TY - JOUR
T1 - A novel pore size classification method of coals
T2 - Investigation based on NMR relaxation
AU - Zheng, Sijian
AU - Yao, Yanbin
AU - Elsworth, Derek
AU - Wang, Bo
AU - Liu, Yong
N1 - Funding Information:
We acknowledge financial support from the National Natural Science Foundation of China ( 41830427 ; 41872123 ), the National Major Science and Technology Projects of China ( 2016ZX05043-001 ), the Key research and development project of Xinjiang Uygur Autonomous Region ( 2017B03019-1 ), and the Fundamental Research Funds for the Central Universities ( 292019252 ).
Funding Information:
We acknowledge financial support from the National Natural Science Foundation of China (41830427; 41872123), the National Major Science and Technology Projects of China (2016ZX05043-001), the Key research and development project of Xinjiang Uygur Autonomous Region (2017B03019-1), and the Fundamental Research Funds for the Central Universities (292019252).
Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/9
Y1 - 2020/9
N2 - Nuclear magnetic resonance (NMR) severs as a nondestructive and relative new technique that has been widely used in characterizing reservoir fluids and pore size distribution (PSD) of coals. Conventionally, pore fluids in coals are classified into movable fluid and irreducible fluid based on a single NMR T2 cutoff value (T2C). However, the single NMR T2 cutoffs model has some apparent defects in pore fluid/size classification, and few researches have reported the limitation of the single T2 cutoffs model. In contrast, the dual T2 cutoffs model may provide an accurate quantified model to classify different pore fluid types in coals. In this study, fifteen coal samples with different ranks were conducted in systematic NMR and centrifugal experiments to investigate the characteristics of pore fluid typing and PSD. Results show that when tried applying the single NMR T2 cutoffs model to classify the pore fluid typing, there are still some movable fluids when T2 < T2C. At the same time, when T2 > T2C, there is remaining some irreducible fluid in pores after high pressure centrifugal experiments. These results indicated the limited application of single NMR T2 cutoffs model in pore fluid classification. By introducing a novel pore fluid classification method (i.e. the dual T2 cutoffs model), a typical T2 spectrum under fully-saturated condition, the absolute irreducible fluid T2 cutoffs (T2C1) and absolute movable fluid T2 cutoff (T2C2) can re-divide the pore fluid typing of coal into three types: absolute irreducible fluid (T2 < T2C1), partial movable fluid (T2C1 < T2 < T2C2), and absolute movable fluid (T2 > T2C2). The results show that the T2C1 is in the range of 0.10–0.32 ms, while the T2C2 has a wider range from 36.12 ms to 89.07 ms. Finally, a conceptional model were proposed to clarify a full-scale PSD classification that includes the absolute irreducible fluid pores, partial movable fluid pores and absolute movable fluid pores. The model established in this study, can also be applicable for other rock types (e.g., sandstones, carbonates and shales).
AB - Nuclear magnetic resonance (NMR) severs as a nondestructive and relative new technique that has been widely used in characterizing reservoir fluids and pore size distribution (PSD) of coals. Conventionally, pore fluids in coals are classified into movable fluid and irreducible fluid based on a single NMR T2 cutoff value (T2C). However, the single NMR T2 cutoffs model has some apparent defects in pore fluid/size classification, and few researches have reported the limitation of the single T2 cutoffs model. In contrast, the dual T2 cutoffs model may provide an accurate quantified model to classify different pore fluid types in coals. In this study, fifteen coal samples with different ranks were conducted in systematic NMR and centrifugal experiments to investigate the characteristics of pore fluid typing and PSD. Results show that when tried applying the single NMR T2 cutoffs model to classify the pore fluid typing, there are still some movable fluids when T2 < T2C. At the same time, when T2 > T2C, there is remaining some irreducible fluid in pores after high pressure centrifugal experiments. These results indicated the limited application of single NMR T2 cutoffs model in pore fluid classification. By introducing a novel pore fluid classification method (i.e. the dual T2 cutoffs model), a typical T2 spectrum under fully-saturated condition, the absolute irreducible fluid T2 cutoffs (T2C1) and absolute movable fluid T2 cutoff (T2C2) can re-divide the pore fluid typing of coal into three types: absolute irreducible fluid (T2 < T2C1), partial movable fluid (T2C1 < T2 < T2C2), and absolute movable fluid (T2 > T2C2). The results show that the T2C1 is in the range of 0.10–0.32 ms, while the T2C2 has a wider range from 36.12 ms to 89.07 ms. Finally, a conceptional model were proposed to clarify a full-scale PSD classification that includes the absolute irreducible fluid pores, partial movable fluid pores and absolute movable fluid pores. The model established in this study, can also be applicable for other rock types (e.g., sandstones, carbonates and shales).
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U2 - 10.1016/j.jngse.2020.103466
DO - 10.1016/j.jngse.2020.103466
M3 - Article
AN - SCOPUS:85088088197
SN - 1875-5100
VL - 81
JO - Journal of Natural Gas Science and Engineering
JF - Journal of Natural Gas Science and Engineering
M1 - 103466
ER -