Cracking Of Oil Research Articles

Differential evolution of pore fluid pressure in the Sinian carbonate reservoirs of the central and eastern Sichuan Basin, China: Implication for gas preservation and destruction

Trillions of cubic meters of gas reserve have been found in the Sinian Dengying carbonate reservoirs with normal pressure in the central Sichuan Basin, while no industrial gas reservoir have been detected in the Sinian Dengying reservoir with normal pressure in the eastern Sichuan Basin. The pore fluid pressure of gas reservoir is usually closely related to total gas content. To investigate the pore fluid pressure evolution and its implication for gas reserve preservation in the Sinian Dengying reservoir of the central and eastern Sichuan Basin, we conducted a comprehensive analysis including fluid inclusion petrography, microthermometry and Raman spectroscopy. The timings of gas inclusions captured in the central and eastern Sichuan Basin occurred from 175 to 92 Ma and 191 to 183 Ma, respectively. The presence of two‐phase vapour‐solid bitumen inclusions with similar phase proportions in a single fluid inclusion assemblage of fluorite provides direct evidence of in situ oil cracking to gas. The widespread solid bitumen from the Sinian Dengying reservoir in the central Sichuan Basin indicates the existence of massive oil cracking, which results in the formation of overpressure in the reservoir. Pore fluid pressure evolution of the Sinian Dengying reservoir of the central Sichuan Basin experiences normal pressure stage (200–155 Ma), overpressure development stage (155–90 Ma) and overpressure release stage (90–0 Ma). The maximum pore fluid pressure and its corresponding pressure coefficient of the Sinian Dengying reservoir of the central Sichuan Basin are approximately 141.4 MPa and 1.95, respectively. The overpressure development stage reflects the processes of oil cracking and gas accumulation, and the overpressure release stage reflects the dissipation of some natural gas in the Sinian Dengying reservoir of the central Sichuan Basin. The pore fluid pressure of the Sinian Dengying reservoir in the eastern Sichuan Basin has maintained at normal pressure since 200 Ma, indicating that the gas reservoir was small during the oil cracking stage and natural gas completely leaked due to tectonic uplift.

Formation mechanism of Gulong shale oil: Insights from semiclosed hydrous pyrolysis

As a typical lacustrine shale oil, Gulong shale oil has enormous resource potential. The current lack of understanding regarding the formation process of this oil has affected its development. This study uses a low-mature shale sample from the first member of the Qingshankou Formation in the Songliao Basin and analyzes the hydrocarbon generation, expulsion, and retention characteristics by conducting hydrous pyrolysis in a semiclosed system. The results show that the formation process of the Gulong shale oil can be divided into three stages. The slow hydrocarbon generation stage occurs when organic matter maturity (Ro) < 0.8 %, and only a small amount of hydrocarbons is generated by kerogen cracking. The products are mainly heavy components (C15+), with retained oil composing the majority of them. The rapid oil generation stage occurs when Ro is of 0.8 %–1.1 %, where a large amount of kerogen is cracked to generate hydrocarbons and reaches its peak when Ro is 1.1 %. Most of generated light component oil (C6–C14) is expelled, and retained oil is mostly composed of heavy components (C15+); Ro > 1.1 % indicates the stage of oil cracking and rapid gas generation. Light component oil (C6–C14) and gaseous hydrocarbons (C1–C5) are formed when heavy components oil (C15+) begins to crack. The light-to-heavy ratio of the hydrocarbon products (C1–C14/C15+) rapidly increases with maturity. The hydrous pyrolysis experiment in a semiclosed system is more in line with actual geological conditions of Qingshankou Formation compared to other experimental systems and can simultaneously consider the influence of geological factors such as temperature, pressure, hydrocarbon expulsion, and formation water.

