Saturation Discrimination Research Articles

Discrimination of Stator Asymmetries and Magnetic Saturation in Self-Excited Induction Generators

Discrimination of Stator Asymmetries and Magnetic Saturation in Self-Excited Induction Generators

Petrophysical evaluation for development of a marginal oil field in the onshore Niger Delta, Nigeria

Petrophysical evaluation was conducted on an onshore marginal field in Niger Delta with the aim of evaluating the rock and fluid properties to boost hydrocarbon production in the field. Five well logs suite from five wells and core log data for two wells were utilized for this study. Petrophysical properties evaluated included; porosity, net to gross, formation factor, irreducible water saturation, permeability, water saturation, hydrocarbon saturation and pay thickness. The well logs suite contained the following logs: Gamma ray log for lithology identification; Resistivity log for fluid type discrimination and determination of water saturation; Density log for porosity determination; and Neutron log in combination with density log for hydrocarbon types. A total of seven reservoir sands (, Sand A, B, C, D, E, F and G) were identified and correlated across all five wells on the basis of gamma ray and resistivity log motifs. The reservoir gross thicknesses ranged from 62.55 to 228.50 ft, shale volume from 7.0 to 24.60%, net to gross from 0.76 to 0.93%, effective porosity from 20.78 to 26.22%, water saturation from 35.80 to 62.30% and permeability ranged from 545.94 to 2821.97 mD. This shows that the reservoirs are of good quality for hydrocarbon productionacross the field.

Combined geophysical and rock physics workflow for quantitative CO2 monitoring

Safe CO2 storage requires conformance verification, i.e. confirmation that the pressure and CO2 accumulation are consistent with modelling forecasts within a given uncertainty range. Quantitative estimates of relevant reservoir parameters (e.g. pore pressure and fluid saturations) are usually derived from geophysical monitoring data (e.g. seismic, electromagnetic and/or gravity data) and potential prior knowledge of the storage reservoir. We describe a two-step strategy combining geophysical and rock physics inversions for quantitative CO2 monitoring. A Bayesian formulation is used to propagate and account for uncertainties in both steps. We demonstrate our workflow using datasets from the Sleipner CO2 storage project (Norwegian North Sea) and combining seismic Full Waveform Inversion and rock physics inversion. We derive rock frame properties from baseline data and use them as input to obtain 2D spatial distribution of CO2 saturation with uncertainty assessment from monitor data. We also discuss the need for advanced rock physics models, considering the way fluid phases are mixed (uniform to patchy mixing) and the trade-off effects of pore pressure and fluid saturation on geophysical measurements. We consequently recommend a joint rock physics inversion approach, where multi-physics, and multi-parameter inversion can be used for better discrimination of pressure, saturation, and fluid mixing effects towards more quantitative conformance verification.

Deep learning a poroelastic rock-physics model for pressure and saturation discrimination

Determining saturation and pore pressure is relevant for hydrocarbon production as well as natural gas and [Formula: see text] storage. In this context, seismic methods provide spatially distributed data used to determine gas and fluid migration. A method is developed that allows the determination of saturation and reservoir pressure from seismic data, more accurately from the rock-physics attributes of velocity, attenuation, and density. Two rock-physics models based on Hertz-Mindlin-Gassmann and Biot-Gassmann are developed. Both generate poroelastic attributes from pore pressure, gas saturation, and other rock-physics parameters. The rock-physics models are inverted with deep neural networks to derive saturation, pore pressure, and porosity from rock-physics attributes. The method is demonstrated with a 65 m deep unconsolidated high-porosity reservoir at the Svelvik ridge, Norway. Tests for the most suitable structure of the neural network are carried out. Saturation and pressure can be meaningfully determined under the condition of a gas-free baseline with known pressure and data from an accurate seismic campaign, preferably cross-well seismic. Including seismic attenuation increases the accuracy. Although training requires hours, predictions can be made in only a few seconds, allowing for rapid interpretation of seismic results.

