Application of Acoustic Wave Propagation Analysis Methods for Monitoring a Miscible Mixing Zone in Porous Media

The Biot's acoustics theory, which describes acoustic wave propagation in a porous medium, and computer simulation techniques were utilized to model the behavior of acoustic waves entering and leaving a mixing zone in a miscible displacement in porous media. The results indicate that the angles of waves produced by a mixing zone are equal to angles of waves produced by an abrupt fluid-fluid interface. Therefore, acoustic methods and a relationship between the incident, reflection, and transmission angles can be used to determine the location and thickness of the mixing zone during a miscible displacement process in porous media.     

Experimental Investigation of Miscible CO2 Flooding

Abstract

Management of water alternating gas (WAG) injection projects requires making decisions regarding the WAG ratio, half-cycle-slug size, and ultimate solvent slug size. The impact of these decisions affects the capital cost and ultimate incremental oil recovery. Core flooding runs were conducted on 2 and 4 ft core samples. Injection scheme (continuous gas injection [CGI] vs. WAG), WAG ratio, and slug size were investigated. In addition, miscible WAG flooding as a secondary process was investigated and its efficiency was compared to the conventional tertiary miscible gas flooding. Miscible gas flooding at different miscible WAG parameters (WAG ratio and slug size) indicate that 1:2 WAG ratio at 0.2 PV slug size is the best combination yielding the highest recovery and tertiary recovery factors. Miscible WAG flooding as a secondary process indicated a higher ultimate recovery compared to the conventional tertiary WAG flooding. However, a larger amount of gas injection is consumed particularly in the early stages of the injection process. Miscible CGI mode conducted using n-Decane as oleic phase appears to have better performance than miscible WAG injection in term of recovery. When light Arab crude oil was used as oleic phase, higher recovery was obtained for miscible WAG flooding. The reversal trend seen in is believed to be due to the presence of crude oil, which alters the rock wettability toward an oil-wet condition, preventing the water blockage during the WAG process.     

Investigation of Low Frequency Elastic Wave Application for Fluid Flow Percolation Enhancement in Fractured Porous Media

In recent years, some numerical models have been proposed to investigate the effects of the elastic wave such as ultrasonic on fluid flow behavior in porous media. Nevertheless, none of these models are applicable to the fractured reservoirs, especially when the fluid is a Bingham plastic. In this work, the model proposed by P. P. Iassonov and I. A. Beresnev (2003) Iassonov, P. P. and Beresnev, I. A. 2003. A model for enhanced fluid percolation in porous media by application of low-frequency elastic waves. J. Geophys. Res., 108: 2138–2146. [Crossref], [Web of Science ®] , [Google Scholar] for flow under exposure of elastic wave in nonfractured porous media is considered and used for development of a new model of steady state flow of a Bingham plastic fluid in fractured reservoirs. The Kazemi's “block and fracture” model assuming negligible vertical permeability in blocks is considered for modeling. In addition, two-phase flow behavior under elastic wave in fractured system is investigated. The results showed that, at higher pressure gradients, vibration amplitude cannot highly influence the fluid percolation, in contrast at lower pressure gradients, the fluid flow through the fractured porous media can considerably be improved by increasing vibration amplitude. Also, it has been found that in two-phase flow systems, wave can increase the produced oil-water ratio in the fractured media. The results of this study can be applied to the fractured reservoir simulations and can be a path breaking to the future studies on the prediction of flow enhancement under elastic wave in the fractured reservoirs.     

The Feasibility of Lab-scale Cyclic CO2 Injection in Fractured Porous Media

A comprehensive analysis of the CO₂ Huff-n-Puff process with application to representative light oil system contained within a fractured porous media is present in this article. To accomplish this work, a simulation model representative of the laboratory experimental model was built and constrained under similar laboratory conditions. Six sets of CO₂ Huff-n-Puff experiments were conducted at injection pressures of 1723–10342 kPa; moreover, additional sensitivity analysis was performed on the 5170 and 6894 kPa conditions for different permeability and porosity. Results of this study demonstrate that cyclic injection of CO₂ under miscible conditions performs more favorably than under immiscible injection conditions.     

