Effects of Cap Rock and Hydrodynamic on CBM Preservation A Case Study From Ordos Basin, China

Different from other countries, more than 60% of total resources in China occur in medium- to high-rank coal basins and experienced complicated evolution in the long history of tectonic subsidence and uplifting. CBM preservation in these basins requires high sealing conditions. A series of investigations has documented factors influencing CBM enrichment and production. Among the factors, cap rock and hydrodynamic condition were identified as two primary control factors which has a significant influence on CBM preservation. The combination of low permeability mudstone with a high Young’s modulus in the roof and floor is very beneficial to the preservation of CBM. Type NaHCO3 and type NaCl formation water with the TDS (Total Dissolved Solids) value ranges from 1200mg/L to 4000mg/L is an indicator for a suitable preservation of CBM.