Oil Mass Research Articles

Creating values from wastes: Producing biofuels from waste cooking oil via a tandem vapor-phase hydrotreating process

This study is focused on producing biofuels from waste oils via a tandem vapor-phase hydrotreating process in a pressurized two-stage fixed bed reactor over a bifunctional Ni/Al2O3-SiO2 catalyst under 0.25 MPa H2. A 100% hydrodeoxygenation efficiency both in liquid and gas products was observed, yielding 83.9 wt% C5-C19 n-alkanes which corresponds to a 7.4-fold increase compared with that obtained from non-catalytic conversion. The hydrodeoxygenation mechanism of waste cooking oil in the catalytic tandem hydrotreating process induced by Ni/Al2O3-SiO2 was proposed. The hydropyrolysis temperature in the first reactor, hydrogenation temperature in the second reactor, reaction pressure, catalyst to waste cooking oil mass ratio, and gas hourly space velocity (GHSV) was optimized at 550 °C, 300 °C, 0.25 MPa, 3, and 56 s−1, respectively. The application potential of this cascade vapor-phase hydrotreating process was evaluated by employing different waste oils such as palm kernel oil, woody oil (swida wilsoniana), soapstock, and waste lubricating oil as feedstock, giving C5 to C19 n-alkane yields ranging from 21.6 to 87.5 wt%. This work provides a novel and promising approach to upcycle waste oils into upgraded biofuels compared with conventional catalytic pyrolysis.

Influence of pad geometry and method of oil supply on the thermal state of GTE rotor tilting-pad journal bearing

High heat generation in the hydrodynamic wedge is one of the main factors limiting application of pad journal bearings as bearings for rotors of aircraft gas turbine engines. The goal of the research is to study the influence of the oil supply method on the bearing thermal state and to determine the design factors reducing the bearing temperature. The study was carried out with the use of bearings with diameters of 100320 mm with different design of the oil supply: through oil dispensing grooves in the pads, through oil nozzles in the inter-pad space, using lead-in chamfers for the pads, with oil bypass channels. The tasks posed were solved by using volumetric geometric models with the tools of computational fluid dynamics in the ANSYS CFX package in which differential equations describing the model are solved by the finite element method. The patterns of temperature and pressure distribution over the surface of the lower, most loaded bearing pad were obtained for various options of oil supply and different geometry of bearing pads; values of the bearing load carrying capacity, maximum pressure in the working gap, the oil mass flow through the elements of the oil supply; dependences of the bearing static performance on the distance between the shaft and nozzles. Oil supply through oil dispensing grooves made in pads is a factor that negatively affects the bearing thermal state, which is associated with so-called locking of the working gap. It is shown that implementation of oil supply through the space between the pads is more efficient. The use of a lead-in chamfer with plain inserts simplifies oil supply to the working gap. The design solutions described make it possible to reduce the maximum oil temperature in the bearing by 36 degrees Celsius.

One-phase Transesterification of Palm Oil in to Biodiesel with Co-solvent Methyl Esters: The Effect of Adding Co-solvent to Kinetic Energy and Dipole Moment

In the transesterification process, the problem is the low solubility of oil in methanol, so the reaction will run slowly. The solution to this problem is to add a co-solvent to increase the solubility so that a one-phase reaction will be formed. The co-solvent methyl ester is the right choice because it is a product of the reaction itself so that it does not require a separation process. The operating conditions of the study were mass of palm oil 250 g, mass of NaOH catalyst 0.8%wt, stirring speed 100 rpm, reaction temperature 60oC, the molar ratio of oil:methanol = 1:6, reaction time (5,10,15,20,25,30 minutes), and the mass of co-solvent (0,5,10,15%wt). The first stage of the research was to make co-solvent, then proceed with the transesterification reaction by adding co-solvent which was carried out according to the research operating conditions. The optimum condition of the study was obtained at reaction time 30 minutes and the addition of co-solvent 5%, with yield 97.4171%. The density of FAME 0.88 g/mL and the concentration of FAME 99.963% which complied with SNI 7185-2015. The simulation results of ChemDraw for components of triglyceride+methanol+NaOH+co-solvent obtained kinetic energy 3479.0264 kJ/mol and dipole moment 43279.8007 debyes.

