含水合物相变的油气井多相流动模型及应用研究

深水钻井、测试过程中,井筒/管柱中易生成天然气水合物。该文研究了含水合物相变的井筒多相流动特征,建立了含水合物相变的井筒多相流动模型,提出了水合物生成区域的定量预测方法,研究了水合物生成与沉积特征,得到了水合物堵塞形成机制。水合物生成导致井筒环空内气体体积分数减小,使得气侵早期具有"隐蔽性";而水合物在井口附近分解会造成气体体积分数迅速增大,使得气侵后期具有"突发性",导致侵入气体处理难度大,井筒压力控制困难。应用该文建立的模型,可以定量预测深水气井测试作业中易发生水合物堵塞的高风险区。研究提出通过注入低浓度的抑制剂,延缓水合物堵塞的发生,可以有效克服传统防治方法过度使用抑制剂的不足。该文的工作可为水合物堵塞预测和防治工作提供参考。     

深水气井测试天然气水合物生成区域预测及分析

在深水气井测试过程中,整个流动范围内(井筒与地面流动管线)天然气水合物生成区域准确预测是测试流动保障的关键前提。深水特殊环境及气体低密度等因素导致深水气井测试时极易达到水合物生成条件:低温、高压等,尤其在泥线附近、地面节流管线处及低产气速率及地面关井等测试工况下。为此,该文针对测试中所有工况(清井、变产量流动、井下及地面关井等),以整个流动范围内温压场及水合物相平衡条件计算为基础,建立了水合物生成区域预测方法;温度计算模型以焓为研究对象,增加了温度预测准确度;计算将井筒与地面管线整合,得到整个流动范围内水合物生成判断图版。并以中国南海一口井为例,分析得到了产量、天然气组分和节流等因素对水合物生成区域的影响规律,评价了甲醇、乙二醇等热力学抑制剂的抑制效果,可提供指导。     

基于格网DEM的等高线提取误差传播模型

从格网DEM的结构入手,根据误差传播定律,分析了格网点的高程误差对由其生成的等高线数据的位置偏移、长度及方向的影响,建立误差传播模型,以实际DEM为例对比了原始等高线和DEM内插产生的等高线的变化,并进行了模型验证。结果表明:等高点落在格网点时中误差最大,越接近中点,中误差越小;等高线折线的长度中误差是线元长度中误差的累计,其值随内插点的增多而增大;等高线折线的方向中误差与折线的起点和终点位置相关,与等高线的追踪路径无关。     

基于Hydrus-2D的果树涌泉灌溉环沟技术要素优化研究

为探寻涌泉灌条件下,土壤水分运移规律与环沟内径、入沟流量、灌水量及土质的关系,确定果树涌泉灌的最优环沟参数.本研究利用Hydrus-2D/3D软件对果树涌泉灌进行建模,再利用模型对不同环沟内径、入沟流量、灌水量及土质组合下的240种情形进行数值模拟,分析探究了各种要素对土壤水分运移及湿润体分布的影响.结果表明,环沟内径增大,湿润体范围减小,高含水量区增大,湿润体形状逐渐趋于椭圆形;入沟流量增大,湿润体范围减小,高含水量区增大;同一灌水量下,土壤渗透性越强,保水性越弱,湿润体越大,高含水量区越小.各种情形下最优环沟内径为20cm,而入沟流量则需要根据灌水量和环沟内径做出相应调整.     

饮用水供水管道的腐蚀监测分析

为了评估保护的有效性,并控制抑制剂的最佳用量,本研究使用腐蚀自动监测系统,并通过测量水的物理、化学性质来评估水的腐蚀性。结果表明,聚磷酸钙作为一种无毒抑制剂,防腐效果较好。管网中注入抑制剂会大大降低进水口的腐蚀风险,且在管网较远位置仍可降低腐蚀速率。在夏季,当水的腐蚀性最强时,抑制剂的保护作用发挥到最大。研究结果对保护供水管道系统和供水水质具有实际的指导意义。     

