Reduction of Surfactant Retention in Limestones Using Sodium Hydroxide

Abstract

Summary Geochemical modeling was used to design and conduct a series of alkaline/surfactant/polymer (ASP) coreflood experiments to measure the surfactant retention in limestone cores using sodium hydroxide (NaOH) as the alkali. Surfactant/polymer (SP) coreflood experiments were conducted under the same conditions for comparison. NaOH has been used for ASP floods of sandstones, but these are the first experiments to test it for ASP floods of limestones. Two studies performed under different reservoir conditions showed that NaOH significantly reduced the surfactant retention in Indiana Limestone. An ASP solution with 0.3 wt% NaOH has a pH of approximately 12.6 at 25°C. The high pH increases the negative surface charge of the carbonate, which favors lower adsorption of anionic surfactants. Another advantage of NaOH is that low concentrations of only approximately 0.3 wt% can be used because of its low molecular weight and its low consumption in limestones. Most reservoir carbonates contain gypsum or anhydrite, and therefore sodium carbonate (Na2CO3) will be consumed by the precipitation of calcium carbonate (CaCO3). As shown in the two studies, NaOH can be used in limestone reservoirs containing gypsum or anhydrite.

Comprehensive review on surfactant adsorption on mineral surfaces in chemical enhanced oil recovery

“…233,238,239 However, recent studies on Indiana limestone suggested the use of NaOH to lower the surfactant retention. [240][241][242] The reasons for NaOH selection were the higher pH of NaOH compared with Na2CO3 or ammonia, suppressing and slowing down the dissolution of calcite, and less alkali consumption by calcite, dolomite, and quartz. In the meantime, NaHCO3 is a good choice for reservoirs containing clay minerals.…”

A new surfactant wettability alteration model for reservoir simulators

“…In the base case, the pK A is 6 and the initial pH is 7, so the concentration of aqueous soap is 10 times that of aqueous acid. a K2i , the coefficient controlling the effect of pH on the adsorption constant, was estimated to be À0.15 from the combined data in Wang et al (2019) and Maubert et al (2018), compiled in Wang (2018). The surfactant retention in carbonate rocks decreases by a factor of approximately 1/3 when the pH is increased from 8 to 11.…”

Synergistic Effects of SiO2-Rhamnolipid Nanofluid on Oil-Water Distribution in Low-Permeability Reservoirs

“…Surfactant flooding is a time-tested method to lower residual oil saturation via reducing oil/water interfacial tension and altering the reservoir wettability. , However, there are some challenges to overcome, including the loss of surfactant molecules on rock surfaces, - surfactant intolerance to reservoir conditions, - and limited efficacy in mobilizing trapped oil within small pore spaces. , Especially in low-permeability reservoirs, the application of surfactant is further hindered by extreme environmental conditions. As compared to surfactant, nanoparticles exhibit superior robustness and stability.…”