A system for monitoring a marine well for shallow water flow: Development of early detection

Abstract

Deepwater basins around the world contain shallow sequences of overpressured, sand-prone sediments that can result in Shallow Water Flow (SWF) events. These events have frequently resulted in wellbore instability, increased man-hour exposure to potential HSSE risks as well as non-productive time (NPT) and have sometimes been the cause of the loss of the well while drilling the shallow (riserless) section for oil and gas exploration or development projects. Methods previously established to classify the magnitude of a SWF event have been used with partial success to identify the onset of a SWF event. The need existed to develop a system enabling early prediction, detection and mitigation of SWF events while drilling. Real-time monitoring of the riserless section of a marine well for SWF requires a system using a plurality of data feeds defined here as the SYSTEM. The data feeds include seismic data, remotely operated vehicle (ROV) video, and surface and downhole logging measurements. A SWF surveillance methodology, herein defined as a discharge category model (DCM), has been developed for early detection of a SWF event, prior to the onset of wellbore instability. The DCM focuses on baseline discharge categories (ranging from no flow to minor flow) prior to wellbore instability and taking into account the u-tube effects. Real-time monitoring of data feeds coupled with the DCM in the context of the SYSTEM has helped to mitigate SWF events. There have been no wells lost due to SWF events that have utilized the DCM in the context of the SYSTEM in various basins throughout the world. A total of 154 wells have been monitored globally using the DCM with 46 SWF events detected and mitigated before reaching a severity level that might compromise the well integrity from 2012 to 2019.