Youngho Jang

Experimental Investigation of Polymer Adsorption-Induced Permeability Reduction in Low Permeability Reservoirs

The polymer retention during polymer flooding causes reduction in pore throat size which can be detrimental to oil recovery. Especially, in low permeability reservoir unlikely in high permeability system, EOR effect of polymer flooding would not excel comparing to water flooding because of the polymer adsorption onto grain surface. This phenomenon is more significant as higher concentration of polymer solution is injected. In this study, we investigated oil recovery process during polymer flooding for a quarter of 2D 5-spot pattern of low permeability sandstone slab, in which the injected polymer solution flows in different shear rates corresponding to streamlines. The results showed that the ultimate recovery was 1.9 times higher in concentration of 1,000 ppm case than 0 ppm. The polymer adsorption layer formed during the flooding reduced the effective permeability of 1,000 ppm polymer solution. Therefore, it facilitated the oil flow and the stage of water-cut reaching 99% was slackened off.

The Development of a Generalized 3D DFN Simulator Implementing 2D Rectangular Fracture Flow

Abstract According to the Nelsons classification scheme, naturally fractured basement reservoirs are Type 1 systems in which the fractures provide porosity and permeability. Hydrocarbon production from basement reservoirs only occurs through the connected fracture network. Thus, characterization and prediction of flow behavior in basement reservoirs is extremely difficult due to the heterogeneity of the fractures. In this study, a generalized multiphase discrete fracture network simulator was developed. The model implements 2D flow within a rectangular fracture, which is important in thick fractured reservoirs like basement rocks. The discrete fracture network model developed in this study was validated for two synthetic fracture systems using a commercial model, ECLIPSE. Comparison showed excellent agreement between the results for both models. To examine the changing production behavior in fractured basement reservoirs, an attempt was made to analyze the effect of a bottom-water aquifer on production behavior. It was confirmed that the discrete fracture network model is a useful tool in predicting water breakthrough and remaining oil phenomena.

A remedial method of polymer flooding to prevent cross-flow problem in a layered reservoir

When injecting polymer into an oil reservoir, polymer adsorption onto the grain surface may seriously clog the pore throat and decrease the permeability. This phenomenon may give rise to a severe cross-flow problem in the case of a layered reservoir with a large permeability contrast. Therefore, we proposed a remedial method, which injects polymer solution with different concentrations under the same condition of the frontal velocity at each layer, to overcome the cross-flow problem. In order to perform this task, the experimental system was built as a two-dimensional two-layered sandstone system with a large permeability contrast of 10. From the results of the experimental investigation, conventional polymer flooding was found to be inefficient in oil recovery, because of the cross-flow problem that occurred almost from the beginning of injection. Meanwhile, in the case of the suggested remedial method of polymer flooding, the oil production was significantly enhanced without showing the cross-flow problem, which was accomplished by injecting the polymer solution with different concentrations under the conditions of the same frontal velocity at each layer. Overall, the suggested injecting method was found to be sufficient to overcome the cross-flow problem in a layered reservoir.

CO2 Plume Migration With Gravitational, Viscous, and Capillary Forces in Saline Aquifers

When injecting CO2 in saline aquifers, in order to investigate realistic flow, this study proposes a dimensionless group in the form of combination of Capillary number and Bond number to consider three forces of gravitational, viscous and capillary forces, simultaneously. Using of each dimensionless group individually is insufficient to obtain a satisfactory correlation with flow behavior of injected CO2. With the proposed dimensionless group, the universal profile of CO2 saturation was obtained in describing CO2 flow behaviors for CO2 injection rate, CO2-water interfacial tension, and density difference between CO2 and water. Thus, more realistic CO2 flow behavior was analyzed.