Experimental Research on Supercritical Carbon Dioxide Fracturing of Sedimentary Rock:A Critical Review

Supercritical carbon dioxide(ScCO_(2))fracturing has great advantages and prospects in both shale gas exploitation and CO_(2)storage.This paper reviews current laboratory experimental methods and results for sedimentary rocks fractured by ScCO_(2).The breakdown pressure,fracture parameters,mineral composition,bedding plane angle and permeability are discussed.We also compare the differences between sedimentary rock and granite fractured by ScCO_(2),ultimately noting problems and suggesting solutions and strategies for the future.The analysis found that the breakdown pressure of ScCO_(2)was reduced 6.52%–52.31%compared with that of using water.ScCO_(2)tends to produce a complex fracture morphology with significantly higher permeability.When compared with water,the fracture aperture of ScCO_(2)was decreased by 4.10%–72.33%,the tortuosity of ScCO_(2)was increased by 5.41%–70.98%and the fractal dimension of ScCO_(2)was increased by 4.55%–8.41%.The breakdown pressure of sandstone is more sensitive to the nature of the fracturing fluid,but fracture aperture is less sensitive to fracturing fluid than for shale and coal.Compared with granite,the tortuosity of sedimentary rock is more sensitive to the fracturing fluid and the fracture fractal dimension is less sensitive to the fracturing fluid.Existing research shows that ScCO_(2)has the advantages of low breakdown pressure,good fracture creation and environmental protection.It is recommended that research be conducted in terms of sample terms,experimental conditions,effectiveness evaluation and theoretical derivation in order to promote the application of ScCO_(2)reformed reservoirs in the future.

Development Features of Supercritical (Ultra-Supercritical) Technology in the World and Experiences We Can Learn

The development and technical characteristics in different stages of supercritical (ultra-Supercritical) technology abroad are introduced in this paper. At the same time, according to the development trend of supercritical (ultra-supercritical) technology, the corresponding revelations are given in this paper. That is: It is an inevitable choice to develop supercritical (ultra-supercritical) technology if we want to improve the thermal efficiency and heat efficiency.

Study on Calculation Method for Partition of Heat Transfer in an Ultra-supercritical Boiler

Use a 1000MW ultra-supercritical tower boiler as the research object. On the basis of one dimensional model, simplify the tube heat transfer model and the radiation heat transfer model;establish the two-dimensional area calculation model with the regional method;?summarize the heat load distribution of flue gas temperature and water wall surface;and compare with the measured data. The error range of the result is acceptable on the project. The distribution of water wall surface heat load along the furnace width and the area where heat transfer deterioration?cause easily along the furnace height direction are studied with the model and algorithm on different boiler load conditions. All these provide the reference for the design and operation of the ultra supercritical boiler.

Optimization of Honing Wheel Structure Parameters in Ultra-precision Plane Honing

Free abrasive particle machining in simple machine such as: honing, polishing can get higher surface finish mirror, but surface error, and working procedure is hard to control. Therefore, the vertical disposed ultra-precision plane honing method by ultra-particle diamond honing wheel is put forward to. The results of experiments indicate: plane-honing wheel has higher machining accuracy and machining efficiency. But at the same time the structure parameters of honing wheel effects on machining accuracy. By analyzing the relation of honing wheel structure parameters and workpiece machining accuracy, the relation of honing wheel and wear coefficient, then this paper gets honing wheel structure parameters in the condition of best accuracy coefficient and wear coefficient, and resolve the problem of choosing honing wheel structure parameters in ultra-precision plane honing at last. This paper analyses the relation of honing wheel structure parameters and workpiece machining accuracy coefficient and wear coefficient, by building relative movement math model of honing wheel and workpiece in plane honing. Through theory calculating, the result indicate: about honing machine tools for large volume manufacture, honing wheel wear is main effect factor, so honing wheel should adopt obverse triangle radial structure. About honing machining for high accuracy and low-batch quantities, machining accuracy coefficient is main factors; so honing wheel should adopt reverse triangle radial structure. Neglected the manufacturing factors of honing wheel, then we can design honing wheel with high power curve structure to meet the need of machining accuracy coefficient and honing wheel wear coefficient in higher accuracy honing.

