Stage Cut Research Articles

Study of Displacement Characteristics of Fire Flooding in Different Viscosity Heavy Oil Reservoirs

A field test in the Xinjiang oilfield in China shows that the viscosity of heavy oil has a certain influence on the combustion dynamics and injection-production performance of fire flooding. The experiment in this study uses a one-dimensional combustion tube to study the temperature, gas composition, and air injection pressure and the production performance of the fire flooding of heavy oil with different viscosities. The results show that the oil viscosities of 1180–22500 mPa·s can achieve stable combustion, and the O2 content of the gas produced during the stable combustion stage is <0.5%. The higher the viscosity of the heavy oil, the higher the temperature in the burned zone and the smaller the range of the temperature increase in the unburned zone. The air injection pressure will increase rapidly until a stable seepage channel is formed, and then, it will drop to a level close to the formation pressure. High-viscosity heavy oil requires a higher air injection pressure and will remain in the high-pressure stage for a longer period of time. Low-viscosity heavy oil has a low water cut in the early stage of fire flooding, a large oil production rate, and a low and stable air–oil ratio. The water cut of high-viscosity heavy oil increases rapidly in the early stage of fire flooding and then decreases gradually, so a good air–oil ratio can only be obtained in the middle and late stages of fire flooding. Thus, fire flooding may be more suitable for application in common heavy oil and some extra heavy oil reservoirs with lower viscosities.

Study on characterization model of relative permeability based on three parameter Weibull model

Aiming at the problem of large error between relative permeability and water cut in high water cut and low water cut stage. A large number of experiments show that there is a good linear relationship between the double logarithm of water saturation and the logarithm of oil-water relative permeability ratio. On this basis, the three parameter Weibull model is applied to establish a new characterization model of relative permeability. The calculation results of two examples show that the calculated values of the new model are all close to the actual values in low water cut, medium water cut and high water cut stages, and the accuracy is high. This study provides a basis for improving the accuracy of reservoir engineering scheme design and reservoir numerical simulation.

Multicomponent Spiral Wound Membrane Separation Model for CO2 Removal from Natural Gas.

A spiral wound membrane (SWM) is employed to separate acid gases (mainly CO2) from natural gas due to its robustness, lower manufacturing cost, and moderate packing density compared to hollow fiber membranes. Various mathematical models are available to describe the separation performance of SWMs under different operating conditions. Nevertheless, most of the mathematical models deal with only binary gas mixtures (CO2 and CH4) that may lead to an inaccurate assessment of separation performance of multicomponent natural gas mixtures. This work is aimed to develop an SWM separation model for multicomponent natural gas mixtures. The succession stage method is employed to discretize the separation process within the multicomponent SWM module for evaluating the product purity, hydrocarbon loss, stage cut, and permeate acid gas composition. Our results suggest that multicomponent systems tend to generate higher product purity, lower hydrocarbon loss, and augmented permeate acid gas composition compared to the binary system. Furthermore, different multicomponent systems yield varied separation performances depending on the component of the acid gas. The developed multicomponent SWM separation model has the potential to design and optimize the spiral wound membrane system for industrial application.

Investigation of Cut Control Equations in the Gas Centrifuge Cascades

Stage cut control and simulation are the most important aspects in the optimum binary mixture or multi-component multiobjective cascades. Numerical investigation revealed that by controlling the cut of a separation cascade, defined as the ratio of the product rate to the feed rate, it is always possible to separate a multi-component mixture into two specified groups of components, a light group, and a heavy group, in just one separation run. In this paper, the equations related to the cut control are introduced and it is proposed that for controlling stage cuts, putting one valve in the product section of each stage is enough. By solving the set of non-linear equations related to the machine behavior, valve, and pressure drop in the pipelines and junctions, the valve setting for each stage can be obtained. In the end, some examples of an optimal cascade are studied and valve setting parameters are obtained.

Removal of sulfur‐containing compounds from Fluid Catalytic Cracking unit (FCC) gasoline by pervaporation process: Effects of variations in feed characteristics and mass transfer properties of the membrane

AbstractAnalyzing the effects of feed characteristics and membrane transport properties are important for designing the industrial‐scale pervaporative desulfurization plants. In this study, a new method to analyze the effects of feed composition and membrane characteristics has been proposed, where these properties are represented by average vapor pressure and average permeance coefficient. Spiral wound module geometry is used in this study for more realistic industrial‐scale predictions. Results suggested that module performance in terms of stage cut and enrichment factor improved with increasing selectivity of the membrane. However, this effect was profound at lower selectivity (<5) and became negligible at higher selectivity (>10). Moreover, results also depicted that the increase in feed temperature increased enrichment factor when selectivity was low (<2.5), but this trend was reversed when selectivity was greater than 2.5. At a constant membrane selectivity, an increase in permeability reduced the enrichment factor. Thus, membrane selectivity should improve along with membrane permeability for better results. The pervaporation process was found more beneficial for removing highly volatile low molecular weight sulfur‐containing compounds. Finally, feed channel temperature drop and permeate channel pressure drop followed the trend of stage cut in all simulations. Therefore, the lower stage cut may improve module efficiency.

