Investigation On Microscopic Oil Displacement Mechanism Of Foam Fluid In Heavy Oil Reservoir

Nowadays,the proportion of heavy oil resources in the world’s oil reserves is continuing to rise,and the efficient development of heavy oil reservoirs is also receiving increasing attention.As a widely used heavy oil reservoir development method,the foam flooding technology can effectively develop heavy oil resources and further improve crude oil recovery.From a micro perspective,the mechanism of foam flooding is an important basis for achieving the EOR effect.Therefore,research on the foam fluid microscopic oil flooding mechanism under the conditions of heavy oil reservoirs is of great significance to further optimize the foam flooding technology.This article first recorded the viscoelastic squeezing and adsorption phenomena between foam and heavy oil at a microscopic angle by using the micro-mechanical force measuring instrument,and measured the changes in the microscopic force between foam and heavy oil during the process.The influence of surfactant concentration,crude oil viscosity,the mixing of HPAM polymer and Si O₂ nanoparticles on the force was discussed,and the influence mechanism of temperature and pressure on the force between fluids was also studied.Later,through the micro-etched glass model oil displacement experiment,the dynamic characteristics of foam fluid displacement of heavy oil were studied,and the model was established by referring to the fluid mechanics formula,and the foam-heavy oil micro force under the experimental conditions was fitted and calculated.Finally,through one-dimensional sand-packing model flooding experiments and two-dimensional sand-packing model flooding experiments,the characteristics of different types of foam systems which aim to displace heavy oil were studied,and the effect mechanism of surfactant concentration,polymer and nano-particles on the macroscopic effect of foam flooding heavy oil was analyzed.The research results showed that foam could produce various viscoelastic micro-forces with heavy oil.The increase of surfactant concentration and the increase of crude oil viscosity would significantly increase the force,and polymers and nanoparticles would further strengthen the force,with an increase of 65.2-80.8%;and the increase in temperature and pressure would cause the force to drop to a certain extent.Etching model oil displacement experiments confirmed that the foam in the pore throat exerts force on the heavy oil in various dynamic forms such as adsorption,stretching,and cutting to realize the displacement process;At the same time,the theoretical model established in this paper could fit the microscopic force between foam and heavy oil with an error of 5-8%.One-dimensional and two-dimensional sand filling model experiments further showed that the increase in the concentration of surfactants,polymers and nanoparticles could significantly improve foam fluidity,thereby optimizing foam flooding energy and crude oil production capacity,and improving foam flooding recovery rate,in this experiment,the heavy oil recovery rates of ordinary foam,polymer foam and nanoparticle foam were about 58.32%,68.16%,and 63.77%,respectively,which confirmed the applicability of foam flooding to the development of heavy oil reservoirs.