声波在高含蜡油生产中防蜡作用的实验研究

含蜡原油在生产过程中,蜡组分随井筒温度的降低而逐渐析出,这种结蜡现象导致原油粘度急剧上升而影响油井的正常生产,因此采取防蜡措施在高含蜡原油生产中是必不可少的,利用声波进行防蜡的实验研究表明,声波作用可以破坏蜡晶网状结构,降低原油粘度和凝固点,从而达到防蜡的目的,声波防蜡以其独特的作用机理较其它防蜡方法具有更大的可靠性和更加广阔的应用前景。     

嗜蜡菌对含蜡原油除蜡降黏作用的影响

含蜡原油因其蜡组分的存在而导致原油在低温环境中黏度变大、流动性变差,而在管输的过程中,蜡晶的析出会降低管道的输送能力、甚至有堵塞管道的威胁。本文利用已发现的一株嗜蜡菌,利用其发酵液降解含蜡原油中的蜡组分,实验证明处理5天后的原油含蜡量降低、表观黏度下降,偏光显微镜观察油中蜡晶结构明显变小而分散。软件ImageJ对显微镜照片处理后测量得到:最大蜡晶粒径从609.1μm下降至72.1μm;平均费雷特径大小从79.1μm下降到50.3μm。     

复配菌对原油微观结构变化的研究

含蜡原油因其蜡组分的存在使其在开采和运输的过程中易使蜡晶析出,蜡晶析出堵塞管道,减小输送半径,严重时会发生凝管停运等事故,造成严重的经济损失.本文利用已发现的一株嗜蜡菌与产表面活性剂菌株进行复配,利用得到的复配菌发酵液按一定比例接种于含蜡原油中,实验表明作用7天后的原油含蜡量降低;利用ImageJ软件对偏光显微镜图片进行后处理发现蜡晶结构变小且密集;最后利用FBRM技术分析得原油中大粒径所占比例减少,小粒径所占比例增多.复配菌作为一种新方法、新思路,可以有效地降低含蜡原油在开采和运输过程中产生的危害,减少经济损失.     

原油中声衰减和声速的温度特性的测量

原油是一种混合物。它的一些性质随温度而变，如原油的声衰减和声速都是温度的函数．本文使用一个换能器发射声波，另一个换能器接收声波，在实验室内测得12t－80℃之间的声波幅度值，利用插值算法，求出该温度范围内原油声衰减的温度特性曲线；利用线性拟合算法，求出原油声速的温度特性曲线。结果表明：随着温度的升高，原油的声衰减和声速都呈下降趋势，而且测量结果与换能器的灵敏度无关．     

含蜡原油乳状液触变性研究

触变性是含蜡原油管道停输再启动压力计算和原油可泵性评价的重要基础资料,为了确定油水混输海底管道的停输再启动特性,必须掌握含蜡原油乳状液的触变性.本文在脱水含蜡原油触变性研究的基础上,对含蜡原油油包水乳状液的触变性进行了研究,发现含蜡原油乳状液的触变趋势与脱水原油类似;建立了一个描述含蜡原油乳状液在恒定剪切速率作用下剪切应力衰减这一触变行为的数学模型.用最小二乘法对本文和文献中的实验数据进行拟合,结果表明,该模型能够较准确地描述在恒定剪切速率作用下剪切应力衰减的触变行为,不仅适用于含蜡原油乳状液,对脱水含蜡原油和化学剂改性含蜡原油也适用,与其他触变模型相比,该模型具有参数较少、计算方便等优点.     

一种线状纳米降凝剂与磁场协同对高含蜡原油的改性研究

本文研究了一种线状纳米降凝剂对高含蜡原油屈服应力的影响,采用偏光显微镜获得了加剂对原油中蜡晶形貌的影响。在此基础上引入磁场作用,分析了线状纳米降凝剂与磁场协同对屈服应力的影响。结果表明,相比传统乙烯/醋酸乙烯酯降凝剂,线状纳米降凝剂能够更明显的降低原油屈服应力。当施加本文所研究的恒定磁场时,磁场的引入削弱了线状纳米降凝剂对原油屈服应力的影响;而当施加本文所研究的交变磁场时,磁场能够起到增强线状纳米降凝剂对原油屈服应力的改善效果。     

沉积物中声速和衰减系数的宽带测量方法

海底沉积物作为海洋波导声传播的下边界普遍存在于大洋中,获知其特性对于准确的声传播和混响建模是十分必要的。为了能够快速而准确地测量沉积物中的声速和衰减系数,提出一种基于脉冲压缩技术的测量方法,对接收信号进行压缩来提取透射波,根据不同厚度样品的透射波来计算沉积物中的声速和衰减系数。该方法不仅可以克服实验过程中经常遇到的多途干扰,而且测量过程简单,可以同时获得测量频带内所有频点的声速和衰减系数,即实现了对声速和衰减系数的宽带测量。在实验室环境条件下,90~170kHz的测量频带内,测得沙样品中的声速为1710~1713m/s,衰减系数在56~70dB/m之间。通过窄带和宽带测量结果的比较可以看出,声速的宽带测量结果与窄带测量结果吻合得较好,而衰减系数在频带后半部分存在较大的起伏。      