Research on Sand Body Description and Perforation Plan Optimization of Off-surface Reservoir in Block a of X Oilfield

Based on the previous understanding of off-surface reservoirs of closed coring wells in Block B of X Oilfield, this paper selects the “four injection and nine production” test well group in Block A as the research object, and studies the distribution characteristics of dominant bands in off-surface sand bodies. The results show that the off-balance-sheet reservoirs can be vertically subdivided into two types and seven sub-types of sand body connectivity patterns, and the understanding of sand body connectivity is deepened by finely depicting sedimentary facies belts on the plane. On the basis of the above research, according to the sedimentary environment and distribution characteristics of the dominant zones, the perforation scheme of the tertiary infill wells is further optimized, and the three principles of “no shooting in the inner front, type I and II selective shooting in the outer front, and type III and IV full shooting in the outer front” are defined, which provides a new research direction for effectively controlling the rapid rise of water cut in the initial stage of new wells and further tapping the potential of the off surface remaining oil.

Heat and mass transfer modeling of an energy efficient Hybrid Membrane-Based Air Conditioning System for humid climates

In this work, a mathematical model was made for a Hybrid Membrane-Based Air Conditioning System to evaluate the performance of the proposed system. The hybrid system consisted of a cross-flow membrane air dehumidifier unit and a membrane contactor unit as humidifier. The model was further validated using simulation and experimental data from the literature. The effects of the parameters such as dehumidifier stage cut, pressure ratio and humidifier geometry were studied. Then, the performance of the system was evaluated in terms of sensible, latent and total cooling capacity and latent heat ratio. The hybrid system produced fresh air with minimum temperature of 13.5 °C and humidity ratio below 12 g/kg providing a thermal comfort condition for human activities. Also, the results showed that the maximum total cooling capacity was 3.3 kW when the dehumidifier pressure ratio was 20, and LHR of the hybrid system was in the range 0.35–0.63. The results also showed that the membrane air-conditioner had a low energy consumption, saving energy up to 66% in comparison to the conventional air-conditioners. The proposed membrane air-conditioner is capable to operate in a wide range of humidity in the Persian Gulf region, while maintaining the thermal comfort conditions.

Trends in neoadjuvant chemotherapy versus surgery-first in stage I HER2-positive breast cancer patients in the National Cancer DataBase (NCDB).

Neoadjuvant chemotherapy (NAC) is the standard of care for locally advanced HER2 + breast cancer (BC). Optimal sequencing of treatment (NAC vs. surgery first) is less clear cut in stage I (T1N0) HER2 + BC, where information from surgical pathology could impact adjuvant treatment decisions. Utilizing the NCDB, we evaluated the trend of NAC use compared to upfront surgery in patients with small HER2 + BC. We identified NCDB female patients diagnosed with T1 N0 HER2 + BC from 2010 through 2015. Prevalence ratios (PR) using multivariable robust Poisson regression models were calculated to measure the association between baseline characteristics and the receipt of NAC. Analysis of trends over time was denoted by annual percent change (APC) of NAC versus surgery upfront. Of the 14,949 that received chemotherapy and anti-HER2 therapy during the study period, overall 1281 (8.6%) received NAC and 13,668 (91.4%) received adjuvant treatment. Patients receiving NAC increased annually from 4.2% in 2010 to 17.3% in 2015, with the most rapid increase occurring between years 2013 (8.5%) and 2014 (14.2%). The greatest increase was seen in patients with cT1c tumors with an APC of 37.8% over the study period (95% CI 29.0, 47.3%, p < 0.01), although a significant trend was likewise seen in patients with cT1a (APC = 26.1%,95% CI 1.59, 56.6%), and cT1b (APC = 27.4%, 95% CI 18.0, 37.7%) tumors. Predictors of neoadjuvant therapy receipt were age younger than 50 (PR = 1.69, 95% CI 1.52, 1.89), Mountain/Pacific area (PR = 1.24, 95% CI 1.05, 1.46), and estrogen receptor negativity (ER- PR + : PR = 2.01, 95% CI 1.51, 2.68; ER- PR- : PR = 1.49, 95% CI 1.32, 1.69). Neoadjuvant therapy for T1 N0 HER2 + BC increased over the study period and was mostly due increased use in clinical T1c tumors. This may be consistent with secular change in Pertuzumab treatment following FDA approval in 2013.

