Using Acoustic Wave As Carrier Signal To Transmit Information From Downhole To Surface In Drilling Engineering

Directional and horizontal wells have become a conventional drilling technique now, which are widely used in various types of hydrocarbon reservoirs and coal mines. A key element of the steering process is the real-time measurement and transmission of the near-bit navigation information from the bottom of the well to surface. The only commercial systems in drilling engineering transmit data to surface by producing pressure pulses within the portion of the drilling mud enclosed in the hollow drillstring. But the transmission rates are very low (just 1 to 2 bits per second) in this method, and it can not meet the needs of modern drilling. A most promising method is to use compressional acoustic wave 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. The drill string is commonly assembled from segments (9m or 1m in length) of threaded pipe and forms a periodic structure, which is known to behave like bandpass filters. So the transmission rates can be increased to hundreds of bits per second. Based on the theoretical analysis and laboratory experiment of the wave propagation properties in the drillstring for both petroleum engineering and coal mine, this paper proves the feasibility of using acoustic wave as carrier signal to transmit information from downhole to surface in drilling engineering. Helpful considerations for design of the system will also be presented.