Swept Volume Research Articles

An active endoscope with small sweep volume that preserves image orientation for arthroscopic surgery

Microsurgery is generally performed in narrow spaces with limited movement. Endoscopes that allow for angle changes have been developed using elastic materials, but they require a large bending space. We propose a new endoscope with a small sweep volume for angle changes. We fabricated a prototype with a thumb-operated joystick. The image sensor is attached to the tooltip. The image signal is input to a motor control board which computes inverse kinematics and transforms it into joint angle values. Each axis is positioned according to these values. The tooltip sweeping volume was 104 mm3 . Surgeons at the Asan Medical Center used our endoscope to obtain images of the biceps tendon and subscapularis joints of a cadaver. Currently, a low-resolution image sensor is attached to endoscope tooltips. In the future, we will develop a high-resolution image module equipped with an ultra-small complementary metal oxide semiconductor sensor.

Pumping Loss of Shrouded Meshed Spur Gears

Abstract High speed rotorcraft transmissions are subject to load-independent power losses consisting of drag loss and pumping loss. Tightly conforming shrouds enclosing the transmission gears are often incorporated to reduce the drag component of the total load-independent losses. However, tightly conforming axial shrouds can result in an increase in the pumping loss component. Quantifying the pumping loss of shrouded gear transmissions has been the subject of many studies. This study presents a new approach for estimating pumping loss based on the concept of swept volume and examines the applicability of the approach to various shroud configurations. The drag loss and pumping loss of a shrouded spur gear pair have been determined through testing using the NASA Glenn Research Center (GRC) Gear Windage Test Facility. The results from this testing have been compared to theoretical results using the formulations presented in this study. In addition, computational fluid dynamics (CFD) analysis has been conducted for the various shroud configurations tested at NASA GRC. The results from the CFD analysis confirm the theoretical and empirical results and provide insight into the applicability of the swept volume approach for estimating pumping power loss of shrouded gear transmissions.

Application of Polymeric microspheres in extra low permeability reservoir in Huabei Oilfield

Aiming at the problems of low water displacement recovery effect in extra low permeability reservoir of Fault-block B10 in Huabei oilfield, the oil recovery technique of surfactant flooding under polymeric microspheres was proposed in this paper. According to the features of polymeric microspheres deep profile control technique, expansion, plugging capacity and migration ability of two samples were evaluated. On the basis of these, a polymeric microspheres matched with the B10 reservoir was selected and tested in the field. Field application indicated that average pressure elevation of each well was up to 4 MPa, corresponding wells efficiency were 88%, comprehensive water was decreased by 6.6% and cumulative incremental oil production was 3350t.Fault block B10 in Huabei Oilfield had an average porosity of 17.6% and an average permeability of 3.5×10−3μm2. It belonged to a low porosity ultra-low permeability reservoir. The surface crude oil viscosity was 90mPa.s, which belonged to ordinary heavy oil reservoir. Many years of water injection had formed a fixed water flow channel in the formation. The water injection wave and volume were not balanced, and the problem of inefficient or ineffective water injection circulation was becoming more and more prominent. At present, the comprehensive water cut had reached 90%. After surfactant flooding in some well groups, due to the serious heterogeneity of reservoir, displacement fingering was obvious and the implementation effect was poor. As a new type of deep profile control and flooding agent, polymer microspheres can form step-by-step plugging after entering the low-permeability reservoir, and greatly adjust the water flooding flow field and expand the sweep volume [1]. In order to explore the adaptability of polymer microsphere to B10 reservoir, a polymer microsphere suitable for B10 reservoir was selected by static expansion of microsphere and dynamic physical model plugging experiment of core. Field application showed that the polymer microsphere had good adaptability in B10 fault block.

