Search Results (12)

Due to the significance of carbon utilization and storage, CO₂ huff and puff is increasingly receiving attention. However, the mechanisms and effects of CO₂ huff and puff extraction in medium to deep saturated heavy oil reservoirs remain unclear. Therefore, in this study, by targeting the medium to deep saturated heavy oil reservoirs in the block Xia of the Xinjiang oil field, measurements of physical properties were conducted through PVT analysis and viscosity measurement to explore the dissolution and diffusion characteristics of CO₂-degassed and CO₂-saturated oil systems. Multiple sets of physical simulation of CO₂ huff and puff in medium to deep saturated heavy oil reservoirs were conducted using a one-dimensional core holder to evaluate the EOR mechanism of CO₂ huff and puff. The results demonstrate that the solubility of CO₂ in degassed crude oil is linearly correlated with pressure. Higher pressure effectively increases the solubility of CO₂, reaching 49.1 m³/m³ at a saturation pressure of 10.0 MPa, thus facilitating oil expansion and viscosity reduction. Meanwhile, crude oil saturated with CH₄ still retains the capacity to further dissolve additional CO₂, reaching 24.5 m³/m³ of incremental CO₂ solubilization at 10.0 MPa, and the hybrid effect of CO₂ and CH₄ reduces oil viscosity to 1161 mPa·s, which is slightly lower than the pure CO₂ dissolution case. Temperature increases suppress solubility but promote molecular diffusion, allowing CH₄ and CO₂ to maintain a certain solubility at high temperatures. In terms of dynamic dissolution and diffusion, the initial CO₂ dissolution rate is high, reaching 0.009 m³/(m³·min), the mid-term dissolution rate stabilizes at approximately 0.002 m³/(m³·min), and the dissolution capability significantly decreases later on. CO₂ exhibits high molecular diffusion capability in gas-saturated crude oil, with a diffusion coefficient of 8.62 × 10⁻⁷ m²/s. For CO₂ huff and puff, oil production is positively correlated with the CO₂ injection rate and the cycle injection volume; it initially increases with the extension of the soak time but eventually decreases. Therefore, the optimal injection speed, injection volume, and soak time should be determined in conjunction with reservoir characteristics. During the huff and puff process, the bottom hole pressure should be higher than the bubble point pressure of the crude oil to prevent gas escape. Moreover, as the huff and puff cycles increase, the content of saturates in the oil rises, while those of aromatic, resin, and asphaltene decrease, leading to a gradual deterioration of the huff and puff effect. This study provides a comprehensive reference method and conclusions for studying the fluid property changes and enhanced recovery mechanisms in medium to deep heavy oil reservoirs with CO₂ huff and puff. Full article

With the growing demand for plastic production and the importance of plastic recycling, new approaches to plastic waste management are required. Most of the plastic waste is not biodegradable and requires remodeling treatment methods. Chemical recycling has great potential as a method of waste treatment. Plastic pyrolysis allows for the cracking of plastic polymers into monomers with heat in the absence of oxygen, allowing energy recovery from the waste. Fluidized bed reactors are commonly used in plastic pyrolysis; they have excellent heat and mass transfer. This study investigates the influence of low and medium process temperatures of pyrolysis on fluidized bed reactor parameters such as static pressure, fluidizing gas velocity, solid movement, and bubble formation. This set of parameters was analyzed using experimental methods and statistical analysis methods such as experimental correlations of changes in fluidized bed reactor velocities (minimal, terminal) due to temperature increases for different particle sizes; CFD software simulation of temperature impact was not found. In this study, computational fluid dynamics (CFD) analysis with Ansys Fluent was conducted for the fluidization regime with heat impact analysis in a fluidized bed reactor (FBR). FBR has excellent heat and mass transfer and can be used with a catalyst with low operating costs. A two-phase Eulerian–Eulerian model with transient analysis was conducted for a no-energy equation and at 100 °C, 500 °C, and 700 °C operating conditions. Fluidizing gas velocity increases the magnitude with an increase of the operating temperature. The point of fluidization could be determined at 1.1–1.2 s flow time at the maximum pressure drop point. With the increase of gas velocity (to 0.5 m/s from 0.25 m/s), fluidizing bed height expands but when the solid diameter is increased from 1.5 mm to 3 mm, the length of the fluidized region decreases. No pressure drop change was observed as the fluidized bed regime was maintained during all analyses. The fluidization regime depends on gas velocity and all the applied fluidization gas velocities were of a value in between the minimal fluidization velocity and the terminal velocity. Full article

