Light Oil Components Research Articles

Two-dimensional spectrum characteristics and oil movability study of the shale oil reservoir

Shale oil is mainly stored in the nano–micro-pores of shale in the form of adsorption or in a free state. Among them, only free-state oil is the main contributor to shale oil production under natural elastic energy. Therefore, it is crucial to evaluate the movability of crude oil effectively. In this paper, focusing on the Jurassic shale oil reservoir core in the middle-eastern Sichuan region of China, low-field nuclear magnetic resonance (NMR) technology is used to analyze the basic characteristics of shale oil core samples. Experiments on the low-field NMR one-dimensional and two-dimensional spectrum characteristics of the original core, heat-treated core, and thermogravimetric-treated shale core are carried out. The effects of the TG-MS method, T2 method, and the volatilization of light oil components on the movability of shale oil reservoirs are analyzed, and the movability characteristics of shale oil reservoirs in the middle-eastern Sichuan region are preliminarily clarified. The results show that under thermal treatment, the distribution range of the two-dimensional spectrum of the core oil occurrence area is significantly reduced, and the T1 and T2 distribution ranges are reduced by 10.9% and 60.7%, respectively. According to the TG-MS method, the mobile oil, bound oil, and adsorbed oil account for 74.7%, 8.1%, and 17.2%, respectively. The quantitative calculation of movable oil saturation by NMR combined with heat treatment is 65.6%, which is lower than that calculated using the thermogravimetric method. In order to calculate the movability more accurately, the scale effect between different samples should be considered. This study could provide a theoretical basis for the subsequent shale oil development program.

Elucidating the impact of ultrasonic treatment on bituminous oil properties: A comprehensive study of viscosity modification

As global energy needs rise and traditional oil production wanes, heavy and viscous oils are becoming increasingly important. This study explores the use of ultrasonic technology to reduce oil viscosity. We investigated the relationship between ultrasonic exposure duration and changes in bituminous oil composition, using chromatography-mass spectrometry to analyze chemical alterations in oil samples pre and post-ultrasonic treatment. Viscosity changes at varied temperatures and shear rates were measured using a vibration viscometer and a rheometer. Our results showed that the viscosity reduction ratio (VRR) peaked at over 30% after 3 min of ultrasonic exposure. However, some processing methods and oil compositions led to increased viscosity. Post-treatment, lighter oil components were more prevalent, suggesting that ultrasonic exposure disrupts long carbon chains, reducing viscosity. Conversely, viscosity increases may result from molecular reconnection within bituminous oil. This research provides insights into a novel method for reducing heavy oil viscosity using ultrasonic technology, broadening our understanding of its applications in energy science and highlighting its potential to revolutionize heavy oil utilization.

Organic Matter Source, Fluid Migration, and Geological Significance of Stylolites in Organic-Lean Carbonate Rocks: A Case from the Sichuan Basin

Carbonate rocks exhibit significant heterogeneity as both a source rock and reservoir. Stylolite formation plays a crucial role in the enrichment of organic matter and the migration of geofluids within carbonate rocks. In order to study the enrichment mechanism of organic matter and the geofluid migration mode in the stylolites developed in carbonate rocks, stylolite-bearing core samples from the Dachigan structural belt in the eastern Sichuan Basin were collected. The stylolites and matrix were subjected to the total organic carbon (TOC) test and Rock-Eval pyrolysis, thin-section observation under fluorescent light, whole-rock X-ray diffraction, carbon and oxygen isotope analysis, and scanning electron microscopy. The organic matter occurring in the stylolites is mainly in the form of three types: soluble organic matter, pyrobitumen, and bitumen. This suggests that the organic matter within the stylolites mainly consists of secondary migrated organic matter. The stylolites also exhibit well-developed secondary dolomite and pyrite resulting from late-diagenetic recrystallization. These minerals contribute to the preservation of intercrystalline pore spaces and fractures, providing favorable conditions for oil and gas accumulation and migration. The strong cementation observed at the contact between the stylolites and matrix, along with the presence of secondary minerals nearby, may be attributed to the fractionation of light and heavy oil components during the migration of hydrocarbon fluids from the matrix to the stylolites. The thicknesses of the stylolites vary within the bulk, indicating severe diagenesis in thinner areas. Consequently, this leads to significant fractionation effects. The fractionation of crude oil components by stylolites poses challenges for the study of definitive oil–source correlations. To overcome these challenges, future research could investigate biomarker compounds to attempt oil–source correlations. Additionally, future efforts should take into consideration the spatial variation in the crude oil properties. Understanding the role of stylolites in organic matter enrichment and geofluid migration is crucial for optimizing exploration strategies in the Sichuan Basin, a region of growing importance in the energy industry. Moreover, our findings shed light on the complex interactions within stylolite-bearing rocks, which are not limited to this specific basin. These insights offer valuable contributions to the broader field of geology and reservoir characterization, enhancing our ability to predict and interpret similar geological formations globally.

