Production Test Data Research Articles

Evaluating methods for logging the pore structure of tight sandstone reservoir in Chang 6 member of the Yanchang Formation, Ordos Basin

Pore structure is a key parameter used to evaluate reservoir quality. At present, experimental method is the most important method to analyze reservoir pore structure. However, coring data may be limited, and it is not possible to perform experimental analyses on all cores. Therefore, the researchers explored the use of logging techniques to study the pore structure of reservoirs. The relationship between pore geometry index (PGI), pore permeability and mercury injection parameters was analyzed based on mercury injection experiment, thin slice analysis, production test data and well logging data. These results can then determine the response characteristics of the logging parameters that correspond to different pore structures and establish a method of modeling the PGI through a multiple parameter regression and neural network method. This research shows that: (1) PGI can quantitatively characterize pore structure, and the maximum pore throat radius, displacement pressure and flow unit index have the highest correlation with PGI, which can be accurately characterized by practical formulas; (2) Natural gamma ray, natural potential amplitude difference, acoustic transit time, density, compensated neutron, deep and shallow resistivity logging data can reflect the quality of the reservoir pore structure. However, there are limitations in evaluating reservoir pore structure with a single logging parameter. Multi-parameter regression method and neural network method realize the quantitative calculation of pore structure from the perspective of multi-parameter and nonlinear. (3) The neural network method and multiple parameter regression method are used to study the pore structure of reservoir and realize the continuous quantitative calculation of pore structure index in a single well. It can be used in uncored analysis Wells and as one of the parameters to evaluate reservoir pore structure.

Multiphase Flow Behavior Prediction and Optimal Correlation Selection for Vertical Lift Performance in Faihaa Oil Field, Iraq

In the petroleum industry, multiphase flow dynamics within the tubing string have gained significant attention due to associated challenges. Accurately predicting pressure drops and wellbore pressures is crucial for the effective modeling of vertical lift performance (VLP). This study focuses on predicting the multiphase flow behavior in four wells located in the Faihaa oil field in southern Iraq, utilizing PIPESIM software. The process of selecting the most appropriate multiphase correlation was performed by utilizing production test data to construct a comprehensive survey data catalog. Subsequently, the results were compared with the correlations available within the PIPESIM software. The outcomes reveal that the Hagedorn and Brown (HB) correlation provides the most accurate correlation for calculating pressure in FH-1 and FH-3 while the Beggs and Brill original (BBO) correlation proves to be the optimal fit for wells FH-2 and Gomez mechanistic model for FH-4. These correlations show the lowest root mean square (RMS) values of 11.5, 7.56, 8.889, and 6.622 for the four wells, respectively, accompanied by the lowest error ratios of 0.00692%, 0.00033%, 0.00787%, and 0.0011%, respectively. Conversely, Beggs and Brill original (BBO) correlation yields less accurate results in predicting pressure drop for FH-1 compared with other correlations. Similarly, correlations, such as Orkiszewski for FH-2, Duns and Ros for FH-3, and ANSARI for FH-4, also display less accuracy level. Notably, the study also identifies that single-phase flow dominates within the tubing string until a depth of 6000 feet in most wells, beyond which slug flow emerges, introducing significant production challenges. As a result, the study recommends carefully selecting optimal operational conditions encompassing variables such as wellhead pressure, tubing dimensions, and other pertinent parameters. This approach is crucial to prevent the onset of slug flow regime and thus mitigate associated production challenges.

