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: A downhole antenna tool is disclosed for downhole well-logging or other downhole operations. Antenna bars are provided for winding of coils through associated coil carriers of individual ones of the antenna bars. The antenna bars with the wound coils are coated with a protection layer and are releasably coupled to a substrate of the downhole antenna tool using, for example, a silicone cushion layer.

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: Methods and devices for evaluating earth formations. Methods include making a plurality of radiation measurements with a GR detector disposed on a carrier in the borehole and a second GR detector disposed on the carrier by positioning the first GR detector and the second GR detector in the borehole at each borehole depth such that the first GR detector is radially offset from the second GR detector with respect to the longitudinal axis of the borehole; making an estimate of a concentration of at least one chemical element in the formation for each borehole depth for each of the first GR detector and the second GR detector from the plurality of measurements; and estimating an actual concentration of the at least one chemical element using the estimates of the concentration for the first GR detector and the estimates of the concentration for the second GR detector for each borehole depth.