Powder Technology

Cyclic thermal impact technology can effectively modify shale reservoirs and improve reservoir fracture networks while removing water phase traps to increase shale gas permeability. Therefore, an experiment on the cyclic thermal impacts of shale was conducted to investigate the alteration of pore structure and permeability of shale before and after cyclic thermal impacts. The results indicated that, under the thermal impact temperature of 300 °C, pores were continuously generated and expanded in the shale. With the increase in thermal impacts, the cumulative porosity of shale gradually increases, and the growth trend is a logarithmic function of the number of thermal impacts. The permeability of shale can be increased effectively through cyclic thermal impacts, and it increases logarithmically with the number of thermal impacts indicates the importance of multiple injection heat treatments in the process of improving the permeability of shale reservoirs. • Pore distribution and permeability enhancement of shale under thermal impacts. • Pore distribution change of shale under cyclic thermal impacts by NMR. • The relationship between pore structure change and permeability increase.

Pore structure alteration and permeability enhancement of shale under cyclic thermal impacts