Effect of stress sensitivity on displacement efficiency in CO2 flooding for fractured low permeability reservoirs

Carbon dioxide flooding is an effective means of enhanced oil recovery for low permeability reservoirs. If fractures are present in the reservoir, CO2 may flow along the fractures, resulting in low gas displacement efficiency. Reservoir pore pressure will fluctuate to some extent during a CO2 flood, causing a change in effective confining pressure. The result is rock deformation and a reduction in permeability with the reduction in fracture permeability, causing increased flow resistance in the fracture space. Simultaneously, gas cross flowing along the fractures is partially restrained. In this work, the effect of stress changes on permeability was studied through a series of flow experiments. The change in the flowrate distribution in a matrix block and contained fracture with an increase in effective pressure were analyzed. The results lead to an implicit comparison which shows that permeability of fractured core decreases sharply with an increase in effective confining pressure. The fracture flowrate ratio declines and the matrix flowrate ratio increases. Fracture flow will partially divert to the matrix block with the increase in effective confining pressure, improving gas displacement efficiency.     

The Application of a New Association Equation of State (AEOS) for Prediction of Asphaltenes and Resins Deposition During CO2 Gas Injection

Abstract

Asphaltene deposition is a serious problem that can cause fouling in the reservoir, well, pipeline, and the oil production and processing facilities. An association equation of state (AEOS) is one of the most useful models used to predict asphaltene phase behavior and asphaltene deposition conditions. For an AEOS, it is assumed that the total compressibility factor consists of physical and chemical parts. The authors apply the conventional form of compressibility factor developed by G. Soave (1972) Soave, G. 1972. Equilibrium constants from a modified Redlich-Kwong equation of state. Chem. Eng. Sci., 27: 1197–1203. [Crossref], [Web of Science ®] , [Google Scholar] to the physical compressibility factor. However, for the chemical compressibility factor a new form is proposed. The total compressibility factor obtained is then used to calculate the asphaltene and resin deposits. The amounts of deposited asphaltenes calculated through the proposed model along with the experimental results are used to calculate resin deposit. A comparison with the experimental results shows that the new proposed model can be used to predict the amounts of deposited resins and asphaltenes within an acceptable range of accuracy.     

多孔介质中CO2水合物饱和度与阻抗关系模拟实验研究

确定沉积物中天然气水合物饱和度是评估水合物资源、开发利用天然气水合物工作中的一项基础而关键的工作。利用青岛海洋地质研究所自主设计、研制的天然气水合物阻抗监测模拟实验装置,研究了CO ₂气体与去离子水在多孔介质中天然气水合物的生成与分解过程。指出：天然气水合物生成过程会使多孔介质阻抗增大;天然气水合物分解过程导致多孔介质阻抗减小。并且多孔介质的阻抗变化与反应体系的温度压力变化相互对应,能够体现天然气水合物生成与分解各阶段的特点。此外,还利用Archie公式,使用天然气水合物的阻抗值计算多孔介质中水合物的饱和度,得到了多孔介质中天然气水合物饱和度随反应时间的增长曲线。     

An Efficient Methodology for Performance Optimization and Uncertainty Analysis in a CO2 EOR Process

Abstract

A pragmatic technique is proposed and successfully applied to determine the optimal production–injection scheme in a CO₂ flooding reservoir under uncertainty. Well rates of injectors and bottomhole pressures of producers are chosen as the controlling variables. Geological uncertainty is accounted for using the multiple reservoir models. An objective function associated with net present value (NPV) is defined, and a modified genetic algorithm is employed to determine the optimal production–injection scheme. It is shown from a field case study that the optimized scheme can not only increase the expected oil recovery and NPV by 7.8 and 6.6%, respectively, but can also achieve a considerably small range of possible NPVs.     

