Dynamics of surfactant flooding in tight carbonate rocks

With the global increase in the demand for crude oil, the need to develop enhanced oil recovery techniques is crucial. These techniques must focus on how to displace greater volumes of trapped oil from within a given rock. Since carbonate reservoirs constitute over half of the world's oil reserves, research has recently shifted its focus on recovery techniques as they pertain to carbonate reservoirs. However, due to complex depositional textures and diagenetic processes, carbonate reservoirs are challenging in terms of recovery. In this study, a robust experimental core flooding setup is employed to assess the impact of wettability of tight carbonate rock in governing the effectiveness of surfactant flooding. A series of flooding experiments with well-defined boundary conditions were performed on the low porosity core plug samples of Indiana Limestone. The three core samples used in this study are referred to as FD3H, FD4H, and FD5H. The cores have an approximate dimension of 13 cm length and 3.8 cm in diameter. The porosity is in the range of 13-21% and the permeability is in the of 0.69 -2.17 mD. The core samples exhibited differing wetting characteristics: strongly oil-wet, moderately oil-wet and weakly oil-wet. Initially, the core samples were saturated with oil and then water flooding was conducted until irreducible saturation was achieved. Later, surfactant flooding was performed as a tertiary recovery technique. The experimental results demonstrate that the efficiency of surfactant flooding increases as the tight carbonate rock get more oil-wet. The strongly oil-wet core manifested highest oil recovery, whereas in the weakly oil-wet core the recovery efficiency as a result of surfactant flooding was least.