Residual Oil Research Articles

Particle Size and Morphological Evaluation of Airborne Urban Dust Particles by Scanning Electron Microscopy and Bidimensional Empirical Mode Analysis

Airborne particles affect the health of the population. As particles decrease in size, they can penetrate deeper into the respiratory system, reaching the terminal bronchioles and alveoli. Particles as small as 0.1 µm in diameter may translocate into the bloodstream, potentially impacting various organs. Additionally, the smaller the particle size, the longer they remain suspended in the air, thereby increasing their deleterious damages. The aim of this work is to study the size distribution of airborne particles emitted from anthropogenic sources of air pollution, with a special emphasis on estimating the distribution of micro and nanoparticles considered the most harmful to health. The Bidimensional Empirical Mode Decomposition (BEMD) algorithm was used on micrographs of the particles obtained by Scanning Electron Microscopy (SEM). BEMD is a current empirical computational tool applied to image analysis that allows extracting non-linear heterogeneous oscillations of brightness. We studied ROFA (Residual Oil Fly Ash) from industrial sources and DEP (Diesel Exhaust Particles) from vehicular emissions as airborne particles. After collecting the particles on filters, micrographs were taken using SEM at different magnifications to which the BEMD algorithm was applied. Particle size and asymmetry distributions were obtained for each mode, allowing the identification of the most deleterious particles. The methodology employed herein is relatively simple and effective for inferring the impact of airborne particulate matter on health and the environment.

Enhanced Carbon/Oxygen Ratio Logging Interpretation Methods and Applications in Offshore Oilfields

As the development of most domestic and international oilfields progresses, many fields have entered a mature phase characterized by high water cut and high recovery, with water cut levels often exceeding 90%. Carbon/oxygen ratio logging has proven to be an indispensable tool for distinguishing oil layers from water layers in complex environments, especially where salinity is low, unknown, or highly variable. This logging method has become one of the most effective techniques for determining residual oil saturation in cased wells, providing critical insights into the oil–water interface. In this study, we evaluate two key interpretation models for carbon/oxygen ratio logging: the fan chart method and the ratio chart method. We optimize the interpretation parameters in the ratio chart model using an improved genetic algorithm, which significantly enhances interpretation precision. The optimized parameters enable a more seamless integration of logging results with reservoir and conventional logging data, reducing the influence of lithological variations and physical property differences on the measurements. This research establishes a robust theoretical foundation for enhancing the interpretation accuracy of carbon/oxygen ratio logging, which is crucial for effectively identifying water-flooded layers. These advancements provide vital technical support for monitoring oil–water dynamics, optimizing reservoir management, and improving production efficiency in oilfield development.

The Formation Mechanism of Residual Oil and Methods of Enhanced Oil Recovery in a Fractured Low-Permeability Metamorphic Rock Reservoir in Bohai Bay

The oil reservoirs of the metamorphic rocks in Bohai Bay have geological characteristics such as low matrix porosity and permeability, developed natural microfractures, which result in the injection water rapidly advancing along fractures, a fast increase in the water content, and difficulties in extracting the remaining oil. In order to reveal water channeling and the residual oil formation mechanisms in fractured low-permeability reservoirs and solve the water channeling problem, we first analyzed the reservoir development status, then studied the formation mechanism of residual oil using a microfluidic chip device, and formed a method of hierarchical control to effectively control the water channeling problem of fractured reservoirs and maximize the displacement of residual oil. The results show that (1) Due to the low permeability of the reservoir matrix, a large amount of injected water flows along the fracture channel, which leads to the long-term high water cut of some oil wells and the retention of a large amount of crude oil in the matrix. (2) The results of microfluidic experiments show that the distribution of residual oil after water flooding mainly includes five types: blind end of the pore throat, columnar, cluster, flake and film, and residual oil. Among them, sheet-like and clustered residual oil are dominant, accounting for 75~85% and 10~13%, respectively. (3) Based on the characteristics of fracture development in buried-hill reservoirs, a hierarchical control technology of “gel particle + liquid crosslinked gel system” is established. The field application effect predicted that the input–output ratio was 1:3. This study provides a reference for the comprehensive treatment of water channeling in the same type of offshore fractured low-permeability metamorphic rock reservoirs.

Characterization and Inversion Method of Relative Permeability of Emulsion Flooding.

