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Dameng Liu - One of the best experts on this subject based on the ideXlab platform.

  • evaluation of coal petrophysics incorporating fractal characteristics by Mercury Intrusion Porosimetry and low field nmr
    Fuel, 2020
    Co-Authors: Dameng Liu, Yidong Cai, Yunpeng Wang
    Abstract:

    Abstract Mercury Intrusion Porosimetry (MIP) and low-field nuclear magnetic resonance (NMR) were combined to investigate pore-fracture structure and fractal characteristics of coals (0.93%  k N = 0.0045 ∗ e ϕ NM 0.6851 + 0.037 ), ranging from 0.043 to 2.767 mD. The NMR permeability should be related to movable fluid space and pore-fracture connectivity, and micro-fractures can largely contribute to free fluid volume.

  • pore structure and compressibility of coal matrix with elevated temperatures by Mercury Intrusion Porosimetry
    Energy Exploration & Exploitation, 2015
    Co-Authors: Dameng Liu, Yanbin Yao, Yidong Cai, Hui Wang
    Abstract:

    To gain a better understanding of the effect of heat (e.g., magma Intrusion, geothermal fluids and enhanced coal-bed methane recovery process) on coal reservoir properties, the pore structure and compressibility of coal matrix for low rank coal (0.69% Ro, m) with elevated temperatures were investigated by using multiple methods, including thermogravimetry-mass spectrometry (TG-MS), scanning electron microscope (SEM), N2 adsorption/desorption at 77 K and Mercury Intrusion Porosimetry (MIP). The results from TG-MS showed that moisture and partial volatiles were removed from the coal matrix, and pore structure almost remained unchanged during the low heat treatment (25~200℃). The micropores and transition pores consisted of more than 80% of the total pore volume based on the MIP. The pore structure was slightly changed following the temperature increase to 400℃, and the bound moisture and partial organics in the coal were released and decomposed by the increased heat, respectively. When temperature reached 4...

  • characteristics of coal matrix compressibility an investigation by Mercury Intrusion Porosimetry
    Energy & Fuels, 2014
    Co-Authors: Xiaoqian Guo, Yanbin Yao, Dameng Liu
    Abstract:

    Coal matrix compressibility caused by a pressure change is an important parameter in evaluating the permeability change during coalbed methane production. In this study, the pressure-driven coal matrix compressibility for 21 coals in the rank range from high-volatile A bituminous (0.65% Ro,m) to low-volatile bituminous (1.77% Ro,m) was evaluated by combining the results from Mercury Intrusion Porosimetry (MIP) with N2 adsorption analysis. The pressure interval was chosen to be from 7.35 MPa to ensure that the compression is totally from the coal matrix. The calculated coal matrix compressibility shows a U-shaped relationship with increasing coal rank, and it obtains relatively low values at the medium-volatile bituminous coals. The coal matrix compressibility of high-volatile A bituminous coals is of 1.6398–2.9060 × 10–4 MPa–1, and medium- and low-volatile bituminous coals have coal matrix compressibility of 0.3451–1.5519 × 10–4 and 0.7625–2.5554 × 10–4 MPa–1, respectively. Moreover, with the data of petr...

  • comparison of low field nmr and Mercury Intrusion Porosimetry in characterizing pore size distributions of coals
    Fuel, 2012
    Co-Authors: Yanbin Yao, Dameng Liu
    Abstract:

    In this study we investigated how traditional Mercury Intrusion Porosimetry (MIP), constant-rate-controlled Mercury Porosimetry (CMP), Low-field NMR spectral analysis (LFNMR), and micro focus computerized tomography (μCT) compare in revealing the pore size distribution (PSD) characteristics of coals. The comparison was made using the same source samples throughout. Two limitations of Mercury Porosimetry are addressed. First, the high-pressure Intrusion by Mercury may either deform or destroy the coal sample and eventually induce suspect value of coal porosity, thus correction of pore structure compressibility must be made in analyzing lignite or other coals that with very open structure. Second, pore shielding effects can induce high uncertainty of MIP results, in particular when clusters of smaller pores occur in isolated domains in a continuous network of larger pores. This can result in temporary Mercury entrapment during the extrusion process and result in inaccurate estimations of PSD. Another pore shielding effect is due to isolated clusters of large pores in a continuous network of smaller pores. Her Mercury is prone to be trapped permanently. This effect can induce inaccurate estimations of the total pore volume. CMP is an effective method that can provide much more detailed PSD information of macropores, however it is deficient in analyzing mesopores of coals. After comparison with the results by μCT and other traditional methods, it was found that LFNMR is an efficient tool for nondestructively quantifying the PSD of coal.