Cross-interaction of volatiles in fast co-pyrolysis of waste tyre and corn stover via TG-FTIR and rapid infrared heating techniques

Using fast infrared heating technology to minimize the pyrolysis temperature differential and optimizing secondary reactions is advantageous for studying co-pyrolysis behaviors. In this study, the co-pyrolysis behaviors of waste tyres (WT) and corn stover (CS), including product distribution, pyrolysis kinetics, and thermodynamics, were studied using TGA-FTIR analysis and fast infrared heating reactor. The DTG curves for the co-pyrolysis of WT and CS significantly differed from the calculated values, implying that the pyrolysis intermediates produced by CS during the pyrolysis process may have synergetic effects with the pyrolysis of WT. The apparent activation energies using the Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods were similar, 244.88 kJ/mol and 245.93 kJ/mol, respectively. The experiment results suggest that the bio-oil yield increased first and then decreased with a further temperature increase. The yield of bio-oil gradually increased from 35.36% to 46.06% as temperature rose from 500 °C to 700 °C; but the further increasing to 800 °C decreased the bio-oil yield to 40.72%. The aromatic compounds in tar gradually increased with increasing the temperature, while the aliphatic compounds increased initially and then reduced. Meanwhile, the oxygenated compounds first decreased and then increased with increasing the pyrolysis temperature. The yield of light oil components (C＜10) increased from 5.11% at 400 °C to 7.71% at 700 °C. A further increase in the pyrolysis temperature to 800 °C reduced the light oil content to 4.93%.

Full-component cascade utilization of waste cooking oil in asphalt materials

Resources utilization of waste has become a global challenge with both environmental and economic issues. To realize the refinement recycling of waste cooking oil (WCO), a novel strategy was proposed in this work for the cascade utilization of different components of WCO in asphalt materials. Given the characteristics of each component in WCO, the analysis and verification were carried out for WCO as aged asphalt rejuvenators, warm mix asphalt additives, and thermal storage materials for asphalt thermoregulation. The results show that WCO components can be classified into three categories based on the nature of the fatty acid esters, namely waxy components, light oil components, and heavy oil components. Both light oils and heavy oils demonstrate great potential as rejuvenators of aged asphalt in terms of rheological properties and microscopic characteristics. Furthermore, it is worthy of expectation to select appropriate WCO components for performance recovery according to the actual aging degree of asphalt pavement. The waxy components of WCO can be applied for asphalt thermoregulation and warm mix asphalt additives after hydrolysis and ammonolysis respectively, which is conducive to improving the durability of roads, reducing the energy consumption and volatile organic compounds emissions during the construction process. The findings of the study contribute to the sustainable development of highway engineering and the recycling of waste resources.

