Study on evaluation of geometric parameters of shale hydraulic fractures based on electromagnetic three-parameters

Abstract

Hydraulic fracturing can improve the permeability of shale reservoirs, and accurately acquiring post-fracturing fracture geometric parameters is critical for optimizing subsequent development plans and enhancing hydrocarbon recovery efficiency. This study presents a monitoring method using three electromagnetic parameters based on a single-transmitter and double-receiver coil system in a horizontal borehole. By establishing a finite-element fracture geoelectric model, the study investigates the influence of coil source distance and tool eccentricity on the three electromagnetic parameters, as well as their response characteristics under different fracture parameters. Results show that increasing the coil source distance broadens the response peak width of the three electromagnetic parameters; tool eccentricity has a more significant effect on the parameters at small source distances. The three electromagnetic parameters exhibit distinct resolution capabilities for fracture geometry: The real-part amplitude ratio offers the best resolution for fracture dip angles, the phase difference is most sensitive to changes in fracture length, and the apparent conductivity is most sensitive to variations in fracture width. Additionally, co-axial monitoring of transmitter and receiver coils cannot distinguish fractures with complementary dip angles, whereas when the two receiver coils are tilted during monitoring, all three electromagnetic parameters can effectively distinguish such fractures. This method leverages the differential sensitivity of the three electromagnetic parameters to fracture dip angle, length, and width, selecting the most suitable electromagnetic parameter for precise evaluation according to different fracture parameters and verifying results using the remaining two parameters. It provides a new solution for evaluating shale fracturing effects.