NMR experiments on the migration characteristics of water in bedding-bearing low rank coal

Ma, Yankun; Ye, Meng; Zhang, Xi; Deng, Zimo; Zhao, Aohan; Yue, Jiwei

doi:10.1080/10916466.2023.2175867

Cited by 2 publications

(3 citation statements)

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“…Once the residual pressure is removed, water enters the pores through spontaneous imbibition under the action of capillary forces. , When the direction of imbibition is consistent with the direction of CBM production, the capillary force is the driving force of CBM migration. Otherwise, it is resistance. , This resistance causes the retention of fracturing fluid, known as the water-blocking effect. , Therefore, water imbibition in coal seams is considered a key factor affecting CBM recovery, and understanding the transport mechanism of the water imbibition process in coal bodies is of great importance for CBM production. − …”

Section: Introductionmentioning

confidence: 99%

“…Meanwhile, it has been observed that most of the studies tend to focus on cores in the field of petroleum engineering, with very few investigations into coal cores. 13,35 In this study, samples from the Datong, Duanshi, and Sihe coal mines in the Qinshui Basin and the Zhangjiamao coal mine in the Ordos Basin are selected as research objects. The samples were made into 25 mm diameter columns for spontaneous imbibition experiments at room temperature.…”

Section: Introductionmentioning

confidence: 99%

“…However, there is limited research on the direct monitoring of water migration processes. Meanwhile, it has been observed that most of the studies tend to focus on cores in the field of petroleum engineering, with very few investigations into coal cores. , …”

Section: Introductionmentioning

confidence: 99%

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Experimental Study on Spontaneous Imbibition of Coal Samples of Different Ranks Based on the NMR Relaxation Spectrum

Wang,

Du,

et al. 2023

ACS Omega

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The comprehension of the mechanisms governing spontaneous water imbibition in gas–water systems plays a significant role in the operation of hydraulic fracturing and the development of coalbed methane (CBM). In this study, nuclear magnetic resonance (NMR) techniques were used to investigate the pore structure and fluid behavior of different rank coal samples during spontaneous imbibition. Analyses were conducted on the 1D NMR T 2 spectrum, 2D NMR T 1–T 2 spectrum, and layer division T 2 spectra to achieve accurate and detailed information about the internal pore structure of coal and the characteristics of fluid transport during spontaneous imbibition. Low-rank coal exhibits good pore connectivity and favorable pore sorting characteristics, indicating favorable reservoir conditions. High-rank coal has larger pore spaces and highly developed micropores, which are highly beneficial for gas adsorption. However, its poor pore sorting characteristics and connectivity limit the migration and diffusion of fluids within the reservoir. The imbibition capacity follows a specific order of contribution, with small pores (10–50 nm) having the most significant role, followed by micropores (2–10 nm), ultramicropores (r < 2 nm), mesopores (50–1000 nm), macropores (1000–10,000 nm), and microfractures (r ≥ 10,000 nm). Low-rank coal stands out due to the restricted development of ultramicropores and small pores, leading to a different contribution of imbibition capacity compared to other samples, where macropores and microfractures dominate over all pore types. The coal reservoirs with favorable pore sorting characteristics and pore connectivity tend to exhibit a tendency toward rapid saturation and attainment of a prompt stable state during the hydraulic fracturing process. Finally, the mechanism of the late retreat effect of imbibition and the laws governing different coal ranks, pore structures, and fluid transport were discussed. This study offers comprehensive analyses of the mechanism of coal spontaneous imbibition and the characteristic laws of fluid seepage, providing insights into the optimization of CBM recovery and reservoir management.

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