A quantitative evaluation model for biodegraded reservoirs based on multinomial logistic regression

The application of multiple evaluation technologies is a prerequisite for improving the probability of correctly identifying the type of a given reservoir (e.g., gas, oil, or biodegraded oil reservoirs). The traditional identification methods do not consider the graphical information conveyed by the total gas curves from mud logging and the pyrograms from pyrolysis-gas chromatography (Py-GC). To improve the accuracy of the predictions, this research proposed a new reservoir-identification methodology that incorporates the graphical information carried by the total gas curves and the pyrograms from Py-GC. The proposed model is applied to Daliuquan Structural Belt to test its performance. Sensitive parameters (the Tg values, the shape of the total gas curve acquired from mud logging, the content of methane in the mud gas, the Pg values, the TPI values, and the patterns of the Py-GC chromatogram) used in this model for reservoir evaluations are determined based on reservoir characterization results. The graphic information carried by the total gas curves from mud logging and the pyrograms from Py-GC is converted into probability problems using multinomial logistic regression in Statistical Package for the Social Sciences (SPSS) software. The well logging data of 137 layers are used to validate the model, and the predictions of the model are compared with the production test data. The overall prediction accuracy of the proposed model is 91.2%. The proposed model is subsequently used to predict the types of 23 reservoirs that are not used in the regression process. The results show that the probability of correctly identifying the types of these reservoirs verified by production tests is 78.3%.

Saturation Determination and Fluid Identification in Carbonate Rocks Based on Well Logging Data: A Middle Eastern Case Study

In the Middle East, there remain many technical challenges in the water saturation evaluation of carbonate rocks and the effective identification of reservoir fluid properties. The traditional Archie equation is not applicable to carbonate reservoirs with complex pore structures and varying reservoir space distribution, as there are obvious “non-Archie” phenomena. In this paper, by analyzing the experimental data on the rock resistivity of the target formation in the study area and analyzing the relationship between stratigraphic factors and porosity, the previous fitting method was modified as a result of using the actual data while avoiding the cementation index as a way to improve Archie’s formula to evaluate the water saturation. Based on the improved Archie formula, the mathematical differential operation of water saturation and porosity was carried out using the formation resistivity. The calculation results of irreducible water saturation were used to calibrate the oil layer, and the water layer was calibrated when the water saturation was 100%, allowing for a novel reservoir fluid property identification method. This total differential method can effectively identify the oil-down-to (ODT) and water-up-to (WUT) levels in an oil–water system and then accurately divide the transition zone of the oil–water layer. When this method was applied, the identification results were in good agreement with production conclusions and test data with an accuracy rate of 89.95%. Although the use of geophysical logging data from open-hole wells combined with the total differential method is only applicable to wells with similar logging time and production time, it is possible to compare geophysical logging data from different periods to construct oil–water profiles to observe the changes in ODT over time to guide development and adjust production plans. The proposed reservoir fluid property identification method and the improved water saturation calculation formula can meet the requirements of water saturation evaluation in the target block with low calculation cost and easy implementation, which provides a new method for water saturation evaluation and rapid identification of reservoir fluid properties.

Petroleum exploration breakthrough and geological significance in Cretaceous Yingcheng and Denglouku formations of Shuangcheng area, northern Songliao Basin, NE China

Based on drilling geological, geochemical, geophysical and production test data, the characteristics of source rocks, reservoir rocks and caprocks, as well as the process of hydrocarbon generation, trap evolution and oil accumulation of the oil-bearing assemblage composed of the Cretaceous Yingcheng Formation (K1yc) and Denglouku Formation (K1d) in the Shuangcheng area, northern Songliao Basin, NE China, were analyzed by using the research methods for petroleum systems. The source rocks mainly exist in K1yc, with the organic matters mainly originated from lower aquatic organisms and algae, and reaching the grade of high-quality source rock in terms of organic abundance. The crude oil, which is characterized by low density, high freezing point and high wax content, is believed to have generated by the K1yc source rocks. The reservoir rocks include K1d sandstones and K1yc glutenites. The mudstone in the fourth member of K1d serves as the direct caprock of the oil reservoir. The oil was generated during the period between Yaojia Formation and Nenjiang Formation, and then accumulated during the periods of Nenjiang Formation and Paleogene–Neogene. The traps evolved in three stages: the late Yingcheng Formation, the late Quantou Formation and the late Nenjiang Formation, forming structural and structural-lithologic reservoirs. It is concluded that good source-reservoir-caprock assemblage, late hydrocarbon charging, short migration distance and stable tectonic setting are favorable factors for the formation of oil reservoirs.

