S. Vincent-Bonnieu

Role of Gas Type on Foam Transport in Porous Media

We present the results of an experimental investigation of the effect of gas type and composition on foam transport in porous media. Steady-state foam strengths with respect to three cases of distinct gases and two cases containing binary mixtures of these gases were compared. The effects of gas solubility, the stability of lamellae, and the gas diffusion rate across the lamellae were examined. Our experimental results showed that the steady-state foam strength is inversely correlated with the gas permeability across a liquid lamella, a parameter that characterizes the rate of mass transport. The results are also in good agreement with existing observations that the foam strength for a mixture of gases is correlated with the less soluble component. Three hypotheses with different predictions of the underlying mechanism that explain the role of gas type and composition in foam strength are discussed in detail.

Small core flood experiments for foam EOR: screening surfactant applications

Aqueous foams are a means of increasing the sweep efficiency of enhanced oil recovery processes. An understanding of how a foam behaves in the presence of oil is therefore of great importance when selecting suitable surfactants for EOR processes. The consensus is currently that the most reliable method for determining the foam behavior in the presence of oil is to inject foam through a rock core. Coreflood tests, however, are typically carried out using large rock cores (e.g. diameter = 4 cm, length = 40 cm or longer), and hence foam flow tests can take days or weeks to achieve steady-state flow. In this study, we present the preliminary results for a core-flood system where the rock core is pen-sized (diameter = 1 cm, length = 17 cm). These small cores allow for short-duration foam flow tests, where steady-state flow is achieved in a few hours. Using this system, the foam quality/effective viscosity response curves can be plotted, both with and without oil in the system. These small size cores then enable rapid screening of surfactants and foam properties in different rocks and with different oils. Benefits and limitations of these small coreflood experiments are discussed.

Effect of Permeability on Foam-model parameters - An Integrated Approach from Coreflood Experiments through to Foam Diversion Calculations

Foam reservoir simulations commonly suffer from poor foam parameter definition which makes their predictions ambiguous. To reduce uncertainty in foam parameter estimation, extensive core-flood experiments under variable experimental and physical conditions are required. A principal physical property which can influence foam parameters is permeability. We present a set of steady-state foam-flood experimental data for four sandstones with different permeabilities, ranging between 6 and 1900 mD, and with similar porosity. We derive permeability-dependent foam parameters with two modelling approaches, those of Boeije and Rossen (2013) and a non-linear least-square minimization approach (Eftekhari et al., 2015). The two approaches can yield significantly different foam parameters. Thus we critically assess their ability in deriving reliable foam parameter estimates. In particular, the way the two approaches treat shear-thinning foam behavior and foam coalescence is discussed. The foam parameter set acquired from the latter approach is further used as input in foam diversion calculations: this serves to evaluate mobility predictions in non-communicating reservoir layers to the foam parameters. This study aims to provide a framework to integrate experimental work, modelling and simple qualitative diversion calculations to provide a background for the upscaling of foam studies, with particular focus to heterogeneous systems.

Experimental Study of Hysteresis behavior of Foam Generation in Porous Media

Foam can be used for gas mobility control in different subsurface applications. The success of foam-injection process depends on foam-generation and propagation rate inside the porous medium. In some cases, foam properties depend on the history of the flow or concentration of the surfactant, i.e., the hysteresis effect. Foam may show hysteresis behavior by exhibiting multiple states at the same injection conditions, where coarse-textured foam is converted into strong foam with fine texture at a critical injection velocity or pressure gradient. This study aims to investigate the effects of injection velocity and surfactant concentration on foam generation and hysteresis behavior as a function of foam quality. We find that the transition from coarse-foam to strong-foam (i.e., the minimum pressure gradient for foam generation) is almost independent of flowrate, surfactant concentration, and foam quality. Moreover, the hysteresis behavior in foam generation occurs only at high-quality regimes and when the pressure gradient is below a certain value regardless of the total flow rate and surfactant concentration. We also observe that the rheological behavior of foam is strongly dependent on liquid velocity.

Fall-off test analysis and transient pressure behavior in foam flooding

Gas injection projects often suffer from poor volumetric sweep because under reservoir conditions the density and viscosity differences between the gas and the in-situ oil leads to override and bypassing of much of the oil in place. Foam has been suggested as a potential solution to this shortcoming and has shown success in some of the field applications. In the field scale foam can reduce the gas mobility, fight against gravity by inducing excess viscous forces and reduce the gas-oil ratio in the producer. Nevertheless, foam propagation in the reservoir, with low fluid velocities, and survival of foam in the path from injector to producer are among major uncertainties in foam projects. This necessitates the design of surveillance plans to monitor foam rheology and its propagation in porous media. Usually foam generation inside a porous medium is indirectly inferred from the pressure response; once foam is generated in the reservoir the pressure increases. Foam frequently exhibits non-Newtonian (shearthinning) behaviour, as it is propagated through the porous medium, which can influence the pressure transient test behaviour. This paper studies different well testing interpretation and pressure behaviour of foam flow in a homogenous reservoir. Local-equilibrium or implicit-texture foam model (that of STARS) are used to model the foam behaviour in porous media. Pressure fall-off test behaviour presented in this paper is new for foam injection. The flow regimes including inclined radial flow, radial flow, transient section, and reservoir boundary are discussed. A method which uses a pressure and a pressure derivative plot is developed for foam injection so that the mobility changes, flow behaviour index, location of foam front, reservoir parameters and reservoir boundary can be estimated. The results of this study can be used to analyse data from injection well, where monitoring of the generation, stability and distribution of foam is a key factor in the success of a foam field project. This paper discuss the dependency of the results on foam-model parameters, which indicates that by using pressure transient data one can obtain the foam model parameter.