Design of nanofiltration cascades for fructooligosaccharides using the McCabe-Thiele approach

We developed a design method for an inhomogeneous membrane cascade by adopting the McCabe-Thiele method, which is long established for designing distillation columns. The stage cut value is an independent design parameter in the design procedure and thus has to be set. Within each section, the operating conditions were uniform, but both sections could be operated differently using various combinations of membranes, trans-membrane pressure, temperature and stage cut. The procedure was applied to cascaded nanofiltration for the fractionation of a mixture of fructooligosaccharides of varying molecular weight. The stage and area requirements were strongly dependent on the initial design parameter, the overall stage cut. The total area was related to the overall system cut. However, the overall system cut was dependent on the stage cuts for both sections (top and bottom). The top stage cut could be chosen, whereas the bottom stage cut needed to be calculated iteratively to match the top design at the intersection.

Industrial application of ceramic nanofiltration membranes for water treatment in oil sands mines

A commercial titania ceramic nanofiltration membrane unit with a permeate flow capacity of 20 m3/h was used to reduce ion concentration, Total Suspended Solids (TSS) and Total Organic Carbon (TOC) in recycle water from a Canadian oil sands mine. This unit, the first of its kind, was tested for almost two years to evaluate membrane performance under actual recycle process water conditions. This paper focuses on the results at a 50% stage cut. A strong correlation between specific flux and rejection was found, with the highest mass rejections observed at the lowest specific flux values. A potential formation of a cake layer on the membrane surface seems to favour the rejection since lower specific flux values improved mass rejection. The analysis of more than 20 ions showed that differences in hydrated ionic sizes and electrostatic phenomena are at play with divalent cations showing the largest rejection. Additional 75–90% TOC and almost 100% TSS rejection was observed. These results indicate that it is possible to implement this technology in an oil sands mine and obtain significant water quality improvements and reducing river water intake.

Modeling and simulation of gas separations with spiral‐wound membranes

AbstractModels for gas separations with spiral‐wound membranes are developed and found to exhibit good agreement with experiments performed on N2/O2 mixtures. The two‐dimensional (2D) model can be accurately approximated by a one‐dimensional (1D) surrogate model when the spacer widths are chosen to make the channel pressure drops small. Subsequently, the separation of propane/propylene mixtures from the recycle purge stream of a polypropylene reactor is investigated. Assuming ideal gas is found to lead to significant overestimations in membrane stage cuts (sometimes more than 10%), an extent comparable to that associated with extrapolating constant olefin permeance from a low‐pressure condition. While olefin permeance can change significantly with pressure, using a constant‐permeance formulation can result in a small (&lt; 2.5%) underprediction in stage cut if the value for the permeance is taken from the feed condition. Finally, membrane properties and costs necessary for a viable separation process are discussed.

Efficiency Separation Process of H2/CO2/CH4 Mixtures by a Hollow Fiber Dual Membrane Separator

Hydrogen purification and CO2 capture are of great significance in refineries and pre-combustion power plants. A dual membrane separator offers an alternative approach for improving H2/CO2 separation efficiency. In this work, H2/CO2/CH4 ternary gas mixtures separation can be achieved by a dual membrane separator with an integrated polyimide (PI) membrane and polydimethylsiloxane/polyetherimide (PDMS/PEI) composite membrane. A hollow fiber dual membrane separation equipment is designed and manufactured. Through the self-designed device, the effects of stage cut, operating temperature, operating pressure, and membrane area ratio on separation performance of dual membrane separator have been studied. The results indicate that, at a high stage cut, a dual membrane separator has obvious advantages over a single membrane separator. Operating temperature has a significant impact on gas permeation rates. At 25 °C, a dual membrane separator can obtain the highest purity of H2 and CO2. By increasing operating pressure, the purity and recovery of H2 and CO2 can be improved simultaneously. The effect of the membrane area ratio on the performance of the dual membrane separator was studied. When the permeate flows of two membranes are approximately equal by changing the membrane area ratio, the overall performance of the dual membrane separator is the best. On the basis of its synergy in promoting separation, the dual membrane separator holds great industrial application potential.

