Surfactant-Gas Hybrid Enhanced Oil Recovery for Meramec Shale: A Comprehensive Laboratory Study on Surfactant Selection and Performance

Document Type

Conference Proceeding

Publication Date

1-1-2025

Abstract

Surfactant enhanced oil recovery is gaining tremendous momentum in its application to liquid-rich shale reservoirs. This requires an extensive surfactant selection procedure to delineate appropriate surfactants and quantify their performance. This study focuses on an extensive surfactant selection study on Meramec shale rock in the Anadarko basin. The study results in identifying a surfactant that performs the best amongst others in terms of wettability alteration, interfacial tension reduction, and spontaneous imbibition. This quantifies the rate and extent of oil recovery by the selected surfactant. The study is also extended to a core flood experimental investigation of the application of Hybrid enhanced oil recovery, where Carbon Dioxide gas is injected along with surfactants in an alternating sequence. This investigation focuses on the impact of gas and surfactant on each other in the hybrid enhanced oil recovery technique. This study or investigation includes wettability studies by contact angle measurements, interfacial tensions measurements, static, spontaneous imbibition measurement in an Amott cel, and a high pressure - high temperature core flood experiments. This also includes extensive mineralogical analysis which play a crucial role in surfactant performance. Rock samples from Meramec’s silica rich zone were aged in in-situ oil until the samples showed oil-wet condition. Multiple surfactants (nonionic and cationic) were tested for their wettability alteration and interfacial tension reduction capability. The results were used to select an optimally performing surfactant which was then used for a comparative spontaneous imbibition test against distilled water. The surfactant was further used in a Hybrid enhanced oil recovery core flood study where it was injected alternatingly with Carbon dioxide. The wettability studies show that all the surfactants tested alter wettability of the rock sample. All surfactants also show interfacial tension reduction compared to the measurement in distilled water. The two cationic surfactants and one nonionic surfactant with 12 ethoxylate head groups (NP-12) show the greatest wettability alteration and interfacial tension reduction. Extremely low interfacial tension will also reduce the capillary forces required to mobilize the fluids in pore space. Hence, non-ionic surfactant with 20 ethoxylate head groups (NP-20) is used, with good wettability alteration and reasonable interfacial tension capability, is selected for further spontaneous imbibition studies. When compared with distilled water, the selected non-ionic surfactant solution (NP-20) showed a greater rate and extent of oil recovery during spontaneous imbibition. The NP-20 surfactant solution was further used to investigate a hybrid enhanced oil recovery where the solution was alternatingly injected with CO2 into the silica rich Meramec core plug. The impact of sequence of injection was investigated: surfactant followed by gas injection and gas injection followed by surfactant. This investigation shows the effect of CO2 and surfactant solution on each other. The results show that surfactant recovers heavier hydrocarbons, and CO2 recovers relatively lighter hydrocarbons. Injecting gas first followed by surfactant solution minimizes the extent of oil recovery by surfactants due to possible mobility reduction because of vaporization and recovery of lighter fractions of oil by the former gas injection.

Publication Source (Journal or Book title)

Society of Petroleum Engineers SPE AAPG Seg Unconventional Resources Technology Conference Urtc 2025

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