Model Identification Based on Subspace Model Identification of Main Steam Temperature in Ultra-Supercritical Coal-Fired Power Unit

Ultra-supercritical(USC) unit is more and more popular in coal-fired power industry.In this paper,closed-loop identification based on subspace model identification(SMI) is introduced for superheated steam temperature system of USC unit.Closed-loop SMI is applied to building step response model of the unit directly.The parameters selection method is proposed to deal with the parameter sensitivity and improve the reliability of the model.Finally,the model is used in model identification of real USC unit.

Molecular dynamics simulation of supercritical CO2 microemulsion with ionic liquid domains: Structures and properties

Supercritical carbon dioxide microemulsions are great medium to combine two immiscible substances through forming nanoscale polar cores in nonpolar continuous phase with the help of proper surfactants. The properties of microemulsions could be significantly affected by their constituents and structures. In this work, molecular dynamics simulation was implemented to study supercritical carbon dioxide microemulsions containing ionic liquid [bmim][PF6] and water by adding surfactant Ls-36. Results showed that the above components could form spherical aggregates in CO2 bulk phase with [bmim][PF6] and some water as the inner core, surfactant headgroups and water as the intermediate shell, and surfactant tails as the outer shell. The microstructure information about the outer shell was further investigated by defining an angle between the surfactant tail and the normal direction of the aggregate outer surface, which ranged from 78° to 125°. The influence of the ionic liquid content on the size and structure of microemulsions was explored and the best molar ratio between the ionic liquid and surfactant was around 1.25 for getting maximum water solubility.

Solubility of the silver nitrate in supercritical carbon dioxide with ethanol and ethylene glycol as double cosolvents: Experimental determination and correlation

Solubility of the silver nitrate in the supercritical carbon dioxide containing ethanol and ethylene glycol as double cosolvents was measured under certain pressure and temperature range(10–25 MPa, 323.15–333.15 K). The impact of the pressure and temperature on the solubility was also investigated. Based on the experiment data,a correlation model concerning solid's solubility in supercritical fluids was established by combining the solubility parameter with the thermodynamic equation when a binary interaction parameter and a mixed solvent solubility parameter were defined. Experiments show the solubility of AgNO_3 increases with the pressure at a certain temperature. However, the influence of temperature is related to a pressure defined as the turnover pressure(12.3 MPa). When the pressure is higher(or lower) than this turnover pressure, silver nitrate's solubility shows increasing(or decreasing) trend as the temperature rises. Satisfactory accuracy of our presented model was revealed by comparing experimental data with calculated results.

“Special Issue—Supercritical Fluids” Literatures on Dyeing Technique of Supercritical Fluid Carbon Dioxide

The supercritical fluid is used extensively, especially in substance extraction. The extraction of many substances has reached the economic-scale industrial bulk production stage. However, the research on the wastewater-free dyeing technique replacing water as dissolvent is still at a development stage. This study introduced the development situation of supercritical fluid dyeing technique, and described the evolution of stock dyeing, measurement of solubility of dye, studies of dyeing kinetics and instrument application studies, in order to provide related data for relevant studies in further development of this technique.

