Injection Strategies for Foam Generation in Homogeneous and Layered Porous Media

Abstract

Foam generation plays a crucial role in the use of foam for improved oil recovery, acid diversion and environmental remediation.This sandpack study extends previous work to layered media, the effect of surfactant concentration, and injection strategy, including alternating-slug (SAG) injection and pulsed injection rate and pressure.As in earlier studies, three foam states were observed: high-mobility coarse foam at low pressure gradient, low-mobility strong foam at high pressure gradient, and, in between, an intermediate state with nearly complete gas plugging. With co-injection of gas and liquid in homogeneous sandpacks, foam generation occurred at lower pressure gradient and lower gas velocity at higher liquid injection rates, higher permeability, and higher surfactant concentration. Within the plugged state, the pressure gradients required for foam propagation were remarkably high (of order 10 psi/ft) given the high permeability of the packs. In flow from lower- to higher-permeability layers, foam generation occurred at lower pressure gradient than expected in either medium by itself. However, a minimum threshold pressure gradient for foam generation was still observed when the permeability contrast was of order 5:1, contradicting theory for foam generation at a sharp permeability transition. Foam generation was observed at all pressure gradients when the permeability contrast was 20:1. With co-injection of gas and liquid into layered packs, the low-mobility zone near the transition in permeability spread downstream if pressure gradient was sufficient. During gas injection in SAG processes, a low-mobility front traveled the length of homogeneous packs and then exited. In heterogeneous packs, SAG injection gave persistent low mobility near the transition in permeability. Gas mobility in SAG processes was from 10 to 100 times higher than with co-injection of gas and liquid. Briefly raising injection pressure in steady co-injection helped trigger foam generation in layered media, but had no lasting effect in homogeneous packs. Foam was not uniform within packs, especially in the plugged state. Therefore, properties averaged over the pack do not represent a homogeneous state. Care is needed in using such data to fit mechanistic models for foam behavior. Introduction Foam can improve conformance in gas-injection improved oil recovery (Schramm, 1994; Rossen, 1996), acidizing (Smith et al., 1969; Gdanski, 1993) and environmental remediation (Hirasaki et al., 2000; Mamun et al, 2002). For all applications, foam generation is crucial to applying foam. Foam generation, however, is a complicated function of gas and water superficial velocities, pore geometry, the presence of oil, surfactant concentration, surfactant formulation, and other factors.

Modeling Techniques for Foam Flow in Porous Media

“…It was also found that a secondary desaturation front propagated in the direction opposite the foam propagation during coinjection processes (Simjoo et al 2013), which was similar to the observations in other studies (Apaydin and Kovscek 2001;Nguyen et al 2003). Some coinjection experiments require several-pore-volume injections of gas and surfactant solution to achieve a steady pressure drop across the core even after excluding the possibility of satisfying surfactant adsorption and gas compressibility (Li et al 2010;Ma et al 2013;Simjoo et al 2013), which is also not predicted by local-equilibrium foam models. Rossen and Boeije (2013) pointed out that laboratory SAG coreflooding could be unreliable to be used for parameter fitting of local-equilibrium models because of failure to reach local steady state, increased effect of dispersion, and the capillary end effect.…”

“…As a mobility-control agent, foam has the potential for applications in industrial processes that involve fluid injection into porous formation, such as enhanced oil recovery (EOR) (Patzek and Koinis 1990;Patzek 1996;Farajzadeh et al 2009Farajzadeh et al , 2012Li et al 2010;Ren et al 2013;Chen et al 2014), matrix-acidization treatments (Gdanski 1993;Rossen and Wang 1999;), gas-leakage prevention (Bernard and Holm 1970;Smith and Jikich 1993), and contaminated-aquifer remediation (Hirasaki et al 1997;Mulligan 2009). The success of these applications relies heavily on the understanding of the physics of foam flow through porous media.…”

“…Foam coalesces in situ through capillary suction and gas diffusion (or bubble Oswald ripening), of which capillary suction is the governing mechanism because of the converging/diverging geometry in porous media (Khatib et al 1988;Jiménez and Radke 1989). The presence of oil also has a major impact on foam coalescence and mobility control in porous media (Nikolov et al 1986;Jensen and Friedmann 1987;Lau and O'Brien 1988;Hanssen and Dalland 1990; Manlowe and Radke 1990;Svorstol et al 1996;Li et al 2010). The details of foam/oil interactions are reviewed in the work by Farajzadeh et al (2012).…”

Upscaling of Foam Mobility Control to Three Dimensions

“…So these two mechanisms are considered to be able to generate strong foam. Pressure gradient [11][12][13][14] is important in strong foam generation process. Higher p ∇ can mobilize more stationary lamellae, set off the lamellae division process and generate more new lamellae which will block more of the gas flow paths.…”

Understanding aqueous foam with novel CO2-soluble surfactants for controlling CO2 vertical sweep in sandstone reservoirs

“…At the same time, we also notice that relative to simultaneous injection (Fig. 6), the alternating injection does promote the foam generation and injectivity (Li and Rossen 2005) for both types of foams indicated by the quick strong foam propagation and lower pressure drops.…”