Properties of biochars derived from different straw at 500℃ pyrolytic temperature: Implications for their use to improving acidic soil water retention

Climate change cause extreme weather effects with temperature increases and drops in humidity, such as drought and heatwaves, which will lead to more evaporation in arid and semi-arid lands. The application of biochar made from crop straw without burning to farmland can effectively improve the water retention capacity of soil. A testing program has been carried out in a climate simulation laboratory to study the effects of different straw biochars on the cracking and evaporation of soils due to drying. Biochar from wheat straw (WS), corn straw (CS) and rice straw (RS) is produced at a pyrolysis temperature of 500℃. Thermogravimetric analysis and elemental analysis are carried out to obtain the properties of the biochar. Five percent of WS, CS and RS biochar by weight is added to acidic soil. Digital camera and digital image processing technology are used to analyze the crack morphology of the samples during evaporation. The results indicate that the RS biochar has the highest ash content (32.5 %), CS biochar has the highest content of volatile solid (25.36 %) and WS biochar has the highest content of fixed carbon (55.38 %). Biochar can effectively improve the water retention capacity of soil. The final water contents of the WS, CS and RS biochar soil samples are 132.3 %, 101.0 %, and 20.7 % respectively higher than that of the soil without biochar. Moreover, biochar can effectively reduce the degree of soil cracking. The addition of WS, CS and RS biochar can reduce soil cracking by 9.21 %, 16.57 %, and 7.46 %, respectively. WS contains more total cellulose than CS and RS, so WS biochar is the best choice to improve soil water retention ability. Therefore, biochar technology helps to optimize soil water retention while avoiding environmental pollution from straw burning.

Pyrolytic hydrocarbon generation characteristics of the Chang 7 shale based on different experimental methods: Implications for shale oil and gas in the Ordos Basin

Shale oil and gas resources are abundant in the Chang 7 shale of the Yanchang Formation in Ordos Basin. To determine the characteristics and influencing factors of hydrocarbon generation evolution of the Chang 7 shale, a series of thermal simulation experiments were conducted on low‐maturity shale and kerogen samples. The results indicate that the maximum yield of shale oil are 294.5 and 304.3 mg/g TOC for kerogen sample at heating rates of 20 and 2°C/h, and the corresponding experimental temperatures are 360.2°C and 408.0°C, respectively. The utilization of lower heating rates is favourable for shale oil generation and it is recommended to employ a lower heating rate during in situ heating processes to maximize the economic benefits. The formation of crude oil cracking gas begins when simulating temperature exceeds 528.0°C (Easy Ro 2.6%) at a heating rate of 20°C/h and 480.0°C (Easy Ro 2.5%) at a heating rate of 2°C/h, as indicated by the carbon isotopic composition of gaseous hydrocarbons. The maximum oil production rate of the rock powder sample is 159.8 mg/g TOC, which is lower than that of the kerogen sample. It suggests that certain minerals in the Chang 7 shale may impede hydrocarbon generation. After the addition of pyrite, the highest yield of shale oil is 213.96 mg/g TOC, 33.9% higher than the yield of the original rock powder sample, reflecting the positive catalytic effect of pyrite on hydrocarbon generation of Chang 7 shale. Under geologic conditions, pyrite catalytic hydrocarbon generation may act primarily on the migration of organic matter by macromolecules, which considerably increases the probability of direct contact between pyrite and organic matter. Therefore, the organic‐rich shale with high pyrite content in Chang 7 member is the preferred target for in situ conversion of shale oil and gas in the Ordos Basin.

Dynamic evolution of three-dimensional cracks in expansive soil under wet-dry cycles: insights from resistivity monitoring

Dynamic evolution of three-dimensional cracks in expansive soil under wet-dry cycles: insights from resistivity monitoring

Investigation of Desiccation Cracking Behavior of Waste Carbon Fiber–Reinforced Clay Material

Carbon fiber is a common waste building material, but its effect on the drying and cracking properties of clay materials is unknown. In this paper, crack rate and fractal dimension are used to characterize the influence of waste carbon fiber materials on the development of soil cracking. With the rise in carbon fiber content to 0.2%, 0.4% and 0.6%, the crack rate of soil cracking decreased by 7.9%, 17.3% and 23.3%, respectively, while the fractal dimension of soil cracking decreased by 2.4%, 8.7% and 21.2%, respectively. Accordingly, the critical moisture content of the soil samples increased by 33.2%, 110% and 151%, and the time of the soil constant evaporation stage decreased by 5.1%, 13.8% and 34.5%, respectively. When carbon fiber is combined with soil, carbon fiber will increase the interface bonding strength, friction and interlocking force, effectively inhibiting the cracking of soil, and it provides a channel for water transport in the soil in the early stage.

