A fail-safe method to cement a section of casing string to a formation is provided. The method includes providing the casing string in a wellbore, the casing string comprising a stage tool, a packer, and a sensor. The packer is located vertically below the stage tool and vertically above the sensor on the casing string. The method further includes pumping cement down the casing string and up an annulus to an expected height, the expected height being a vertical distance above the sensor, and detecting a presence or absence of cement with the sensor. If the sensor detects the presence of cement, the stage tool is kept closed and the packer is kept deflated. If the sensor detects the absence of cement, the stage tool is opened and the packer is inflated.

A fail-safe method to cement a section of casing string to a formation is provided. The method includes providing the casing string in a wellbore, the casing string comprising a stage tool, a packer, and a sensor. The packer is located vertically below the stage tool and vertically above the sensor on the casing string. The method further includes pumping cement down the casing string and up an annulus to an expected height, the expected height being a vertical distance above the sensor, and detecting a presence or absence of cement with the sensor. If the sensor detects the presence of cement, the stage tool is kept closed and the packer is kept deflated. If the sensor detects the absence of cement, the stage tool is opened and the packer is inflated.

A method for investigating well integrity, the method including pumping a magnetic fluid into an annulus of the well; magnetizing with a magnet the magnetic fluid while in the annulus of the well; moving a magnetic sensing probe through a casing of the well and recording a magnetic field generated by the magnetic fluid; and processing the recorded magnetic field to determine a distribution of magnetic particles into the magnetic fluid in the annulus.

A method for investigating well integrity, the method including pumping a magnetic fluid into an annulus of the well; magnetizing with a magnet the magnetic fluid while in the annulus of the well; moving a magnetic sensing probe through a casing of the well and recording a magnetic field generated by the magnetic fluid; and processing the recorded magnetic field to determine a distribution of magnetic particles into the magnetic fluid in the annulus.

Material properties between a wellbore and a casing having a partition separating respective domains inside and outside the casing are evaluated by disposing at least one ultrasonic transmitter and a plurality of ultrasonic receivers in longitudinally spaced-apart relationship alongside the partition inside the casing. The ultrasonic transmitter is activated to form ultrasonic waveforms comprising propagated quasi leaky-Lamb waves constituting flexural waves having symmetric and antisymmetric zero-order modes within the partition. A time-shift is applied to the received flexural waves so that the respective time-shifted waveforms corresponding to each of the flexural waves arrive at the same time. The time-shifted waveforms are clustered to form separate clusters respectively relating to a flexural wave part, and at least one post-flexural wave part which exposes characteristics that would otherwise be hidden behind more dominant features in the flexural wave and allowing determination of a material and geometry behind the partition.

Material properties between a wellbore and a casing having a partition separating respective domains inside and outside the casing are evaluated by disposing at least one ultrasonic transmitter and a plurality of ultrasonic receivers in longitudinally spaced-apart relationship alongside the partition inside the casing. The ultrasonic transmitter is activated to form ultrasonic waveforms comprising propagated quasi leaky-Lamb waves constituting flexural waves having symmetric and antisymmetric zero-order modes within the partition. A time-shift is applied to the received flexural waves so that the respective time-shifted waveforms corresponding to each of the flexural waves arrive at the same time. The time-shifted waveforms are clustered to form separate clusters respectively relating to a flexural wave part, and at least one post-flexural wave part which exposes characteristics that would otherwise be hidden behind more dominant features in the flexural wave and allowing determination of a material and geometry behind the partition.

A system for fluid monitoring in a borehole for extracting hydrocarbons includes a casing to transport hydrocarbons, the casing defining an annulus between the casing and borehole wall. The system further includes a centralizer, coupled to the casing, to center the casing within the borehole. The system further includes a sensor unit, including a radio frequency identification (RFID) interrogator, positioned on the centralizer to monitor one or more fluids, including RFID tags, in the annulus.

A downhole sensor deployment assembly includes a body attachable to a completion string and one or more arms pivotably coupled to the body. A sensor pad is coupled to each arm and movable from a retracted position, where the sensor pad is stowed adjacent the completion string, and an actuated position, where the sensor pad is extended radially away from the completion string. One or more actuators are pivotably coupled to the body at a first end and pivotably coupled to a corresponding one of the one or more arms at a second end, the one or more actuators being operable to move the sensor pad to the actuated position. One or more sensor devices are coupled to the sensor pad for determining a resistivity of a formation, the one or more sensor devices comprising at least one of a sensing electrode, a transceiver, and a transmitter.

A system that is positionable in a wellbore in a subterranean formation can include a first transceiver that is positionable external to a casing string in the wellbore. The first transceiver can wirelessly transmit data via a signal within a frequency band that is selected based on a fluid property of a fluid in the wellbore and a property of the subterranean formation. The system can also include a second transceiver that is positionable externally

A system for use in a wellbore can include a first transceiver that is operable to transmit a wireless signal. The first transceiver can be positioned in an electrically isolated chamber between a tubular and a casing string for confining a transmission of the wireless signal to within the electrically isolated chamber. The system can also include a second transceiver that is positionable in the electrically isolated chamber for receiving the wireless signal from the first transceiver.