Patent ID: 6466872
Filing Date: 2002-10-15
Classification: G01V

Abstract:
A method of determining a parameter of interest of subsurface formations containing a sand and a shale surrounding a borehole, the method comprising:(a) conveying an electromagnetic logging tool into the borehole and using at least one electromagnetic transmitter and one electromagnetic receiver on the tool to obtain measurements related to a horizontal and vertical resistivity of the formation; (b) obtaining a plurality of layer intervals for the subsurface; (c) deriving a horizontal and vertical resistivity at a plurality of depths from said measurements using an anisotropic whole space model; (d) obtaining from the derived horizontal and vertical resistivities a layered model; (e) deriving a shoulder bed corrections based upon the layered model and the whole space model; (f) applying the shoulder bed corrections to said measurements to obtain shoulder bed corrected measurements; (g) determining a difference between said shoulder bed corrected measurements at the center of each said plurality of layers to a synthetic response of the whole space model at said centers; and (h) iteratively repeating steps (c)-(g) to give an updated layered model.