Shale Permeability Enhancement for Efficient Recovery Using Electromagnetic Heating Stimulation

Abstract:

Source rock shales have permeability in the nano-Darcy range and require drilling long horizontal wells and extensive hydraulic fracturing to commercially produce hydrocarbon. Recently, an electromagnetic (EM) thermal method has been proposed as a primary, or secondary, stimulation method to produce light hydrocarbon from extremely tight reservoirs. This method is based on the fact that EM heating rapidly elevates the pore-water pressure in tight rocks to fracture the reservoir. Since only the in-situ pore-water is needed, this is considered to be a water-free stimulation method, which is especially desirable for regions with limited water resources. This study provides an in-depth investigation of the effects of laboratory EM stimulation on tight rocks under hydrostatic confinement through the quantitative evaluation of the permeability changes. In order to maintain hydrostatic pressure, a special pressure cell was designed using nearly microwave transparent materials. Permeability of the samples before and after EM stimulation was acquired using a novel method capable of simultaneously measuring both matrix and fracture permeability. Microwave heating was found to generate extensive fractures in the source rock samples with pore-water less than 3%, which resulted in an increase of more than three orders of magnitude in permeability. This study provides comprehensive evidences that EM thermal stimulation can be an efficient production method for source rock reservoirs and can result in both a high recovery rate and large estimated ultimate recovery of hydrocarbon.