Horizontal lines in the MacLeod-Boynton diagram: Saturation discrimination and hue discrimination compared

Horizontal lines in the MacLeod-Boynton diagram: Saturation discrimination and hue discrimination compared

Pressure Control and Conformance Management for Safe and Efficient CO2 Storage – An Overview of the Pre-ACT Project

Pre-ACT is a three-year (2017-2020) research project on CO2 storage which brings together a partnership of 10 research institutes and industrial companies. Pre-ACT is delivering cutting-edge research into the safe storage and monitoring of CO2. The focus is on improving strategies for monitoring and management of pore pressure within the storage reservoir. Pre-ACT is establishing methodologies to assess the conformance of a storage site, relative to its expected performance, through research in five work packages. The primary output will be a quantitative conformance system that utilises a cost-effective monitoring strategy to define a series of pressure-driven support protocols. The protocols are directly applicable to industrial operators and focus on the main storage-related challenges for accelerated deployment of CCS: capacity, confidence and cost. Most of the work during the first year in Pre-ACT has addressed pre-injection (pressure) modelling, pressure and saturation monitoring, and conformance assessment. Examples of initial work include: (1) studies at the Horda Platform (North Sea) showing the importance of uncertainty in interpretation of faults and their sealing properties for Smeaheia pre-injection pressure modelling; (2) planning of an experiment for controlled pressure- and saturation discrimination at the Svelvik Field Lab and development of an approach to separate the effects of pressure and saturation changes; and (3) the development of a conformance assessment tool and value-of-information workflow for comparison of different monitoring configurations (expected gain and deployment cost).

Sonic QP/QS ratio as diagnostic tool for shale gas saturation

Sonic [Formula: see text] ratio obtained from full-waveform acoustic logs in conventional sandstone reservoirs is known to be sensitive to the presence of gas, and it is regarded as a potential diagnostic tool for saturation discrimination. However, it is not known if such a saturation diagnostic tool will be applicable in unconventional reservoirs, such as in gas-saturated shales. We have analyzed the monopole and dipole waveform logs acquired from a shale gas exploration well in the Cooper Basin, South Australia. The depth interval of interest is 300 m thick, and it intersects three shale units in which the two underlying formations contain gas saturation of more than 30% and are identified as the primary exploration targets. We use the statistical average method to extract the [Formula: see text]- and the [Formula: see text]-wave attenuation profiles and obtain an average [Formula: see text]-wave quality factor of [Formula: see text] and [Formula: see text]-wave quality factor of [Formula: see text]. The gas saturation of the lithological layers having [Formula: see text] is appreciably larger than the gas saturation of the others having [Formula: see text]. The net difference indicates that the saturation is a dominant factor in controlling the [Formula: see text] ratio in these shale formations. Based on the criterion [Formula: see text], we identify the intervals with high gas potential. This result is in good agreement with the prediction from an independently obtained saturation log based on petrophysical analysis. Furthermore, we found that the [Formula: see text] ratio can be jointly interpreted with the [Formula: see text] ratio to differentiate between the saturation and the lithology effects for a shale reservoir interbedded with sandstone layers. Our results underpin the concept of using the [Formula: see text] ratio as a hydrocarbon saturation indicator and provide insights into application of this technique for shale gas detection.

Utilizing spectral decomposition to determine the distribution of injected CO2 at the Snøhvit Field

ABSTRACTTime‐lapse 3D seismic reflection data, covering the CO2 storage operation at the Snøhvit gas field in the Barents Sea, show clear amplitude and time‐delay differences following injection. The nature and extent of these changes suggest that increased pore fluid pressure contributes to the observed seismic response, in addition to a saturation effect.Spectral decomposition using the smoothed pseudo‐Wigner–Ville distribution has been used to derive discrete‐frequency reflection amplitudes from around the base of the CO2 storage reservoir. These are utilized to determine the lateral variation in peak tuning frequency across the seismic anomaly as this provides a direct proxy for the thickness of the causative feature.Under the assumption that the lateral and vertical extents of the respective saturation and pressure changes following CO2 injection will be significantly different, discrete spectral amplitudes are used to distinguish between the two effects. A clear spatial separation is observed in the distribution of low‐ and high‐frequency tuning. This is used to discriminate between direct fluid substitution of CO2, as a thin layer, and pressure changes that are distributed across a greater thickness of the storage reservoir. The results reveal a striking correlation with findings derived from pressure and saturation discrimination algorithms based on amplitude versus offset analysis.

