RESUMEN
Among the Enhanced Oil Recovery (EOR) methods, gas-based EOR methods are very popular all over the world. The gas injection has a high ability to increase microscopic sweep efficiency and can increase production efficiency well. However, it should be noted that in addition to all the advantages of these methods, they have disadvantages such as damage due to asphaltene deposition, unfavorable mobility ratio, and reduced efficiency of macroscopic displacement. In this paper, the gas injection process and its challenges were investigated. Then the overcoming methods of these challenges were investigated. To inhibit asphaltene deposition during gas injection, the use of nanoparticles was proposed, which were examined in two categories: liquid-soluble and gas-soluble, and the limitations of each were examined. Various methods were used to overcome the problem of unfavorable mobility ratio and their advantages and disadvantages were discussed. Gas-phase modification has the potential to reduce the challenges and limitations of direct gas injection and significantly increase recovery efficiency. In the first part, the introduction of gas injection and the enhanced oil recovery mechanisms during gas injection were mentioned. In the next part, the challenges of gas injection, which included unfavorable mobility ratio and asphaltene deposition, were investigated. In the third step, gas-phase mobility control methods investigate, emphasizing thickeners, thickening mechanisms, and field applications of mobility control methods. In the last part, to investigate the effect of nanoparticles on asphaltene deposition and reducing the minimum miscible pressure in two main subsets: 1- use of nanoparticles indirectly to prevent asphaltene deposition and reduce surface tension and 2- use of nanoparticles as a direct asphaltene inhibitor and Reduce MMP of the gas phase in crude oil was investigated.
RESUMEN
Asphaltene often produces problems in upstream and downstream sections of crude oil transportation and processing equipment. These issues are directly related to the asphaltene precipitation in transportation pipelines, separation columns, heat exchangers, and storage tanks. This research investigates the impact of angular frequency and n-heptane concentration on asphaltene precipitation and rheological behavior of two oil samples from the Mansouri oil field in Iran, i.e., 23 and 71. The viscosity tests revealed that these oil samples and their mixtures with n-heptane exhibit Newtonian behavior. Moreover, increasing the n-heptane concentration increases the asphaltene precipitation and dramatically decreases crude oil viscosity. The frequency tests revealed that the presence of n-heptane has an unfavorable effect on crude oil's viscoelastic behavior. Therefore, it is necessary to find the optimum range of angular frequency and n-heptane concentration to minimize the asphaltene content of crude oil and provide them with appropriate viscoelastic behavior. Increasing the angular frequency continuously increases all oil samples' loss modulus and strengthens their liquid-like manner. The experimental results confirmed that the angular frequency higher than 33.6 rad/s and 75% volume concentration of n-heptane is the best condition for the oil sample of 23. On the other hand, the angular frequency higher than 23.4 rad/s and 75% volume concentration of n-heptane is the best condition for the oil sample of 71. In these conditions, the oil samples of 23 and 71 not only have appropriate viscoelastic behavior, but they also experience 97.2% and 96.3% reductions in their viscosity, respectively.
RESUMEN
During the whole life of oil production, enhancing the efficiency and optimizing the production of wells always have been discussed. Formation damage is one of the most frequent reasons for oil wells productivity reduction. This phenomenon can be caused by different factors such as fine migration, drilling mud invasion, asphaltene precipitation, capillary blockage reservoir fluids, and inorganic precipitation. Acidizing and hydraulic fracturing are two conventional well treatment methods usually applied to overcome the formation damage. However, due to destructive side effects of these methods, new methods such as Ultrasonic technology have helped to overwhelm these challenges. The usefulness of this method has been previously proven experimentally and operationally, but the effect of this technology on the pore structure has not been completely explored yet. In this paper, the effect of the ultrasonic wave on the pore structure during well stimulation is investigated. For this purpose, five samples of carbonate and sandstone with different rock textures were investigated to determine the effect of ultrasonic waves on flow behavior and microscopic pore structure through absolute permeability test, scanning electron microscope (SEM) images and petrography. The results showed that ultrasonic waves may affect pore structure through; initiation of micro-fracture and/or detachment of rock particle. The micro-fracture initiation is expected to increase the permeability while the detached particle may reduce or increase permeability through the clogging or opening the pore throat. For example, it was observed that ultrasonic waves significantly increase the permeability of Oolitic carbonate samples, while the controversial changes were observed in sandstone samples.