Screening of Oil Pools on Alaskan North Slope and Phase Behavior Study of Viscous Oil and CO2 System in Conjunction with CO2 Sequestration

Abstract

Carbon dioxide gas, a greenhouse gas (GHG), is released in the atmosphere by combustion of solid waste, wood, and fossil fuels for energy generation. Due to conspicuous absence of CO₂ sequestration studies for Alaska, the study of CO₂ sequestration options on North Slope has a very important role to play. The screening of the oil reservoirs to evaluate the technical feasibility with respect to their CO₂-EOR potential was performed by calculating the rank of the oil reservoirs with parametric approach. CMG-WinProp® simulator was used to predict phase behavior for CO₂ injection in viscous oil by tuning the equation-of-state.     

含杂质超临界-密相CO2管道输送工艺参数优化

CO_2输送作为CCUS技术实现的中间环节,承担着将CO_2从捕获地输送到封存点的重要任务,结合原油、天然气管道的经验可知,由于管道输送具有输量大、安全可靠性高、连续性强等优势,是目前最主要的CO_2输送方式。根据国外40多年的CO_2管道输送经验,由于超临界-密相CO_2具有类似于液体的高密度和类似于气体的高扩散性与低黏度,被认为是最经济的管道输送方式。以国内某油田30×10~4 t/a CCUS项目为例,采用Pipephase模拟软件对不同管径的超临界-密相CO_2管道在相同入口参数下进行模拟计算,分析研究不同管径下的管道压力、温度、密度与输送距离之间的变化规律,得出含杂质超临界-密相CO_2最优管道输送工艺参数,为后续我国CCUS项目推广和发展提供理论依据。     

Visualization of CO2 and oil immiscible and miscible fl ow processes in porous media using NMR micro-imaging

CO₂ flooding is considered not only one of the most effective enhanced oil recovery（EOR） methods,but also an important alternative for geological CO₂ storage.In this paper,the visualization of CO₂ flooding was studied using a 400 MHz NMR micro-imaging system.For gaseous CO₂ immiscible displacement,it was found that CO₂ channeling or fingering occurred due to the difference of fluid viscosity and density.Thus,the sweep efficiency was small and the final residual oil saturation was 53.1%.For supercritical CO₂ miscible displacement,the results showed that piston-like displacement occurred,viscous fingering and the gravity override caused by the low viscosity and density of the gas was effectively restrained,and the velocity of CO₂ front was uniform.The sweep efficiency was so high that the final residual oil saturation was 33.9%,which indicated CO₂ miscible displacement could enhance oil recovery more than CO₂ immiscible displacement.In addition,the average velocity of CO₂ front was evaluated through analyzing the oil saturation prof ile.A special core analysis method has been applied to in-situ oil saturation data to directly evaluate the local Darcy phase velocities and capillary dispersion rate.     

国外CO2驱流度控制进一步扩大波及体积方法

CO₂驱油是一种有效的提高采收率方法,矿场成功应用已有60多年。理论上微观驱油效率接近100%,但相对原油,CO₂的低黏度低密度与储层的非均质性导致的黏性指进和重力分离两大典型问题大大降低了气体波及系数。本文综述了国外各种流度控制方法,包括气水交替、聚合物直接稠化CO₂、CO₂泡沫驱、气-化学剂联合方法及气体辅助重力泄油,简要介绍了CO₂驱扩大波及体积的其他方法,分析了每种方法的机理及优缺点,力图为我国CO₂驱油进一步扩大波及体积这一难题积累先进做法和经验。     

