Modeling of Complex Naturally Fractured Reservoirs with Novel Formulations (MCNFR-NF)

Objective

The main objective of MCNFR-NF is the development of new-generation simulators for naturally fractured reservoirs (NFRs) characterized for exhibiting a fractal geometry and the presence of vugs. These novel simulators will provide a good level of certainty on both history matching and production forecasting of these types of reservoirs during primary depletion and application of EOR and/or IOR methods.

Motivation

Modeling of NFRs by using current commercial simulators only considers,

• Dual-porosity (matrix blocks separated by fractures),
• Fractures uniformly distributed,
• A single fracture scale,
• Fully interconnected fracture network.

The above assumptions have demonstrated to have flaws with the following consequences,

1. Poor predictions of production behavior,
2. Erroneous recovery forecasts during the application of EOR and/or IOR processes

Based on the aforementioned limitations, it is possible to state that there is a lack of mathematical models which capture the complexity of naturally NFRs, where a large amount of the worldwide residual oil is located.

Proposed Modeling

Current mathematical models available in the literature are not accurate enough for a robust representation of NFRs. For this reason, it is mandatory to search for alternative techniques that better describe the heterogeneities and anisotropies related to NFRs, such as,

• Fractures at different scales and not fully interconnected fracture network
• Non-uniform distribution of fractures
• Presence of vugs.

In our research group, we focus in the development of novel formulations which represent appropriately the fluid flow throughout NFRs. To fulfill our ultimate goal, we propose the following general models,

• Modeling of naturally fractured vuggy reservoirs (NFVRs).- Triple porosity - dual permeability (3Φ, 2k): matrix, fractures, and vugs.

• Modeling of NFRs with fractal geometry (Fractal YNFs).- Anomalous diffusion for the representation of complex fracture and vugular networks, taking into account a non-uniform fracture distribution, different degrees of connectivity of the fracture network, and fractures at different scales.

The conventional dual-porosity model (matrix and fractures), currently available in commercial simulators, results to be a special case of the general formulation proposed by our research group.

Modeling of NFRs by using the models previously described will allow establishing specific recovery methods for each of the components comprising the fractured media, as well as forecasting the expected efficiency of each of these processes.

Final Product

New-generation of NFRs simulators including fractal and vugular modeling with capabilities to appropriately represent primary and enhanced recovery processes including water and gas injection, and thermal and chemical enhanced recovery associated with the exploitation of NFRs.

The main advantages of the proposed NFR modeling are,

• Explain the production behavior observed in the field which cannot described with the use of conventional dual-porosity commercial simulators,
• Prevent/anticipate mud losses during drilling operations,
• Evaluate the effect of vertical communication on the breakthrough of non-desirable fluids,
• Evaluate appropriately the production potential of NFRs,
• Forecast with a good level of certainty the efficiency of EOR/IOR methods,
• Determine the best locations for infill-drilling.