Schlumberger Technology Corporation

Jimmy Everett Neeley

Terry L Mayhugh

Michael Andrew Montgomery

Guy P Vachon

Chanchai Poonpol

Lloyd D Clark, Jr

David Lewis Lyon

Bart J Bombay

Marvin W Rasmussen

Terry L Mayhugh, Jr

A method and apparatus for transmitting and receiving acquired digital data over bandpass channels (i.e. channels having a limited range of frequencies) at high data transmission rates. Combined amplitude and phase modulation (quadrature amplitude modulation) is applied to the digital data and the sampled digital waveform converted to an analog waveform for passage over the bandpass channel. The sample rate is chosen as an integer multiple of the symbol rate and carrier frequency to significantly reduce processing overhead. Reception of the acquired data is similar to transmission and involves an analogous amplitude and phase demodulation. The quadrature amplitude modulation technique of the present invention is applied to an oil well-logging application to transmit the data acquired from the downhole logging instruments over the logging cable (bandpass channel) at high transmission rates.

Method and apparatus for transmitting and receiving digital data over a bandpass channel

Method and apparatus for transmitting and receiving digital data over a

A method and apparatus for predicting the peak voltage at the load end of a power transmission cable having a power supply end and a load end, where direct measurement at the load end is not practical. The method samples the current and voltage waveforms at the power supply end of the cable. The current waveform is used to estimate a current function which includes a full width at half maximum and adjustments for cable reactive current, distortions, and load. The product of the current function and a peak voltage sample from the power supply end is an estimate of the peak voltage at the load end. The method and apparatus have been applied to oil well logging where one or more logging tools are lowered at the end of a transmission cable into an oil well and it is desirable to predict peak voltage at the tools to ensure proper tool performance. An important improvement is a more accurate current function which compensates for capacitive current flow in the cable and includes a quadratic term. Additional improvements are described, namely a method for predicting downhole current, adjustments for power supply distortions, and diagnostic metrics.

Method and apparatus for predicting peak voltage of a cable conveyed tool

A method and apparatus for predicting the peak voltage at the load end of a power transmission cable having a power supply end and a load end, where direct measurement at the load end is not practical. The method samples the current and voltage waveforms at the power supply end of the cable. The current waveform is used to estimate a current function which includes a full width at half maximum approximation adjusted as required for load, cable type, and cable length. The product of the current function and a peak voltage sample from the power supply end is an estimate of the peak voltage at the load end. The method and apparatus have been applied to oil well logging where one or more logging tools are lowered at the end of a transmission cable into an oil well and it is desirable to predict peak voltage at the tools to ensure proper tool performance.

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Georgetown, TX, United States of America

Jimmy Everett Neeley