基于IDA分析的深水高墩连续刚构桥地震损伤评价

为研究深水高墩连续刚构桥的地震易损位置及损伤程度,以某库区深水高墩连续刚构桥为对象,采用塑性铰模型,考虑地震动水效应,建立结构非线性有限元模型。采用频数分析法,选取50条典型强震记录为输入,基于IDA分析,从地震易损性分析的角度去评价深水高墩连续刚构梁桥的抗震性能,对比分析了高水位与无水情况下桥墩和支座的整体易损性曲线、桥墩墩身易损位置及其对应的损伤概率分布情况。结果显示:考虑水体时,桥梁构件损伤概率会显著增大,桥梁主墩的易损位置由墩底附近向墩身上部位置移动;支座处的损伤概率在各相应损伤等级中比桥墩高,且相比于主墩,边墩更容易发生损伤;边墩损伤位置主要集中于墩底附近,而主墩损伤位置位于墩底附近及墩身上部。结果表明,抗震设计时,需重点关注以上边主墩易损伤位置的受力及支座位移情况。     

口环间隙泄漏对离心泵空化性能的影响分析

以DG-350型多级离心泵次级叶轮为研究对象,研究了口环间隙对离心泵空化性能产生的影响。通过定常数值模拟,计算出了离心泵的扬程和效率,同时得出了口环与进口段交汇处的速度矢量图、涡量云图和空化区域分布图以及叶轮流道内的空化区域分布图。模拟结果与实验结果的对比分析表明:(1)误差都在实际工程所要求的5%左右,说明计算与模拟结果准确;(2)由于口环与进口段交汇处速度旋涡的存在,使得离心泵的进口段与前口环交汇处区域的压力降低,从而导致了空化现象的发生;(3)随着口环间隙的增大叶轮流道上的空化区域也随之增大,从而减小了流体的过流面积,使流体速度和必须的汽蚀余量增大,NPSHR增大,则叶轮进口处的空化区域也就会增大。     

基于三元方法的轴流泵设计

为了快速、高效地设计性能优越的轴流泵,结合计算流体力学方法和基于环量的三元设计方法,研究了叶轮环量中心位置、叶轮出口边环量斜率以及导叶进口边环量与叶轮出口边环量比值对轴流泵性能的影响,并设计了一型水力效率超过90%的轴流泵。研究表明:叶轮环量中心从0.3倍叶片弦长移动到0.7倍弦长,叶轮效率降低了1%,但是叶片低压区面积大幅减小;叶轮出口边叶顶环量与叶根环量的比值K从0.9增大到1.1,叶轮效率逐渐提高;导叶进口边环量与叶轮出口边环量比值R从0.9增大到1.1,轴流泵效率逐渐降低。     

固化疏浚泥室内渗透试验研究

为了研究固化疏浚泥的渗透特性,对不同养护条件、固化剂掺入量和龄期的固化疏浚泥进行了室内变水头渗透试验研究。结果表明:在养护条件一定时,固化疏浚泥的渗透系数随着固化剂掺入量和龄期的增大而减小;可用于工程防渗的最佳固化剂掺入量为6%~8%,而在固化剂中添加10%粉煤灰后的最佳固化剂掺入量为5%。试验结果对工程设计和施工具有重要的工程应用参考价值。     

给水处理中产生污泥膨胀的原因及解决办法

给水处理过程中有时也会出现“污泥膨胀” ,而影响水处理工艺的正常运行 ,严重时甚至会造成系统停产。就其所产生的原因进行探讨 ,并提出了增大排泥量 ,及时排泥 ,避免循环泥水重复加药 ,改善絮凝沉淀条件等解决办法和预防措施。     

Prediction of natural gas hydrate formation region in wellbore during deep water gas well testing

Wellbore temperature field equations are established with considerations of the enthalpy changes of the natural gas during the deep-water gas well testing. A prediction method for the natural gas hydrate formation region during the deep-water gas well testing is proposed, which combines the wellbore temperature field equations, the phase equilibrium conditions of the natural gas hydrate formation and the calculation methods for the pressure field. Through the sensitivity analysis of the parameters that affect the hydrate formation region, it can be concluded that during the deep-water gas well testing, with the reduction of the gas production rate and the decrease of the geothermal gradient, along with the increase of the depth of water, the hydrate formation region in the wellbore enlarges, the hydrate formation regions differ with different component contents of natural gases, as compared with the pure methane gas, with the increase of ethane and propane, the hydrate formation region expands, the admixture of inhibitors, the type and the concentrations of which can be optimized through the method proposed in the paper, will reduce the hydrate formation region, the throttling effect will lead to the abrupt changes of temperature and pressure, which results in a variation of the hydrate formation region, if the throttling occurs in the shallow part of the wellbore, the temperature will drop too much, which enlarges the hydrate formation region, otherwise, if the throttling occurs in the deep part of the wellbore, the hydrate formation region will be reduced due to the decrease of the pressure.     