Molecular insight into the oil displacement mechanism of CO2 flooding in the nanopores of shale oil reservoir

With the increasing demand for petroleum, shale oil with considerable reserves has become an important part of global oil resources. The shale oil reservoir has a large number of nanopores and a complicated mineral composition, and the effect of nanopore confinement and pore type usually makes the effective development of shale oil challenging. For a shale oil reservoir, CO2 flooding can effectively reduce the oil viscosity and improve the reservoir properties, which can thus improve the recovery performance. In this study, the method of non-equilibrium molecular dynamics (NEMD) simulation is used to simulate the CO2 flooding process in the nanoscale pores of shale oil reservoir. The performance difference between the organic kerogen slit nanopore and four types of inorganic nanopores is discussed. Thus, the effects of nanopore type and displacement velocity on the nanoscale displacement behavior of CO2 are analyzed. Results indicate that the CO2 flooding process of different inorganic pores is different. In comparison, the displacement efficiency of light oil components is higher, and the transport distance is longer. The intermolecular interaction can significantly affect the CO2 displacement behavior in nanopores. The CO2 displacement efficiency is shown as montmorillonite, feldspar > quartz > calcite > kerogen. On the other hand, it is found that a lower displacement velocity can benefit the miscibility process between alkane and CO2, which is conducive to the overall displacement process of CO2. The displacement efficiency can significantly decrease with the increase in displacement velocity. But once the displacement velocity is very high, the strong driving force can promote the alkane to move forward, and the displacement efficiency will recover slightly. This study further reveals the microscopic oil displacement mechanism of CO2 in shale nanopores, which is of great significance for the effective development of shale oil reservoirs by using the method of CO2 injection.

Influence of sodium hypochlorite/ultrasonic pretreatment on sewage sludge and subsequent hydrothermal liquefaction: Study on reaction mechanism and properties of bio-oil

Subcritical hydrothermal liquefaction (HTL) is an efficient approach for bio-oil production from wet sewage sludge (SS). Before HTL, pretreatment of wet SS by sodium hypochlorite (NaClO) or combination of NaClO and ultrasonic treatment was implemented with different NaClO dosage or ultrasonic temperature for the first time. The results demonstrated that TOC and content of protein in EPS of SS increased after two pretreatment methods. Meanwhile, the bio-oil yield was improved and the maximum of 39.4 wt% was obtained from the bio-oil under combined pretreatment (9.39 mg NaClO/g dried SS and ultrasounds at 80 °C) when HTL was performed at 300 °C for 15 min. Additionally, the maximum energy recovery reached 58.0% with the highest carbon recovery (61.9%) and the highest hydrogen recovery (39.0%) in bio-oils obtained from HTL of combined pretreated SS. GC-MS and NMR analysis showed that the chemical compositions of bio-oil were not affected significantly by pretreatment methods but relative percentage of each compound was changed. The esters formation was favored after combined pretreatment and increased to 16.3%, while the contents of acids and N-containing compounds decreased by 8.2% and 4.0%, respectively. TGA of bio-oils revealed that both pretreatments could promote the formation of light oil components such as diesel. Finally, the main possible reaction pathways for HTL of SS have been elucidated. Overall, this research provided a theoretical foundation for utilization of wet SS from sewage treatment plant directly for bioenergy production.

Effects of CO2 injection volume and formation of in-situ new phase on oil phase behavior during CO2 injection for enhanced oil recovery (EOR) in tight oil reservoirs

CO2 injection in tight oil reservoirs is a proved method for enhanced oil recovery. The mass transfer between CO2 and oil makes the reservoir fluid phase behaviors very complex, and directly affects the recovery process. In this paper, a comprehensive study of interactions between CO2 and live oil and their phase behaviors were conducted by CO2 visual injecting experiment. Based on the calculation of phase equilibrium and entropy, the mass transfer of CO2 and live oil was divided into four stages, and the mechanism of CO2-live oil interactions elucidated. The results indicate that after CO2 injection, the oil will expand immediately, and the expansion of the oil volume is proportional to the pressure increase. In the early stage of CO2 injection, the mass transfer between CO2 and live oil will form an in-situ gas phase. The reduction in light oil components is mainly due to the CO2 dissolution and replacement, supplemented by the CO2 extraction, which resulted in a rapid decrease in oil volume. With the increase in CO2 injection, its ability to dissolve in the oil and replace the oil components weaken, and CO2 extraction becomes the main controlling factor for the reduction of light components of oil. Increasing pressure promotes the extraction capacity of CO2 for light oil components. Entropy change can accurately reflect the mass transfer process between CO2 and oil, during CO2 injection. These results can furnish an in-depth understanding of the complicated mechanisms and phases behavior in CO2 EOR in tight reservoirs.