Exploring the effects of substrate mineral fines on oil translocation in the shoreline environment: Experimental analysis, numerical simulation, and implications for spill response

Mineral fines act a pivotal part in determining the fate and behavior of oil. In this study, the infiltrations of oil emulsion in simulated sediments and natural shoreline sediments were investigated using a fixed bed experiment. Oil infiltration process was simulated based on fixed-bed dispersion model. The role of mineral fines in oil release was explored using simulated and natural sediments. Although mineral fines exhibited a higher affinity for oil, it was found that increasing fines fractions decreased the flow rate of oil emulsion, thereby decreasing the oil retention in the sediment column. In terms of oil release from the sediment, the highest level of oil mass was observed in the oil-mineral flocculation phase compared to the water column and the water surface compartments. Compared to light crude oil, the release of engine oil from sediment was less. The effects of mineral fines on oil infiltration and release were also confirmed by using natural shoreline sediments. Results of our detailed field studies also showed that current shoreline classification datasets do not characterize the presence and fraction of mineral fines at a level of detail required to accurately predict the significance of oil translocation following spill incidents.

Methodological aspects of a new method for determining the mass of oil in bottom sediments of water bodies

A method is proposed for determining the mass of oil pollution per unit area of bottom sediments of water bodies, which makes it possible to associate pollution not only with the concentration of pollutants, but also with the area of the reservoir. The approach relates to the field of environmental protection, in particular to the analytical control of the content of oil pollution in mineral, organogenic and mixed bottom sediments. It can be used for environmental monitoring of polluted water bodies, for assessing the damage caused to a water body, and for planning treatment works. The method for determining the mass of oil pollution per unit area of bottom sediments of water bodies includes sampling, drying the sample to an air-dry state, extraction of oil products from bottom sediments, chromatographic separation of oil products from associated organic compounds of other classes, quantitative determination of oil products by absorption intensity in the infrared spectrum. A survey of 88 oil-contaminated reservoirs within the Samotlor oil field in the north of Russia was carried out, in which the proposed method was tested.

Effects of oil properties on the formation of oil-particle aggregates at the presence of chemical dispersant in baffled flask tests

The formation of oil-particle aggregates (OPA) is the major sedimental pathway of spilled oil, which can bring great harm to both the benthic communities and marine environment. In this paper, effects of GM-2 chemical dispersant and oil properties on the formation of OPA was investigated by the EPA baffled flask test. The addition of dispersant can promote the formation of OPA from montmorillonite and five test oils obviously. With the increase of the dispersant dosage, the size of trapped oil in OPA increased and the density of OPA decreased. The dispersant can increase the kinematic viscosity of crude oil, and high viscosity of the oil is advantageous for the formation of OPA. The oil-seawater interfacial tension is reduced after the addition of dispersant, which makes oil dispersed into the water column easier. A kinematic equation of dispersed oil concentration attenuation was modified by introducing the oil property coefficient β. The modified empirical equation can calculate the mass of oil in sunken OPA in oil spill accidents.

Visualization study on oil retention and flow characteristics of R32/PVE oil in suction lines with different flow orientations

Oil retention characteristic and flow patterns of R32/PVE lubricant oil mixture in compressor suction lines were investigated. Smooth copper tubes with 10.7mm inner diameter and four tube orientations including horizontal flow, vertical upward flow and inclined upward flow with 45° and 60° inclined angles, were utilized as test samples. Saturation temperature and superheat degree were maintained at 7.5°C and 12°C, respectively. The operation conditions of refrigerant mass flux and nominal oil mass fraction covered ranges of 48.5−230 kg•m−2•s−1 and 1−5%, respectively. The oil retention amount was measured by the remove and weight technique. Based on the visualization technique, flow patterns of R32/oil mixture were also observed, identified and analyzed. The characteristic of flow patterns was greatly influenced by the thermophysical properties of refrigerant-oil mixture. Comparisons of existing flow pattern maps and wet wall fraction correlations were conduct to investigate the applicability. The experimental result showed that oil retention in suction lines increased with the decrease in refrigerant mass flux and increase in oil mass fraction. The oil retention amount of 60° inclination suction line was slightly higher than that for 45°. Additionally, the difference of oil retention among the four configurations becomes limited at high mass flux conditions.