A four parameter cubic equation of state with temperature dependent covolume parameter

A four-parameter, Ghoderao–Dalvi–Narayan 2 cubic equation of state(GDN2 CEOS), is presented which incorporates the following: 1. The experimental value of the critical compressibility factor has been used as a fixed input parameter for calculations;2. All the parameters(a, b, c, d) of CEOS are temperature dependent functions in the subcritical region and are temperature independent functions in the supercritical region and;3. A new α function is introduced with two compound specific parameters which are estimated by matching saturated vapor pressure at two fixed temperature points Tr= 0.5, 0.7. Our formalism enables us to cast three of the four parameters of the CEOS as a function of the remaining parameter. The proposed CEOS is used to predict properties of 334 pure compounds, including saturated vapor pressure and liquid density, compressed liquid density, heat capacities at the constant pressure and volume, enthalpy of vaporization, sound velocity. To calculate thermodynamic properties of a pure compound, the present CEOS require the critical temperature, the critical pressure, the Pitzer’s acentric factor, the critical compressibility factor, and two parameters of the alpha function. The saturated liquid density predictions for pure fluids are very accurate when compared with GDN1(Ghoderao–Dalvi–Narayan 1),MPR(Modified Peng–Robinson), and PT(Patel–Teja) equations of state. Unlike MPR EOS, the proposed temperature dependent covolume parameter b in the present work satisfies all the constraints mentioned in the literature to avoid thermodynamic inconsistencies at the extreme temperature and pressure. Using van der Waals one-fluid mixing rule, the present CEOS is further used to predict bubble pressure and the vapor mole fraction of binary mixtures.

Overview of the Analytical Lifecycle of Supercritical Fluid Chromatography Methods

In recent times, the overall interest over Supercritical Fluid Chromatography (SFC) is truly growing within various domains but especially for pharmaceutical analysis. However, in the best of our knowledge modern SFC is not yet applied for drug quality control in the daily routine framework. Among the numerous reported SFC methods, none of them could be found to fully satisfy to all steps of the analytical method lifecycle. Thereby, the present contribution aims to provide an overview of the current and past achievements related to SFC techniques, with a targeted attention to this lifecycle and its successive steps. The included discussions were therefore structured accordingly and emphasizing the analytical method lifecycle in accord with the International Conference on Harmonisation (ICH). Recent and important scientific outputs in the field of analytical SFC, as well as instrumental evolution, qualification strategies, method development methodologies and discussions on the topic of method validation are reviewed.

不同参数高效超超临界机组经济性分析及建议

本文根据目前大量已投运二次再热机组运行经验,结合某660MW项目高效一次再热和二次再热不同的高效超超临界参数,结合对应的汽机热平衡图参数,通过对THA、80%THA、60%THA三个运行负荷进行了相关的机组经济性参数的计算和对比,通过分析提出了在选择一次再热或二次再热参数上的一些建议和结论。

超超临界循环流化床锅炉技术研发进展

随着技术进步和对节能减排需求的提升,更先进的超超临界循环流化床(circulating fluidized bed,CFB)锅炉技术成为行业发展趋势。该文探讨了超超临界CFB锅炉技术的设计理念,包括流态化燃烧、水动力系统、污染物控制及系统集成等关键技术。分析大尺寸炉膛内流态化燃烧的均匀性和燃尽性问题,探讨了不同炉型燃烧系统设计;研究超超临界压力下低质量流速垂直管圈水动力系统的设计方案;提出在大截面和高炉膛条件下污染物控制的设计思路;通过对锅炉燃烧技术、热力系统及辅助系统的耦合特性分析,指出燃烧侧与蒸汽侧系统设计的优化方向。基于对关键技术的深入研究和超临界CFB锅炉的实践经验,形成了多种超超临界CFB技术方案,多个采用不同技术方案的项目已进入到工程应用阶段,其中可靠、灵活、清洁和高效是设计中的关键考量。期望这些多样化的超超临界CFB技术路线能够在未来发展中展现出灵活性和低碳优势。

