大斜度井旋转钻柱横向振动规律比例实验研究

针对振动引起的钻柱磨损与失效等问题,利用钻柱动力学实验装置测量了大斜度旋转钻柱的横向振动情况,通过快速傅里叶变换对振动频率进行了分析,并根据钻柱振动位移数据计算了振动加速度,定量研究了不同转速和钻压下的横向振动规律。实验结果表明:低转速时横向振动频率等于激振频率;高转速条件下观察到钻柱"次生摆动",同一运动周期内钻柱摆动次数增加,该现象导致钻柱横向振动频率加倍,横向振动加速度上升;随着钻压的增大,钻柱摆动平均加速度保持稳定,但钻柱横向振动频率减小,无因次频率从2降为1,表明高钻压对高转速下产生的次生摆动起抑制作用。     

钻柱振动信号的在线监测及应用

钻柱振动信号是一种非常复杂的振动波,它包含了钻柱和钻头自身工况引起的振动、钻头与地层相互作用所激发的振动,钻柱与井壁相互碰撞和粘卡-释放引起的振动等。研究表明,井下钻柱的运动状态、牙轮钻头的磨损状况和岩石的破碎方式的不同,会表现出不同的振动特征。因此,在线监测和分析钻柱振动信号的时域和频域特征,实时识别井下钻具的工作状态,对预防钻具（钻柱和钻头）的早期损坏、减少钻井事故的发生具有重要作用。在调研国内外钻柱振动信号测量方法的基础上,研制了钻柱三轴振动信号的地面测量装置,并进行了现场试验。试验结果表明,通过对振动信号的时域和频域信号的特征分析,对可以识别出钻柱的非稳定工作状态、钻柱粘卡、钻头故障等异常工况,并且通过改变钻压或转盘转速可以消除因钻进参数配合不当二引发的高幅振动,防止钻具的早期损坏。     

钻柱纵向振动分析与应用

利用钻柱纵向振动数学模型,分析了钻柱轴向应力振幅分布曲线和钻柱中最大轴向应力幅频曲线的特征以及钻井液粘度、激励位移、减振器位置对钻杆中最大轴向应力振幅的影响。分析表明：钻柱中轴向应力振幅沿纵向呈波状分布,其最大值在钻柱底部或钻杆中;钻杆中的最大轴向应力振幅随转速的变化曲线呈凹坑形,为了保护钻柱,应该选择凹坑中间的转速带;钻杆中的最大轴向应力振幅和钻柱底部的轴向应力振幅随转速的变化趋势并不完全一致,以后者作为判断钻柱是否共振和优选转速的指标不够准确,而应以前者作为该指标;钻杆中的最大轴向应力振幅与激励位移大致成正比;钻井液粘度越高,钻杆中的最大轴向应力振幅越小;减振器位置可以改变钻柱纵振系统的固有频率,从保护钻柱角度考虑,低转速时,减振器应紧靠钻头安装,高转速时,减振器应与钻头保持一定距离;通过优选钻具组合和转速,防止钻柱共振是预防钻具失效的有效措施     

基于能量的弹塑性损伤实用本构模型

建立一个实用的弹塑性损伤本构模型。在有效应力空间采用经验公式计算塑性变形,能将模型塑性部分与损伤部分解耦,降低模型的数值处理复杂性,同时大大简化模型塑性应变的计算。结合不可逆热力学理论,基于损伤能量释放率建立损伤准则,损伤能量释放率由修正后的弹性Helmholtz自由能导出,模型中将弹性Helmholtz自由能分解为应力球量部分和应力偏量部分,将其应力球量部分产生的损伤取为零,同时根据应力状态引入折减系数对其应力偏量部分进行修正,使得模型能较为准确的模拟混凝土材料在双轴加载下的本构行为。将应力张量谱分解为正、负两部分以分别定义材料受拉、受压损伤演化,并采用受拉损伤变量、受压损伤变量分别模拟混凝土材料在拉、压加载下的本构特性。引入一个加权损伤变量使得模型能较准确的反映混凝土材料的“拉-压软化效应”。最后该文给出初步试验验证,证明了该文模型的有效性。     

