Viscous-Elastic Fluids Can Mobilize Oil Remaining after Water-Flood by Force Parallel to the Oil-Water Interface

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractResidual oil after water flooding appears in three types: oil drops, films and clusters. Work performed using Newtonian fluids shows that to mobilize the residual oil remaining after water flooding, the driving forces, on condition of oil-water IFT (interfacial tension) being constant, need to be increased by one thousand to ten thousand times over that of waterflooding before the capillary forces retaining the residual oil can be overcome [1] . Viscous forces cannot be increased by such a large magnitude in the field.Polyacrylamide (PAM) solutions have little effect on the oilwater IFT. However, results in the laboratory and field show that after flooding by polymer fluids, all types of microscopic scale residual oil in porous media are lowered [2] . The amount that is lowered is related to the elasticity of the fluids. Other conditions being the same, the higher the elasticity, the lower the residual oil saturation. The results of lab tests (including microscopic visualization cores) show that viscoelastic fluid flooding can lower the residual oil saturation in cores of different wettabilities. The main forces to mobilize the residual oil by viscoelastic fluids are not entirely the same as that of Newtonian fluids. It is not only a force perpendicular to the oil-water interface overcoming the restraining capillary force, but also a viscous dragging force parallel to the oil-water interface that mobilizes the residual oil.

Effect of porous media properties on the onset of polymer extensional viscosity

“…Thereby, as the third stage of field development, several techniques are proposed which Seright et al, 2009) recently some experimental results (Urbissinova et al, 2010) along with numerical studies (Afsharpoor and Balhoff, 2013;Bai et al, 2011;Xia et al, 2008) and CT image visualization (Hou et al, 2009;Meybodi et al, 2011) demonstrated that in some cases, the polymer can also mobilize the trapped oil (Bakhitov et al, 1980;Cheng et al, 2010;Sherbone et al, 1967;Wang et al, 2001b;Wu et al, 2007). Several reasons are proposed to explain this observation such as polymer adsorption Kohler, 1987, 1988), viscoelastic effect (Huifen et al, 2004;Wang et al, 2000Wang et al, , 2001aWang et al, , 2001bWu et al, 2007), shear thickening (Delshad et al, 2008;Jones, 1980) and memory effect (Hossain et al, 2009). However, phenomena such as shear thickening and memory effect can be also considered as viscoelastic effects.…”

A Systematic Study of the Polymer Visco-Elastic Effect on Residual Oil Saturation by Core Flooding

“…In the early years of Enhanced Oil Recovery research, incidental papers already reported the fact that polymer flooding may reduce residual oil recovery under certain conditions [5] [6] [7] [8] [9] [10]. Recently, supporting the polymer flood in the Daqing oil field in China, a comprehensive study has been carried out, showing that the visco-elasticity of the polymer solution can increase the microscopic displacement efficiency in core material [11] [12] [13] [14] [15] [16] [17] [18] [19]. These claims were supported by pore scale simulations, microfluidic experiments, core floods and field observations.…”

Polymer Flooding of Heavy Oil - From Screening to Full-Field Extension

“…However some of the significant work performed for the large polymer flood in Daqing (China) suggests that polymer can reduce oil saturation below S or due to its viscoelastic properties (Wang et al 2000, Wang et al 2001a, Wang et al 2001b) at least for low viscosity oil (9 cp for Daqing).…”