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FracMan Applications: Reservoir Engineering

The properties of reservoirs dominated by fracture flow are frequently complex. Irregular fracture network geometries yield scale dependent and anisotropic behavior which is not observable in conventional reservoirs. Hydraulic response of a reservoir is further complicated by hydraulic interaction between fractures and the surrounding porous matrix. Discrete fracture network (DFN) models, which are capable of simulating both processes, represent the core of our capabilities.

Fracture network models provide the means for quantifying hydraulic properties from measured fracture data obtained by the exploration geologist. Depending upon the scale of fracturing, fracture network models can be used to estimate hydraulic parameters for reservoir simulation, well test data analyses, or reservoir performance estimates. The network realization are stochastic, so they can be used to quantify variability in the results. The models incorporate flow within the porous matrix as well as the fracture network using either, 1) computationally efficient analytical, or 2) geometrically exact numerical approaches.

Determination of Average Well Production and Expected Variance
Well production within fractured reservoirs is generally highly variable since effective connectivity up of the well with the existing fracture system is uncertain. Since the fracture network models use a stochastic approach, the probability distribution of well production can be determined. Quantification of uncertainties in reservoir development cannot be provided by standard reservoir models.

Optimization of Well Spacing
Optimization of well spacing within fractured reservoirs can be greatly enhanced using fracture network models. Specifically the fractured reservoir model can be used to assess permeability scale effects associated with the probable length of connected fracture networks, the effective drainage radius and effect of fracture anisotropy on the shape of the drainage patterns.

Evaluation of Well Stimulation Techniques
Fractured network models can predict the effectiveness of well stimulation techniques. The models provide the means of determining how successfully the created hydraulic fractures, or multiple fracture stimulations, link up with existing fracture systems. The permeability and anisotropy scale effects of fractured reservoirs are particularly important here and cannot be assessed with standard porous media or dual porosity models.

Evaluation of Secondary Recovery Performance
Secondary recovery within fractured reservoirs is often problematic, particularly when the injection fluid surrounds and isolates matrix blocks prior to their complete desaturation. It is possible to improve the effectiveness of oil recovery using fracture network geometry. This approach more accurately models injection fluid fronts than conventional reservoir models.

Calculation of Reservoir Simulator Input
Stochastic continuum models can be used in conjunction with fracture network models to simulate highly fractured reservoirs. When used to simulate fractured reservoirs, the distribution of individual element properties is determined from network fracture models. See the information on reservoir simulator interfaces for more information.

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Also, please visit the Fractured Reservoir Discrete Fracture Network Technologies presentation. The presentation details the combined efforts of Golder Associates, Marathon Oil and the Massachusetts Institute of Technology to provide new reservoir analysis tools, including an on-line database with field data, analyses, images and software available for downloading.