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Flow assurance has taken on a primary role in FEED studies as of late and has become a standard tool to test design ideas, design changes, and operating strategies. The expectation from such studies is to lower the risk of flow assurance related problems, thereby minimizing both capital expenditures and operating costs. This discussion includes both the methodology and the results of the flow assurance study. Production is located offshore and is made up of two platforms with a 25 kilometer flowline between them. The production stream is the combination of production from 5 wells and contains oil, water, and gas. This combined fluid presents primarily two flow assurance related problems: slugging and wax deposition. In the case described herein, simulation tools incorporated the various data to create an understanding of the three typical operating scenarios:normal production operations and the respective flowline characteristicsplanned and un-planned shutdowns with resultant fluid cool-down behaviorstart-up methodology and subsequent transient behavior A review of the methodology of the FEED study includes a discussion of what constitutes the necessary input data, how that data was used, how design changes were treated, and how other engineering aspects utilized these results for the final design. The resulting simulated operations of the production system are presented. This includes the thermal behavior of the flowline, the changing fluid characteristics, and the associated temperatures and pressures with respect to the operating methodologies and mitigation techniques. Finally, what makes this study possible is the use of state of the art dynamic simulation technology to delineate complex behavior in flowline systems. A discussion of the computing power and the software capabilities required for such an involved set of variables is provided. Introduction A recent discovery in Ca Ngu Vang field has lead to development of Vietnamese offshore leases and one lease in particular from Hoan Vu Joint Operating Company (HVJOC) prompted an immediate FEED study. Of the multitude of engineering disciplines that began work to assess the needs for this offshore production and transportation endeavor certainly a key aspect was flow assurance. Coupling experience and technology, flow assurance results in reducing initial capital expenditures through efficient design of transportation facilities and ensuring the reliable, manageable, and profitable flow of fluids from the reservoir to the sales point. The plan included producing from five wells, commingling production topside to a wellhead platform (designated CNVWHP), and tie-back to an existing production platform (designated CPP-3) roughly 25 kilometers away. The intent of the engineering analysis is to determine the potential problems experienced by producing these fluids through the proposed facilities and providing remediation solutions.

The Canyon Express development is a three operator (TotalFinaElf, BP, and Marathon Oil Company) subsea development consisting of the transport of gas-condensate from deepwater (~7000 feet) subsea reservoirs to a host platform via dual 47-mile 12-inch nominal OD flowlines. The three developments are Camden Hills (Marathon, Pioneer Natural Resources USA, Inc., and TotalFinaElf), Aconcagua (TotalFinaElf, Pioneer Natural Resources USA, Inc., and Mariner Energy, Inc.) and King's Peak (BP). The Canyon Express development is unique in that it involves ultradeepwater reservoirs from three individual operators flowing into a common subsea multi-phase gathering system in which the operating pressure is lowered over time as dictated by reservoir decline. The flowline fluid is predominantly methane gas along with a liquid phase consisting of condensate, produced water, and methanol (injected for hydrate inhibition). To verify the operability of the system it was necessary to perform transient simulations of the flowline to predict the behavior of the fluid in the flowline.The primary objective behind the transient simulations was to determine the impact of the liquids in the flowline on the topside facilities and evaluate system performance during both upset and normal conditions. The software used to perform these simulations was Scandpower's OLGA-2000 version 1.01. Scenarios and time points where potential problems due to liquids were identified as well as appropriate techniques to control the any associated liquid slugs. The results from this work will form the basis of the operational procedures to be developed for the Canyon Express flowline system.

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