Pressure losses in the surface network can have a critical impact on well productivity. Therefore, for field development planning, it is highly advantageous for the simulation model to include the surface facilities as well as the reservoir. The objective of this study is to outline the advantages of modeling reservoir-to-surface coupling over conventional standalone simulation.

This paper presents a case study of creating an integrated model of a giant oil field with a compositional surface gathering system. The reservoir model is controlled by complex field management logic including gas balance. The reservoir wells are balanced with the surface network by setting inflow performance relationships (IPRs) as the boundary conditions. The network is then solved and returns operating point pressure as a varying tubinghead pressure (THP) limit for the reservoir well. After the minimum THPs have been established, the guide rate balancing allocates production by respecting the THP limits at which wells can flow.

The results show that an integrated reservoir-to-surface coupling gives significantly different but more realistic production allocation profiles at the group and well levels than a separate standalone simulation model. The oil production plateau rate drops prematurely as surface-network-constrained guide rate balancing results in different production allocation between producing wells. In fact, updated allocation results in an increase in gas-oil ratio for some of the groups and consequently leads to early gas breakthrough for some of the wells. Increase of stability in results and speed were achieved by selecting the appropriate reservoir-to-surface-network balancing frequency and leveraging the power of multicore hardware.

The sequence of network and guide rate balancing can over-constrain some of the high-capacity groups by a higher THP limit. To avoid this, a nested approach is presented that includes an additional network balancing step that is solved by IPRs based on guide rate balancing, which allows reducing the THP limit and prolongs the plateau rate. Based on this field example, integrated modeling has proved to bring value by providing more accurate profiles and debottlenecking of surface facilities.

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