Analysis on correlation between nanopores and coal compositions during thermal maturation process. (November 2020)

• Record Type: Journal Article
• Authors: Li, Pengpeng; Zhou, Shixin; Zhang, Xiaodong; Li, Jing; Zhang, Shuo; Hou, Anqi; Guo, Chen
• Is Part Of: Marine and petroleum geology. Volume 121(2020)
• Publication Date: 2020-11
• Subjects: Nanopores -- Coal compositions -- Thermal maturation -- Pore structure parameters -- Fractal dimensions -- Gray correlation analysis; Submarine geology -- Periodicals; Petroleum -- Geology -- Periodicals; Géologie sous-marine -- Périodiques; Pétrole -- Géologie -- Périodiques; Petroleum -- Geology; Submarine geology; Periodicals; Electronic journals; 551.468
• DOI: 10.1016/j.marpetgeo.2020.104608
• Languages: English
• ISSNs: 0264-8172

Abstract

Abstract: The evaluation of nanopore that links to methane accumulation space and migration channel is vital for coalbed methane development and underground gas drainage. This work aims to uncover the evolution of coal compositions and nanopores with thermal maturation and to evaluate quantitatively the influencing degrees of coal compositions on pore structure parameters based on gray correlation analysis using 498 coal samples from different countries, covering a very wide and continuous thermal maturation range (Ro = 0.22–5.18%) and representing commercially valuable coal seams, typical coal basins and coalfields and CBM development sweet spots. As thermal maturation increases, pore structure parameters and coal compositions changes regularly. As thermal maturation increases, PV-N2, SSA-N2 show a rough "W-shaped" trendency with left steepness and right slowness while fractal dimensiosshow a rough "U-shaped" trend with left steepness and right slowness, APD-N2 present an approximate "M-shaped" trend, PV-CO2 and SSA-CO2 both present an asymmetrical "V-shaped" tendency with a minimum value at Ro between 1.0 and 1.3%. Concerning coal compositions, with progressive thermal maturation, there are the "L-shaped" evolution of moisture, the increasing envelope line of vitrinite and the decreasing envelope lines of inertinite, exinite and minerals with the same trend of first steepness and then slowness. In essence, the alteration of pore structure parameters is closely linked to the evolution of coal compositions. Fractal dimensions are controlled by coal macerals while inorganic compositions like moisture and minerals have a significant impact on PV-N2 and SSA-N2 within whole thermal maturation process. Highlights: Evolution of nanopores and coal compositions with thermal maturation is analyzed. The effects of coal compositions on pore structure parameters are evaluated quantitatively. Fractal dimensions are controlled by coal macerals while inorganic compositions like moisture and minerals have a significant impact on PV-N2 and SSA-N2 .