Rig-Movement Accelerometer

On floating drilling rigs, heave movement hampers the accurate analysis of critical return-flow measurements. This heave effect leads to the movement of the telescopic joint into the riser, consequently displacing the drilling mud into the return flowline. These movements introduce variations in return flow that mask the true flow responses from the well. GEOLOG has introduced an accelerometer that is located at the center of gravity of the installation and continuously measures the rig movement under the heave while using a predictive algorithm that computes and compensates the flow variations induced by the pump effect of the telescopic joint. The system has a self-tuning feature that adapts to change in heave height and period in real time with no additional operator input required. This application has been used with major operators drilling in deepwater West Africa and Europe. Once the predictive system’s operating parameters are acquired, GEOLOG is able to detect and measure the flowout component caused by the rig’s heave movement in real time. This is then eliminated from the flowout measurement that is already normalized for drillpipe displacement and changes in circulating parameters to derive a true heave-compensated flowout measurement. The system continues the tuning process, adapting to changes in heave height and period in real time.

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