A New Methodology To Estimate Fracture Intensity Index For Naturally Fractured Reservoirs

摘要

The characterization of Naturally Fractured Reservoirs (NFR) represents additional challenges to that of conventional reservoirs because it is not only required the description of two separate means (matrix and fracture) but also it is necessary to understand their interaction. Among the list of potential parameters that can contribute to understand the complexity of NFR is the fracture intensity. This is defined as the density of fractures per foot of formation. This attribute is a key factor for a quantitative prediction of the porosity and permeability of a NFR. Furthermore, it is directly related to the reservoir productivity and can be used to optimize reservoir management decisions. In this paper, we present a new methodology to identify fractured intervals in a NFR by combining the answer of a set of conventional electric logs and the information coming from the physical description of the cores of a fractured formation. With this information, a continuous variable fracture intensity track is generated and related with the fracture permeability through two different approaches. In the first approach, the aperture and fracture intensity were used to estimate the fracture permeability. The second approach is indirect. Using a non-parametric regression technique, the measured fracture permeability is modeled from variables such as GR, fracture porosity, Facies, and fracture intensity. In both cases, quantitative models of fracture permeability were obtained under static conditions. We have successfully applied the proposed technique on a reservoir producing from a Cretaceous Formation in a Colombian Field. The models obtained were satisfactory validated with information coming from core analysis, stratigraphic and structural models, pressure tests, and production data.