To increase the oil recovery factor (RF), enhanced oil recovery (EOR) methods are applied: chemical, gas, thermal, and combined ones. Standard laboratory research methods for selecting and optimizing EOR technologies require a lot of time and resources, as well as core material, which is often in short supply. To optimize the selection of reagents and field development technologies, the use of microfluidic technology is proposed i.e. conducting experiments in reservoir conditions using microfluidic chips with a porous structure, reproducing the properties of the core of the target field. The main advantages of conducting tests in micromodels are the low duration and the ability to visualize filtration processes, which makes it possible to evaluate the behavior of fluids in reservoir conditions. This paper considers the modern application of microfluidics for the selection of EOR agents and stimulation methods and the status of this technology in the oil and gas industry. The use of microfluidic chips for screening surfactants and polymers, as well as studying the mechanism of low-mineralized water action is described. Conducting microfluidic tests to optimize gas and thermal EOR, which became possible due to the development and improvement of technology, is considered.

Surfactant flooding is among the most studied and widespread EOR technologies that is being introduced into tight and low-permeable reservoirs to mobilize trapped oil. Typically, the selection of formulations for chemical flooding is associated with numerous challenges and constraints such as time-consuming core flooding tests, the high cost of the tests with modern saturation control methods, and a limited amount of core samples. To overcome these issues, microfluidic technology was applied to optimize the screening of surfactant compositions for flooding. The workflow of this project consisted of five main steps: (1) fabrication of microfluidic chips, (2) surfactant screening in bulk, (3) surfactant flooding in microfluidic chips, (4) image analysis and data interpretation. Silicon-glass microfluidic chips, which are 2D representatives of the reservoir porous media, were used in the experiments. The porous structure geometry was developed based on CT images of core samples from a particular field with low permeability. For the selected surfactants, interfacial behavior on the boundary with n-decane was studied and correlated with hydrocarbon recovery ability. The results obtained revealed that the IFT patterns have a significant influence on displacement efficiency. Thus, the surfactant compositions with a lower initial IFT than the equilibrium value achieved higher recovery factors.