Relative permeability curves are one of the crucial factors that control the behavior of multiphase flow in petroleum reservoirs. Accurate prediction of the relative permeability curve involving emulsification and emulsion transport in emulsion flooding is vital to enhancing heavy oil recovery. In this study, a relative permeability characterization model including the emulsification mechanism and emulsion transport is developed, in which residual oil saturation and end-point permeability for water are parametrized as functions of emulsion concentration and capillary number. Based on the built characterization model, an inversion method (ensemble Kalman filter) is used to estimate the relative permeability curves of emulsion flooding. The inversion results of four sets of emulsion flooding experiments show that the errors of end points between the Johnson-Bossler-Neumann method and inversion method are less than 10%. For the continuous emulsification process in the in situ emulsion flooding tests, the inversed relative permeability curves shift between the upper and the inferior limits of the permeability. The error of residual oil saturation between the inversion and the experiment is less than 10%. In summary, this study demonstrates the feasibility of using the characterization model and inversion method to infer the relative permeability curves of emulsion flooding, which can aid in the predictions of multiphase flow in heavy oil reservoirs.

Methodological approaches to assessing the invasion of process fluids into the core pore space

Background. The reliability of the lithological and petrophysical studies is largely determined by the quality of the core material. The invasion of drilling mud filtrate into the core will primarily affect the measurements of the fluid type, residual oil and water saturation, porosity, permeability, geochemical properties and wettability of the rock. Evaluating the suitability of the core material for laboratory studies is one of the main tasks in the study of low-invasion core. Objective. To determine the most informative methods of penetration of process fluids into the pore space of the rock to assess the suitability of the core for laboratory studies. Materials and methods. The paper uses the methods of lithological and petrophysical research of core and reservoir fluids. Results. The application of the used research methods is analyzed. The advantages and limitations of each of the presented methods are determined. Conclusions. The assessment of the degree of mud filtrate invasion into the core determines the suitability of the core material for further petrophysical research.

Utilization Status of Oil-Based Drilling Cutting Pyrolysis Residues in The Field of Building Materials

The exploitation of shale gas generates a large amount of oil-based drill cuttings, which are harmful to the environment due to their content of petroleum hydrocarbons, heavy metals, and organic pollutants. Thermal desorption technology is one of the main techniques for treating oil-based drill cuttings. This paper focuses on oil-based drilling cutting pyrolysis residues and summarizes its current research status in the construction materials field. Currently, the application of oil-based drilling cutting pyrolysis residues has achieved certain results in road fill, cement production, ceramsite production, and wall materials, and further exploration and development are needed in the future to develop high value-added products and expand the pathways for the high-value utilization of oil residues.

Roles of kaolinite-oil-gas molecular interactions in hydrogen storage within depleted reservoirs

Hydrogen is a clean alternative to fossil fuels, emitting only water vapor during combustion. In a future hydrogen economy, large-scale storage will be an important component of the supply chain. Due to its low volumetric density, conventional surface storage methods are inadequate. Underground hydrogen storage (UHS) offers a viable solution, enabling the storage of millions of cubic meters. Among potential geological sites, including salt caverns, aquifers, and depleted gas reservoirs, depleted oil reservoirs show promise. Studying hydrogen interactions with residual oil and reservoir minerals is vital for understanding the properties of hydrogen and the reservoir post-injection. In this study, we employed molecular dynamics simulations to gain molecular-level insights into these interactions. We investigated hydrogen dissolution in oil, adsorption at kaolinite/oil interfaces, the role of CO2 as a cushion gas, and the influence of kaolinite’s hydrophobicity on H2 behavior. The main findings include: (1) hydrogen dissolves more in oil than in water, (2) the introduction of CO2 suppresses hydrogen dissolution in oil and reduces the interfacial tension (IFT) between oil and gas, (3) CO2 decreases H2 partitioning near kaolinite surfaces due to its strong affinity for the hydrophilic gibbsite surface of kaolinite, and (4) CO2 is more effective than H2 in reducing IFT between kaolinite and the oil–gas mixture. These findings emphasize the effectiveness of CO2 as a cushion gas and the important role of clay hydrophobicity in UHS, providing insights that are challenging to obtain experimentally.