牙轮钻头单牙轮的破岩仿真研究

牙轮钻头在井底破碎岩石过程中受顶部钻压、自身动载荷以及井底接触岩石的随机冲击碰撞作用,存在牙齿与岩石交替压入、刮切和滚动的运动状态,受力情况相当复杂。基于岩石弹塑性本构关系和等效塑性应变的岩石破坏准则,考虑井底围压以及钻头与岩石互作用随机接触碰撞,采用有限单元法建立了牙轮钻头与井底岩石互作用下系统非线性动力学模型。探讨了牙轮钻头在破碎井底岩石过程中的运动规律及力学性能,对岩石破碎坑的形成过程进行了仿真,为有效预测和控制井眼轨迹的形成,实态工况下整体钻柱系统耦合非线性动力学研究提供了理论依据。     

一种新型流体附壁自激式水力振荡器及其射流振荡特性EI北大核心CSCD

为了降低钻进过程钻柱与井壁间的摩阻,有效改善托压、卡钻现象及提高有效钻压,设计了一种流体附壁自激式水力振荡器,其可使钻柱发生周期性轴向振动,改变钻柱与井壁间的摩擦形式,提高作业效率。通过理论分析和数值模拟方法阐述了装置原理,利用理论力学分析和Matlab编程方法建立轴向振动工况下管柱摩擦力数学模型;采用有限元数值模拟方法对振荡器进行参数敏感性分析,利用全尺寸物模试验对不同排量下装置的振动特性进行实测分析,并在连续油管加深钻进工程应用中验证了装置的振动减阻效果。结果表明:进出口比对装置入口压力的变化较为敏感,振荡腔腔长和排量对装置入口压力及频率均较为敏感;进出口比和排量的变化对减阻效率影响明显,进出口比与减阻效率呈负相关,排量与减阻效率呈正相关;装置入口压力极值、幅值随排量增大呈增长趋势,装置轴向振动位移幅度与泵注排量呈正相关;该装置可使连续油管钻井进尺速度提高128.6%,提速效果明显。研究结果可为流体附壁自激式水力振荡器的工业化应用提供依据。     

垂直井中受压段旋转钻柱的分岔研究

主要目的是研究钻柱的转动效应对铅垂井段钻柱屈曲行为的影响。通过考虑垂直井中受压段钻柱在旋转时引起的惯性力,建立了在分布浮重作用下旋转钻柱的分岔微分方程。通过对方程的数值求解,得到了旋转钻柱发生屈曲时的前四阶分岔值曲线及相应的屈曲构形。计算结果表明,随着钻柱转速的提高,发生各阶屈曲的临界钻压将明显降低。通过对工程实例的分析得知,转动效应对受压段钻柱的屈曲行为有不可忽视的影响。     

主动围压下岩石的冲击力学性能试验研究

利用具有主动围压加载装置的直径为100 mm分离式Hopkinson压杆（SHPB）试验装置和薄圆形紫铜片作为波形整形器,研究了斜长角闪岩在不同围压等级（0~6 MPa）、不同应变速率（50~170 s-1）下的动态力学性能,并对试验有效性进行了分析。试验结果表明：斜长角闪岩的动态强度增长因子与应变率的对数呈近似线性关系,强度与比能量吸收随应变率的增加而近似线性增加,体现了显著的应变率相关性;在同等级应变率范围内,随着围压的增加,岩石的增强效果与增韧效果逐渐增强;同时发现,在围压作用下,岩石的破坏由拉伸破坏向压剪破坏逐渐过渡和发展。SHPB试验中,近似恒应变率加载时间比例约为69.5 %,能够较好地满足应力均匀分布及近似恒应变率加载要求,表明SHPB试验的有效性和结果的可靠性     

斜直井眼中钻柱横向动态运动非线性模型研究

由于缺乏对钻柱在斜井或水平井中运动规律清楚的认识,故无法采取有效措施避免钻柱的非正常磨损以及由于钻柱偏磨导致的钻杆磨穿问题。基于Lagrange动力学普遍方程,综合考虑了钻柱的黏滑运动、横向及扭转变形以及钻井液阻尼的影响,建立了斜直井中钻柱非规则运动的4自由度非线性动态模型。针对不同井斜角条件下钻柱运动的数值研究表明:当井斜角为90°时,钻柱将会沿着自身旋转方向约30°扇形域的井壁蠕动,并且由于摩阻扭矩的集聚-释放,伴随随机的黏滑和翻滚。随着井斜角的减小,局部的摩擦翻滚幅度增加并逐渐扩展成为整个井眼内的带有随机碰撞的回旋运动。该模型有助于更好地认识定向井作业中钻柱的井下工况,为有效实施减弱钻柱磨损和预防钻杆磨穿的举措提供理论指导。     

