Recent Advances In Measurement While Drilling

MWD services have been commercially available for over ten years. The most entrenched application is that of directional services, where conventional methods such as wireline steering have all but been obsoleted. The only real advances in this application have been those influenced by software changes and data rate improvements. For example, faster tool face update rates while steering are now possible. A relatively recent sensor is one that provides weight on bit and torque in real time. The currently intended applications are estimation of bit wear and bearing failure. A drilling model is used to estimate shear strengths of the rock, although the model currently appears to be limited to shales only. The resulting Mechanical Efficiency Log is used for a variety of interpretations. An augmentation of the RLL service is now available whereby the recorded log may be retrieved on a wireline by stabbing with a "wet" connector upon demand. In the interests of brevity, neither this nor the MEL service will be discussed here. The other recent sensors/services are the EWRR and CN0SM, both described more fully below.