FE-MWD Logging in a Different Environment Induced by Drilling with a Rotary Steerable System

Abstract The drilling of horizontal and extended reach wellbores is being revolutionized by rotary steerable systems such as the AutoTrak™ tool. Typically, advanced directional drilling has been performed with steerable mud-motor systems. However, drilling with a steerable mud-motor results in a rough and tortuous wellbore due to the motor's geometry and operational behavior. A rough wellbore may affect the performance of various logging sensors deployed with the system. Different logging sensors are affected differently, and so the ability to compensate for borehole effects varies from sensor to sensor. The result may be a log that suffers in quality. Rotary steerable systems drill smoother and less tortuous wellbores. As a consequence, typical borehole effects visible on various FE logs may not be apparent when drilling with rotary steerable systems. Knowledge of the logging environment in which the data were obtained is important when analyzing the log. It is believed that the introduction of rotary steerable systems will improve the economics of long horizontal and extended reach wells. As a consequence, there will be an increase in the drilling of these types of wells. It is desirable to log these wells while drilling, as the deployment of wireline-operated logging tools will be costly and risky. The real-time logging information can be used for navigating in the reservoir and optimizing the wellbore position. Also, FE-MWD logging sensors are continuously being developed and improved, so the desire to perform the logging operations while drilling will tend to increase. This paper discusses the differences in logging environment as a result of drilling with a rotary steerable system as opposed to a steerable motor system. The paper also discusses the impact of this new logging environment on the results from various FE-MWD logging sensors. Examples of logs recorded in comparable formations with the two drilling systems are included. This may help log analysts in their interpretation of log results, as rotary steerable systems are more commonly used for horizontal and extended reach drilling (ERD).