Osman, Yossra (2019-03). An Experimental Investigation of Improved Recovery in Fractured Carbonate Samples Following Foam Flooding. Master's Thesis.
Thesis
Due to complex depositional textures and diagenetic processes, carbonate reservoirs are challenging in terms of recovery. This thesis will present the use of foam flooding as a tertiary recovery technique, and as a means of overcoming limitations of pre-existing methods. Two cases were studied in this thesis - Case 1 will present the EOR impact of surfactant flooding on nonfractured carbonate rocks, and Case 2 will present the EOR impact of foam flooding on fractured carbonate rocks. The three core samples used in this study are Indiana limestone carbonate rocks. The cores have an approximate dimension of 13 cm length and 3.8 cm diameter. The porosity is in the range of 13-21% and the permeability is in the of 0.69 -2.17 mD. In the first case (Case 1), surfactant flooding aims to improve recovery by decreasing the oil-water interfacial tension, thus improving the displacement efficiency. In the second case (Case 2), foam aims to improve recovery by both decreasing the oil-water interfacial tension, and plugging high permeability channels, thus forcing brine to sweep areas of lower permeability. Prior to implementing any recovery techniques in Case 1 or Case 2, petrophysical properties including porosity, permeability, initial oil saturation and residual water saturation were obtained through mass balance, pressure difference tests during steady state injection and volume balance respectively. For Case 1, recoveries due to waterflooding were in the range of 22.-34 %. For Case 2, waterflooding performed poorer with recoveries in the range of 20 - 27 %. Tertiary recovery (surfactant flooding for Case 1 and foam flooding for Case 2) shows an enhancement in recovery in the range of 0.5 - 5(% of OIP) for Case 1, and 5- 8 (% of OIP) for Case 2. These results prove to be effective for the low surfactant concentration used (0.1%). Low concentration foams and surfactant seem to be a more reasonable choice for the cost-cutting industry of today.