Deepwater gas kick simulation with consideration of the gas hydrate phase transition简

The hydrate phase transition presents new problems and challenges for the deepwater well control in the drilling processes. A simulation model is built for deepwater gas kicks with consideration of the hydrate phase transition. The model is based on the multiphase flow governing equations and the hydrate phase transition calculation equations. The influence of the hydrate phase tran-sition on the gas kick hydraulics is investigated through numerical simulations. It is shown that the diameter of the gas bubbles can significantly influence the hydrate phase transition effect. The influence of the hydrate phase transition on the gas kick hydraulics in-creases with the decrease of the average gas bubble diameter. The hydrate phase transition adds a＂hidden＂nature for the well kick in deepwater and hinders the early detection of the gas kick. The influence of the hydrate phase transition on the gas kick hydraulics is also studied in the case when the hydrate inhibitor is added to the drilling fluid.     

深海能源土抗剪强度的理论研究

水合物的存在和分解对能源土的抗剪强度有双面影响。为了研究水合物对于海洋土抗剪强度的影响,考虑到水合物的存在增大了土颗粒之间的接触面积,引入胶结面积比的概念,采用理论推导的方法,修正了考虑水合物影响的有效应力表达式,并提出能够同时考虑水合物种类以及赋存模式的黏聚力表达式。根据摩尔-库伦准则,得到抗剪强度随着水合物饱和度变化的关系式。此外,考虑甲烷气体的溶解,修正了水合物分解后的孔隙压力表达式。最后,借助于沉积物三轴剪切试验和水合物分解的数值模拟结果来验证公式的合理性。结果表明:所提公式能较好地反映水合物含量、水合物赋存状态、高水压对强度的影响;同时修正孔压模型有助于更好地分析海底斜坡稳定。     

A NUMERICAL PRESSURE TRANSIENT MODEL FOR MULTILAYERED GAS RESERVOIRS WITH PSEUDOSTEADY STATE FORMATION CROSSFLOW

ＮＯＭＥＮＣＬＡＴＵＲＥＡＤｊ=Ａｊ·ｒ2 ｗ(ｋｈ) ｔＣＤｅ =ＴＶｗ2πＴｗｒｗ2 (ｈ) ｔｒＤ =ｒｒｗｐＤｊ=2π(ｋｈ) ｔＴｓｃｐｓｃｑｓｃＴ (Ｐμｚ) ｊ(φ0 - φｊ)ＴａＤ =(ｋｈ) ｔｔａ(ｈ) ｔ(μＣｇ) 0 ｒｗ2ｑＤｊ=ｑｊｑＷＤｊ=(ｋｈ) ｊ(ｋｈ) ｔωｊ=(     

MATHEMATICAL AND COMPUTER SIMULATION TECHNOLOGY OF CONDENSATE OIL AND GAS WELLS STIMULATED BY ELECTROMAGNETIC HEATING

In this article, the recent research achievements on the theory and technology of condensate oil and gas wells stimulated by electromagnetic induction heating during middle or late exploitation period were introduced for the first time at home and abroad. A new kind of electromagnetic wave induction heating equipment XAEMH-1 was developed. Taking near wellbore zone temperature field as the main research object, which is the key factor for the condensation and retrograde vaporization during electromagnetic heating, the mathematical simulation model for a condensate oil and gas well stimulated by electromagnetic heating to eliminate blockage near wellbore region was established. A corresponding computer system was developed to dynamically predict and evaluate the efficiency of this electromagnetic heating process. Through this computer system, the near wellbore region distributions of several important factors such as temperature, pressure, condensate oil saturation and relative permeability can be described quantitatively. A condensate gas well in a late exploitation period reservoir here in China was chosen as a practical example to test the effectiveness of this new technology and some satisfactory results were obtained.These results proved that it is feasible to eliminate the near wellbore region blockage by electromagnetic heating. A new prospective stimulation method was given for the condensate oil and gas reservoirs during middle or late exploitation period.     

