Quantitative Modeling in the North Sea: Towards a More Confident Assessment of the Critical Risks

Abstract

Quantitative modeling has become a standard part of probability assessment, for both hydrocarbon systems analysis and reservoir quality prediction, undertaken in association with prospectivity evaluation in the Norwegian North Sea and Haltenbanken areas. Presently, the Norwegian North Sea and parts of Haltenbanken can be classified as mature basins. As such, quantitative assessment is focussed towards assessment of prospects lying on basin margins outside known kitchen areas; satellite prospect assessment in and around existing infrastructure; and assessment of deep, often high-pressure, high-temperature (HP/HT) prospects in basin centers. Outside the known kitchen areas, access to a long-distance petroleum migration route is critical for success. In the proximity of existing infrastructure petroleum migration and trapped fluid gas-to-oil ratio (GOR) are often key risks. In deep, HP/HT settings reservoir quality and top-seal integrity are often the most important factors. Application of quantitative models in these environments allows a consistent evaluation methodology, testing of the consequences of geological uncertainty, and an improvement in confidence. We will illustrate the use of 3D migration modeling to assess migration fairways close to existing infrastructure and outside known kitchens; our experience of matching observed fluid GOR using 2D compositional modeling; and how we model porosity evolution in HP/HT areas and the influence that thermally controlled quartz diagenesis has on overpressure build-up and top-seal leakage. These examples show how quantitative modeling tools and new understanding of fundamental processes are being used and developed today in the North Sea and Halten bank.