Oil Carbon Dioxide Research Articles

Research and Practice of Heavy Oil Hydraulic Pump Lifting Technology in Bohai Bay K Oilfield

In the early stage of heavy oil reservoir development in Bohai Bay K Oilfield, crude oil viscosity is high, conventional lifting processes have poor adaptability, and production energy consumption is high; Entering the stage of ultra-high water cut development, the company implemented carbon dioxide huff and puff, the difficulties in lifting matching brought about by the integrated wellbore requirements of injection and production, high gas-liquid ratio lifting, and enhanced corrosivity of the produced fluid. It conducted research on concentric dual/single pipe hydraulic lifting technology for heavy oil reservoirs, and conducted field practice. The research results and field practice show that the hydraulic pump lifting technology has good adaptability for both heavy oil sand production wells and heavy oil carbon dioxide huff and puff wells, effectively reducing the energy consumption of heavy oil lifting, significantly extending the pump inspection cycle of heavy oil sand production wells, significantly improving the lifting adaptability of carbon dioxide huff and puff wells, and has high promotion value in similar reservoirs and single wells.

Temporal variabilities of soil carbon dioxide fluxes from cornfield impacted by temperature and precipitation changes through high-frequent measurement and DAYCENT modelling

AbstractSoil carbon dioxide (CO2) emissions from the field of corn (Zea mays L.) play an important role in global warming. This study investigated temporal variability of soil CO2 fluxes (Rs) with soil temperature (Ts) and moisture (θ) and built DAYCENT models for predicting future impacts of climate changes on Rs using the measured high-frequency data. Rs trend was tested by Mann–Kendall and Sen Estimator. Predicted Rss under different climate scenarios were compared using Parallel-line Analysis. The findings indicated that daily Rs exponentially increased with Ts constrained by θ. During the θ of 27–31%, there was a strong exponential relationship between Rs and Ts, but the relationship was weaker for the θ of 38–41% and 22–26%. Soil environmental index (SEI, Ts × θ) significantly impacted Rs with linear regression Rs0.5 = 0.4599 + 0.002059 × SEI in 2008, 2009 and 2011. At the diurnal scale, there were different trends in Rss and relationships among Rs and Ts and θ in different years. Predicted yearly Rss, root Rss and corn yield in 2014–2049 increased with an increase in temperature scenarios, but the Rss significantly increased as temperature rose by 1°C or higher. Predicted yearly Rss, root Rss and yield reduced with precipitation scenario increase, and the root Rss and yield significantly diminished as precipitation increased by 15 and 30%. Predicted yearly Rs from cornfields had a significantly increasing trend. Future research is needed to explore methods for mitigating cornfield Rs and evaluating sensitivities of different cropland Rss to temperature changes.

Experimental and theoretical study on water solubility of carbon dioxide in oil and gas displacement

The emission of greenhouse gas carbon dioxide causes the global temperature to rise year by year. A possible method for CO2 storage and emission reduction is to use it to displace oil and gas. Solubility of CO2 in water is key to replace oil and gas. The present study investigates the effects of the temperature, pressure, and addition of salt and methane on the water solubility of CO2 by high temperature and high pressure cell combined with chromatographic analysis. The results show that the phase state of CO2 in water with temperature and pressure greatly affects its solubility. Besides, its solubility in the supercritical and liquid state is significantly greater than that in the gaseous state. The solubility of CO2 gas in brine and water increases with an increase in pressure; however, this increasing tendency gradually decreases. At the same time, the addition of CH4 gas can boost the dissolution of CO2 gas, while the addition of NaCl can significantly reduce its solubility; as the salt content in the water increases, the solubility of CO2 gradually decreases. Given the influence of saturated vapor pressure of water at vapor-liquid equilibrium, a thermodynamic constitutive equation was established to calculate the water solubility of CO2. The results showed that the prediction error of CO2 solubility in water is within 8%, that of pure CO2 is less than 4%. A comparison of these results with those predicted using the artificial neural network model showed that the thermodynamic model is more suitable for predicting water solubility required for replacing oil and gas by carbon dioxide.