含水合物泥质粉细砂三轴试验及本构模型

为了得到不同有效围压和水合物饱和度对含水合物沉积物强度和刚度的影响规律,并得出相应数学表达式,以南海北部沉积物土样级配作为参考,配制人工泥质粉细砂,利用自主研发的含水合物沉积物三轴试验机,制备不同饱和度的含CO₂水合物沉积物,在1, 2, 4 MPa有效围压下等向固结并进行三轴剪切试验。由于围压能自动根据气压的变化而变化,所以在水合物生成过程中有气体消耗但有效围压保持不变。试验结果表明:初始弹性模量随水合物饱和度的增加而增加,与有效围压无关;初始泊松比随着有效围压增加而减小,而随水合物饱和度的增加而增加;黏聚力随水合物饱和度的增加而增加,而内摩擦角与水合物饱和度无关。在邓肯-张模型的基础上,引入参数水合物饱和度,建立了含水合物沉积物的非线性弹性本构模型。最后,用试验数据对模型进行了验证,其结果符合较好。     

Investigation and Application on Gas-Drive Development in Ultra-low Permeability Reservoirs

To select a proper displacement medium with the purpose of developing ultra-low permeability reservoirs both effectively and economically, three kinds of gases, including CO2, NG and N2, are studied through physical modeling and numerical simulation under the specified reservoir conditions. The results indicate that the oil recovery through water injection is relatively low in ultra-low permeability reservoirs, where the water breaks through early and the water cut rises rapidly. Gas injection can enhance the production, of which the gas-drive efficiency depends on the injection pressure and the gas itself. CO2 is proved to be the best one after comprehensive consideration of the recovery speed, the overall recovery efficiency and the time needed for gas to break through. The pressure of CO2 injection in the field experiments is lower, compared with that of water-drive. The injectivity index of CO2 is 7.2 times as high as that of water, and the oil production of the test well group increases by about 4 t/d.     

蒸汽沿井筒流动过程数值模拟

蒸汽沿井筒流动过程中,蒸汽参数(压力、温度及干度等)、径向散热损失和垂向压力能损失,均沿流动过程变化。本文运用传热学、热力学及流体力学等学科知识,建立了井筒数值模拟综合计算模型,给出了求解方法,并进行了模拟计算。本文所建模型,综合考虑了蒸汽流动过程中压力、温度、干度和热损与压降的相互影响,给出了更为精确的无因次时间函数的表达式,通过试验确定了接箍对总传热系数的影响,同时也通过试验修正了隔热管性能变化对隔热性能的影响。     

掺水泥粉土的改良风积沙三轴压缩特性

基于单掺5%水泥的经济性设计指标,开展了混掺水泥粉土的改良风积沙三轴压缩试验,分析了改良风积沙试样不同围压下的应力-应变及强度特性,揭示了不同掺比改良风积沙黏聚力和内摩擦角的变化规律,以及改良风积沙的破坏形式及剪切破坏机理。结果表明：改良风积沙的应力-应变关系曲线均为应变软化型曲线;弹性模量和破坏强度与围压正相关,弹性模量在粉土掺量增至15%时达到峰值;破坏强度与粉土掺量正相关;10%粉土掺量下改良风积沙黏聚力最大,内摩擦角则随粉土掺量增加而单调增长。水泥水化物包裹在沙粒表面,增加了沙粒表面粗糙度,并在沙粒之间的空隙形成网状结构,将沙粒联结起来,阻碍沙粒相对运动;掺入适量粉土可填充沙粒和水化物之间的空隙,但过量粉土会制约水化反应,同时碱性离子与水化物反应产生胶结能力差的硅酸钠和铝酸钠,导致改良风积沙整体性能下降。     

压力脉冲在井眼气－液两相流传播的数值模拟

本文对压井期间节流阀调节过程中压力脉冲在井眼环空气－液两相流中传播速度进行了数值模拟。建立并求解了一维拟线性双曲型偏微分方程组，从而能够给出气侵后环空气－液两相流分布和在压井期间的气－液两相流分布。同时导出了压力脉冲在气－液两相流中传播速度公式，给出了计算节流阀调节间隔计算方法。举例计算出了节流阀调节后压力脉冲经过钻柱泥浆及环空流体中传播时间。利用本方法可以适时调节节流问，使压井期间井底保持较恒定的压力，从而真正符合并控理论。