The existence of propane (C₃H₈) in a CO₂-oil mixture has great potential for increasing CO₂ solubility and decreasing minimum miscibility pressure (MMP). In this study, the enhanced solubility, reduced viscosity, and lowered MMP of CO₂-saturated crude oil in the presence of various amounts of C₃H₈ have been systematically examined at the reservoir conditions. Experimentally, a piston-equipped pressure/volume/temperature (PVT) cell is first validated by accurately reproducing the bubble-point pressures of the pure component of C₃H₈ at temperatures of 30, 40, and 50 °C with both continuous and stepwise depressurization methods. The validated cell is well utilized to measure the saturation pressures of the CO₂-C₃H₈-oil systems by identifying the turning point on a P-V diagram at a given temperature. Accordingly, the gas solubilities of a CO₂, C₃H₈, and CO₂-C₃H₈ mixture in crude oil at pressures up to 1600 psi and a temperature range of 25–50 °C are measured. In addition, the viscosity of gas-saturated crude oil in a single liquid phase is measured using an in-line viscometer, where the pressure is maintained to be higher than its saturation pressure. Theoretically, a modified Peng–Robinson equation of state (PR EOS) is utilized as the primary thermodynamic model in this work. The crude oil is characterized as both a single and multiple pseudo-component(s). An exponential distribution function, together with a logarithm-type lumping method, is applied to characterize the crude oil. Two linear binary interaction parameters (BIP) correlations have been developed for CO₂-oil binaries and C₃H₈-oil binaries to accurately reproduce the measured saturation pressures. Moreover, the MMPs of the CO₂-oil mixture in the presence and absence of C₃H₈ have been determined with the assistance of the tie-line method. It has been found that the developed mathematical model can accurately calculate the saturation pressures of C₃H₈ and/or CO₂-oil systems with an absolute average relative deviation (AARD) of 2.39% for 12 feed experiments. Compared to CO₂, it is demonstrated that C₃H₈ is more soluble in the crude oil at the given pressure and temperature. The viscosity of gas-saturated crude oil can decrease from 9.50 cP to 1.89 cP and the averaged MMP from 1490 psi to 1160 psi at 50 °C with the addition of an average 16.02 mol% C₃H₈ in the CO₂-oil mixture. Full article

In this work, we investigate the effect of dissolved gas concentration on cavitation inception and cavitation development in a transparent sharp-edged orifice, similar to that previously analyzed by Nurick in the context of liquid injectors. The working liquid is water, and carbon dioxide is employed as a non-condensable dissolved gas. Cavitation inception points are determined for different dissolved gas concentration levels by measuring wall-static pressures just downstream of the orifice contraction and visually observing the onset of a localized (vapor) bubble cloud formation and collapse. Cavitation onset correlates with a plateau in wall-static pressure measurements as a function of a cavitation number. An increase in the amount of dissolved carbon dioxide is found to increase the cavitation number at which the onset of cavitation occurs. The transition from cloud cavitation to extended-sheet or full cavitation along the entire orifice length occurs suddenly and is shifted to higher cavitation numbers with increasing dissolved gas content. Volume flow rate measurements are performed to determine the change in the discharge coefficient with the cavitation number and dissolved gas content for the investigated cases. CFD analyses are carried out based on the cavitation model by Zwart et al. and the model by Yang et al. to account for non-condensable gases. Discharge coefficients obtained from the numerical simulations are in good agreement with experimental values, although they are slightly higher in the cavitating case. The earlier onset of fluid cavitation (i.e., cavitation inception at higher cavitation numbers) with increasing dissolved carbon dioxide content is not predicted using the employed numerical model. Full article

It is well recognized that PVT data are essential in oil and gas production facilities as well as in the determination of the reservoir fluid composition in reservoir engineering calculations. In the current work, the studied borehole is located in Tawke oilfield in the High Folded Zone. The structural geology and lithological facies of rocks are studied and found to comprise fine crystalline dolomite and anhydrite interbedded with claystone and dolomite. In addition, the practical PVT data of black oil from Tawke oilfield, Zakho, from reservoirs to transgressive–regressive cycles, are studied. The PVT data are investigated to derive the empirical models that rule and correlate the properties of the reservoir fluids in terms of the amount of natural gas (methane, ethane, and propane) dissolved in reservoir fluids and evolving from the wells. The characteristics of the reservoir fluid, including °API, viscosity at reservoir pressure and bubble-point pressure, reservoir pressure and temperature, gas–oil ratio (GOR), coefficient of compressibility at reservoir pressure, gross heating value, and sample depth, are correlated. The lithological part reveals that the carbonate and some clastic rock facies are conducive to enhancing natural gas adsorption. The reservoir fluid properties show adverse effects on the amount of natural gas constituents evolving from the wells, while it shows positive effects on the dissolved reservoir fluids. The estimated empirical correlations can help indicate the quantity of natural gas that is dissolved in reservoir fluids and liberated from the wells depending on the characteristics of the reservoir. In addition, they can be used in numerical simulators to predict oil well performance. Full article

