Design and analysis method of reliable firmware of LWD tool’s controller

As an essential component of Logging While Drilling (LWD) tool, controller is responsible for logging flow control, instruction decoding, environmental parameter measurement and data storage. Firmware with high reliability has substantial significance to ensure reliable work of the controller. A design and analysis method of controller's firmware is proposed in this paper. On the basis of function analysis of the controller, a flexible firmware architecture using modularization technology is presented. On the other hand, an improved Failure Modes Effects and Criticality Analysis (FMECA) method is presented, which considers coupling degree in determining conditional probability to introduce severe results given a failure mode occurs. Engineers can optimize the strategy of design resource distribution after criticality analysis, which may further improve the reliability of the controller's firmware. The proposed design and analysis method of reliable firmware is applied to new type neutron LWD tool's controller, which has worked reliably in several offshore wells.