Identification of the depth range of in situ shale oil production

Oil shale resource is an important supplement to conventional oil and gas in China. Thermal in situ retorting processes for producing hydrocarbons from oil shale have been utilized recently. Based on the mechanical analysis of the process of oil shale retorting, for an efficient production of shale oil and gas at least two requirements should be met. Firstly, the expulsion pressure of oil and gas from shale needs to be lower than the breakdown pressure of the overburden interval, to keep the produced oil and gas confined. Secondly, the expulsion pressure of oil and gas should be higher than the breakdown pressure of the shale reservoir to enable the development of more fractures to allow oil and gas to flow. The expulsion pressure of oil and gas from shale is primarily dominated by temperature which means that a vertical or horizontal heater delivery borehole needs place at a proper depth. The higher the heating temperature for in situ shale oil production is, the deeper and thicker the oil shale reservoir should be.