Characteristics of High Molecular Components Obtained by Thermal Destruction of Oil Residue Asphaltenes in Supercritical Water

Characteristics of High Molecular Components Obtained by Thermal Destruction of Oil Residue Asphaltenes in Supercritical Water

Development of a flow diagram for the production of asphalt concrete mixture using polyethylene waste, contaminated with oil products

Large quantities of low-pressure polyethylene containers used for transportation and storage of oil products (motor oils) entail higher environmental risks produced by their utilization or disposal. An urgent scientific task is to search for new ways for utilization of such containers, to involve them in production of new target products without thorough cleaning of waste from contaminants and residues of motor oils. The present study involved crushed containers used for storage and transportation of motor oil in order to explore the possibility of including polyethylene in the production of asphalt concrete mixture. A sample, containing 17.5% of low-pressure polyethylene (contaminated with motor oil by 8% of asphalt mass), and a control sample of asphalt concrete mixture free of polyethylene, were made in order to investigate the change of properties, occurring in the low-pressure polyethylene asphalt concrete. Results. The study assessed main physical and mechanical properties of asphalt concrete samples containing low-pressure polyethylene and motor oil. According to the assessment, a number of properties exceed the values stated in GOST 9128-2013. In addition, the study results included development of technological regulations for producing asphalt concrete mixture with polyethylene as well as the flow diagram for obtaining asphalt concrete mixture. Using polyethylene waste contaminated with motor oil in the production cycle of asphalt concrete mixtures will reduce the consumption of raw materials for asphalt concrete production and the negative impact on the environment.

Enhanced oil recovery and carbon sequestration in low-permeability reservoirs: Comparative analysis of CO2 and oil-based CO2 foam

Excessive CO2 emissions contribute to global climate change thus mandating effective methods for CO2 utilization and sequestering. In this study, one-dimensional flow simulation experiments on CO2 flooding, CO2 Huff-n-Puff, oil-based CO2 foam flooding, and oil-based CO2 foam Huff-n-Puff are conducted using low-permeability sandstone cores modeled after the Q131 block in Liaohe Oilfield, characterized by porosity ranging from 15% to 20% and permeability between 25 mD to 35 mD. Low permeability reservoirs are rich in oil resources and may effectively sequester CO2. Parameters pertaining to oil and gas production and carbon storage are collected. Nuclear magnetic resonance (NMR) is employed to determine the spatial variation of oil saturation in the cores. The experimental results show 8.03% and 41.21% increase in oil recovery factor by foam flooding and foam Huff-n-Puff relative to CO2 as the recovery agent. Moreover, NMR analysis confirms lower residual oil saturation in core samples using foam, suggesting better displacement agent. Oil-based CO2 foam recovery contributed to effective carbon sequestration, with carbon storage increasing by 34.24% and 315% relative to CO2 flooding and CO2 Huff-n-Puff, respectively. CO2 storage mechanisms for oil-based CO2 foam recovery method are detailed.

Characterization of Residual Dispersion in High Water Cut Reservoir

Abstract Minghua Formation in Gangdong Oilfield belongs to high permeability reservoir. The dispersion degree of residual oil is a very important production target. The dominant reserves in reservoirs are extracted by the abundance parameters of residual dominant reserves. The residual oil dispersion degree is characterized by the index of unit area, distribution density and shape index, and the weight of each index is determined by the entropy weight method. Finally, the residual oil fraction is formed. The results show that for a stable reservoir, the residual oil dispersion in different development stages include the following stages: rising, rapid rising, fluctuating downward and secondary rising. The characterization index is used to evaluate the Nm3-4-1 formation of Gangdong oilfield. The residual oil dispersion of the formation increases steadily with the development. At present, the residual oil dispersion begins to decrease. The new characterization method of residual oil dispersion effectively reflects the stage effect of reservoirs and provides a basis for improving oil recovery.

