Prediction of CO2 Solubility in Oil and the Effects on the Oil Physical Properties

Abstract

CO₂ solubility in oil is a key parameter in CO₂ flooding process. It results in oil swelling, increased oil density, and decreased oil viscosity. Laboratory studies needed to cover a wider range of data, and are time consuming, costly, and may be not available or possible in many situations. On the other hand, although various models and correlations are useful in certain situations, they may are not be applicable in many situations.

In this study, a new genetic algorithm- (GA)-based technique has been used to develop more reliable correlations to predict CO₂ solubility, oil swelling factor (SF), CO₂-oil density, and viscosity of CO₂-oil mixtures. Based on the Darwinian theory, the GA technique mimics some of the natural process mechanisms. Furthermore, GA-based model correlations recognize all the major parameters that affect each physical property and also well address the effects of CO₂ liquefaction pressure.

Genetic algorithm-based correlations have been successfully validated with published experimental data. In addition, a comparison of these correlations has been made against widely used correlations in the literature. It has been noted that the GA-based correlations yield more accurate predictions with lower errors than all other correlations tested. Furthermore, unlike other correlations that are applicable to limited data ranges and conditions, GA-based correlations have been validated over a wider range of data.     

Effects of aqueous solubility and molecular diffusion on CO2-enhanced hydrocarbon recovery and storage from liquid-rich shale reservoirs

This study investigates the effects of aqueous solubility and aqueous molecular diffusion of gaseous components (CO₂ and CH₄) on the CO₂ huff and puff process in the liquid-rich shale reservoirs. In a gas-condensate reservoir, the effects negligibly enhance the hydrocarbon production, but increase the CO₂ storage with 4.4% by solubility trapping. In a shale oil reservoir, they increase the production and CO₂ storage up to 5% and 14% by more CO₂ imbibition and contacting between CO₂ and oil. This study clarifies the importance of aqueous solubility and aqueous-phase molecular diffusion of CO₂ huff and puff in shale reservoirs.     

Evaluation and optimization of hybrid polymer-assisted carbonated waterflood to enhance oil recovery and CO2 storage

Hybrid polymer-assisted carbonated waterflood (PCWF) introduces synergetic effects due to multiple mechanisms (polymer rheology, geochemical reactions, and interphase transport of CO₂ in crude oil/brine/mineral). This study simulates the hybrid process and investigates its performance in comparison to waterflood, polymer flood, and CWF. In addition, the robust optimization and Pareto optimality study maximize the net present value (NPV) and CO₂ storage of PCWF. The optimum designs of PCWF increase NPV with 30% over waterflood and secure CO₂ storage effect. This comprehensive study demonstrates the hybrid enhanced oil recovery/CO₂ storage of the PCWF.     

Optimizing a CO2 value chain for the Norwegian Continental Shelf

This paper presents a mathematical model for designing a carbon dioxide (CO₂) value chain. Storage of CO₂ in geological formations is recognized as an important alternative for carbon abatement. When CO₂ is deposited in oil reservoirs it can sometimes be used to achieve additional oil production, enhanced oil recovery (EOR). The model determines an optimal CO₂ value chain from a fixed set of CO₂ emission points and a set of potential injection sites. It designs a transport network and chooses the best suited oil fields with EOR potential or other geological formations for storage. A net present value criterion is used. The model is illustrated by an example of a Norwegian case with 14 oil fields, two aquifers and five CO₂ sources. A sensitivity analysis is performed on the most important parameters.     

Comparison of supercritical CO2, liquid CO2, and solvent extraction of chemicals from a commercial slow pyrolysis liquid of beech wood

