Estimation of low salinity water flooding efficiency to improve oil recovery in sandstone reservoir in Kazakhstan

Background: The regular increase in demand for hydrocarbons necessitates the introduction of optimal technologies to improve the development of reserves. The method of utilization of water with low salinity as an injected agent seemed promising in solving this issue. Aim: The aim of this article is to assess the potential of low-salt water to increase production and oil recovery in the terrigenous field of Kazakhstan. Materials and methods: For the study, low-salinity water injection into the reservoir was simulated on the ECLIPSE 100 simulator. The impact of salt concentration on production and oil displacement efficiency in the considered field during the secondary injection were determined by simulating flooding of solutions with different salinity. The model has been running for 18 years. Analysis of salinity reduction efficiency was carried out by comparing oil recovery after flooding with high salinity water. Results: The decrease in water salinity led to an increase in oil recovery by 1.3–2%. Such a slight increase in production is due to the initial hydrophilic properties of the rock. To obtain a response from the contact of low-salt water with rock, the presence of adsorbed oil on the surface of minerals is required. It can be said with high probability that in this reservoir, an increase in the oil recovery factor with a decrease in salinity is due to active interactions at the oil-water interface, one of which is an increase in viscoelastic properties. Conclusion: A slight difference in the efficiency of oil displacement between the studied low-salinity waters indicates the presence of the optimal salinity of the injected water. The initial hydrophilic property of the reservoir rock surface excludes wettability change as a reason for the increase in oil production. Further study of low-salt water flooding on core material from the studied field is recommended to obtain accurate data and understand how low salinity can affect the distribution of oil in the rock.

low salt water, low-salt water flooding, terrigenous reservoir, mechanisms, relative permeabilities, wettability, viscoelasticity