Comparative Study of Coal Sample Stress Sensitivity Characterized by Different Methods

Abstract

The stress sensitivity of pores and fractures in four groups of coal samples was measured and analyzed comprehensively by overburden nuclear magnetic resonance(NMR) and permeability. The results show that the compression coefficient based on the overburden permeability increases with the increase of fracture development, the corresponding T2 spectral area of pore and fracture decreases exponentially with the increase of stress, in the same sample, the stress sensitivity of fracture is greater than that of seepage pore, and the adsorption pore is the lowest; compared with the pore developed samples, the compression coefficient of the fissure developed adsorption pore did not change significantly with the stress; in the same pressure range, the compressibility obtained by permeability is obviously greater than that obtained by NMR.

Keywords

• coal reservoirs
• pore
• fracture
• coefficient of compressibility
• permeability
• coalbed gas production
• gas-water migration