Turbulence and pressure fluctuations are key elements in the bed protection design of hydraulic structures. However, their roles in a hydraulic jump are not yet fully understood, and the nature of their relationships are not conclusive. In order to better understand the relationships between pressure fluctuations and flow characteristics of a hydraulic jump downstream of a weir, detailed measurements of flow kinematics using the nonintrusive techniques of particle image velocimetry and bubble image velocimetry and pressure using voltage-type pressure gauges were carried out in this study. The physical modeling of the hydraulic jump was carried out using the simultaneous measurements of pressure and turbulent flow properties. The distributions of flow properties, such as water level and velocity, were assessed in each case. Based on the measurements, the correlations between the pressure fluctuations and the variables were investigated by coupling the statistical values of the variables at the same points. The analysis results show that the water level and turbulence intensity are the main factors influencing the pressure fluctuations in the hydraulic jump. Using these factors, an empirical formula and dimensionless numbers are proposed to show that the pressure fluctuations depend on the bubble flow behavior. Full article

Gas-lift dual gradient drilling (DGD) is a solution for the complex problems caused by narrow drilling windows in deepwater drilling. Investigations are lacking on using oil-based drilling fluid in DGD, which is the principal novel idea of the present study. This research compares the results obtained from two new models with those of Standing’s correlations for solubility and bubble point pressure. Nitrogen was selected as the injection gas, then the PVT behavior of drilling fluid (oil/water/Nitrogen) in gas-lift DGD was evaluated and compared by coding in MATLAB. Then, these results were used to calculate the bottom hole pressure and finally investigate the optimization of injected gas flow rate. According to the achieved results, the Standing model has some errors in evaluating the PVT behavior of “Nitrogen and oil-based drilling fluids” and is not recommended for the mixtures in the gas-lift DGD. Regarding optimizing gas flow rate, a discrepancy was observed between pressure values obtained from the new models and the Standing model for the case of high liquid flow rates at low gas flow rates because of the difference in PVT parameters. The developed codes are deposited on an online data repository for future users. This study lays the foundation for better planning of drilling in deepwater drilling projects. Full article

Recently, the trend towards sustainable energy production and pollution control has motivated the increased consumption of ultra-low-sulfur diesel (ULSD) or bio-fuels. Such fuels have relatively low surface tension with water and therefore, the separation of water from fuel has become a challenging problem. The separation process relies on using porous structures for the collection and removal of water droplets. Hence, understanding the interaction between water droplets and the separators is vital. The simplest geometry of a separator is the wire mesh screen, which is used in many modern water–diesel separators. Thus, it is considered here for systematic study. In this work, pore-scale computational fluid dynamics (CFD) simulations were performed using OpenFOAM^® (an open-source C++ toolbox for fluid dynamics simulations) coupled with a new accurate scheme for the computation of the surface tension force. First, two validation test cases were performed and compared to experimental observations in corresponding bubble-point tests. Second, in order to describe the interaction between water droplets and wire mesh screens, the simulations were performed with different parameters: mean diesel velocity, open area ratio, fiber radii, Young–Laplace contact angle, and the droplet radius. New correlations were obtained which describe the average reduction of open surface area (clogging), the pressure drop, and retention criteria. Full article

Accurate estimation of crude oil Bubble Point Pressure (Pb) plays a vital rule in the development cycle of an oil field. Bubble point pressure is required in many petroleum engineering calculations such as reserves estimation, material balance, reservoir simulation, production equipment design, and optimization of well performance. Additionally, bubble point pressure is a key input parameter in most oil property correlations. Thus, an error in a bubble point pressure estimate will definitely propagate additional error in the prediction of other oil properties. Accordingly, many bubble point pressure correlations have been developed in the literature. However, they often lack accuracy, especially when applied for global crude oil data, due to the fact that they are either developed using a limited range of independent variables or developed for a specific geographic location (i.e., specific crude oil composition). This research presents a utilization of the state-of-the-art Bayesian optimized Least Square Gradient Boosting Ensemble (LS-Boost) to predict bubble point
pressure as a function of readily available field data. The proposed model was trained on a global crude oil database which contains (4800) experimentally measured, Pressure–Volume–Temperature (PVT) data sets of a diverse collection of crude oil mixtures from different oil fields in the North
Sea, Africa, Asia, Middle East, and South and North America. Furthermore, an independent (775) PVT data set, which was collected from open literature, was used to investigate the effectiveness of the proposed model to predict the bubble point pressure from data that were not used during the model development process. The accuracy of the proposed model was compared to several published correlations (13 in total for both parametric and non-parametric models) as well as two other machine learning techniques, Multi-Layer Perceptron Neural Networks (MPL-ANN) and Support Vector Machines (SVM). The proposed LS-Boost model showed superior performance and
remarkably outperformed all bubble point pressure models considered in this study. Full article