Investigation of the Shear and Pore Structure Characteristics of Rubber Fiber-Reinforced Expansive Soil

In recent years, many researchers have evaluated the sustainable use of waste tire rubber as an aggregate in soil. Its effectiveness has been widely acknowledged. The main objective of this work is to study the influence of rubber fibers on shear strength and pore structure characteristics in relation to expansive soil. In this context, we conducted a series of experiments that were carried out on reinforced expansive soil with rubber fiber contents of 0, 5, 10, 15, and 20%. The results show that the shear strength and maximum dilatation angle increase gradually with rubber fiber content. Due to the pore water pressure and creep effects, the deviator stress and effective cohesion of the samples under the consolidated drained conditions were higher than those under the undrained conditions. The converse was true for the internal angle. The addition of an appropriate amount of (5–10%) rubber fiber can effectively inhibit the development of soil cracks and reduce the porosity of the samples. The results obtained can highlight the beneficial effects of rubber fiber, which is highly desirable in many backfill applications.

Model test study of bridge pile horizontal bearing behavior under landslide deformation

Pile is a common foundation on the slope, which poses a serious threat to the construction and operation if the slope deformation and causes landslide. In this study, a model device of pile foundation on landslide was independently developed by relative displacement loading between pile and soil to explore the influence of landslide deformation on pile and analysis the soil failure rule and the deformation characteristics of pile in different stages of landslide deformation, a few model tests were completed including the relative displacement between soil and pile from 1 to 17 cm, and the pile diameter and the modulus of slide bed were also considered. The results indicated that: the evolution process of landslide deformation with pile foundation on could be divided into four stages including soil compaction, cracks growth, yield stage, and failure stage; ratios of the maximum soil pressure and bending moment growth from the soil compaction stage to the cracks growth stage to the total growth in these four stages are both exceeding 60%; the soil pressure increases with the increase of pile diameter and sliding bed modulus. Therefore, it is best to effectively monitor and control the landslide in the initial soil compression stage that in soil compaction stage and methods such as increasing pile foundations or reinforcing the sliding bed can be used for protection.

Utilization of waste tires in the process of thermal cracking of vacuum gas oil

The process of thermal cracking of vacuum gas oil (VGO) with the addition of 10% tire crumb at a temperature of 500 °C and feed rate of 1 h- ¹ was studied. In the course of the study experiments were carried out, which showed that the introduction of tire crumb into the composition of VG promotes the acceleration of conversion of the heavy fraction of VG. Addition of 10% of tire crumb has a positive effect on the cracking process, which is expressed in the increase in the yield of diesel fraction by weight by 2%. Analysis of the material balance of the thermal cracking process of crushed tire crumb shows that under these conditions tire crumb was poorly subjected to thermal transformation. The yield of gasoline fraction and light gas oil fraction in the catalyst composition was only 1% and 7.4% by weight, respectively. The conversion of tire crumb into light fractions including gas oil reached 20.5%. Addition of 10% by weight of tire crumb to the composition of vacuum gas oil increases the yield of gasoline and diesel fractions (light gas oil fractions), while reducing the amount of heavy gas oil. The increase in the yield of diesel fraction is 4% by weight, and the total conversion of blended feedstock reaches 59.5%. Thus, the addition of tire crumb to the composition of vacuum gas oil practically does not affect the total conversion, but increases the yield of light gas oil. This allows us to conclude that the introduction of tire crumb contributes to a more efficient conversion of heavy fractions of vacuum gas oil. After hydrotreating process the obtained diesel and gasoline fractions can be successfully used as components of automotive fuels. Thus, the addition of tire crumb to the thermal cracking process of vacuum gas oil not only improves the conversion of heavy fractions, but also increases the yield of valuable products such as diesel fuel, which is important for the refining industry.

Steam catalytic cracking of vacuum gas oil: Effect of co-feeding naphtha or gas condensate on light olefins yield

Herein, we have investigated the steam catalytic cracking of heavy VGO (HVGO) blends with naphtha (NAPH) and gas condensates (GCON) in a microflow fixed-bed reactor using synthesized nano-ZSM-5 catalyst for increased light olefins yield. The co-feeding of HVGO with NAPH in the steam cracking reaction increased HVGO conversion from 38.2 % to 65.3 %, and slightly decreased the coke yield. Ethylene and propylene yield increased from 10.2 % and 9. 8 % in HVGO to 15.0 % and 13.4 % in the HVGO+20 %NAPH respectively. The co-feeding of HVGO with GCON in the steam cracking reaction increased HVGO conversion from 38.2 % to 47.5 %, however, lower yield of light olefins was recorded. The catalytic cracking of HVGO with NAPH over synthesized nano-ZSM-5 zeolite resulted in higher conversion and light olefins yield. This has been ascribed to the available acid sites and shape selectivity of the nano-zeolite that favors high yield of light olefins. The HVGO+20 %GCON conversion increased to 68.6 % during catalytic cracking over nano-ZSM-5 zeolite, and the light olefins increased from 33.2 % to 41.1 %. The effect of steam/oil ratio on the catalytic cracking reactions of HVGO+20 %NAPH and HVGO+20 %GCON for steam/oil ratio 0–2 showed that higher conversion and light olefins yield were achieved at the steam/oil ratio of 2.