Studying the effect of carbon dioxide oil solubility on asphaltene aggregation under conditions of the Bashkortostan Republic fields

The purpose of this work is to study the effect of carbon dioxide oil solubility on the aggregation of asphaltene associates and decrease of oil permeability of sandstones. Consideration is given to the interaction variants of oil and carbon dioxide in a free volume before being injected into a porous medium and immediately in the porous medium. The influence of oil composition on the aggregation of asphaltene associates is studied. The effect of the dissolved carbon dioxide on associate dispersion in oil is examined through oil filtering in sandstones. If asphaltene aggregation occurs in a porous medium it causes pore plugging leading to reduced permeability, complicates the development of carbon dioxide injection wells and, as a result, prevents from achieving the planned indicators of oil production and oil recovery. It is found that in the case when oil interacts with carbon dioxide in the free volume before being injected into a porous medium, the increase in the volume of filtered oil and the concentration of carbon dioxide dissolved in oil, and decrease in sandstone permeability reduce the relative mobility of oil with the dissolved carbon dioxide. The significant influence of sandstone permeability on the experimental results indicates that the sizes of asphaltene aggregates are comparable to the sizes of small pores. We have not observed complete attenuation of filtration after passing of oil with dissolved carbon dioxide through sandstones. Based on the analysis of changes in oil composition and properties carried out in the laboratory experiments on oil displacement by carbon dioxide rims, it has been determined that aggregation of asphaltene associates takes place under immediate contact of oil and carbon dioxide in a porous medium. The higher the asphaltene content in oil, the lower the formation permeability, whereas tight formations feature a more significant decrease in permeability.

Soil carbon dioxide emissions in a sorghum field: Row position and growth stage effects

AbstractSoil carbon dioxide emission (SCE) is known to be impacted by multiple factors including sources of respiration, environmental factors, and crop and soil management practices, yet few reports exist on how crop row position and growth stage affect SCE in sorghum [Sorghum bicolor (L.) Moench] fields. The objective of this study was to examine the effects of row position and growth stage on SCE dynamics in a field under grain and sweet sorghum production in northern Alabama. Soil CO2 emissions were measured weekly during the growth period using a closed soil CO2 survey chamber system. The results showed that SCEs increased steadily from approximately 4 μmol CO2 m–2 s–1 during the vegetative stage and reached maximum values of approximately about 5 μmol CO2 m–2 s–1 and 6 μmol CO2 m–2 s–1 for grain sorghum and sweet sorghum, respectively. Soil CO2 emissions then decreased to approximately 2 μmol CO2 m–2 s–1 at the maturity and post‐maturity periods for both sorghum types. Significant differences in SCE were observed between row positions. Soil CO2 emissions at the row (R) positions were 19% greater than at interrow (I) positions during the entire growing season under grain sorghum production. Significant difference occurred only during the vegetative stage (SCE at R was 9% greater than at I position) under sweet sorghum production. Additionally, a significantly greater response of SCE to soil temperature (Ts) during the vegetative stage was observed under sweet sorghum production but not grain sorghum production. This study provides evidence that SCE is affected by row position, growth stage, and crop type and suggests that crop row position and growth stage should be taken into consideration for SCE estimation.

A 6M digital twin for modeling and simulation in subsurface reservoirs

A 6M digital twin for modeling and simulation in subsurface reservoirs

A Comparative Study of CO2-Flood Displacement Efficiency for Different CO2 Injection Strategies: Permian Basin vs. U.S. Gulf Coast

