Foam stability and foam structure under high pressure for tertiary oil production - Foam analysis under pressure up to 35 MPa
Martina Szabries, TU Bergakademie Freiberg
Svenja Sergelius, Arne Kordts, Krüss GmbH
Foam properties such as stability, structure, foamability and bubble size distribution depend, among other things, on the type and phase behavior and concentration of the stabilizing surfactant, on the salt content as well as on additives such as polymers and finally on the temperature.
When foams are used in tertiary oil production, a further factor occurs that hardly plays a role in conventional foam analyses: the pressure prevailing in a reservoir, which leads to a completely different foamability and above all stability behavior compared to standard conditions. The influence of this particularly important parameter has so far only been investigated to a limited extent due to a lack of available measurement technology.
With the High Pressure Foam Analyzer - HPFA, analyses of the formation, stability, and structure of liquid foams at up to 35 MPa and 120 °C have recently become possible in a single measurement. In this study, we present the first investigations on the pressure-dependent foaming behavior carried out with this instrument. The focus is on measurements of foam height and structure as well as time-dependent analyses of the relative foam height and mean bubble size of aqueous nitrogen foams.
Reproducibility measurements provide well consistent results. Furthermore, the influence of the gas type for the most important gases nitrogen (N2) and carbon dioxide (CO2) on the foam behavior was investigated.
In order to use foams in tertiary oil production, the dispersion of gas bubbles in aqueous surfactant solution must be stable over a longer period of time and against the extreme conditions present in the deposit, such as high salinity, temperatures, and pressures. Before the multiphase flow in the pore space including all interactions with the rock matrix can be investigated, the behavior of the fluid phase (bulk foam) should be known. Depending on the surfactant-gas system used, pressure, temperature, various additives and interactions with salts and crude oils play a role.