Abstract: An apparatus and method for a temperature compensated pressure gauge for downhole use based on Fiber Bragg Gratings (FBGs). The apparatus and method results in FBG measurements that can be interrogated with higher resolution and higher accuracy than from previous methods with the additional benefit of being less sensitive to error-inducing drift factors such as FBG thermal degradation and hydrogen.

Abstract: A method using a capstan device and different bonding methods for minimizing undesirable time-dependent effects that occur in sensing devices that use optical fibers placed in tension.

Abstract: Various embodiments include apparatus and methods structured to interrogate a plurality of sensor assemblies, where each sensor assembly may have one or more transmissive optical sensors. The plurality of sensor assemblies can be arranged to couple between two optical fibers. The interrogation can include generating optical signals to each sensor assembly such that each sensor assembly can be selectively and individually interrogated using semiconductor optical amplifiers. Additional apparatus, systems, and methods are disclosed.

Abstract: Gravity surveys of subterranean formations may be based on the simultaneous measurement of gravity and its derivatives to produce a higher resolution formation map or wellbore log.

Abstract: A distributed optical fiber sensing system is provided. The system can include an interrogator, a transmission optical fiber, a sensing optical fiber, and a reflector. Each of the transmission optical fiber and the sensing optical fiber includes at least one circulator. The reflector is optically coupled to the transmission optical fiber for sensing separate regions along the sensing optical fiber.

Abstract: A disclosed example embodiment includes a composite slickline cable having an optical fiber with optimized residual strain. The composite slickline cable includes a fiber reinforced polymer and at least one optical fiber disposed within the fiber reinforced polymer such that axial stress applied to the composite slickline cable is shared by the at least one optical fiber and the fiber reinforced polymer. In the axially unstressed state of the composite slickline cable, the at least one optical fiber has a residual strain between about ?1,000 microstrain and about 500 microstrain.

Abstract: An apparatus and method for a temperature compensated pressure gauge for downhole use based on Fiber Bragg Gratings (FBGs). The described apparatus and method results in FBG measurements that can be interrogated with higher resolution and higher accuracy than from previous methods with the additional benefit of being less sensitive to error-inducing drift factors such as FBG thermal degradation and hydrogen.

Abstract: A disclosed example embodiment includes a composite slickline cable having an optical fiber with optimized residual strain. The composite slickline cable includes a fiber reinforced polymer and at least one optical fiber disposed within the fiber reinforced polymer such that axial stress applied to the composite slickline cable is shared by the at least one optical fiber and the fiber reinforced polymer. In the axially unstressed state of the composite slickline cable, the at least one optical fiber has a residual strain between about ?1,000 microstrain and about 500 microstrain.

Abstract: A distributed optical fiber sensing system is provided. The system can include an interrogator, a transmission optical fiber, a sensing optical fiber, and a reflector. Each of the transmission optical fiber and the sensing optical fiber includes at least one circulator. The reflector is optically coupled to the transmission optical fiber for sensing separate regions along the sensing optical fiber.

Abstract: Various embodiments include apparatus and methods structured to interrogate a plurality of sensor assemblies, where each sensor assembly may have one or more transmissive optical sensors. The plurality of sensor assemblies can be arranged to couple between two optical fibers. The interrogation can include generating optical signals to each sensor assembly such that each sensor assembly can be selectively and individually interrogated using semiconductor optical amplifiers. Additional apparatus, systems, and methods are disclosed.

Abstract: Sensors, systems and methods for downhole electromagnetic field detection, including a downhole micro-opto-electro-mechanical system (MOEMS) electromagnetic field sensor that includes a first surface that is at least partially reflective, a second surface that is at least partially reflective and suspended by one or more flexible members to define an optical cavity having a variable distance between the first and second surfaces, and a first conductive layer attached to the second surface and having a first electric charge. An electric field passing through the optical cavity interacts with the first electric charge and displaces the second surface to alter the variable distance and cause a spectrum variation in light exiting the sensor.

Abstract: Sensors, systems and methods for downhole electromagnetic field detection, including a downhole micro-opto-electro-mechanical system (MOEMS) electromagnetic field sensor that includes a first surface that is at least partially reflective, a second surface that is at least partially reflective and suspended by one or more flexible members to define an optical cavity having a variable distance between the first and second surfaces, and a magnetically polarized layer attached to the second surface. A magnetic field passing through the optical cavity interacts with the magnetically polarized layer and a gradient in the magnetic field produces a displacement of the second surface that alters the variable distance and causes a spectrum variation in light exiting 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: Sensors, systems and methods for downhole electromagnetic field measurement, including a downhole micro-opto-electro-mechanical system (MOEMS) electromagnetic field sensor that includes a first surface that is at least partially reflective, a second surface that is at least partially reflective and suspended by one or more flexible members to define an optical cavity having a variable distance between the first and second surfaces, a first conductive layer attached to the first surface, and a second conductive layer attached to the second surface. The first and second conductive layers have an electrical potential proportional to an electromagnetic field within a formation surrounding the sensor. The electrical potential produces an electric field that displaces the second surface to alter the variable distance and cause a spectrum variation in light exiting the sensor.

Abstract: Sensors, systems and methods for downhole electromagnetic field measurement, including a downhole micro-opto-electro-mechanical system (MOEMS) electromagnetic field sensor that includes a first surface that is at least partially reflective, a second surface that is at least partially reflective and suspended by one or more flexible members to define an optical cavity having a variable distance between the first and second surfaces, a first conductive layer attached to the first surface, and a second conductive layer attached to the second surface. The first and second conductive layers have an electrical potential proportional to an electromagnetic field within a formation surrounding the sensor. The electrical potential produces an electric field that displaces the second surface to alter the variable distance and cause a spectrum variation in light exiting the sensor.

Abstract: Sensors, systems and methods for downhole electromagnetic field detection, including a downhole micro-opto-electro-mechanical system (MOEMS) electromagnetic field sensor that includes a first surface that is at least partially reflective, a second surface that is at least partially reflective and suspended by one or more flexible members to define an optical cavity having a variable distance between the first and second surfaces, and a magnetically polarized layer attached to the second surface. A magnetic field passing through the optical cavity interacts with the magnetically polarized layer and a gradient in the magnetic field produces a displacement of the second surface that alters the variable distance and causes a spectrum variation in light exiting the sensor.

Abstract: A method using a capstan device and different bonding methods for minimizing undesirable time-dependent effects that occur in sensing devices that use optical fibers placed in tension.

Abstract: A system includes an optical source. The system further includes a reflective sensor remotely deployed from the optical source. The system further includes an optical processor. The system further includes a forward optical waveguide spanning the distance from, and transmitting light from, the optical source to the reflective sensor. The system further includes a return optical waveguide spanning the distance from, and transmitting light from, the reflective sensor to the optical processor. The forward optical waveguide follows substantially the same path as, but is completely separate from, the return optical waveguide.