Research and Field Application on Extreme Subdivision Water Injection Technology for Low Permeability Reservoirs

Abstract Low permeability Block A is about to enter the development phase of extremely high water cut. Due to the low overall recovery degree and residual oil scattered sporadically, the efficient development meets more difficulty and conventional residual oil analysis and adjustment methods cannot fulfil the current needs of precise development. To enhance the reservoir utilization degree, we conduct extremely concise zonal water injection experiment from three aspects: sand body description, policies establishment, and proper technique application. In terms of sand body description, four types of sand-body distribution patterns were summarized through fine characterization of vertical, planar, and spatial single sand bodies, clarifying the origin and potential distribution of residual oil. In terms of development policy, numerical simulation and reservoir engineering methods have been comprehensively applied to determine the subdivision combination of injection layers and reasonable water allocation boundaries, and subdivision principles have been established, considering single septation to thin and thick layer with combining enhancing -controlling. In terms of supporting technology, we have studied the small space subdivision process of small compartments, optimized the testing and adjustment methods, and finally achieved accurate separation, strict clamping, and accurate matching of water injection layers. Through the research and practice, it realized the finest septation of the water injection to extremely enhance the subdivision degree and the efficiency of the injection. It also have strengthened the utilization of thin and poor layers and effectively controlled the decline.

Research and Practice on EOR Development Strategy of Water Drive Followed by Gas Drive in Fractured Carbonate Reservoir in Bohai Sea

Abstract Focusing on the issues of high comprehensive water cut and low recovery degree following water flooding in the CFD 2-2 carbonate buried hill reservoir in the Bohai Sea, the productivity variation law, water cut rising characteristics and development effect of horizontal wells were analyzed based on different types of reservoir classification systems. The reservoir numerical simulation model of dual media coupling of matrix and fracture is established, and the analysis is done on the matrix and fracture production state, the distribution pattern of the residual oil, and the primary governing parameters.. The physical simulation experiment of water flooding to gas flooding is carried out. In conjunction with the distribution characteristics of fractures and matrix residual oil in low, middle and upper tiers of the framework, the development strategy of nitrogen injection pressure water cone in low water-flooded area, nitrogen flooding in middle inter-well residual oil enrichment area and nitrogen huff and puff in high well point residual oil enrichment area is put forward. The recovery rate is increased by 5-8 %, which successfully enhances the high water cut stage development effect, and provides reference for similar oilfield development.

Waste to Energy; Conversion of Plastic Waste into Liquid Fuel Equivalent to Diesel and Gasoline Using the Pyrolysis Method

Abstract The aim of this research is to produce oil equivalent to diesel and gasoline from plastic waste using the pyrolysis method, examining its physico-chemical properties and comparing it with conventional diesel and gasoline. The production of diesel oil and gasoline from plastic waste is a topic that has received increasing attention in recent years, due to increasing awareness of the environmental problems caused by plastic waste and the need for alternative energy sources. Methods for converting plastic waste into liquid fuel, separating diesel and gasoline equivalents and examining their physico-chemical properties are the main focus of this research. Pyrolysis is the process chosen because the technology is simpler than other methods, such as gasification for example. A total of 6000 grams of plastic chips were pyrolyzed in an LPG-fueled reactor. Pyrolysis was carried out at temperatures of 200, 250, 300, 350, 400 °C, then the yield of oil produced at each temperature was weighed. It was found that the optimum temperature for pyrolysis was 300 because the increase in yield afterwards was very small. Next, 2000 grams of pyrolysis oil was distilled by gradually increasing the temperature from 100 to 300. The resulting 1520 grams or 79.17% gasoline equivalent fraction, 320 grams or 16.67% diesel fraction, the remaining 80 grams or 4.17% residual oil. The results of the physico-chemical properties examination showed that the diesel and gasoline fractions were similar to conventional diesel and gasoline.

Differential hydrocarbon generation characteristics of organic matter with green algae and cyanobateria origins in the Permain Lucaogou Formation of the Santanghu Basin