Simulation for CO2 capture using tubular dual-phase membrane module

Dual-phase membrane is a newly developed membrane that is capable of capturing carbon dioxide (CO2) from flue gas at high temperature up to 823 K. To date, the researches on CO2 capture using dual-phase membrane are performed experimentally. However, the gas separation performance of the scale-up tubular dual-phase membrane module is scarcely studied. Therefore, the potential application of the dual-phase membrane module remains as a challenge. The design of membrane module and its implementation in actual operating conditions can be analyzed beforehand by using Computational Fluid Dynamics (CFD) simulation. In this paper, the hydrodynamic profile of the gas flowing inside a tubular dual-phase membrane module was studied to investigate its potential for industrial application. CFD simulation of gas mixture consisting of CO2 and nitrogen (N2) that flowing through the membrane module was performed at 823 K. Among the parameters investigated are the absolute pressure, concentration of CO2 and gas velocity within the tubular membrane module. The inlet mass flow rate was set at 0.00448 kg s−1 and the total volume of the membrane module was 0.031 m3. Based on the simulation, 0.09 bar of pressure drop was observed when the feed gas stream passed across the membrane zone to the outlet zone. There was about 86 % of CO2 recovery with the CO2 concentration decreased from 20 mol % to 3.3 mol %. Besides, the membrane stage cut was around 0.17 with 83 % of the gas leaving the membrane module at the retentate side. The simulation results give reliable statement over the separation efficiency of CO2 and flow pattern in membrane module. The scale-up performance of single membrane module has been predicted through the simulation based on the experimental data.

A hybrid batch distillation/membrane process for high purification part 1: Energy efficiency and separation performance study for light impurities removal

High purification processes are usually characterized by high energy demand and unavoidable losses of a purified substance during removal of trace impurities. An unsteady-state hybrid separation method based on a batch distillation with integrated membrane gas separation was studied for high purification of liquefied gases. The performance of a hybrid process versus a standalone batch distillation was analyzed through simulations and experiments for the case of light impurities removal from ammonia. A model of a middle-vessel batch distillation column was built in Aspen Plus Dynamics™ with an integrated hollow fiber membrane model implemented in Aspen Custom Modeler™. The results of batch distillation simulations are validated against the experimental data. Among the considered aspects are the hydrodynamics study, the effect of operating conditions on column separation performance, and the dynamics of the purification process. The simulations were done at a varied impurity cut withdrawal rate, membrane area, stage cut, and membrane selectivity taking into account the effective (mixed gases) selectivity data for ammonia/impurity systems available in the open literature. The possibility of both reducing the total energy input and improving the product recovery is shown for a hybrid purification process involving the separation of the withdrawn impurity cut in a membrane module with recycling of the purified component back to the distillation column.

Process Design Characteristics of Syngas (CO/H2) Separation Using Composite Membrane

The effectiveness of gas separation membranes and their application is continually growing owing to its simpler separation methods. In addition, their application is increasing for the separation of syngas (CO and H2) which utilizes cryogenic temperature during separation. Polymers are widely used as membrane material for performing the separation of various gaseous mixtures due to their attractive perm-selective properties and high processability. This study, therefore, aims to investigate the process design characteristics of syngas separation utilizing polyamide composite membrane with polyimide support. Moreover, characteristics of CO/H2 separation were investigated by varying inlet gas flow rates, stage cut, inlet gas pressures, and membrane module temperature. Beneficial impact in CO and H2 purity were obtained on increasing the flow rate with no significant effect of increasing membrane module temperature and approximately 97% pure CO was obtained from the third stage of the multi-stage membrane system.

Downregulation of homeodomain protein Cut is essential for Drosophila follicle maturation and ovulation.

Proper development and maturation of a follicle is essential for successful ovulation and reproduction; however, the molecular mechanisms for follicle maturation, particularly for somatic follicle cell differentiation, are poorly understood. During Drosophila oogenesis, the somatic follicle cells encasing oocytes undergo two distinct well-established transitions: the mitotic to endocycle switch at stage 6/7 and the endocycle to gene amplification switch at stage10A/10B. Here, we identify a novel third follicle cell transition that occurs in the final stages of oogenesis (stage 13/14). This late follicle cell transition is characterized by upregulation of the transcription factor Hindsight (Hnt), and downregulation of the homeodomain transcription factor Cut and the zinc-finger transcription factor Tramtrack-69 (Ttk69). We demonstrate that inducing expression of Cut in stage 14 follicle cells is sufficient to inhibit follicle rupture and ovulation through its negative regulation of Hnt and promotion of Ttk69 expression. Our work illustrates the importance of the stage13/14 transition for follicle maturation and demonstrates the complex regulation required for somatic follicle cells to differentiate into a state primed for follicle rupture and ovulation.

