Mechanistic Investigation of LSW/Surfactant/Alkali Synergism for Enhanced Oil Recovery: Fluid–Fluid Interactions

Abstract

The combination of chemical enhanced oil recovery (CEOR) and low salinity water (LSW) flooding is one of the most attractive enhanced oil recovery (EOR) methods. While several studies on CEOR have been performed to date, there still exists a lack of mechanistic understanding on the synergism between surfactant, alkali and LSW. This synergism, in terms of fluid–fluid interactions, is experimentally investigated in this study, and mechanistic understanding is gained through fluid analysis techniques. Two surfactants, one cationic and one anionic, namely an alkyltrimethylammonium bromide (C19TAB) and sodium dodecylbenzenesulfonate (SDBS), were tested, together with NaOH used as the alkali, diluted formation brine used as the LSW, and the crude oil was collected from an Iranian carbonate oil reservoir. Fluids were analyzed using pendant drop method for interfacial tension (IFT) measurement, and Fourier transform infrared spectroscopy for determination of aqueous and oleic phase chemical interaction. The optimum concentration of LSW for IFT reduction was investigated to be 1000 ppm. Additionally, both surfactants reduced IFT significantly, from 28.86 mN/m to well below 0.80 mN/m, but in the presence of optimal alkali concentration the IFT dropped further to below 0.30 mN/m. IFT reduction by alkali was linked to the production of three different types of in situ anionic surfactants, while in the case of anionic and cationic surfactants, saponification reactions and the formation of the C19TAOH alcohol, respectively, were linked to IFT reduction. The critical micelle concentration and optimal alkali concentration when using cationic C19TAB were significantly lower than with the anionic surfactant; respectively: 335 vs 5000 ppm, and 500 vs 5000 ppm. However, it was found that SDBS was more compatible with NaOH than C19TAB, due to occurrence of alkali deposition with the latter beyond the optimal point.

Mechanistic Investigation of the Synergy of a Wide Range of Salinities and Ionic Liquids for Enhanced Oil Recovery: Fluid–Fluid Interactions

“…A peak belonging to the dimeric vibration of O–H bond in the carboxylic acid was also observed at 3390 cm –1 . , Carboxylic acids, as one of the main components of crude oil, independently exist in the crude oil structure; however, they can be also generated as a result of the ester hydrolysis. The presence of two peaks at 1459 and 1377 cm –1 in the FTIR results was attributed to the bending vibration of C–H in the methylene and methyl structures, respectively, belonging to the saturated fraction of HCO . The domination of CH and CH 2 stretching bands over CH 3 corresponds to the cyclic structures of the crude oil with a high acid number (2.90 mg KOH·g –1 ) …”

“…On the basis of the results shown in Figure , the presence of carboxyl, phenolic, carbonyl, amine, amide, sulfone, and sulfoxide functional groups could be observed in the crude oil structure. As an instance, the wavenumber between 1600 and 1800 cm –1 represents the carbonyl groups (CO bond), like carboxylic acids and esters . A peak belonging to the dimeric vibration of O–H bond in the carboxylic acid was also observed at 3390 cm –1 . , Carboxylic acids, as one of the main components of crude oil, independently exist in the crude oil structure; however, they can be also generated as a result of the ester hydrolysis.…”

“…As an instance, the wavenumber between 1600 and 1800 cm –1 represents the carbonyl groups (CO bond), like carboxylic acids and esters . A peak belonging to the dimeric vibration of O–H bond in the carboxylic acid was also observed at 3390 cm –1 . , Carboxylic acids, as one of the main components of crude oil, independently exist in the crude oil structure; however, they can be also generated as a result of the ester hydrolysis. The presence of two peaks at 1459 and 1377 cm –1 in the FTIR results was attributed to the bending vibration of C–H in the methylene and methyl structures, respectively, belonging to the saturated fraction of HCO .…”

Recovery Observations from Alkali, Nanoparticles and Polymer Flooding as Combined Processes

“…Therefore, the total acid number (TAN) could be another parameter affecting the R–F/F–F interactions during EOR processes. Some researchers also refer to the saponifiable number (SN), and saponifiable acids, as a more reliable comparative variable [ 61 ]. TAN defines the number of polar compounds, whereas SN refers to the amount of those compounds able to become soap.…”

Enhancing the Oil Recovery from Naturally Fractured Reservoirs Using Viscoelastic Surfactant (VES) Flooding: A Field-Scale Simulation

“…Nanoparticles can be used with the help of surfactants to improve oil recovery, and nanoparticles are also used to improve the performance of surfactants and delay the water breakthrough . Also, low-salinity brines have been extensively studied in order to improve the efficiency of surfactants and polymers, thereby maximizing the oil recovery . Moreover, after the primary and secondary recovery operations, the remaining oil is trapped in the reservoir pores due to the high capillary and viscous forces. , Then, chemical treatments are implemented to reduce the capillary and viscous forces.…”