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Cyclic waterflooding has received recent attention since many studies and field tests have shown that it may lead to additional oil recovery at virtually zero additional cost. Even though the process is in principle very similar to conventional waterflooding, there are interesting new effects taking place under the pulsed conditions that need to be properly quantified for a realistic field deployment of the cyclic injection process. Two-phase immiscible pulsed flow experiments performed on homogenous packed glass beads cells are compared with flow behaviour under continuous injection. In the pulsed experiments, injection is switched on/off using a timing device in the pumping system. Symmetric cyclic periods and different injection rates were used in the study. Initially the dry packed cells were flushed with CO2 and saturated with water. This was followed by injection of oil up to leaving the cells at irreducible water saturation conditions. Then water was injected and the amount of produced fluids measured. Separate experiments under continuous and pulsed injection conditions with visual monitoring of fluid displacement were performed. It is found that the amount of oil recovered at intermediate stages (after breakthrough and less than 3 pore volumes of injected water) is larger for the pulsing mode. The final recovery for both injection processes is similar within the experimental error. In the pulsed experiments, during the off injection period, spontaneous fluid spreading was observed leading to smoother displacement fronts compared to continuous injection. Also, displacement fronts were found to be more stable under pulsed conditions. The study concludes that residual oil saturation under pulsed injection can be reached earlier than under continuous injection, a result very attractive for field application. Experimental findings of this work shed light in the design of cyclic injection processes. Introduction Cyclic water injection is being considered as a potential alternative to the inherent difficulties of waterflooding since it may lead to additional oil recovery. The process itself was proposed a few years ago, and has been tested successfully in some reservoirs in USA, Russia and China, where additional recoveries in the range 2–18% have been reported, with the additional benefit of a decrease in water cut levels. Even though the process is in principle very similar to waterflooding, there is still a lack of understanding on the role of certain parameters and operational variables. Among those we may cite: reservoir wettability initial oil and water saturation, saturation history effects, oil viscosity, cyclic period selection, and reservoir heterogeneity. Cyclic water injection refers to a process in which the injection rates are changed from high to low values and then back to high, in a periodic fashion, allowing the pressure maintenance support required in the water injection process. The cyclic periods are in the range of weeks to months, a different time scale from the so called pulsed pressure technique, where short pressure pulses are applied in time intervals of a few minutes. Several authors have simulated the cyclic injection process for a variety of operational conditions. However, only few experimental works have been reported quantifying the role different variables on the process, and to clearly establish the differences with continuous waterflooding. Visualization experiments are particularly appropriate to address such objectives allowing capturing fine details about the dynamics of flow displacement. After a literature review we present the methods and the properties of the porous media and fluids used in the experiments. The cyclic water injection process is compared with the results obtained in a conventional waterflooding experiment under conditions where the same amount of fluid is injected in each case. The effect of bead size, injection rate, oil viscosity, cyclic period is reported and analyzed. Displacement front stability is addressed in the discussion section.

The paper presents a promising method of removing undesirable tensile residual stresses in aircraft metal structural elements; the basis of the method is the action of pulsating subsonic gas flows on the surface of these elements. The results of the research showed high effectiveness of controlling residual stresses in aircraft metal structural elements by using pulsating subsonic air flows.

This paper presents the results of a study of the effect of pulsating subsonic gas flow treatment on the corrosion resistance of structural metal materials used in aircraft structural elements. The disadvantage of even the most modern methods of increasing the structural strength of metal materials is an insufficient increase in corrosion resistance. An urgent task is to develop methods for increasing the corrosion resistance of aircraft structural elements throughout their volume without additional alloying, which not only increases the cost of the product material, but also, often, makes it less producible, which can be used during the restoration of both aviation and airfield equipment. The article describes a method developed by the authors to increase corrosion resistance using pulsed subsonic gas flows. The data obtained as a result of the conducted research will allow more effective control of the corrosion condition of aircraft by non-destructive methods, as well as increase the accuracy of forecasting the technical condition.