Thermal and nonthermal effect of microwave irradiation on the pore microstructure and hydrocarbon generation of organic matter in shale

In situ heating conversion is the most effective means to develop medium-low maturity shale oil. Herein, the effects of microwave irradiation on the shale pore structure and hydrocarbon generation of organic matter were studied using an independent development microwave device in combination with Rock-Eval, Leco analysis, X-ray diffraction, field emission scanning electron microscopy, low-temperature N2 adsorption/desorption, nuclear magnetic resonance, Fourier transform infrared spectroscopy and kinetic simulation of hydrocarbon generation. The results show that microwave irradiation can effectively heat shale and the temperature can rise to hundreds of degrees Celsius in a short time (10 min), with 400 °C as the best temperature for in situ conversion of medium-low maturity shale, at which the pore volume and surface area reach the maximum. Microwave irradiation is conducive to pyrolysis and hydrocarbon generation of aliphatic structure in shale organic matter. There are differences in the response of different organic components to the nonthermal effect of microwave irradiation, which reduces the activation energy of hydrocarbon generation during organic matter pyrolysis. Heating shale by microwave irradiation can effectively promote organic matter pyrolysis and hydrocarbon generation, improve rock reservoir and seepage capacity, and is of great significance for the efficient development of shale oil. •An investigation of thermal and nonthermal effects of microwave irradiation on shale pores and organic matter.•400 °C is the best temperature for in-situ conversion of the medium-low maturity shale.•Microwave irradiation is conducive to pyrolysis of aliphatic structure compared with conventional heating.•The responses of different organic components to nonthermal effect in microwave irradiation heating are different.