Reformed pattern of coal reservoirs in reformed coal basins and effect on favorable blocks of coalbed gas in the North China craton

Two patterns of reformed coal reservoirs in reformed coal basins, the reformation of coal structure and reformed fracture by aposedimentary fillings and forming of the fillings are introduced. A new criterion of structural coal is proposed to judge the reformed degree of coal basins. Evolution of compressional structure in Mesozoic to extensional structure in Cenozoic and area of different types of structures in the North China craton are summarized. The results indicated that this type evolution is easy to form the structural coal and aposedimentary fillings. Three reformed structural types and each area in the North China craton are put forward, the property of coal reservoirs and their effect on favorable blocks of coalbed gas are analyzed. The study and examination of coalbed gas of Jurassic coal in Ordos basin should be emphasized.