A New Method for Fracture Diagnostics Using Low Frequency Electromagnetic Induction

Abstract

Abstract Currently, microseismic monitoring is widely used for fracture diagnosis. Since the method monitors the propagation of shear failure events, it is an indirect measure of the propped fracture geometry. Our primary interest is in estimating the orientation and length of the ‘propped’ fractures (not the created fractures), since this is the primary driver for well productivity. This paper presents a new Low Frequency Electromagnetic Induction (LFEI) method which has the potential to estimate not only the propped length, height and orientation of hydraulic fractures but also the vertical distribution of proppant within the fracture. The proposed technique involves pumping electrically conductive proppant (which is currently available) into the fracture and then using a specially built logging tool that measures the electromagnetic response of the formation. Results are presented for a proposed logging tool that consists of three sets of tri-directional transmitters and receivers at 6, 30 and 60 feet spacing respectively. The solution of Maxwell's equations shows that it is possible to use the tool to determine both the orientation and the length of the fracture by detecting the location of these particles in the formation after hydraulic fracturing. Results for extensive sensitivity analysis are presented to show the effect of different propped lengths, height and orientation of planar fractures in a shale environment. Multiple numerical simulations, using a leading-edge (FEKO) electromagnetic simulator, indicate that we can detect and map fractures up to 250 feet in length, 0.2 inches wide, and with a 45 degree of inclination with respect to the wellbore. Special cases, such as proppant banking and wells with steel casing in place, were also considered.