Combined control of fluid adsorption capacity and initial permeability on coal permeability

The variations of strain and permeability of coal were systematically studied through the physical simulation of N2 and water injection.The effects of fluid adsorption capacity and initial permeability on strain,permeability and the dominant effect of pore pressure were discussed.The adsorption strain and strain rate of coal during water injection are significantly higher than those during N2 injection.An edge of free adsorption exists in the early phase of N2 and water injection,which is related to fluid saturation.Within this boundary,the strain rate and pore pressure are independent.Moreover,the injec-tion time of initial stage accounts for about 20%of the total injection time,but the strain accounts for 70%of the total strain.For water injection,this boundary is about half of water saturation of coal.Besides,the influence of pore pressure on permeability is complex,which is controlled by adsorption capacity and initial permeability of coal.When the initial permeability is large enough,the effect of adsorption strain on permeability is relatively weak,and the promoting effect of pore pressure on fluid migration is dominant.Therefore,the permeability increases with increasing pore pressure.When the initial permeability is relatively low,the pore pressure may have a dominant role in promoting fluid migration for the fluid with weak adsorption capacity.However,for the fluid with strong adsorption capacity,the adsorption strain caused by pore pressure may play a leading role,and the permeability reduces first and then ascends with increasing pore pressure.

Magnetic Hysteresis and Complex Initial Permeability of Cr³⁺Substituted Mn-Zn Ferrites

The impact of Cr3+ ion on the magnetic properties of Mn0.50Zn0.50CrxFe2-xO4 (with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) has been studied. Ferrite samples were synthesized by combustion method and sintered at various temperatures (1250°C, 1300°C and 1350°C). The structural properties were investigated by means of X-ray diffraction patterns and indicated that the samples possess single phase cubic spinel structure. The lattice parameter decreases with the increase in Cr3+ content, as the ionic radius of Cr3+ ion is smaller than that of Fe3+. The average grain size (D), bulk density (ρB) and initial permeability (μi’ )decreases with increase in Cr3+ content whereas porosity follows its opposite trend. The ρB was found to increase with increase in Cr3+ content as the sintering temperature (Ts) is increased from 1250°C to 1350°C. The Ts affects the densification, grain growth and (μi’ ) of the samples. The (μi’ ) strongly depends on average grain size, density and intragranular porosity. The B-H loops of the compositions were measured at room temperature. The saturation magnetization (Ms), coercivity (Hc) and hysteresis losses were studied as a function of Cr3+ content. The Ms was found to decrease with the increase of Cr3+ content, which is attributed to the dilution of A-B interaction.

NANOCRYSTALLINE STRUCTURE AND INITIAL PERMEABILITY OF ANNEALED Fe_(73.5)Cu_(1)W_(3)Si_(13.5)B_(9) Alloy

The nanocrystalline structure of annealed Fe73.5 Cu1 W3Si13.5B9 alloy has been investigated by using the XRD and the TEM methods. The relation between the initial permeability and the microstructure of the annealed alloy has been discussed. The crystalline phase in annealed Fe73.5 Cu1 W3Si13.5B9 alloy is the α-Fe(Si) phase with DO3 superstructure. The volume fraction, Si content and degree of order of the αFe(Si) phase increase with increasing annealing temperature. In the temperature range of 490-570℃, the α-Fe(Si) phase has a size of 13 nm, and its grain number increases as the annealing temperature is increased. The DO3 ordered region in the α-Fe(Si) grain is spherical approximately, and its size increases as the annealing temperature increases. The size of the DO3 ordered region is 12.8 nm at the temperature of 570℃,which is close to that of the α-Fe(Si) grain. There is obvious change in the structure of the residual amorphous phase during annealing, and the nearest atomic distance and the short-range order of residual amorphous phase reach maximum and minimum at 530℃, respectively. The initial permeability of annealed Fe73.5 Cu1 W3Si13.5 B9 alloy is not only dependent on the size, volume fraction and Si content of the α-Fe(Si) phase but also related to the structure state of the residual amorphous phase.

