Abstract
The need for optimal recovery of crude oil from sandstone and carbonate reservoirs around the world has never been greater for the petroleum industry. Water-flooding has been applied to the supplement primary depletion process or as a separate secondary recovery method. Low salinity water injection is a relatively new method that involves injecting low salinity brines at high pressure similar to conventional water-flooding techniques, in order to recover crude oil. The effectiveness of low salinity water injection in sandstone reservoirs depends on a number of parameters such as reservoir temperature, pressure, type of clay particle and salinity of injected brine. Clay particles present on reservoir rock surfaces adsorb polar components of oil and modify wettability of sandstone rocks to the oil-wet state, which is accountable for the reduced recovery rates by conventional water-flooding. The extent of wettability alteration caused by three low salinity brines on oil-wet sandstone samples containing varying clay content (15% or 30%) and type of clay (kaolinite/montmorillonite) were analyzed in the laboratory experiment. Contact angles of mica powder and clay mixture (kaolinite/montmorillonite) modified with crude oil were measured before and after injection with three low salinity sodium chloride brines. The effect of temperature was also analyzed for each sample. The results of the experiment indicate that samples with kaolinite clay tend to produce higher contact angles than samples with montmorillonite clay when modified with crude oil. The highest degree or extent of wettability alteration from oil-wet to intermediate-wet state upon injection with low salinity brines was observed for samples injected with brine having salinity concentration of 2000 ppm. The increase in temperature tends to produce contact angles values lying in the higher end of the intermediate-wet range (75°–115°) for samples treated at 50 °C, while their corresponding samples treated at 25 °C produced contact angle values lying in the lower end of intermediate-wet range.
Highlights
Low salinity water flooding (LSWF) is one such modified application of traditional water flooding techniques
The uneven distribution of clays throughout the sandstone reservoir rocks have made it difficult to study the exact impact of each clay particle and that the amount of clay content has on wettability alteration
The naturally water-wet mica powder to the oil-wet state was naturally water-wet mica powder to the oil-wet state was analyzed analyzed by measuring contact angles ofsamples
Summary
Low salinity water flooding (LSWF) is one such modified application of traditional water flooding techniques. During the process of LSWF, cations are exchanged between the clay minerals and low salinity brines. The lower concentration of cations present in injected brine causes the equilibrium established between connate water and reservoir rocks to be disturbed, resulting in the cation exchange reactions. The cation exchange reactions result in desorption of polar components of oil from negatively charged clay surfaces and they are replaced by the cations from low salinity brine. To evaluate the role of content (concentration) of individual clay particles such as montmorillonite and kaolinite in modifying the wettability of sandstone rocks. To evaluate the pattern of variation in the values of contact angles measured for each sandstone sample (having different clay content) that are injected with three brines of varying low salinity concentrations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
