Hyemin Park

Optimum design of multi-stage hydraulically fractured multi-horizontal shale gas well using flow regime analysis

Optimum horizontal well spacing and fracture spacing are obtained through characterizing the changes in flow regime caused by pressure interference in multiple transverse fractured horizontal wells. To obtain this aim, appropriate hydraulic fracture spacing was calculated by using flow regime characteristic called pseudo pseudosteady state where the pressure interference between neighbored two fractures. In addition, the fracture spacing calculated for the shale gas reservoir with permeability of 0.0001 md was applied to calculate the horizontal well spacing when two wells were drilled. Through the calculated optimum fracture spacing and well spacing, we determined the optimal number of horizontal wells in a shale gas reservoir and presented the estimated ultimate recovery.

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.

Effect of miscibility condition for CO2 flooding on gravity drainage in 2D vertical system

In CO2 flooding process, gravity drainage and miscibility condition are the main factors on the efficiency of oil recovery. In this study, we observed oil recovery for different miscibility conditions in vertical oil reservoir. This was investigated in two dimensional vertical sandstone slab, where unstable gravity drainage phenomena can be formed. CO2 is injected at bottom into 100% saturated with oil and production port is open at top of the system. We have performed a series of experiments using continuous CO2 flooding for immiscible and near-miscible conditions. From the experimental results, oil recovery at near-miscible condition is 3.77 times greater than at immiscible condition, particularly in vertical system. It indicated that applying the immiscible CO2 flooding is ineffective because of gravity override of CO2 and generation of CO2 channel at upper side in vertical reservoir. Meanwhile, the results revealed that oil recovery increases considerably once miscibility is reached at outlet. That is, miscibility condition is found to be a sensitive factor on oil recovery particularly in vertical oil reservoir.

Effects of the imbibitional flow of steam on oil recovery from carbonate reservoirs

Carbonate reservoirs contain over 90% of oil within an extremely tight matrix and are usually oil-wet, which makes them unfavorable for oil production. During water injection, water does not imbibe into the matrix, but flows preferentially through the fractures, resulting in very low oil recoveries. It is proposed that steam or hot water is injected, inducing a wettability change and rendering the matrix water-wet. Then, water can move into the matrix by capillary imbibition. From this perspective, it is crucial to analyze the contributions of conductive and convective heat transfer during steam injection. The mechanism of wettability changes is accounted for when steam is injected into carbonate reservoirs. The effect of strong capillary pressure in a tight matrix on the oil recovery is also examined. The purpose of this study is to evaluate the rate of conduction and convection and to determine optimum conditions that maximize heat transfer and wettability alteration in the tight matrix. An analytical solution and numerical results were compared for heat conduction within the matrix during steam injection. Investigations were also performed to determine the optimum injection time, steam injection pressure and steam quality required to make the carbonate matrix water-wet and maximize oil recovery. The results from this study show that convectional flow might be the most important heat-transfer mechanism to shorten the matrix wettability converting time. Based on analysis of the thermal process, an optimum steam injection strategy can be designed for a given matrix permeability and fracture spacing.

Efficiency of enhanced oil recovery by injection of low-salinity water in barium-containing carbonate reservoirs

When low-salinity water containing sulfate ions is injected into carbonate reservoirs, rock dissolution and in situ precipitation occur, altering rock permeability and wettability. Particularly, when barium ions are present in formation water, they react chemically with

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

{\text{SO}}_{4}^{2 - }

Effect of polymer concentration on the polymer adsorption-induced permeability reduction in low permeability reservoirs

SO42-, and BaSO4 is precipitated. These reactions can cause a serious impact on the efficiency of enhanced oil recovery (EOR). Therefore, the main purpose of this study was to identify EOR efficiency induced by low-salinity waterflooding (LSWF) when Ba2+ is present in carbonate reservoirs. From the experimental results, it was confirmed that the permeability calculated by the measured pressure difference was improved because of rock dissolution predominating over in situ precipitation for the case of low Ba2+ concentrations. In the analysis of wettability alteration through the measurements of relative permeabilities before and after LSWF, the higher Ba2+ concentration case consumed more