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This paper introduces an Algebraic MultiScale method for simulation of flow in heterogeneous porous media with embedded discrete Fractures (F-AMS). First, multiscale coarse grids are independently constructed for both porous matrix and fracture networks. Then, a map between coarse-and fine-scale is obtained by algebraically computing basis functions with local support. In order to extend the localization assumption to the fractured media, four types of basis functions are investigated:(1) Decoupled-AMS, in which the two media are completely decoupled, (2) Frac-AMS and (3) Rock-AMS, which take into account only one-way transmissibilities, and (4) Coupled-AMS, in which the matrix and fracture interpolators are fully coupled. In order to ensure scalability, the F-AMS framework permits full flexibility in terms of the resolution of the fracture coarse grids. Numerical results are presented for two-and three-dimensional heterogeneous test cases. During these experiments, the performance of F-AMS, paired with ILU(0) as second-stage smoother in a convergent iterative procedure, is studied by monitoring CPU times and convergence rates. Finally, in order to investigate the scalability of the method, an extensive benchmark study is conducted, where a commercial algebraic multigrid solver is used as reference. The results show that, given an appropriate coarsening strategy, F-AMS is insensitive to severe fracture and matrix conductivity contrasts, as well as the length of the fracture networks. Its unique feature is that a fine-scale mass conservative flux field can be reconstructed after any iteration, providing efficient approximate solutions in time-dependent simulations.

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This paper presents a hybrid numerical/analytical model for the pressure-transient response of a finite-conductivity fracture intercepted by a horizontal well. The model dynamically couples a numerical fracture model with an analytical reservoir model. This approach allows us to include finer details of the fracture characteristics while keeping the computational work manageable. For example, the fracture may have irregular shape, nonuniform width, and variable conductivity, and the well may not intersect the fracture at its geometric center.In this paper, we use the hybrid model to investigate the effects of fracture properties on the pressure-transient characteristics of a single, finite-conductivity horizontal-well fracture. The single horizontal-well-fracture model can be extended easily to multiply fractured horizontal wells by superposition. The model also can be used to compute the pseudoskin caused by the effects of nonideal fracture geometry, variable conductivity, and flow choking around the wellbore and to investigate the influence of fracture properties on the performance of horizontal wells.

Smart waterflooding (SWF), an emerging EOR technique, was first investigated in sandstone reservoirs. However in recent years, the effect of smart water on carbonate reservoirs has gained wide interest. Despite the increasing number of research and publications in this area, the mechanism enhancing the recovery is still not fully understood. Wettability alteration and reduction in interfacial tension (IFT) have been identified as the two most dominant mechanisms. Divalent ions such as sulfate (SO42-) are found by many investigators to show promising results during SWF. However, limited research has been carried out to investigate the effect of trivalent ions. The objective of this study was to investigate the potential of phosphate (PO43-) spiked brines as a viable EOR technique in tight carbonate reservoirs. Seawater with different dilution factors and varying concentration of phosphate ions were investigated against non-phosphate brines. Impact of these brines on wettability alteration was qualitatively monitored by tracking the rate of contact angle change on several aged-carbonate core samples subjected to varying aging periods. Various designed phosphate brines were tested at elevated temperature of 90 °C, and IFT was also measured at both ambient and elevated temperature (90 °C) to complement our findings. To identify the impact of phosphate ions on wettability alteration due to brine/crude oil/rock interactions, carbonate core samples were prepared having initial contact angle ranging from 130° to 160°. The rate of contact angle change observed ranged from 9° to 36° as a function of varying composition of smart brines. A slight decrease in IFT was observed when lower salinity brines were used without phosphate. Phosphate spiked brines show a near surfactant reduction in IFT, compared to the low salinity brines. Smart brines with higher concentration of phosphate achieved better results than those with lower concentration.