Apparatus for determining a natural current flow in well casing

摘要

An apparatus for determining the natural current flow in the casing of a well. The apparatus includes earth surface control and recording equipment connected by a cable to an instrument housing. A casing collar locator on the instrument is used to assist in positioning the instrument in the well casing. A plurality of electrodes on the instrument are contactable with the interior of the casing. The earth surface equipment and the electrodes are used to measure voltages and to pass an electrical current through the casing. Measurements of native voltages in the casing and the change in voltage between two locations in the casing during application of a known current are used to determine the casing's resistance at that location in the well and the native current flow between the well casing and the earth formation throughout the well.