Symmetries and asymmetries in chromatic discrimination

Under conditions of adaptation to a steady neutral field (metameric to Daylight Illuminant D65), forced-choice thresholds for color discrimination were measured for brief targets presented to the human fovea. Measurements were made along +45° and -45° lines in a MacLeod-Boynton chromaticity space scaled so that the locus of unique yellow and unique blue lay at -45°. The lines were symmetrical relative to the tritan line passing through the chromaticity of D65. Thresholds increased with distance of the probe chromaticity from D65. Thresholds were higher for saturation discrimination than for hue discrimination. A region of enhanced discrimination was found for thresholds measured orthogonally to the locus of unique blue and unique yellow. There may be an analogous enhancement near the loci of unique red and unique green.

Time-lapse pressure–saturation discrimination for CO2 storage at the Snøhvit field

At the Snøhvit field, Barents Sea, the produced gas contains 5–8% CO2. This is separated from the sales gas at the Melkøya LNG plant, piped back and re-injected into the saline aquifer Tubåen formation. The injected CO2 is monitored by time-lapse seismic data. Pressure and saturation changes are estimated by using near and far offset amplitude changes. The inverted pressure and saturation are used to predict expected time-shifts. The predicted time-shifts are then compared to conventional time-shifts estimated directly from the time-lapse seismic data. Empirical rock physics parameters linking pressure and saturation to the seismic parameters are estimated assuming linear relationships.The pressure effect dominates the time-lapse seismic data, except in the near well area where a fluid effect is also estimated. The pressure increase is strong in the near well area (up to 15MPa) and decreases rapidly with distance from the well. However, a continuous pressure buildup (4–5MPa) is estimated terminating against the faults approximately 1–2km away from the well. A CO2 saturation of 0.15–0.5 is estimated in the near well area, depending on the fluid distribution in the pores (uniform to patchy). There is a good correlation between predicted and conventional time-shifts. The empirical rock physics parameters indicate a CO2 saturation between 0.2 and 0.5, a patchy fluid distribution in the pore space is most likely. A pressure sensitivity corresponding to a Hertz–Mindlin exponent of 1/4 to 1/6 is estimated. This is clearly to high, and show that the uncertainties in the inverted rock physics parameters are high.

When does fading enhance perceptual category learning?

Training that uses exaggerated versions of a stimulus discrimination (fading) has sometimes been found to enhance category learning, mostly in studies involving animals and impaired populations. However, little is known about whether and when fading facilitates learning for typical individuals. This issue was explored in 7 experiments. In Experiments 1 and 2, observers discriminated stimuli based on a single sensory continuum (time duration and line length, respectively). Adaptive fading dramatically improved performance in training (unsurprisingly) but did not enhance learning as assessed in a final test. The same was true for nonadaptive linear fading (Experiment 3). However, when variation in length (predicting category membership) was embedded among other (category-irrelevant) variation, fading dramatically enhanced not only performance in training but also learning as assessed in a final test (Experiments 4 and 5). Fading also helped learners to acquire a color saturation discrimination amid category-irrelevant variation in hue and brightness, although this learning proved transitory after feedback was withdrawn (Experiment 7). Theoretical implications are discussed, and we argue that fading should have practical utility in naturalistic category learning tasks, which involve extremely high dimensional stimuli and many irrelevant dimensions.

