Compositional Integrated Subsurface-Surface Modeling

Abstract

Abstract Adequate modeling of a hydrocarbon production system may require integration of several reservoir models with a model for the surface network and a model for the processing facilities. The degree of detail in each model should be in accordance with its impact on the business case. Compositional modeling of the hydrocarbon streams is usually highly desirable for volatile oils, gas-condensates and production systems in which different streams are mixed. However, compositional modeling is notoriously involved and CPU-intensive. Hence it has so far only been applied in an approximate way, with a few lumped components and reduced detail in the geological reservoir model(s). These approximations will often defeat the purpose for which compositional modeling was brought in. Compositional modeling has been implemented in Shell#x0027;s proprietary Hydrocarbon Field Planning Tool to enable adequate modeling of gas-condensate and volatile oil systems. Surface network modeling was accomplished by interfacing with the compositional mode of the commercial network solver Pipephase. The compositional well streams were generated by extension of Shell's multi-purpose reservoir simulator MoReS with a delumping scheme. This scheme is in essence postprocessing of the well streams calculated on the basis of a two-component reservoir fluid representation. It requires a marginal amount of CPU time, independent of the number of components. In all applications so far the delumping scheme was found to be unexpectedly accurate: the mass rates of the 20-odd well stream components were reproduced with an average relative accuracy of about 0.5 %. The well streams consist of all components mentioned explicitly in the PVT report(s) and typically about 10 pseudo-components to represent the heavy fraction. In this paper the physical considerations are described, which underly the delumping scheme. Also provided are a detailed validation study and the key results of field studies of gas-condensate fields in Australia's North-West Shelf area and in the North Sea.