Mojdeh Delshad

Modeling wettability alteration in naturally fractured reservoirs

Modeling Wettability Alteration in Naturally Fractured Reservoirs By Nariman Fathi Najafabadi, M.S.E The University of Texas at Austin, 2005 SUPERVISORS: Mojdeh Delshad and Kamy Sepehrnoori The main objective of this research is to model the wettability alteration effect of surfactant on the porous medium combined with its interfacial tension (IFT) reduction and oil mobilization effects. One of the main applications of this model would be in simulation of surfactant floods in naturally fractured reservoirs (NFR), where imbibition of the injected brine by the matrix rock and expulsion of oil is the most important mechanism of oil production. The injected surfactant changes the wetting state of the matrix rock to more water-wet conditions which results in higher brine imbibition rates and therefore higher oil production rates. To model the wettability alteration effects of surfactants, UTCHEM, the chemical compositional oil reservoir simulator of University of Texas at Austin was chosen. The wettability alteration is modeled by its effect on relative permeability and capillary desaturation curves of the oil, water, and microemulsion phases. Two extreme wetting conditions are represented by two sets of relative permeability and capillary desaturation parameters and the relative permeability of each gridblock is calculated by interpolating between these two extreme wettability conditions. The interpolation is performed using a scaling factor. Two methods for calculation of the

Two- and Three-Phase Relative Permeabilities of Micellar Fluids

Two- and three-phase relative permeabilities have been measured for a low-interfacial-tension (IFT) brine/oil/surfactant/alcohol mixture in Berea sandstone cores. The measurements were done at steady-state conditions with a constant nominal capillary number of 10/sup -2/. These are the first three-phase micellar relative permeabilities reported to date. Continuous and slug displacements of both partitioning and nonpartitioning radioactive tracers were run for each steady-state experiment. The effluent tracer data from these experiments were analyzed by a capacitance model. Both excess phases flowing with the microemulsion showed significant capacitance effects, but the microemulsion did not. The absence of capacitance indicates that the microemulsion was probably the wetting phase in these low-IFT flows, even more wetting than the excess brine phase. The relative permeability of each phase is a function of only its own saturation during three-phase flow. Polymer dissolved in brine had little effect on the relative permeabilities of brine and microemulsion in two-phase flow.

Alkaline/Surfactant/Polymer Flood Predictions for the Karamay Oil Field

Conventional surfactant/polymer flooding can be made cost-effective by addition of inexpensive chemicals, such as sodium carbonate (Na 2 CO 3 ) to increase pH and to react with acids in crude oils to form surfactants.