Summary

Streamline-based models have shown great potential in reconciling high-resolution geologic models to production data. In this paper, we extend the streamline-based production-data integration technique to naturally fractured reservoirs. Describing fluid transport in fractured reservoirs poses additional challenges arising from the matrix/fracture interactions. We use a dual-porosity streamline model for fracture-flow simulation by treating the fracture and matrix as separate continua that are connected through a transfer function. Next, we analytically compute the sensitivities that define the relationship between the reservoir properties and the production response in fractured reservoirs. The sensitivities are an integral part of our approach and can be evaluated very efficiently as 1D integrals along streamlines. Finally, the production-data integration is carried out by a generalized travel-time inversion that has been shown to be robust because of its quasilinear properties and that uses established techniques from geophysical inverse theory.

We also apply the streamline-derived sensitivities in conjunction with a dual-porosity finite-difference simulator to combine the efficiency of the streamline approach with the versatility of the finite-difference approach. This significantly broadens the applicability of the streamline-based approach in terms of incorporating compressibility effects and complex physics. We demonstrate the power and utility of our approach using 2D and 3D synthetic examples designed after actual field conditions. The reference fracture patterns are generated using a discrete fracture network (DFN) model that allows us to include statistical properties of fracture swarms, fractured ensities, and network geometries. The DFN is then converted to a continuum model with equivalent gridblock permeabilities. Starting with prior models with varying degrees of fracture information, we match the water-cut history from the reference model. Both dual-porosity streamline and finite-difference simulators are used to model fluid flow in the fractured media. Our results indicate the effectiveness of our approach and the role of prior information and production data in reproducing fracture connectivities and preferential flow paths.

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