Innovative Concepts to Increase the Data Rate of Downhole Hydraulic Data Transmission Systems

摘要

In modern drilling operations a wide range of data is gathered by downhole sensors placed in the bottom hole assembly (BHA). Directional and geological data are transmitted to the surface in real time and allow the directional driller to monitor and optimize the drill path during the drilling process. Data transmission is usually accomplished using mud pulse telemetry systems. The mud pulse telemetry (MPT) generates encoded pressure waves, which travel through the mud channel inside the drill string. A sophisticated data acquisition unit at the surface is able to detect and decode the incoming data. The receiver unit is also capable of suppressing interfering hydraulic noise. The most common MPT systems are the mud pulser and mud siren, which are located in the BHA and transmit the data up to the surface. The mud pulser creates its signal by slightly changing the static pressure level in the wellbore. On the other side, the mud siren creates a continuous pressure wave at a specific frequency. Both systems have advantages and disadvantages. The mud siren allows a higher data transmission rate, while the pulser enables data transmission over a greater distance. The siren and the pulser offer a limited transmission rate and therefore cannot keep up with the amount of data collected downhole. In the field it is usually not possible to exceed a transmission rate of 10 bits per second. For this reason, complex data processing has to be carried out prior to sending the main information to the surface. At the Institute of Drilling Engineering and Fluid Mining in Freiberg, a research program focuses on new ways to enhance the data transmission by combining conventional transmission methods. In the following paper, the complex technical challenges, which arose during the research program, will be discussed.