  • petrophysical characterization of coals by low field nuclear magnetic resonance nmr
    Fuel, 2010
    Co-Authors: Dameng Liu, Shuheng Tang, Dazhen Tang, Yao Che, Wenhui Huang
    Abstract:

    Nuclear magnetic resonance (NMR) has been widely used in petrophysical characterization of sandstones and carbonates, but little attention has been paid in the use of this technique to study petrophysical prop- erties of coals, which is essential for evaluating coalbed methane reservoir. In this study, two sets of NMR experiments were designed to study the pore types, pore structures, porosity and permeability of coals. Results show that NMR transverse relaxation (T2) distributions strongly relate to the coal pore structure and coal rank. Three T2 spectrum peaks identified by the relaxation time at 0.5-2.5 ms, 20-50 ms and >100 ms correspond to pores of 0.1 lm and cleats, respectively, which is consistent with results from computed tomography scan and Mercury Intrusion Porosimetry. Based on calculated pro- ducible and irreducible porosities through a T2 cutoff time method, we propose a new NMR-based per- meability model that better estimates the permeability of coals. In combination with Mercury Intrusion Porosimetry, we also propose a NMR-based pore structure model that efficiently estimates the pore size distribution of coals. The new experiments and modeling prove the applicability of NMR in petrophysical characterization of intact coal samples, which has potential applications for NMR well logging in coalbed methane exploration.

Jianchao Cai - One of the best experts on this subject based on the ideXlab platform.

Yunpeng Wang - One of the best experts on this subject based on the ideXlab platform.

Yidong Cai - One of the best experts on this subject based on the ideXlab platform.

  • evaluation of coal petrophysics incorporating fractal characteristics by Mercury Intrusion Porosimetry and low field nmr
    Fuel, 2020
    Co-Authors: Dameng Liu, Yidong Cai, Yunpeng Wang
    Abstract:

    Abstract Mercury Intrusion Porosimetry (MIP) and low-field nuclear magnetic resonance (NMR) were combined to investigate pore-fracture structure and fractal characteristics of coals (0.93%  k N = 0.0045 ∗ e ϕ NM 0.6851 + 0.037 ), ranging from 0.043 to 2.767 mD. The NMR permeability should be related to movable fluid space and pore-fracture connectivity, and micro-fractures can largely contribute to free fluid volume.

  • insights into matrix compressibility of coals by Mercury Intrusion Porosimetry and n2 adsorption
    International Journal of Coal Geology, 2018
    Co-Authors: Yidong Cai, Yingfang Zhou
    Abstract:

    Abstract Matrix compressibility and pore properties (pore size distribution) of a rank range of coals was investigated using Mercury Intrusion Porosimetry (MIP) on coal cores with the pore size distribution also being determined using low temperature at 77 K nitrogen adsorption/desorption isotherms for crushed samples. The coal matrix compressibility is significant when the pressure of MIP is from 0.0074–35 MPa. Mathematical models were developed (based on MIP and nitrogen adsorption/desorption isotherms) to establish the porosity/pore size distribution relationships with matrix compressibility. For coal ranks, the matrix compressibility was between 0.24 × 10−4 to 13.56 × 10−4 MPa−1, and had a negative exponential relationship with the vitrinite reflectance (Ro,m%). Lignites have the maximum matrix compressibility due to their structural open structure having limitied compaction during coalification. In addition to the pore structure relationship the composition, moisture, and ash yields impacts on compressibility were also examined. Inertinite-rich coals however had a low matrix compressibility across the rank range, which may be due to the interinhibitive relationships between the mesopores, macropores and minerals. The wetting action of high moisture (water molecules) weakens the link between the coal particles of the lignites and the subbituminous coals, which causes abnormally high compressibility. Observations here relate to hydrofracturing or CO2 injection behaviors during enhancing coalbed methane (CBM) recovery.

