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高温高压下甲烷在油里的溶解度大,水包油乳化钻井液中存在油相,钻井作业中钻井液静置期间如起下钻、工具故障抢修等时间过长,储层中的甲烷气体会扩散到井眼里。在钻高含硫化氢及二氧化碳气井时,高温高压条件下天然气更有可能到达与油完全互溶的状态。文章将储层内的水平段井眼的气体扩散区域划分为4个区,外滤饼区、内滤饼区、滤液滞留区、滤液未污染区,根据外滤饼区、内滤饼区、滤液滞留区不同计算参数条件,计算预测了在使用水包油乳化钻井液情况下,储层中天然气通过扩散穿过3个区后,进入储层内井眼段环空导致的环空含气质量浓度变化,对环空内含气质量浓度随扩散时间、含油浓度因素的变化进行了定量计算。用伽略金有限元方法求解,计算表明,气体扩散量随钻井液静置时间延长而增加,水基钻井液加入油后与不加油的钻井液相比增大了气体扩散量。 相似文献
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A coupled finite-element model, CON2D, has been developed to simulate temperature, stress, and shape development during the
continuous casting of steel, both in and below the mold. The model simulates a transverse section of the strand in generalized
plane strain as it moves down at the casting speed. It includes the effects of heat conduction, solidification, nonuniform
superheat dissipation due to turbulent fluid flow, mutual dependence of the heat transfer and shrinkage on the size of the
interfacial gap, the taper of the mold wall, and the thermal distortion of the mold. The stress model features an elastic-viscoplastic
creep constitutive equation that accounts for the different responses of the liquid, semisolid, delta-ferrite, and austenite
phases. Functions depending on temperature and composition are employed for properties such as thermal linear expansion. A
contact algorithm is used to prevent penetration of the shell into the mold wall due to the internal liquid pressure. An efficient
two-step algorithm is used to integrate these highly nonlinear equations. The model is validated with an analytical solution
for both temperature and stress in a solidifying slab. It is applied to simulate continuous casting of a 120 mm billet and
compares favorably with plant measurements of mold wall temperature, total heat removal, and shell thickness, including thinning
of the corner. The model is ready to investigate issues in continuous casting such as mold taper optimization, minimum shell
thickness to avoid breakouts, and maximum casting speed to avoid hot-tear crack formation due to submold bulging. 相似文献
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Data mining extracts implicit, previously unknown, and potentially useful information from databases. Many approaches have been proposed to extract information, and one of the most important ones is finding association rules. Although a large amount of research has been devoted to this subject, none of it finds association rules from directed acyclic graph (DAG) data. Without such a mining method, the hidden knowledge, if any, cannot be discovered from the databases storing DAG data such as family genealogy profiles, product structures, XML documents, task precedence relations, and course structures. In this article, we define a new kind of association rule in DAG databases called the predecessor–successor rule, where a node x is a predecessor of another node y if we can find a path in DAG where x appears before y. The predecessor–successor rules enable us to observe how the characteristics of the predecessors influence the successors. An approach containing four stages is proposed to discover the predecessor–successor rules. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 621–637, 2006. 相似文献