Operation of the Huldra field commenced on November 2001. It is a gas condensate field, which has been developed with a not normally manned wellhead platform remotely controlled from the existing, manned Veslefrikk B platform. A first stage separation process is installed at the platform to separate gas and liquid. Two pipelines emanate from the Huldra field - a 93.2-mile [150 Km] 20" inner diameter pipeline transporting wet gas from Huldra to the Heimdal platform and an 8" inner diameter 9.9-mile [16 Km] pipeline transporting unstabilised condensate, including water, to the Veslefrikk platform. Due to the hydrocarbon mixture, the flow through these pipelines exhibits multiphase behaviour and therefore requires a multiphase real-time simulation model for surveillance and optimised control. Statoil was responsible for development of the Huldra field and is the field operator. The transient multiphase code OLGA has been an important tool in all phases of the project from the decision to develop the field and into the production phase. The design of the Huldra wet gas pipeline was a significant improvement in multiphase flow transport technology due to the long large diameter pipeline which should be tied-in to the existing Heimdal platform with restricted liquid processing capacity. For the condensate line efficient and good environmental hydrate and wax control methods are selected. This paper describes the requirements of the simulation engine and the pipeline modelling system. This leads to a clear split between the functionality that is necessarily encapsulated in the simulation engine and the functionality that can be incorporated within the wider On-Line System environment developed by Energy Solution International for gas pipeline modelling. The aim is to provide a common level of functionality throughout the system. Functions for multiphase flow pipelines, such as: model tuning, leak detection, liquid accumulation, and composition tracking need to be considered as well. A brief description of the approach to these issues is given. The strategy for operating the pipeline and its impact on extending the functionality of the existing OLS system is presented. This paper gives a brief description of the initial operational experiences with the realtime model. Page 2 of 30
In November 2001, the Huldra field commenced production. Design and start-up of the transport system for wet gas and condensate from Huldra is an extension of current experience. Statoil, as the operator of the Huldra field, awarded Gassco contracts for operational support for the condensate and wet gas pipelines. Valuable experience related to operational aspects and real-time modelling of large-scale multiphase flow systems has been gained after start-up of production. Huldra is a gas/condensate field located in the North Sea at a water depth of 410 ft [125 meters]. After a first stage separation the rich gas containing water and MEG is routed 93.2 miles [150 km] to the Heimdal platform for further processing.