首页|Investigation of organic-shale nanopores in the Lower Cambrian Niutitang Formation using low temperature N-2 and CO2 adsorption: Multifractality and classification

Investigation of organic-shale nanopores in the Lower Cambrian Niutitang Formation using low temperature N-2 and CO2 adsorption: Multifractality and classification

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  • NSTL
  • Elsevier
Nanopores in organic shale reservoirs are of great significance for shale gas accumulation and carbon dioxide geological sequestration. To explore the multifractality and classification of nanopores in the Lower Cambrian Niutitang Formation shales, nine shale samples were selected from the well TX1 in North Guizhou, South China. Then, we conducted TOC analysis, XRD analysis and SEM to investigate shale material composition and nanopore morphology and low temperature N2 and CO2 adsorption experiments were used to quantitatively characterize the nanopore structure. The multifractal theory was applied to study the spatial distribution of nanopores. Results showed that nanopores in Niutitang Formation shales are mainly organic pores with pore sizes less than 50 nm, followed by intraparticle dissolution pores; interparticle pores are rarely observed. According to the results of the N-2 adsorption experiments, our samples can be divided into three types. Type I samples have the highest average pore size, whereas Type III samples have the highest pore volume and surface area. Results of the CO2 adsorption experiments indicated a trimodal distribution of measured pores. Our study revealed the multifractality of nanopores, and the complexity of pores measured via N2 adsorption is stronger than that measured via CO2 adsorption. Results of multifractal analysis via N2 adsorption demonstrated that Type I samples have the strongest pore agglomeration and Type III samples have the most uniform pore size distribution. For nanopores measured via CO2 adsorption, subtle differences exist in multifractal characteristics of the various samples. An increase in the pore volume measured via N(2 & nbsp;)adsorption corresponds to a decrease in pore aggregation and heterogeneity and an increase in pore connectivity. For nanopores detected via CO2 adsorption, no obvious correlations were observed between the pore structure and multifractal parameters. We propose a new nanoporeclassification scheme based on pore heterogeneity and connectivity. Nanopores of the selected samples can be classified as micropores (< 10 nm), mesopores (10-25 nm), and macropores (> 25 nm). Fractal properties of nanopores obtained from SEM images showed that mesopores have weaker heterogeneity and better connectivity than micropores and macropores, which also indicates the reasonability of our pore classification.

NanoporesMultifractal analysisPore classificationN-2/CO2 adsorptionNiutitang shalePORE STRUCTURE CHARACTERIZATIONUPPER YANGTZE PLATFORMMATURATION GRADIENT INSIGHTSNUCLEAR-MAGNETIC-RESONANCESICHUAN BASINFRACTAL CHARACTERISTICSGAS-ADSORPTIONSIZE DISTRIBUTIONSBLACK SHALESSOUTH CHINA

Tong, Zhongzheng、Zhang, Jinchuan、Li, Zhen、Wu, Yaning、Wang, Dongsheng、Gong, Dajian

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China Univ Geosci

Tongren Sino Energy Nat Gas Corp

2022

10.1016/j.micromeso.2022.111935

Microporous and mesoporous materials

Microporous and mesoporous materials

EISCI
ISSN：1387-1811
年,卷(期)：2022.337
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