On multiple wireless channels in oil wells drill strings

Wireless communication of information in oil wells is a key component of drilling operations. For cost-effective, fast, and low-risk drilling, information such as temperature, pressure, etc., should be transmitted from downhole to the driller on the surface. Data transmission through drill strings and via sound signals is a feasible approach. However, due to the superposition of many reflections from tool joints connecting pipes in the drill string, it behaves similarly to a multipath wireless channel with strong signal fades. Here, we study multichannel reception using several receivers to improve communication system performance. We propose a strain sensor and a tri-axial accelerometer as a four-channel receiver. Given the complexity of studying the strain channel and the three acceleration channels analytically, we conduct experiments to obtain these channel impulse responses. Our measurements show that these wireless channels are nearly uncorrelated, and therefore, can provide diversity gain. This is further confirmed by presenting low bit error rates that this system provides. Comparison with single channel receivers shows the usefulness of the proposed system for wireless communication via drill strings.