Enhancing Agricultural Efficiency: Deep Learning-Based Soil Crack Detection for Water Irrigation

The escalating demand for agricultural precision and environmental monitoring underscores the necessity for effective soil crack detection methods. This study explores the feasibility of employing a Raspberry Pi-powered camera system and deep learning image recognition to detect soil cracks and control agricultural irrigation. The purpose is to develop a soil crack detection system using deep learning techniques, sustain plant growth process, increase productivity, and optimize water irrigation practice. Our approach leverages TensorFlow to craft a convolutional neural network tailored specifically for execution on a Raspberry Pi 3B+. A dataset comprises manually captured images and is trained with the InceptionV3 model categorized into crack or nocrack classes. The accuracy is achieved ranging from 97% to 99%. These results underscore deep learning image recognition models on Raspberry Pi for cost-effective soil crack monitoring and controlling the plants watering system.

Geochemistry and accumulation of the ultra-deep Ordovician oils in the Shunbei oilfield, Tarim Basin: Coupling of reservoir secondary processes and filling events

Ultra-deep (7300 m–8900 m) condensed and volatile oil reservoirs have been discovered in the Ordovician reservoirs of the Shunbei oilfield, in the Tarim Basin. This study describes the petroleum accumulation process in the Shunbei oilfield by combining an analysis of its geochemical characteristics with seismic section observations and an analysis of petroleum filling events. Geochemical techniques are used to determine the sources, maturity, secondary processes, accumulation periods, and timing of petroleum filling. Analysis of fluid inclusion homogenization temperatures and burial-thermal histories indicates distinct petroleum filling events. Specifically, the north sub-section of the No. 5 fault zone experienced two petroleum filling periods during the late Caledonian and Indosinian epochs while the No. 1 fault zones and the mid-south sub-sections of the No. 5 fault zones experienced three distinct filling periods, encompassing the late Caledonian, Indosinian, and Himalayan periods. The CO2 concentrations and δ13CCO2 values suggest the presence of secondary microbial gases, primarily thermogenic gases. Gas component analysis reveals a transition from kerogen degradation gas to oil cracking gas from north to south. The detection of intact n-alkanes and compounds of the 25-norhopanes series in oil samples suggests a mixture of early biodegradable oil with late fresh oil in the area. Seismic sections reveal diabase intrusions with strong axial reflections. Local hydrothermal activities during the Permian era rapidly cracked saturated hydrocarbon biomarkers, forming polycyclic aromatic hydrocarbons in the oil. Hydrothermal activity in the south sub-section of the No. 5 fault zone depleted the hydrocarbon-generating capacity of the underlying source rocks. Petroleum charged during the Indosinian period likely originated from potential petroleum reservoirs in the Cambrian system. This explains the comparatively low temperature of the SHB57X reservoir (163.32 °C) and the lack of strong hydrothermal activity in the late stage, but no biomarkers of the second-stage charged oil have been detected. Biomarker detection and gas genesis in the mid-south sub-section of the No. 5 fault zone and in the No. 1 fault zone suggest weak or no hydrothermal activity, with Cambrian source rocks maintaining their hydrocarbon generation capacity. Gas filling in the Himalayan period caused evaporative fractionation in the original reservoirs, resulting in a disproportionate (2-MH+2,3-DMP)/(3-MH+2,4-DMP), producing high K1 values in the light hydrocarbons in the present petroleum reservoirs. Differences in gas charging events in the Himalayan period led to the present distribution of petroleum phases.