Identifying of Unsteady Performance of Oil to Water Heat Exchanger Integrated with Process

There are many approaches by which the heat exchanger can be modeled depending on how much information is available to start with. Grey-box model represents one of these approaches which is considered in the present study to modeling the unsteady operation heat exchanger. The available measurements of an unidentified heat exchanger integrated with a process involving oil circulation were statistically analyzed to extract the information that could aid in its identification. The proposed heat exchanger system included a hot oil stream coming from the thermal unit process and cooled by a cold-water circuit. The objective of this study is to develop a grey box model for the unspecified heat exchanger with a suitable nonlinear state-space structure and solved numerically using MATLAB-19 software and engineering equation solver (EES). Suitable parameters included oil and water inventories, heat addition, and conductance divisor factor are chosen to fully identify the heat exchanger from measured temperatures and flow rates. The parameters used to identify the oil process included the oil mass inventory within the process and the quantity of heat added. While for the heat exchanger; oil, water, and solid thermal masses were determined along with a conductance divisor to close its model. The results revealed that, comparing the model output with the measured data was satisfactory. The effect of 10% increment in the oil process heat as external excitation on a heat exchanger can only be controlled by water and oil flow rates and any fluctuation in inlet water temperature is insignificant and considered as a noise disturbance. An increment of 19% in the oil flowrate with unchanged water flowrate resulted in an increase in oil outlet temperature by about 4%. applying a noise of about ±10% on inlet water temperature to the system resulted in insignificant effects on the oil temperatures, and therefore it could be considered as uniform temperature. An effective control system to manage the heat exchanger and therefore the process can be designed according to the predictions of changing the water and oil flow rate responses.

Improvement in engine thermal management by changing coolant and oil mass

Several investigations related to increasing engine thermal efficiency focusing on the engine hydraulic circuits (oil and coolant) were performed over the last years. According to literature, more than 20% of the fuel energy is rejected to the coolant in steady state conditions. Thus, better use of that energy, especially during warm up of the engine, would lead to an improvement of engine performance and fuel consumption. In the present work, a complete engine and its subsystems were modeled and validated in a 0D/1D in-house software. After, several case studies based on modifying the volume of the engine hydraulic circuits were simulated and analyzed. The simulations were performed for steady state and transient conditions. On one hand, the impact of the present thermal management strategy was practically negligible in steady state conditions. On the other hand, for transient conditions and ambient boundary conditions, the results showed that by reducing the coolant volume by 45% the reduction in warm up time and fuel consumption compared with the base case were 7% and 0.4% respectively. Additionally, for cold conditions, the impact was even higher, obtaining a reduction of warm up time and fuel consumption of 13% and 0.5% respectively.

Synthesis of mesoporous Pt@KIT−6/SAPO−11 VIA in situ encapsulation to catalyze the decarboxylation of oleic acid to C8–C17 alkanes

AbstractBACKGROUNDA series of mesoporous Pt@KIT−6/SAPO−11 catalysts with SiO2:Al2O3 molar ratios of 0.3, 0.4, or 0.5 and Pt loadings of 0.4, 0.8, or 1.2 wt% were prepared via an in situ encapsulation process using a PEO − PPO − PEO triblock copolymer (EO20PO70EO20, P123) as the mes. China 750001 oporous template and KIT−6 molecular sieves as the silicon source.RESULTSThese catalysts were characterized by transmission electron microscopy (TEM), specific surface area analysis, and pyridine–infrared spectroscopy (Py − IR). The results showed that Pt nanoparticles with particle sizes of 3–7 nm were uniformly dispersed on the supports. These materials also exhibited good mesoporous structures with specific surface areas of 138–197 m2/g and average pore sizes of 7.1–9.9 nm. The specimens having a SiO2:Al2O3 molar ratio of 0.4 also showed an orderly strip−shaped pore structure. The Py − IR results indicated that the catalysts had both Brønsted acid and Lewis acid sites, with total acid contents in the range of 77.8–131.1 μmol/g.CONCLUSIONThe decarboxylation of oleic acid using these materials under CO2 was examined. The catalyst with a SiO2:Al2O3 molar ratio of 0.4 and a Pt loading of 0.8 exhibited the best catalytic performance and a C8 − C17 alkanes yield as high as 85.1% at 340 °C by using a catalyst−to−oil mass ratio of 1:10 and a reaction time of 5 h. This performance was attributed to the ordered mesoporous structure of this catalyst along with its high surface area (173 m2/g), good crystallinity (92.8%), suitable acid content (98.6 μmol/g), and abundant Pt metal active sites. © 2022 Society of Chemical Industry (SCI).