Analysis of Different Uniflow Scavenging Options for a Medium-Duty 2-Stroke Engine for a U.S. Light-Truck Application

Abstract The work presented here seeks to compare different means of providing uniflow scavenging for a 2-stroke engine suitable to power a U.S. light-duty truck. Through the “end-to-end” nature of the uniflow scavenging process, it can in theory provide improved gas-exchange characteristics for such an engine operating cycle; furthermore, because the exhaust leaves at one end and the fresh charge enters at the other, the full circumference of the cylinder can be used for the ports for each flow, and therefore, for a given gas exchange angle-area demand, expansion can theoretically be maximized over more traditional loop-scavenging approaches. This gives a further thermodynamic advantage. The three different configurations studied, which could all utilize uniflow scavenging, were the opposed piston, the poppet-valve with piston-controlled intake ports, and the sleeve valve. These are described and all are compared in terms of indicated fuel consumption for the same cylinder swept volume, compression ratio, and exhaust pressure, for the same target indicated mean effective pressure (IMEP) and indicated specific power. A new methodology for optimization was developed using a one-dimensional engine simulation package which also took into account charging system work. The charging system was assumed to be a combination of supercharger and turbocharger to permit some waste energy recovery. As a result of this work, it was found that the opposed-piston configuration provides the best attributes since it allows maximum expansion and minimum heat transfer. Its advantage over the other two (whose results were very close) was of the order of 8.3% in terms of net specific fuel consumption (NSFC) (defined as indicted specific fuel consumption (ISFC) net of supercharger power). Part of its advantage also stems from its requirement for minimum air supply system work, included in this NSFC value. Interestingly, it was found that existing experiential guidelines for port angle-area specification for loop-scavenged, piston-ported engines using crankcase compression could also be applied to all of the other scavenging types. This has not been demonstrated before. The optimization process that was subsequently developed allowed port design to be tailored to specific targets, in this case lowest NSFC. The paper therefore presents a fundamental comparison of scavenging systems using a new approach, providing new insights and information which have not been shown before.

Efficient Preparation of Nano-Starch Particles and Its Mechanism of Enhanced Oil Recovery in Low-Permeability Oil Reservoirs

Summary As development of low-permeability oil reservoirs continues to increase, it urgently needs an efficient enhanced oil recovery (EOR) technology to adapt to the new situation and requirement of oilfield exploitation. Although the application of nanomaterials for the EOR of low-permeability oil reservoirs has initially obtained good results, the types of currently used nanomaterials in the field of EOR are limited, and the mechanism of EOR is still unclear. In this paper, a type of nanosized starch particle is efficiently prepared using the method of precipitation with the help of ultrasonic oscillation. Under ultrasonic oscillation, the viscosity of starch paste can be significantly decreased, which is beneficial for the precipitation of starch nanoparticles. After ultrasonic oscillation, the size of the developed nanoparticles is smaller and controlled during the precipitation of starch paste using ethanol as the precipitating agent. The developed nanosized starch particles are suitable for the low-permeability oil reservoirs with low-salinity water. Subsequently, the mechanism of EOR of the developed nanosized starch particles is systematically studied through laboratory experiments. In addition to changing the wettability of rock surface and decreasing oil/water interfacial tension (IFT), the nanosized starch particles can effectively change the motion state of water molecules and cause the change of the structure of water molecules. In the low-permeability core, the displacement front of the nanosized starch solution is uniform, and the sweep volume of the nanosized starch solution flooding is large. Because of a higher sweep volume and a smaller adsorption loss, nanosized starch solution flooding can achieve a better effect of oil recovery than surfactant flooding in 30 m of low-permeability porous medium. The conclusions can provide a new guidance for EOR technology to support the efficient development of low-permeability oil reservoirs.

