Visualization of helium-water flow in tight coal by the low-field NMR imaging: An experimental observation

D.J. Xue●Y.T. Liu●J. Zhou●X.T. Sun

Abstract

The  low-field NMR imaging (NMRI) technology plays a key role of  visualization of helium-water flow in tight coal. Combined with the  traditional description by T₂ spectrum, the NMRI description  provides an auxiliary illustration on spatial distribution of water in  various pores. To distinguish the different contribution of various  pores in helium-water flow, a flow function-based classification of  adsorption pore (AP), percolation pore (PP) and migration pore (MP) are  suggested. It depends on the periodic appearance of peak and valley of  the T₂ spectrum. Although all pores contribute to porosity, the unchanged AP peak of T₂  spectrum and the trapped water in 2D distribution shows AP contributes  little to the helium-water flow. Further, the saturation evolution is  clearly illustrated by CPMG sequence and NMRI visualization. Both  descriptions show a strong dependence of saturation evolution on pore  size distribution. Finally, the porosity is modified based on the  squeezing effect of enhancing the peak of T₂ spectrum. The  experimental result shows the helium-water flow is properly demonstrated  by the low-field NMRI method, but the drainage efficiency of helium  displacing water is not high due to the trapped water in AP.

Keywords

Low-field NMRI;Visualization;Helium-water flow;T₂ spectrum;Saturation evolution;Porosity

引用格式：

D.J. Xue, Y.T. Liu, J. Zhou, X.T. Sun. (2019). Visualization of helium-water flow in tight coal by the low-field NMR imaging: An experimental observation. Journal of Petroleum Science and Engineering, 188:1-18.

DOI:https://doi.org/10.1007/s00603-019-01974-7

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