Electroosmotic strengthening of soft clay under different electrification modes

AbstractElectrification mode is one of the important factors affecting the energy consumption and drainage effect of the electroosmosis method. In this work, a series of laboratory tests were performed to explore the impact of continuous changes in the electric field on the migration of ions and electrons, as well as the migration of electroosmotic flow. The results show that different electrification modes had a significant impact on the current and water discharge. An electrode reversed from anode to cathode, from one circuit to another, is beneficial to drainage, while an electrode reversed from cathode to anode, from one circuit to another, is unfavorable to drainage. The drainage effect of the specific cyclic and progressive electroosmosis (CPE) is not as good as the conventional electroosmosis method. However, combining the two electrification modes can further enhance the shear strength of the soil near a designated electrode. The generation of transverse cracks in soil is mainly due to the drainage difference caused by the electroosmotic flow, which is caused by the adjacent electric field at that location. When the electroosmotic flow is strong, longitudinal cracks will occur in the soil along the strongest electroosmotic flow path. In practical in situ engineering applications, the electrification mode of CPE will be more energy‐efficient than conventional electrification modes with the same processing time.

The role of soil structure on the cracking and cadmium leaching behavior of biochar-amended fine-grained soils

Biochar has shown promising potential for soil remediation, yet its impact on heavy metals (HMs) immobilization often overlooks soil structure, which could influence soil cracking behavior and HMs transport. To address this gap, this study investigates the role of soil structure (dry density and aggregate size) on the cracking and cadmium (Cd) leaching behavior of biochar-amended fine-grained soils. A series of semi-dynamic leaching tests were conducted on samples with and without wetting-drying (W-D) cycles. Based on the proposed improved method for quantifying the effective diffusion coefficient (De) of Cd in unsaturated soils and microstructural analyses, we found that: (1) Higher dry density and larger aggregate generally resulted in smaller De by decreasing soil pore volume. (2) Biochar could connect isolated pores within large aggregates through its internal pores, yielding greater increases in De (294.8%–469.0%) compared to small aggregates (29.1%–77.4%) with 3% biochar. However, further increases in biochar dosage led to decreased De, primarily due to the dense pore structure. (3) Biochar effectively inhibited soil cracking, achieving the highest reduction of 36.8% in surface crack ratio. (4) After W-D cycles, samples exhibited higher De with increasing dry density, with aggravated cracking being the primary cause, suggesting preferential flow within the cracks, particularly those penetrating the soil. This study highlights the importance of careful consideration of soil structure and cracking potential before in situ field application of biochar as a remediation agent for HMs-contaminated fine-grained soils.

Characterization and impact of oxygenates in post-consumer plastic waste-derived pyrolysis oils on steam cracking process efficiency

Mechanical recycling of mixed packaging waste has limitations due to challenging separation into pure polyolefin streams which often leads to low quality recyclates. A solution to improve overall recycling rates of polyolefins is chemical recycling. One promising approach is conversion into a liquid product via pyrolysis and subsequent steam cracking of the pyrolysis oil towards light olefins. In this study, distilled fractions of pyrolysis oils from PE and PP-rich waste were characterized via GC × GC including normal and reversed-phase column configurations with a special focus on oxygenated components. Distilled pyrolysis oils were subsequently steam cracked in 20/80 weight‐based blends with conventional naphtha. All pyrolysis oil samples contained substantial amounts of oxygenates (1–10 wt%) which poses a huge challenge for steam cracker feedstocks and it was found that ketones are the most prevailing oxygenate group. Steam cracking experiments showed slightly increased ethylene yields of the blends compared to pure fossil naphtha, with the PE-derived samples outperforming the PP-derived samples. Furthermore, diesel-range distillation cuts led to higher formation of heavy products compared to the naphtha-range cuts. Increased formation of CO was observed as a consequence of the substantial oxygen contamination which can be a deal-breaker in industrial steam crackers. This work shows that distilled pyrolysis oils with conventional naphtha are promising steam cracking feedstocks if intermediate processing steps are performed to remove the oxygenates and other impurities using, for instance, hydrotreatment. With the findings of this work, such upgrading processes can be designed in a more effective way.