Organic-rich fine-grained rocks are key carriers of unconventional oil and gas resources, making it crucial to understand their hydrocarbon generation and evolution characteristics. This study examines the fine-grained rocks of the second member of the Lucaogou Formation (P2l2) in the Tiaohu and Malang Sags of the Santanghu Basin, focusing on how different organic matter (OM) backgrounds - primarily green algae and cyanobacteria - affect hydrocarbon generation and crude oil properties. Kinetic analysis and hydrous pyrolysis experiments on shales rich in green algae, cyanobacteria, and their mixtures revealed that green algae - derived OM requires lower activation energy to initiate hydrocarbon generation, results in an earlier oil generation peak, and has a broader oil window. Conversely, cyanobacteria - derived OM needs higher activation energy to start hydrocarbon generation, has a later oil peak, and a more concentrated generation period. These findings led to two models: the "green algae origin - early hydrocarbon generation - early oil peak - broad oil window model" and the "cyanobacteria origin - late hydrocarbon generation - late oil peak - concentrated oil generation model." Correlation analysis showed that aromatic hydrocarbons, resins, and asphaltenes significantly degrade crude oil quality. Hydrous pyrolysis experiments indicated that the heavy component content (aromatic hydrocarbons + resins + asphaltenes) in liquid hydrocarbons follows the order: residual oil > absorbed oil > expelled oil, with content initially increasing and then decreasing with maturity, and the color change of liquid hydrocarbons in dichloromethane reflects heavy component content changes effectively. Calculations of density and viscosity of liquid hydrocarbons, based on heavy component content and crude oil properties, were compared with the longitudinal distribution of crude oil properties in the study area. Results show that the hydrocarbon generation characteristics of green algae and cyanobacteria control crude oil properties, highlighting significant intra-source differentiation in the P2l2 shale and validates the phase separation approach in hydrous pyrolysis experiments. The P2l2 shale, with its high OM content and substantial hydrocarbon generation, holds great potential for shale oil exploration, but both reservoir quality and crude oil property evolution under different OM backgrounds should be considered when selecting favorable areas.

Research and Practice of Development Model during the Continental Heavy Oil Field’s Extra-high Water Cut Stage in the Bohai Sea

Abstract The formation mechanism, production limits and injection-production pattern of residual oil were studied by laboratory experiment, micropore simulation and reservoir engineering. The findings indicate that when injection times increase, the displacement efficiency rises as well. The residual oil mostly remains in the pore throat, which has a radius of 10 to 50 μ m, with a mean pore throat radius of 35 μ m.. As the displacement pressure gradient increases from 0.004MPa/m to 0.012MPa/m, When the displacement ratio of piston type increases and the displacement ratio of water film flow drops, the displacement efficiency grows. The horizontal well pattern’s gradient of displacement pressure is increased by 1.5 ~ 1.7 times compared with the oriented well pattern, and the displacement efficiency is increased by 12% ~ 15%. The development of the Bohai oilfield during the ultra-high water cut stage has been informed by the aforementioned findings, forming a horizontal well joint directional well three-dimensional pattern development model, oil production rate increased from 1.3% to 2.3%, and water drive recovery rate increased from 24.5% to 38.6%, realizing efficient development in the ultra-high water cut stage, and providing reference for the development of similar oil fields.

Single-layer iron network microstructure magnetorheological elastomer for transparent soft actuator

The motion of a soft magnetic magnetorheological elastomer, a composite material consisting of soft magnetic fillers and an elastomeric matrix, is limited by the gradient of the applied magnetic field, making its application as an out-of-plane soft actuator difficult. In this study, an anisotropic soft magnetic magnetorheological elastomer-based transparent soft actuator with large out-of-plane deformation was fabricated using a very low concentration (1 vol%) of carbonyl iron particles as the soft magnetic fillers. An applied AC electric field treatment method was used to manipulate iron particles in silicone oil, assembling and depositing them onto a glass substrate to form a single-layer iron-network microstructure. A single-layer iron-network microstructure-based magnetorheological elastomer (SL-sMRE) film with initial self-buckling was fabricated by exploiting the swelling properties of the residual silicone oil and polydimethylsiloxane. The SL-sMRE film exhibited out-of-plane deformation with a very short reaction time (228 ms) under a uniform magnetic field. When stimulated by a non-uniform magnetic field, the SL-sMRE film deformed away from the permanent magnet, which was not possible with an isotropic film. An optically transparent SL-sMRE film was applied to a transparent flexible gripping device that could detect the surface of a gripped object in real time.

Chemical kinetics of SARA fractions pyrolysis: Saturates and aromatics

This manuscript focuses on presenting a predictive and widely applicable model for describing the pyrolysis of saturates and aromatics, two of the so called SARA (Saturates, Aromatics, Resins, Asphaltenes) fractions. The fractions extracted from two different oil samples, a typical Heavy Fuel Oil 380 and a typical Vacuum Residue Oil, were thoroughly investigated. Different experimental methods elucidated the elemental composition, chemical structure, thermal degradation behavior, and characterized the products released during the pyrolysis of these two oils. Finally, a model to describe the pyrolysis of saturates and aromatics was developed. The model is comprehensive of methodology for the definition of a surrogate and a kinetic mechanism to describe its pyrolysis. The surrogate is defined using a certain number of pseudo-components, whose mass fraction in the mixture is defined to match the chemical properties of the actual fuel. A kinetic mechanism was defined by pairing each pseudo-component with a reaction to describe its thermal decomposition. The model was then validated against literature data and demonstrated to be predictive in describing the pyrolysis of different samples.

