Crude Oil Flow Research Articles

Modeling apparent viscosity of waxy crude oils doped with polymers using tree-based models, radial basis function neural networks, and Gaussian process regression

The probability of wax precipitation increases as temperature decreases and this happens during the flow of crude oil from a high temperature reservoir to the cool surface facilities. The present work aims to evaluate the apparent viscosity of waxy crude oils in two conditions: without presence of polymers and doped with them. To reach this purpose, a comprehensive databank consists of 622 actual values of waxy crude oils’ apparent viscosity were gathered. Various intelligent networks including Radial Basis Function (RBF) coupled with three algorithms, namely Teaching-Learning Based Optimizer (TLBO), Marine Predators Algorithm (MPA), and Barnacles Mating Optimizer (BMO), Decision Tree (DT), Random Forest (RF), Extra Tree (ET), and Gaussian Process Regression (GPR) were trained to predict waxy crude oil viscosity values. According to the findings, the GPR model demonstrates exemplary performance and offers forecasts with the minimum average absolute percent relative error (AAPRE = 0.30 %), the highest coefficient of determination (R2 = 0.999), and the lowest standard deviation (SD = 0.011). The accuracy of the other models was also acceptable and overall, tree-based techniques (except ET) and GPR provided better results than RBF coupled with different optimizers. Ultimately, the Leverage method was applied to identify the suspected dataset utilizing outlier detection. The outlier discovery represented that majority of data points, which were used for modeling in this paper, are statistically valid and trustworthy.

Temperature Field Study of Offshore Heavy Oil Wellbore with Coiled Tubing Gas Lift-Assisted Lifting

Offshore heavy oil resources are abundant, but they have greater difficulty and higher costs compared to onshore extraction. When crude oil flows through the seawater section, the temperature of the crude oil decreases faster, making it susceptible to solidification in the wellbore and resulting in lower well production. The cooling of crude oil becomes more pronounced in deep-water wellbore. However, the injection of low-temperature gas will have a cooling effect on the formation production fluid, which will have a negative effect. The model analyzes the effects of coiled tubing running depth, gas injection temperature, gas injection volume, coiled tubing diameter, and crude oil production on the temperature distribution of heavy oil in deep-water and shallow water wellbores. We propose recommendations for the selection of each parameter for deep and shallow water environments by analyzing and summarizing the laws.

The Foundation and Validation of Sigmoid-Typed Functions for Fouling Formation Modelling of Crude Oil Flows

The phenomenological model of fouling formation is investigated in this research which, the parametrization method based on the species and energy equation is implemented. It is shown that the previous empirical sigmoid-typed correlation can also be generated from the species equation as a special solution. Meanwhile, the fouling heat resistance is obtained from the phenomenological energy equation. Correlating these two solutions, it is shown that the proposed model generates key parameters of fouling formation characteristics of crude preheat train within all operational conditions. Thus, it generalizes the previous models as it covers wider operational range.

Enhancement of flow characteristics in waxy crude oil under the influence of subtle magnetic fields

The study aims to improve flow in weakly magnetized transportation of waxy crude oil. The magnetization of waxy crude oil with a weak magnetic field strength below 100 mT was investigated using magnetization processing equipment. By employing the orthogonal experimental principle and data processing method, the magnetization effect of crude oil and its primary influencing factors were examined and analyzed. A new concept, equivalent viscosity reduction rate, is introduced along with criteria for evaluating the effectiveness of reducing magnetization viscosity. The equivalent viscosity reduction rate increases as magnetization intensity rises, but initially increases and then decreases as magnetization temperature increases. The viscosity reduction is most significant when the magnetization temperature is close to the wax appearance temperature, resulting in an 18% equivalent viscosity reduction rate. We clarify the mechanism of enhancing crude oil flow with magnetic fields by integrating previous microscopic studies. The viscosity reduction effect of magnetized wax crystals is orderly under a weak magnetic field. The nucleation of magnetic wax limits the viscosity reduction effect of magnetization at high temperature. The reduction in the length-diameter ratio of magnetized wax crystals and boundary box dimensions contributes to enhancing the low temperature fluidity of crude oil.

