Abstract
When multiple reservoirs are produced through a common facility network, the capability to integrate the modeling of surface and subsurface can be critical to field development and optimization. The shared facility network imposes constraints that the combined production cannot exceed, determines the pressure drop in the flow lines, and the composition and volume of the sales and reinjection streams. Pressure drop in flow lines is particularly important in deepwater field development, where flow lines are long, and production from multiple reservoirs can flow through the same riser.
The most robust method for solving the combined surface-subsurface system is to fully couple and simultaneously solve the reservoir and facility equations. However, if the reservoirs fluids are represented with compositional equation of state models, and different pseudo-components are used in some or all of the reservoirs, then the reservoir fluid must be delumped into a common set of pseudo-components in the network. In this paper, we describe a method to consistently and efficiently model such a system with a fully coupled surface-subsurface simulator. At every point in the network, where fluid from only a single reservoir is present, the phase behavior calculations can use the fluid characterization for that reservoir and exactly reproduce the result that would have been obtained if the fluid had not been delumped into the network pseudo-components. However, at any point in the network, the characterization of the common network fluid can be used. In addition, if more compositional accuracy is required, the network fluid can be further delumped into more pseudo-components, or if accuracy is not critical, the fluid can be lumped into fewer pseudo-components for more computational efficiency. Examples demonstrating the flexibility, efficiency, and consistency of the method are provided.