Rolling contact fatigue nondestructive testing system for a bearing inner ring based on initial permeability

Due to the fact that rolling contact fatigue is not easily detected, and residual life is not easily evaluated in the early stage of bearing life, a nondestructive testing method based on initial permeability is proposed. By analyzing the crack propagation mechanism, a fatigue state detection system based on differential signals is designed. A simulation model of the detection of the inner ring of the pulse signal is established by using the electromagnetic field simulation software. The effects of the height of the coil, the inner and outer diameter, the number of coil turns, the diameter and the height of the ferrite core of the probe on the differential value of the detection signal are simulated. The parameter combination of the maximum difference value of the signal is used as the structural size of the sensor, and the detection sensor is designed and fabricated. Moreover, the bearing fatigue test system is designed, and the bearing is tested. The results show that the system has good detection ability for rolling contact fatigue and verifies the mechanism and trend of crack propagation in the inner ring of the bearing.

INITIAL BINDING CAPACTIES OF CHLORIDE ION OF COMPONENTS IN HIGH-PERFORMANCE CONCRETE

An investigation is reported on the influence of different components of high performance concrete (HPC) on the initial binding capacities (IBC) of chloride ion. The testing results demonstrate that cement has the largest IBC, and the relative binding ratio is as high as 30% of total ion amount. Among the mineral admixtures, fly ash has the largest IBC of chloride ion. The IBC of silica fume is about 14.4%, which is smaller than that of fly ash. The IBC of refined ground blast-furnace slag (microslag) is abnormal due to the influence of sulfate ion contained. The addition of superplasticizer and corrosion inhibitor containing calcium nitrite weakens the IBC of mixtures. The fluidity and pore-filling effect of mineral admixtures are studied with paste samples with WIC ratio of 0.3. The influence mechanism of various components in high-performance concrete in IBC is studied further through SEM and Mercury Instrusion Porosimetry tests with paste samples at the age of 3 days.

低渗透砂岩储层压驱裂缝起裂及扩展特征实验研究

针对水驱低渗透油藏地层能量补充困难、“注不进、采不出”的问题,胜利油田结合提液稳产技术需求,形成了针对低渗透油藏的压驱注水技术。压驱通过高压注水有效提高了水驱注水总量,矿场试验表明压驱过程中储层形成了一定规模的裂缝,但压驱破裂压力及裂缝扩展规律尚不明确。为了优化矿场施工参数,采用天然砂岩和真三轴水力压裂平台开展5组压驱与压裂物理模拟实验,研究注入排量对压驱破裂压力和裂缝形态的影响,分析注入方式对裂缝形态的影响,并利用多孔弹性理论分析其成因。结果表明:压驱过程同时存在明显的起裂压力和破裂压力,裂缝发育呈现弹性变形、微破裂和失稳破裂3个阶段。随着注入排量升高,起裂压力基本不变,破裂压力逐渐降低。H-F模型可用于预测起裂压力,H-W模型可用于预测破裂压力的上限。压驱裂缝扩展方向受岩石非均质性的影响较大,非均质性通过影响井眼附近的孔隙压力场,进而改变应力场,使裂缝扩展方向不再垂直于最小地应力。定排量注入时,分支缝与主裂缝夹角大,形成鱼骨状裂缝;变排量注入时,分支缝与主裂缝近平行,在主裂缝两侧形成裂缝带。

基于小样本数据的储层渗透率预测方法

针对Timur/Coates和SDR公式计算储层渗透率处理步骤繁琐的缺点,设计了一个实现非线性回归的单隐层前馈神经网络(single hidden layer feedforward neural network,SLFNN),该网络包含一个具有非线性激活函数的隐含层、两个线性全连接层和一个dropout层。为了防止学习过程中陷于局部最优和小样本数据集造成的过拟合,使用了Adam优化器、ReLU激活函数、何恺明均匀分布权重初始化方法和余弦退火热重启学习率调整算法。以某油田A~D四口生产井不同层位上的测井和岩心构成的小样本数据作为训练集和验证集,采用5折交叉验证方法,确定了隐含层神经元个数、初始学习率和dropout层神经元失活概率。最后以同区块E井数据作为测试集,使用4种模型(SLFNN、随机森林回归、支持向量回归和极端梯度提升回归)分别对渗透率进行了预测和对比。实验结果表明,在测试集下SLFNN模型的平均绝对误差(MAE)和决定系数(R 2)均比其他3种模型的优,说明SLFNN模型对储层渗透率的预测是有效的。

