Research on Reconstruction and Quantitative Characterization of Three-dimensional Cracks in Pyrolysis Anthracite

Abstract

In order to study the effect of temperature on the permeability of anthracite coal cracks, Jincheng anthracite coal was used as the research object, and the pyrolysis CT scan of Jincheng anthracite coal under different temperatures was performed by using the μCT225 kVFCB scanning system. On the basis of AVIZO three-dimensional visualization reconstruction technology, the internal cracks of coal samples were extracted. The single crack was analyzed separately, the main crack surface of the crack was constructed, and the effects of thermal cracking and pyrolysis on the development of crack at different temperatures were compared and analyzed. The research results show that: at 200 ℃ micro-cracks develop into cracks with a length of L>1 000 μm. Under different temperatures, they affect the development of the cracks. Low temperature mainly affects the individual cracks 2, and a cracking phenomenon occurs with increasing temperature. Under the action of high temperature, cracking goes through the cracks 1 and 3 to expand and develop, meanwhile the formation and penetration of secondary cracks occurs. At different temperatures and according to the length L, there are three main types of internal cracks in Jincheng anthracite, which are 1 μm<L<100 μm, type I; 100≤L<1 000 μm, type II; and L≥1 000 μm, type III. Under the effect of different temperatures, the direction of the main crack surface tensor extracted by a single crack is different; as the temperature increases, crack develops faster in the direction of bedding. Especially, the development of the crack space is most significant at 300 ℃ and 600 ℃. At higher temperature, the fissures are interconnected and the permeability is increased, which provides a high permeability channel for coalbed methane extraction.

Keywords

• anthracite
• ct visualization
• three-dimensional reconstruction
• crack
• pyrolysis