孔径双峰分布γ-Al2O3负载NiMoP催化剂的制备及对蜡油加氢催化性能

在氢氧化铝干胶挤条成型时,调节纳米炭黑的加入量和水/粉质量比,制备了孔径呈双峰分布、具有较大孔容和比表面积的γ-Al2O3载体。当炭黑加入质量分数为13%、水/粉质量比1.15时,制备的孔径呈双峰分布的γ-Al2O3载体的孔容为0.80mL/g、比表面积为309m2/g,4～10nm和10～15nm孔径分别占总孔容50.8%和35.1%(体积分数),采用该载体制备的NiMoP/γ-Al2O3催化剂的孔径呈明显的双峰分布。在反应温度370℃、氢分压10MPa、氢/油体积比700、体积空速1.5h-1的条件下,制备的NiMoP/γ-Al2O3催化剂可使减压和焦化混合蜡油的硫质量分数由25600μg/g降至2070μg/g,脱硫率为91.9%,而参比催化剂仅可使减压和焦化混合蜡油硫质量分数降至3450μg/g,脱硫率为86.5%。     

The Impact of CO2 Injection and Pressure Changes on Asphaltene Molecular Weight Distribution in a Heavy Crude Oil: An Experimental Study

Abstract

This work concerns observing the pressure as well as CO₂ mole percentage effects on asphaltene molecular weight distributions at reservoir conditions. A high-pressure, high-temperature asphaltene measurement setup was applied, and the amount of precipitated asphaltene at different pressures as well as CO₂ mole percentage in an Iranian heavy crude oil was measured. Moreover, the asphaltene molecular weight distributions during titration of crude oil with different n-alkanes were investigated. The gel permeation chromatography (GPC) apparatus was used for characterization of asphaltene molecular weight under different conditions. It has been observed that some thermodynamic changes such as pressure depletion above the bubble point increase the average molecular weight of asphaltene and cause the asphaltene molecular weight distributions changes from a bimodal curve with two maxima to a single maxima curve. One the other hand, below the bubble point, pressure reduction causes a decrease in the average molecular weight of asphaltene and also causes the shape of asphaltene molecular weight distributions to restore, which might be due to dissolution of asphaltene aggregates. An interesting result is that asphaltene molecular weight distribution at the final step of pressure reduction tests, ambient condition, shows approximately the same trend as the distribution of asphaltene molecular weight obtained at reservoir condition. This behavior explains the reversibility of the asphaltene precipitation process under pressure depletion conditions. In the case of CO₂ injection, the graphs of asphaltene molecular weight distributions always show a single modal trend and shift toward larger molecular weight values when CO₂ mole percentage increases. The results of this work can be imported to thermodynamic models that use polydisperse data of heavy organic fractions to enhance their performance at reservoir conditions. The distributions obtained by this method are good indicators of asphaltene structures at reservoir conditions.     

Effects of titanium dioxide nanoparticles on the efficiency of surfactant flooding of heavy oil in a glass micromodel

Nanotechnology has the potential to profoundly change enhanced oil recovery and to improve mechanism of recovery, and it is chosen as an alternative method to unlock the remaining oil resources and applied as a new enhanced oil recovery method in last decade. The objective of this research is identification of potential of nanotitanium dioxide as an appropriate agent for improving the efficiency of surfactant flooding in five-spot glass micromodels. In this work a series of solvent injection experiments was conducted on horizontal glass micromodels at same conditions. Surfactant solutions and newly developed nanosurfactant solutions with 1600–2000 ppm sodium dodecyl sulfate were tested. Observations showed that nanotitanium dioxide has appropriate performance in enhancing the oil recovery at surfactant solution, near critical micelle concentration conditions. Also The results of experiments illustrated improvement of heavy oil recovery in micromodel test with nanotitanium dioxide (51.0%).     

