Enhanced oil recovery (EOR) is a crucial technology in the petroleum industry, influenced by several factors, including flooding fluids and methods. The adjustment of injection strategies and the application of vibration stimulation can significantly impact oil recovery, especially residual oil. In this study, we conducted experiments using a glass micromodel to investigate the effect of pulsing water injection on oil recovery. Our results show that when the pulse frequency matches the natural frequency of the micromodel, resonance occurs during the two-phase flow of pulse driving, which causes an increase in the amplitude of oscillation, enhances the mobility of oil, and improves recovery. The efficiency of the kinetic energy of displacement is also improved. However, when the frequency is 3 Hz, the absence of resonance leads to the opposite effect. In addition, we found that a greater amplitude increases the fluidity of oil. These findings have significant implications for the design of EOR strategies and methods. Our experimental results provide insight into the effect of pulse water injection on oil recovery and offer a potential strategy for the optimization of EOR techniques.

In China, sandstone geothermal reservoirs are large in scale and widely distributed, but their exploitation is hindered by low recharge efficiency. In this paper, an unblocking and permeability enhancement technology using a rotary water jet for low recharge efficiency wells in sandstone geothermal reservoirs is proposed to solve this problem. This paper presents a series of studies about the proposed technology, including experiments, simulation and field application. Firstly, an experiment was carried out to verify the scale removal effect of a high-pressure water jet on the inner wall of the screen tube and its impact on sandstone. Secondly, the numerical models of the rotary jet flow field in the wellbore were established by ANSYS Fluent to study the influence of parameters. Finally, based on the simulation and experiment results, a rotary jet tool applicable to unblocking and descaling low-efficiency wells was designed, and a field application for low-efficiency wells in sandstone thermal reservoirs was conducted. The study results show that the unblocking and permeability enhancement technology using a rotary water jet is effective in removing the blockages and improving the permeability near the well. In conclusion, the presented technology can solve the problem of low efficiency during the reinjection of cooled thermal waters back into sandstone geothermal reservoirs and has great effectiveness in field application.

Simulation of the effect of stand-off parameter on collapse behaviours of a single cavitation bubble in jet drilling