Helical structure of complementary colors' relative spectral distribution function

I report a curious double helix in psychophysical data. As recently reported, color complementarism structures at least 40 functional roles in vision including all Red-, Green-, Blue-peaked functions (e.g., color matching functions, Helmholtz–Kohlrausch effect, saturation discrimination, lightness discrimination, and wavelength discrimination). These can be modeled from the relative spectral power distribution (SPD) function of complementary colors (at requisite power ratios to neutralize complements). So, the SPDs three-dimensional (3D) structure is of interest. Extended to the hue cycle, the SPD is plotted in a rectilinear graph of wavelength versus wavelength with radiance vertical to the plane. In this rectilinear color mixture space, the white locus representing the illuminant chromaticity is not a single point (representing the junction of complementary pairs of wavelengths) but a sinusoidal curve whose 3D structure is a double helix, representing an SPD and its complementary SPD. The structure's purpose is possibly to store and access global complementary colors data across illuminants. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 292–296, 2013

Effect of pore structure on electrical resistivity in carbonates

The electrical resistivity log has proven to be a powerful tool for lithology discrimination, correlation, porosity evaluation, hydrocarbon indication, and calculation of water saturation. Carbonate rocks develop a variety of pore types that can span several orders of magnitude in size and complexity. A link between the electrical resistivity and the carbonate pore structure has been inferred, although no detailed understanding of this relationship exists. Seventy-one plugs from outcrops and boreholes of carbonates from five different areas and ages were measured for electrical resistivity properties and quantitatively analyzed for pore structure using digital image analysis from thin sections. The analysis shows that in addition to porosity, the combined effect of microporosity, pore network complexity, pore size of the macropores, and absolute number of pores are all influential for the flow of electric charge. Samples with small pores and an intricate pore network have a low cementation factor, whereas samples with large pores and a simple pore network have high values for cementation factor. Samples with separate-vug porosity have the highest cementation factor. The results reveal that (1) in carbonate rocks, both pore structure and the absolute number of pores (and pore connections) seem more important in controlling the electrical resistivity, instead of the size of the pore throats, as suggested by previous modeling studies; (2) samples with high resistivity can have high permeability; large simple pores facilitate flow of fluid, but fewer numbers of pores limit the flow of electric charge; and (3) pore-structure characteristics can be estimated from electrical resistivity data and used to improve permeability estimates and refine calculations of water saturation.

Robust and Efficient Cotton Contamination Detection Method Based on HSI Color Space

摘要: 棉花杂质的有效检测和剔除对于棉花质量的控制具有重要意义. 本文提出了一种实用的棉花杂质高速检测方法. 该方法利用 3D-LUT 技术, 有效解决了颜色空间转换的时间耗损问题. 利用 HSI 颜色空间的色度和饱和度信息, 对棉花中的杂质进行高效检测和定位. 彩色运动补偿技术的应用, 弥补了相机在硬件上进行空间参数校正的不足, 降低了杂质的错误判别率. 实验结果表明, 该系统可以在 10ms 内完成 80 线棉流图像的采集、图像格式转换、杂质的检测和定位等全部过程. 在棉流速度为 18m/s, 杂质大小为 2×2mm2 的情况下, 杂质识别正确率可达到 95.4%. 关键词: HSI颜色空间 / 棉花杂质 / 查找表 / 运动补偿

