Heterogeneous structural responses of high-rank coal pores to hydraulic fracturing based on low-field nuclear magnetic resonance

Pores in coal are not only the main space for coalbed methane (CBM) occurrence but also to be opened during CBM recovery. Therefore, analysis of impact hydraulic fracturing on pores, especially change adsorption pores before and after fracturing, is great significance evaluation effect Hydraulic experiments low-field nuclear magnetic resonance technology were used analyze changes T 2 curve, pore, effects distance situ stresses pore modification samples Sihe (SH) Chengzhuang (CZ) mines fracturing. The results show that can affect <10 nm. CZ exhibit stronger heterogeneity than SH size distribution (PSD) anisotropy increased. For with poor heterogeneity, transformation depends more stresses. smaller horizontal difference facilitates establishment complex networks. After when diameter 30–100 nm, volume proportions directions maximum principal stress (? H ), minimum h vertical V ) increase from 43.73% 64.84%, 59.79%, 60.16%, respectively. increases PSD samples.