Innovative extraction methods with supercritical CO₂ and liquid CO₂ have been employed to obtain value-added chemicals from a slow pyrolysis liquid. Sequential solvent extraction with hexane and acetone was carried out for comparison. Pyrolysis liquid was first adsorbed on silica (SiO₂) with weight ratios SiO₂:oil of 100:40 and 100:80. Pyrolysis liquid and extracts were mainly characterized by GC–MS/FID, elemental analysis, and water content. Results show that scCO₂ extraction is mainly controlled by dissolution at the first 3 h during a 6-h extraction period and by combination of dissolution and diffusion at later extraction periods. Around 60–65% of the CO₂ and hexane extracts could be identified by GC compared to 49% of the starting pyrolysis liquid. GC data confirmed that, CO₂ extraction effectively enriched both non-aromatics and aromatic compounds. Hexane extracts contained lower contents of organic acids. Hexane enabled a complete extraction of aromatics. Chemical composition of extracts from scCO₂ and liquid CO₂ are very similar. Extraction with scCO₂ and liquid CO₂ proves to be an effective and innovative pre-treatment process for the production of chemicals from pyrolysis liquid.     

Immiscible CO2 Flooding through Horizontal Wells

Abstract

The CO₂ immiscible process is a potentially viable method of enhanced oil recovery (EOR) for heavy oil reservoirs. In an immiscible CO₂ process, part of the injected CO₂ is absorbed into the reservoir fluids and part forms a free-gas phase in the reservoir. Three groups of well configurations were mainly used: (1) vertical injection and vertical production wells, (2) vertical injection and horizontal production wells, and (3) horizontal injection and horizontal production wells. In immiscible CO₂ injection, highest recovery was obtained by vertical injection-horizontal production (VI-HP), followed by vertical injection-vertical production (VI-VP), and the least by horizontal injection-horizontal production (HI-HP). In VI-HP well configuration, the best recovery was obtained as 15.1% OOIP. In continuous CO₂ injection experiments, oil recovery for the VI-HP well configuration was higher than that of the other well configurations. The lowest ultimate recovery was obtained from HI-HP well configuration. The distance between the horizontal injector and horizontal producer was another important factor for the displacement of oil. In all runs, CO₂ breakthrough occurred very early, showing the dominance of viscous forces and relatively small effect of mass transfer between CO₂ and oil. The total oil recovery varied considerably because of the differences in injection rates and because of the unstable displacement. As a whole, oil recovery increased with an increase in the injection rate of CO₂. The cumulative gas-oil ratio (GOR) appeared to be sensitive to the gas injection rate for all well configurations. An increase in oil recovery with injection rate during initial stages of the runs was affected by the cumulative GOR.     

Assessment of CO2 emissions and its reduction potential in the Korean petroleum refining industry using energy-environment models

We assessed potential future CO₂ reduction in the Korean petroleum refining industry by investigating five new technologies for energy savings and CO₂ mitigation using a hybrid SD-LEAP model: crude oil distillation units (CDU), vacuum distillation units (VDU), light gas-oil hydro-desulfurization units (LGO HDS), and the vacuum residue hydro-desulfurization (VR HDS) process. The current and future demand for refining industry products in Korea was estimated using the SD model. The required crude oil input amounts are expected to increase from 139 million tons in 2008 to 154 million tons in 2030 in the baseline scenario. The current and future productivity of the petroleum refining industry was predicted, and this prediction was substituted into the LEAP model which analyzed energy consumption and CO₂ emissions from the refining processes in the BAU scenario. We expect that new technology and alternative scenarios will reduce CO₂ emissions by 0.048% and 0.065% in the national and industrial sectors, respectively.     

An Investigation of WAG Process Using Horizontal Wells

In this study, a comprehensive laboratory investigation was conducted for the recovery of heavy oil from a three-dimensional (3-D) physical model, packed with 18°API gravity crude oil, brine and crushed limestone. A total of 15 experiments were conducted using the 3-D physical model with 30 cm × 30 cm × 6 cm dimensions. Basically, water-alternating gas (WAG) process was used for recovering heavy oil. Three groups of well configurations were mainly used: (i) vertical injection and vertical production wells, (ii) vertical injection and horizontal production wells, and (iii) horizontal injection and horizontal production wells. Base experiments were run with water only and carbondioxide alone and optimum rates for WAG process were determined. In CO₂ injection experiments, vertical injection and horizontal production well configuration supplied a higher recovery (15.06% OOIP) than that of the others. Horizontal injection and horizontal production well configuration gave poor recovery with the same gas rate, while vertical injection and vertical production was better off with a lower gas rate. The volumetric ratio of the water and CO₂ slugs (WAG ratio) was varied 1:3 to 1:10 in order to determine optimum conditions. For water alternating gas injection case at a WAG ratio 1:7, vertical injection and vertical production well configuration gave the highest recovery (21.04% OOIP). Waterflooding reached the best recovery (37.20% OOIP) in vertical injection and vertical production well configuration. Oil production from WAG injection is higher than that obtained from the injection of continuous CO₂ or waterflooding alone.     