Molecular Dynamics Simulation and Experimental Studies of the Wettability Behaviors of Shales

The wettability behaviors of nanoscale pores in shales from Longmaxi Formation in the Sichuan Basin of South China, which contain quartz pores, illite pores, and organic matter pores, were investigated using the molecular dynamics simulation and experimental methods, and the organic matter surface was approximated by grafting oxygenated functional groups onto a graphite surface. The distribution characteristics of a water–methane system in organic matter pores were studied. The results indicate that the organic matter pore network and the inorganic pore network in shales show cross-distribution characteristics. The speed of spontaneous imbibition of oil is less than that of water, and the spontaneous imbibition mass of oil increases with increasing the total organic carbon (TOC) contents. The surfaces of illite and quartz mineral are hydrophilic. With the increase in oxygen-containing functional groups, the interaction energy between the organic matter surface and water molecules decreases, resulting in an increase in the wetting contact angle of the organic matter surface. With increasing temperature, the interaction energy between the organic matter surface and water molecules increases, resulting in a decrease in the wetting contact angle. In symmetrical graphite pore models with different C/O ratios, water molecules are symmetrically spread near the oxygen-functionalized graphite wall, and with a decrease in the C/O ratio, the relative concentration of water molecules increases and the diffusion coefficient decreases. In contrast, methane molecules are gathered and distributed in the center of the pore. In an asymmetric graphite pore model with different C/O ratios, water molecules are asymmetrically spread near the oxygen-functionalized graphite wall, whereas methane molecules are concentrated and spread in the pore center. The side with a lower C/O ratio has stronger hydrophilicity and a higher relative concentration of water molecules, whereas the side with a higher C/O ratio has stronger hydrophobicity and a lower relative concentration of water molecules.

Determination of optimal oil pumping plans

This paper presents the results of determining the optimal plans for pumping oil through the main oil pipelines of Kazakhstan. The calculation methodology is based on determining the minimum unit cost of pumping depending on oil flow rate. Oil pumping energy-saving modes are determined under optimal operating conditions of pumping units and heating furnaces at stations. Determination of the optimal pumping plan is implemented as a separate module of the SmartTranPro software. Pumped oil volumes on the oil pipeline sections were determined on the basis of the automated system of control and metering of electrical energy data of KazTransOil JSC. Optimal pumping plans for monthly oil volumes in the Kalamkas – Karazhanbas and Dzhumagaliev – Atasu pipeline sections for cold and warm periods were calculated on the basis of the found dependence of the pumping unit cost. For each range of oil mass flow rate, specific costs for oil pumping and a list of operating pumps at oil pumping stations located along the pipeline section are indicated.

Operational Modeling of North Aegean Oil Spills Forced by Real-Time Met-Ocean Forecasts

Over the latest decades, oil marine pollution has posed a vital threat for global ocean health, since spillages of any scale are related to environmental, social and financial impacts. The worldwide increase in oil and gas demand, and the parallel rise in oil and gas production, exploiting particularly coastal and offshore marine deposits, have significantly increased the risk of accidental oil release to the sea. In the present study, an operational oil spill model was applied to test the oil dispersive properties and to reveal the relative magnitude of weathering processes, after an accidental oil spill release along the main tanker transportation route in the North Aegean Sea. Numerical simulations were implemented using the OpenOil transport and fate numerical model, a subclass of the OpenDrift open-source trajectory framework. This model integrates algorithms with several physical processes, such as oil entrainment, vertical mixing, oil resurfacing and oil emulsification. The oil dispersion model was coupled to real-time met-ocean forecasts received from NOAA-GFS and CMEMS. Present simulation results have focused on the impact of turbulent kinetic energy, induced by the background flow field, on the horizontal spreading of particles, as well as on the evolution of oil mass balance and oil mass properties.

