This paper study the role of hydraulic fracture properties on the transient bottomhole pressure (BHP) behavior of a horizontal well producing from a tight fracture-cavity reservoir. A combination of ...point source function, Laplace transformation and Perturbation transformation are used to obtain BHP step by step. Through literature comparison and numerical simulation, the results of BHP have a good consistency, which indicates the proposed method is scientific and reasonable. We divide the fluid flow into five stages, namely the wellbore storage stage, the karst cave fluid flows to the fracture stage, the radial flow stage of karst cave and fracture system, the matrix fluid flows to the fracture stage and the quasi-steady state stage. We come to the conclusion that the number of fractures and fracture direction mainly affect radial flow stage. In contrast, the length of horizontal subsection and skin factor mainly affect the karst cave fluid flows to the fracture stage. The matrix fluid flows to the fracture stage is more obvious when the fracture half-length and the horizontal segment spacing of the horizontal well are small. The study believes special attention should be paid to reforming the formations at both ends of the horizontal well. The advantage of this method is to incorporate well geometry (skin factor) and hydraulic fracturing design (fracture parameters), which is useful for well test interpretation through generating a new set of type curves. What's more, this new method has the characteristics of easy calculation. The findings of this study can help for better understanding of well test analysis in fracture-cavity reservoir. However, the limitation of this study is that it is only suitable for this situation the horizontal well does not encounter karst caves and the karst caves in the reservoir are connected to the wellbore through fractures.
This paper presents a new method to obtain a semi-analytical solution for bottom hole pressure (BHP) of a horizontal well in fracture-cavity reservoirs. The basic building block of the method is to ...build a new source function suitable for the seepage of carbonate rock for the first time and obtain BHP step by step. This paper uses Laplace transform and Perturbation method to solve the diffusivity equation, which is different from the traditional method of using Green’s function presented by Gringarten and Ramey. We validated it with the available published analytical solution and numerical simulation. The sensitivity analysis of pressure and pressure derivative is carried out, and the influence of fracture number, fracture angle, fracture half-length, skin factor, horizontal well segment length, and horizontal well segment spacing on pressure and pressure derivative is analyzed in detail. The findings of the research have led to the conclusion that the number of fractures and fracture direction mainly affect the radial flow stage. In contrast, the length of horizontal subsection and skin factor mainly affect the karst cave fluid flows to the fracture stage. The matrix fluid flows to the fracture stage that is more obvious when the fracture half-length and the horizontal sublevel interval of the horizontal well are small. The advantage of this method is to incorporate well geometry (skin factor) and hydraulic fracturing design (fracture parameters), which are helpful to improve the accuracy of well test interpretation. In addition, this new method has the characteristics of easy calculation. The findings of this study can help for better understanding of transient pressure behavior of horizontal well in fracture-cavity reservoirs.
Using molecular dynamics (MD) simulations, a new approach based on the behavior of pressurized water out of a nanopore (1.3-2.7 nm) in a flat plate is developed to calculate the relationship between ...the water surface curvature and the pressure difference across water surface. It is found that the water surface curvature is inversely proportional to the pressure difference across surface at nanoscale, and this relationship will be effective for different pore size, temperature, and even for electrolyte solutions. Based on the present results, we cannot only effectively determine the surface tension of water and the effects of temperature or electrolyte ions on the surface tension, but also show that the Young-Laplace (Y-L) equation is valid at nanoscale. In addition, the contact angle of water with the hydrophilic material can be further calculated by the relationship between the critical instable pressure of water surface (burst pressure) and nanopore size. Combining with the infiltration behavior of water into hydrophobic microchannels, the contact angle of water at nanoscale can be more accurately determined by measuring the critical pressure causing the instability of water surface, based on which the uncertainty of measuring the contact angle of water at nanoscale is highly reduced.
This paper presents the fracture closure law of fault-controlled reservoir under different pressures by means of a combination of laboratory tests and numerical calculation. Fractures are an ...important seepage channel for fault-controlled reservoirs. With the improvement of the recovery degree of fault-controlled oil and gas reservoirs, the formation pressure decreases, and the effective rock stress increases, which leads to the deformation and even closure of fractures. The dynamic opening and closure of fractures restricts the formation permeability and affects the production of oil and gas wells. In this paper, experimental methods are used to study the fracture closure law. First collect carbonate rock samples, prepare samples through Brazilian splitting experiment and linear cutting method. We establish fracture deformation analysis method based on CT scan gray image. Through pressurization and depressurization test, the closure law of fractures under different filling conditions and fracture extension length was studied. The research results show that as the confining pressure increases, the fracture width and permeability gradually decrease. The stronger the ductility of the filler is, the more obvious the fracture closure is under pressure, and the greater the permeability reduction is. For the same quartz filled fractures, fracture closure laws are different under different filling methods. For fracture support effect, the single layer fine sand > thick layer fine sand > medium-fine mixture sand. In general, the greater the fracture extension length, the higher the permeability, but the increase of permeability is different. The findings of this study can help for a better understanding of reasons for large differences in single well productivity and contribute to rational productivity optimization of fault-controlled reservoirs.