Comprehensive chemical kinetic modeling of the oxidation of 2-methylalkanes from C7 to C20

Conventional petroleum jet and diesel fuels, as well as alternative Fischer–Tropsch (FT) fuels and hydrotreated renewable jet (HRJ) fuels, contain high molecular weight lightly branched alkanes (i.e., methylalkanes) and straight chain alkanes (n-alkanes). Improving the combustion of these fuels in practical applications requires a fundamental understanding of large hydrocarbon combustion chemistry. This research project presents a detailed and reduced chemical kinetic mechanism for singly methylated iso-alkanes (i.e., 2-methylalkanes) ranging from C₇ to C₂₀. The mechanism also includes an updated version of our previously published C₈–C₁₆n-alkanes model. The complete detailed mechanism contains approximately 7200 species 31400 reactions. The proposed model is validated against new experimental data from a variety of fundamental combustion devices including premixed and non-premixed flames, perfectly stirred reactors and shock tubes. This new model is used to show how the presence of a methyl branch affects important combustion properties such as laminar flame propagation, ignition, and species formation.     

ANFIS modeling of CO2 separation from natural gas using hollow fiber polymeric membrane

The present study is proposed to develop the Adaptive Neuro-Fuzzy Inference System optimized by genetic algorithm to estimate CO₂ value in permeate stream using a hollow fiber polymeric membrane for separation of binary gas containing CO₂ and CH₄ in natural gas. To that end, a number of 65 samples was gathered from the literature. Results indicated that the proposed ANFIS model has great potential with high correlation (R² = 0.9993) and less error (RMSE = 0.0064) for estimation of aforementioned parameter.     

The effect of capillary-trapped CO2 on oil recovery and CO2 sequestration during the WAG process

This study investigated capillary-trapped CO₂ depending on the consideration of hysteresis effect in relative permeability for various water-alternation-gas (WAG) operating conditions to ascertain the oil production process. From the simulation results of CO₂ WAG flooding method, the trapped CO₂ led to prevent water-flow, in which CO₂ acts as a gas blocker near the well. It caused the injection pressure increase during water injection period. As the trapped CO₂ in pores increased, the reservoir pressure was also increased and maintained above minimum miscibility pressure (MMP). Ultimately, it was concluded that the reservoir was kept under miscible conditions throughout WAG process, reducing residual oil and increasing oil recovery.     

Prediction of mineral scale formation in geothermal and oilfield operations using the Extended UNIQUAC model: Part II. Carbonate-scaling minerals

Two parameters have been added to the Extended UNIQUAC model of Thomsen and Rasmussen [Thomsen, K., Rasmussen, P., 1999. Modeling of vapor–liquid–solid equilibrium in gas-aqueous electrolyte systems. Chem. Eng. Sci. 54, 1787–1802] to account for the pressure dependency of mineral solubility. The improved model has been used for correlating and predicting vapor–liquid–solid equilibrium for different carbonate systems (CaCO₃, MgCO₃, BaCO₃ and SrCO₃) causing mineral scaling problems. The solubility of NaCl and CO₂ in pure water and the solubility of CO₂ in NaCl and Na₂SO₄ solutions have also been correlated. The results show that the Extended UNIQUAC model, with the added pressure parameters, is able to represent binary (NaCl–H₂O, CaCO₃–H₂O, BaCO₃–H₂O, SrCO₃–H₂O, MgCO₃–H₂O, Mg(OH)₂–H₂O and CO₂–H₂O), ternary (CaCO₃–CO₂–H₂O, BaCO₃–CO₂–H₂O, SrCO₃–CO₂–H₂O, MgCO₃–CO₂–H₂O, CO₂–NaCl–H₂O and CO₂–Na₂SO₄–H₂O), and quaternary (CO₂–NaCl–Na₂SO₄–H₂O) solubility data within the experimental accuracy in the range of temperatures and pressures considered in the study, i.e. from 0 to 250 °C, and from 1 to 1000 bar, respectively.The modified Extended UNIQUAC model will be a useful tool for predicting and quantifying the scaling problems that may occur in wells and surface equipment during geothermal operations. This would allow adequate preventive measures to be taken before mineral deposition becomes troublesome.     