复配菌优化培养及其在原油中的应用研究

微生物除蜡、降黏技术因高效、经济、无毒、无污染的优点,被广泛研究和采纳。本论文主要研究了嗜蜡菌SL-7以及用BH-12进行复配制成微生物菌剂SB7-12的除蜡、降黏研究。实验结果表明:优化后的复配菌SB7-12对原油具有降黏与除蜡双重功效,对原油中石蜡的降解率达83.3%,降黏率可达到43.3%。显微镜结果表明,微生物菌剂的加入使原油中微观蜡晶结构呈现出小而分散的特点,表观黏度降低,从而有利于提高原油流动性。     

沉积物中声速和衰减系数的宽带测量方法

海底沉积物作为海洋波导声传播的下边界普遍存在于大洋中,获知其特性对于准确的声传播和混响建模是十分必要的。为了能够快速而准确地测量沉积物中的声速和衰减系数,提出一种基于脉冲压缩技术的测量方法,对接收信号进行压缩来提取透射波,根据不同厚度样品的透射波来计算沉积物中的声速和衰减系数。该方法不仅可以克服实验过程中经常遇到的多途干扰,而且测量过程简单,可以同时获得测量频带内所有频点的声速和衰减系数,即实现了对声速和衰减系数的宽带测量。在实验室环境条件下,90~170 kHz的测量频带内,测得沙样品中的声速为1710~1713 m/s,衰减系数在56~70 dB/m之间。通过窄带和宽带测量结果的比较可以看出,声速的宽带测量结果与窄带测量结果吻合得较好,而衰减系数在频带后半部分存在较大的起伏。     

管输含蜡原油的化学组成与变化规律

本文主要对含蜡原油化学进行计算研究。一方面,根据燃料化学反应的常用计算方法,得出了油田含蜡原油的比化学反应,并通过对比前人得出的燃料油的比化学反应值,证明此方法切实可用;另一方面,从化学扩散的一般计算表达式出发,基于管输过程蜡分子的扩散沉积机理,推导得出原油扩散的计算式,并对管输过程中油流扩散的变化情况进行了分析,旨在为以后进一步研究原油输送系统的分析提供理论基础。     

Temperature dependent ultrasonic properties of aluminium nitride

Hexagonal wurtzite structured aluminium nitride has been characterized by the theoretical calculation of ultrasonic attenuation, ultrasonic velocity, higher order elastic constants, thermal relaxation time, acoustic coupling constants and other related parameters in temperature range 200-800 K for wave propagation along the unique axis of the crystal. Higher order elastic constants of AlN at different temperatures are calculated using Lennard-Jones potential for the determination of ultrasonic attenuation. A decrease in ultrasonic velocity with temperature has been predicted, which is caused by reduction in higher order elastic constants with temperature. The temperature dependent ultrasonic properties have been discussed in correlation with higher order elastic constants, thermal relaxation time, thermal conductivity, acoustic coupling constants and thermal energy density. Anomalous behaviour of the attenuation is found at 400 K. On the basis of attenuation, the ductility and performance of AlN have been studied.     

Ultrasonic wave propagation in IIIrd group nitrides

The ultrasonic attenuation in hexagonal structured (wurtzite) third group nitrides (GaN, AlN and InN) has been evaluated at 300 K for an ultrasonic wave propagating along the unique axis of the crystal. Higher order elastic constants of these materials are calculated using the Lennard-Jones potential for the determination of ultrasonic attenuation. The ultrasonic velocity, Debye average velocity, thermal relaxation time and acoustic coupling constant are evaluated along the z-axis of the crystal using the second order elastic constants and other related parameters. The contributions of the elastic constants, thermal conductivity, thermal energy density, ultrasonic velocity and acoustic coupling constant to the total attenuation are studied. On the basis of the ultrasonic attenuation, it can be concluded that the AlN is more ductile than either GaN or InN at 300 K. Orientation dependent characterization has been achieved by calculation of the orientation dependent ultrasonic velocity, Debye average velocity and thermal relaxation time for the materials.     

Ultrasonic properties of strontium titanate at the 105°K transition

The temperature dependence of the sound velocity and the ultrasonic attenuation has been measured by the pulse-echo method in single crystals of strontium titanate in the vicinity of the 105°K structural transformation. Special attention is paid to the anisotropy of these measured quantities. The behaviour of the attenuation in the cubic phase can nearly quantitatively be interpreted as interaction with critical fluctuations belonging to the R-corner phonon mode. A numerical estimate leads to the conclusion that also in the tetragonal phase this fluctuation scattering contributes most to the attenuation, in comparison to resonant interaction (of the Landau-Khalatnikov type) and domain effects, which under the present experimental conditions dominate the sound velocity behaviour.     