Quantitatively evaluating greenhouse gas leakage from CO2 enhanced oil recovery fields

Greenhouse gas (mainly CO2 and CH4) leakage from abandoned wells in CO2 enhanced oil recovery sites is a long-standing environmental concern and health hazard. Although multiple CO2 capture, utilization, and storage programs, e.g., CarbonSAFE and Regional Carbon Storage Partnerships, have been developed in the U.S. to reach the net-zero emission target by 2050, one cannot neglect the significant amount of CO2 and CH4 leakage from abandoned wells. This study will investigate the potential of CO2 and oil components leakages from the abandoned wellbore and develop the first-ever quantitative approach to evaluating CO2 and oil component leakage from a CO2 enhanced oil recovery field. Results show that in addition to a large amount of CO2 leakage, a significant amount of light and intermediate oil components leaked through the wellbore. In contrast, a minimal amount of heavy oil component leaked. Oil components’ leakage is mainly through the gas phase rather than the liquid phase. CO2 leakage is positively correlated to reservoir depth, wellbore pressure, and permeability through sensitivity analysis. In contrast, it is negatively related to net-to-gross ratio, residual oil saturation, and mole fraction of CH4. On the other hand, oil component leakages are positively correlated to all uncertain parameters, except the net-to-gross ratio. Lastly, the reduced-order models generated using the machine learning technique have a relatively high fidelity. Cited as: Chen, B., Mehana, M. Z., Pawar, R. J. Quantitatively evaluating greenhouse gas leakage from CO2 enhanced oil recovery fields. Advances in Geo-Energy Research, 2023, 7(1): 20-27. https://doi.org/10.46690/ager.2023.01.03

Effect of solvent on the adsorption behavior of asphaltene on silica surface: A molecular dynamic simulation study

In recent years, the hybrid thermal-solvent process has been widely applied to improve the recovery performance of steam injection processes in heavy oil reservoirs. In this paper, the method of Molecular Dynamics (MD) simulation is employed to illuminate the asphaltenes adsorption behavior in the thermal-solvent recovery process. Three different solvent molecules (CO2, C3H8, and nC4H10) and SARA (Saturates, Aromatics, Resins, Asphaltenes) simulated heavy oil model are constructed as the basic simulation model. A series of MD simulations at different temperature conditions are performed. Results show that for the SARA model, the asphaltene molecules can interact with the silica by a T-shape stacking, finally forming the asphaltene dense aggregates as a basic heavy oil occurrence state. The steric hindrance effect of other SARA components can also contribute to this configuration. Temperature significantly affects the adsorption configuration of asphaltenes by disassembling the dense core and loosening the structure of the aggregates. For the SARA model in three solvent atmospheres, the increasing temperature can benefit the extraction of light components. CO2 can only extract saturates, while nC4H10 and C3H8 can simultaneously extract the saturates and aromatics. Besides, asphaltenes re-precipitation behavior can be observed in the 393 K CO2 atmosphere. Both nC4H10 and C3H8 have mutual solubility with the heavy oil system. No apparent precipitation of asphaltenes occurs in the above two atmospheres. Comparing the performance of extraction capability and diffusion capability in all MD simulations, the nC4H10 can both extract light oil components and control the asphaltenes precipitation. It further reveals that nC4H10 can recover heavy oil more efficiently at a microcosm level. Among the three different solvents, nC4H10 is the optimal solvent for hybrid thermal-solvent processes in heavy oil reservoirs.

