Application of Low-Field Nuclear Magnetic Resonance (LFNMR) in Characterizing Coal Pores and Permeability

Low-field nuclear magnetic resonance (LFNMR) is a rapid, nondestructive analytical method which has been proved to be attractive for its application in brittle and easily compressed coals. In this paper, the relationships between NMR parameters and coal pores were analyzed by the NMR measurements of six coal samples with different ranks using AniMR with the resonance frequency of 12.15MHz. Results show that NMR porosity usually compare well to water porosity and be lower than He porosity, and the NMR porosity at echo spacing of 0.3ms sometimes underestimates the coal sample, lower than water porosity by >1 porosity unit. In contrast, the NMR porosity at echo spacing of 0.1ms is acceptable for characterization of coal reservoir. The difference of NMR porosity at different echo spacing may relate to the vitrinite content. Based on the T2c model, the transverse surface relaxivity of coal is calculated and it ranges from 0.25 to 20 um/s, commonly lower than 5um/s. The producible porosity could be a parameter used to estimate coal permeability, however there still needs a lot of work to construct a perfect method for this.

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Synthetical study on the difference and reason for the pore structure of the No. 3 coal reservoir from the southern Qinshui Basin, China, using mercury intrusion porosimetry, low-temperature N2 adsorption, low field nuclear magnetic resonance, and nuclear magnetic resonance cryoporometry

Energy Reports ◽

10.1016/j.egyr.2020.07.011 ◽

2020 ◽

Vol 6 ◽

pp. 1876-1887 ◽

Cited By ~ 1

Author(s):

Huihu Liu ◽

Ibrahim Issa Farid ◽

Shuxun Sang ◽

Jianhua Shang ◽

Haiyan Wu ◽

...

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Mercury Intrusion Porosimetry ◽

N2 Adsorption ◽

Mercury Intrusion ◽

Low Field ◽

Southern Qinshui Basin ◽

The Difference ◽

Coal Reservoir ◽

Nuclear Magnetic

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High-resolution characterization of nanoparticle transport in heterogeneous porous media via low-field nuclear magnetic resonance

Journal of Hydrology ◽

10.1016/j.jhydrol.2020.124558 ◽

2020 ◽

Vol 583 ◽

pp. 124558

Author(s):

Qian Zhang ◽

Yanhui Dong ◽

Hang Deng ◽

Derek Elsworth

Keyword(s):

Nuclear Magnetic Resonance ◽

Porous Media ◽

Magnetic Resonance ◽

High Resolution ◽

Heterogeneous Porous Media ◽

Nanoparticle Transport ◽

Low Field ◽

Nuclear Magnetic

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Petrophysical characterization of high-rank coal by nuclear magnetic resonance: a case study of the Baijiao coal reservoir, SW China

Royal Society Open Science ◽

10.1098/rsos.181411 ◽

2018 ◽

Vol 5 (12) ◽

pp. 181411 ◽

Cited By ~ 3

Author(s):

Dongming Zhang ◽

Yapei Chu ◽

Shujian Li ◽

Yushun Yang ◽

Xin Bai ◽

...

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Coalbed Methane ◽

High Rank ◽

Free Fluid ◽

Permeability Model ◽

Cutoff Value ◽

Coal Reservoir ◽

Nuclear Magnetic

To better apply nuclear magnetic resonance (NMR) to evaluate the petrophysical characterization of high-rank coal, six anthracite samples from the Baijiao coal reservoir were measured by NMR. The porosity, T 2 cutoff value, permeability and pore type were analysed using the transverse relaxation time ( T 2 ) spectrum before and after centrifugation. The results show that the T 2 spectrum of water-saturated anthracite can be divided into a discontinuous and continuous trimodal distribution. According to the connectivity among pores, three T 2 spectrum peaks were identified at the relaxation times of 0.01–1.7 ms, 1.7–65 ms and greater than 65 ms, which correspond to the micropores (less than 100 nm), mesopores (100–1000 nm) and macropores (greater than 1000 nm), respectively. Based on the T 2 cutoff value, we divided the T 2 spectrum into two parts: bound fluid and free fluid. By comparing two classic permeability models, we proposed a permeability model to calculate the permeability of anthracite. This result demonstrates that NMR has great significance to the exploration of coal reservoirs and to the understanding of the development of coalbed methane.

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Characterization of moisture in acetylated and propionylated radiata pine using low-field nuclear magnetic resonance (LFNMR) relaxometry

Holzforschung ◽

10.1515/hf-2017-0072 ◽

2018 ◽

Vol 72 (3) ◽

pp. 225-233 ◽

Cited By ~ 19

Author(s):

Greeley Beck ◽

Emil Engelund Thybring ◽

Lisbeth Garbrecht Thygesen ◽

Callum Hill

Keyword(s):

Nuclear Magnetic Resonance ◽

Cell Wall ◽

Magnetic Resonance ◽

Relaxation Times ◽

Radiata Pine ◽

Saturation Point ◽

Weight Percentage ◽

Low Field ◽

Nuclear Magnetic

AbstractMoisture in radiata pine (Pinus radiataD. Don) earlywood (EW), which was acetylated or propionylated to various degrees, was measured by low-field nuclear magnetic resonance (LFNMR) relaxometry. Spin-spin relaxation times (T2) were determined for fully saturated samples at 22 and −18°C.T2values for EW lumen water increased with increasing acetylation weight percentage gain (WPG), perhaps caused by the less hydrophilic acetylated wood (AcW) surface. Cell wall water (WCW) and the water in pits and small voids also showed increasingT2values as a function of WPG but with a weaker tendency. A possible explanation is the counteracting effects of decreased hydrophilicity and reduced moisture content (MC) of these water populations at higher levels of acetylation. The evaluation of propionylation on WCWT2data was complicated by peak splitting in the relaxation spectrum. ConstantT2values for void water populations at various WPG levels for propionylated samples indicate a modification gradient in the cell wall. Fiber saturation point (FSP) was significantly reduced by both modifications. Slightly higher FSP values for propionylated samples suggest that physical bulking is not the only factor causing moisture exclusion in AcW. But this interpretation is tentative because of the possibility of cell wall damage caused by propionylation.

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