Abstract: A downhole telemetry system having discrete multi-tone modulation and dynamic bandwidth allocation is disclosed herein. In one embodiment, the downhole telemetry system comprises a surface transceiver, a cable, and a downhole transceiver coupled to the surface transceiver via the cable. The downhole transceiver communicates to the surface transceiver using discrete multi-tone (DMT) modulation to transmit telemetry information over a set of frequency subchannels allocated for uplink communications. The surface transceiver may likewise communicate to the downhole transceiver using DMT modulation to transmit information over a set of frequency subchannels allocated for downlink communications. The number of uplink and downlink communications subchannels is preferably variable and preferably can be changed depending on the operating mode of the system.

Abstract: A system and method for downhole power delivery. In one embodiment, the system delivers computer-regulated downhole power voltages, and may be configured to customize signal waveforms and power allocation on the various independent signal transmission modes to maximize the power capacity of the logging cable subject to its maximum voltage rating. In one embodiment, the system includes a standard multiconductor logging cable which supports orthogonal signal transmission modes on circumferentially spaced insulated conductors. A high-power power source on the surface is coupled to the insulated conductors in the cable to drive a power signal on the lowest impedance signal transmission mode. The system may further include multiple power sources operating on different independent signal transmission modes, and may also include multiple telemetry channels which share the power transmission modes via frequency multiplexing.

Abstract: A system and method is described for safely and economically providing up to 1800 watts to downhole equipment over existing logging cables. In one embodiment, the system includes a standard multiconductor logging cable which supports orthogonal signal transmission modes on circumferentially spaced insulated conductors. A high-power power source on the surface is coupled to the insulated conductors in the cable to drive a power signal on the lowest impedance signal transmission mode. Bearing in mind that high-power electrical currents can present a safety hazard, system safety may be enhanced by the addition of a reliable current imbalance detector configured to shut down all power sources when currents in the insulated conductors don't add up to zero. The system may further include multiple power sources operating on different independent signal transmission modes, and may also include multiple telemetry channels which share the power transmission modes via frequency multiplexing.

Abstract: A digital communications system employing modulated Walsh functions to convey data across a communications channel. In one embodiment, the system includes a transmitter having a constellation encoder, and a Walsh constellation modulator. The constellation encoder receives a sequence of data words and converts it into a sequence of constellation signal point labels. The modulator receives the sequence of labels, and responsively generates one or more amplitude-modulated Walsh functions which are summed to produce a modulated signal. The modulated signal passes through a communications channel to a receiver. The receiver includes an analog-to-digital converter (ADC) and a demodulation circuit. The ADC oversamples the received signal. The demodulation circuit manipulates the sign of the samples to effectively multiply the received samples with one or more Walsh functions, and sums the resulting values over one symbol interval to determine the modulated amplitude of the corresponding functions.

Abstract: A downhole telemetry system having discrete multi-tone modulation and dynamic bandwidth allocation is disclosed herein. In one embodiment, the downhole telemetry system comprises a surface transceiver, a cable, and a downhole transceiver coupled to the surface transceiver via the cable. The downhole transceiver communicates to the surface transceiver using discrete multi-tone (DMT) modulation to transmit telemetry information over a set of frequency subchannels allocated for uplink communications. The surface transceiver may likewise communicate to the downhole transceiver using DMT modulation to transmit information over a set of frequency subchannels allocated for downlink communications. The number of uplink and downlink communications subchannels is preferably variable and preferably can be changed depending on the operating mode of the system.

Abstract: A well tool for developing measurements of pressure or temperature in a well bore comprising an elongated well tool which utilizes a coherent beam of light which is applied to the ends of separate fiber optics and the other ends of the fiber optics are detected to produce an electrical signal in response to differences between the outputs of the fiber optics to the detector. For measuring pressure, one fiber optic may be coiled in a temperature insulated chamber and sense a discrete sample from the earth formations while the other fiber optic is coiled in a temperature insulated reference pressure chamber. In another embodiment both fiber optics are subjected to pressure samples from longitudinally spaced locations of the earth formations. In still another embodiment, the fiber optics are subjected to the temperature in the bore hole at longitudinally spaced locations for obtaining a temperature gradient measurement.

Abstract: In situ measurement of the gas content of formation fluid using thermal expansion principles. The formation fluid from a wellbore source is passed through an expansion type valve into a test chamber. The temperature and pressure are measured upstream and downstream of the valve. The difference in the temperature measurement is an indicator of gas content in the formation fluid. Samples of the formation fluid can be taken on favorable indicators.

Abstract: An acoustic well logging system is provided for measuring the speed of propagation of all acoustic wave propagation modes of earth formations penetrated by a borehole simultaneously. A linearly changing frequency swept acoustic signal is generated and received at a spaced distance apart in a borehole. The received signal is mixed in a product forming device with the transmitted signal. Mixer product signals are low pass filtered to remove high frequency components and the resultant signals spectrum analyzed. Frequency spectra components may then be interpreted directly in terms of speed of propagation of various acoustic energy wave propagation modes.

Abstract: An improved means of closure comprising in combination two formed adjoining unextended co-members, such as the ends of a grommet, and a third formed resilient locking member pivotally mounted on one of the two formed adjoining unextended co-members.