Mechanism of Extractive Separation of Light Cycle Oil Using a Deep Eutectic Solvent Composed of Tetrabutylphosphonium Bromide and Levulinic Acid

To achieve maximum usage and economically upgrade light cycle oil, it is necessary to separate light cycle oil components into nonaromatic and aromatic fractions. A deep eutectic solvent composed of tetrabutylphosphonium bromide and levulinic acid exhibited excellent extraction performance in separating light cycle oil components. In this work, the mechanisms of deep eutectic solvent formation and light cycle oil separation are investigated using characterization analysis and molecular dynamics simulations. Both Fourier-transform infrared spectra and molecular dynamics simulation results indicate that the main driving force for deep eutectic solvent formation is hydrogen-bonding interactions between the Br– anion of tetrabutylphosphonium bromide and the carboxyl group (−COOH) of levulinic acid. On the other hand, while the TBP+ cation of tetrabutylphosphonium bromide and the carbonyl group (−C═O) of levulinic acid are less likely to contribute to deep eutectic solvent formation, they are more likely to interact with the aromatic ring of tetralin via CH−π and π–π interactions, respectively. The results suggest that each functional group of tetrabutylphosphonium bromide and levulinic acid plays an essential role either in deep eutectic solvent formation or in aromatic compound extraction, which provides insights into the mechanism of extractive separation of light cycle oil components using deep eutectic solvents.

Molecular Insights into Asphaltene Aggregation in Gas Flooding

The gas flooding has been well developed and been widely used for heavy oil recovery. The extraction of light oil components by injecting gas with supercritical properties could destroy the stable asphaltene colloidal structure and induce asphaltene aggregation and precipitation, which greatly threatens reservoir permeability and wellbore safety. In this work, employing molecular dynamic simulations, the asphaltene aggregation behavior in gas flooding was investigated. Three kinds of injecting gases, CO2, CH4, and C3H8, and three temperatures at 350, 410, and 470 K were adopted to study the effects of injecting gas types and temperature on asphaltene aggregation. Simulation results indicate that the asphaltene aggregation degree is high in CO2 flooding, and it increases with decreasing temperature. Furthermore, the spatial structure and intermolecular interaction were discussed to unveil the underlying mechanism of asphaltene aggregation. This work reveals molecular-level insights of asphaltene aggregation in gas flooding under different temperature, which is expected to facilitate future studies on controlling asphaltene precipitation in gas flooding.

Pyrolysis behavior of low-density polyethylene over HZSM-5 via rapid infrared heating

Catalytic fast pyrolysis experiments of low-density polyethylene (LDPE) over HZSM-5 were carried out by using infrared heating technology. The effects of heating rate (1–30 °C/s), pyrolysis temperature (450–650 °C), and mass ratio of catalyst to LDPE (0:100 to 50:100) on product distribution and oil composition in LDPE pyrolysis were investigated, and the fast pyrolysis mechanism was explored. The results indicated that a higher heating rate, namely 20 °C/s, can remarkably enhance the liquid oil yield (93.42%), but the oil is heavy due to about 90% high‑carbon n-aliphatics. The addition of HZSM-5 performed an excellent effect on obtaining high-quality liquid oils, among which the total content of monocyclic aromatic hydrocarbons (MAHs) and iso-aliphatics obviously increase from 0.68% to 70.26%. The optimal HZSM-5/LDPE ratio of 10:100 was identified by considering the cost-effective factor. Furthermore, the lower catalytic temperature is favorable to the generation of light oil components, especially MAHs. The feasible generation paths were proposed, which mainly derived from the secondary reaction of the intermediate formed by initial chain cleavage including cyclization, aromatization, Diels-Alder reaction, as well as isomerization.

Photothermal Fabrics for Efficient Oil-Spill Remediation via Solar-Driven Evaporation Combined with Adsorption.

Oil spill rapidly destroys aquatic system and threatens humans, requiring fast and efficient remedy for removal of oil. The conventional remedy employs water-floating oil adsorbents whose volume should be large enough to accommodate all oil ingredients. Here, we suggest a new concept for efficient oil-spill remediation, which combines solar-driven evaporation of light oil components and simultaneous adsorption of heavy oil components, namely, solar-driven evaporation of oil combined with adsorption (SEOA). To design photothermal oil absorbents for the efficient SEOA, we designed carbonaceous fabrics with high photothermal heating performance and oil-adsorption capacity by carbonizing nonwoven cotton fabrics. For three model organic solvents of octane, decane, and dodecane floating on water, the fabrics, respectively, accelerated the evaporation in factors of 2.0, 4.4, and 2.3 through photothermal heating under simulated sunlight condition. For the 1.18 mm thick crude oil floating on water, 70 and 77 wt % of crude oil were evaporated within 2 and 16 h, respectively, with the photothermal fabrics, whereas only 22 and 34 wt % was evaporated in the absence of the fabrics, indicating the dramatic enhancement of oil removal by solar-driven evaporation. The remaining heavy oil components were accommodated in the pores of the fabrics, removal of which showed an additional 18 wt % reduction; that is, a total 95 wt % of the crude oil was removed. The oil-treatment capacity is as high as 110 g g-1, which has never been achieved with conventional oil adsorbents to the best of our knowledge. We believe that our combinatorial SEOA approach potentially contributes to minimizing the environmental disaster through a fast and efficient oil-spill remediation.

