Oil Migration Process Research Articles

Simulation Analysis of Metallic Particles Movement in Typical Structure of Oil-immersed Power Transformer

The insulation performance of oil-immersed power transformers is closely involved with the movement of metal particle impurities, and the movement characteristics of metal particles are not only influenced by the electric field, but also by the oil flow. In this paper, a solid-liquid two-phase flow simulation model was constructed, and the effect of electric field on the motion of metal particles was considered. Firstly, the validity of the simulation model was verified by using the experimentally observed motion of metal particles in the horizontal oil channel between parallel flat plate electrodes, based on which the motion of metal particles in the typical oil channels of a 500kV power transformer was studied. It was found that when the metal particles passed through the oil flow inlet, the number of metal particles settling increased with the increase of particle size. All the metal particles with 1mm particle size sank in the oil flow inlet during the oil migration process, it was almost impossible to enter the low, medium and high voltage winding parts. Through the middle or upper end of the high voltage winding, the smaller particles (50μm, 150μm) would easily migrate with the oil flow and move faster; the larger particles (500μm) would move slower or be more easily deposited. This research holds significant practical implications in the engineering study of metal particle motion distribution within transformers.

Mesoscale migration of oil in tight sandstone reservoirs by multi-field coupled two-phase flow

The oil migration process plays a pivotal role in determining the distribution and scale of oil reservoirs in tight sandstone formations, while also simultaneously influencing their development outcomes. However, the mechanisms governing oil migration in these tight formations remain poorly understood. This study conducted numerical simulations to investigate the oil migration characteristics in tight sandstone at the mesoscale. Multivariate regression analysis was used to characterize the micromechanical parameters of a 3D digital core. In addition, the main equations describing the two-phase flow that couples the stress and seepage fields were proposed, thereby elucidating the oil migration process. Finally, the effects of the reservoir space type, pressure gradient, and stress on the oil migration efficiency were assessed. The results showed that: (1) Compared with the porous-type model, the fractured-type model had a higher level and more concentrated distribution of damage, better connectivity, and higher oil migration efficiency due to the seepage-stress coupling effect; (2) High fluid pressure gradients improved the efficiency of oil migration and enhanced the control of the three-dimensional distribution of the pore domain over oil distribution in the matrix domain. (3) When σ1 >σ3, the oil phase migration efficiency improves with the increasing axial stress. When σ1 <σ3, the oil phase migration efficiency decreases with the increasing confining stress. When σ1 = σ3, high stress leads to low oil phase migration efficiency. This study reveals the mesoscopic-scale mechanism of oil migration in tight sandstone reservoirs and may prove useful in the exploration and development in such reservoirs.

Physical properties of cocoa butter: effect of sucrose esters on oil migration

SummaryIt is known that emulsifiers can modify the crystallisation behaviour of fats, improving their stability. In this sense, changes in the crystallisation behaviour of cocoa butter (CB) may contribute to reducing oil migration through its crystalline structure. This study analysed the effect of adding sucrose stearate (S‐370) and sucrose behenate (B‐370) emulsifiers at different concentrations on oil migration in CB. The compatibility diagram curves indicated a miscible phase behaviour between CB and the emulsifiers S‐370 and B‐370 at concentrations of 0.1%, 0.3% and 0.5%, confirming the compatibility between its components. There is a significant difference (P ≤ 0.05) for the melting point of mixtures containing 0.3% and 0.5% of S‐370, yet we can consider that all samples reach their total melting point at 35 °C. However, the samples containing S‐370 showed a higher firmness profile than those containing B‐370, corroborating the results of compatibility and melting point. CB exhibited characteristic two‐step isothermal crystallisation at 17.5 °C, with distinct effects of the emulsifiers for each crystallisation step. S‐370 and B‐370 modify the solid dissolution process and oil migration through cocoa butter. The physical properties of CB were altered by adding S‐370 and B‐370. The oil migration process differed for each emulsifier, although diffusion, the identified migration mechanism, is the same for both.

