Browsing by Author "Zhang, Tao"
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- Downhole gas-kick transient simulation and detection with downhole dual-measurement points in water-based drilling fluid
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2020-12) Wang, Chao; Liu, Gonghui; Yang, Zhirong; Li, Jun; Zhang, Tao; Jiang, Hailong; He, Miao; Luo, Ming; Li, WentuoGas kick is generally difficult to discover in time using traditional surface detection methods, which results in a significant wastage of time and money. Owing to the restriction of the low data-transmission speed of measurement-while-drilling system, downhole measured data is usually ignored in gas-kick detection. Furthermore, surface detection methods comprising the use of pressure and flow-rate sensors require professional knowledge and many input parameters, some of which are required to be assumed. In this study, we used downhole dual measurement points for detecting gas kick without the use of other surface input parameters. Firstly, we developed an end-to-end supervised neural network to determine the still and circulation working conditions, which were used for calculating the drilling fluid density and viscosity. Secondly, an unscented Kalman filter was applied to perform a backward gas fraction calculation dynamically. However, this downhole calculation method cannot be used in highly deviated and horizontal wells. Because there is a downhole fluctuating pressure generated during the rock breaking, we proposed an auxiliary gas-kick detection method based on the theory of pressure wave attenuation. This method can be applied to all well types. To evaluate the proposed gas-kick detection method, we used a gas-liquid flow simulation model combined with a pump rate model, screw-drilling-tool pressure-consumption model, rock-breaking model, and formation permeability model to generate transient data with the highest possible accuracy. The advection upstream splitting model was used as the numerical scheme. The accuracy of the simulation model was successfully validated using two field experimental data sets. Finally, we generated a set of vertical and horizontal well data each with the simulation model to test the gas-kick detection method. The experiment results showed that the proposed gas-kick detection model was successful in detecting gas kick and obtaining the accurate gas fraction. - Internal sizing of different hardwood species
Helsinki University of Technology | Master's thesis(2009) Zhang, TaoIn order to improve profitability, uncoated fine paper mills nowadays utilize large proportion fast-growing hardwood pulp, calcium carbonate filler, and in Asia also non-wood pulp, which raw materials could contribute good optical properties and favourable formation to paper. On the other hand, some challenges from papermaking and paper-printing are apparently induced and naturally related to these raw materials, such as high consumption wet-end chemicals consumption and printing picking problem. Botnia has already supplied Asia markets eucalyptus pulp with high fiber property. The objective of this thesis was to characterize the performance of two hardwood pulp grades at internal sizing process during uncoated fine paper making and to clarify the differences between pulp grades. The comparison of two wheat straw pulp grades as complement pulp was also included into this study. The fiber and pulp properties of raw pulp and stock pulp have been thoroughly analyzed in several laboratories according to industry standards, which fundamental properties or modified ones by mechanical treatments contribute the performance of pulp grades in final paper products. After papermaking trials, the parameters of papermaking process, and the properties of ASA sized fine paper have been also measured to be evident for the various performance of pulp materials. The released organic substances (COD, cationic demand) and WRV of Euca pulp reach higher level than Acacia pulp after refining, which differences drive Euca pulp to consume more ASA size and to receive lower dry content after press than Acacia pulp. Acacia pulp possesses large fiber population per gram, which may lead at same basis weight into high dense, low porosity, and high smoothness for uncalendered paper. Low porosity of uncoated fine paper enables high initial pressure for liquid penetration, which is favourable for good sizing degree. Generally, more wheat straw pulp content in paper furnishes more difficulty it is for ASA sizing. With low amount of released organic substances, however, Novel straw pulp has performed inferior sizing efficiency in comparison with Soda straw pulp, which phenomenon is opposite to hardwood or traditional pulp. - Train Localization Environmental Scenario Identification Using Features Extracted from Historical Data
A4 Artikkeli konferenssijulkaisussa(2021) Zhang, Tao; Cai, Baigen; Lu, Debiao; Wang, Jian; Xiao, YuThe application of Global Navigation Satellite System (GNSS) on the railway greatly reduces the cost on train localization. However, the railway environment is complex and changes with the train movement, buildings, trees, railroad cuts and mountains will block and reflect the GNSS signals, which will bring errors to the GNSS-based train position estimation. This paper proposes a railway scenario identification method based on historical GNSS receiver observation data to identify scenarios along the railway. Firstly, a railway environment scenario parameter model library is established according to Feature of Sky Occlusion (FSO) of typical scenarios, apply historical GNSS observation data along the railway to establish the FSO models of scenario segments, and generate FSO feature sequences. The dynamic time warping algorithm (DTW) is used to match the FSO parameter model of the scenario segment with the FSO model library. This paper collected data from field experiments at Beijing Sanjiadian station to verify the algorithm. The scenario identification results showed that the scenario identification method based on DTW can effectively identify the railway scenarios.