Perceptual Functions in Prosopagnosia

Some patients with prosopagnosia may have an apperceptive basis to their recognition defect. Perceptual abnormalities have been reported in single cases or small series, but the causal link of such deficits to prosopagnosia is unclear. Our goal was to identify candidate perceptual processes that might contribute to prosopagnosia, by subjecting several prosopagnosic patients to a battery of functions that may be necessary for accurate facial perception. We tested seven prosopagnosic patients. Three had unilateral right occipitotemporal lesions, two had bilateral posterior occipitotemporal lesions, and one had right anterior-to-occipital temporal damage along with a small left temporal lesion. These lesions all included the fusiform face area, in contrast to one patient with bilateral anterior temporal lesions. Most patients had impaired performance on face-matching tests and difficulty with subcategory judgments for non-face objects. The most consistent deficits in patients with lesions involving the fusiform face area were impaired perception of spatial relations in dot patterns and reduced contrast sensitivity in the 4 to 8 cycles deg(-1) range. Patients with bilateral lesions were impaired in saturation discrimination. Luminance discrimination was normal in all but two patients, and spatial resolution was uniformly spared. Curvature and line-orientation discrimination were impaired in only one patient, who also had the most difficulty with more basic-level object recognition. We conclude that deficits in luminance, spatial resolution, curvature, line orientation, and contrast at low spatial frequencies are unlikely to contribute to apperceptive prosopagnosia. More relevant may be contrast sensitivity at higher spatial frequencies and the analysis of object spatial structure. Deficits in these functions may impair perception of subtle variations in object shape, and may be one mechanism by which the recognition defect in prosopagnosia can extend to other classes of object subcategorization.

Predicting glaucomatous sensitivity loss using perimetric color saturation test

Purpose To predict future glaucomatous sensitivity loss using a perimetric color saturation test (PCST) that measures the color saturation discrimination threshold for six hues (red, yellow, green, green-blue, blue, and purple) at 9° in horizontal and 3° in vertical extrafoveal points. Methods This new test was carried out on 31 patients (31 eyes) with early glaucoma or ocular hypertension. The sensitivity loss at the four points approximately 9.5° apart from the fixation point was prospectively evaluated annually for 3 years using the Humphrey Field Analyzer (HFA) program central 30-2. The initial results of PCST and the total deviation (TD) in the follow-up HFA results were compared. Results Twenty-seven patients (27 eyes) were followed up for 3 years. The color saturation threshold for six hues was correlated with the TD of HFA results at 108 points in the 27 eyes. The TD was −4 dB or better at the baseline measurement in 91 out of the 108 points. The averaged TD in the second and the third year in the follow-up period decreased below −4 dB in 10 of these 91 points, which were categorized as progression points in relation to the 81 nonprogression points. In the initial PCST, only the saturation threshold for purple was higher in the progression points when compared with the nonprogression points ( P = .0004, Mann-Whitney U-test). Conclusion Future sensitivity loss is most likely at the points where the threshold of color saturation discrimination is increased for purple in eyes with early glaucoma or ocular hypertension.

Developmental prosopagnosia: A study of three patients

We studied perception in three patients with prosopagnosia of childhood onset. All had trouble with other ‘within-category’ judgments. All were deficient on face matching tests and severely impaired on tests of perception of the spatial relations of facial features and abstract designs, indicating a deficit in the encoding of coordinate relationships, similar to adult-onset prosopagnosia with lesions of the fusiform face area. Two had difficulty perceiving feature colour, which correlated with reduced luminance sensitivity. In contrast to adult-onset patients, saturation discrimination was spared in two and spatial resolution impaired in two. Curvature discrimination was relatively spared. Contrast sensitivity showed variable reductions at different spatial frequencies. We conclude that developmental prosopagnosia is similar to the adult-onset form in encoding deficits for the spatial arrangement of facial elements. Deficits in luminance perception and spatial resolution are more associated with defective encoding for basic object-level recognition, as shown on tests of object and spatial perception.

