查看更多>>摘要：Elbows are widely used in piping systems to change the direction of flow. However, it is also extremely sus-ceptible to erosive damage, which may lead to the leakage of petroleum and gas pipelines. Therefore, revealing the erosion process and accurately predicting erosion rate are of great importance to pipeline safety. In this study, the unsteady slurry erosion process in the 90 degrees elbow is investigated numerically using LES Eulerian-Lagrangian methodology. The Large eddy simulation (LES) is coupled with Lagrangian particle tracking to simulate slurry flow and erosion process in elbows. The erosion prediction model is validated using experimental data before investigating the unsteady erosion process in elbows with different radius. The results show that the unsteady secondary flow can be precisely captured using LES and thus the prediction accuracy of the fluid flow velocities and turbulent intensities are improved by this model comparing to RANS. The particles movement coupled with the unsteady secondary flow and boundary separation in elbows with different radius can be successfully revealed using this methodology. The LES Eulerian-Langragian erosion model presented is helpful to understand the flow and slurry erosion in elbows and improve the accuracy of the CFD-based prediction of slurry erosion rate.
查看更多>>摘要：In this study, the efficacy of blend, of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP), was explored for enhanced CO2 absorption and thereafter, used polymer enhanced carbonated fluid for flow behaviour and oil recovery from synthetic porous media of sand, prepared by wet-ramming of sand in sand-pack. Initially, PVA-PVP blends of varying wt% (2-5 wt% PVA and 1-3 wt% PVP) were formulated and their stability along with potential for CO2 absorption were investigated via viscosity measurements and thermogravimetric analysis over varying pressure, temperature, and saline conditions. Thermal stability results indicated that the performance of PVA-PVP solutions was better (than pure PVA solution) even at 150 degrees C. Comparative viscosity tests indicated that the impact of adverse conditions was least on PVA-PVP solutions consequently, these solutions proved to be excellent CO2 carrier fluid after CO2 solvation experiments in an equilibrium cell. Rheological results indicate strong interactions between PVA and PVP which was understood by the formation of new bonds in solution causing an increase in the viscosity and solid like nature of solution. Finally, these solutions were used as EOR agents for oil recovery from a porous media. The oil recovery tests were performed at a temperature of 40 degrees C and reservoir salinity of 4 wt% NaCl and these results indicated that PVA-PVP solutions displayed enhanced oil mobilization in these conditions. As a result, oil recovery improved by 12-18% original oil in place (OOIP). Thus, based on the results of this study, it can be anticipated that newer polymer composites of PVA-PVP exhibited better synergy with CO2 and act as CO2 carrier fluid for improved oil recovery and enhanced carbon storage. In addition, they are viable candidates for use in elevated temperature and saline conditions of oil reservoirs.
查看更多>>摘要：Efficient removal of residual oil from produced water (PW) is a challenging but crucial task to meet the increasingly stringent environmental regulations. The current study presents lab-made magnetite particles coated with different amounts of oleic acid (OA) as an efficient and environment-friendly solution for the removal of low concentrations of oil from PW. Performance of the particles in oil removal experiments was studied as a function of the coating factor, adsorption time, oil to the particle concentration ratio and concentrations of emulsifier and salt. Furthermore, reusability of the particles after regeneration through solvent washing and centrifugation was studied. It was observed that the oil removal efficiency of the particles improves by increasing the OA coating factor up to 32 and decreases thereafter. Increasing oil to the particle concentration ratio boosted oil removed per unit time as well as the final oil removal efficiency. Salinity alone did not disturb the oil removal efficiency of the particles whereas oil adsorption efficiency was negatively affected due to the presence of emulsifier alone or in combination with the salinity. Adsorption of oil on the particles followed a Freundlich isotherm model and the kinetic was described by the pseudo-second-order model. Solvent washing completely restored the performance of the particles and was found to be more effective than centrifugation. It was concluded that the proposed particles offer a promising and highly efficient solution for the removal of residual oil from PW.
查看更多>>摘要：Asphaltene removal from sediments is essential for enhanced oil recovery from heavier crude oil reservoirs and tar sands and bitumen recovery from bottom products in downstream processes. Water injection or water flooding at high pressures exert shear forces that can overcome the adhesive forces between asphaltene and mineral surfaces. The adhesive forces are also affected by ions in the aqueous medium. In the current work we study asphaltene removal from silica surface using shear forces of aqueous media in a parallel plate channel. We demonstrate the effect of varying pH and surfactant conditions in aqueous media on asphaltene removal efficiency. We relate the removal efficiency with fractional asphaltene volume on the surface estimated from atomic force microscopy. The fractional asphaltene volume reduces to 0.12 at pH 10, which is approximately 50% lower than water at neutral pH at the same shear rate. We show that the water-soluble anionic surfactants are inefficient in asphaltene removal, whereas cationic surfactant reduces the asphaltene fraction to 0.30. We conclude that the removal efficiency is affected by the zeta potential of the asphaltene and the surface, where electrostatic repulsion between the asphaltene and the surface and increased wettability in the presence of cationic surfactant improves asphaltene removal.