φ139.7 mm×10.54 mm G105钻杆刺穿失效分析

采用宏观分析、化学成分分析、力学性能试验、金相检验、扫描电镜断口分析及能谱分析等手段对某规格为φ139.7 mm×10.54 mm的G105钻杆的刺穿原因进行了分析。结果表明:钻杆刺穿的实质是早期疲劳失效;蹩钻、跳钻等钻柱振动引起钻杆上产生的严重交变应力是导致钻杆失效的主要原因;钻井液中的溶解氧对钻杆外表面造成氧腐蚀并形成腐蚀坑,促进了疲劳裂纹的萌生;钻铤直接过渡到钻杆,截面变化突然,使应力集中加剧,也是导致钻杆发生疲劳失效的原因之一。建议在钻井液中添加除氧剂和缓蚀剂,并适当降低钻压,调整钻井参数,避免钻柱剧烈振动。     

不同激振条件下减振器对钻柱纵向振动的影响

利用钻柱纵向振动数学模型,在钻头处分别施加激励位移(即激励位移法)和激励力(即激励力法),对比分析了减振器刚度和安装位置对常用塔式钻柱钻杆中晟大轴向应力振幅和井口钻柱轴向位移振幅的影响.分析发现:二者随转速的变化曲线呈连续的凹坑形,钻井时应优选转速使二者尽可能小;减振器的安装位置和刚度对二者有重要影响,当钻头处采用不同...     

受压旋转钻柱非线性动力学与分叉研究

在水平井钻井过程中,钻柱由于受压很容易发生横向振动,引发钻柱失效、井眼扩径等严重事故。该文将受压柔性旋转钻柱简化为柔性旋转梁,将钻柱受到的复杂载荷简化到柔性旋转梁系统中,基于vonKarman理论建立了柔性钻柱的动力学方程,再利用Galerkin法离散偏微分方程,得到了钻柱的非线性控制方程,并且利用多尺度法得到了平均方程。运用非线性动力学的方法分析柔性旋转梁在共振情况下的复杂动力学响应,得出系统中钻柱旋转角速度对非线性动力学响应的变化规律。研究结果可为水平井钻井过程中减少钻柱失效、提高钻速和降低钻井成本提供参考。     

Stability of drill strings in controlled directional wells

We formulate the problem of theoretical simulation of the bifurcation buckling of drill strings in deep directional and horizontal oil and gas wells, and propose the procedure for its solution. The analysis is made of the critical states in drill strings for various values of the well inclination, axial velocities of drill string motion and rotation. The buckling modes of the bifurcation drilling are constructed. Translated from Problemy Prochnosti, No. 6, pp. 71–81, November–December, 2008.     

牙轮钻头纵向横向扭转振动动力学仿真研究

随着石油资源钻探难度的不断加大，有效地预测和控制井下钻头的运动规律，改善钻柱动力学性能，以提高钻头和钻柱的强度，实现对井眼轨迹的精确控制是目前钻井工业中亟待解决的关键技术难题。本文根据牙轮钻头的实际振动状态，分析了钻头产生各种振动的机理，讨论了钻头-岩石互作用力学模型，用能量法建立了考虑牙轮钻头纵向、横向和扭转振动耦合非线性系统动力学分析模型，编制了系统动力学仿真程序，并结合实例对牙轮钻头系统进行了动态仿真。     

Influence of adsorption kinetics on chemomechanically enhanced hard rock drilling

To enhance the efficiency of diamond bit drilling into hard rocks by means of chemomechanically active additives, several not-so-obvious factors must be taken into account. These include polarity and concentration of surfactant, mode of diamond failure and rate of adsorption of the active species onto the rock under the bit. To evaluate the latter factor, Westerly granite was drilled with diamond bits ranging in size from 0.6 to 6 cm at rotational speeds ranging from 50 to 5000 rpm using aqueous concentrations of Aerosol C-61, a cationic surfactant, ranging from 10^–4 to 10^–2moll^–1. The results reveal that rotational speed has a strong effect on the additive-enhanced diamond life, with maxima appearing under conditions suggesting that, for higher bit speeds, the isoelectric point of the rock effectively occurs at surfactant concentrations greater than those determined under static conditions. The results also demonstrate the possibility of utilizing laboratory-scale drilling tests to inexpensively simulate field-scale tests of potentially useful, bit wear-reducing surfactants.     

