A New Mud Pulse Telemetry System for Enhanced MWD/LWD Applications

Abstract

Abstract Mud Pulse Telemetry systems in drilling operations have enabled the industry to gather valuable directional and formation data while drilling the well, and to optimize the drilling process. This makes drilling operations more cost efficient and allows the drilling of complex wells. In recent years, new LWD technologies have dramatically increased the amount of information collected downhole. This increasing demand for realtime bandwidth is a major challenge for conventional Mud Pulse Telemetry, which has data rates that are normally below 3 bits per second. This paper describes a system for downhole-to-surface Mud Pulse Telemetry that uses baseband or carrier modulated pressure signals generated by a novel mud pulser design and a surface data acquisition unit with advanced signal processing capabilities. The new system is able of handling the complex and continuously varying properties of the transmission channel (the pipe bore filled with flowing drilling mud) by optimizing the transmission signal and the surface processing algorithms in realtime. Under a given scenario, higher data rates can be achieved that, from a log-quality standpoint, result in high log-densities for improved realtime decision making. Surface processing algorithms include active pump noise cancellation, dual pressure transducer processing, signal filtering and signal decoding. In addition, the system contains an automated calibration routine that after turning pumps-on measures the characteristics of the transmission channel. This novel feature assures that the latest knowledge about the transmission channel is available in the processing algorithms. The new system has been successfully run in field-trials in the United States, North Sea, South America and the Middle East. During these deployments, data rates could be substantially increased compared to previous offset runs. The focus in this paper will be on a description of the system and its impact on both MWD and LWD realtime services. Introduction Mud Pulse Telemetry (MPT) has been the global standard for real time data delivery from Measurement While Drilling (MWD)/Logging While Drilling (LWD) systems for the past thirty years. This is largely due to the robustness of the downhole system, the simple concept of a single down hole transmitter and a single surface receiver, proven performance under various conditions and the possibility to adjust various down hole Bottom Hole Assembly (BHA) parameters while drilling the well. With the introduction of more complex MWD/LWD tools and services, most of which produce large amounts of real-time data, it has become crucial to use the available mud channel more efficiently to ensure that there is sufficient information to make informed decisions whilst drilling. This is a complex task given the uncertainty and continuous fluctuations of the various system properties in the mud channel, most of which are outside the control of the MWD/LWD service company, these include:mud pumpspulsation dampenerssurface pipingpressure transducer locationsdrill string componentsmud propertieswell depth In addition, MWD/LWD companies have to deal with a limited amount of down hole power which adds to the restrictions in optimizing the entire system. This paper introduces a new telemetry system, including a novel, advanced, mud pulser design which has been in development since 2001 and a new surface data acquisition unit with improved signal processing capabilities. The overall system is able to automatically adjust its decoding parameters during data transmission. Since measurements are made continuously, fluctuations of channel properties are captured and accounted for. Field-trials have been carried out that proved the new concept. Data rates of up to 20 bits per second (bps) have been achieved in commercial drilling situations. Compared to earlier offset runs this is an increase of more than 200%. Those optimized, high data rates are essential to support present and enable future MWD/LWD services.