In CO2-EOR, there are two main field development strategies: water-alternating-gas (WAG) and continuous gas injection (CGI). The aim of our study is to compare these strategies in terms of their economic performance (from the basis of incremental oil recovery) and in terms of their environmental performance (from the basis of ultimate CO2 storage volumes). Within this framework and to demonstrate the efficiency of each strategy, we evaluate the distribution of Carbon Dioxide in oil, gas, and brine phases; the amount of total CO2 stored at the end of the project; the incremental oil recovery; and the CO2 utilization ratios. In this study, we model and compare two fields which represent two different reservoir settings: Cranfield (representative of the U.S. Gulf Coast sandstone reservoirs) and SACROC (representative of the Permian Basin carbonate reservoirs). CGI is the original operating strategy in Cranfield and WAG is the original operating strategy applied in the SACROC unit. High resolution geocellular models are used for both Cranfield and SACROC fields. The models are constructed based on wire-line logs, seismic surveys, core data, and stratigraphic interpretations. A comprehensive pressure-production history matching for primary, secondary, and tertiary recovery is conducted for both of the fields. Different operating strategies are designed for each field (e.g. CGI and WAG). After finishing the history-matching, CGI and WAG scenarios are simulated in both models to compare their performances. CO2 partitioning in oil, brine, and gas phase (mobile or residual) are compared for both scenarios (WAG and CGI). The partitioning of CO2 in oil results in CO2 miscibility in oil, the partitioning of CO2 in brine results in CO2 dissolution in brine, and CO2 partitioning in gas phase are divided into structural trapping and residual trapping of CO2. We plotted the contribution of different trapping mechanisms over a post injection period for WAG and CGI for both SACROC and Cranfield. Additionally, the total CO2 storage, the incremental oil recovery, and CO2 utilization ratios are compared in both scenarios for both fields. Although actual operating strategy in these two fields are different (CGI in Cranfield and WAG in SACROC), our numerical modelling results show that WAG could not only balance the CO2 storage, incremental oil recovery, and CO2 utilization ratio but also store the trapped CO2 with lower risk of leakage in both fields (by decreasing the amount of structurally trapped CO2). Because of multiple alternation of CO2 and water slugs in WAG, this approach reduces the viscous instability and therefore the efficiency of oil recovery. Our study shows that the distribution of CO2 in different phases is different for each field. Because of the lower minimum miscibility pressure (MMP) and lighter initial oil saturation in SACROC, the partitioning of CO2 in oil is much higher in SACROC than in Cranfield. The dissolution of CO2 in brine is much higher in Cranfield because of the presence of strong aquifer near injection wells. The present work provides valuable insights for optimizing oil production and CO2 storage in a CO2-EOR project. Additionally, this study clearly shows the impact of development strategies on the relative importance of different trapping mechanisms.

Determination of crossover pressure for cedarwood oil in carbon dioxide

Solubility experiments were conducted to determine the crossover pressure for cedarwood oil (CWO) in CO2. A stirred reactor with an in-line loop connected to a GC was used. Two temperatures (25 °C and 85 °C) with nine pressures (6.9, 10.3, 13.8, 17.2, 20.7, 24.1, 27.6, 31.0, and 34.5 MPa) were tested. The GC-FID counts were used to measure CWO solubility and composition. Below 20.7 MPa, the solubility of CWO was higher in liquid CO2 (25 °C) than supercritical CO2 (85 °C). The crossover pressure for CWO in CO2 was calculated to be 23.7 MPa. The solubility isotherms for CWO in CO2 were similar to those for triglycerides in CO2, although the crossover pressure for CWO was much lower. An experiment was also conducted monitoring CWO extracted from Eastern red cedar sawdust spiked with CWO. The calculated crossover pressure from these extractions was significantly lower (18.5 MPa) than that determined from the stirred reactor experiments.

Real-Time Soil CO2 Respiration Rate Determination and the Comparison between the Infrared Gas Analyzer and Microrespirometer (MicroRes®) Methods

ABSTRACTSoil carbon dioxide (CO2) respiration is one of the important soil health parameters that provides a general assessment of soil microbial activity and soil quality. Soil respiration rates, however, have not been widely applied in soil testing protocols mainly because the traditional methods are either inconvenient, technically cumbersome or too expensive. Currently, only two methods are available for a true real-time soil respiration rate determination (<2 h): the infrared gas analyzer (IRGA) and the microrespirometer (MR or MicroRes®) methods. We analyzed the real-time soil respiration rates of 20 soil samples from fifteen states after various periods of incubation using the IRGA method and the MR method. The measured soil respiration rates ranged from 0.4 µL CO2/h/g to 9.0 µL CO2/h/g. Both methods show precision in soil respiration determinations (CV = 12.7% and 11.9%, respectively). Comparison of the results between the IRGA and MR methods indicates high degrees of agreement (r2 = 0.914). This study shows that the MR method is a simpler and more cost-effective alternative for real-time soil respiration rate determinations.