Оценка вероятности отказа при эксплуатации сборного режущего инструмента со сменными многогранными пластинами методами непараметрической статистики

The article discusses the issues of durability of a prefabricated cutting tool in the process of metal cutting, as well as the risk of loss of its operability. In the course of assessing the probability of tool failure in violation of the established wear criterion, the results of a production experiment are used when roughing the Shaft part made of a rod with a diameter of ø 58 mm made of HN77TYUR alloy. The processing of the part is carried out with a prefabricated cutting tool with replaceable polyhedral plates of round and square shape, having a special type of alloys: VK6m, VK8 and T15K6. To evaluate the results obtained and describe their distribution, the authors use the Shapiro–Wilk agreement criterion to check the correlation between the initial data and the corresponding assumption of their normal distribution. Since the obtained production test data do not obey the normal distribution law, the nonparametric Parsen–Rosenblatt method is used for further analysis.

Intelligent calculation method of relative sonic attenuation and its application to fracture evaluation in tight sandstone reservoir

Fractured tight reservoirs have widespread exploration and development prospects. For these types of reservoirs, fractures provide pathways for fluid flow and storage spaces for tight oil and gas, which play a significant role in increasing production. In order to explore a fine fracture evaluation scheme for tight reservoirs, we firstly proposed an intelligent calculation method for the relative sonic attenuation; and then developed a novel semi-quantitative evaluation approach for the equivalent fracture width based on relative sonic attenuation and physical experimental results of the effect of fracture on sonic attenuation. The acoustic experimental results of the models with fractures show that the S-wave relative attenuation coefficients have a good correlation with the fracture attribute parameters. This lays a foundation for the fine fracture evaluation based on attenuation information. Field application results of the intelligent calculation method for relative attenuation and the inversion method for fracture width have been validated by comparing them with results from image logging, S-wave anisotropy estimation, and production test data, which demonstrates the feasibility and correctness of the proposed methods. The investigation depth of the proposed fracture evaluation scheme based on acoustic attenuation is significantly larger than that of the image logging, which provides a new optional scheme for fine fracture evaluation, especially for effective fracture evaluation; and it makes up for the deficiencies of the image logging fracture evaluation method.

Microfacies and Reservoir Connectivity of Shore Sandbar, Southern Indus Basin, Pakistan

Shore sand bar reservoirs have attracted much attention as one of the target intervals with the greatest potential for petroleum exploration and development in marine sedimentary basins. Nevertheless, due to lack of effective research methods, it is difficult to analyze the rapid lateral change and heterogeneity in a sand bar reservoir, which has a major impact on the efficient petroleum development that seriously restricts the rolling evaluation and efficient development of sand-bar reservoirs. In this study, based on integrated analysis of cores, thin sections, logging, 3D seismic data, production test and dynamic data, through a combination analysis of drilling and seismic interpretation data—the petromineral composition, microfacies and reservoir connectivity of the shore sand bar in the southern Indus basin are investigated, which is used for the fine description of the sandbar reservoir. The results show that the shore sand bar is located in a relatively high-energy shore sedimentary environment, which is conducive to forming a favorable lithologic reservoir. Four sedimentary microfacies types are identified, including center bar, bar edge, inter bar and local mudstone interbeds. The sandbar microfacies are changed rapidly, and different microfacies types overlap each other, especially the inter bar and local mudstone interbeds that overlap and intersect in the center bar and bar edge, which significantly reduces the internal reservoir connectivity as well as intensifying the heterogeneity of the sandbar reservoir. The sandbar reservoir is not connected transversely, the physical properties are changing rapidly, and the sandbar reservoir is cut into several relatively independent oil reservoirs.

Application of Edge Computing in the Quality Control of Cable Production Process

Given the lack of quantifiable evaluation criteria for the quality supervision and control in the existing power cable industry, insufficient research on the correlation of production indexes in the production process, and low timeliness in the analysis and processing of massive multi-source production data, the video monitoring model and data-driven process quality evaluation strategy model under the edge computing framework were constructed. Next, all the production data and test data in the cable production procedures were captured using edge nodes, and the factory-side data was cleansed, processed, and analyzed. The cable manufacturing quality was evaluated through edge computing, and the business process was arranged based on the edge computing results, so as to improve the cable product quality and finally optimize the total value chain of production in the whole cable industry.

