Experimental Study On Supercritical And Miscible Carbon Dioxide Flooding Characteristics Based On Micro-CT Technology

With the continuous development of modern social industry,people's demand for energy is increasing,and the emission of greenhouse gas CO₂ continues to increase.The use of supercritical CO₂ flooding can effectively improve oil recovery?EOR?and achieve landfill.The purpose of CO₂ has therefore become an important issue.In the enhanced oil recovery?EOR?study of CO₂,experimental research on the seepage characteristics of CO₂ in porous media has become one of the important ways.In this paper,the displacement experiments of CO₂ throughput,supercritical CO₂ foam and mixed CO₂ in porous media were carried out,and the oil displacement under different displacement pressures was obtained.The CT technology was used to scan different porous media during the experiment.The gray value at different times,combined with the experimental data,obtains the three-phase saturation at different times.The experiment has important guiding significance for supercritical CO₂ flooding,CO₂ miscible flooding and CO₂ huff and puff mining under underground reservoir conditions,and provides valuable experience for enhanced oil recovery technology?EOR?.The experimental results show that:?1?CO₂ throughput method has obvious enhanced recovery effect on dense porous medium oil phase;when CO₂ is used as displacement medium to displace oil phase in dense porous medium,the mixed phase effect of CO₂ and crude oil is affected by pressure When the replenishing pressure is 20 MPa,a better displacement effect than the replenishing pressure of 14 MPa can be obtained.?2?When the system pressure is 13 MPa,the liquid paraffin and supercritical carbon dioxide fluid can reach the mixed phase in the saturated oil core at 50°C;In the comparative experiments using supercritical carbon dioxide foam,it was found that the effect of supercritical carbon dioxide foam displacement after using supercritical carbon dioxide fluid mixed phase displacement was not obvious.According to the pressure difference measured by the pressure sensor,the N₂ foam has a larger displacement pressure difference than the supercritical CO₂ foam.Nitrogen has good foaming properties.?3?The use of liquid CO₂ for displacement can effectively improve oil recovery,and increase inlet pressure can improve oil displacement efficiency;In the case where the parameters such as the voltage,the current,and the placement position of the CT are kept constant,the density of the measured object is larger,and the gray value of the processed CT image is larger;At lower pressures?7 MPa?,the CO₂ fluid only displaced 36.7%of the fluid.As the system pressure increases,its displacement effect gradually increases.When the system pressure reaches 20 MPa,the gas phase saturation can reach 63.1%.Compared to the aqueous phase in the core?from 0.274to 0.084?,the displacement of the CO₂ fluid to the oil phase is more pronounced?from 0.726 to 0.285?.