查看更多>>摘要：Compositional modeling is essential when simulating any process that involves significant changes in the composition of reservoir fluids. This includes modeling the flow of multicomponent hydrocarbons in pipes, surface facilities, and subsurface rocks. However, the rigorous thermodynamics approach to obtain phase composition is computationally expensive. So, various researchers have considered using machine learning models trained with rigorous phase-equilibrium (flash) calculations to improve computational speed. Unlike previous publications that apply classical deep learning (DL) models to flash calculations, this work will demonstrate the first attempt to incorporate thermodynamics constraints into the training of these models to ensure that they honor physical laws. To this end, we generated one million different compositions with a space-filling mixture design and performed two-phase flash to obtain the corresponding phase compositions. We performed seven-fold cross-validation to ensure reliable estimates of model accuracy. We compared the physics-constrained and standard DL model results to quantify the ability of our approach to honor physical constraints. The evaluation of our physics-informed neural network (PINN) model compared to a standard DL model shows that we can incorporate physical constraints without a considerable reduction in model accuracy. Based on the test data, our model evaluation results indicate that both PINN and standard DL models achieve coefficients of determination of 97%. In contrast, the root-mean-square error of the physics-constraint errors in the PINN model is at least two times smaller than in the standard DL model. To further demonstrate that our PINN model out-performs the DL model in terms of honoring physical constraints, we generate phase envelopes using the overall compositions predicted using the PINN and DL models for several fluid mixtures in the test data. These results show the importance of incorporating the thermodynamic constraints into DL models.
查看更多>>摘要：Hydraulic fracturing has become the dominant development technology for unconventional reservoirs. The accurate prediction of rock breakdown pressure is key to fracturing design in deep formations where the wellbore shape is prone to deform into an ellipse. However, few of the presented theoretical models for breakdown pressure focus on the wellbore deformation, which may lead to inaccurate results. Therefore, a theoretical model for analyzing fracture initiation from a perforated elliptical wellbore is proposed by using the conformal mapping method. Additionally, the analytical solution for the breakdown pressure and the initiation angle at the fracture tip is obtained by using the derived stress intensity factor at the perforation tip based on the fracture mechanics and the maximum tangential stress (MTS) criterion. The model is verified by comparing the previous experimental and theoretical breakdown pressure data for perforated circular wellbores. The effects of the wellbore deformation, perforation orientation, perforation depth, and fracture toughness on fracture initiation are analyzed. It is shown through theoretical analysis that a breakdown pressure predicted without considering the wellbore deformation will be overestimated, and it is unwise to optimize the perforation orientation based on the fracture toughness of rocks. To reduce the breakdown pressure and avoid excessive fracture curvature near the wellbore, the recommended optimal perforation depth is about 1.5-2 times the size of the wellbore and it is better to control the perforation orientation that is adopted within 20 degrees. The proposed model is a new attempt to calculate the rock breakdown pressure of a perforated elliptical wellbore, which can provide some guidance for the perforation optimization in a deep formation.
查看更多>>摘要：Production of crude oil from a matured oil reservoir is challenging due to the low recovery factor. Hybrid methods have demonstrated potential in oil recovery from the matured crude oil reservoir. In recent years, the low salinity water with chemicals (viz., surfactant, polymer) and nanoparticles have brought the attention of the researchers due to their ability in altering the interfacial properties of the rock-oil-water systems favorable for crude oil recovery. The current interest by industries in injection fluid (i.e., low salinity water injection) has prompted the invention of a hybrid oil recovery agent for matured crude oil reservoirs. In the current study, a novel silica-based hybrid nanofluids (NFs) of variable silica nanoparticles (NPs) concentration in low salinity seawater with anionic surfactant (AOT: dioctyl sodium sulfosuccinate) and polymer (PVP-K30: polyvinylpyrrolidone) (sometimes referred to as SMART LowSal) are used as an injection fluid in a sand-pack reactor. Oil recovery from oil saturated sand-pack reactor is observed to enhance due to NFs (hybrid) injection after secondary recovery. The characteristic study of relative permeability curves discloses that sand surface was initially water-wet and converted to strongly water-wet in the presence of NFs. A nuclear magnetic resonance (1H NMR) study reveals that adsorption of the chemical appeared on the sand surfaces, which could be the reason for wettability alteration, and thereby enhanced oil recovery. Similarly, the scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) of the sand samples before and after injection disclosed desorption of hydrocarbon from the sand surfaces after NFs injection. An additional 5-10% oil recovery is achieved after chemical flooding due to the injection of NFs. Adsorption isotherm study well agreed with the monolayer adsorption of surfactant on the sand surface.