强降雨作用下引入分形理论的浅层边坡入渗及稳定性分析

为探究降雨过程中土体实际入渗能力动态变化对边坡降雨入渗规律及其稳定性的影响,从土体级配特征的角度出发,首先基于分形理论推导了不同级配特征土体的饱和渗透系数分析模型;进一步考虑入渗区椭圆形过渡带的影响,根据不同降雨历时下过渡带与入渗区的厚度比例关系对入渗区等效渗透系数进行实时修正,提出了不同级配特征土体的改进GA入渗模型;最后,基于改进GA入渗模型建立了考虑土体抗剪强度随级配特征及降雨时间变化的浅层边坡稳定性分析修正模型。与已有结果对比表明建立的模型能够准确地表征降雨过程中土体入渗状态及剪切强度变化特征。参数分析表明:土体孔隙分布特征与饱和渗透系数具有明显的正相关关系,其直接影响坡体水分剖面分布及坡面径流出现时间;湿润峰推移速率随坡体初始含水率的增大而加快,致使相同降雨历时下入渗区过渡带占比减小,进而实时影响入渗区等效渗透系数;坡体过渡带稳定性受土体级配特征及初始含水率的影响较为显著,坡体容易在过渡带发生失稳破坏。故在强降雨作用下边坡的失稳分析中,需额外注意入渗区过渡带的稳定性。

无石棉纤维水泥平板的透水性的比较研究

论文讨论了无石棉纤维水泥平板底材对透水性的影响因素,比较了三种使用量最大的底材的外观和特性,介绍了它们的差异和优缺点。测试了三种底材在不同时间的透水值,讨论了透水值的大小和离散程度,评价了底材的质量。通过比较和分析探讨出底材的初始透水性值可能是影响透水性的关键因素。

建筑涂料在不同底材上透水性的结果分析和机理研究

总结了涂料透水性的影响因素,比较了涂料在不同底材上透水性规律和差异,对透水性试验底材的选用提出了建议。另外本文还从微观分析的角度,分析了底材的红外光谱、热失重曲线和X射线衍射结果,剖析了底材中的成分;从成分的角度说明了不同底材的联系和区别。

渤海低渗储层液氮压裂技术可行性研究

渤海低渗储层改造面临产量递减快和稳产期短的问题。液氮压裂技术可以通过形成复杂裂缝以增强地层能量,提高油气井产量并延长稳产期,但是该技术在海上应用的可行性有待研究。为此,通过建立液氮在大尺度裂缝内的流动传热模型,分析了液氮压裂在渤海低渗储层中的造缝能力,结合常规水力压裂的携砂效果,评估了液氮作为携砂液需要的排量和液量,并综合考虑液氮压裂的施工压力和施工规模,分析了液氮压裂在海上的适用性。分析结果表明:提高液氮注入排量是扩大复杂裂缝造缝范围的有效手段,以4.32 m^(3)/min的排量注入液氮60 min,可以形成半长为44 m的复杂裂缝;液氮作为携砂液,达到常规水力压裂携砂铺置效果所需的排量为9~14 m^(3)/min。针对海上作业特点,提出了液氮携砂压裂和液氮复合压裂2种海上液氮压裂工艺,液氮复合压裂工艺具备海上实施条件,有望成为渤海低渗储层开采的重要技术储备。