Previous studies have confirmed the diverse spatiotemporal characteristics of Atlantic Niño events. Our research further reveals the crucial preparatory role of equatorial western Atlantic barrier ...layers (BL) and the triggering effect of westerly wind bursts (WWB) on different varieties of Atlantic Niño. Strong easterly winds typically facilitate the formation of thick BL by deepening isothermal layer depth in the western Atlantic through horizontal transport. The existence of BL accumulates the necessary heat for the onset of Atlantic Niño. Additionally, the timing of BL occurrences, the presence of easterly wind anomalies preceding WWB, and the duration of westerly wind anomalies jointly contribute to Atlantic Niño diversity. Persistent westerly wind anomalies following strong easterly winds often lead to Atlantic Niño events lasting over 6 months, while short‐lived events occur when westerly wind anomalies cease shortly after their onset.
Plain Language Summary
The tropical Atlantic Ocean experiences significant year‐to‐year climate variability known as Atlantic Niño or Niña, similar to the warm and cold phases of El Niño–Southern Oscillation (ENSO) in the Pacific. Atlantic Niño has a considerable impact on local rainfall and cyclone activity. However, each instance of Atlantic Niño has unique spatiotemporal development characteristics, which can be classified into four varieties. While previous research has demonstrated that distinct preconditions give rise to different varieties of Atlantic Niño events, there hasn't been any investigation into the common factors among them. The salinity stratified isothermal layer between the base of the mixed layer and the top of the thermocline is referred to as the barrier layer (BL), which is a common feature of tropical western Pacific and Atlantic. The BL in the tropical western Pacific has been confirmed to facilitate the accumulation of heat in the upper ocean and can provide favorable thermal conditions for the onset of El Niño events. Our study reveals the key role of BL induced heat accumulation in various Atlantic Niño onsets. This suggests that anomalies of BL can be reliable indicators for predicting the onset of Atlantic Niño events.
Key Points
The role of barrier layers in heat buildup is confirmed during the development of the four varieties of Atlantic Niño
The heat buildup caused by barrier layers, combined with zonal wind events, regulates the diversity of Atlantic Niño
The sustainability of westerly wind anomalies links to the strength of Atlantic Niño events
As sea ice disappears, the emergence of open ocean deep convection in the Arctic, which would enhance ice loss, has been suggested. Here, using 36 state‐of‐the‐art climate models and up to 50 ...ensemble members per model, we show that Arctic deep convection is rare under the strongest warming scenario. Only five models have convection by 2100, while 11 have had convection by the middle of the run. For all, the deepest mixed layers are in the eastern Eurasian basin. When that region undergoes a salinification and increasing wind speeds, the models convect; yet most models are freshening. The models that do not convect have the strongest halocline and most stable sea ice, but those that lose their ice earliest ‐because of their strongly warming Atlantic Water‐ do not have a persistent deep convection: it shuts down mid‐century. Halocline and Atlantic Water changes urgently need to be better constrained in models.
Plain Language Summary
Both observations and modeling simulations suggest that deep vertical mixing (or deep convection) in winter may become the new normal in the Arctic as sea ice disappears, which further accelerates that disappearance. These simulations are often done using only one model, so here we used all models available that participated in the Climate Model Intercomparison Project Phase 6 (CMIP6), for the strongest warming scenario. We show that after removing those that are already inaccurate in the present, and even with a restrictive threshold, most models have no deep convection in the Arctic, or extremely rarely. Only five still had deep convection by the time the run finishes in 2100. We found that deep convection regions and periods are associated with a saltier, windier surface, while the rest of the Arctic and/or run freshens. The subsurface properties were crucial too: a deep halocline, that is, strongly stratified model, leads to less ice loss and no deep convection. In contrast, models with a shallow halocline and strongly warming Atlantic Water lose their ice and convect earliest, although it does not persist. As water mass properties are poorly represented in CMIP6 models, these need improving to better constrain Arctic deep convection and sea ice projections.