Feasibility of three dimensional power Doppler ultrasonography methods to assess placental perfusion

ObjectivesGiven the crucial role of the placenta in establishing a healthy pregnancy, reliable non-invasive methods to measure placental perfusion are desirable. The aim of this study is to determine the reproducibility and potential bias in different three-dimensional power Doppler (3DPD) methods assessing placenta perfusion. MethodsTen singleton pregnancies around 16 weeks of gestation, with an anteriorly located placenta and centrally inserted umbilical cord were included in this study. Eight different combinations of a specific placental sweep and sonobiopsy method were used to evaluate placental perfusion. Vascularization index (VI), flow index (FI) and vascularization-flow index (VFI) were determined offline using the 4D-view program. Reproducibility and repeatability of the methods, expressed as correlation coefficients and Bland-Altman mean differences, were calculated. Differences between sampling methods were analyzed using t-test or Mann-Whitney U test. ResultsIntra- and inter-class correlation coefficient (CC) was highest when using a spherical centrally placed sonobiopsy of 2 cm3 in a whole placenta sweep (method 1; IntraCC VI 0.985, FI 0.769, VFI 0.993, InterCC VI 0.986, FI 0.784, VFI 0.987). Overall, intraCCs were higher compared to interCCs. Lowest mean differences in VI and FI were found comparing spherical to manual sonobiopsies, whereas the mean differences in VFI were lowest when comparing central versus peripheral located sonobiopsies. Comparing the three vascular indices, best median intra- and interCC and lowest mean differences were found for VFI. ConclusionsThree dimensional placental vascularization analysis showed best reproducibility using whole placental sweep volume and centrally located, spherical sonobiopsy of 2 cm3.

Fabrication and testing of a gamma type stirling engine

The paper presents the manufacturing and design aspects of a gamma type Stirling engine using spirit lamp flame as its heat source. A small scale model of the engine is developed with 10 cc swept volume. The engine was tested two times. Vital observations and data collection was done during the first test. After incorporating sufficient modification on the engine with the observations of the first test, second test was conducted successfully. The speed of the engine during the working was monitored. The engine attained maximum speed up to 2000 rpm. When the engine could not produce the required temperature difference, speed was dropped down to 500 rpm. This study also includes the various manufacturing processes carried out during the engine development. This data and engine can be used for future reference model, since Stirling engine has the potential to become Green engine.

Synchronous injection-production energy replenishment for a horizontal well in an ultra-low permeability sandstone reservoir: A case study of Changqing oilfield in Ordos Basin, NW China

It is difficult to build an effective water flooding displacement pressure system in the middle section of a horizontal well in an ultra-low permeability sandstone reservoir. To solve this problem, this study proposes to use packers, sealing cannula and other tools in the same horizontal well to inject water in some fractures and produce oil from other fractures. This new energy supplement method forms a segmental synchronous injection-production system in a horizontal well. The method can reduce the distance between the injection end and the production end, and quickly establish an effective displacement system. Changing the displacement between wells to displacement between horizontal well sections, and point water flooding to linear uniform water flooding, the method can enhance water sweeping volume and shorten waterflooding response period. The research shows that: (1) In the synchronous injection and production of horizontal well in an ultra-low-permeability sandstone reservoir, the water injection section should select the section where the natural fractures and artificial fractures are in the same direction or the section with no natural fractures, and the space between two sections should be 60–80 m. (2) In addition to controlling injection pressure, periodic water injection can be taken to reduce the risk of re-opening and growth of natural fractures or formation fracture caused by the gradual increase of water injection pressure with water injection going on. (3) Field tests have verified that this method can effectively improve the output of single well and achieve good economic benefits, so it can be widely used in the development of ultra-low permeability sandstone reservoirs.