基于降阶投影的初始渗流场反演方法

为了解决传统基于降阶模型的参数反演方法的高耗时问题,提出了一种改进的降阶反演方法(IterROM),用于执行快速参数反演任务。不同于传统降阶反演方法先训练后反演的流程,该方法将参数反演与降阶模型训练紧密融合,使用训练中的降阶模型代替原始模型进行参数反演,同时将反演结果应用于降阶模型的训练。该方法在参数反演阶段使用观测资料和后验误差共同组成目标函数,并使用降阶模型解与全阶模型解的最大节点误差作为迭代终止精度。经过某工程初始渗流场反演模型的测试,发现IterROM相比传统方法精度高、计算成本低,可用于快速执行初始渗流场的反演任务。

基于响应面法的煤体有效抽采半径多因素交互作用

钻孔有效抽采半径是煤层瓦斯抽采参数设计的重要指标。为探究煤体基础物性因素(含水率、渗透率、瓦斯压力)对钻孔有效抽采半径的影响特性,首先基于煤的基质-裂隙双重孔隙理论,考虑水分对裂隙开度及基质瓦斯吸附性能的弱化影响,构建了考虑水分影响的煤体渗透率模型与固-气多场耦合模型;其次利用多物理场数值模拟方法并结合响应面分析法研究了不同因素对钻孔有效抽采半径的交互作用。研究发现钻孔有效抽采半径与初始渗透率呈正相关,而与初始瓦斯压力、含水率均为负相关;建立了瓦斯抽采半径与三个因素的二次多元响应面模型,并分析发现含水率、初始瓦斯压力、渗透率对钻孔有效抽采半径的影响显著性逐次降低,并且在一定程度上,煤体初始瓦斯压力的增加会弱化煤岩初始渗透率和含水率对钻孔有效抽采半径的影响,煤体初始渗透率和含水率也会显著改变初始瓦斯压力对钻孔有效抽采半径的影响,然而煤体初始渗透率几乎未改变含水率对钻孔有效抽采半径的影响。

水性环氧树脂灌浆材料的制备及渗透性能研究

以水性环氧树脂E51为原料、二乙烯三胺(DETA)为固化剂,制备出了水性环氧树脂灌浆材料,研究了DETA用量对灌浆材料凝结时间、黏度、力学强度和渗透性能的影响。结果表明,随着固化剂DETA质量分数的增加,水性环氧树脂灌浆材料的初凝时间逐渐降低,黏度持续增大,粘接强度先增大后减小,热稳定性提高,热失重速率减慢,残炭率提高,渗透时间增多。当DETA质量分数为30%时,灌浆材料的初凝时间最短为8.0 h,对应时刻的黏度最大为80334 mPa·s;当DETA质量分数为25%时,灌浆材料的粘接强度和抗压强度达到了最大值,分别为2.94和59.9 MPa,对应的断裂延伸率为13.82%;在800℃时,DETA质量分数为25%的水性环氧树脂灌浆材料的残炭率为9.3%,渗透时间为1709 s,热稳定性和渗透性能较好。综合分析可知,DETA的最佳质量分数为25%。

CO_(2)羽流地热系统热提取率影响因素数值模拟

为获得CO_(2)羽流地热系统采热特性与不同影响因素之间的关系,通过建立三维几何模型,利用COMSOL Multiphysics软件进行数值模拟研究,深入探讨井筒直径、注采井距、储层渗透率、初始孔隙率以及天然裂缝缝长等因素对CO_(2)羽流地热系统采热特性的影响。模拟研究结果表明:在控制变量法下,羽流地热系统热提取率随井筒直径的增大呈现先增加后减少的趋势;热提取率随着热储渗透率和注采井距的增大而增大;初始孔隙率增加,热储渗透性能变好,热提取率提高;由于天然裂缝的存在,增大流体流动性,降低生产温度,热突破程度更明显,系统采热效率降低。可见研究结果为优化CO_(2)羽流地热系统的采热性能提供依据,同时指导深部地热能的开采。