Geochemistry of oils and condensates from the lower Eagle Ford formation, south Texas. Part 6: Carbon isotopes

Compound specific carbon isotope analyses were performed on a well-characterized suite of unconventional oils and condensates produced from the lower Eagle Ford Formation. Thermal maturity is the major influence on the δ13C values of C3–C19 hydrocarbons. From ∼0.8 to ∼1.1 %Ro, the main stage of oil generation, the δ13C values of most measured hydrocarbons remain relatively constant: n-alkanes are ∼ −30 ‰: light aromatic hydrocarbons, cycloalkanes and isoprenoids are ∼ −29 to −28 ‰. Only the C4 to C10 methylalkanes exhibit high variance with carbon number with δ13C values ranging from ∼ −32 to −28 ‰, respectively. Hydrocarbons from samples ∼1.1 to 1.3 %Ro, the late oil generation stage, are 13C-enriched by ∼1–∼2 ‰. This is the range typically assigned to the influence of thermal maturity on oil from many conventional petroleum systems. The onset of significant oil cracking occurs at ∼1.3 %Ro and all measured hydrocarbons systematically become progressively 13C-enriched although the degree varies by compound class and carbon number. The δ13C values of individual hydrocarbons shift by as much as ∼ +9 ‰ for propane and butane to only ∼ +3 ‰ for methylcyclopentane from <1.1 to 1.7 %Ro. The 13C-enrichments observed in the Eagle Ford oils/condensates with increasing maturity are attributed to the kinetic isotope effect (KIE), whereby 12C–12C bonds cleave faster than 12C–13C bonds. No evidence for isotopic equilibrium was found. The consistency of the sums of the weighted δ13C values for C4–C7n-alkane/methylalkane isomers provides support for Mango's (2000a) theory that these hydrocarbons are generated from precursors with a common chemical structure that pass through a similar transition state.Source facies exert only a minor influence on the carbon isotopic composition of Eagle Ford oils/condensates. Small variances in the 13C values of C6+n-alkanes, cyclohexane and methylcyclohexane are consistent with oils produced east of the San Marco Arch being generated from shales with a higher influx of terrestrial high plant matter compared to the shales west of the Arch. Phase fractionation was shown to have a measurable impact on the δ13C values of the most volatile hydrocarbons in evaporated samples and on the least volatile hydrocarbon that underwent phase separation in the subsurface during production.

A Nanocrystalline ZSM‐5 for the Catalytic Cracking of Waste Cooking Oil

AbstractA series of hierarchical ZSM‐5 nanocrystalline aggregates (HNZ‐5) was synthesized using a hydrothermal method with tetrapropylammonium hydroxide as a structural guide. The HNZ‐5 samples having different Si/Al molar ratios all showed suitable hierarchical architectures and the maximum surface area was found to be 329 m2/g. The SEM image displayed the width of the individual crystal particles was ~100 nm, and its nanocrystalline clusters generated intercrystalline pores. Temperature‐programmed desorption with NH3 indicated that the total acidity of this material increased with increases in the Al3+ content to a maximum of 0.47 mmol/g at a Si/Al ratio of 15. In addition, 27Al magic angle spinning nuclear magnetic resonance spectra showed that the acid sites were associated with tetrahedral and octahedral Al sites. This HNZ‐5 was applied to the catalytic cracking of waste cooking oil model compound and gave a light olefin yield as high as 43.9 % at 550 °C. Extending the reaction time to 6000 min provided a yield of light olefins in excess of 30 %, which was higher than that achieved using traditional ZSM‐5. These data confirmed that the hierarchical pore structure of HNZ‐5 resulting from the self‐assembly of nanocrystals, together with exposed acidic sites, promoted the catalytic conversion of large molecules.

Monolithic HZSM-5/SS-fiber catalysts with high coke-resistance and selectivity for catalytic cracking of castor oil to produce biofuel

Monolithic HZSM-5/SS-fiber catalysts with hierarchical porous structure from micro-to macro-size for catalytic cracking of castor oil to produce biofuel were fabricated by seed coating and subsequent hydrothermal synthesis of ZSM-5 zeolite crystals onto the thin-sheet stainless steel fiber (SS-fiber). Compared with the powdered HZSM-5, the HZSM-5/SS-fiber catalyst exhibited high hydrocarbon selectivity (78% in gasoline and 57% in diesel) with enhanced physical properties of liquid products, as well as excellent coke-resistance with coking rate of 0.47 mg gzeolite−1 h−1 (one-eighth of the powdered HZSM-5), indicating a significant intensification on cracking process due to a unique combination of high heat/mass transfer and hierarchical pore structure. SiO2/Al2O3 ratio exerts a pivotal influence on HZSM-5 loading and acid strength/amount of the HZSM-5/SS-fiber, which thereby strongly relates to the degree of cracking, aromatization, and deoxygenation. The HZSM-5/SS-fiber (200) with moderate acid amount and strength permitted mild secondary cracking and sufficient deoxygenation reactions, resulting in a low coke yield, a high liquid product yield and a high hydrocarbon/aromatic selectivity along with reduced acid values (7.4 mg KOH g−1 in gasoline and 83.2 mg KOH g−1 in diesel). The physical properties including kinematic viscosity, density, oxygen content and heating value, were optimal at SiO2/Al2O3 ratio of 200.

