Title: Analysis of the effect of different pretreatment conditions on pore structure heterogeneity of low-rank coal based on multifractal theory

Authors: Lirong Gao; Teng Li; Jiao Peng; Jianzhong Zhang

Addresses: Shaanxi Key Laboratory of Advanced Stimulation Technology for Oil and Gas Reservoirs, Xi'an Shiyou University, Xi'an, Shaanxi 710065, China; College of Petroleum Engineering, Xi'an Shiyou University, No. 18, Section 2, Dianzi Road, Xi'an, Shaanxi Province 710065, China ' Shaanxi Key Laboratory of Advanced Stimulation Technology for Oil and Gas Reservoirs, Xi'an Shiyou University, Xi'an, Shaanxi 710065, China; College of Petroleum Engineering, Xi'an Shiyou University, No. 18, Section 2, Dianzi Road, Xi'an, Shaanxi Province 710065, China ' Shaanxi Key Laboratory of Advanced Stimulation Technology for Oil and Gas Reservoirs, Xi'an Shiyou University, Xi'an, Shaanxi 710065, China; College of Petroleum Engineering, Xi'an Shiyou University, No. 18, Section 2, Dianzi Road, Xi'an, Shaanxi Province 710065, China ' Shaanxi Yanchang Petroleum (Group) Company Limited, No. 4 Gas Production Plant of Yanchang Gas Field, Yan'an, Shaanxi 716000, China

Abstract: In order to select the pretreatment conditions of low-temperature nitrogen adsorption experiment more scientifically, low-temperature gas adsorption experiments of five particle-size subsamples pretreated at seven degassing temperatures were conducted. The results showed that the higher the degassing temperature, the faster the volatile and water separated, and some of pores collapsed. After mechanical crushing, some pores are filled and blocked by mineral particles. Multifractal analysis shows that the pore connectivity hardly improves with increasing degassing temperature, while the heterogeneity of pore distribution is enhanced. With the decrease of particle size, the heterogeneity of pore size distribution decreases, while the connectivity of pores increases. With the increase of degassing temperature or the decrease of particle size, nitrogen adsorption capacity, sample mass, pore volume and pore area all showed a three-stage decline. Ultimately, 120°C and 40-60 mesh are recommended as the best degassing temperature and sample size for low-temperature gas adsorption method. [Received: February 24, 2023; Accepted: April 14, 2024]

Keywords: pretreatment temperature; particle size effect; pore structure; multifractal analysis; low rank coal.

DOI: 10.1504/IJOGCT.2024.140912

International Journal of Oil, Gas and Coal Technology, 2024 Vol.36 No.3, pp.338 - 365

Received: 23 Feb 2023
Accepted: 14 Apr 2024
Published online: 03 Sep 2024 *

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