ABSTRACT

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 flowinginto 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.

Introduction

TotalFinaElf, BP, Marathon Oil Company, Pioneer Natural Resources USA, Inc., and Mariner Energy Inc. intend to jointly develop three deepwater fields in the Gulf of Mexico region. The fields are the Marathon-operated Camden Hills in Mississippi Canyon (MC) 348 block, TotalFinaElf-operated Aconcagua in MC305 block, and BP-operated King's Peak in DeSoto Canyon (DC) 133, DC177, and MC217 blocks. The production consists primarily of methane gas with varying volumes of water and condensate. Methanol is to be injected at the wellhead for hydrate inhibition. Maximum production rates from each field range from 100 to 225 MMSCFD with approximately 200 to 450 BPD of condensate, 300 to 900 BPD of water, and 450 to 1400 BPD of methanol.

The production from the wells will be transported via twin 12-inch nominal O.D. flowlines from the Camden Hills field at approximately 7200-foot water depth, to the Aconcagua field at approximately 7050-foot water depth, then to King's Peak field at approximately 6600-foot water depth, and finally to a host platform fixed structure located on the continental shelf. The twin flowlines (East and West) form a piggable system via a loop connecting the two flowlines at the flowline ends. The flowlines are separated by a pigging valve, which will remain closed during the normal operation of the system. Thus, the flowlines will operate independently of the other. Analysis of the flowline gas/liquid behavior under various operating scenarios is required to establish and verify operability.

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