Use of real crude oil fractions to describe the high pressure phase behavior of crude oil in carbon dioxide

The knowledge about crude oil phase behavior at high-pressures is a challenge for scientists due to inherent complexity to this systems. Some works employ model systems attempting to predict crude oil behavior, but the results are normally poor. In this sense, the use of real crude oil fractions can be an alternative to improve the accuracy of the models used in these simulations. In this work, a light oil sample has been fractionated to generate four representative fractions. An approach to estimate the critical properties of these distilled fractions using only density and vapor pressure experimental data is presented. In sequence, phase behavior of the pseudo binary (carbon dioxide (CO2)+real crude oil fractions), multicomponent (mixture of fractions+CO2) and original crude oil+CO2 systems were determined using static synthetic method and static synthetic+NIR, with CO2 molar fraction range of 0.367-0.986, temperature range of 20⿿80°C and pressure up to 300bar. Binary interaction parameters (BIP) were estimated for each pair (CO2+distilled fraction) and employed to describe the phase behavior of a CO2+crude oil systems with Peng-Robinson equation of state (PR-EOS) and quadratic mixing rule. The results suggest that the use of real fractions can be a safer strategy for predicting the phase behavior of petroleum in carbon dioxide. Besides, NIR spectroscopy showed to be a good alternative to study phase behavior of dark/opaque systems.

Oil recovery and CO2 storage in CO2 flooding

ABSTRACTIn this study, the interfacial tension (IFT) of crude oil-carbon dioxide mixtures was measured to determine the minimum miscibility pressure. CO2 flooding with sand packs, long cores, and heterogeneous cores was conducted to investigate the oil recovery and storage efficiency. The experiment results show that the interfacial tension decreases linearly with increasing pressure at two different pressure ranges. Under immiscible condition, the oil recovery and storage efficiency are increased by 30.1% and 52.4% when the injection pressure is increased from 13 to 22 MPa, and improved by 16.3% and 22.04% when the permeability is decreased from 270 to 10 mD, respectively. Under miscible condition, increase of injection pressure can only lead to much slower increase of oil recovery and storage efficiency, and permeability almost has no influence on oil recovery and storage efficiency. The oil recovery and storage efficiency can be remarkably reduced by heterogeneity. Water alternating CO2 injection can improve the oil recovery and storage efficiency by 35.5% and 13.55%, respectively, compared with continuous injection.

Carbon dioxide compressibility factor determination using a robust intelligent method

Owing to the demanding applications and wide uses of supercritical carbon dioxide in oil, gas and chemical industries, fast and precise estimation of carbon dioxide compressibility factor is of a vital significance in order to be imported into the relevant industrial simulators. In this study, a data bank covering wide range of temperature and pressure was gathered from open literature. Afterwards, a rigorous novel approach, namely least square support vector machine (LSSVM) optimized with coupled simulated annealing (CSA) was proposed to develop a reliable and robust model for the prediction of compressibility factor of carbon dioxide. Reduced temperature and pressure are the inputs of the model. 80% of the dataset was used for training the model and the remaining 20% was used to evaluate its accuracy and reliability. Statistical and graphical error analyses have been conducted to investigate the performance of the model and the obtained results from the proposed model have been compared with those of six equations of state, REFPROP package and two correlations. It was demonstrated that the proposed CSA–LSSVM model is more efficient and reliable than all of the studied empirical correlations, equations of state and the software package, hence it can be utilized confidently for the prediction of carbon dioxide compressibility factor.