Investigation of gas hydrate formation and inhibition in oil-water system containing model asphaltene

Gas hydrate and asphaltene are two major flow assurance issues that will cause severe plugging in the subsea transportation pipelines, but the detailed understanding of their interactions remains insufficient. Systematic experiments were performed in the present study to investigate the influence of light oil components and asphaltene on gas hydrate formation, and to evaluate the performance of commercial kinetic hydrate inhibitors (KHIs) in different oil-water systems. Results demonstrated the promotion effect of light oil on initial hydrate growth, and the inhibition effect of asphaltene particularly with the light oil solvent of toluene. The influence mechanisms of asphaltene were based on the weakening mass transfer of methane at the gas-liquid interface, and the adsorption of free methane in the bulk liquid phase, while the degree of inhibition on hydrate formation was not positively related to the total concentration of asphaltene. Results also indicated that light oil components can weaken the performance of KHIs, but the role of asphaltene was closed related to the type of KHIs and light oil solvent. The overall experimental results of gas hydrate formation in the asphaltene system are consistent with our previous molecular dynamics simulations researches. Meanwhile, it provides an implication that asphaltene may have a potential ability to help some KHIs recover their inhibition performance, and emphasizes the necessity in systematically considering the oil composition when attempting to develop and utilize KHIs in oil-water system.

Dynamics and miscible behaviors of hydrocarbon gas and crude oil in nanoslits: Effects of light gas type and crude oil components

It is of importance to uncovering miscible behavior of hydrocarbon gas and crude oil in nanoslits for enhanced oil recovery. The comprehensive MD simulations are performed to investigate the miscible process of different hydrocarbon gas and crude oil in nanoslits under reservoir conditions. For the first time, absolute solubility of crude oil is calculated to estimate its miscibility with gas phase. The simulation results manifest that a longer chain length of hydrocarbon gas could help to increase its miscibility with crude oil due to the increasing interaction strength between them. Additionally, the miscibility of hydrocarbon gas and crude oil is reduced due to the increasing polarity of crude oil. Because the larger polarity could strengthen the interactions between crude oil and rock surface and then correspondingly reduce its solubility of crude oil in hydrocarbon gas. This investigation introduces a novel method to evaluate of miscibility of fluids in naoslits and contributes to more general applications of hydrocarbon flooding in reservoirs.

Impact of in-situ gas liberation for enhanced oil recovery and CO2 storage in liquid-rich shale reservoirs

ABSTRACT Carbon dioxide injection in shale reservoirs can be beneficial for enhanced oil recovery and CO2 storage scenarios. CO2 mass transfer can be influenced strongly by the in-situ liberation of light oil components from live oil forming a distinct gas phase. This mechanism has been overlooked in the past for studying CO2 and oil interactions in tight formations. In this work, a series of analytical solutions and numerical simulations were developed to identify the effect on EOR by CO2 due to the liberation of a light hydrocarbon gas phase from live oil in shales. The analytical model demonstrated faster diffusion of CO2 in the two-phase system due to the presence of this gas phase. Using numerical approaches, laboratory-scale simulations indicated that in-situ gas formation can increase oil recovery by 35%. At the field-scale, an additional oil recovery of 9.8% could be attained. Also, the CO2 storage capacity of shale formations could be significantly enhanced due to capillary trapping of CO2 in the liberated gas. The results of this study could potentially be used to improve evaluations of the potential of CO2 EOR in shale reservoirs.