Resource utilization of expired progesterone medicines as flow improver for waxy crude oils

At present, the treatment of expired medicines mainly involves burning, which means waste of resources and carbon dioxide emissions, and it does not comply with the concept of resource recycling. In this study, in order to explore the resource utilization pathways of expired medicines, progesterone drugs were evaluated as crude oil flow improvers as an example. The results shows that progesterone injection (PI) and progesterone capsule (PC) both act as viscosity reducer and pour point depressant in different crude oil, and 500 ppm PI and 300 ppm PC are the best dosage respectively. 500 ppm PI can reduce the viscosity of HN oil sample by 60.40%, and depress the pour point by 8.5 °C. 300 ppm PC can reduce the viscosity of HN oil by 54.7%, and depress the pour point by 10.9 °C. Furthermore, through DSC and wax crystal morphology analysis, the possible mechanism of this expired medicine as crude oil flow improver was further discussed. Finally, considering the costs of concentration, transportation, treatment, processing and other links, the possible cost of crude oil flow improver was summed up, and its market feasibility was analyzed. This study provides a reference case for the resource utilization of expired medicines.

Environmental impact of fouling for crude oil flow in preheat pipes according to oil blends

Crude oil fouling is a complex process caused by multiple mechanisms. This study examined fouling's environmental impact on a distillation unit's heating tubes and heat exchangers, proposing optimal pollution levels to reduce emissions and achieve sustainability goals. The study evaluated five crude oil blends in terms of API, sulphur, salt content, and other physical properties. Contaminated water was analyzed through biological and chemical means, while CO2, NOx, and SOx emissions were calculated from actual fuel and power consumption. Solid and sludge sediments were observed throughout all plate heat exchangers, consisting primarily of iron hydroxides and manganese oxides. Rationalizing energy use reduced the burden on the environment and fuel consumption by 7 %, with a 2 % reduction in energy needed to refine crude oil feeding units when fouling is removed after maintenance. By optimizing pollution levels and reducing energy consumption, the environmental impact of fouling can be mitigated.

Study on the slip behavior of CO2-crude oil on nanopore surfaces with different wettability

Unconventional reservoirs are characterized by a significant amount of micro and nanopores, which pose a critical challenge in accurately assessing the microscopic fluid transport behaviors to enhance oil and gas recovery in such reservoirs. CO2 injection is a promising recovery method for unconventional resources, hence the transport mechanism of CO2-crude oil at the nanoscale deserves further exploration. In this work, the flow and transport behaviors of CO2 and multicomponent crude oil in hydrophilic, neutral, and hydrophobic nanopores were investigated by the molecular dynamics simulation (MD) method. The CO2-crude oil shows a negative slip flow on hydrophilic surfaces, while it has a slip flow on neutral and hydrophobic surfaces. By illustrating the distribution structure of each component in the fluid and the solid-liquid interaction energy, the inherent causes of the slip mechanism of different wettability surfaces were revealed. The transport capacity and permeability of CO2-crude oil in the pores with different wettability were investigated. Modifying the Hagen-Poiseuille equation based on slip characteristics can effectively improve the prediction ability of nanopore permeability. This study is helpful to understand the flow and slip behavior of CO2-crude oil in nanopores of unconventional reservoirs, which provides a theoretical basis for accurately predicting the migration of reservoir fluid in nanopores.

Characterization of Asphaltene Deposition Behavior in Diluted Heavy Oil under High-Pressure Conditions

Some oil wells in the Tahe oilfield have been reported to produce extremely heavy oil due to asphaltene deposition. To enhance the flow of crude oil through the wellbore, engineers adopted the use of light oil from nearby wells to dissolve the heavy crude in the wells’ sections to maximize recovery from the Tahe oilfield. However, this mixing has led to the problem of accelerated asphaltene deposition, which often blocks the wellbore in the process. In this research, the factors that influence the stability of diluted heavy oil, temperature, and mixing ratio on asphaltene deposition characteristics under high pressure are studied using a high-temperature and high-pressure crude oil flow property experimental device based on the differential pressure method. The results under high pressure show that the initial deposition pressure of asphaltene decreases as the experimental temperature increases. With an increase in the mixing light oil ratio, the initial deposition pressure of diluted heavy oil increases, and the deposition trend of asphaltene strengthens. The asphaltene accumulation and deposition will be aggravated by filling quartz sand and pipe diameter changes. The research here is helpful to understand the deposition characteristics of asphaltene during the production of diluted heavy oil. It offers significant guidance in the prevention and control of asphaltene precipitation in heavy oil wells.