查看更多>>摘要：Heavy oil and water dispersed flows in a 0.0254 m, 0.0381 m, 0.0508 m ID horizontal pipelines (Pipeline length = 2.5 m) were investigated experimentally and numerically (at steady state) without and with additives by varying the temperature from 25 degrees C to 50 degrees C by considering power law (i.e., for emulsion) rheological behavior. The development of boundary layer, pressure drop, velocity profile, boundary layer thickness, and wall shear were discussed in these numerical investigations without and with water, ML (i.e., a natural extract from Madhuca Longifolia), and PS (i.e., potato starch) via pipeline transportation of heavy oil. The pressure drops in the numerical simulations were compared with the available experimental results and found in qualitative agreement (i.e., max error +/- 7%). The pressure drop from the inlet to the outlet was decreased with an upsurge in the concentration of bio-additives in the aqueous phase of the heavy oil emulsion and temperature. The development of the boundary layer was significantly varied after adding water and bio-additives to the heavy oil. The ratio of boundary layer thickness and pipe length is reduced by increasing the additive's temperature and concentration in the heavy oil-water flows. Furthermore, the reduction in wall shear occurred after efficiently adding water and bio-additives to the heavy oil during transportation. The comparative studies also carried out between the influence of additives on the hydrodynamic parameter. The bio-additives (ML and PS) in the aqueous phase improve the hydrodynamics of heavy oil flow in the pipeline. Natural extract ML improves the hydrodynamics of heavy oil flow through the pipeline than potato starch. The application of numerical investigations can significantly enhance understanding the hydrodynamics of the heavy oil/emulsion's transportation via pipelines with greater accuracy for complex pipeline configurations.
查看更多>>摘要：The shale of the Middle Permian Lucaogou Formation in the Jimusaer Sag has become one of the most important prospects for unconventional shale oil production in China. The Lucaogou Formation develops two sweet spots, the upper (P(2)l(2)(2)) and lower (P(2)l(1)(2)) sweet spots, which are not more than 150 m apart. Interestingly, oils produced from the lower sweet spots have higher densities and viscosities than those in the upper sweet spots. Meanwhile, these high-viscosity oils have brought technical challenges to shale oil production. In this paper, geochemical data from 78 source rock solvent extracts and 17 oil samples from various depths were employed to elucidate unconventional petroleum systems and the reason for high viscosities. The source rocks of the Lucaogou Formation are good to excellent, primarily type II and II-III kerogens, and are now in the early-peak oil window. Oils produced from the P(2)l(1)(2) interval are characterized by abundant polar compounds, which are derived from the P(2)l(1)(2) and P(2)l(1)(1) intervals source rocks with relatively high marine sources contribution. Oils in the P(2)l(2)(2) interval are generated from the P(2)l(2)(2) interval source rocks with relatively high terrigenous-marine sources contribution. Terpane biomarker ratios indicate all oil samples are derived from lacustrine source rocks. The distributions of terpanes and steranes in these samples are similar, with high quantities of C-29 steranes and low amounts of diasteranes. Migration from sources to reservoirs in the Lucaogou shale oil systems is short-distance given thermal maturity considerations. All oil samples have experienced slight biodegradation (PM level 1-2) at most. The sources and thermal maturities are the primary reasons for the high viscosities of the crude oils produced from the P(2)l(1)(2) interval. This research also indicates the Lucaogou shale petroleum system could be divided into two subsystems, and the production of different unconventional petroleum subsystems requires different strategies.
查看更多>>摘要：Research on the migration and accumulation of hydrocarbons in shale oil reservoirs composed solely of organicrich mudstones has not received adequate attention. The Qianjiang Formation provides an opportunity for research on the hydrocarbon accumulation mechanism due to the presence of hydrocarbon migration characteristics in its inter-salt organic-rich fine-grained rocks. In this study, the inter-salt stratum of the tenth rhythmite can be classified into three sections: lower, middle, and upper. The middle section is mostly composed of laminated marlstones and laminated calcite-bearing argillaceous dolomicrites, whereas, the lower and upper sections mostly contain bedded muddy dolomicrites and glauberite. Geochemical analysis was conducted to study the organic matter enrichment mechanism and shale oil accumulation characteristics. The results indicate that the middle section has the highest organic matter abundance, with poor organic matter abundance displayed by the other sections. The C27/C29 sterane and extended tricyclic terpane ratios suggest that the organic matter types in different sections of the inter-salt stratum differ, and the middle section has more aquatic organic matter than other sections. The sedimentary structures and salinity-related parameters indicate that the middle section was developed in a deep stratified saline lake and that the other sections were formed in a shallow hypersaline lake. This study shows that high biological productivity and stratified lake water facilitated the enrichment of organic matter, resulting in high organic matter content in the middle section. The oil saturation index and hydrocarbon composition suggest that hydrocarbons were differentially accumulated in the inter-salt stratum of the tenth rhythmite. The maturity-related biomarkers further revealed the possible migration paths of hydrocarbons in the inter-salt stratum. Based on the aforementioned analyses, this study established an inter-salt shale oil accumulation model. This study suggests that hydrocarbons were released from the mature source rocks in the deep depression with differential migration laterally and vertically within the inter-salt stratum. The study of the Qianjiang Depression shows that organic-rich fine-grained rocks cannot only form in situ sweet spots but may also possess migrated hydrocarbons inside them, which are characterized by high organic matter abundance and oil saturation. This research provides a new case for further understanding hydrocarbon accumulation inside source rocks.
NSTL
Elsevier