Reducing Uncertainty In Log Analysis Due To Presence Of Heavy-Conductive Minerals In Sendimentary Rocks

Presence of heavy-conductive mineral(s) in formation rocks tends to provide negative influence to some log readings especially the resistivity log. With regard to its function in log analysis, any distortion in resistivity log readings will certainly lead to potential misinterpretation on petrophysical properties such as water saturation (S.) Therefore a method dedicated to minimizing the effect is indeed necessary.This paper presents results of a study on presence of heavy-conductive minerals, distributed in structural form, on resistivity reading. Based on analogy and expansion of a structural clay distribution model, a correction method plus its application procedure have been proposed. Since the method is develop using an approach that is considered valid in general term it is, therefore, conceptually applicable to any field cases as long as its theoretical conditions are met. In order to make application of the method easier it has also been presented in form of nomographs.Application of the method on log analysis of two wells in West Java has proved itself well in which corrections on calculated water saturation have yielded values that are more consistent when compared to production test data. The method is also prepared in a manner that it can be easily integrated into standard log analysis practices.

Geological Characteristics and Controlling Factors of Enrichment of Deep Shale Gas in the East Weiyuan–North Rongchang Area, Sichuan Basin, China

The southern Sichuan Basin is the core area of China’s efficient development of deep shale gas (burial depth greater than 3,500 m). Reservoir geological characteristics determine whether shale gas can be preserved, enriched, and produced. Taking the Long 11 sub-member of the Wufeng Formation of the Upper Ordovician and the Longmaxi Formation of the Lower Silurian in the East Weiyuan–North Rongchang area as an example, we used the core, logging, production test, and other data, combining X-ray diffraction analysis, LECO Total Organic Carbon (TOC)-S analysis, optical microscopy, and argon ion polishing field-emission scanning electron microscopy, to study the shale mineral composition, geochemistry, reservoir space, pore structure characteristics, and reservoir physical properties. The following results were obtained: 1) The brittle mineral content, organic matter maturity, and TOC content are high, gradually increase from top to bottom, and reach their maxima at small layer 1 of Long 11. 2) Organic pores, inorganic pores, and fractures are important reservoir spaces, among which organic pores and fractures are important seepage channels for shale gas. 3) The shale pore structure revealed by electron microscopy shows that the pore structure in target layers can be divided into four types: unimodal type (mainly organic pores), bimodal type (both organic and inorganic pores), monoclinic type I (mainly organic pores), and monoclinic type II (mainly inorganic pores). The pore morphology is complex, and circular and oval shapes predominate. 4) Sedimentary facies are the main factor controlling the enrichment of shale gas, and the development of fractures is the key to obtaining high yields of shale gas. 5) The class I favorable target area is mainly distributed in wells W206, W206H1, R234H, and R233H and areas to its south, and some areas in the east of the study area.

Numerical and experimental investigation on a downhole gas-liquid separator for natural gas hydrate exploitation

Natural gas hydrate (NGH) is widely considered as an alternative energy source due to its tremendous reserves, cleanness and high energy density. During the exploitation process, discharging the gas-liquid phase to the surface for separation not only affects the pump performance but also increases the space requirements of the offshore platform. Taking NGH production test data in South China Sea for example, a downhole spiral gas-liquid separator is designed for high gas-liquid ratio (liquid content is less than 10%) in this paper. The forces of droplets in the separator are analyzed and the CFD model for gas-liquid two phase flow is established. The RNG k-ε turbulence model is used for analyzing the velocity field distribution and the pressure field distribution in the separator. The influence of structure parameters (pitch, cycle number of spiral piece, and the outer diameter of spiral pipe) and scale on the separation performance is investigated. The energy loss increases sharply after scaling in the separator and some necessary measures should be taken to avoid the generation of the sale and the secondary hydrate. Based on steepest ascent design, response surface methodology and particle swarm optimization, the optimal structure of the separator with high separation efficiency 87.26% and low pressure drop 2614.19Pa is obtained. The experimental platform is built for testing the gas-liquid separator. The comparison of numerical simulations and experiments show that the calculation model for the hydrate gas-liquid separation is correct and feasible. The separation device with the optimal structural parameters has good separation performance.