外加力与回流焊对高初始磁导率锰锌铁氧体性能的影响

在对提供的外径为6mm的初始磁导率高、中、低的三款锰锌铁氧体的非涂装和涂装磁环施加垂直力分别为0kg/f、1kg/f、2kg/f、3kg/f、4kg/f和5kg/f的力,用Aglient精密型LCR表测试磁环施加垂直力的电感(L_(s)),另外,磁环经过回流焊(高温250℃停留3min,总时间7min)处理前后,使用IWATSU全自动功率损耗B-H测试仪测试感值(L_(s))、饱和磁通密度(B_(m))和磁通量(H_(c))的值。研究结果表明,垂直力对外径为6mm磁环的μi影响显著,初始磁导率的大小与垂直外加力对初始磁导率影响的大小成正相关性。同时,回流焊中高温过程对材料的应力释放有效,Bm表现出变大的趋势。

海上油田某区块应用水力压裂技术机理及效果研究

海上油田某区块水力压裂的技术应用欠缺压裂机理及开发规律分析评价。通过对水力压裂原理分析建立低渗压裂裂缝起裂模型,运用真三轴水力压裂试验装置进行直井水力压裂模拟试验,并在海上A区块进行现场应用,对压裂效果进行评价。结果表明:流体黏度越高裂缝起裂排量越小,起裂排量与地层破裂压力梯度呈线性正相关,射孔深度越深、射孔角度越小,裂缝起裂排量越高;在压裂工艺参数上采用孔密16孔/米的单螺旋(45°)射孔方式、注入流体黏度为30~40 mPa∙s、注入排量为2.7 m^(3)/min时起裂效果较佳;A区块4口压裂井实现平均单井日增油23%。该研究为水力压裂技术在海上油田区块应用提供了理论支撑。

Synthesis, Permeability and Microstructure of the Optimal Nickel-Zinc Ferrites by Sol-Gel Route

The optimum ferrite can be obtained through free-microstructural defects where such defects are always encountered in the conventional ferrites often caused by chemical inhomogeneity. In this study, Ni-Zn ferrite was synthesized and fabricated by means of a sol-gel route. Thermal gravimetric analysis (TGA) was used to study the thermal transforma-tion of the ferrite in air. Parts of the sol-gel powder heated at elevated temperatures were characterized by X-ray dif-fraction (XRD) method and Scanning Electron Microscopy (SEM) to reveal the crystallized single-phase and the struc-ture of the obtained ferrite. Fourier transform infrared spectroscopy (FT-IR) was assisted to investigate the structure. The microstructures of the toroidal cores were obtained at two different sintering temperatures and compared with those obtained via the classic method. In addition to that, the magnetic properties were measured. The initial magnetic permeability was found to increase with the increasing of the frequency as a result of the domain wall motions and the corresponding loss was small. Therefore, a well defined polycrystalline microstructure ferrite via an easier preparation methodology as compared to the classic method is obtained.

Complex Permeability of Ferrites as Intrinsic and Extrinsic Properties

CIP （complex initial permeability） spectra of PF （polycrystalline ferrite） are studied both as intrinsic and extrinsic properties. In the former case, main steps of modeling, based on effects coming from polycrystal grain sizes distribution and defects, are described. The obtained relations work well in practice for PF with more or less normal MS （microstructure） and no size effects. Besides, fundamental connection between parameters of CIP and MS is found. Another case--PF with possible size effects （MnZn-ferrites） are studied experimentally for different sizes of cores, unveiling the dependence of phenomena on： dimensions of cross-section, number of turns, width of nonmagnetic gap.

矿山机械轴承无损检测装置研究

为了有效地全方位检测出轴承裂纹,根据轴承材料的铁磁性特征,对轴承采用基于初始磁导率的无损检测方法,设计了一种光滑的支撑装置放置轴承套圈,使套圈借助带轮皮带的摩擦力在固定位置轴向旋转,再采用双检测线圈探头,在轴承套圈的内、外圆表面同时进行检测。该结构简单且易实现,能对轴承套圈进行大批量裂纹检测,有效提高检测效率,降低检测成本。