  • pore structure and compressibility of coal matrix with elevated temperatures by Mercury Intrusion Porosimetry
    Energy Exploration & Exploitation, 2015
    Co-Authors: Dameng Liu, Yanbin Yao, Yidong Cai, Hui Wang
    Abstract:

    To gain a better understanding of the effect of heat (e.g., magma Intrusion, geothermal fluids and enhanced coal-bed methane recovery process) on coal reservoir properties, the pore structure and compressibility of coal matrix for low rank coal (0.69% Ro, m) with elevated temperatures were investigated by using multiple methods, including thermogravimetry-mass spectrometry (TG-MS), scanning electron microscope (SEM), N2 adsorption/desorption at 77 K and Mercury Intrusion Porosimetry (MIP). The results from TG-MS showed that moisture and partial volatiles were removed from the coal matrix, and pore structure almost remained unchanged during the low heat treatment (25~200℃). The micropores and transition pores consisted of more than 80% of the total pore volume based on the MIP. The pore structure was slightly changed following the temperature increase to 400℃, and the bound moisture and partial organics in the coal were released and decomposed by the increased heat, respectively. When temperature reached 4...

Na Zhang - One of the best experts on this subject based on the ideXlab platform.

  • nanoscale pore structure characterization and permeability of mudrocks and fine grained sandstones in coal reservoirs by scanning electron microscopy Mercury Intrusion Porosimetry and low field nuclear magnetic resonance
    Geofluids, 2018
    Co-Authors: Na Zhang, Fangfang Zhao, Pingye Guo, Weili Gong, Zhibiao Guo, Xiaoming Sun
    Abstract:

    Porosity and permeability of two typical sedimentary rocks in coal bearing strata of underground coal mines in China, i.e., mudrocks and fine-grained sandstones, were comprehensively investigated by multiple experimental methods. Measured porosity averages of the helium gas porosity ( ), MIP porosity ( ), water porosity ( ), and NMR porosity ( ) of the twelve investigated rock samples range from 1.78 to 16.50% and the measured gas permeabilities ( ) range from 0.0003 to 2.4133 mD. Meanwhile, pore types, pore morphologies, and pore size distributions (PSD) were determined by focused ion beam scanning electron microscopy (FIB-SEM), Mercury Intrusion Porosimetry (MIP), and low-field nuclear magnetic resonance (NMR). FIB-SEM image analyses showed that the mineral matrix pores including interparticle (interP) and intraparticle (intraP) pores with varied morphologies are the dominant pore types of the investigated rock samples while very few organic matter (OM) pores were observed. Results of the MIP and the full water-saturated NMR measurements showed that the PSD curves of the mudrock samples mostly present a unimodal pattern and nanopores with pore diameter less than 0.1 μm are their predominant pore type, while the PSD curves of the fine-grained sandstone samples are featured by a bimodal distribution. Furthermore, comparison of the full water-saturated and irreducible-water-saturated NMR measurements indicated that pores in the mudrocks are solely adsorption pores (normally pore size 0.1 μm). Moreover, the PSD curves of NMR quantitatively converted from the NMR spectra by and weighted arithmetic mean (WAM) methods are in good agreement with the PSD curves of MIP. Finally, the applicability of three classic permeability estimation models based on MIP and NMR data to the investigated rock samples was evaluated.

  • pore structure characteristics and permeability of deep sedimentary rocks determined by Mercury Intrusion Porosimetry
    Journal of Earth Science, 2016
    Co-Authors: Na Zhang, Bo Zhang, Fengchao Qiao, Hailong Sheng
    Abstract:

    Pore structure characteristics of rock are a great concern for researchers and practitioners in rock mechanics and rock engineering fields. In this study, Mercury Intrusion Porosimetry (MIP) was used to measure pore size distribution, as well as several important index parameters of pore structure, for seven common types of deep sedimentary rocks with a total of fifty rock samples. Results show a similar pore size distribution pattern of the rock samples in the same lithological group, but remarkable differences among different lithological groups. Among seven investigated rock types, mudstone has the smallest porosity of 3.37%, while conglomerate has the largest value of 18.8%. It is also found that the porosity of rock types with finer grain size is lower than those with coarser grain size. Meanwhile, a comparison of frequency distribution at ten intervals of pore-throat diameter among seven types of sedimentary rocks reveals that different rock types have different dominant pore-size ranges. Furthermore, permeability of the investigated sedimentary rock samples was derived based on MIP data using reported theoretical equations. Among seven rock types, mudstone has the lowest averaged permeability (3.64×10-6 mD) while conglomerate has the highest one (8.59×10-4 mD). From mudstone to conglomerate, rock permeability increases with an increase of grain size, with only an exception of siltstone which has a relatively larger porosity value. Finally, regression analysis show that there is a good fitting (R2=0.95) between permeability and porosity which could be easily used to derive reliable permeability values of similar kinds of engineering rocks.