Properties of N2- and CO2-foams as a function of pressure

• Published in: Journal of petroleum science & engineering 2014-04, Vol.116, p.72-80
• Main Authors: Aarra, Morten Gunnar, Skauge, Arne, Solbakken, Jonas, Ormehaug, Per Arne
• Format: Article
• Language: English
• Subjects: Applied sciences; CO2-foam; Crude oil, natural gas and petroleum products; Energy; Exact sciences and technology; Foam; Foam core flood experiments; Foam mobility reduction factor; Fuels; Gas blocking; Water blocking
• ISSN: 0920-4105; 1873-4715
• DOI: 10.1016/j.petrol.2014.02.017

In enhanced oil recovery (EOR) operations foam has been applied to improve sweep during gas injection or for gas shut-off. Field experiences for North Sea reservoirs involve foams using hydrocarbon gas for conformance control and gas blocking in high pressure and high temperature fields. Generally foam field applications have utilized CO2 and N2 in addition to hydrocarbon gas. As reservoir conditions vary significantly it is important to understand foam properties on a broad experimental basis. The large changes in physical properties with temperature and pressure may affect CO2-foam properties and these are discussed by varying pressure from 30 to 280bar in an outcrop Berea sandstone core material at 50°C. The CO2-foam properties were compared to N2-foams. Foam was generated by co-injection of surfactant solution (AOS) and N2 or CO2 at 80% foam quality (fraction gas) at a total injection rate of 40ml/h. Strong N2-foams were generated both at 30 and 280bar. In general, N2-foams were stronger than CO2-foams. Comparing CO2-foams at different pressures showed that CO2-foams at 30bar were strong (MRF ~50–75) whereas supercritical CO2-foams gave MRFs in the range of 3–6. The visual foam structure observations from a sight glass at the core outlet showed denser N2-foams compared to CO2-foams. Injecting seawater after N2-foam showed that relative seawater permeability was low and remained low (