Patent ID: 9696450
Date: 2017-07-04
CPC Classifications: E21B,G01V

Claim:
1. A method of induced polarization logging of subsurface earth formations from a well borehole which has a casing installed along its extent into the earth to a location of interest near a formation of interest, the casing being formed of lengths of tubular members connected at end portions to adjacent tubular members by casing collars, the method comprising the steps of: lowering a borehole to surface electromagnetic survey transmitter with a sonde body connected therewith to the location of interest in the borehole below the casing; locating a ground electrode at the surface of the earth; locating an array of surface electromagnetic field receivers at spaced positions over a surface area on the earth surface conforming to dimensions of a reservoir of interest; forming a measure with the casing collar locator of the number of casing collars past which the source and sonde body travel during the step of lowering to determine the depth of the source and sonde body in the borehole based on the measured number of casing collars; deactivating the casing collar locator when the source and the sonde body are at the location of interest; and emitting an electromagnetic field from the borehole to surface electromagnetic survey transmitter at the location of interest to travel through the subsurface formations to the surface and form an electromagnetic field; sensing the formed electromagnetic field with the array of surface electromagnetic field receivers; detecting with the array of surface electromagnetic field receivers a measure of induced polarization resulting from the electromagnetic field emitted from the borehole to surface electromagnetic energy field for induced polarization logging of the subsurface earth formations.