Investigation of Permeability Impairment Using Local Polymers for Enhanced Oil Recovery

Abstract

The use of viscosity enhancer in Polymer flooding decreases mobility and improves sweep efficiency of flood water. However, there is a likelihood of permeability impairment due to the polymer retention onto the rock surface. This leads to formation damage. Therefore, a good assessment and evaluation of this problem is important to oil recovery sustenance. In this study, the permeability reduction caused by some local polymers in Nigeria used for Enhanced Oil Recovery was investigated. A laboratory study was carried out using unconsolidated core plugs (sands packs) and crude oil from the Niger Delta field. Two of the core plug samples (control samples) were flooded with simulated brine concentration and viscosity of 20000ppm and 0.949cP respectively. Cisus populnea (Okoho), Abelmoschus esculentus (Okro), Irvingia gabonensis (Ogbono) and Gum Arabic were used as polymers. Water breakthrough time, oil recovery and mobility ratio results obtained from fourteen samples were recorded and compared with that obtained from using only brine. The permeabilities of core plug samples were estimated prior to and after polymer flooding by pressure drop calculation. Residual Resistant Factor (RRF) and adsorption capacity of these polymers at same concentrations of 1000 ppm, 2500 ppm and 5000 ppm were also estimated. At 5000ppm, the RRF and mobility ratio for Cisus populnea, Abelmoschus esculentus, Gum Arabic and Irvingia gabonensis were 2.341/0.91., 1.354/0.35, 2567/0.56 and 3/0.66 respectively. The percentage reduction in permeability and displacement efficiency for Cisus populnea, Abelmoschus esculentus and Gum Arabic are 3.9%/75.30%, 2.7%/89.50% and 4.2%/77% respectively. It was observed that there was no-flow while flooding with Irvingia gabonensis at 5000ppm. The results from the study indicate that Irvingia gabonensis triggered the highest permeability impairment while Abelmoschus esculentus gave the least permeability impairment. The best performed polymer is Abelmoschus esculentus with highest displacement efficiency, reduced mobility ratio, lowest RRF values, lowest static and dynamic adsorption.