Abstract: Wellbore ranging methods and systems for active electromagnetic ranging between a pair of conductive tubulars. Methods may include generating a depth-dependent current on one conductive tubular of the pair and a return current on another and thereby causing an injection current to flow into the earth formation by electrically exciting a first conductive tubular of the pair at a first wellhead and a second of the pair at a second wellhead, wherein the return current on the one results from the injection current on the other and is received from the earth formation; making electromagnetic measurements indicative of at least one electromagnetic field resulting from the depth-dependent current in the earth formation; and estimating a relative position of the first conductive tubular with respect to the second tubular using the electromagnetic measurements.

Abstract: Wellbore ranging methods and systems for active electromagnetic ranging between a pair of conductive tubulars. Methods may include generating a depth-dependent current on one conductive tubular of the pair and a return current on another and thereby causing an injection current to flow into the earth formation by electrically exciting a first conductive tubular of the pair at a first wellhead and a second of the pair at a second wellhead, wherein the return current on the one results from the injection current on the other and is received from the earth formation; making electromagnetic measurements indicative of at least one electromagnetic field resulting from the depth-dependent current in the earth formation; and estimating a relative position of the first conductive tubular with respect to the second tubular using the electromagnetic measurements.