井底牙轮钻头的钻速方程及现场应用

以岩石侵入理论为基础,在考虑井底压力的条件下,建立牙轮钻头的钻速模型。结果表明:在地层由软、中硬到硬地层过渡过程中,钻速方程能够解释不同破岩方式下牙轮钻头的机械钻速问题;随着刃尖角的增大,锥形齿和楔形齿的牙齿侵深都呈指数递减趋势;随着井眼内钻井液柱压力的增大,侵入深度呈指数递减趋势,其中锥形齿递减趋势大于楔形齿;模型理论钻速计算结果与实际钻速数据接近,最小欧式距离为25.8。     

基于旋转侵入理论的牙轮钻头钻速模型

 针对旋转钻井牙轮钻头对井底岩石垂向压入和水平刮切联合作用的特点, 基于牙轮钻头旋转侵入理论, 建立了机械钻速预测模型, 并通过室内实验确定了楔形齿纯滚动多齿联合作用对破岩效果的综合影响系数, 机械钻速预测平均误差为4.1%。研究认为, 考虑钻头旋转引起的水平刮切力时, 侵入深度比只考虑垂向压入时有所增加;摩擦系数和刃尖角较小时两者相差不大, 随着摩擦系数和刃尖角的增大, 两者的相对差值越来越大, 摩擦系数和刃尖角较大时钻头旋转引起的水平刮切作用对机械钻速的影响不容忽视。     

冲击诱导损伤岩石的切削特性

为了提高硬岩矿山开采时牙轮切削钻孔效率,降低钻具磨损,提出冲击诱导切削复合破岩新方法。在Walsh模型的基础上,建立冲击诱导孔周围岩石损伤区的裂纹模型,推导岩石损伤区的牙轮钻齿侵入系数方程及牙轮钻速方程,分析裂纹密度和扰动频率分别对岩石弹性模量、钻齿侵入系数和钻齿切削力的影响。研究结果表明:随着裂纹密度增大,岩石的有效弹性模量减小,侵入系数逐渐减小;在一定内摩擦角范围内,随着裂纹密度增大,牙轮钻速显著提高;在相同轴向载荷条件下,随着冲击扰动频率增大,牙轮钻齿切削力逐渐减小。     

大尺寸牙轮钻头结构设计问题的分析

针对深井上部大直径井段中牙轮钻头机械钻速低的问题，从设计角度对目前大尺寸牙轮钻头的齿面结构和水力结构进行了分析和讨论。与Φ２１５．９ｍｍ钻头相比，在相同地层条件下，Φ４４４．５ｍｍ钻头牙齿与井底岩石的最大接触应力低１８％～２８％，相同齿圈上的齿顶间距增大７０％～８０％，井底面积覆盖率减小了近５０％，平均单齿破岩量增加了１．７４倍，因而在硬地层和砾石层中破岩效率要低。在相同机泵条件下，Φ４４４．５ｍｍ钻头的井底比水功率远低于Φ２１５．９ｍｍ钻头，井底和钻头清洗状况不良，影响了机械钻速。因此，应根据大尺寸牙轮钻头的具体情况，对齿面结构和水力结构进行改造，以提高钻头的破岩效率和清洗效率。同时应增加钻头类型，完善钻头系列。     

欠平衡井底附近岩石应力状态分析

由于欠平衡钻井具有大幅度提高钻速、有效保护油气层和降低钻井成本等优点,被广泛应用于国内外各大油田,但对欠平衡钻井井底岩石应力状态特点的相关研究较少。本文以欠平衡钻井井底附近井眼为研究对象,通过分析地应力、孔隙压力、液柱压力等对井底岩石机械力学特征变化的影响,来研究欠平衡条件下非渗透性井壁和渗透性井壁岩石的破碎效率、井斜、井壁稳定等问题。研究结果表明：井底附近岩石力学性质受地应力、孔隙压力、井眼及液柱压力等的综合作用。非渗透岩石时,欠平衡钻井破岩效率高,机械钻速大,井壁集中力大,易井斜;渗透井壁时,随渗透率的增大,欠平衡钻井破岩效率降低,机械钻速减小,井壁集中力减小,井斜倾向变小。     

冲击诱导损伤岩石的侵入特性

在硬岩矿山开采中,为了提高大孔径深孔凿岩效率,降低钻具磨损,提出了冲击诱导切削复合凿岩新工艺.在Walsh模型的基础上,建立了冲击诱导孔周围损伤岩石的裂纹模型,推导了岩石损伤区的牙轮钻齿侵入系数方程及侵入阻力方程.分析了裂纹密度、扰动频率分别对岩石弹性模量、岩石破碎体积和钻齿侵入阻力的影响.结果表明:随裂纹密度的增大,岩石的有效弹性模量减小;相同侵入载荷下,随着扰动频率的增加,钻齿的侵深和岩石破碎体积不断增加;随着冲击扰动频率的增大,牙轮钻齿侵入阻力逐渐减小.     

三牙轮钻头的计算机仿真模型

本文将牙轮钻头上各牙齿置于易于描述的坐标系下．通过坐标变换方法,实现了各牙齿的空间位置交换．在钻头几何学和运动学的基础上,建立了随钻运动的牙轮钻头的计算机仿真模型。该仿真模型可真实反映牙轮钻头钻进过程中牙轮上各牙齿的形状、大小,钻头上各牙齿的布置及钻头钻进过程中各牙齿间的相互位置关系。该项研究不但是钻头与岩石互作用仿真研究的核心问题之一,也是分析研究牙轮钻头工作行为的基础。     

空气冲旋钻井机械钻速仿真算法

钻井机械钻速预测是难题.以前,研究者们常根据现场数据或试验数据,用统计拟合分析方法得出机械钻速的经验或半经验关系式.这些经验或半经验公式包括一些很难确定的系数准确性和可靠性差.为此,作者结合三牙轮钻头有关的理论,建立了空气冲旋钻井钻头的真实数学模型、真实井底模型和钻头牙齿与井底岩石互作用模型,用计算机仿真方法预测出了空气冲旋钻井机械钻速.使用表明,该模型可靠,计算结果与实际机械钻速基本一致,研究成果可用于冲旋钻头改进、优化设计和钻井参数优选.     

牙轮钻头牙齿破岩有限元分析

牙轮钻头是石油钻井中主要的破岩工具。牙轮钻头的破岩是通过其齿圈上的牙齿和岩石相互作用完成的。本文通过建立牙轮钻头单个牙齿与岩石互作用模型,用有限元方法完成了牙轮钻头破岩过程的分析,获得岩石的破碎坑;进一步通过等效应力云图确定了牙齿破岩过程牙齿及岩石的应力分布情况,为进一步分析牙轮钻头破岩效率提供依据。     

混合钻头对软硬交错地层破岩特性的仿真研究

为了研究PDC-牙轮混合钻头的破岩过程及其钻进软硬交错地层时的工作特性,根据Drucker-Prager准则构建软硬交错岩石模型,并对混合钻头和传统PDC钻头进行钻进仿真对比分析。结果表明:钻进过程中距井眼轴心约2/3井眼半径部位的岩石所受应力较大;在软硬交错地层中,混合钻头比PDC钻头的机械钻速高28.8%、钻速波动值低27.0%、径向载荷峰值低27.6%。混合钻头利用PDC切削齿与牙轮切削齿进行协同破岩,相比PDC钻头能够更加快速、稳定地钻进软硬交错地层。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with