Effect of Temperature on Two-Phase Relative Permeabilities of Heavy Oil, Water, Carbon Dioxide, and Methane Determined by Displacement Technique

Two coreflood setups were used to measure heavy oil–water, heavy oil–carbon dioxide, and heavy oil–methane relative permeabilities. Using fractional effluents measured with precision meters and differential pressure data records, the Johnson–Bossler–Naumann technique was applied to calculate two-phase relative permeability in a consolidated sandstone core. In order to investigate the effect of temperature on the shape of relative permeability curves, a series of coreflood tests was conducted at three different temperatures (28, 40, and 52 °C) for each fluid pair. Analysis of the data obtained for the heavy oil–water system showed a linear increase of about 65% and 50% in water relative permeabilities when temperature ranged from 28 to 40 °C and 40 to 52 °C, respectively. However, although the oil relative permeability curve showed an increase of about 70% when temperature increased from 28 to 40 °C, it was dramatically decreased by about 30% when temperature was increased from 40 to 52 °C. In the case of heavy oil–gas a different effect was observed for methane and carbon dioxide. Although both methane and carbon dioxide relative permeabilities increased nonlinearly at higher temperatures, oil relative permeability in the presence of carbon dioxide decreased when temperature increased. In contrast, in the presence of methane, oil relative permeability experienced a reduction of 80% from 28 to 40 °C followed by a considerable increase of 15-fold from 40 to 52 °C.

Application Prospects of Supercritical Carbon Dioxide in Unconventional Oil and Gas Reservoirs

The technical problems during the development of unconventional oil and gas reservoirs are becoming more and more difficult to handle with conventional drilling and production methods. Supercritical carbon dioxide has so many good properties such as high rock-breaking drilling efficiency, strong dissolved displacement performance and unharmful effect on the reservoir that it can be used as a drilling, completion and production medium to effectively exploit the unconventional oil and gas reservoirs. The global distribution of unconventional oil and gas resources is introduced, application status of carbon dioxide in oil and gas development is discussed, and development prospects of supercritical carbon dioxide in the unconventional oil and gas reservoirs are systematically analyzed. Using supercritical carbon dioxide as a medium in the whole development process is an important trend of unconventional oil and gas development technologies.

Experimental Comparison of Nitrogen and Carbon Dioxide Oil Displacement in Carbonate Cores

The feasibility of nitrogen and carbon dioxide flooding is being investigated experimentally as possible enhanced oil recovery processes in Iranian carbonate oil fields. Laboratory tests were conducted on a tight permeability sample of an Iranian oil field. Three flooding tests were conducted at back pressures of 1,000, 2,000, and 2,500 psi for both nitrogen and carbon dioxide separately. All tests were conducted at constant temperature of 28°C. Experimental results indicate that immiscible carbon dioxide can mobilize more oil than immiscible nitrogen due to the ability of carbon dioxide to dissolve in oil. The key factor in higher recoveries of carbon dioxide injection compared to nitrogen is the ability of carbon dioxide to extract oil components. Extraction dominates after carbon dioxide breakthrough. Although the only mechanism of oil displacement in nitrogen flooding tests was the displacement energy applied by injection pressure, the oil recoveries in nitrogen flooding are considerable, especially at higher pressures.

Phase Equilibrium Measurements of Sacha Inchi Oil (Plukenetia volubilis) and CO2 at High Pressures

AbstractNew data on phase equilibria for Sacha inchi seed oil in carbon dioxide have been measured using a variable volume cell phase equilibria system at temperatures of 303, 313 and 323 K and at pressures ranging from 4.3 to 27.7 MPa. The CO2 mole fraction varied from 0.7488 to 0.9997. At the studied concentrations, phase transitions of vapor‐liquid, liquid‐liquid‐vapor and liquid‐liquid were observed. Sacha inchi oil contains 47% of omega‐3 fatty acids, with a ratio of 0.76:1 for omega‐6:omega‐3, which is good for human health. The Peng‐Robinson equation of state was used to describe the experimental data. A qualitative agreement was obtained between experimental and calculated data for the binary system CO2 and Sacha inchi seed oil.