Experimental Study on Mechanism of Foamy Oil-Assisted Methane Foam Flooding in an Etched Glass Micromodel

A number of heavy oil reservoirs under cold heavy oil production with sand (CHOPS) show anomalously good primary performance due to foamy oil flow. However, as the pressure of the reservoir depletes, the foamy oil phenomenon gradually disappears and the development gradually deteriorates. In this paper, a new method named methane foam flooding is proposed as an effective enhanced heavy oil recovery process. In this paper, we take advantage of Ross miles foam equipments to select foaming agents and evaluate the foam ability, study and analyze the foam ability of different foam agent in different concentrations. and through visual microscopic model experiments to study the oil displacement mechanism and flow characteristics of methane foam flooding. The results show that foaming agent ZY-1 has excellent foam comprehensive properties, and it has the best foam stability at 1% concentration. It can be found from the micromodel flood experiments that methane foam flooding can effectively block the formation of high permeability channels, delaying the production of methane gas, emulsifying crude oil and changing the wettability of the rock to enlarge a sweeping volume and improve oil displacement efficiency.

Experiment investigation of microemulsion enhanced oil recovery in low permeability reservoir

Microemulsion flooding is a effective enhanced oil recovery for low permeability. In this paper, combined the advantage of sulphobetaine surfactant and gemini surfactant, a kind of gemini sulphobetaine surfactant (DPSB) was used to prepared microemulsion. The oil–water interfacial tension and adsorption for different concentration surfactant was measured to evaluate the DPSB property. The stability of microemulsion, the microemulsion volume percentage, solubilisation parameter and relative phase volume, microemulsion viscosity was also measured. The performance of this surfactant was further optimized by adding the additives. The relative permeability was determined to analyze the fluid flow characteristics, and the recovery efficiency was studied through natural core and visual core displacement experiment. The results show that the oil–water interfacial tension is 9.1 × 10−4 mN/m when DPSB concentration is 0.5%, and it can still maintain low interfacial tension after adsorption. The interfacial tension can be further decreased by adding n-butyl alcoholy. When the DPSB concentration is 1.5% and n-butyl alcohol concentration is 1.5%, the microemulsion volume percentage is 31%, and the viscosity is 4.37 mPa∙s. It can reduce the flow velocity of displacing fluid, and expand sweep volume. Compared with water flooding, the residual oil saturation reduces by about 30% in microemulsion flooding. The recovery efficiency is increased by about 4% compared with the low concentration of surfactant flooding.

Transient performance of the mixed flow and radial flow variable geometry turbines for an automotive turbocharger

In our previous paper, the steady-state test results of a mixed flow turbine with variable nozzle vanes for a turbocharger are reported. In this paper, the transient response of the same mixed flow turbine along with that of a similarly sized radial flow turbine is presented. The turbine size is suitable for handling the flow capacity of the diesel engines with swept volume up to 1.5 L. The previous experimental test set up is modified by adding a quick-release valve – actuation system before the turbine inlet to obtain a transient response. The radial and mixed flow turbines are tested for different turbine inlet pressures and for various opening positions of the nozzle vanes while matching the turbine mass flow parameters between radial and mixed flow turbines. Typically at nozzle vane openings corresponding to 50% mass flow parameter and 1.5 bar (abs) pressure at the inlet to the turbine, the transient response time for the turbine with mixed flow variable nozzle vanes configuration is about 0.770 s, as compared to 0.858 s for the turbine with radial flow variable nozzle vanes configuration.

Numerical modelling of coupled single-phase fluid flow and geomechanics in a fractured porous media

