Determining Nuclear Magnetic Resonance Surface Relaxivity of Shales

Cheng, Jiuhui; Xia, Xuanzhe; Wang, Linlin

doi:10.1021/acs.energyfuels.2c04116

Cited by 6 publications

(3 citation statements)

References 48 publications

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“…Previous studies have reported a variety of methods for determining surface relaxivity. ,, For example, the surface relaxivity is determined based on the relationship between the inverse cumulative curve of mercury saturation obtained by MIP and the inverse cumulative curve of T 2 proportion. , However, the pore size of the macropore obtained by MIP is often nonlinear with respect to the T 2 value, , which may be due to the significant pore shielding effect as a result of the large difference between the macropore and the pore throat. Therefore, for some samples, it may be more appropriate to fit the surface relaxivity by the MIP data in the small pore range. , …”

Section: Methodsmentioning

confidence: 99%

Analysis of Stress Sensitivity and Movable Fluid Characteristics of Tight Sandstone Based on NMR and Permeability Experiments

Jiang,

Zhu,

et al. 2023

Energy Fuels

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The movable fluid porosity can be used as a sensitivity factor to reflect the seepage capacity of tight reservoirs. However, the stress sensitivity and compressibility of samples differ and it is worth investigating whether the movable fluid porosity reflects the relative magnitude of the overburden permeability of the sample. In this study, the static pore information on three tight sandstones was characterized based on low-temperature nitrogen adsorption (LTNA), mercury intrusion porosimetry (MIP), and nuclear magnetic resonance (NMR) experiments. The stress sensitivity, compressibility, and movable fluid porosity of the samples at different pressures were discussed based on NMR, centrifugation, and permeability tests. The results show that the pore information on the nanopores of the samples obtained from LTNA, MIP, and NMR was consistent. Moreover, the NMR results reflected more submicron and micron pores in the samples compared to the MIP results that were affected by pore connectivity. The permeability was more sensitive to pressure than the porosity, and a small change in porosity was sufficient to cause a rapid decrease in permeability. The stress sensitivity and compressibility of nanopores were smaller than those of submicron and micron pores. The relative magnitude of stress sensitivity of micron pores and submicron pores varied from sample to sample. The variable compressibility coefficients of the samples decreased with increasing pressure (<12 MPa). The increase in the compressibility coefficients of nanopores and submicron pores for the samples at 12−15 MPa may result from the increase in the compressible space due to the transformation of the micron pores. The initial movable fluid porosity of the samples was positively correlated with the air permeability. The movable fluid porosity under pressure conditions (1−15 MPa) cannot reflect the relative magnitude of the overburden permeability, resulting from the difference in stress sensitivity between the porosity and permeability.

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Section: Methodsmentioning

confidence: 99%

Analysis of Stress Sensitivity and Movable Fluid Characteristics of Tight Sandstone Based on NMR and Permeability Experiments

Jiang,

Zhu,

et al. 2023

Energy Fuels

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“…At present, there are many methods used to characterize the pore microstructure of coalbed methane reservoirs, and there are three main types: The first is the non-material contact method, such as X-ray diffraction (XRD) [16] and nuclear magnetic resonance (NMR) [17], in which X-ray diffraction is used to determine the mineral structure of coal seams and the analysis of coal phase composition [16]. Although nuclear magnetic resonance technology can quickly and non-destructively determine the pore structure of coal and rock, its microscopic morphology cannot be intuitively observed [18,19].…”

Section: Introductionmentioning

confidence: 99%

Research on the Multiscale Microscopic Pore Structure of a Coalbed Methane Reservoir

