Compositional Multi Tank Material Balance for Reserve Estimation in Fractured Giant Oil Reservoir

Field development plans and reserves estimates are often driven by complex 3D reservoir simulations, deemed to give the most reliable results. However, material balance method is always suitable to support numerical simulations, making estimates more robust and reducing uncertainties, especially when studying complex or giant fields. In this paper, the authors present the analysis performed on a giant fractured carbonate oil reservoir to support the reserves certification process.

The dual porosity-dual permeability nature of the reservoir was captured by a proper multi-tank approach. Being a green field, a specific analytical approach to correctly estimate the level of communication between the different tanks was used. Furthermore, since the field development foresees gas re-injection, a compositional modeling was also introduced in the material balance simulation.

The material balance model (linked to a surface network model) strengthened the reserves estimates provided by 3D numerical simulation, also providing a comparison benchmark for a successful reserves certification process.