Abstract: A downhole telemetry system and method using discrete multi-tone modulation having repeated symbols. The system includes a surface receiver, a cable, and a downhole transmitter coupled to the surface receiver via the cable. The transmitter communicates a time-domain signal to the receiver. The time-domain signal has a cyclic prefix for a symbol at least as long as the length of the symbol. The system may alternatively include the time-domain signal having a symbol followed immediately by a copy of the symbol. The method includes receiving a time-domain signal carrying desired information at specific frequencies. The signal has at least one symbol. The method includes prepending a cyclic prefix having first length to the beginning of the symbol. The cyclic prefix has a second length no longer than the first length. The method may alternatively include appending a copy of the at least one symbol to the end of the at least one symbol.

Abstract: An apparatus controls the operation of a hydrocarbon production well. The apparatus includes a supply means for providing an electric power supply. The apparatus also includes a plurality of electrically operated actuating devices. The actuating devices can be a plurality of electric motors. The apparatus includes drivers responsive to the power supply for providing a drive signal for the actuating devices. The apparatus also includes a control assembly for applying the drive signal to the actuating devices in a multiplexed manner. The power from each driver creates a power input signal. When there are more than one input signals, they are multiplexed so that a single signal is received by the actuating devices.

Abstract: A power transmission and data communications system for use in a gas or oil well borehole is disclosed. The borehole includes a casing and a piping structure therein and at least one downhole equipment module located therein. The system provides for a power signal to provide power transfer to downhole systems that require power and for data and control signals to be transmitted using orthogonal frequency division multiplexing (OFDM) to the downhole equipment located in the downhole equipment modules. In particular, the system provides for the data signal to be electrically coupled to the case and piping structure for transmission downhole to the downhole systems that are similarly coupled to the casing and piping structure. The downhole equipment includes a power supply that is operative to recover electrical power from the power signal and to provide output power to the other downhole equipment.

Abstract: A method and apparatus for wireless transmission of data through a communications channel between at least two local data sensors (for example automotive diagnostic data sensors or NVH sensors), which may include a primary data-processing function, and data-processing function (for example a PC) to receive data therefrom. The system provides for asymmetrical division of the communications channel on a frequency or time-division or packet-switching basis so that the corresponding asymmetrical data transmission requirement of the local data sensors are matched to the capacity of their respective sub-channels whereby a single channel is capable of transmitting all the required data. A particularly practical application is to noise vibration harshness analysis of wireless-transmitted data from three-dimensionally spaced NVH sensors enabling special pinpointing of vibration sources in automotive warranty analysis studies.

Abstract: A synchronous CDMA telemetry system is provided for use in a wellbore. In one described embodiment, each data bit of digital outputs of multiple downhole data sources is multiplied by an orthogonal code unique to each data source. The resulting encoded outputs are modulated on a carrier frequency and summed on a transmission channel. The resulting signal is demodulated at a remote location and separately multiplied by each of the codes to separate out the contributions to the signal from each data source. The individual demodulated and decoded outputs are then integrated over the length of each data bit.

Abstract: A system for sensing subterranean acoustic waves emitted from an acoustic source includes a plurality of laser sources, a plurality of subterranean optical sensors, at least one optical detector, and electronics. The laser sources each emit light at a different frequency. The subterranean optical sensors receive the light and alter the light in response to the acoustic waves. The optical detector receives the altered light and outputs an electrical signal. The electronics receives the electrical signal and converts it into seismic data format. The hydrophone for sensing the acoustic signals is able to operate at pressures of at least 5,000 psi and temperatures of at least 130 degrees Celsius. A hydrophone may be housed in a cable having a diameter of less than about 1.5 inches. The hydrophone's sensor preferably includes a reference mandrel, two sensing mandrels, and a telemetry can, all of which are aligned in a coaxial, end-to-end configuration to reduce the profile of the hydrophone.

Abstract: The present invention provides a tool assembly for use in field applications to monitor at least one condition in a well or other hole. The tool assembly may include a computing unit for directing operation of the tool assembly and may be sized to be operable in a hole having a diameter of 1 inch, and in some cases even smaller. In one aspect, the tool assembly is designed to significantly conserve power. Sensor readings may be taken at different schedules to conserve power when frequent readings are not required. Also, internal electronics of the tool assembly can be operated at a low voltage. In one aspect, the tool assembly is assemblable by simple rotatable engagement of the components, with electrical interconnections being made automatically by the rotatable engagement without keying of components. In another aspect, the tool assembly is networkable with other like tool assemblies and monitorable from a central location.

Abstract: A very high data rate telemetry system is provided for use in a wellbore. In a described embodiment, a telemetry system includes multiple nodes positioned in the wellbore and distributed over a substantial length of the wellbore. The nodes simultaneously communicate with a remote location at a very high combined data transmission rate. A method of communicating data in a wellbore is also provided. The method includes the steps of installing multiple modems in the wellbore, installing a remote modem at a location remote from the downhole modems, and simultaneously communicating data from each of the downhole modems to the remote location. Each downhole modem communicates with the remote modem using a unique set of frequency subchannels.

Abstract: A downhole telemetry system that transmits a burst-QAM uplink signal to the surface of the well is disclosed. In a preferred embodiment, a downhole instrument coupled to a pair of conductors in a wireline or composite tubing string transmits a burst-QAM uplink signal to a surface system. The burst-QAM signal preferably comprises a series of data frames carrying telemetry data. Each data frame is preferably preceded by a quiet interval (when no signal is present), a timing synchronization sequence, and a training sequence. The timing synchronization sequence is designed for easy timing recovery at the surface, and the training sequence is designed to aid the adaptation of the equalizer. The data frame itself preferably includes a synchronization field, a data count, and a checksum in addition to the data. Direct digital synthesis is preferably employed to modulate the uplink signal.

Abstract: A system for use with a well includes a surface device, a communications link coupled to the surface device and extending into the well, and a plurality of downhole devices coupled to different points on the communications link in the well. The surface device and the plurality of devices are adapted to determine distortions of different portions of the communications link coupling the surface device and downhole devices and to compensate for the distortions when communicating. Transfer characteristics of the communications link portions may be determined, from which equalization parameters may be determined to compensate for distortions caused by communications link portions.