钛合金/钢钻杆复合钻柱动力学特性分析与优化设计

钻井深度的持续增加使钻柱面临的载荷工况越来越严苛。钛合金具有密度小、屈服强度高和弹性模量低等特点,基于井口钻杆抗拉余量设计要求,设计3种钛合金/钢钻杆复合钻柱,即复合钻柱1(Φ101.6 mm钻杆段全段使用钛合金钻杆)、复合钻柱2(Φ101.6 mm钻杆上半段使用钛合金钻杆)和复合钻柱3(Φ101.6 mm钻杆下半段使用钛合金钻杆)。为了探究钛合金/钢钻杆复合钻柱(简称为复合钻柱)的动力学特性,基于Hamiton原理建立复合钻柱的动力学模型,并采用节点迭代法和Newmark-β法对模型进行求解,分析3种复合钻柱的涡动特征、动态应力和振动特性,并与常规钢钻柱进行比较。结果表明:钛合金钻杆的使用可有效减缓钻柱涡动速度、动态应力,其中复合钻柱3的涡动速度、动态应力最小;基于振动特征强度对钻井作业参数进行优化,形成复合钻柱3的钻井作业参数推荐图版并给出合理的施工参数范围。

超深井钻柱动态疲劳失效特征及参数优选

随着油气勘探深度不断增大,超深井钻柱井下振动更加复杂,应力状态随时间变化显著,为保障超深井钻柱的安全性,开展了受空间挠曲井筒约束超细长钻柱的动态疲劳失效特征研究,并进行钻柱结构及工作参数优选。基于实际井眼轨迹,考虑钻柱与井壁的碰撞特征,通过有限元仿真分析,得到全井钻柱动力学特性;根据疲劳损伤累积理论,研究了超深井全井钻柱在非对称循环变幅应力状态下的疲劳强度;结合现场实例,研究了超深井钻柱的危险截面,分析了钻柱疲劳强度随转速、钻压和稳定器安装位置的变化规律。研究表明:钻压和高转速对钻柱疲劳强度的影响较大,低转速对钻柱疲劳强度的影响较小;稳定器可以大幅降低底部钻具组合疲劳失效的概率,而且稳定器安装位置对钻柱疲劳强度的影响较为显著。研究结果为超深井钻柱组合结构参数和钻井参数优选提供了理论依据。

非线性动态特性系数对汽轮机转子-轴承-密封系统运动特性的影响

为准确地反应汽流激振下汽轮机转子-轴承-密封系统的运动特性,推导了包含非线性动态特性(非线性刚度、阻尼)的转子运动微分方程,将数值模拟获得的非线性汽流激振力拟合成方程耦合到运动方程中,采用龙格-库塔法求解对应的运动方程,基于试验对比验证了考察非线性因素的必要性与运动微分方程的准确性。在此基础上,分析汽流激振力作用下不同非线性动态特性系数对转子运动特性与稳定性的影响。结果表明:系统中的非线性动态特性会改变转子不同类型的混沌运动区域与位移,使1/2、1/3、2/3工频的出现范围及幅值改变,密频现象增加;耦合热、动载荷后高负荷区域转子位移减小。对比Lyapunov指数,考虑非线性动态特性后其均值有所上升;合理的非线性刚度能够改善系统的稳定性,高非线性阻尼值能提高系统稳定性;耦合热、动载荷后的系统高负荷运行时更稳定。

塔东区块庆玉1井超深井优快钻井技术

随着油气勘探开发逐步从深层向超深层领域推进,塔东区块储层埋藏深,井下温度高、地质条件异常复杂,使得钻速慢、钻井周期长和钻井风险高。庆玉1井是大庆钻探工程公司在该区块钻的最深的井,为打好打成该井,开展施工难度因素分析,制定技术措施,应用高温仪器、工具、钻井液,施工参数优化等方法,研发超深井配套工艺技术,并结合现场施工要求,实现了塔东区块超深井庆玉1井的优快安全钻井。结果表明:该技术具有安全高效的优点,为深层、超深层油气的经济有效开发提供有效工程技术手段。

