Patent ID: 9606257
Date: 2017-03-28
CPC Classifications: G01V

Claim:
1. A method for determining existence of a fracture in a formation surrounding a wellbore drilled through subsurface rock formations, comprising: deploying an electromagnetic logging tool in the wellbore, the electromagnetic logging tool including a triaxial transmitter and a triaxial receiver longitudinally spaced apart from one another; causing the triaxial transmitter to transmit electromagnetic energy into the subsurface rock formations; causing the triaxial receiver to receive said transmitted electromagnetic energy to obtain electromagnetic measurements such that the obtained electromagnetic measurements comprise responses between the triaxial transmitter of the electromagnetic logging tool and the triaxial receiver of the electromagnetic logging tool; determining a fracture orientation value of the rock formations from only two measured responses of the electromagnetic logging tool in accordance with the following equation: wherein the two measured responses are transverse with respect to one another, and wherein θ represents the fracture orientation value, σxx represents an apparent conductivity of the one of the two measured responses, σyy represents an apparent conductivity of the other of the two measured responses, and σxx determining a fracture indicator value of the rock formations based at least partially upon the two measured responses and the fracture orientation value; and determining the presence of a fracture in the rock formations based upon the magnitude of the fracture indicator value.