Role of base plate rotational speed in controlling spheroid size distribution and minimizing oversize particle formation during spheroid production by rotary processing

The occurrence of material adhesion and formation of oversize particles in the product yield during one-pot spheroid production by rotary processing leads to a less predictable process and a decrease in the usable portion of the total product yield obtained from each production run. The use of variable speeds of the rotating frictional base plate during the spheronization run was investigated for achieving optimal spheroid production. When the base plate speed was increased during liquid addition, the greater centrifugal forces generated improved liquid distribution and the mixing of the moist powder mass, resulting in a decrease in the amount of oversize particles formed. When the base plate was maintained at a high speed throughout the run, the amount of oversize particles and mean spheroid size increased, and a greater “between batch” mean spheroid size variability was also observed. The findings showed that, when higher speeds were used, the residence time must be adjusted accordingly to avoid excessive coalescence and growth while maintaining even liquid distribution. A “low-high-low” speed variation during rotary processing may be used to produce spheroids with a narrow size distribution and with a minimal amount of oversize particles in the total product yield.     

岩屑床破坏器在水平井斜井段的清洁效果研究

针对水平井斜井段岩屑堆积成床易造成钻柱摩阻、扭矩增大及卡钻等问题，对斜井段中岩屑床破坏器的影响规律和清洁效果进行评估分析。首先，基于CFD （computational fluid dynamics，计算流体动力学）技术，对岩屑床破坏器的清洁机理进行研究，并通过对比分析得到岩屑床破坏器的清洁效果。然后，分析了不同井斜角、钻井液排量和钻柱转速下岩屑床破坏器对水平井斜井段岩屑床的影响规律，并对岩屑床破坏器的工况参数进行优选，以更好地发挥其清洁作用。最后，通过岩屑床破坏器的现场应用来验证其清洁效果。结果表明，岩屑床破坏器对水平井斜井段井眼的清洁效果非常明显，使用后可减小钻柱的摩阻和扭矩，有效防止钻进过程中卡钻事故的发生。研究结果可为岩屑床破坏器的使用提供指导。     

Research on Buckling Behavior and Analysis of Sensitive Factors in Horizontal Well Drilling

Buckling behavior of the drill string in the wellbore is one of the key issues in the oil and gas well engineering, which has been investigated by many theoretical and experimental studies in recent years. In order to study the buckling characteristics of drill string in the horizontal well, the factors of gravity, friction, and boundary conditions were taken into account, and a numerical simulation model of horizontal drill string was built up. The buckling critical load of numerical simulation was proven to be in good agreement with the experimental results; that is to say the simulation result is reliable. The key factors of friction coefficient, length of horizontal well section, and radial clearance between drill string and wellbore annular which affect buckling critical load of drill string were discussed. The results show that the angular displacement of horizontal drill string changes in the form of sine when sinusoidal buckling occurs. The pipe string buckling critical load increases with the increasing of friction coefficient. Under the same condition, the buckling critical load of horizontal drill string decreases approximately linear with the raise of horizontal well length, and declines in exponential trend with the increasing of the annular clearance. The research can provide theoretical reference for the optimal design of horizontal well string and practical drilling operation.     

Dynamic analysis and nonlinear simulation of aircraft flat spin

Abstract

In this paper we investigate the dynamic characteristics of flat spin of a fighter aircraft in open-loop configuration. The aircraft model under study is of the multi-role fighter configuration co-sponsored by China and Pakistan. The aerodynamic model used in the study is in the form of look-up tables that have been developed from rotary balance steady coning and oscillatory coning motion wind tunnel data. The set of all possible equilibrium spin states is numerically computed for various values of control settings using eighth-order aircraft equations of motion. Results from dynamical systems theory are applied to investigate local stability characteristics of aircraft around steady spin state. The complete set of dynamic modes of aircraft in spin is evaluated and mode content in each of the motion variable is determined using modal decomposition. This analytical technique is complemented by performing numerical simulations to investigate flat spin dynamic features. The methodology is applied to investigate dynamic behavior of two flat spins: right flat spin at 72.1° and much flatter left spin at 84.4°. The presented work provides insight into the global overview of aircraft flat spins as a function of various control settings, and their dynamic characteristics and it can facilitate the designing of flight control laws for spin recovery/prevention.