Simplified Network Simulation Vs. Integrated Asset Modelling for Management and Development of Offshore Gas Fields

Abstract

The development of any offshore assets is always a technical and economical challenge, especially for the investment decision-maker. It is well known that stand-alone dynamic reservoir models and surface facilities models are not able to effectively capture the overall complexity of the system if considered independently from each other. The task can be effectively faced only coupling together reservoir models, wells, surface network, facilities and processing plants models in the frame of an integrated asset modelling system. Nowadays, however, several solutions and workflows are available to achieve an effective coupling of the surface and subsurface simulation models, and the choice of the right approach can also depend on the specific targets of the study. In this paper, we compare two available solutions for reservoir-network coupling in the case of a real dry gas asset, consisting in a brown field currently in production and five near-by green fields. These green fields will be developed to meet the contractual gas sales target using the spare capacity of the existing facility. Since the near-by fields are currently in different development stages -and then different state of knowledge in terms of data acquisition or reliability of reservoir model -the simulation of the integrated system will need to take into account specific different priorities to correctly balance production from the different fields.Main aim of the activity is to highlight advantages and criticalities of the two different approaches with respect to the specific study goals to be addressed. Simulating multi-asset development scenarios from reservoir to surface facility till the market delivery point represents one of the most important task in the oil and gas business and it can be achieved under two different modeling concepts. The first concept is a simplified solution represented by the capabilities offered by some commercial simulators, where the network solver (based on pre-computed hydraulic table) is directly included in the reservoir simulator together with some possibilities of reservoir coupling. The second approach consists in combining reservoir models with a dedicated network simulator having optimization capabilities, building an Integrated Asset Model (IAM). Although IAM approach is recognized to be an effective tool for asset management, in some cases the simplified approach can be very useful to speed up the screening of different development scenarios without losing accuracy. In the real case considererd in this parer, the production logic was implemented for both methods and applied in the simulation of alternative development scenarios. Both approaches are able to resolve and handle the differences between alternative development scenarios in terms of production profiles, making all the needed information available to the project management team in due time to be able to strengthen the decision making process within an acceptable degree of accuracy.