Hierarchy of integrated models. Applying integrated modeling of varying detail at different stages of gas condensate projects development

Background. An integrated model (IM) is a unified digital model of a field, consisting of related models of a reservoir, wells, and a surface infrastructure model, it is indispensable tool at all stages of major projects, because it allows finding system solutions and takes into account the maximum possible number of factors and constraints. The integrated approach is especially relevant for reservoirs with oil rims, gas and gas condensate assets, when the produced fluid contains a large amount of associated petroleum gas and natural gas and system “reservoir — wellbore — gathering and hydrocarbon treatment network” is inseparable, so need to take into account the mutual influence of components to production forecast, to search optimal development solutions. However, when working with integrated model, requirements for the initial data increase, labor costs and computing power both for the creation and for model maintenance increase, speed of model calculations and taking decisions decrease. One of the major strategic challenges of the company is ensuring the optimum value created, thus need the balance between model detail and calculation accuracy.

In practical cases, it is more correct to speak not about a single integrated model, but about a hierarchy of integrated models or integrated modeling tools. We use a compositional principle of using IM tools, which implies building of ready-made component models and combining them into a full model of the field in a configuration necessary for solving specific problems. It makes sense to use the Pareto law to select the configuration of the integrated model: for individual tasks, we can somewhat simplify the model (component models), having lost only 20% of its properties, and it is possible that the lost properties will not have any effect when addressing this research problem.

Aim. The article object is the matrix of application integrated models of varying degree of detail development, article is based on long-term experience of professional engineers.

Materials and methods. The article presents the case study of a multi-reservoir gas condensate field X as an example of the integrated modeling tools development, which have varying degree of detail depends on project stage and solving problems:

• An analytical (“balance”) integrated model of a field based on a mathematical model;
• Simplified integrated model based on a detailed gathering network model and a simplified analytical reservoir model;
• Integrated model with a “Network” option based on detailed reservoir model and simplified gathering network model (VLP);
• Integrated model in the integrator software (Resolve) based on combining a gathering network simulator (GAP) and a reservoir flow simulator

Various types of integrated models are compared with each other, advantages and disadvantages, solved task and place in hierarchy of integrated models are highlighted. The tools and approaches of integrated modeling used by the authors in practice are generalized in the form of integrated modes applicability matrix. Degree of detail integrated models is associated with the initial data, the stage of project development and the tasks solved at this stage.

Results. The article shows that the introduction of reasonable and justified simplifications, the elimination of the shortcomings of simpler models using analytical methods, custom algorithms and Workflow allows to achieve the match of varying degree of detail integrated models with high accuracy.

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