Abstract:
In-situ calibration of a resistivity logging tool is accomplished using a variety of methods in which deep measurement signals are calibrated using acquired and simulated measurement signals.
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:
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:
A method and a system for providing electromagnetic measurement in a rock formation are provided. The system includes a borehole casing (50B) having a plurality of casing segments (52B). At least two casing segments (53B) of the plurality of casing segments are electrically isolated from each other. The system further includes an electromagnetic source (71A-C) positioned on a surface of the earth. The electromagnetic source is connected to the at least two casing segments. The electromagnetic source is configured to energize the at least two casing segments so as to generate an electromagnetic field in the rock formation around the borehole casing.
Abstract:
A system for ranging between two wellbores where an emitter electrode and return electrode of a current injection system are disposed to drive a current to a conductive member within a target wellbore to create an electromagnetic field about the conductive member. The electromagnetic field is measured utilizing a sensor disposed in an investigative wellbore, which may be in the process of being drilled. In some embodiments, the emitter electrode and return electrode are positioned on the surface of a formation, spaced apart from one another with locations on the surface selected to optimize current, and therefore, the electromagnetic field, at a desired point along the conductive member. In some embodiments, one or both of the emitter electrode and return electrode are positioned in the target wellbore.
Abstract:
Systems and methods for obtaining deep resistivity measurements are described herein. The method may include obtaining first formation data from a first borehole within a formation. The method may further include obtaining second formation data from a drilling assembly disposed in a second borehole. In certain embodiments, the drilling assembly may comprise a drill bit and a measurement-while-drilling (MWD) or logging while drilling (LWD) assembly, and may be actively drilling the second borehole. The second formation data may correspond to a portion of the formation ahead of and around the drill bit. The first formation data and the second formation data may be correlated to identify a formation characteristic. The method may further include altering an operating condition of the drilling assembly based, at least in part, on the formation characteristic.
Abstract:
A method of measuring an electromagnetic field in a formation can include installing an electromagnetic sensor with improved sensitivity, the sensor including multiple optical waveguides and respective multiple materials, and in response to exposure to the electromagnetic field, the materials changing shape in opposite directions. A well system can include an optical electromagnetic sensor which measures an electromagnetic field in a formation, and wherein optical path lengths or phases in optical waveguides of the sensor change both positively and negatively in response to exposure to the electromagnetic field. A method of monitoring a formation can include installing an optical electromagnetic sensor in a wellbore which penetrates the formation, and an optical path length/phase in an optical waveguide of the sensor increasing in response to exposure to the electromagnetic field, and an optical path length/phase in another optical waveguide of the sensor decreasing in response to exposure to the electromagnetic field.
Abstract:
A fracture sensing system and method is disclosed herein. The method may include positioning a transmitter and a receiver in a borehole and magnetizing a casing disposed within the borehole to magnetically saturate the casing. The transmitter and receiver may be located inside or outside of the casing. The method may also include inducing with the transmitter an electromagnetic field in a formation surrounding the borehole. The method may also comprise receiving the induced electromagnetic field at the receiver. The induced electromagnetic field may identify a fracture within the formation based, at least in part, on a contrast agent within the fracture.
Abstract:
A system (50) enables a borehole casing (60) to be used to connection with establishing electromagnetic fields within the earth at the depth of formations of interest over a significant surface area. A particular advantage is that a borehole casing (60) can be used as an essential part of the system (50), without needing to open the borehole.
Abstract:
Various embodiments include apparatus and methods to provide a skin- effect correction. The skin-effect correction can be based on a pre-calculated correction coefficient library. In various embodiments, a skin-effect correction procedure can be applied that only uses a single-frequency R-signal measurement. In addition, an embodiment of a skin-effect correction procedure using a single- frequency R-signal measurement can be applied whenever the quality of the data from one of the multiple frequencies normally used in a multi- frequency method is reliable. Additional apparatus, systems, and methods are disclosed.