Solubility Measurements and Data Correlation of Carbon Dioxide in Pentaerythritol Tetra(2-ethylbutanoate) (PEBE6)

Carbon dioxide is one of the most promising alternative refrigerants, but its compatibility with compressor lubricants is still almost unknown. The solubility of refrigerants in oils is one of the most important properties in the selection of the proper lubricant. For this reason, in our laboratories a systematic research program on the solubility of carbon dioxide in oils has been started, putting particular attention on its dependence on lubricant chemical structure, temperature, and pressure. In this paper, experimental solubility data and their correlation of carbon dioxide in a precursor of polyol ester oil, that is, pentaerythritol tetra(2-ethylbutanoate), are presented in the temperature range of (283 to 343) K and pressures up to 10 MPa.

Solubility of β-Carotene from Crude Palm Oil in High-Temperature and High-Pressure Carbon Dioxide

The solubility of β-carotene from crude palm oil using a phase equilibrium loading recirculating high-pressure-type apparatus at temperatures of (353.2, 373.2, and 393.2) K was studied. The experimental data showed that the mole fraction solubility of β-carotene was 2.27·10−2 at a temperature of 393.2 K and at pressure of 5.4 MPa. The experimental data were compared with a set of theoretical data that was calculated using the regular solution theory model (RSTM). The theoretical data showed that the RSTM was able to correlate the solubility of β-carotene from crude palm oil in carbon dioxide. The mole fraction solubility of β-carotene based on the RSTM was 5.30·10−3 at temperature of 393.2 K and at pressure of 3.3 MPa.

Modelling the extraction of essential oils with compressed carbon dioxide

Three models were used to describe the extraction of essential oils from oregano bracts using compressed carbon dioxide. They were developed on the basis of a plate-like geometry of the particles and were tested experimentally using various bract pre-treatments, pressures, temperatures and solvent flow rates. The two particle phase derived models applied, the Single Plate model (SP model) and the Simple Single Plate model (SSP model), differ only by the allowance or not for a film coefficient ( k f) and have as the only adjustable parameter the matrix diffusivity ( D m). The third model, the Fluid Phase/Simple Single Plate model (FP/SSP model), considers both the particle mass balance and a detailed description of the fluid mass balance. In addition to the matrix diffusivity the FP/SSP model may require the adjustment of the fraction of oil leached by the solvent during the pressurisation procedure ( f 0). All models gave a good fit to the experimental data though the FP/SSP model gave the best fit. However, the matrix diffusivities found correlated very poorly with the estimated diffusivity of essential oils in carbon dioxide ( D 12), which indicates a complex intraparticle transport.

Phase behavior of CO 2–perfluoropolyether oil mixtures and CO 2–perfluoropolyether chelating agent mixtures

Perfluoropolyethers and functionalized perfluoropolyethers have been shown to exhibit high solubility in liquid and supercritical carbon dioxide. A perfluoropolyether oil, Krytox 16350, molecular weight (MW) of 11 350, was fractionated into 14 monodisperse fractions using carbon dioxide at 373 K at pressures between 20.69 MPa and 34.47 MPa. The molecular weights of these fractions, determined using 19F NMR, ranged between 8160 and 29 252. The phase behavior of mixtures of carbon dioxide with each fraction was determined at 298 K. The two-phase boundary shifted to higher pressures as the MW of the perfluoropolyether oil fraction increased. The high solubility of these oils in carbon dioxide led to the development of a series of carbon-dioxide-soluble chelating agents. These amphiphilic compounds were composed of a CO 2-philic perfluoropolyether tail to enhance the solubility of the chelating agent in CO 2 and a hydrophilic chelating head group for metal ion extraction. CO 2-chelating agent phase behavior at 298 K was determined for chelating agents with bis(picolyl amine) or dithiol head groups and fluoroether tails with molecular weights of 2500, 4000 and 7500. As the MW of the tail increased, the overall MW of the chelating agent increased, tending to decrease solubility in CO 2. The increasing MW of the fluoroether tail also increased the chelating agent's CO 2-philicity, thereby enhancing the solubility of the compound in CO 2. These competing effects resulted in an optimum MW of the tail, 4000, for monofunctional chelating agents at 298 K, that minimized the pressure requirement for complete miscibility of the CO 2 and chelating agent.