Optimal borehole communication using multicarrier modulation
Johnson, Don H.
Doctor of Philosophy
Transmission of down-hole measurements to the surface while the oil well is being drilled (logging while drilling-LWD-telemetry) is the key to the efficient and successful recovery of hydrocarbon resources. The most promising method of telemetry uses compressional acoustic waves to transmit data along the drillstring. In this technique, telemetry signals are encoded as acoustic wave pulses that propagate through the drillstring and are subsequently received and converted back to electric signals for data recovery at the surface receiver. Based on the analysis of the wave propagation properties in the drillstring, I propose and design an acoustic orthogonal frequency division multiplexing (OFDM) transmission scheme to efficiently communicate through the channel. To prove the feasibility of the proposed communication technique, numerous field tests were successfully designed and implemented in various drilling oil rigs. Then I characterize the performance of the oil well telemetry system and propose a joint source-channel coding approach wherein the end-to-end distortion in reconstructing telemetry signals at the surface receiver is directly minimized. I show that the acoustic OFDM technique enables simple implementation of the joint source-channel coding design criterion and present the methodology for optimizing different transmission scheme components. Realistic LWD acoustic telemetry design examples demonstrate that the optimal design results in significant gains in system performance and throughput as compared to standard design approaches.
Electronics; Electrical engineering; Petroleum engineering