Cyclic LN2 Treatment of Coal Samples from Coal Basin in Kazakhstan

Abstract

In recent years liquid nitrogen (LN2) fracturing technology has been investigated as a promising stimulating technique in coalbed methane (CBM) development. Using the immersion method, this study experimentally examines and illustrates the efficacy of LN2 cryogenic fracturing for a CBM reservoir in the Karaganda Basin of East Kazakhstan. Coal core plugs were frozen with LN2 under different lab-controlled conditions like the length freezing time (FT) and the number of freezing thawing cycles (FTC). Then these treated core plugs were subjected to uniaxial compressive strength test and SEM analysis for comparisons. The results from SEM analysis showed that the LN2 freezing-thawing process can augment the cryogenic fracture and the fracture interconnectivity. Moreover, uniaxial compressive test indicated that compressive strength is kept decreasing with successively increasing the number of freezing-thawing cycles and the same decreasing trend was observed with freezing time experiments compared with the coal sample without liquid nitrogen case.