A Robust Short-Term Oil Production under a Bow-Tie Uncertainty Set for the Gas Lift Performance Curve

SummaryThe method of continuous gas lift has been commonly used in the oil industry to enhance production. Existing optimization models consider an approximate performance curve anchored by production test data, often disregarding reservoir uncertainty. We propose a robust optimization model that jointly considers the most recent data and an uncertainty set for the reservoir pressure, a critical parameter that is usually not measured precisely. As a result, we obtain what we call a “bow-tie” uncertainty set for the performance curves, in which the performance uncertainty increases when we move away from the production test’s operational point. We test our model with real data from an offshore oil platform and compare it against a fully deterministic model. We show superior out-of-sample performance for the robust model under different probability distributions of the reservoir pressure.

IMPROVING STUDENTS’ ENGLISH PRONUNCIATION THROUGH LISTENING TO ENGLISH SONGS AT THE SECOND GRADE STUDENTS OF SMP SWASTA HARVARD MARTUBUNG

The objective of this study was to investigate whether listening to English songs significantly improve students’ English pronunciation by conducting Classroom Action Research (CAR). The subject of this research was the second grade of SMP Swasta Harvard Martubung which consisted of 30 students and was conducted in two cycles. The instrument of collecting data was quantitative data Sound Production Test (Test Produksi Suara) and qualitative data (observation sheet). Based on data analysis, the score of students’ Sound Production Test improved in every test. In the result of students’ tests were showed that the mean score of pre-test was 52,3. The mean score of post-test in Cycle I was 65,7. The mean score of post-test in Cycle II was 81,2. Based on observation sheet, it was found that teaching learning process ran well. After giving the treatment by listening to English songs, the students’ English Pronunciation in pronouncing English words improved. It was concluded that listening to English songs can improve the students’ English Pronunciation.

Early Detection of Product Reliability Based on the Parameters of the Production Line and Warranty Data

Reliability is one of the key dimensions of the quality of services and products that should be always evaluated. Growth and development of industries can be achieved by appropriate reliability engineering of products. Companies should evaluate and predict the reliability of products and accordingly find and fix the potential problems. In this regard, early detection of reliability problems based on the parameters of the production line or quality test results can prevent future warranty costs. Early detection of reliability problems based on production process and test data has not gained much attention in the literature. Therefore, an early detection model for predicting the reliability of products according to their quality test results is proposed in this research. For this purpose, hot test and warranty data of car engines manufactured by an automotive company are utilized. This data are prepared to predict engine reliability after preprocessing and removing inefficient data. Then, engines are divided into two homogeneous clusters using particle swarm optimization (PSO) clustering algorithm. Afterwards, the data in these clusters are used to feed the Artificial Neural Network (ANN) to predict the reliability of the engines. The obtained results show that the proposed ANN-based method is able to predict the reliability of the engines based on engine kilometers operated and hot test results. Also, it is shown that the proposed method outperforms the Cox proportional hazards model which has previously been used for early detection of product reliability.

The Implementation of Flow Performance Test to Monitor Well Performance in Geothermal Field