Dynamic variation of porosity, permeability, and elastic modulus was considered in order to investigate the single-phase fluid flow in a fractured porous media using fully coupled hydro and geomechanical models. The development of streamlines, pressure distribution, effective stress and strain generations have been extensively studied. However, from the present model results, it can be critically noted that the development of streamlines and pressure are highly dependent on (a) fracture orientation; (b) the distance from injection/production well; and (c) the fracture density. The results have been analyzed both in the presence and absence of geomechanics. It was observed from the model results that there was no fluid flow within the fracture when the fracture aperture varied between 10−6 and 10−9 m; and the respective streamlines were very smooth at the fracture-matrix interface, whereas, a significant fluid flow was observed within the fracture when the aperture sizes exceeded 10−6 m; and in this case, streamlines and pressure variations were very sensitive at the fracture-matrix interface. The model results clearly projected that this sensitivity primarily resulted from the lateral stresses arising from the generation of effective-stress and its associated strains. It was further observed from the numerical results that the effective stress, strain, and pressure in the fractured porous media were extremely sensitive to the Biot-Willis coefficient; and thereby clearly projecting the significance of the considered lateral stresses (which are generally absent, while characterizing a typical conventional reservoir). In addition, it was also observed that the lowest effective stress occurred in the vicinity of the injection well, while the highest value was found nearer to the production well for Biot-Willis coefficients with values less than 0.6. Thus, it can be critically concluded that the compressive strains were dominating over the highest sweep volume of the fractured porous media that starts a little bit away from the injection well, and that gradually increases to the maximum at the production well, when the Biot-Willis coefficient falls below 0.6. Finally, the model has been upscaled by increasing the scale of the porous medium with complex embedded fracture along with the dynamic variation of permeability, porosity, and elastic modulus so that the developed numerical model will better replicate the complex reality associated with the field scale.

Effect of Pore-Throat Microstructures on Formation Damage during Miscible CO2Flooding of Tight Sandstone Reservoirs

Pore and throat blockage and wettability alteration caused by asphaltene deposition are serious problems during the injection of CO2 into subsurface reservoirs for enhanced oil recovery (EOR). During miscible CO2 flooding, the efficacy and distribution of fluid flow in sandstone reservoirs are controlled by the pore-throat microstructure of the rock. Furthermore, CO2 injection promotes asphaltene precipitation on pore surfaces and in the pore throats, decreasing the permeability and altering reservoir wettability. In this work, miscible CO2 flooding experiments under reservoir conditions (up to 70 ± 0.1 °C, 18 MPa) were carried out on four samples with very similar permeabilities but significantly different pore size distributions and pore-throat structures to study the effects of the pore-throat microstructure on formation damage. The features of the pore-throat structure were evaluated by fractal theory, based on constant-rate mercury intrusion (CRMI) tests. Reservoir rocks with smaller pore-throat sizes and more heterogeneous and poorer pore-throat microstructures were found to be more sensitive to asphaltene precipitation, with corresponding 14–22% lower oil recovery factors (RFs) and 4–7% greater decreases in permeability compared to more homogeneous rocks and rocks with larger pore throats. However, the water-wettability index of cores with larger and more connected pore-throat microstructures was found to drop by an extra 15–25% compared to the water-wettability decrease found for heterogeneous cores. We attribute these observations to an increase in asphaltene precipitation caused by the larger sweep volume of injected CO2, which occurs in rocks with larger and more homogeneous pore throats. In addition, we observed that rocks with more homogeneous pore-throat microstructures also exhibit homogeneity in the consequent distribution of formation damage.

Microbial enhanced oil recovery through deep profile control using a conditional bacterial cellulose-producing strain derived from Enterobacter sp. FY-07

BackgroundHeterogeneity of oil-bearing formations is one of major contributors to low oil recovery efficiency globally. Long-term water flooding will aggravate this heterogeneity by resulting in many large channels during the exploitation process. Thus, injected water quickly flows through these large channels rather than oil-bearing areas, which ultimately leads to low oil recovery. This problem can be solved by profile control using polymer plugging. However, non-deep profile control caused by premature plugging is the main challenge. Here, a conditional bacterial cellulose-producing strain, namely Enterobacter sp. FY-0701, was constructed for deep profile control to solve the problem of premature plugging. Its deep profile control and oil displacement capabilities were subsequently identified and assessed.ResultsThe conditional bacterial cellulose-producing strain Enterobacter sp. FY-0701 was constructed by knocking out a copy of fructose-1, 6-bisphosphatase (FBP) encoding gene in Enterobacter sp. FY-07. Scanning electron microscope observation showed this strain produced bacterial cellulose using glucose rather than glycerol as the sole carbon source. Bacterial concentration and cellulose production at different locations in core experiments indicated that the plugging position of FY-0701 was deeper than that of FY-07. Moreover, enhanced oil recovery by FY-0701 was 12.09%, being 3.86% higher than that by FY-07 in the subsequent water flooding process.ConclusionsTo our knowledge, this is the first report of conditional biopolymer-producing strains used in microbial enhance oil recovery (MEOR). Our results demonstrated that the conditional bacterial cellulose-producing strain can in situ produce biopolymer far from injection wells and plugs large channels, which increased the sweep volume of injection water and enhance oil recovery. The construction of this strain provides an alternative strategy for using biopolymers in MEOR.

