Patent ID: 7298147

Claim:
Process for determining an improved profile of a variation along an axial direction of a resistivity of a geological formation surrounding a well equipped with a lining along the said axial direction, process in which a local resistivity of the formation is determined by injecting a current in the lining to create a leakage current in the formation measurement zone and measuring potential values at first positions with a spacing between consecutive positions equal to an average value, the first positions comprising at least one central position (eb) between an upper end position (ea) and a lower end position (ec) along the axial direction, and using the measurement results to calculate a local value of the leakage current in the formation to determine a value of the resistivity of the said formation in the said measurement zone and then to restart the measurement by moving the first potential measurement positions along the axial direction, to deduce a first profile of the variation of the resistivity along the axial direction, process, wherein for each local potential measurement made in the first positions, a potential measurement at two second positions is made simultaneously on each side of the first positions, a second position being at a distance from the closest end position of more than 1.5 times the average value of the spacing between consecutive positions to deduce a second profile for the variation of the resistivity along the axial direction and then to correct the first profile by replacing resistivity values of the first profile for the first axial positions by resistivity values of the second profile when the resistivity values of the second profile at the same first axial positions are greater than the first values, the profile thus corrected forming the improved profile.