Key Points
Oceanic deep convection does not emerge and persist in the Arctic in the majority of Climate Model Intercomparison Project Phase 6 models, despite a drop in the Nordic Seas
Arctic deep convection occurs only when both surface salinity and winds are increasing, year round, yet most models are freshening
A deep halocline and stable ice cover hinder deep convection, while early ice loss due to warmer Atlantific water can also stop it rapidly
Conventional optical security devices provide authentication by manipulating a specific property of light to produce a distinctive optical signature. For instance, microscopic colour prints modulate ...the amplitude, whereas holograms typically modulate the phase of light. However, their relatively simple structure and behaviour is easily imitated. We designed a pixel that overlays a structural colour element onto a phase plate to control both the phase and amplitude of light, and arrayed these pixels into monolithic prints that exhibit complex behaviour. Our fabricated prints appear as colour images under white light, while projecting up to three different holograms under red, green, or blue laser illumination. These holographic colour prints are readily verified but challenging to emulate, and can provide enhanced security in anti-counterfeiting applications. As the prints encode information only in the surface relief of a single polymeric material, nanoscale 3D printing of customised masters may enable their mass-manufacture by nanoimprint lithography.
Conventional high-rise building surface inspection is usually inefficient and requires the inspectors to work at heights with high risk. Unmanned aerial vehicles (UAVs) carrying optical or thermal ...cameras are currently widely utilized as an effective tool for inspection. The UAV-based data collection, especially for unreachable inspection areas, is the basis of unmanned inspection of building surface. In addition, building information modeling (BIM) with rich geometric and semantic information can also be instrumental in building surface inspection. Therefore, this paper presented an automatic inspection method of building surface, especially for the inspection data collection, by integrating UAV and BIM. To minimize the length of UAV flight while collecting complete and high-quality image data considering the limited endurance capability, the coverage path planning problem is solved using genetic algorithm (GA). The required inspection areas are obtained from the BIM model of the target building to be inspected. To further enhance the automation of building surface inspection, the optimized UAV flight mission parameters are rapidly calculated based on the BIM model and proposed algorithm. A real office building in Shenzhen University campus is used to validate the presented automatic method. The quality of the collected inspection images using the UAV with optimized flight mission are evaluated. The results show that this method leads to time-efficient, accurate, and high-quality inspection data collection for building surface.
•UAV flight path of inspecting high-raised building is optimized based on BIM.•Target inspection areas are efficiently generated from BIM.•Inspection flight path of UAV is optimized based on GA.•BIM-based flight mission parameters can be automatically transformed for execution.
Conversion of CO2 to value-added chemicals has been a long-standing objective, and direct hydrogenation of CO2 to lower olefins is highly desirable but still challenging. Herein, we report a ...selective conversion of CO2 to lower olefins through CO2 hydrogenation over a ZnZrO/SAPO tandem catalyst fabricated with a ZnO-ZrO2 solid solution and a Zn-modified SAPO-34 zeolite, which can achieve a selectivity for lower olefins as high as 80–90% among hydrocarbon products. This is realized on the basis of the dual functions of the tandem catalyst: hydrogenation of CO2 on the ZnO-ZrO2 solid solution and lower olefins production on the SAPO zeolite. The thermodynamic and kinetic coupling between the tandem reactions enable the highly efficient conversion of CO2 to lower olefins. Furthermore, this catalyst is stable toward the thermal and sulfur treatments, showing the potential industrial application.
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•A silsesquioxane-based disulfide-linked polymer was rapidly synthesized in 2 min.•The polymer shows a highly selective and efficient adsorption towards cationic dyes over anionic ...dyes.•The absorbent is recyclable.
Developing a facile and rapid method to prepare adsorbents for an efficient and selective removal of dyes is of great importance for human health and environment. In this work, a silsesquioxane-based disulfide-linked polymer (DLP) was rapidly synthesized by a simple oxidative coupling reaction of octa(3-mercaptopropyl)silsesquioxane within 2 min at room temperature. The synthesized DLP demonstrated selective and efficient adsorption of cationic dyes over anionic dyes with the maximum capacities of 12.94 mg g−1 for methylene blue, 18.47 mg g−1 for rhodamine B and 26.69 mg g−1 for crystal violet. The high uptake and selectivity for cationic dyes was attributed to the electrostatic interactions between the anionic charges from sulfur and oxygen anions formed by the deprotonation of thiols and hydroxyls in the DLP and the cationic charges from the dyes, and the swelling behavior of the DLP. To investigate the adsorption process, the effect of various factors such as contact time, initial concentration, temperature, and pH on the adsorption activity of cationic dyes was studied. The adsorption equilibrium data showed a better fitting to the Langmuir isotherm model than the Freundlich model and the adsorption kinetics fitted well with the pseudo-second-order kinetic model, indicating that the adsorption process is mostly governed by the chemisorption behavior. Additionally, the absorbent was recyclable with the adsorption capacity being >95% after five times recycle adsorption. These results indicated that the present disulfide-linked polymer could be promisingly applied as an efficient adsorbent for the selective removal of cationic dyes from industrial wastewater.
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