Experimental study on thermal cracking reactions of ultra-heavy oils during air injection assisted in-situ upgrading process

In-situ upgrading (ISU) via down-hole heating can be an effective technique for exploitation of heavy oil reservoirs. In order to increase the heat transfer rate and reservoir energy, air or gas injection assisted in-situ upgrading process (AAISU) has been proposed. In the AAISU process, and also in the traditional in-situ combustion (ISC) process, complex thermal cracking reactions of heavy oils occur along with low temperature oxidation (LTO) in the presence of air or oxygen at high pressure conditions. In comparison with the conventional oil cracking or pyrolysis in refinery (without or with less oxygen), it has been concerned that low temperature oxidation of oil components during air injection may have some impacts on their cracking reactions. In this study, thermal cracking experiments of ultra-heavy oils in small batch reactor as well as thermogravimetry analysis (TGA) experiments have been conducted under high pressure in the presence of air and nitrogen to simulate the AAISU process. The starting temperature for cracking, the products of cracking reactions, reaction rate, and the influence of temperature and pressure on reaction kinetics have been investigated in order to reveal the influence of LTO on cracking reaction and to clarify the confusions. The experimental results demonstrated that the presence of air has some kind negative effect on the cracking of oils compared with that in the presence of nitrogen. For a typical ultra-heavy oil, the minimum starting temperature for cracking is around 350 °C in the presence of air at 3.2 MPa for a reaction time of over 30 days, while the starting temperature is around 325 °C when nitrogen is present. Less light oil components produced and lower cracking reaction rate (about 20–30%) were observed when air was present in comparison with that of nitrogen at the same pressure. That means higher activation energy is required to activate the thermal cracking reaction of oils when air or LTO reactions are involved.

Catalytic hydrothermal liquefaction of Spirulina over bifunctional catalyst to produce high-quality biofuel

In this study, five different bifunctional catalysts (NiO/SAPO-34, NiO/ZSM-5, NiO/USY, NiO/γ-Al2O3 and NiO/SiO2) are characterized and applied for the hydrothermal liquefaction (HTL) of Spirulina to produce biofuel. The X-ray diffraction (XRD), ammonia desorption measurement (NH3-TPD) and Brunauer-Emmet-Teller (BET) analysis results show that NiO/SAPO-34 and NiO/USY catalysts have the better physical properties compared to the other three catalysts, resulting in the higher bio-oil yields of 59.85 wt% and 59.12 wt%, respectively. Then the bio-oil samples are characterized by elemental analysis, Gas Chromatography-Mass Spectrometry (GC–MS) and Thermo-gravimetric analysis (TGA). Results indicate that the bio-oil obtained over NiO/USY catalyst has the highest higher heating value (HHV) due to the higher C and H content as well as the lower O and N content. What’s more, it contains the most hydrocarbons (20.58%) and light oil components (72.91%) with NiO/USY catalyst. Consequently, NiO/USY is considered to be the best bifunctional catalyst for the HTL of Spirulina.

Analysis of the role of the isolation ball in the process of pushing the water from the oil pipeline with complex terrain

To explore the influence of the isolation ball in a crude oil pipeline running over complex terrain, a “U” undulating crude oil pipeline with a large drop was taken as a practical case (the maximum elevation difference was 1490 m). Based on the OLGA multiphase flow transient simulation method, this paper conducts a simulation study on the process of pushing water in a large drop crude oil pipe section. The effect of oil–water interface pig (isolation ball) in the process of pushing water from crude oil and the influence of key parameters such as isolation ball diameter were analyzed. the movement characteristics of the pig in the large-drop sections under the conditions of various throughputs and fluid volumes were studied and determined the maximum velocity, pressure, fluid-holding rate, travel distance, and slug behavior of the pig at various low points. The results show that in the selected pipe section, when the throughput was 900 m3/h to 2500 m3/h, the presence of the isolation ball reduced the mixture of oil and water by 84.2% to 93.7%, reduced the volume of gas generated by the vaporization of the light oil components during transport, and reduced the slug flow in the pipe, providing an effective basis for designing optimal conditions for crude oil pipeline transport.