Modeling the Effects of a Deepwater Leak on Behavior of a Multiphase Production Flowline

Abstract Identification of a leaking flowline represents a special challenge for the many deepwater developments planned in the U.S. Gulf of Mexico (GOM) and around the world. While historically, the number of shallow water releases from pipelines is extremely small, deepwater flowlines operate under conditions rarely encountered in previous development schemes. The remoteness of the deepwater flowline, coupled with a number of complex interactions between the released fluids and the deepwater environment effectively eliminates most external detection methods. Commonly applied internal leak detection methods are also ineffective due to multiphase flow and their dependence on precise metering of both the inlet and outlet flowrates. While multiphase meter technology is emerging for the deepwater market, these devices have rarely been applied in the GOM and may have difficulty providing the required accuracy given the wide range of flow conditions encountered during the life of a well. This paper considers how the presence of a leak would be manifest in the flow behavior of a deepwater production flowline for the annular mist, stratified and slug flow regimes. The models developed require only routine production data, i.e. inlet and outlet pressure and outlet flowrates. Also, various leak locations along the pipe circumference are considered, i.e. top and bottom leaks. The results indicate that a leak can be detected in many instances if special testing and monitoring methods are utilized. In particular, detection is greatly enhanced when flow pattern changes occur downstream from the leak. The case of liquid leaking from the bottom of the pipe in stratified flow may be the most difficult to detect.