Cavitation will cause abnormal flow, causing a series of problems such as vibration, noise, and erosion of solid surfaces. In severe cases, it may even destroy the entire system. Cavitation is a key problem to be solved for hydraulic machinery and underwater robots, and the attack angle is one of the most important factors affecting the cavitation. In order to systematically study the impact of the attack angle on the hydrofoil cavitation, the hydrofoils of NACA 4412 with different attack angles were selected to study the collapse process and hydraulic characteristics such as pressure, velocity, vortex, and turbulent kinetic energy during cavitation. The results showed that when the cavitation number was the same, the process of cavity collapse was greatly affected by the attack angle. The length of the cavity collapse area was positively correlated with the attack angle. As the attack angle increased, the volume of the falling bubbles increased, resulting in a larger pressure peak caused by the collapse of bubbles. Moreover, the pressure gradient near the collapse point changed more drastically, thereby affecting the growth of attached cavitation. The fluctuation range of vortex core and turbulent kinetic energy also increased with increasing the attack angle. Full article

Reservoir fluid properties such as bubble point pressure (Pb) and gas solubility (Rs) play a vital role in reservoir management and reservoir simulation. In addition, they affect the design of the production system. Pb and Rs can be obtained from laboratory experiments by taking a sample at the wellhead or from the reservoir under downhole conditions. However, this process is time-consuming and very costly. To overcome these challenges, empirical correlations and artificial intelligence (AI) models can be applied to obtain these properties. The objective of this paper is to introduce new empirical correlations to estimate Pb and Rs based on three input parameters—reservoir temperature and oil and gas gravities. 760 data points were collected from different sources to build new AI models for Pb and Rs. The new empirical correlations were developed by integrating artificial neural network (ANN) with a modified self-adaptive differential evolution algorithm to introduce a hybrid self-adaptive artificial neural network (SaDE-ANN) model. The results obtained confirmed the accuracy of the developed SaDE-ANN models to predict the Pb and Rs of crude oils. This is the first technique that can be used to predict Rs and Pb based on three input parameters only. The developed empirical correlation for Pb predicts the Pb with a correlation coefficient (CC) of 0.99 and an average absolute percentage error (AAPE) of 6%. The same results were obtained for Rs, where the new empirical correlation predicts the Rs with a coefficient of determination (R²) of 0.99 and an AAPE of less than 6%. The developed technique will help reservoir and production engineers to better understand and manage reservoirs. No additional or special software is required to run the developed technique. Full article

Oil production by natural energy of the reservoir is usually the first choice for oil reservoir development. Conversely, to effectively develop tight oil reservoir is challenging due to its ultra-low formation permeability. A novel platform for experimental investigation of oil recovery from tight sandstone oil reservoirs by pressure depletion has been proposed in this paper. A series of experiments were conducted to evaluate the effects of pressure depletion degree, pressure depletion rate, reservoir temperature, overburden pressure, formation pressure coefficient and crude oil properties on oil recovery by reservoir pressure depletion. In addition, the characteristics of pressure propagation during the reservoir depletion process were monitored and studied. The experimental results showed that oil recovery factor positively correlated with pressure depletion degree when reservoir pressure was above the bubble point pressure. Moreover, equal pressure depletion degree led to the same oil recovery factor regardless of different pressure depletion rate. However, it was noticed that faster pressure drop resulted in a higher oil recovery rate. For oil reservoir without dissolved gas (dead oil), oil recovery was 2–3% due to the limited reservoir natural energy. In contrast, depletion from live oil reservoir resulted in an increased recovery rate ranging from 11% to 18% due to the presence of dissolved gas. This is attributed to the fact that when reservoir pressure drops below the bubble point pressure, the dissolved gas expands and pushes the oil out of the rock pore spaces which significantly improves the oil recovery. From the pressure propagation curve, the reason for improved oil recovery is that when the reservoir pressure is lower than the bubble point pressure, the dissolved gas constantly separates and provides additional pressure gradient to displace oil. The present study will help engineers to have a better understanding of the drive mechanisms and influencing factors that affect development of tight oil reservoirs, especially for predicting oil recovery by reservoir pressure depletion. Full article