Acoustic Transceiver Optimization Analysis for Downhole Sensor Data Telemetry via Drillstring

Abstract

Downhole sensor data telemetry using acoustic waves along the drillstring helps to know the physical and chemical properties of the formation and drilling fluid in Logging While Drilling. However, complex drillstring channel characteristics and normal downhole drilling operations will often adversely affect the quality of acoustic telemetry. Based on a theoretical channel model, we analyze the effects of transceiver optimal placements on acoustic transmission through a periodic drillstring. Considering the downhole noisy conditions including the surface noise sources, the downhole noise sources and multiple reflection echoes, dual acoustic receivers and an acoustic isolator are analyzed to improve the Signal-to-Noise Ratio and the capacity of the uplink channel. By arranging two receivers spaced one-quarter wavelength apart at receiver ends, the suppression results of one-way downlink noises are evaluated with the aid of the channel transient simulation model. Then the isolating results of uplink noises from drilling bit are investigated, with regard to the isolator placed between the downhole transmitter and a noise source. These methods, in conjunction with the complex drillstring features, show that the uses of the available transceiver design and signal processing techniques can make the drillstring as a waveguide for transmitting downhole sensor information at high data rate.