Calcite U-Pb ages constrain petroleum migration pathways in tectonic complex basins

Abstract Tracing secondary oil migration pathways is critical for understanding petroleum system evolution histories. Traditional tools (e.g., molecular indicators and numerical modeling) utilized for evaluating oil migration processes either lead to ambiguous interpretations or only provide qualitative estimates. We quantitatively constrain secondary oil migration processes under an absolute time frame by integrating oil-inclusion fluorescence and in situ calcite U-Pb dating on calcite veins and cements hosting primary oil inclusions. Fluorescence spectra of oil inclusions and U-Pb ages were obtained on samples from ultra-deep Ordovician reservoirs along two major faults in the Halahatang oilfield, Tarim Basin (northwestern China). Absolute U-Pb ages suggest two main oil charge events during 475–433 Ma and 294–262 Ma, respectively, and revealed a northward-decreasing trend for oil maturity during single charge events. Vertical migration of oil from in situ source rock through active (or reactivated) faults is believed to be the key process inducing the spatial maturity variation in charged oils and considered as the main mechanism of secondary migration, with brecciated fault zones and dilatant fractures along faults acting as major vertical oil-migration pathways. The successful application of this approach has wider implications for elucidating petroleum migration processes in tectonic complex basins worldwide.

Geochemical characteristics and genesis of crude oils with complex physical properties in the eastern part of the southern gentle slope of Dongying Sag

The crude oil in the eastern part of the southern gentle slope of Dongying Sag has complex physical properties, and various crude oils with different properties such as heavy oil, high sulfur oil, and high wax oil have developed. The complexity of the physical properties reflects the influence of the source rock properties, crude oil migration process, and secondary alteration after accumulation on crude oil characteristics. Through systematic analysis of geochemical data, the formation mechanism of crude oil with these special physical properties has been clarified. The result of hydrocarbon generation at an early stage from source rocks rich in high-sulfur kerogen deposited in a euxinic waterbody is the cause of high-sulfur crude oil with low maturity in Wangjiagang oil field. While the shallow reservoir burial depth and the resulting biodegradation is the mechanism of the formation of high-sulfur crude oil in Le’an oil field with higher maturity. Biodegradation is the main mechanism of the formation of heavy oil, and the recharge of hydrocarbons into the degraded crude oil reservoirs leads to the complication of crude oil density. Both the hydrocarbon generation of organic matter rich in terrestrial higher plants and phase-controlled fractionation during hydrocarbon migration lead to the generation of high wax crude oil.

In Situ Wettability Investigation of Aging of Sandstone Surface in Alkane via X-ray Microtomography

Wettability of surfaces remains of paramount importance for understanding various natural and artificial colloidal and interfacial phenomena at various length and time scales. One of the problems discussed in this work is the wettability alteration of a three-phase system comprising high salinity brine as the aqueous phase, Doddington sandstone as porous rock, and decane as the nonaqueous phase liquid. The study utilizes the technique of in situ contact angle measurements of the several 2D projections of the identified 3D oil phase droplets from the 3D images of the saturated sandstone miniature core plugs obtained by X-ray microcomputed tomography (micro-CT). Earlier works that utilize in situ contact angles measurements were carried out for a single plane. The saturated rock samples were scanned at initial saturation conditions and after aging for 21 days. This study at ambient conditions reveals that it is possible to change the initially intermediate water-wet conditions of the sandstone rock surface to a weakly water wetting state on aging by alkanes using induced polarization at the interface. The study adds to the understanding of initial wettability conditions as well as the oil migration process of the paraffinic oil-bearing sandstone reservoirs. Further, it complements the knowledge of the wettability alteration of the rock surface due to chemisorption, usually done by nonrepresentative technique of silanization of rock surface in experimental investigations.