Nontraditional oil sorbents: Hydrophilic sponges with hydrophobic skin layer for efficient oil spill remediation

Advances in the use of porous materials for oil-water separation offer a promising avenue for solving oil spill problems. Conventionally, to realize selective oil absorption, porous sorbents need to be fully hydrophobized with low-surface-energy chemicals. However, such exhaustive hydrophobization brings about problems of excessive chemical consumption, high cost and increased environmental hazards, hindering the practical applications of sorbents. Here, an innovative type of oil sorbent is developed via a facile liquid film-based dip coating technique. Unlike conventional fully-hydrophobized sorbents, only the outmost layer of our sorbent is modified with hydrophobic polydimethylsiloxane (PDMS) coating while the inner part remains hydrophilic, thus achieving 80% reduction in low-surface-energy chemical consumption. The prepared sorbent allows highly selective oil absorption from oil-water mixture, as the hydrophobic skin layer blocks water entrance and the hydrophilic inner part drives oil absorption. More importantly, our sorbent significantly speeds up oil absorption, and compared with conventional hydrophobic sponges, the absorption time is reduced by 36% for absorption of the same mass of crude oil, attributed to the strong capillary absorption of its hydrophilic inner channels. This sorbent also shows larger specific absorption capacity than its fully hydrophobized counterpart. Our study provides a general strategy to develop cost-effective and environmental-benign sorbents with enhanced oil spill absorption performances.

REMOVAL OF HIGH-MOLECULAR COMPOUNDS UNDER ACTION OF BAF-1 REAGENT INCLUDED BY DEPOSITS DURING STORAGE OF TRANSPORTED OIL IN TANKS

Sedimentation occurs during storage and transportation of all produced oil, which leads to a reduction in the effective capacity of tanks, corrosion spills, difficulty in checking the condition of the tank, a large amount of oil loss and, most importantly, changes in the composition of oil. This, in turn, leads to a decrease in the volume of the fraction during oil refining. In order to effectively combat sediment formation, it is necessary to determine its essence, as well as the basic laws of this process. One of the most important problems in the operation of tanks is their cleaning. During long-term operation, sediment accumulates at the bottom of the tanks, which reduces their useful volume and complicates their operation. Sedimentation in tanks is due to the separation of solid phases in the oil and its subsequent deposition. This is a natural and necessary process that is directly related to the increase in the concentration of heavy components - asphaltene, resin, paraffn in the total volume of oil during the mixing of different oils. On the other hand, the separation of the solid phase depends on the physical and chemical properties of the oil, temperature and a number of other factors, and the intensity of accumulation depends on the design and maintenance characteristics of the tank. During long-term storage of oils of different densities and viscosities, depending on the constantly changing temperature regime of storage conditions, sediment accumulates at the bottom and walls of the tank and is unevenly distributed over the area. Its relative thickness is observed in areas far from the intake and distribution pipes, which does not allow to more accurately determine the actual amount of oil in the tank. Over time, the sediment thickens; washing is difficult in some areas, and sometimes not at all. To ensure efficient and reliable operation of the tanks it is important to regularly clean them of accumulated sediment. One of the most important problems in the operation of tanks is their cleaning. During long-term operation, sediment accumulates at the bottom of the tanks, which reduces their useful volume and complicates their operation. Sedimentation in tanks is due to the separation of solid phases in the oil and its subsequent deposition. Manual cleaning of tanks from oil sludge is a fairly common method of cleaning. First of all, this method is used to clean small tanks. When cleaning the tanks in this way, the tank is first steamed, then washed at a temperature of 30-50 ° C and a pressure of 0.2-0.3 MPa. The device used for pumping water consists of a pump and an ejector. The washing water is pumped along with the oil sludge. The solid sediment and sand are removed with a shovel, a shovel and a bucket. Cleaning of tanks from sediments is a dangerous labor-intensive work and requires considerable material costs. Even the most advanced chemical-mechanized treatment method does not eliminate human manual labor and requires preparation for the installation of additional equipment, as the main problem in technological and commercial tanks is the formation of high-molecular asphaltene and resin paraffin compounds in oils. The component composition of asphaltene-resin-paraffin sediments (ARPS) varies widely over a single oil recovery region, even within a single field. Knowing the composition of ARPS is of practical importance in determining the optimal methods of combating them, or more precisely in the selection of chemical reagents. A 1:1:1 mixture of all three sediments conventionally called BAF-1. the coordination polymer was injected and expelled until a dry residue was obtained (450-600 °C) and the sample was cooled and RFA analyzed. In order to prevent the formation of coagulants, it is important to pre-inject anticoagulant into the oil mass in the tank, which can successfully perform this task with the reagent we offer. As for the cleaning (washing) of the already formed sediments, the proposed reagent can break down large coagulants (associations) and ensure their re-dissolution in the oil mass. Keywords: asphaltene, resin, paraffin, associate, Balakhani, Bulla, Diogenes, BAF-1.

