Low tension water flood LTWF for enhanced oil recovery in a tight carbonate oilfield

A. A. Al-Rubkhi, M. Karimi, M. Hadji, R. S. Al-Maamari, M. Aoudia

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The aim of this study is to develop and optimize a low tension water flood (LTWF) as an option for enhanced oil recovery in a tightcarbonate oilfield using a mixture of formation brines as injection water (total salinity: 165.9 g/L, Ca2+: 12.3 g/L, Mg2+: 2.0 g/L, and T = 70 °C.). In our approach, a combination of an anionic surfactant (alkyl ether sulfonate, C17EO7S(C17EO7) and a nonionic surfactant (alkyl ether, iC13EO10) were used to formulate clear and stable surfactant solutions at reservoir conditions. Formulation and optimization of a LTWF at a very low total surfactant concentration (0.01 wt%) was achieved through surfactant/brine compatibility tests (target: clear and stable surfactant solution), surfactant solution/oil interfacial tensions (target: ∼ 10-3 mNm-1), phase behavior (target: Type II(-) oil-in-water microemulsion) and core flooding experiments. Compatibility tests showed that the cloud point of the nonionic surfactant (0.01 wt%)is lower than the reservoir temperature (70 °C) whereas the clear point of the anionic surfactant is above the boiling point of water, suggesting that both surfactants cannot be used alone at reservoir conditions. On the other hand, clear and stable mixture of anionic/nonionic surfactants in the composition range fw = 0.1-0.8 (fw being the weight fraction of the nonionic surfactant) at 0.01 wt% total surfactant concentration were generated above 70 °C. Clear, transparent and gel-free oil-in-water phase behavior with relatively high oil solubilization parameters (o ~ 125) were observed for surfactant mixture (0.01 wt%, fw = 0.1-0.8). These phase behaviors tests were validated by interfacial tension (IFT) measurements. Ultralow IFT (~ 10-3mN/m) was achieved at fw = 0.2. This optimum system was selected for core flooding experiments. Injecting surfactant (0.5PV) slug into a fully water flooded carbonate core sample resulted in additional oil recovery of 10 % of OOIP. This is a very significant result owing to the low surfactant concentration used (0.01 wt%). In another experiment, injecting a surfactant slug (0.5 PV) before water injection resulted in a total recovery of 75% of OOIP. In addition, Amott-Harvey test showed that wettability indices of the core plug samples used in the experiments changed within a narrow range (- 0.231 to + 0.164); suggesting an alteration of wettability from slightly oil-wet to weakly water-wet state.

Original languageEnglish
Title of host publicationSociety of Petroleum Engineers - SPE EOR Conference at Oil and Gas West Asia, OGWA 2016
PublisherSociety of Petroleum Engineers
ISBN (Print)9781613994450
Publication statusPublished - 2016
EventSPE EOR Conference at Oil and Gas West Asia, OGWA 2016 - Muscat, Oman
Duration: Mar 21 2016Mar 23 2016

Other

OtherSPE EOR Conference at Oil and Gas West Asia, OGWA 2016
CountryOman
CityMuscat
Period3/21/163/23/16

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ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Fuel Technology
  • Geochemistry and Petrology

Cite this

Al-Rubkhi, A. A., Karimi, M., Hadji, M., Al-Maamari, R. S., & Aoudia, M. (2016). Low tension water flood LTWF for enhanced oil recovery in a tight carbonate oilfield. In Society of Petroleum Engineers - SPE EOR Conference at Oil and Gas West Asia, OGWA 2016 Society of Petroleum Engineers.