Synergistic biocementation: harnessing Comamonas and Bacillus ureolytic bacteria for enhanced sand stabilization

Biocementation, driven by ureolytic bacteria and their biochemical activities, has evolved as a powerful technology for soil stabilization, crack repair, and bioremediation. Ureolytic bacteria play a crucial role in calcium carbonate precipitation through their enzymatic activity, hydrolyzing urea to produce carbonate ions and elevate pH, thus creating favorable conditions for the precipitation of calcium carbonate. While extensive research has explored the ability of ureolytic bacteria isolated from natural environments or culture conditions, bacterial synergy is often unexplored or under-reported. In this study, we isolated bacterial strains from the local eutrophic river canal and evaluated their suitability for precipitating calcium carbonate polymorphs. We identified two distinct bacterial isolates with superior urea degradation ability (conductivity method) using partial 16 S rRNA gene sequencing. Molecular identification revealed that they belong to the Comamonas and Bacillus genera. Urea degradation analysis was performed under diverse pH (6,7 and 8) and temperature (15 °C,20 °C,25 °C and 30 °C) ranges, indicating that their ideal pH is 7 and temperature is 30 °C since 95% of the urea was degraded within 96 h. In addition, we investigated these strains individually and in combination, assessing their microbially induced carbonate precipitation (MICP) in silicate fine sand under low (14 ± 0.6 °C) and ideal temperature 30 °C conditions, aiming to optimize bio-mediated soil enhancement. Results indicated that 30 °C was the ideal temperature, and combining bacteria resulted in significant (p ≤ 0.001) superior carbonate precipitation (14–16%) and permeability (> 10− 6 m/s) in comparison to the average range of individual strains. These findings provide valuable insights into the potential of combining ureolytic bacteria for future MICP research on field applications including soil erosion mitigation, soil stabilization, ground improvement, and heavy metal remediation.

Oil cracking under closed-system pyrolysis: Implications for deep oil occurrence and related source determination

The cracking and stability of liquid oil is of critical importance in the exploration of deep petroleum accumulations. Numerous studies have been conducted on oils to investigate the cracking process. However, limited research has been directed to the cracking of oil with different maturities. Here, gold tube pyrolysis experiments were conducted on lower maturity normal oil (LMO) and higher maturity condensates (HMC) samples to investigate the compositions of pyrolysis products and to estimate the stability of oil during continuous deep burial. The results indicated that oil cracking can be generally divided into two stages, namely light oil generation stage and gas generation, with a maturity boundary approximately EasyRo ∼1.5%. Most of oil cracking gas was generated at EasyRo ∼2.4 %, with maximum mass yield of C1-5 is 553.8 mg/g and 609.4 mg/g for LMO and HMC, respectively. The difference in gas yields between HMC and LMO indicates the higher gas potential during the cracking of light oil components. An obvious increase in the C19/C23 tricyclic parameters was observed with enhanced thermal maturity, which indicates the interpretation of tricyclic parameters of high mature oils should be made with caution. Although high maturity also influenced the ratios of gammacerane/αβ C30 hopane (G/H) and 4-methylsteranes/C29 steranes (4MSI), the altered corresponding values still fall within the suggested discriminating zones for the Dongying and Shahejie Formation source rocks. Thus, the G/H and 4MSI parameters can be utilized to characterize the high mature oil with Ro <1.3% in the Bohai Bay Basin (BBB) or other basins. The calculated activation energy of C1-5 generation for LMO displays a more discrete and lower distribution compared to the HMC, which may indicate relatively lower stability heavy hydrocarbons in LMO. Based on previous studies of petroleum charge, the kinetics of C1-5 generation of LMO were extrapolated to geological conditions, yielding a maximum depth of 5750 m for the occurrence of liquid oil in the BBB. This study underscores the high thermal stability of light oil fractions, which indicates that deep high mature oils may represent the preservation of directly charged light oil or the transformation by in-reservoir cracking of normal oil associated with continuous burial.