A New Approach for Accurate Prediction of the Phase Behavior of the Complex Mixtures of Acid Gases,Hydrocarbons, Water,and Methanol in the Petroleum Industry

In this work a new approach for accurate prediction of the vapor-liquid equilibrium of the complex mixtures of water, methanol, acid gases (H₂S, CO₂), and hydrocarbons considering the hydrogen bonding association, hydrolytic dissociation, and acid gas solvation effects is presented. The overall average absolute deviation between the predicted and measured compositions regarding 330 sour gas mixtures is about 3.22%. The proposed CPA/electrolyte model is quite reliable over wide ranges of temperatures and sour gas concentrations and can be employed for accurate design of sour natural treatment and flow assurance systems in oil and gas industries.     

Performance Evaluation of Cyclic Pressure Pulsing in a Depleted,Naturally Fractured Reservoir with Stripper-Well Production

Abstract

We present a parametric study on the operational parameters of cyclic pressure pulsing with N₂ and CO₂. We aim to develop a better understanding of how operational parameters affect the process performance in a shallow, naturally fractured, and depleted reservoir of the Big Andy Field in eastern Kentucky. The study includes analyses of various design parameters such as the injection rate, lengths of injection and soaking periods, cycle rate limits, and number of cycles. Incremental oil production, peak oil rate, and net present value (NPV) are considered as the performance criteria. Analyses have been performed using a single-well, dual-porosity, compositional reservoir model.     

The Utilization of Natural Reservoir Brine in an Enrichment Culture Medium: An Alternative Approach for Isolation of Anaerobic Bacteria from an Oil Reservoir

This study aims to suggest the new approaches of enrichment cultures using natural reservoir brine for enrichment culture medium in order to increase the bacterial population in the enrichment cultures and isolate novel thermophilic anaerobic bacteria from an oil reservoir. The results suggest that the brine-based culture medium should be sterilized by filtration to increase the number of bacterial population and CO₂ should be supplied to culture medium to increase the possibility of isolating novel bacteria from oil reservoirs. One of the specific bacteria isolated under the presence of CO₂ was a strain AR80 representing a novel bacterium within the genus Petrotoga on the basis of the phylogenetic analysis.     

A numerical simulation study of CO 2 injection for enhancing hydrocarbon recovery and sequestration in liquid-rich shales

Less than 10% of oil is usually recovered from liquid-rich shales and this leaves much room for improvement, while water injection into shale formation is virtually impossible because of the extremely low permeability of the formation matrix. Injecting carbon dioxide (CO₂) into oil shale formations can potentially improve oil recovery. Furthermore, the large surface area in organicrich shale could permanently store CO₂ without jeopardizing the formation integrity. This work is a mechanism study of evaluating the effectiveness of CO₂-enhanced oil shale recovery and shale formation CO₂ sequestration capacity using numerical simulation. Petrophysical and fluid properties similar to the Bakken Formation are used to set up the base model for simulation. Result shows that the CO₂ injection could increase the oil recovery factor from 7.4% to 53%. In addition, petrophysical characteristics such as in situ stress changes and presence of a natural fracture network in the shale formation are proven to have impacts on subsurface CO₂ flow. A response surface modeling approach was applied to investigate the interaction between parameters and generate a proxy model for optimizing oil recovery and CO₂ injectivity.     

Investigation of immiscible CO2 and C1 injection and comparison with water injection for enhanced oil recovery in naturally fractured reservoirs

Reservoir oil and gas content tends to rise up to the surface as long as their potential energy levels are sufficient. In order to amplify this energy, either during the time when oil is uprising on its inherent energy or since after, so as to facilitate the traveling of oil to the surface, enhanced oil recovery (EOR) methods come into play. Furthermore, the increasing demand for oil from one hand, and the shrinkage of producible reserves on the other hand, have made it unavoidable to undertake EOR techniques. Built in this research was a 10-element model of reservoir fluid to simulate its behavior. Furthermore, slim tube simulation was undertaken to determine minimum miscibility pressure for various gases. Then, different scenarios of natural depletion, CO₂ injection, methane injection, and water injection were simulated by ECLIPSE 300 software package with the results of different scenarios compared. The results indicated water injection to be associated with higher recovery factor.