Ultrasonic velocity changes in a nickel single crystal - domain effect

We have measured detailed ultrasonic velocity changes in a nickel single crystal as a function of magnetic field in the frequency range 10 to 150 MHz at room temperature. Qualitatively the velocity changes follow the attenuation changes. The magnitudes of the velocity differences between the demagnetized and the fully magnetized states decrease slowly with the increase of frequency, and the decrease is slower than predicted by Mason's theory. Both velocity and attenuation, measured at 10 MHz, show similar behaviour in the temperature range 23 to 300°C.     

Relaxation and resonance ultrasound attenuation by Jahn-Teller centers in a GaAs:Cu crystal

The interaction of ultrasound with Cu_Ga4As in a GaAs:Cu crystal has been experimentally studied. The temperature dependences of the attenuation of all normal ultrasonic modes propagating in the ??110?? direction both in doped copper and in nominally pure gallium arsenide crystals have been measured. In the GaAs:Cu crystal, the attenuation peak has been revealed for a transverse wave polarized along the ??110?? axis whose elastic shifts correspond to the symmetry of the tetragonal mode of the Jahn-Teller effect. The temperature dependence of the attenuation of this wave indicates that two types of attenuation??relaxation and resonance??occur. The constructed temperature dependence of the relaxation time indicates that tunneling through the potential barrier between the minima of the adiabatic potential energy is the main relaxation mechanism at temperatures below 10 K. Tunneling splitting estimated from experimental data is in good agreement with the theoretical estimate.     

用超声方法研究掺丙氨酸氘化TGS晶体的相变

 采用超声脉冲重合技术，观察LADTGS在压力升至0.8 GPa，温度在20~90 ℃范围内，超声波在晶体中传播的速度及声衰减系数随温度变化的规律，发现在常压下，在64 ℃处声速随温度变化曲线的斜率有明显变化，对应的声衰减也有一明显吸收峰。随压力升高，T_c以约12 ℃/GPa的速率向高温方向移动。这一现象与介电常数的研究结果大致相同。     

Dielectric and ultrasonic investigation of phase transition in cuinp2s6 crystals

Investigation results of dielectric and ultrasonic properties of layered CuInP₂S₆ crystals are presented. At low frequencies, dielectric spectra are highly influenced by the high ionic conductivity with the activation energy of 7357.4?K (0.635?eV). The high-frequency part of the spectra is determined by relaxational soft mode. The critical slowing down and Debye-type dispersion show the order–disorder type of the phase transition. The temperature dependence of the relaxational soft mode and dielectric contribution show a quasi-one-dimensional behaviour. Ultrasonic velocity exhibits critical slowing down which is accompanied by attenuation peaks in the phase transition region. Layered CuInP₂S₆ crystals have extremely large elastic nonlinearity in the direction perpendicular to layers. The nonlinear elastic parameters substantially increases at the PT temperature.     

Features of high-frequency ultrasound propagation in the temperature range of structural and magnetic phase transitions in La1−x SrxMnO3 (x=0.175) manganite

The propagation of ultrasonic waves at a frequency of 770 MHz in a La_0.825Sr_0.175MnO₃ single crystal is investigated in the temperature range 350–150 K. It is found that the velocity, attenuation, and mode composition of ultrasonic waves change at temperatures of 315–280 and 220 K. These changes correlate with the structural and magnetic phase transitions and can be explained in terms of the Jahn-Teller distortions of the crystal lattice.     

Resonance attenuation of ultrasonic waves in a superconductor with a moving vortex structure

Equations describing the interaction of ultrasonic waves with a moving vortex structure are derived. The addition to attenuation and the relative change in the velocity of longitudinal ultrasonic waves due to this interaction are calculated. It is found that when a longitudinal ultrasonic wave propagates along the direction of motion of the vortex structure and the velocity V of the structure is equal to half the velocity of the wave, then anomalous acoustic attenuation occurs and the contribution from the ultrasound-vortex interaction to the velocity of the ultrasonic wave vanishes. It is shown that if the vortex structure moves at a sufficiently high velocity, then (in contrast to the case of the structure at rest) a weakly damping collective mode propagating with velocity 2V arises in the structure. It is this mode that is responsible for anomalous attenuation of longitudinal ultrasonic waves.     

Tunneling Relaxation Mechanisms of the Jahn–Teller Complexes in a CaF2:Cr2+ Crystal

JETP Letters - The temperature dependences of attenuation and the velocity of ultrasonic waves at frequencies of 26–158 MHz in a CaF2 fluorite crystal at the substitution of...