An untethered apparatus for measuring properties along a subterranean well includes a housing, and one or more sensors configured to measure data along the subterranean well. The data includes one or more physical, chemical, geological or structural properties in the subterranean well. The untethered apparatus further includes a processor configured to control the one or more sensors measuring the data and to store the measured data, and a transmitter configured to transmit the measured data to a receiver arranged external to the subterranean well. Further, the untethered apparatus includes a controller configured to control the buoyancy or the drag of the untethered apparatus to control a position of the untethered apparatus in the subterranean well. The processor includes instructions defining measurement parameters for the one or more sensors of the untethered apparatus within the subterranean well.

An untethered apparatus for measuring properties along a subterranean well includes a housing, and one or more sensors configured to measure data along the subterranean well. The data includes one or more physical, chemical, geological or structural properties in the subterranean well. The untethered apparatus further includes a processor configured to control the one or more sensors measuring the data and to store the measured data, and a transmitter configured to transmit the measured data to a receiver arranged external to the subterranean well. Further, the untethered apparatus includes a controller configured to control the buoyancy or the drag of the untethered apparatus to control a position of the untethered apparatus in the subterranean well. The processor includes instructions defining measurement parameters for the one or more sensors of the untethered apparatus within the subterranean well.

Some embodiments of the inventive subject matter improve techniques for measuring downhole attributes. A method for determining a flow rate of a fluid includes positioning a tubular within a wellbore formed in a subsurface formation, wherein a flow of fluid is to move through the tubular. An orifice plate is positioned in the tubular. The orifice plate is movable between a first position and a second position to alter a flow area of the flow of fluid moving through the tubular. The method includes detecting a change in a downhole attribute that changes in response to the alteration of the flow area of the flow of fluid. Sensors positioned within or in communication with an interior of the tubular can detect the change in the downhole attribute. The method further includes determining a flow rate of the flow of fluid based on the detected change in the downhole attribute.

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.

A communication system that is positionable in a wellbore can include a first transceiver positioned externally to a casing string. The first transceiver can be operable to detect a presence or an absence of a surface wave; determine a location of a fluid in the wellbore based on the presence or the absence of the surface wave; and transmit data indicative of the location to a second transceiver. The surface wave can include an electromagnetic wave that has a magnetic field or an electric field that is non-transverse to a direction of propagation of the surface wave. The communication system can also include the second transceiver, which can be positioned externally the casing string and operable to receive the data.

Described herein are tools, systems, and methods for detecting, classifying, and/or quantifying underground fluid flows based on acoustic signals emanating therefrom, using a plurality of acoustic sensors disposed in the wellbore in conjunction with array signal processing and systematic feature-based classification and estimation methods.

A system for use in a wellbore can include a component that is positioned in a flow path through a tubular for fluid. The component can be movable by the fluid between a first position and a second position for changing a magnitude of a magnetic field that is detectable by a sensor or inducing a current in the sensor. The system can also include the sensor positioned external to the tubular for determining a direction of a flow of the fluid through the tubular based on the magnitude of the magnetic field or a polarity of the current.

The present disclosure is directed to articles that include one or more coated fiber(s) (i.e., fiber(s) with a cured coating disposed thereon), where the coating includes a matrix of crosslinked polymers and optionally a colorant (e.g., pigment particles or dye or both). The cured coating is a product of crosslinking a coating composition including uncrosslinked polymers (e.g., a dispersion of uncrosslinked polymers in a carrier, wherein the uncrosslinked polymers are crosslinked to form the matrix of crosslinked polymers). The present disclosure is also directed to articles including the coated fibers, methods of forming the coated fibers and articles, and methods of making articles including the coated fibers.

Monitoring and diagnosing completion during hydraulic fracturing operations provides insights into the fracture geometry, inter-well frac hits and connectivity. Conventional monitoring methods (microseismic, borehole gauges, tracers, etc.) can provide a range of information about the stimulated rock volume but may often be limited in detail or clouded by uncertainty. Utilization of DAS as a fracture monitoring tool is growing, however most of the applications have been limited to acoustic frequency bands of the DAS recorded signal. In this paper, we demonstrate some examples of using the low-frequency band of Distributed Acoustic Sensing (DAS) signal to constrain hydraulic fracture geometry. DAS data were acquired in both offset horizontal and vertical monitor wells. In horizontal wells, DAS data records formation strain perturbation due to fracture propagation. Events like fracture opening and closing, stress shadow creation and relaxation, ball seat and plug isolation can be clearly identified. In vertical wells, DAS response agrees well with co-located pressure and temperature gauges, and illuminates the vertical extent of hydraulic fractures. DAS data in the low-frequency band is a powerful attribute to monitor small strain and temperature perturbation in or near the monitor wells. With different fibered monitor well design, the far-field fracture length, height, width, and density can be accurately measured using cross-well DAS observations.