The Appomattox asset, which currently has an expected production of 175,000 barrels of oil equivalent per day (boe/d), is a floating production system fed by several subsea production drill centers in the Gulf of Mexico, located in blocks MC437, 348, and 391-393. As the focus on in-situ leak detection has grown, two leak detection systems were implemented at Appomattox. Each uses an entirely different methodology for leak detection.
The Conditional Rate of Change (C-ROC) algorithm resides in the production control system and uses existing subsea pressure sensors. This algorithm was developed by Shell and is detailed in separate publications. Developed in parallel to the Appomattox project, C-ROC was added to the project later in the project lifecycle as it has become the Shell Gulf of Mexico standard for leak detection. In addition to the C-ROC method, each of the production drill centers has an Acoustic Leak Detector (ALD), provided by Naxys AS, a Baker Hughes business. These units are being piloted by Shell for the Gulf of Mexico. The ALD acoustically monitors the production manifold, wells, and associated flowline hardware at each drill center. The system is designed to distinguish the difference between background noise and actual leaks.
Implementation of each of these technologies leverage several other novel technologies and uses of existing technologies at Appomattox, including high bandwidth communications to support ALD and high-fidelity process simulation to both validate and train operations staff on the C-ROC algorithm.
This paper provides an overview of each leak detection system, details the technologies leveraged to implement these systems, and relates the project experiences thus far with each method.