Investigating the Influences of Pore-Scale Characteristics on Tight Oil Migration by a Two-Phase Pore Network Model

The migration of expelled hydrocarbon from source rock into unconventional tight reservoirs is subject to different pore-scale fluid transport mechanisms as opposed to the conventional counterparts and therefore plays a crucial role in controlling the hydrocarbon distribution and accumulation in the former. One of the different mechanisms is related to the formation of a more viscous boundary layer (BL) of brine, i.e., wetting phase fluid on pore surfaces, giving rise to the so-called BL effect. In this work, a two-phase pore network model (PNM) that considers this BL effect is developed to study the influences of pore-scale characteristics on the oil migration process, manifested through the BL effect in tight-sandstone media. Good agreements are reached between experimentally derived relative permeability curves and predicted ones, by applying this model to the pore-network networks extracted from the same samples. Then, this validated model was used to evaluate the impacts of the following factors on the oil migration process: pore radius, coordination number, aspect ratio, brine viscosity, and wettability. The results show that all factors can influence the oil migration process but at different magnitudes. The applicability and significance of the developed tight oil migration PNM are discussed in this work.

Interfacial self-propagation of oleophilic vaterite in crude oil emulsion and its application for reinforcing polyethylene

Non-nature mineral vaterite crystals with lipophilicity are generated in the crude oil migration process, which adversely affects the oil recovery and causes environmental pollution. In this work, a simulated interfacial self-propagating strategy has been designed to obtain quasi hydrophobic and oleophilic vaterite crystals by mixing heavy alkyl-benzene sulfonate (HABS)/Na2CO3/crude-oil emulsion and partially hydrolyzed polyacrylamide (HPAM)/CaCl2/crude-oil emulsion. Oleophilic vaterite is produced through ions migration and self-assembly of nanocrystals at the oil/water interfaces. Monodispersed vaterite spheres were achieved with an average diameter of 2.4 μm, a water contact angle of 88.5°, and a kerosene contact angle of 4.5°. Due to the oleophilic surface, the vaterite has a good compatibility with polyethylene, which exerts an essential role in improving the mechanical properties of polyethylene. This finding enriches the understanding of CaCO3 mineralization in oilfield, and provides new strategy not only for waste-derived application of the vaterite scales but also for organic-inorganic composites manufacturing.

A Mathematical Model for Determining Oil Migration Characteristics in Low-Permeability Porous Media Based on Fractal Theory

Oil migration processes are crucially important for determining oil reserve levels and distributions in low-permeability reservoirs. Previous researches have proved that the macroscopic parameters of oil migration processes are controlled by microscopic pore properties in low-permeability media. To analyze the relationship between pore-scale parameters and the oil migration process in low-permeability formations, a mathematical model combining the capillary bundle model and fractal theory is developed in this work. The accuracy of the proposed model is validated via comparisons with three well-designed oil charging experiments using natural core samples. Based on the validated model, the influence of four factors (pore fractal dimension, tortuosity fractal dimension, the wettability of the rock surface, and the formation water viscosity) on oil migration processes in low-permeability media is analyzed. Oil saturation and effective permeability are used as the output parameters for reflecting changes in the oil migration process. The calculation results indicate that oil saturation decreases as pore fractal dimension, tortuosity fractal dimension, the hydrophilicity of the rock surface, and brine viscosity increase. On the other hand, effective permeability decreases as tortuosity fractal dimension and formation water viscosity increase, but increases with pore fractal dimension. Moreover, the wettability dependence of effective permeability is relatively weak.

