| In this paper, the research of depth profile control gel system is carried out under the condition of sewage, through the indoor experiments, the selected gel formula is suitable for the sewage condition of the oil production factory in daqing oil field to meet the needs of the field displacement. And the surface active agent that commonly used in the oilfield is selected which have good thermal stability, strong salt resistance and good property of emulsion, it is used for the surface active agent flooding. Through the two parallel pipe core experiments,the displacement effect and the sealing ability of different chemical flooding methods are studied to provide certain theoretical basis for improving the recovery efficiency and the water control.Firstly, under the condition of sewage in the oil production company of Daqing oilfield,it is studied that the effect of the components in the organic acid of chromium gel system that impact on the gel performance, and the reasonable concentration range of the components is determined. By the basis of single factor experiments, through the orthogonal experiments,the influence degree of the components on the gel properties is studied to optimize the recipe.We optimize the gel formula again to select the gel system that can meet the displacement need at the scene and have a good economic value. Considering the performance of the gel and the economy, finally we select the optimization of the gel formula is that the polymer concentration is 1200 mg/L, crosslinking agent concentration is 30 mg/L, crosslinking agent molar ratio is 1:10, pH value is 7, stabilizer concentration is 800 mg/L. Then, the properties of the gel are evaluated. The gel time, viscosity stability, resistance to salt, shear resistance and plugging rate of the gel are studied respectively. The optimized gel system has a long gel time, the gel viscosity is up to 2100 mPa·s in the 24 hours, the highest viscosity can reach above 3000 mPa·s, and it has good stability, the gel viscosity retention rate is about 80% after30 days. The salinity have a little effect on the gel properties in the salinity range of the experiments. After shearing, the gelling time of the gel system is about 1.7 times of the static gel system, and the viscosity after gelling is lower than the static gel system, but it still has a good viscosity. The gel has a good sealing performance, the plugging rate can reach more than 80% in different permeability cores.Secondly, we choose the betaine amphoteric surfactants which used as low interfacial tension surfactants, And it is evaluated that the ability to reduce the interfacial tension, and the viscosity, interfacial tension stability and emulsifying properties. When the betaineamphoteric surfactant concentration reach 0.1~0.8%, the oil/water interfacial tension value can reach about 1×10-3, that can meet the requirements of Daqing oilfield. The viscosity of binary compound system after 90 days is about 16.5 mPa·s, and interfacial tension can reach about 4.8210-3×mN/m, The system stability and the emulsifying performance are good.Finally, through the two parallel tube core displacement experiments, the plugging ability and the improving recovery ability of different chemical flooding methods are studied.The results show that, the improved recovery rate from large to small order is binary flooding(19.08%) > CDG flooding(17.84%) > the polymer flooding(15.10%) > the CDG and binary alternating flooding method(14.55%) > the CDG and surface active agent alternating flooding method(12.03%) > polymer and surface alternating flooding(9.32%) > surface active agent flooding(5.06%). The plugging ability of the gel is better than the polymer, the gel has the good profile control effects. Binary compounds flooding need a large chemical reagent dosage, and improve the recovery ratio is greater than the alternating injection displacement mode. But considering the injection pressure and economy, we propose the mode of gel and surface active agent alternating injection method. |
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