Artificial intelligence techniques for the vibration,noise, and emission characteristics of a hydrogen-enriched diesel engine

The present paper investigates the prediction of vibration, noise level, and emission characteristics of a four-stroke, four-cylinder diesel engine fueled with sunflower, canola, and corn biodiesel blends while H₂ injected through inlet manifold using two different artificial intelligence methods: artificial neural network (ANN) and support vector machines (SVM). The aim of using these methods is to predict vibration, noise, carbon monoxide (CO), CO₂, and NO_x based on the initial experimental study by varying engine speed, blends of biodiesel, and H₂ energy substitution ratio. Experimental data were gathered from the literature. For the ANN method, LevenbergMarquardt backpropagation training algorithm with logarithmic sigmoid and linear transfer function for hidden and output layers, respectively, gives the best results for prediction of vibration, noise, and emission characteristics. For SVM, a regression model is implemented with Gaussian kernel function. Results show that the ANN performs better than SVM, and the best mean average percent error and R² for the models developed are 2.03 and 0.988 for vibration acceleration, 0.39 and 0.9615 for noise, 7.27 and 0.8549 for CO, 5.09 and 0.9398 for NO_x, and 2.21 and 0.993 for CO₂ values, respectively. Eventually, it is found that the ANN method is a good choice for simulation and prediction of dual fueled hydrogen sunflower, canola, and corn biodiesel blends.     

A comparative study of electrodes in the direct synthesis of CH4 from CO2 and H2O in molten salts

Since the Industrial Revolution, the heavy reliance on the limited fossil energy has emitted huge number of CO₂ into the air and led to a severely global warming. We propose a new green technology to moderate greenhouse gas CO₂ emission and transform it into low-carbon renewable energy in this paper. Through this manner, electricity is transformed into chemical energy. CO₂ and H₂O is directly simultaneous electrolysis under constant 0.25 A with 30 cm² nickel anode and 30 cm² iron cathode in a 600 °C alkali carbonate with LiOH electrolyte in mole ratio of n_H:n_C = 0.15:1, achieving the storage of electricity to chemical energy. This electrolysis provides a gaseous product comprising 45.9% methane, 53.1% H₂, 0.92% CO and trace amounts of longer (than methane) hydrocarbons. Simultaneously, the current efficiency is still ～51% for 60 min.     

A novel anode for preventing liquid sealing effect in DMFC

Carbon dioxide removal from the catalyst sites is critical to ensure high power output operation of direct methanol fuel cell (DMFC). In this work, a novel anode which contains water-proof oil, dimethyl silicon oil (DMS) was prepared for preventing liquid sealing effect (LSE) to CO₂. The novel electrode displays outstanding preventing LSE capability than a conventional PtRu/C electrode. The success of the novel anode in preventing LSE is due to DMS, in which the solubility and diffusion coefficient of CO₂ are much higher than that in methanol–water solution, supplying an unoccupied channel for CO₂ transportation.     

Effects of relative permeability change resulting from interfacial tension reduction on vertical sweep efficiency during the CO2-LPG hybrid EOR process

The addition of liquefied petroleum gas (LPG) to the CO₂ stream reduces interfacial tension (IFT) between the injected gas and the reservoir oil, and it changes the gas-liquid relative permeability by making it more water-wet, which affects not only the oil mobility, but also the vertical sweep efficiency. The reduction of the IFT decreases vertical sweep efficiency because it enhances the relative permeability of the solvent, resulting in an increase in the viscous gravity number. For CO₂-LPG enhanced oil recovery (EOR), oil recovery is enhanced by up to 47%, as compared to CO₂ flooding, when the relative permeability change caused by the IFT is not considered. By taking the vertical sweep-out caused by IFT and relative permeability change into consideration, this increase is reduced to 40%. These results indicate the importance of considering the relative permeability and IFT change when predicting the performance of the CO₂-LPG EOR process.     