Using Box–Behnken Design Coupled with Response Surface Methodology for Optimizing Rapeseed Oil Expression Parameters under Heating and Freezing Conditions

The effect of heating and freezing pretreatments on rapeseed oil yield and the volume of oil energy under uniaxial compression loading was investigated. Four separate experiments were carried out to achieve the study objective. The first and second experiments were performed to determine the compression parameters (deformation, mass of oil, oil yield, oil expression efficiency, energy, volume of oil and volume of oil energy). The third and fourth experiments identified the optimal factors (heating temperatures: 40, 60 and 80 °C, freezing temperatures: −2, −22 and −36 °C, heating times: 15, 30 and 45 min and speeds: 5, 10 and 15 mm/min) using the Box–Behnken design via the response surface methodology where the oil yield and volume of oil energy were the main responses. The optimal operating factors for obtaining a volume of oil energy of 0.0443 kJ/mL were a heating temperature of 40 °C, heating time of 45 min and speed of 15 mm/min. The volume of oil energy of 0.169 kJ/mL was reached at the optimal conditions of a freezing temperature of −36 °C, freezing time of 37.5 min and speed of 15 mm/min. The regression model established was adequate for predicting the volume of oil energy only under heating conditions.

Modeling for extraction of oil from walnut and sesame using batch flow cold press oil extraction system.

In this study, a batch flow oil extraction system was used for extraction of oil from walnut (Juglans regia L.) and Sesamum (Indicum sesame). Sample mass (g), applied pressure (MPa), and processing temperature of oil (°C) were selected as independent variables and oil extraction mass percentage and oil analysis as dependent variables. Response surface methodology was employed for conducting statistical analysis, modeling, and data optimization. The results revealed that the highest percentage of oil extraction for walnut was obtained at a pressure of 10.5 MPa, a temperature of 31.5°C, and a sample weight of 8 g, with a value of 25.36%. Also, the highest percentage of oil extraction for Sesamum was obtained at the pressure of 13.88 MPa, the temperature of 31.5°C, and a sample value of 20 g with a value of 22.4%. Optimal level of independent variables for walnut and sesame were 8.03 g, 10.41 MPa, and 27.37°C; 20 g, 13.88 MPa, and 27°C, respectively. In this optimum condition, the amount of sesame and walnut peroxide was 10 ± 0.03 and 1.9 ± 0.07 (meq O2/kg), respectively. Likewise, the amount of acid for sesame and walnut was 1.53 ± 0.05 and 0.06 ± 0.02 g/%, separately. Linoleic acid (42.7–51.15), oleic acid (38.6–24.03), palmitic acid (10.87–8.21), and stearic acid (5.5–3.39) were the most common fatty acid components in sesame and walnuts, respectively.