Modeling Membrane Gas and Vapor Separation in the Aspen Plus Environment

The paper presents the results of the development of a unit for calculating mass transport in a membrane gas separation apparatus in the Aspen Plus environment. The created user model has been verified by comparing the results of the calculation of separation characteristics with available experimental data for two cases. In the first case, the calculation results were compared with experimental data on the separation of the ternary H2O/EtOH/N2 (13.3/5.5/81.2 mol %) vapor–gas mixture simulating the stream from the stripping column of a laboratory membrane vapor separation unit with a plate-and-frame membrane module for ethanol recovery from fermentation broth. It has been shown that the calculated concentrations of the components in the retentate and permeate streams are close to the experimental values obtained in the separation of the ternary vapor–gas mixture. In the second case, the calculation results were compared with experimental data obtained upon the separation of a binary N2/CH4 gas mixture (99/1 mol %) simulating a stream with a low content of an easily penetrating impurity component using a radial membrane module. It has been found that the calculated concentration of CH4 in the retentate is noticeably less than in the experiment, especially at high stage cuts, a difference that is associated with the increasing influence of the longitudinal mixing of components at low speeds of the mixture in the channels of the membrane module, which deteriorates the separation characteristics of the apparatus with respect to the removal of impurities and requires additional consideration of the deviation from the plug-flow mode in computational mathematical models used for this case.

Theoretical Performance Evaluation of Inorganic (Non Pd-Based) Membranes for Hydrogen Separation

The aim of this work theoretical study is to theoretically investigate a inorganic membrane assisted purifcation process of an H2-rich stream derived from a conventional methanol steam reforming stage. In particular, a black-box model for multicomponent gas mixture purifcation is developed to evaluate the H2 separation performance of such non-palladium based membranes such as silica, polymeric and carbon membranes, by varying design and processing variables such as stage cut and feed pressure. The most signifcant modeling result is achieved by using a silica membrane based separation module in which 98% of H2 purity and 0.3% of carbon monoxide in the permeate side are reached, operating with a transmembrane pressure of 4.0 bar.

High-Pressure Aging of Asymmetric Torlon® Hollow Fibers for Helium Separation from Natural Gas

Membrane separation for helium extraction from natural gas gained increased interest recently. Several vendors offer membrane elements for helium extraction, although data on their performance and operating experience are unpublished. The aim of this work was to obtain and study the separation performance of asymmetric hollow-fiber membrane element from commercial polyamide-imide Torlon®, in conditions close to the industrial process of helium extraction from natural gas. A membrane element with an active area of 0.177 m2, a helium permeance of 100 l(STP)/(m2·h·bar), and a selectivity α(He/CH4) = 340 was produced. This corresponds to a selective layer thickness of 82.3 nm, which was confirmed by SEM and resistance model calculations. The obtained membrane element was employed to decrease the concentration of helium in its binary mixture with methane from 0.4% to 0.05%. A relationship of separation characteristics from transmembrane pressure is also presented. At 70 bar and a stage cut of 2.7%, the feed flow rate was 0.16 m3(STP)/h, which yielded a helium permeate concentration of 14.7%. At 80 bar, a decrease in permeance to 60 l(STP)/(m2·h·bar) and in selectivity to 240 was observed. It was shown that the main reason for aging was the increased support resistance, due to a partial compaction of pores with a radius of less than 15 nm.

Intensification of CO2 separation performance via cryogenic and membrane hybrid process — Comparison of polyimide and polysulfone hollow fiber membrane

Cryogenic-membrane hybrid CO2 capture process has been considered as a promising alternative for the standalone processes to mitigate the critical challenge of energy penalty. In this work, two different commercial hollow fiber membranes were tested at low temperature condition to find the possibility of consisting a novel cold-membrane-cryogenic hybrid process. The gas permeation properties of membranes were evaluated at different operating temperature, CO2 concentration and stage cut. The experimental results indicated that cryogenic condition could facilitate to improve the CO2/N2 selectivity with a minimum permeance reduction. Specifically, with the operating temperature dropped to −20 °C and feed pressure set at 0.7 MPa, the CO2 selectivity of polyimide membrane increased by 166% with the permeance declined by 31%. Meanwhile, the CO2 recovery and purity of polyimide membrane achieved 92% and 49% at the temperature of −20 °C and pressure 0.7 MPa, respectively. It can be observed that operating membrane at cold condition could be a promising approach to intensify the CO2 separation, and thus decrease the energy consumption of subsequent CO2 liquefaction or desublimation in the hybrid process.