted experimental studies on 13 typical coal measure sedimentary rocks by using NMR, and realized the application of multifractal in fluid mobility of coal measure sedimentary rocks based on fractal theory. Xi et al 26 used FE-SEM and NMR to analyze the formation and propagation of cracks in granite after cold and heat treatment, and established a theoretical model of rock damage evolution based on fractal theory.…”

Section: Acoustic Emission and Fractal Characteristics Of Red Beds So...mentioning

confidence: 99%

Acoustic emission and fractal characteristics of red beds soft rock under water-force coupling

Chen,

Liu,

Jia

et al. 2023

Preprint

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Groundwater has significant influence on the mechanical properties of surrounding rock. Aiming at the large deformation of surrounding rock of red layer soft rock tunnel affected by groundwater, the uniaxial graded loading tests were carried out on red beds soft rock with different water content. The failure process of the specimen was monitored by acoustic emission (AE) and the crack evolution law was analyzed, and the scanning electron microscopy (SEM) was used to compare the microstructure of the specimens before and after immersion. Combined with fractal theory, the monofractal and multifractal characteristics of AE ringing count during the loading process of red layer soft rock were analyzed. The results show that, with the gradual increase of water content, the AE ringing count before the yield stage gradually decreased, and the corresponding cumulative ringing count at the same time gradually decreased, and the decrease was large in the early stage of immersion, and decreased in the later stage. The cumulative ringing curve gradually slowed down, the internal crack appeared earlier, the cumulative ringing curve stepped significantly, the AE signal amplitude gradually weakened, and the bandwidth of each frequency band gradually decreased. The failure of red beds soft rock with different water content is dominated by shear crack, and with the gradual increase of water content, the proportion of shear crack increases gradually, and the AE b value decreases gradually. With the gradual increase of the relative peak strength, the correlation dimension D of red beds soft rock with different water content increases first and then decreases. At 80% of the relative peak strength, the correlation dimension D reaches its maximum value and then drops sharply until it is maintained at a relatively low level, and the correlation dimension D gradually decreases with the water content. The fitting correlation coefficients of different water content (lnC(r), lnr) are all above 0.9, indicating that the AE ringing count of water-bearing red beds soft rock has fractal characteristics, and the higher the correlation coefficient, the higher the self-similarity of AE ringing count sequence. As the weight q gradually increases, the generalized fractal dimension D(q) gradually decreases. When q≠0, under the condition of the same q, D(q) presents a trend of first increasing and then decreasing. The multifractal characteristics of AE ringing count of red layer soft rock with different water content is inverted ‘U’ shape. From the natural state to immerse 1d, the ∆α gradually increases, and from 1d to 7d, the ∆α gradually decreases. When saturation is not reached, ∆f < 0 indicates that the number of cracks in the specimen is small, when saturation is reached, ∆f > 0 indicates that a large number of cracks are generated inside the specimen and macro cracks are formed. This research can provide a reliable theoretical basis for the construction and maintenance of large deformation of water-rich soft rock tunnel excavation, and have certain engineering significance.

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“…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.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2023

Self Cite

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Analyzing and mastering the fractal features of coal-measure sedimentary rocks is crucial for accurately describing the pore structure of coalbed methane resources. In this work, mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR) are performed on coal-measure sedimentary rocks (i.e., shale, mudstone, and sandstone) to analyze their pore structure. Pore size distributions (PSDs) and the multifractal dimensions of the investigated samples are discussed. Moreover, multivariable linear regression models of multifractal dimensions are established through a comprehensive analysis of multifractal characteristics. The results show that sandstone (SS-1) and clay rocks are dominated by nanopores of 0.01 to 1μm, while sandstone (SS-2) is mostly mesopores and macropores in the range of 1 to 10μm. The fractal characteristics of the investigated rock samples show a prominent multifractal characteristic, in which DA reflects the surface structure of micropores, while DS represents the pore structure of macropores. Multifractal dimension is affected by many factors, in which the DA is greatly influenced by the pore surface features and mineral components and the DS by average pore diameters. Moreover, multivariate linear regression models of adsorption pore and seepage pore are established, which have a better correlation effect on the multifractal dimension.

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Characterization of the Pore Structure and Fluid Movability of Coal-Measure Sedimentary Rocks by Nuclear Magnetic Resonance (NMR)

Cited by 7 publications

References 29 publications

Pore Size Distribution Characterization by Joint Interpretation of MICP and NMR: A Case Study of Chang 7 Tight Sandstone in the Ordos Basin

Pore Size Distribution Characterization by Joint Interpretation of MICP and NMR: A Case Study of Chang 7 Tight Sandstone in the Ordos Basin

Acoustic emission and fractal characteristics of red beds soft rock under water-force coupling

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

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