Carbon dioxide injection has recently been considered as a promising method for enhanced oil recovery. The supercritical carbon dioxide is often miscible or nearly miscible with the oil under reservoir conditions, which facilitates high recovery. Underground injection of carbon dioxide is also of a significant ecological advantage, and utilization of CO2 results in a noticeable reduction of the taxation of the petroleum companies. On the other hand, application of carbon dioxide under conditions of the North Sea petroleum reservoirs for enhanced oil recovery (EOR) is hindered by multiple practical problems: availability of the CO2 sources, logistics of the delivery offshore, corrosion resistivity of the installations, and other. Previous studies of CO2 EOR for the reservoirs of the North Sea region, including core-flooding experiments and reservoir simulations, indicate that the deployment of CO2-EOR can significantly enhance the recovery of hydrocarbons. However, CO2 must be generated from anthropogenic sources, which affects the feasibility of the projects.
The current study evaluates the potential of a CO2-EOR project under the conditions of a specific petroleum reservoir of the Danish sector North Sea. Geological characteristics of the reservoir and the detailed oil properties lie in the ground of the study. The minimum miscibility pressures between CO2 and the reservoir oil are evaluated with the help of the in-house software (SPECS 5.70) and the commercial reservoir simulator (ECLIPSE 300). The results are verified in the slimtube simulations. The effect of the different oil characterizations and its lumping into the different numbers of components is investigated. The oil is found to be miscible with the carbon dioxide under reservoir conditions.
Several injection scenarios have been tested on the 2-D and 3-D reservoir models. Waterflooding was compared to injection of carbon dioxide, as well as water-alternate gas injection. An optimal scenario with regard to water-gas ratio under WAG was selected for further studies.
Finally, a cash flow model by Monte Carlo simulations and a sensitivity analysis on the impact of oil and CO2 price and discount rate, certify the feasibility and attractiveness of a CO2-EOR project in the West Flank of the Dan field.
Arshad, Muhammad Waseem (Technical University of Denmark) | Feilberg, Karen Louise (Technical University of Denmark) | Shapiro, Alexander (Technical University of Denmark) | Thomsen, Kaj (Technical University of Denmark)
Characterization of emulsion formation (amount and droplet size) in the brine-oil-nanoparticle systems as a function of varying size of nanoparticles and modified brine salinity is presented. Different brines were used with a range from zero salinity for deionized water (DIW) to synthetic seawater (SSW), mimicking the salinity of North Sea water. Brines (FW1 and FW2) representing the composition of formation water obtained from different production wells (North Sea) were also used. Two model oils (decane (D) and hexane-hexadecane (HH) mixture of 1:1 vol. ratio) and a sample of North Sea crude oil (NSCO) were used. CaCO3 nanoparticles of three different sizes of 15-40, 50, and 90 nm were used. Nanoparticles characterization was performed with Transmission Electron Microscopy (TEM). A commercially available sonication equipment, Branson Sonifier® SFX250, was employed for emulsion formation in brine-oil-nanoparticles systems. All the experiments were performed at room temperature for the same experimental conditions of 5 minutes of ultrasonic processing by using a 6.5 mm tapered microtip (sonication probe) with an output power of 30 W. Emulsion characterization (emulsion droplet size) was performed with an optical microscope (Axio Scope.A1).
The effect of size of CaCO3 nanoparticles and brine salinity on emulsion formation was investigated for different brine-oil systems. The results showed that the emulsion formation in brine-model oil (D and HH) systems was an inverse function of the size of nanoparticles i.e., a large amount of emulsion formation was observed for the smaller sized nanoparticles and vice versa. Emulsion characterization for these systems showed that the emulsion droplet size increased with an increase in size of the nanoparticles. The brine salinity also showed a significant effect on emulsion formation in brine-model oil systems i.e., a decrease in brine salinity showed an increase in emulsion formation and correspondingly smaller emulsion droplet sizes. However, the brine salinity did not affect the emulsion formation and emulsion droplet size for 15-40 nm nanoparticles. Contrary to the brine-model oil results, the results of brine-NSCO systems neither showed any dependence on the size of nanoparticles nor on the brine salinity. This might be due to the presence of polar fractions (polar acids and polar bases) in the crude oil.
The characterization study presented in this paper can provide a foundation for future development of calcite nanoparticle based EOR applications in the carbonate reservoirs.
Arshad, Muhammad Waseem (Technical University of Denmark DTU, DTU Chemical Engineering, Center for Energy Resources Engineering, Søltofts Plads 229, DK-2800 Kongens Lyngby) | Loldrup Fosbøl, Philip (Technical University of Denmark DTU, DTU Chemical Engineering, Center for Energy Resources Engineering, Søltofts Plads 229, DK-2800 Kongens Lyngby) | Shapiro, Alexander (Technical University of Denmark DTU, DTU Chemical Engineering, Center for Energy Resources Engineering, Søltofts Plads 229, DK-2800 Kongens Lyngby) | Thomsen, Kaj (Technical University of Denmark DTU, DTU Chemical Engineering, Center for Energy Resources Engineering, Søltofts Plads 229, DK-2800 Kongens Lyngby)
Smart water flooding is an advanced method for enhanced oil recovery (EOR) in which the composition of injected brine is altered by varying the concentration of selected ions that can increase the oil recovery from various carbonate reservoirs. Besides wettability alteration mechanism, the formation of water-soluble oil emulsions has been reported as a possible reason to explain the observed increase in oil recovery using smart water. The formation of water-soluble oil emulsions takes place on the interaction of insoluble salts (fines) with oils. However, the interaction of these fines with the crude oil is not very well studied for carbonate reservoirs. This work presents emulsion formation in water-oil systems in the presence of water-insoluble fines. The effect of amount of fines on emulsion formation is also examined.
Synthetic seawater (SSW) and deionized water (DIW) were used as water phase, two model oils (decane (D) and 1:1 vol. ratio of hexane-hexadecane (HH) mixture) and North Sea crude oil (NSCO) were used as oil phase, and fines of CaCO3 (≤ 30 µm) and CaSO4 (≈ 44 µm) were used as solid phase. Branson Sonifier® SFX250 was used for emulsion formation (based on the principle of ultrasonic processing). All the experiments were performed for the same conditions of 5 minutes of ultrasonic processing at an output power of 30 W by using 6.5 mm tapered microtip (sonication probe). Emulsion characterization was done by using an optical microscope (Axio Scaope.A1).
Several combinations of water-oil-fines were tested. The tests consisted of control experiments (in which only water-oil without any fines were tested) and water-oil-fines experiments. In the control experiments (without fines), SSW did not show any tendency to emulsify neither with the model oils nor with NSCO. However, DIW showed clear tendency to emulsify with model oils and NSCO. Amongst model oils, DIW emulsified with HH better compared to decane. Similar results were observed in the water-oil-fines experiments. SSW did not form any emulsion with the model oils in the presence of fines of CaCO3 and CaSO4. However, significant amounts of emulsion formation were observed when DIW was sonicated with model oils and fines. HH formed more emulsions compared to decane. For NSCO case, both SSW and DIW formed a significant amount of emulsions with both types of fines (CaCO3 and CaSO4). An increase in amount of fines showed an increase in emulsion formation and a better emulsion stabilization. Sonication is a quick and reliable technique to screen out emulsion formation in different combinations of water-oil-fines.
This work will further develop our understanding of emulsion formation in the water-oil-fines systems.