Development of Metal-Seal Packer to Estimate In-Situ Fracture Aperture

Abstract

To develop a Hot Dry Rock power generation system, artificial fractures within a rock must be newly created or natural fractures must be stimulated by hydraulic pressurization. Fractures play an important role as a heat exchanger within a rock. In the case of conventional geothermal reservoir that consists of natural fractures, fractures also play an important role as a geothermal fluid path. Especially in HDR development, if the thickness of the fracture is too thin, then the injection pressure would be very high and an economical operation would be difficult. In hydraulic fracturing or stimulation operation, estimation of the spatial fracture aperture distribution with elapsed time is very important to decide the total volume injection of water and to decide the pumping power. Nevertheless, it is difficult to estimate the in-situ fracture aperture and there have been not enough data about fracture aperture. As a basic study of estimating the fracture aperture within a borehole, a ëDual Single-Packerí has been developed. This paper describes the principle of the packer and experimental results of in-situ and laboratory experiment obtained by the new packer.