‘Supercharged’ Shale EOR: A Liquid-Hydrocarbon-Based Approach Enters the Fray

Around a decade of research and testing has passed by, and the unconventional sector has yet to show that natural gas huff-and-puff can scale effectively across tight-oil fields. This doesn’t mean enhanced oil recovery (EOR) in shale is a lost cause. Though it does suggest that the industry needs alternatives to the first and most well-known method. Proof of this can be found in North Dakota’s Bakken Shale where researchers, operators, and a firm called EOR ETC have tried to show that the water-alternating-gas method is a cheaper, less gas-intensive way of adding incremental barrels. EOR ETC has indicated on its website that ExxonMobil subsidiary XTO Energy is currently testing the technology. Chevron has also recently shared how it has rethought shale EOR methods by designing a program for production-boosting surfactant injections and gas injections that can be done with artificial lift instead of giant compressors. Another emerging shale EOR concept goes a step further, arguing that the unconventional sector should abandon natural gas injections altogether. Denver-based Shale Ingenuity proposes that liquid-hydrocarbon solvents should be used instead. Shale Ingenuity has patented a process called SuperEOR, which it claims delivered a strong showing during its initial field test in the Eagle Ford Shale of south Texas. After nearly a year of cyclic solvent injections, which began in early 2023, a horizontal well with a 4,400-ft lateral and 16 fracture stages produced 44% more oil than its previous total output. This resulted in a 30-fold boost in flow rate, from 13 to 391 B/D. Building on its initial success, Shale Ingenuity informed JPT that two private producers in the Permian Basin and the Eagle Ford have selected its EOR technology for upcoming projects. Both will involve single four-well pads, with EOR operations expected to begin in 2026. The solvents used in the pilot consisted mostly of natural gas liquids (NGL)—ethane, propane, butane, and pentane. Shale Ingenuity said formulations may include other hydrocarbon and nonhydrocarbon liquids. While the bulk of these products flow straight out of thousands of wellheads in the US shale sector, Shale Ingenuity emphasizes that the key to unlocking their potential for EOR lies in its proprietary method of blending, or “tuning,” the solvents based on formation and crude oil properties. This allows the injected solvents to quickly mix with and help mobilize the residual oil droplets that are trapped in tight-rock formations, according to the company. Robert Downey, founder and CEO of Shale Ingenuity, explained the process. “The tuned solvents we are using have a minimum miscibility pressure (MMP) of 700 to 900 psi, which means it doesn’t take much pressure to drive them into solution. When pumped into the well, they instantly become miscible with oil, and as the formation heats up and the well is reopened, the solvents expand back into gas at 100 to 200 times their liquid volume.” The effect of all this is what he describes as a “supercharging” of the solution gas drive mechanism that promotes the strong early well flow shale wells are known for. This is the energy released by dissolved gas in the oil as it expands during the pressure drop brought on by producing the well.

Uncovering the impact of morphology of porous media and capillary number on immiscible oil recovery using computational fluid dynamics

Pore-scale simulation and analysis of oil displacement in digital rocks has shown great promise in tracking oil recovery in porous media. This paper examines three digital rocks with varying pore and throat radii but the same porosities, studying their behavior under immiscible oil recovery through waterflooding. Computational fluid dynamics was used to conduct numerical simulations to observe the impact of rock morphology on breakthrough times, residual oil saturations, and oil displacement patterns. The validity of the simulation mechanism is confirmed in both imbibition and drainage conditions through the pore doublet Chatzis' experiment. This study consisted of 33 separate simulations which varied in mobility ratios, interfacial tensions, and injection velocities. The findings suggest that smaller pore and throat radii result in higher oil recovery and water percolation and faster breakthrough times that facilitates the effects of viscous fingering. An increase in capillary number was found to have a significant impact on oil recovery in larger pores and throats.