Molecular Insight into the Occurrence Characteristics of Deep Oil with Associated Gas Methane and the Displacement Resistance in Water Flooding in Nano-Pore Throat

In deep oil reservoirs, the existence of associated gas generally has a crucial impact on crude oil properties and flow performance. In this work, adopting molecular dynamic simulation, we studied the occurrence characteristics of oil with associate gas methane (the molar ratio of methane to oil rm/o were 1/4, 2/3, 3/2, and 4/1) in nano-pore throat and the displacement behavior of oil and methane in the water flooding process. Simulation results indicated: (1) an increasing replacement of the adsorption-status oil by methane as the methane content increased; (2) the oil and methane displacement efficiency was enhanced as the methane content increased in the water displacement oil and gas process; (3) the threshold displacement pressure gradually decreases as the methane content increases. The microscopic characteristics of the occurrence features and displacement performance of crude oil with associated methane in nano-pore throat were discussed in detail, and the underlying mechanism was discussed at the length concerning the interaction between different components. Our work provides an in-depth understanding of the occurrence characteristics and flow resistance of oil with associated gas in deep oil reservoirs.

Synthesis and Performance Evaluation of Graphene-Based Comb Polymer Viscosity Reducer

The high viscosity of heavy oil makes it difficult to realize its economic value. Therefore, improving the fluidity of heavy oil can effectively improve the economic benefit of the development of heavy oil resources. Oil-soluble viscosity reducers can utilize functional groups in monomers to break up asphaltene aggregates to improve the flow of crude oil. Graphene can be used to insert and split asphaltene aggregates through sliding phenomena and π–π interaction with colloidal asphaltene, thereby improving the fluidity of heavy oil. In this study, a graphene nanocomposite viscosity reducer was synthesized from lipophilic-modified graphene and a polymer viscosity reducer. The net viscosity reduction rate reached 80.0% at 400 ppm. Compared with a polymer viscosity reducer, the viscosity reduction effect of a graphene nanocomposite viscosity reducer was improved by about 7%. Structural characterization of a graphene nanocomposite viscosity reducer was characterized with infrared spectroscopy and a thermogravimetric test. The mechanism of a graphene nanocomposite viscosity reducer splitting asphaltene aggregates was verified with scanning electron microscopy. This study provides a theoretical and practical basis for the research and development of a novel nanocomposite viscosity reducer.

Crude oil differential enrichment in sandy-debris-flow and turbidite-current sandstones by physical simulation experiment

The article selected the samples of Chang 6 sandy-debris-flow and turbidite-current sandstones in the Ordos Basin and studied the seepage law and differential accumulation of crude oil by physical simulation experiment. The results show that the sandy-debris-flow and turbidite-current sandstones are featured with nonlinear and quasilinear crude oil flow with the threshold pressure gradient and critical pressure gradient. The oil saturation increases by leaps in the turbidite-current sandstones with relatively low maximum oil saturation. The sandy-debris-flow sandstones show steady growth with high maximum oil saturation. Differential accumulation of crude oil is controlled by porosity, permeability, crude oil viscosity, and hydrocarbon-generating pressure. The crude oil accumulation requires the pressure gradient to break through the critical pressure gradient, which can be formed if oil saturation exceeds 25%. Large-scale oil accumulation is easily formed in near-source sandy-debris-flow sandstones. Far-source deep-water sandstones easily develop inauthentic oil accumulation.

Investigation of nano composite heat exchanger annular pipeline flow using CFD analysis for crude oil and water characteristics

This study focuses on the dual-core annular process of crude oil and water. The crude oil exhibits non-Newtonian behavior with high viscosity. The heat transmission flow in pipeline locations is complex. In this process, the cooled water passes through the annular core, experiencing turbulence effects, while the crude oil flows in a laminar manner. The influence of the non-Newtonian behavior is investigated in terms of pipe angles and deformations. In the valve, the inlet velocity flow is set at 1.75 m/s. The flow is executed in downhill orientations in high-velocity locations. The simulation results show CFD variations with a velocity of 3.5 m/s, pressure of 2.33 MPa, pressure gradients of 1.33 MPa, and Reynolds numbers of 1.38 MPa. This study is being conducted for a horizontal pipeline. The CFD solution solvers investigate the volumetric flow characteristics of the fluid as well as the temperature effects. The maximum heat energy has been reduced, resulting in unique flow directions.