The mechanism of the effect of Geobacillus stearothermophilu on crude oil

The study of the mechanism of endogenous microbial flooding in the reservoir, this paper analyzed the effect of microbial and its product on the stability of paraffin wax using Geobacillus stearothermophilu isolated from wells. GC-MS was adopted to investigate the degradation of crude oil by emulsified bacteria. A simulated reservoir environment created by micro-visualized two-dimensional glass model was used to identify mechanism of emulsified bacteria on remaining oil. Emulsified bacteria and their metabolite can greatly improve the efficiency of displacement process. Microorganisms can use crude oil and activator as the source of nutrition, facilitating its grow at the oil-water interface, thus creating a favorable wettability by means of degradation of residual oil. Emulsified bacteria and their metabolite can emulsify the crude oil into emulsion, whose large viscosity attribute to a lower oil-water interface force as well as an improved mobility ratio and in the end, an enlarged swept volume.

Review of experimental and simulation studies of enhanced oil recovery using viscoelastic particles

The profile control that employs viscoelastic particles for enhancing oil recovery is a novel technology that has attracted widespread interest in recent years. Viscoelastic particles can selectively plug high-permeability zones and enlarge the sweep volume of low-permeability zones, which can better improve the effect of development. Based on the extensive investigation of existing literature, the research status of experiments and simulations of viscoelastic particles on profile control is introduced in this paper. First, the properties of viscoelastic particles are summarized. Thereafter, the injection ability, migration ability, profile control ability, and damage effects of viscoelastic particles are expounded. Moreover, the simulation methods for studying the profile control, including classical percolation theory, size exclusion theory, and lattice Boltzmann method–discrete element method, are generalized. The characteristics and applications of different simulation methods are discussed. Finally, the problems that hinder the implementation of experiments and simulations are identified, and suggestions for clarifying the focus and directions of future research are presented.

A numerical study of the influence of design variable interactions on the performance of a Stirling engine System

This paper presents a study to determine the influence of design variable interactions on the performance of a Stirling engine, as well as a new methodology to identify and quantify such influence. An Alpha-type 2 kW Stirling engine was assessed using a second order model where the engine, heater, regenerator and cooler variables were simultaneously analyzed in pairs.The study includes 240 interactions corresponding to the 16 selected design variables. It was observed that the piston stroke and cylinder diameter variables have more significant interactions with the rest of the parameters due to their strong influence over mass flow. The piston crown length does not show significant interactions; however, it reduces individual thermal losses in the expansion zone. The cycle achieves its maximum net power at angles less than 90° due to pressure, heat losses, and the ratio between mass flow rates and swept volume. Finally, this work presents recommendations for the analyzed interactions.The global interactions scheme provides a qualitative and quantitative identification of the variables that affect the system, synthesized into a hierarchy of variables that indicates a critical path for their exploration for system design and optimization purposes.