Lu,

Liu,

Zhou

et al. 2024

Energies

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Coal rock pores are the space in which coalbed gas is stored and flows. Accurately characterizing the pore structure of coalbed gas is the foundation of coalbed gas reserve assessment and production forecasting. Traditional experimental methods are unable to characterize the multi-scale pore structure characteristics of coal rock. In this paper, a multi-scale pore structure characterization method is proposed by coupling various experimental methods, including low-pressure nitrogen gas adsorption experiments, X-ray computed tomography (XCT) imaging technology, and scanning electron microscopy (SEM). Using Zhengzhuang coalbed gas as an example, the micro-pore structure of coalbed gas reservoirs is characterized and depicted from a multi-scale perspective. The results indicate that a single experimental approach can only partially reveal the microstructure of coal rock pores. The combined use of multiple methods can accurately reveal the full-scale microstructure of coal rock pores. The pore structure of the experimental coal rock samples exhibits multi-scale characteristics, with a complex variety of pore types, including inorganic pores, organic pores, and fractures. Organic pores are predominant, with a small number of inorganic pores, and their sizes range from 2 nm to 50 μm. Mineral particles and fractures are observed at both the nanoscale and microscale, exhibiting typical multi-scale characteristics, with quartz being the predominant mineral.

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“…The advantage of this method is that the relative magnitude of the surface relaxivity of the samples can be conveniently obtained by using basic physical parameters. Besides, the digital petrophysics method, experimental parameter method, and diffusion method have also been used to determine the surface relaxivity. − …”

Section: Introductionmentioning

confidence: 99%

Applicability of Nuclear Magnetic Resonance Experiment in Analyzing Pore and Fluid Distribution Characteristics of Tight Sandstone: A Case Study in the Julu Area, Bohai Bay Basin, China

Jiang,

Zhu,

et al. 2023

ACS Omega

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Characterizing the pore and fluid distribution is critical for evaluating the reservoir potential of new areas. Nuclear magnetic resonance (NMR) is considered as an experimental method capable of full-scale characterization of pore characteristics. However, the T 2 spectrum of a saturated sample is affected by a combination of sample and experimental parameters, and it is important to confirm whether the T 2 spectrum fully reflects the sample pore information. Eight tight sandstone samples from the Julu area were selected for thin section identification, mercury intrusion porosimetry (MIP), NMR, NMR cryoporometry (NMRC), and centrifugation experiments to critically analyze the applicability of the NMR results. Two methods, the similarity method and Kozeny’s equation method, were used to calculate surface relaxivity, a critical parameter for converting NMR T 2 signals into pore information. The discussion focuses on the applicability of the calculated surface relaxivity and the phenomenon of T 2 signal changes in a short relaxation range after centrifugation. The main results are as follows: The surface relaxivity values calculated using the different methods differed significantly. The surface relaxivity calculated using the same method reflected the relative magnitude of the true surface relaxivity of the samples. For the samples with large surface relaxivity, there may be partial misses of the short relaxation signal, the NMR porosity was smaller than the gas-measured porosity, there was a variation in the T 2 spectrum in the short relaxation range after centrifugation, and the calculated surface relaxivity was small. The surface relaxivity calculated using Kozeny’s equation was nearly accurate, but perhaps smaller than the true value. The T 2 spectra mainly reflected macropore information. This study suggests that PSDs converted from T 2 spectra of saturated samples should be judged with relative caution rather than solely based on the peak or range correspondence between the two curves, and the minimum centrifugal radius can be used as a constraint.

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Determining Nuclear Magnetic Resonance Surface Relaxivity of Shales

Cited by 6 publications

References 48 publications

Analysis of Stress Sensitivity and Movable Fluid Characteristics of Tight Sandstone Based on NMR and Permeability Experiments

Analysis of Stress Sensitivity and Movable Fluid Characteristics of Tight Sandstone Based on NMR and Permeability Experiments

Research on the Multiscale Microscopic Pore Structure of a Coalbed Methane Reservoir

Applicability of Nuclear Magnetic Resonance Experiment in Analyzing Pore and Fluid Distribution Characteristics of Tight Sandstone: A Case Study in the Julu Area, Bohai Bay Basin, China

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