Abstract:
One or more seals may be provided in a gap sub to prevent the ingress of drilling fluid into an insulating gap between a male member of the gap sub and a female member of the gap sub. A first seal may comprise an internal gap sub seal provided near the tip of the male member of the gap sub. A second seal may comprise an external gap sub seal provided near the tip of the female member of the gap sub. The first and second seals may comprise non-conductive materials. The first and second seals may each comprise one or more O-rings. The first and second seals may comprise one or more lips, protrusions or flanges to engage the male and/or female members of the gap sub for maintaining contact with the male and/or female members during deformation of the gap sub.
Abstract:
A gap sub assembly for electromagnetic telemetry used in downhole drilling is disclosed. The gap sub comprises a female part comprising a female mating section and a male part comprising a male mating section. The male mating section is matingly received within the female mating section and electrically isolated therefrom. One or more electrically insulating bodies secure the male part axially and torsionally relative to the female part. The electrically insulating bodies also electrically isolate the male part from the female part. The electrically insulating bodies can be installed through apertures in the female part or at least some of the electrically insulating bodies can be installed before the male mating section is inserted into the female mating section. The electrically insulating bodies can be held in place on the male mating section using a retention apparatus such as a ring, a scarf, pods or an adhesive.
Abstract:
An electromagnetic telemetry system adjusts telemetry parameters which may include carrier frequency, signal amplitude and/or data encoding protocol to achieve reliable data transmission and to conserve power. In some embodiments, sweep signals transmit a range of carrier frequencies and the parameters are determined in part by analyzing the received sweep signals. In some embodiments, different parameters are selected automatically based on a mode of drilling.
Abstract:
The embodiments described herein generally relate to a method and apparatus for providing a back up system of Directional and Inclination (D&I) information to be gathered and transmitted in addition to primary D&I sensors currently employed in industry. A downhole probe assembly including primary sensors, back up sensors and a controller is disclosed. The primary sensors comprise primary accelerometers and primary magnetometers configured to gather information relating to each of orthogonal axes X, Y and Z. The back up sensors comprise back up accelerometers configured to gather information relating to each of orthogonal axes X, Y and Z, the back up accelerometers being solid state accelerometers. The controller is in electrical communication with the primary sensors and the back up sensors. The controller is configured to receive and process information from the primary sensors and the back up sensors so that information from the back up accelerometers can be used when one or more of the primary accelerometers fail, which may allow drilling operations to continue despite such failure.
Abstract:
An electromagnetic telemetry system adjusts telemetry parameters which may include carrier frequency, signal amplitude and/or data encoding protocol to achieve reliable data transmission and to conserve power. In some embodiments, sweep signals transmit a range of carrier frequencies and the parameters are determined in part by analyzing the received sweep signals. In some embodiments, different parameters are selected automatically based on a mode of drilling.
Abstract:
An electromagnetic telemetry signal generating assembly comprises a first section of drill string, a second section of drill string, a gap sub configured to insulate the first section from the second section, and a power source configured to provide a first voltage to a control circuit. The control circuit is configured to drive a second voltage between the sections of drill string. The gap sub provides a gap of at least 12 inches (30 cm). The second voltage may be different than the first voltage.
Abstract:
A downhole system comprises a main sensor, such as a gamma sensor, and a backup sensor. The backup sensor may be of a different type from the main sensor. In some embodiments the backup sensor is a high reliability sensor that may have a different sensitivity from the main sensor. The system operates both the main and backup sensors and generates calibration data for the backup sensor. If the main sensor fails the calibration data may be applied to process data from the backup sensor to yield an estimate of the data that the main sensor would have yielded if it had remained operational. The calibration data may compensate for temperature variations and/or temporal drift, for example.
Abstract:
A range of apparatus and methods for providing local and long range data telemetry within a wellbore is described. These apparatus and methods may be combined in a wide variety of ways. In some embodiments data is transmitted across a gap in a drill string using signals of a higher frequency for which an electrical impedance of the gap or of a filter connected across the gap is low. Low-frequency EM telemetry signals may be applied across the gap. The gap and any filter connected across the gap present a high impedance to the low-frequency EM telemetry signals. The described technology may be applied for transferring sensor readings between downhole electrical packages. In some embodiments sensors are electrically connected across electrically insulating gaps in the drill string.
Abstract:
An insulating collar for a gap sub assembly for electromagnetic (EM) telemetry used in downhole drilling is disclosed. The gap sub assembly comprises a female member comprising a female mating section and a male member comprising a male mating section and a gap section. The male mating section is matingly received within the female mating section and electrically isolated therefrom. The insulating collar is positioned on the gap section. The collar is made up of a framework with a plurality of discrete bodies spaced about the framework and a portion of each of the discrete bodies protrudes above the framework. Either the framework or the discrete bodies are made of an electrical insulator material to electrically isolate one end of the collar from the other end of the collar. The collar therefore electrically isolates the male member from the female member and the male member, female member and insulating collar function as the “gap sub” for EM telemetry.
Abstract:
An electromagnetic telemetry system adjusts telemetry parameters which may include carrier frequency, signal amplitude and/or data encoding protocol to achieve reliable data transmission and to conserve power. In some embodiments, sweep signals transmit a range of carrier frequencies and the parameters are determined in part by analyzing the received sweep signals. In some embodiments, different parameters are selected automatically based on a mode of drilling.