Applications of in situ polymerization microsphere with surfactant EOR in low-permeability and heterogeneous reservoirs

In order to enhance the low recovery efficiency in low-permeability and heterogeneous reservoirs resulted by water channeling during water flooding process, a series of flooding experiments using in situ polymerization microsphere (ISPM) with surfactant were conducted to achieve deep profile control in high conductivity water channels. Dynamic pressure measurement showed that ISPM demonstrated good injectability and profile control effect in low-permeability core of 20.22 mD, as the plugging rate was as high as 78.99%. At the same time, the electron microscopy results showed that the ISPM could migrate deeper into the core to form microsphere clusters to block the high conductivity channels. The core flooding experiments showed that the profile control effect of the composite slug consisted of surfactant and ISPM was much better than that of just ISPM alone. The front part of the slug consisting of BA with strong emulsifying capability and ultra-low interfacial tension can better exert the profile control effect of the ISPM and expand the sweep volume of the subsequent displacing agent better than surfactant TS with ultra-low interfacial tension. As a subsequent oil displacing agent after ISPM + BA profile control, surfactant BA with strong emulsifying capability and ultra-low interfacial tension, compared with AES and TS, achieved higher recovery efficiency. In low-permeability and heterogeneous reservoirs, ultra-low interfacial tension is screening crucial characteristic of surfactant, but emulsification capacity also plays a very important role. Combination of surfactant BA and ISPM could fully utilize the profile control effect of ISPM and the oil stripping effect of surfactant; the stage recovery efficiency was as high as 22.52%.

Oil production and reservoir damage during miscible CO2 injection

The blockage and alteration of wettability in reservoirs caused by asphaltene deposits are problems that contribute to poor oil recovery performance during carbon dioxide (CO2) injection. Oil production and reservoir damage are both controlled by macroscopic interlayer heterogeneity and microscopic pore-throat structure and may be optimized by the choice of flooding method. In this work, the residual oil distribution and the permeability decline caused by organic and inorganic precipitation after miscible CO2 flooding and water-alternating-CO2 (CO2-WAG) flooding have been studied by carrying out core-flooding experiments on a model heterogeneous three-layer reservoir. For CO2, flooding experimental results indicate that the low-permeability layers retain a large oil production potential even in the late stages of production, while the permeability decline due to formation damage is larger in the high-permeability layer. We found that CO2-WAG can reduce the influence of heterogeneity on the oil production, but it results in more serious reservoir damage, with permeability decline caused by CO2–brine–rock interactions becoming significant. In addition, miscible CO2 flooding has been carried out for rocks with similar permeabilities but different wettabilities and different pore-throat microstructures in order to study the effects of wettability and pore-throat microstructure on formation damage. Reservoir rocks with smaller pore-throat sizes and more heterogeneous pore-throat microstructures were found to be more sensitive to asphaltene precipitation, with corresponding lower oil recovery and greater decreases in permeability. However, it was found that the degree of water wetness for cores with larger, more connected pore-throat microstructures became weaker due to asphaltene precipitation to pore surfaces. Decreasing the degree of water wetness was found to be exacerbated by increases in the sweep volume of injected CO2 that arise from cores with larger and better connected pore throats. Erosion of water wetness is a disadvantage for enhanced oil recovery operations as asphaltene precipitation prevention and control measures become more necessary.

FADE: Feature Aggregation for Depth Estimation With Multi-View Stereo

Both structural and contextual information is essential and widely used in image analysis. However, current multi-view stereo (MVS) approaches usually use a single common pre-trained model as pixel descriptor to extract features, which mix structural and contextual information together and thus increase the difficulty of matching correspondence. In this paper, we propose FADE (feature aggregation for depth estimation), which treats spatial and context information separately and focuses on aggregating features for efficient learning of the MVS problem. Spatial information includes image details such as edges and corners, whereas context information comprises object features such as shapes and traits. To aggregate these multi-level features, we use an attention mechanism to select important features for matching. We then build a plane sweep volume by using a homography backward warping method to generate match candidates. Furthermore, we propose a novel cost volume regularization network aims to minimize the noise in the matching candidates. Finally, we take advantage of 3D stacked hourglass and regression to produces high-quality depth maps. With these well-aggregated features, FADE can efficiently perform dense depth reconstruction, achieving state-of-the-art performance in terms of accuracy and requiring the least amount of model parameters.