Reservoir monitoring of a geothermal field has an important role in determining the direction of company policies in managing a geothermal field, one of which needs to be monitored is by looking at changes in the pattern of the deliverability curve so that it can determine changes in the characteristics and performance of production wells. In order to update the deliverability curve, it is necessary to conduct periodic production tests. However, this cannot be done due to limited steam reserves. This research was conducted to determine the performance of production wells using the Flow Performance Test (FPT) method. This method is an alternative solution that can update the production well deliverability curve without leaving the gathering system. The FPT is applied to UBL-DL5 and JL2, UBL-JL3 is shown to validate the equations used. The data obtained were validated with TFT data and production test data where the deviation of the data obtained for UBL-DL5 was 1.42%, UBL-JL2 was 2.7%, and UBL-JL3 was 2.74%. The comparison of the UBL-DL5 and JL3 models based on time shows a significant production decline, and this is possible because the wells have only been operating within a period of 4 months – 1 year where the condition of production wells are still looking for stable condition, while the UBL-JL2 have not been seen there is a change in characteristic. The FPT is reliable enough to be used as an alternative method in monitoring production wells compared to the TFT method and the horizontal lip pressure production test. The FPT program should be conducted periodically and synchronized with the company’s operational activities plan. The delivery curve modeling as FPT result is used to monitor production wells’ condition as the basis for the company to develop a dynamic five-year work plan.

Formation conditions and enrichment model of retained petroleum in lacustrine shale: A case study of the Paleogene in Huanghua depression, Bohai Bay Basin, China

Abstract Compared with marine facies shale strata, lacustrine shale strata are more complicated in geological conditions, and thus more difficult to explore and develop. To realize economic exploration and development of lacustrine shale oil, the geological regularities of accumulation and high yield of retained movable petroleum in shale should be understood first. In this work, taking the shale strata of Kong 2 Member and Sha 3 Member in the Paleogene of Huanghua depression in the Bohai Bay Basin as examples, based on the previous joint analysis results of over ten thousand core samples and the latest oil testing, production test and geochemical data of more than 30 horizontal wells, accumulation conditions and models of retained movable petroleum in lacustrine shale were studied comprehensively. The study shows that at moderate organic matter abundance (with TOC from 2% to 4%), shale strata have the best match between oil content and brittleness, and thus are rich in oil and good in fracability. Moderate ancient lake basin size and moderate sediment supply intensity are the internal factors leading to best coupling of organic matter abundance and brittle mineral content in the shale formation. Moderate thermal evolution maturity of Ro of 0.7%–1.0% (at burial depth of 3200 to 4300 m) is the interval where oil generation from thermal evolution and oil adsorption by kerogen in shale layers match best, and retained movable petroleum is high in proportion. Moderate diagenetic evolution stage (3200 to 4300 m in the middle diagenetic stage A) is conducive to the formation of a large number of dissolved pores and organic matter pores, which provide storage space for shale oil enrichment. Moderate development degree of natural fractures (without damaging the shale oil roof and floor sealing conditions) is conducive to the storage, seepage and preservation of shale oil. The research results have overthrown the general understanding that high organic matter abundance, high maturity, and high development degree of natural fractures are conducive to shale oil enrichment, and have guided the comprehensive evaluation of shale oil and gas sweet spots and well deployment in the second member of the Kongdian Formation in the Cangdong sag and the Shahejie Formation in the Qikou sag. Industrial development of the shale oil in Kong 2 Member of the Cangdong sag has made major breakthrough, and important signs of shale oil have been found in Sha 3 Member of the Qikou sag, demonstrating huge exploration potential of lacustrine shale oil.

