SUMMARYAlkaline-Surfactant-Foam (ASF) flooding is a recently introduced enhanced oil recovery (EOR) method. This paper presents laboratory study of this ASF to better understand its mechanisms. The focus is on the interaction of ASF chemical agents with oil and in the presence and absence of naphthenic component and in-situ soap generation. The impact of alkali, IFT reduction, in-situ soap generation and oil acid number were systematically studied by measurement of phase behaviour, interfacial tension and foam stability. Phase behaviour results indicate the synergistic effect between the generated soap and synthetic surfactant, which gives wider range of optimal salinity in terms of IFT reduction. The novel alkali-surfactant formulation lowered IFT between oil and aqueous phase from nearly 30 mN/m to 10-1 -10-3 mN/m. This means that chemical formulation can create low tension foam flooding with higher capillary number than conventional foam for displacing oil from porous media. In the foam stability analysis of ASF agent in the presence and absence of oil, several characteristics such as foam volume evolution, foam half decay time, liquid fraction of foam were measured over a wide range of surfactant, alkali, electrolyte and naphthenic acid concentration. Bulk foam stability tests demonstrated that stability of foam diminishes in presence of oil with high in-situ soap generation. The obtained results for foam stability in the presence of oil were successfully interpreted in terms of phenomenological theory of entering/spreading/bridging coefficient, lamella number and pseudo-emulsion film. The discussed method in this paper can be successfully applied to formulate high performance chemical agents for achievement of improved foam flooding according to reservoir fluid condition, i.e. properties of crude oil and formation water.
SUMMARYThe Steamflooding was considered in this research to extract the discontinuous bitumen layers that are located at the oil-water contact for the heterogeneous light oil sandstone reservoir of South Rumaila Field. The reservoir heterogeneity and the bitumen layers impede water aquifer approaching into the reservoir; therefore, Steamflooding would be efficient to extract bitumen layers and improve oil recovery. This research focused on adopting three Design of Experiments (DoE) approaches with thermodynamic reservoir flow simulation to identify the most influential factors that impact the reservoir performance through Steamflooding process. Meanwhile, the thermodynamic simulation was used to evaluate the various what-if scenarios and compute cumulative oil production that was considered as a response in the experimental design procedure. In this paper, full factorial design (FFD) and orthogonal arrays design (OAD) were adopted along with Hammersley Sequence Sampling (HSS) for that purpose. HSS is a low discrepancy and uniform space filling decimal points sampling that provide multiple levels for each factor. The factors are steam injection pressure, steam quality, steam injection rate, steam temperature, and number of injectors. To validate the overall design and each factor, analysis of variance (ANOVA) test was used to assess the influential role for each factor. In comparison with no-injection base case, Steamflooding has proved its feasibility to extract bitumen and improve recovery factor that reached to 80.018% by the end of 12 years prediction period; nevertheless, oil recovery for the base case was only 68.231 %, which is equal to the value with Steamflooding only after 11 months when the Steam injection starts. The linear DoE model of HSS has shown its validity to handle wide variety experiments of the problem. The main influential factors that were identified by DoE models are steam quality, steam injection rate and some of the interaction terms that include other factors.
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