Fatty acid solvent extraction from palm oil using liquid–liquid film contactor: Mathematical model including mass transfer effects

Free fatty acid (FFA) presence in vegetable oils (VO) promotes unwanted organoleptic characteristics. Its traditional removal is carried out by steam distillation (deodorization). However, the high temperature of this process promotes the formation of toxic components such as glycidol esters (GE) and 3-monochloropropane-1,2-diol (3-MCPD). FFA extraction by solvents is an alternative refining process at low temperatures which preserves natural phytonutrients that are thermically destroyed or distilled in deodorization. In this work, a model to predict continuous co-current FFA extraction with a liquid–liquid film contactor (LLFC) using ethanol as a solvent at low temperature (<80 °C) was developed and experimentally validated. This model includes the prediction of the FFA mass transfer from the oil-rich phase to the interface. Experimental validation also assessed the effects of flow rate (0.5–1.5 kg/h), ethanol to oil mass flow rate (1–2), FFA initial concentration (2–4 wt.%), and LLFC stages employed on FFA removal. At the best operational conditions experimentally evaluated, it was possible to reduce the FFA content from 4 wt.% to 0.08 wt.%. The mathematical model shows an approximate description of the LLFC behavior and mass transfer effects that can be used for the scale-up of the technology.

Experimental Investigation of Phase Behavior of Condensate Gas and Crude Oil System in Underground Gas Storage

Abstract The phase behavior of reservoir fluids is crucial for the smooth operation of an underground gas storage (UGS). In this work, three experiments were conducted to investigate the phase behavior of condensate and crude oil systems within different development stages of gas storage in Bohai Bay Basin of eastern China. In stage 1, constant volume depletion (CVD) test was conducted to simulate the interaction of the original condensate gas-live oil system. In stage 2, the phase behavior of a series of mixtures of live oil with 47.5, 58.3, 69.9, and 77.4 mol% of condensate gas was studied by constant composition expansion (CCE) test. In stage 3, a new experiment was designed to study the mass transfer and phase behavior during cyclic injection-production process of the underground gas storage. The results from the CVD test describe the effect of each pressure stage on produced gas composition and equilibrium oil properties in the condensate crude oil system. The results of the CCE test indicate that condensate gas can expand the oil and improve the properties. The results of cyclic injection-production experiment demonstrate that the mass transfer in condensate gas and oil system is a dual mechanism of condensation and vaporization. With the increase of the cycle, the intermediate components of oil phase are enriched and the heavy components decreases. After four cycles, the oil and gas interphase mass transfer reaches dynamic equilibrium. In addition, test results show that multicycle operation is beneficial to improve the oil properties. This work is of great significance to understand the phase transition mechanism of underground gas storage, which provides a basis for other researchers to further update and improve the EOS model.

Mechanism of Loading Fracture of Coal Mass and Formation of Oil and Gas Disaster Channel in Coal and Oil Resources Costorage Area

Fracture structure characteristics are crucial for determining the fracture mechanism of coal mass and the migration law of oil and gas disasters. In this study, computed tomography (CT) scanning technology and fractal theory were used to investigate the damage process of coal mass in the common storage area of coal and oil resources under uniaxial compression as well as the degree of damage of high-pressure oil and gas diffusion to the surrounding coal and rock mass. Uniaxial compression and acoustic emission signal acquisition tests of coal mass were conducted. The relationship among the load evolution law of coal samples at different positions around the oil well and the failure mode of key failure positions were further analyzed. Finally, the formation mechanism of coal load fracture and oil and gas disaster channel in coal and oil resource costorage area was investigated. The test results showed the following: (1) High-pressure oil and gas diffusion degrades the mechanical properties of coal mass in varying degrees. The closer the coal sample to the oil well, the greater the fracture development degree, the fracture density, the fracture fractal dimension of coal sample, and the severity of the coal mass damage and the lower the compressive strength, the acoustic emission event number, and the cumulative energy. (2) The lateral diffusion of high-pressure oil and gas changes the failure mode of coal samples in the common storage area of coal and oil resources. The failure modes when the sampling location is away from the oil well are step failure, conjugate shrinkage failure, and high-frequency vibration intermittent microcrack fracture. (3) Coal mass instability and coal mine oil and gas disaster in the common storage area of coal and oil resources can easily be induced by the formation of microfracture expansion, extension, and coalescence caused by coal failure, the formation of network and macrochannels of main fracture, and the instantaneous release of accumulated stress during failure.