超高参数火箭煤油在小通道圆管内的流动换热特性

火箭煤油再生冷却过程具有高压、高温、高热流密度和高质量流速等特点。在超高参数条件下,采用低电压大电流电加热方法模拟火箭发动机推力室壁面热环境,在高温合金钢∅2 mm×0.5 mm圆管内研究了火箭煤油的流动换热特性。参数范围为压力25~65 MPa,质量流速8500~51000 kg/(m^(2)·s),流体温度常温为~500℃,热流密度最高为35 MW/m^(2)。研究表明:在所测试条件下,火箭煤油在小通道圆管内处于单相液态强制对流换热机制;换热性能主要受到流体温度和质量流速的影响;流体温度增加,换热系数增加;质量流速增加,换热系数增加;压力在25~65 MPa范围内对换热性能无显著影响;热流密度增加,内壁温显著增加,但热流密度变化对换热系数无显著影响;受入口强化换热效应的影响,换热系数增加,热流密度越高,入口效应越明显。超高参数尤其是超高压力条件下的火箭煤油换热特性,为火箭煤油再生冷却技术应用提供参考。

超超临界一次再热机组再热冷段材料选取研究

近几年,为缓解我国电力供需严峻形势,国家政策对火电态度出现转变,强调火电“压舱石”的作用,提出“三个8000万工程”后,火电机组建设规划进行了较大规模的调整,尤其是高参数大容量机组发展态势迅猛,对A6911-1/4CrCL22焊接钢管的需求量也逐年增加。受现国际国内形势影响,该材料管道价格飞涨,且供货周期长,不能满足国内超超临界一次再热机组项目建设需求,因此,再热冷段管道选择合适的材料替代A6911-1/4CrCL22对超超临界一次再热机组项目的建设有重要的推动作用。为此探讨了超超临界一次再热机组采用国产12Cr1MoVG无缝钢管替代A6911-1/4CrCL22焊接钢管的可行性。经过一系列比对,12Cr1MoVG无缝钢管替代A6911-1/4CrCL22焊接钢管在技术上可实现。

P92钢接头Ⅳ型开裂蠕变孔洞临界值的分析及应用

【目的】分析P92管道接头热影响区发生Ⅳ型开裂的蠕变孔洞临界值的影响因素,得到蠕变孔洞临界值计算方法,为评估接头开裂风险提供依据。【方法】收集服役后发生Ⅳ型开裂的P92接头,在未开裂处取样进行610℃下不同应力条件的高温持久蠕变试验,然后使用光学显微镜、电子显微镜观察服役开裂接头和持久断裂接头热影响区的蠕变孔洞分布形貌,并借助图像分析软件测量蠕变孔洞的面积分数,同时使用硬度仪测试热影响区软化情况,最后综合测试结果分析细晶区软化程度和接头应力水平对蠕变孔洞临界值的影响,并拟合应力、显微硬度、孔洞临界值三者之间的函数关系。【结果】研究发现,P92钢接头细晶区相比于接头其它区域软化速度更快,但软化作用并非其发生Ⅳ型开裂的必要条件,当应力水平较高时,细晶区没有发生明显软化时就可以触发蠕变开裂;得到接头轴向应力水平、蠕变孔洞面积分数临界值和显微硬度的函数关系式。【结论】引起Ⅳ型开裂的蠕变孔洞面积分数临界值与相对应力水平(轴向应力与硬度的比值)有关,相对应力水平越高,蠕变孔洞临界值越小,接头安全性就越低;通过测量接头细晶热影响区的蠕变孔洞面积分数和显微硬度,可以估算开裂接头的轴向应力水平,也可以评估在役未开裂接头的Ⅳ型开裂风险。

4 m/s超高速电梯系统的主参数配置与计算

随着城市建筑高层化进程的加速,带动了超高速电梯的迅速发展。针对国内超高速电梯研发滞后的现状,以4 m/s超高速电梯为设计对象,合理选择电梯驱动主机,配置电梯主要参数,对电梯系统的主机功率、速度、主轴负荷、曳引条件、钢丝绳安全系数、导轨强度等关键参数进行计算分析。结果表明,4 m/s超高速电梯主要参数配置合理,满足设计要求,为国内超高速电梯研究提供了理论计算参考依据。