Study on Production Characteristics during N2 Flooding in Low Permeability Reservoirs: Effect of Matrix Permeability and Fracture

The N2 flooding enhanced oil recovery process is an important technical means for the development of low permeability reservoirs due to its good energy enhancement effect and good injectivity. Low permeability reservoirs have a large permeability span and strong heterogeneity, which will have a significant impact on gas injection development. In order to explore the influence of matrix permeability and fractures on the production characteristics of N2 flooding, this study conducted a series of displacement experiments with full-scale matrix permeability (0.1–50 mD) and different fracture conditions. The research results indicate that, in non-fracture low permeability cores, the pressure difference decreased with the matrix permeability increase, and the volume of N2 injection required to achieve the highest injection pressure decreased. In addition, the increase in matrix permeability accelerates the gas breakthrough and gas channeling, but is beneficial for improving no-gas oil recovery and ultimate oil recovery due to the decrease in crude oil flow resistance. The impact of different matrix permeability ranges on production characteristics varies. When the matrix permeability is less than 2 mD, the characteristics of oil and gas production are significantly affected by changes in matrix permeability. When the matrix permeability is greater than 2 mD, the impact of changes in matrix permeability on development effectiveness is weakened. The existence of fracture causes a high permeability channel to appear in the low permeability matrix, exacerbating the gas breakthrough and channeling, and significantly reducing the utilization of matrix crude oil (about a 50% decrease in oil recovery). The increase in matrix permeability is beneficial for weakening the heterogeneity between fractures and the matrix, alleviating the gas channeling, thereby increasing the swept volume in the low permeability matrix and improving oil recovery.

Corrosion fouling during crude oil flow on a heated surface: Effects of temperature, shear and material of construction

Corrosion fouling during crude oil flow on a heated surface: Effects of temperature, shear and material of construction

Compositional numerical analysis of multiphase flow of crude oil in porous media under non-isothermal conditions

Abstract The present work details the development of a compositional model to replicate the heavy hydrocarbon flow in porous reservoir systems under non-isothermal conditions. The mathematical model considers mass and energy conservation equations describing the reactive of natural variables distributed in a multiphase hydrocarbon system. Such natural variable based compositional models better suit fully implicit numerical schemes with inexpensive Jacobian matrix computations. Further, the model accommodates a switch of primary variables for the disappearance and reappearance of a phase. The resulting nonlinear conservation equations are numerically discretized using a block-centered finite-difference scheme and solved with a quasi-Newton based implicit iterative solver. The present model is validated with the thermal profiles presented in the literature for the multiphase flow during the combustion of heavy crude oil in petroleum reservoir system with performance coefficient (R 2), mean absolute error (MBE), and maximum absolute percentage error (MAPE) of about 0.954, 0.37, and 0.01 respectively. The developed compositional model projected 26 and 72 % of light and heavy oil recoveries respectively in about 160 days with a maximum or peak temperature of about 798 K. Further, the thermal and production profiles projected by the sensitivity analysis on various operating parameters are presented. It is noteworthy that the present works aid in providing an economical numerical based tool in evaluating the flow and transport during underground or in-situ combustion process for efficient energy exploration.

Key theoretical and technical issues and countermeasures for effective development of Gulong shale oil, Daqing Oilfield, NE China

Aiming at the four issues of underground storage state, exploitation mechanism, crude oil flow and efficient recovery, the key theoretical and technical issues and countermeasures for effective development of Gulong shale oil are put forward. Through key exploration and research on fluid occurrence, fluid phase change, exploitation mechanism, oil start-up mechanism, flow regime/pattern, exploitation mode and enhanced oil recovery (EOR) of shale reservoirs with different storage spaces, multi-scale occurrence states of shale oil and phase behavior of fluid in nano confined space were provided, the multi-phase, multi-scale flow mode and production mechanism with hydraulic fracture-shale bedding fracture-matrix infiltration as the core was clarified, and a multi-scale flow mathematical model and recoverable reserves evaluation method were preliminarily established. The feasibility of development mode with early energy replenishment and recovery factor of 30% was discussed. Based on these, the researches of key theories and technologies for effective development of Gulong shale oil are proposed to focus on: (1) in-situ sampling and non-destructive testing of core and fluid; (2) high-temperature, high-pressure, nano-scale laboratory simulation experiment; (3) fusion of multi-scale multi-flow regime numerical simulation technology and large-scale application software; (4) waterless (CO2) fracturing technique and the fracturing technique for increasing the vertical fracture height; (5) early energy replenishment to enhance oil recovery; (6) lifecycle technical and economic evaluation. Moreover, a series of exploitation tests should be performed on site as soon as possible to verify the theoretical understanding, optimize the exploitation mode, form supporting technologies, and provide a generalizable development model, thereby supporting and guiding the effective development and production of Gulong shale oil.

