Patent ID: 6584408
Filing Date: 2003-06-24
Classification: G01V

Abstract:
A method for determining a parameter of a subsurface formation from electromagnetic measurements acquired with a logging tool disposed within said formation, said tool adapted with a tri-axial system of transmitter and receiver antennas, comprising:a) determining couplings associated with said measurements; and b) calculating the following expression derived from said couplings to determine the horizontal conductivity (&sgr;h) of said formation: (Tâ€²zzâˆ’Lh)(Tâ€²xxâˆ’Th)=(Tâ€²xz)2, â€ƒwhere Tâ€²zz is the coupling between a z-axis receiver antenna and a z-axis transmitter antenna; Tâ€²xx is the coupling between an x-axis receiver antenna and an x-axis transmitter antenna; Tâ€²xz is the coupling between an x-axis receiver antenna arid a z-axis transmitter antenna; Lh, Th are elementary functions corresponding to said couplings of said antennas: Th=&ee;ikh&it;r4&it;Ï€&it;â€ƒ&it;r3&it;(-1+ikh&it;r+kh2&it;r2),â€ƒ&it;Lh=&ee;ikh&it;r2&it;Ï€&it;â€ƒ&it;r3&it;(1-ikh&it;r);r is the separation distance between the antennas; and kh2=i&ohgr;&mgr;&sgr;h.