An Investigation of Oil Destabilization of Nitrogen Foams in Porous Media

Abstract

When applied as conformance treatments, foams are required to effectively reduce gas injectivities over prolonged periods of time. Frequently, this ability must be manifested in the presence of a residual oil saturation which often exerts a destabilizing effect on foam and the capacity to generate foam. In this study, the capacity to generate and sustain foam in the presence of a residual oil saturation was examined by each of two methods. The first method monitored the in-situ generation of nitrogen foam at constant pressure drop for 1-ft Berea cbres at a residual oil saturation to surfactant. Gas mobility reduction, foam longevity, and the rate of foam decay were quantified for a variety of surfactants and oils at constant salinity and concentration at room temperature. The second procedure involved the constant quality injection of pregenerated foams into Berea cores at residual oil saturation to water flooding. The liquid requirement to reach steady state and the absolute pressure drop were determined under test conditions identical to the aforementioned method. In each method, foam stability showed a strong sensitivity to surfactant, oil type, in-situ foam quality and oil desaturation kinetics. In a companion laboratory study, the degree of correlation between these results and a variety of benchtop measurements was established. Benchtop measurements included interfacial and surface tensions, film elasticities, oil spreading, pseudoemulsion film drainage times, and film disjoining pressure for oil equilibrated and nonequilibrated surfactant solutions. From these studies, it is concluded that foam destabilization by oil is dictated primarily by pseudoemulsion film stability. The relative stability of the pseudoemulsion films in-situ, however, is dependent upon the prevailing pore level conditions of oil and liquid saturation. Oil spreading, wave dampening, and lamellar film strength had little effect on foam stability to oil. Given this information, one can easily choose test design criteria upon which to screen surfactants for foam conformance treatments in the presence of oil.

Core Flood Evaluation of Solvent Compositional And Wettability Effects On Hydrocarbon Solvent Foam Performance

“…Oil recovery by foam has been attributed to the emulsification and imbibition of oil into foam lamellae (14,45) . A very slow approach to steady state and continued slow oil production have previously been observed with nitrogen-and CO 2 -foams that exhibit some sensitivity to oil (16,17,46,47) . When the methane fractional flow was lowered to 72%, the pressure drop increased more steeply, correlating directly with an increased rate of oil production [ Figure 6(b)].…”

Transient behavior of simultaneous flow of gas and surfactant solution in consolidated porous media

“…The overwhehning majority of d,_tt_ available in the literature confirms that much less gas mobility reduction is obtained in the presence of oil tll,m in it;s td)sence [5,6,18,25,44,60,78,86], In corefloods, foam propagation is reL,_rded in the presence ,,f oil, Being l;he non-wel;ting phase in sands, oil occupies the l_rge pores t_hus blocking a few of tile foa, rn generatiion sities ld/li, Therefore, fo_ma does not propaga, t,e until some of the ,,ii is disl)l_uzed, The desl;_billz,ation of fomn by oil in a porous medium is due to oil penetr_tion of the gas/liquid interfa,ce followed by lamellae rupture [106]. Result, s of Lau _md O'I3rien [76] show tl_at; flu' presence of a spre_cling oil slows down foam generation and decreases foam propagation rat;e, Mmllowe and l:{,a,dl<e [81] indicated that foam sta,bility in porous media is'dependent ttpoll l,he stability of pseudoemulsiozl films (liquid films between oil and g_s).…”

“…• The presence of oil has a destabilizing effect on foam with mos foaming surfactants q [5,6,18,25,44,60,67,78,81,86,106]. …”

Experimental investigation and modelling of CO2‐foam flow in heavy oil systems

“…The presence of oil is of primary importance since its effect on lamellae stability depends on the extent to which the foam lamellae interact with the oil . Since foam generation and propagation in porous media is strongly oil‐specific, oil‐insensitive foams have been shown to propagate faster than oil‐sensitive foams . Earlier studies showed that alkenes with a shorter carbon chain tended to be more detrimental to foam stability, which was determined by performing a series of bulk experiments .…”

“…[16] Since foam generation and propagation in porous media is strongly MONTH 2019 THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING 1 oil-specific, oil-insensitive foams have been shown to propagate faster than oil-sensitive foams. [17][18][19] Earlier studies showed that alkenes with a shorter carbon chain tended to be more detrimental to foam stability, which was determined by performing a series of bulk experiments. [8] One group of researchers stated that there is a specific critical oil saturation above which foam does not form, while others argued that high-quality foam can still be generated at relatively high residual oil saturation.…”