Abstract: The water cut of a fluid used or produced in conjunction with wellbore operations may be measured or otherwise estimated using an ion selective fiber sensor. For example, a method may include flowing a fluid comprising an aqueous phase and an oleaginous phase through a sensor; contacting an ion selective fiber positioned in the sensor with the fluid, wherein the ion selective fiber has an intrinsic time constant (?0) associated with an intrinsic color change of the ion selective fiber in response to contact with the aqueous phase; measuring a color change of the ion selective fiber in response to contact with the fluid as a function of time; deriving an effective time constant (?eff) for the color change of the ion selective fiber in response to contact with the fluid; and calculating a water cut (Y) in the fluid based on Y = ? 0 ? eff .

Abstract: The water cut of a fluid used or produced in conjunction with wellbore operations may be measured or otherwise estimated using an ion selective fiber sensor. For example, a method may include flowing a fluid comprising an aqueous phase and an oleaginous phase through a sensor; contacting an ion selective fiber positioned in the sensor with the fluid, wherein the ion selective fiber has an intrinsic time constant (?0) associated with an intrinsic color change of the ion selective fiber in response to contact with the aqueous phase; measuring a color change of the ion selective fiber in response to contact with the fluid as a function of time; deriving an effective time constant (?eff) for the color change of the ion selective fiber in response to contact with the fluid; and calculating a water cut (Y) in the fluid based on Y = ? 0 ? eff .

Abstract: A disclosed subsurface electromagnetic field monitoring system includes at least one fiberoptic cable to optically communicate measurements from an array of electromagnetic field sensors in a borehole. The array of electromagnetic field sensors includes a distributed feedback fiber laser strain sensor with electromagnetic field sensitivity.

Abstract: A method of flowing fluid from a formation, the method comprising: sensing presence of a reservoir impairing substance in the fluid flowed from the formation; and automatically controlling operation of at least one flow control device in response to the sensing of the presence of the substance. A well system, comprising: at least one sensor which senses whether a reservoir impairing substance is present; and at least one flow control device which regulates flow of a fluid from a formation in response to indications provided by the sensor.

Abstract: Fiberoptics can be employed to detect downhole electromagnetic signals via resistive heating. A disclosed electromagnetic energy detector embodiment includes an optically-interrogated temperature sensor; and a conductive element thermally coupled to the sensor, the conductive element having a temperature response to incident electromagnetic energy. The optically-interrogated temperature sensor may be a length or coil of optical fiber to which a distributed acoustic sensing (DAS) or distributed temperature sensing (DTS) system is attached. The conductive element may be a metal coating on the fiber that experiences resistive heating in response to electromagnetic energy and creates an optically-measurable thermal response in the sensor.

Abstract: A formation monitoring system includes a casing. An array of electromagnetic field sensors is positioned in the annular space and configured to communicate with the surface via a fiberoptic cable. A computer coupled to the fiberoptic cable receives measurements from the array and responsively derives the location of any fluid fronts in the vicinity such as an approaching flood front to enable corrective action before breakthrough. A formation monitoring method includes: injecting a first fluid into a reservoir formation; producing a second fluid from the reservoir formation via a casing in a borehole; collecting electromagnetic field measurements with an array of fiberoptic sensors in an annular space, the array communicating measurements to a surface interface via one or more fiberoptic cables; and operating on the measurements to locate a front between the first and second fluids.

Abstract: A disclosed subsurface electromagnetic field monitoring system includes at least one fiberoptic cable to optically communicate measurements from an array of electromagnetic field sensors in a borehole.

Abstract: A disclosed formation monitoring system includes a casing that defines an annular space within a borehole. An array of electromagnetic field sensors is positioned in the annular space and configured to communicate with the surface via a fiberoptic cable. A computer coupled to the fiberoptic cable receives said measurements and responsively derives the location of any fluid fronts in the vicinity such as a an approaching flood front to enable corrective action before breakthrough. A disclosed formation monitoring method includes: injecting a first fluid into a reservoir formation; producing a second fluid from the reservoir formation via a casing in a borehole; collecting electromagnetic field measurements with an array of fiberoptic sensors in an annular space between said casing and said borehole, said array communicating measurements to a surface interface via one or more fiberoptic cables; and operating on said measurements to locate a front between the first and second fluids.

Abstract: Fiberoptics can be employed to detect downhole electromagnetic signals via resistive heating. A disclosed electromagnetic energy detector embodiment includes an optically-interrogated temperature sensor; and a conductive element thermally coupled to the sensor, the conductive element having a temperature response to incident electromagnetic energy. The optically-interrogated temperature sensor may be a length or coil of optical fiber to which a distributed acoustic sensing (DAS) or distributed temperature sensing (DTS) system is attached. The conductive element may be a metal coating on the fiber that experiences resistive heating in response to electromagnetic energy and creates an optically-measurable thermal response in the sensor.

Abstract: Various systems and methods for cementing plug tracking using distributed strain sensing include a downhole cementing apparatus that includes a distributed strain sensor with an optical cable and a first downhole cementing plug coupled to a fixed point on the optical cable. The apparatus further includes a second downhole cementing plug slidably coupled to the optical cable between the first downhole cementing plug and a sensing end of the optical cable. The second downhole cementing plug causes a detectable feature in a strain profile along the optical cable's length that indicates a position of the second downhole cementing plug.

Abstract: A method of flowing fluid from a formation, the method comprising: sensing presence of a reservoir impairing substance in the fluid flowed from the formation; and automatically controlling operation of at least one flow control device in response to the sensing of the presence of the substance. A well system, comprising: at least one sensor which senses whether a reservoir impairing substance is present; and at least one flow control device which regulates flow of a fluid from a formation in response to indications provided by the sensor.

Abstract: A system is disclosed for measuring strain using a technique of detecting the optical path difference in a sensing interferometer using an interrogating interferometer including a chirped fiber Bragg grating in which the optical path difference in the sensing interferometer is changed with the strain in the sensing arm, whereas the optical path difference of the interrogating interferometer is changed only by changing the center wavelength of addressing light, making use of the wavelength-dependency on the penetration depth inside the chirped fiber Bragg grating interferometer. Consequently, strain in the sensing interferometer can be assessed by determining the wavelength in which a coherence matched condition between the sensing and interrogation interferometers is attained.

Abstract: An exchange length guidewire for use in percutaneous transluminal coronary angioplasty is formed in two sections including a proximal section and a distal section. The proximal end of the distal section is rotatably attached to the distal end of the proximal section so that it may be rotated freely with respect to the proximal section. The proximal section may be maintained in a coiled configuration in a storage hoop while the distal portion may be used as a steerable guidewire to assist in navigating a catheter to the intended vascular treatment site. When it is desired to perform a catheter exchange, the proximal section is removed from the storage hoop to permit the wire to extend to its full exchange length, typically slightly more than twice the length of the catheter. The catheter exchange then may be performed. Thereafter, the proximal section of the exchange wire may be reinserted into the storage hoop and while the distal portion may continue to serve as a steerable guidewire.