Effect of Crude Oil and Nitrogen Gas Flow Rates on the Time Taken for Flow Initiation of Waxy Crude Oil

Transportation of waxy crude oil in a production pipeline often encountered flow assurance issues, such as wax deposition. In a case where pipeline shutdown is needed, wax deposit is likely to form within the pipelines, which leads to operational complexity during the restart phase. Commonly, crude oil restarts to flow after a significantly high restart pressure is pumped longer than is necessary. This is due to the physical hindrance caused by the solid wax, which requires additional pressure to disintegrate it before achieving a steady crude oil flow. This study aims to investigate the effect of crude oil and nitrogen gas flow rates on the time taken for crude oil flow initiation using a flow loop rig, which is connected to a nitrogen gas injection system. The nitrogen gas was injected into the test section pipeline at predetermined flow rates within specified periods. After 45 min of static cooling, the crude oil gear pump is switched on to build sufficient pressure to initiate the waxy crude oil flow in the pipeline. Additionally, a statistical analysis by the response surface methodology was also performed by Minitab® 19 software. Results show that the maximum reduction in flow initiation is 73.7% at 5 L/min of crude oil and 1 L/min of nitrogen gas. This study reveals that the presence of nitrogen gas improved the pipeline restart phase by minimizing both restart pressure and time taken for flow initiation.

Application of Bio-Derived Alternatives for the Assured Flow of Waxy Crude Oil: A Review

High molecular weight paraffin/wax precipitates in the solution of crude oil when the surrounding temperature falls below the wax appearance temperature, which causes the problem of wax deposition in pipelines. To enhance the rheology of the crude oil and lessen wax deposition, pour point depressants (PPDs) and flow enhancers were utilized. These substances change the wax crystals’ morphology, reducing crystal interlocking and preventing wax agglomeration from facilitating wax dispersion. However, recent research prompted a further investigation to improve the performance of conventional polymeric PPD and to address wax accumulation in a safe and environmentally responsible way. This is because of their poor performance at high shearing, expensive preparations, limited biodegradability, and toxicity. The primary objective of this study is to provide a thorough summary of current studies on the use of seed oil extracts rich in unsaturated fatty acids as an alternative for polymeric PPD. Important studies on the use of nanoparticles to improve the performance of conventional PPD, as well as strategies put into place to overcome issues with nanoparticle application, are also highlighted. Finally, an outlook of potential research ideas to develop pour point depressants is provided.

Research on non-Newtonian characteristics of crude oil flow at micro-nano scale

The characteristic scale of flow in micro–nanochannels is generally in the range of 0.01 μm∼1 μm. When crude oil passes through micro-nano channels and tight reservoirs, it shows obvious nonlinear seepage characteristics, which does not conform to the continuity assumption of fluid. Therefore, a non-Newtonian model of crude oil flowing in micro-nano channels and tight reservoirs under the action of shear stress is established, and the relationship between flow rate and apparent viscosity and shear rate is analyzed. The experiment of crude oil flow in micro-nano channels and tight oil reservoir cores shows that the model can be used to describe the nonlinear seepage law of liquid through the nonlinear fitting. The power law index of the oil-phase power-law non-Newtonian fluid is greater than 1 at the micro-nano scale, which conforms to the flow characteristics of the expansive fluid, thus verifying the effectiveness of the non-Newtonian model. In addition, the study of apparent viscosity and shear rate of non-Newtonian fluid shows that the increasing and decreasing trends of flow rate and shear rate and the changing trends of flow rate and pressure gradient are consistent, and shear rate can be used to describe the characteristics of fluid instead of the pressure gradient.

The effect of polyethylene butene (PEB) and xylene on the shear stress of Niger delta crude oil

Crude oil production and transportation is plagued by several flow assurance issues especially in offshore environment with prevailing low temperature. One of the flow assurance challenges is the deposition of paraffin wax which usually changes the crude oil flow from Newtonian fluid flow to non- Newtonian fluid flow with increased viscosity. This increased viscosity can impede flow causing the installation of high horsepower pumps for fluid flow. In severe cases, paraffin wax has plugged the pipes and caused production disruption. It is therefore imperative to manage paraffin disposition in crude samples containing paraffin compounds (C18+). This research discusses the use of varying concentrations of Polyethylene Butene (PEB) in managing wax precipitation at various temperatures (10 °C to 35 °C) at a constant shear rate of 511(s-1). The reduction in crude oil temperature increased the shear stress in all experiments conducted. It was discovered that the increasing concentration of PEB from 500ppm to 5000ppm had a sinusoidal effect on reducing the shear stress. 500ppm of PEB effected a 19% reduction in shear stress, while 5000ppm effected a 35% reduction in shear stress. It is important for the engineer to make the choice of inhibitor concentration based on the degree of shear stress reduction required to optimize inhibitor usage.