A supported solid base catalyst synthesized from green biomass ash for biodiesel production

This study aimed to evaluate camphor tree ash (green biomass ash) supported K₂CO₃ as a solid base catalyst for biodiesel production. The catalyst was prepared by way of first-calcination, K₂CO₃ solution impregnation, and second-calcination method. The catalytic performance of the catalyst for the preparation of biodiesel was investigated. Under the optimal conditions of K₂CO₃ loading of 50 wt%, first-calcination temperature of 800°C, second-calcination temperature of 500°C, catalyst concentration of 5 wt%, catalytic time of 210 min, methanol/oil molar ratio of 14:1, and catalytic temperature of 65°C, the biodiesel yield reached 92.27%.     

Evaluation of effective parameters on CO2 injection process in a gas condensate reservoir: A case study

One of the key problems in gas condensate reservoirs is condensate blockage phenomena or condensate banking that reduces the condensate recovery. This phenomenon occurs when by reservoir depletion the reservoir pressure declines below the dew point pressure. One of the most important and common methods to prevent condensate blockage is gas cycling. Nowadays, regarding the value of natural gas, the use of other gases such as CO₂ as a suitable replacement has increased. The purpose of this study is to evaluate different parameters such as injection rate, injection pressure, and the number of wells in CO₂ injection process, in order to determine optimum conditions for CO₂ injection with the maximum condensate recovery and minimum economic cost. The two-parameter, Peng–Robinson equation of state (EOS) was used to match PVT experimental data. Then various scenarios of CO₂ injection with different conditions have been studied, and optimum conditions for CO₂ injection were compared with the natural depletion scenario. The results showed that the injection rate and pressure play important roles in determining the best condensate recovery.     

Environmental and economic assessment of the chemical absorption process in Korea using the LEAP model

CO₂ emission from fossil fuels is a major cause for the global warming effect, but it is hard to remove completely in actuality. Moreover, energy consumption is bound to increase for the continuous economic development of a country that has an industrial formation requiring high-energy demand. Therefore, we need to consider not only a device for CO₂ mitigation but also its impact when a CO₂ mitigation device is applied. The device for CO₂ emission mitigation can be classified into three fields: energy consumption reduction, development of CO₂ removal and recovery technology, and development of alternative energy technology. Among these options, CO₂ removal and recovery technology has a merit that can be applied to a process in the near future. Therefore, research for CO₂ removal and recovery is actively progressing in Korea. In this study, environmental and economic assessment according to the energy policy change for climate change agreement and increase of CO₂ mitigation technology is accomplished, on the bases of operating data for the CO₂ chemical absorption pilot plant that is installed in the Seoul coal steam power plant. The Long-range Energy Alternatives Planning system (LEAP) was used to analyze the alternative scenario, and results were shown quantitatively.     

Gas hydrate formation process for pre-combustion capture of carbon dioxide

In this study, gas hydrate from CO₂/H₂ gas mixtures with the addition of tetrahydrofuran (THF) was formed in a semi-batch stirred vessel at various pressures and temperatures to investigate the CO₂ separation/recovery properties. This mixture is of interest to CO₂ separation and recovery from Integrated Gasification Combine Cycle (IGCC) power plants. During hydrate formation the gas uptake was determined and composition changes in the gas phase were obtained by gas chromatography. The impact of THF on hydrate formation from the CO₂/H₂ was observed. The addition of THF significantly reduced the equilibrium formation conditions. 1.0 mol% THF was found to be the optimum concentration for CO₂ capture based on kinetic experiments. The present study illustrates the concept and provides thermodynamic and kinetic data for the separation/recovery of CO₂ (pre-combustion capture) from a fuel gas (CO₂/H₂) mixture.