Study of Oil Migration Processes in Meadow Soils

Study of Oil Migration Processes in Meadow Soils

Fractionation of dibenzofurans during subsurface petroleum migration: Based on molecular dynamics simulation and reservoir geochemistry

Dibenzofurans, oxygen-containing heterocyclic aromatics, are ubiquitous in crude oils. Their geochemical implications in petroleum geochemistry have been studied in numerous previous publications. Here, we present the distribution of dibenzofuran and its methylated homologues, and calculate the polarity and solubility of methyldibenzofuran isomers based on the Connolly surfaces and molecular dynamics simulation. The results show that the geo-chromatographic fractionation effect is evident due to absorption onto the water/silica matrix carrier bed during the oil migration process. Two potential molecular indicators relative to dibenzofurans, i.e. the total content of dibenzofurans and the relative abundances of 1-methyldibenzofuran to 4-methyldibenzofuran, are proposed for tracing the oil migration orientation and filling pathways. These two indicators were applied successfully in Paleozoic marine carbonate and Tertiary lacustrine sandstone reservoirs. The variations of source input, depositional environment, and maturity for oils from same source bed/kitchen appear to have no significant effect on these two indicators. It suggested that these two dibenzofuran indicators are potentially effective molecular tracers for orientation and filling pathways in oil migration.

APPLICATIONS OF COMPUTER MICROTOMOGRAPHY FOR ANALYSIS AND MODELING OF OIL MIGRATION IN THE SOIL

The paper discusses modeling of oil migration processes in the soil with the use of x-ray microtomography to optimize the process of oil spill elimination. To conduct the study, the most common soils on the territory of Tyumen region, i.e. sandy and sandy loam soils, were taken. Then a process of an oil spill was simulated on the micro model. As a result of the analysis, 3D-models of spatial distribution of oil in the soil were created and the depth of oil penetration into the ground was determined.

Effects of Cocoa Butter Origin, Tempering Procedure, and Structure on Oil Migration Kinetics

The effects of cocoa butter (CB) origin, tempering procedure, and structure on oil migration kinetics were studied using a flatbed scanner followed by image processing and analysis. The migration rate (OMR) and migration distance (I10) of stained oil were determined in tempered and nontempered CBs. Tempered matrices had 10 to 50 times lower OMRs than nontempered CBs. In addition, the lag phase observed before significant oil migration was also significantly longer in tempered CBs (12 days vs 2 days in nontempered butters). Moreover, cocoa butter origin had a strong effect on OMR. Brazilian and Nigerian CBs had the highest OMR in both tempered and nontempered samples. Malaysian CB had the third highest OMR, but this effect was only significant in untempered samples. Finally, the lowest OMRs were found in Chinese, Ecuadorian, and Ivorian cocoa butters. The amount of oleic acid and triunsaturated triglycerides (UUU) was strongly correlated to OMR (the higher the UUU concentration, the lower the resistance to oil migration). However, the relationships between the permeability coefficients and structural factors (squared averaged particle size and crystalline domain size) suggest that the micro- and nanostructure of the material also plays a significant role in the oil migration process.

Optimization of a scanner imaging technique to accurately study oil migration kinetics

The aim of this study was to refine an image analysis technique that was developed in our laboratory in order to study oil migration in confectionery products (Marty, S., Baker, K., Dibildox-Alvarado, E., Neves Rodrigues, J., & Marangoni, A. G. (2005). Monitoring and quantifying of oil migration in cocoa butter using a flatbed scanner and fluorescence light microscopy. Food Research International). The migration of a nile red stained oily phase (soft fat) was monitored in tempered cocoa butter matrices kept at 18 °C for about 75 days. Oil migration kinetics was quantified using a common flatbed scanner followed by image processing and analysis. The most reliable parameter derived from this analysis is the position of the dye front (I10) where the intensity of the dye is 10% of maximum. The determination of the amount of dye migrated from pixel intensity measurements was found to be highly affected by cocoa butter structure at times greater than 28 days, but I10 was not. The determination of a model-independent oil migration rate (I10/tn) using this method was found to be highly reproducible and accurate. Due to the observed non-linearity of the oil migration process and the effects of matrix structure on the determination of pixel intensity (and thus mass of dye migrated), the quantification of oil migration using the simplified version of Fick’s second law is not recommended.