On saturation and related parameters following Guth's ATD colour‐vision model

AbstractIn this work, we have examined the influence of different parameters both on perceived saturation and saturation discrimination with unrelated colours, on the basis of S. L. Guth's CA90 colour‐vision model and its subsequent modifications. Our analysis of perceived saturation covered (1) spectral saturation functions at constant luminance, (2) saturation functions in constant colorimetric purity loci, (3) saturation vs. colorimetric purity functions, (4) saturation vs. luminance functions in the 1–1000 td range, and, finally, (5) the equal saturation loci in the xy color diagram. Regarding saturation discrimination, we focused on (1) saturation thresholds from white and from the locus, (2) the number of just noticeable steps from white to the spectral locus as a function of dominant wavelength, and (3) the colorimetric purity incremental threshold vs. colorimetric purity at constant dominant wavelength. Hunt's 1991 colour‐appearance model and the colour‐discrimination model by Yeh et al. (1993) were used for comparison purposes. The behavior predicted by Guth's and Hunt's models is qualitatively very similar in many issues, but they especially disagree on the dependence of saturation on luminance. For the discrimination task, Guth's model predicts spectral discrimination functions comparable with those predicted by Yeh et al., both from white and from the locus. Nevertheless, the models disagree on intermediate colorimetric purities for most wavelengths. The model is basically consistent with the experimental data except for the luminance dependence. On the other hand, the literature on discrimination is insufficient to determine which model is right. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 305–321, 2001

Macular Diseases—Application of Automated Static Perimetry and Optical Coherence Tomography

The usefulness of automated static perimetry and optical coherence tomography in the management of macular diseases has been described. Scotomata in eyes with central serous chorioretinopathy could be evaluated with central 10-degree automated static perimetry. The degree of visual field defects in eyes with the disease varied greatly with mean deviation of −10 dB or less in as many as 10% of the subjects. Although retinitis pigmentosa is a diffuse retinal dystrophy, eyes with a moderately advanced stage of retinitis pigmentosa should be managed as a macular disease, because the functioning retina is confined within the vascular arcade. The progressive nature in this stage of the disease could be demonstrated with a central 10-degree automated static perimetry measured once or twice a year and the use of univariate linear regression of mean deviation, in half of the patients with a mean follow-up period of 5 years. Functional recovery in eyes with exudative age-related macular degeneration after laser surgery or submacular surgery could be evaluated with central 10-degree automated static perimetry. Eyes with increased mean deviation in spite of reduced visual acuity after therapeutic intervention should also be evaluated. Macular function could also be evaluated using a color test. A newly developed color saturation discrimination test was applied to patients with age-related macular degeneration, retinitis pigmentosa, and cone dystrophy. The degree of dyschromatopsia was less in eyes with age-related macular degeneration than in those with retinitis pigmentosa or cone dystrophy with the same level of acuity loss. The highly protrusive nature of the orange-red nodule in eyes with idiopathic polypoidal choroidal vasculopathy was demonstrated with dimensional measurement with OCT. The degree of protrusion was greater than in eyes with serous pigment epithelial detachment, which suggests that the polypoidal lesion is covered with rigid tissues including Bruch's membrane. Parafoveal retinal sensitivity obtained with automated static perimetry was studied in correlation with retinal thickness measured using OCT in eyes with branch retinal vein occlusion showing macular edema without macular non-perfusion or massive retinal hemorrhages. The increased retinal thickness due to macular edema is closely correlated with retinal sensitivity both at the fovea and in the parafoveal area. Eighty-nine phakic eyes of 46 patients with retinitis pigmentosa patients were studied to detect cystoid macular edema using OCT. Cystoid lesions were observed in the macula in 12 eyes in 6 (13%) of 46 patients. Some eyes with OCT-proven cystoid macular edema did not show dye pooling in the fluorescein angiogram. The width of the total area of cystoid lesions was positively correlated with best-corrected visual acuity but the thickness of the neurosensory retina at the center of the fovea was not. OCT findings of successfully repaired macular holes were categorized into 3 groups. Eyes with U-type showed a normal foveal contour and a dark layer corresponding to the outer segment of photoreceptors. Eyes with V-type showed a notch in the surface of repaired neurosensory retina without a dark layer on the retinal pigment epithelium. Those with W-type showed a defect of the neurosensory retina, where the retinal pigment epithelium was exposed. The visual results were excellent in eyes with U-type, but poor in those with W-type.

Dichoptic discrimination of saturation

Dichoptic discrimination of saturation