Rasoul Khaledialidusti

Sample Mechanistic Modeling of Alkaline Surfactant Polymer Flooding for Snorre Field from Core-scale to Larger Scale of One-Spot Pilot

A considerable amount of oil resides in the Snorre reservoir in the North Sea. The impact of low-salinity-water flooding was investigated from core-scale using coreflood tests to larger scale of one-spot pilot using Single-Well-Chemical-Tracer (SWCT) tests before. Since the results showed a negligible amount of oil recovery, the alkaline/surfactant/polymer (ASP) flooding has been selected after the evaluation of the feasibility of all possible chemical enhanced oil recovery (EOR) methods based on the reservoir conditions. The potential of ASP has been evaluated through mechanistic modeling from core scale to large scale of one-spot pilot using SWCT test. First, the mechanistic modeling of ASP coreflood has been performed to make sure about the proper propagation of alkali, in-situ surfactant (soap), and surfactant. Second, the ASP injection has been also evaluated at larger scale of one-spot pilot using SWCT method. Mechanistic modeling of ASP flooding is highly sophisticated because of the complicated ASP phase behavior and the reactions that affect the process. Almost all effective reactions have been taken into account. Although low-salinitywater flooding as a standalone method could not improve oil recovery, the effect of low-salinity-water on the ASP efficiency has been studied to design and optimize the ASP method. Keywords— ASP flooding, Single-Well-ChemicalTracer (SWCT) method, low-salinity-water flooding, oil saturation.

Evaluation of surfactant flooding using interwell tracer analysis

Surfactant flooding is an important enhanced oil recovery (EOR) method, especially in carbonate oil reservoirs where water flooding may not have an effect on oil recovery as much as for sandstone reservoirs. This is because of the initial wettability of most carbonate reservoirs that is mixed- or oil-wet. Since surfactant flooding has a great impact on both fluid–fluid and rock–fluid interactions, it can be an efficient EOR method for these kinds of reservoirs. Surfactants affect fluid–fluid interactions by reducing interfacial tension (IFT) between water and oil phases and rock–fluid interactions by wettability alteration. The objective of this paper is the evaluation of these two surfactant mechanisms in non-fractured carbonate reservoirs using UTCHEM, the University of Texas chemical compositional simulator. In this paper, first, the laboratory data of two surfactant spontaneous imbibition tests for carbonate cores are successfully matched with modeled data to evaluate the mechanisms of surfactant flooding. Second, the field-scale surfactant flooding is simulated using the experimental data from spontaneous imbibition tests. Several cases are modeled in order to study the effect of surfactant flooding in terms of decreasing IFT and wettability alteration. Since the formation brine salinity in most reservoirs is more than the optimum salinity of surfactant phase behavior, the benefit of combining surfactant and low-salinity water is also investigated. Finally, tracer test simulation is performed to estimate the average oil saturation within the swept pore volume at the end of each recovery mode.