Recognition of the Lower Limit of Reservoir Physical Properties

The lower limit of reservoir physical properties is an important parameter for identifying the reservoir and determining the effective thickness in the reserve evaluation, and it is also an important basis for selecting the test interval in the oilfield exploration and development. In view of the basicity and necessity of studying the lower limit of reservoir physical properties, related determination methods have been the research hotspots of reservoir engineers. Existing research results show that the lower limit of the reservoir physical properties is determined under the established process technology conditions, but the lower limit of the reservoir physical properties changes with the development of oil and gas extraction technology. As the basis of effective thickness determination and reserve calculation, the sole determination of the lower limit of the reservoir physical properties is acceptable, and its changes or uncertainties are difficult to understand. Understanding the root cause of this contradictory problem theoretically is of great significance to further research on the lower limit of reservoir physical properties. Therefore, from the perspective of percolation, the author reunderstands the lower limit of the physical properties of the reservoir on the basis of systematically sorting out the difference in percolation capacity of pores of different sizes in the reservoir. The results show that: ①There are three types of lower limit of reservoir physical properties, including the lower limit of theoretical physical properties, the lower limit of producing physical properties, and the lower limit of filling physical properties. Among them, the lower limit of theoretical physical properties is the minimum effective porosity and minimum permeability of the reservoir capable of storing and percolating fluid, and its size depends on the geological conditions of the reservoir; the lower limit of producing physical properties is the minimum effective porosity and minimum permeability of a reservoir that can store and percolate fluid under production conditions, and its size depends on both the reservoir geological conditions and the production conditions of the reservoir; the lower limit of filling physical properties is the minimum effective porosity and minimum permeability of a reservoir that can store and percolate oil and gas under the state of reservoir forming, and its size depends on both the reservoir geological conditions and the reservoir forming conditions. Among the three, the lower limit of theoretical physical properties is the smallest, and the lower limit of producing physical properties and the lower limit of filling physical properties are relatively large. ②At present, the lower limit of reservoir physical properties is mainly determined based on core physical property analysis, oil test and production test data, therefore, it should be the lower limit of producing physical properties. And the lower limit of producing physical properties is closely related to the production conditions, so it is uncertain. On the contrary, the lower limit of theoretical physical properties and the lower limit of filling physical properties are irrelevant to production conditions, so they are certain. ③The study of the lower limit of reservoir physical properties should be based on the theoretical lower limit and the filling lower limit, while the producing lower limit can reflect the changes in production conditions and can be used as a dynamic index to measure oilfield development, but it should not be used as the focus of research on the lower limit of reservoir physical properties.

Black-Box Test-Cost Reduction Based on Bayesian Network Models

The growing complexity of circuit boards makes manufacturing test increasingly expensive. In order to reduce test cost, a number of test selection methods have been proposed in the literature. However, only few of these methods can be applied to black-box test-cost reduction. In this article, we propose a novel black-box test selection method based on Bayesian networks (BNs), which extract the strong relationship among tests. First, the problem of reducing the black-box test cost is formulated as a constrained optimization problem. Next, multiple structure learning and transfer learning algorithms are implemented to construct BN models. Based on these BN models, we propose an iterative test selection method with a new metric, Bayesian index, for test-cost reduction. In addition, averaging strategies are applied to enhance the reduction performance. Finally, a robust model selection framework is proposed to select the optimal BN model for test-cost reduction. Two case studies with production test data demonstrate that when no prior information is provided, our proposed approach effectively reduces the test cost by up to 14.7%, compared to the state-of-the-art greedy algorithm. Moreover, our proposed approach further reduces the test cost by up to 7.1% when prior information is provided from similar products.

Rebuilding the wheelset flanges of locomotives by surfacing without wheeling out

The most effective method to increase the surface life of wheel tires, the flange wear of which outpaces the growth of tire wear significantly, is surfacing of worn flanges of electric locomotive wheel sets. This method, in comparison with the restoration by turning and forming a profile configuration by reducing the thickness of the tire has undeniable advantages: flange surfacing combined with the shape of female profile minimizes the technological wear of the tire before its retirement; idle time of locomotives caused by the need of intermediate turning is eliminated; the costs of maintaining the machines for turning without removing the wheels and purchasing hard-alloyed cutting tools are decreased; wage savings are achieved. The work presents basic information on wheel sets, theoretical data on surfacing, analyzes previously used surfacing materials and provides metallographic studies of the surfaced material. The technology of flange surfacing without removing the wheels from under the electric locomotive was developed and described, that allows reducing the time spent on repair significantly. The use of alloyed surfacing materials instead of low-carbon ones allows reducing the time of surfacing and increasing the resistance to wear of wheel set flanges of traction vehicles. Efficiency of NP-18H1G1M.01 surfacing wire application for wear-resistant surfacing of tire flanges and increase of the overhaul cycle is shown. Increased wear resistance of electric locomotive wheel flanges surfaced with alloyed wire is confirmed by the production test data.