Abstract: A method for using a tool in a wellbore in a formation to predict an anomaly in the formation ahead of the device, the tool comprising a transmitter for transmitting electromagnetic signals through the formation and a receiver for detecting response signals. the method comprises a) bringing the tool to a first position inside the wellbore; b) energizing the transmitter to propagate a transient electromagnetic signal into the formation; c) detecting a response signal that has propagated through the formation as a result of the transient signal in step (b); d) calculating a derived quantity for the formation as a function of time based on the detected response signal for the formation; e) plotting the derived quantity for the formation against time; f) moving the tool to at least one other position within the wellbore and repeating steps (b) to (e); g) predicting an anomaly in the formation.

Abstract: A method of imaging a subterranean formation traversed by a wellbore using a tool comprising a transmitter for transmitting electromagnetic signals through the formation and a receiver for detecting response signals. The tool is brought to a first position inside the wellbore, and the transmitter is energized to propagate an electromagnetic signal into the formation. A response signal that has propagated through the formation is detected. A derived quantity for the formation based on the detected response signal for the formation is calculated, and plotted against time. The tool may be moved to at least one other position within the wellbore where the procedure may be repeated to create an image of the formation within the subterranean formation based on the plots.

Abstract: Method of analyzing a subterranean formation traversed by a wellbore. The method uses a tool comprising a transmitter antenna and a receiver antenna, the subterranean formation comprising one or more formation layers. The tool is suspended inside the wellbore, and one or more electromagnetic fields are induced in the formation. One or more time-dependent transient response signals are detected and analyzed. Electromagnetic anisotropy of at least one of the formation layers is detectable. Geosteering cues may be derived from the time-dependent transient response signals, for continued drilling of the well bore until a hydrocarbon reservoir is reached. The hydrocarbon may then be produced.

Abstract: Detecting in an earth formation a boundary between first and second formation regions having different resistivities, wherein the first formation region is traversed by a wellbore, using a logging tool provided with a number of electrodes including a monitoring electrode, the method having: a) selecting a location of the logging tool in the wellbore; b) assuming a position of the boundary relative to the selected location, selecting outside the wellbore a target point relative to the selected location, and selecting a target value for a selected parameter in the target point; c) assuming a model wherein the logging tool in the wellbore is surrounded by a homogeneous formation having the resistivity of the first formation region, and determining how two of the electrodes have to be energized in order that in the target point the selected parameter has the target value; d) selecting a monitoring parameter at the monitoring electrode; e) placing the logging tool at the selected location in the wellbore; f) de

Abstract: Detecting in an earth formation (51) a boundary (56) between first and second formation regions (54, 55) having different resistivities, wherein the first formation region (54) is traversed by a wellbore, using a logging tool (60) provided with a number of electrodes (61, 62, 63) including a monitoring electrode (63), the method comprising: a) selecting a location (65) of the logging tool (60) in the wellbore (57); b) assuming a position of the boundary (56) relative to the selected location (65), selecting outside the wellbore (57) a target point (67) relative to the selected location (65), and selecting a target value for a selected parameter in the target point (67); c) assuming a model wherein the logging tool (60) in the wellbore is surrounded by a homogeneous formation having the resistivity of the first formation region (54), and determining how two of the electrodes (61, 62, 63) have to be energized in order that in the target point (67) the selected parameter has the target value; d) selecting a moni