Mechanisms and capacity of high-pressure soaking after hydraulic fracturing in tight/shale oil reservoirs

Huff-n-puff by water has been conducted to enhance oil recovery after hydraulic fracturing in tight/shale oil reservoirs.However,the mechanisms and capacity are still unclear,which significantly limits the application of this technique.In order to figure out the mechanisms,the whole process of pressurizing,high-pressure soaking,and depressurizing was firstly discussed,and a mechanistic model was established.Subsequently,the simulation model was verified and employed to investigate the significances of high-pressure soaking,the contributions of different mechanisms,and the sensitivity analysis in different scenarios.The results show that high-pressure soaking plays an essential role in oil production by both imbibition and elasticity after hydraulic fracturing.The contribution of imbibition increases as the increase in bottom hole pressure(BHP),interfacial tension,and specific surface area,but slightly decreases as the oil viscosity increases.In addition,it first decreases and then slightly increases with the increase in matrix permeability.The optimal soaking time is linear with the increases of both oil viscosity and BHP and logarithmically declines with the increase in matrix permeability and specific surface area.Moreover,it shows a rising tendency as the interficial tension(IFT)increases.Overall,a general model was achieved to calculate the optimal soaking time.

Analyzing the Flow Field in the Oil Chamber of a Hydrostatic Guide Rail Used for Ultra-Precision Machining: Numerical Simulation and Performance Optimization

In order to explore the impact of different structural design parameters and environmental factors on the performance of the hydrostatic guide rail,the flow field inside its oil chamber is simulated,which provides direction and guidance for the design and optimization of the guide rail system.Based on the theory of fluid lubrication and the Reynolds equation,numerical simulations are performed through a mathematical model.The results suggest that the bearing capacity of the oil film increases with the oil supply pressure.The film thickness and the film stiffness share a positive correlation.Different oil film thickness and different input pressure parameters can have a significant impact on bearing capacity and oil film stiffness.The correlations identified in the present analysis can be used as a basis to optimize the guide rail design.

Research on thermal insulation materials properties under HTHP conditions for deep oil and gas reservoir rock ITP-Coring

Deep oil and gas reservoirs are under high-temperature conditions,but traditional coring methods do not consider temperature-preserved measures and ignore the influence of temperature on rock porosity and permeability,resulting in distorted resource assessments.The development of in situ temperaturepreserved coring(ITP-Coring)technology for deep reservoir rock is urgent,and thermal insulation materials are key.Therefore,hollow glass microsphere/epoxy resin thermal insulation materials(HGM/EP materials)were proposed as thermal insulation materials.The materials properties under coupled hightemperature and high-pressure(HTHP)conditions were tested.The results indicated that high pressures led to HGM destruction and that the materials water absorption significantly increased;additionally,increasing temperature accelerated the process.High temperatures directly caused the thermal conductivity of the materials to increase;additionally,the thermal conduction and convection of water caused by high pressures led to an exponential increase in the thermal conductivity.High temperatures weakened the matrix,and high pressures destroyed the HGM,which resulted in a decrease in the tensile mechanical properties of the materials.The materials entered the high elastic state at 150℃,and the mechanical properties were weakened more obviously,while the pressure led to a significant effect when the water absorption was above 10%.Meanwhile,the tensile strength/strain were 13.62 MPa/1.3%and 6.09 MPa/0.86%at 100℃ and 100 MPa,respectively,which meet the application requirements of the self-designed coring device.Finally,K46-f40 and K46-f50 HGM/EP materials were proven to be suitable for ITP-Coring under coupled conditions below 100℃ and 100 MPa.To further improve the materials properties,the interface layer and EP matrix should be optimized.The results can provide references for the optimization and engineering application of materials and thus technical support for deep oil and gas resource development.

Oxidization characteristics and thermal miscible flooding of high pressure air injection in light oil reservoirs

Physical modeling,numerical simulation and field case analysis were carried out to find out the subsurface thermal oxidation state,thermal oxidation front characteristics and production dynamic characteristics of high pressure air injection thermal oxidation miscible flooding technology.The lighter the composition and the lower the viscosity of the crude oil,the lower the fuel consumption and the combustion temperature are.The thermal oxidation front of light oil and volatile oil can advance stably,and a medium-temperature thermal oxidation stable displacement state can be formed in the light oil reservoir under high pressure conditions.With strong thermal gasification and distillation,light oil and volatile oil are likely to form a single phase zone of gasification and distillation with thermal flue gas at the high-temperature and high-pressure heat front,finally,an air-injection thermal miscible front.In light oil reservoirs,the development process of high-pressure air-injection thermal miscible flooding can be divided into three stages:boosting pressure stage,low gas-oil ratio and high-efficiency stable production stage and high gas-oil ratio production stage.Approximately 70%of crude oil is produced during the boosting pressure stage and low gas-oil ratio high-efficiency and stable production stage.

适用于城市轨道交通车钩装置的液压油-环簧缓冲器特性分析

[目的]目前城市轨道交通车钩装置普遍应用胶泥缓冲器或气液缓冲器,而这两种缓冲器存在内高压易导致介质泄漏。液压油-环簧结构缓冲器可避免因密封问题而引起的泄漏问题,但需分析其对于城市轨道交通车钩装置的适用性。[方法]基于液压油-环簧缓冲器的结构,分析了其压缩过程的受力情况、稳态压缩性能和冲击性,通过仿真分析模拟了车辆冲击试验。[结果及结论]液压油-环簧缓冲器可以承受速度为4 m/s(15 km/h)的稳态压缩,通过了8 km/h以下速度的冲击试验,完全适用于城市轨道交通列车。

基于可变喷油规律的设计分析

为优化轻重型柴油机的燃烧效率以及满足严格的排放法规,提出一种基于双喷油器的可变喷油规律构想。利用Simulink搭建喷油器执行驱动仿真模型,并在发动机仿真台架中进行仿真验证。研究结果表明,通过控制双喷油器开始喷射时刻以及喷射持续时间,可实现方形、斜坡形、靴型和反斜坡形等不同形式的喷油规律。其中,喷油控制策略可对主喷实现靴型、方形、斜坡与反斜坡形、预喷实现斜坡形、后喷实现方形喷油规律,最终通过构建多种喷油规律未来可实现不同工况下的最优喷油规律。

轨道交通无油活塞式主供风单元适应性设计及试验

基于轨道交通主供风单元低振动、低噪音等技术要求,结合间隙启停模式下低运转率、高可靠性等特殊使用工况要求,介绍了适用于中国标准地铁列车的无油活塞式主供风单元设计开发情况,有针对性地说明了开发过程涉及的关键技术,并进行了相关试验验证,验证结果良好。

不同介质作用下轮轨粘着特性研究

利用MMS-2A型微机控制摩擦磨损试验机开展介质工况下的轮轨粘着特性试验,研究干态、水、油、砂、树叶等介质对轮轨粘着系数的影响。结果表明:不同介质工况下的轮轨粘着系数明显不同,干态下轮轨粘着系数最大,油水介质下粘着系数最小,加水和油将显著降低轮轨粘着系数,且油介质下的轮轨粘着系数明显小于水介质下的粘着系数;随环境湿度增加轮轨粘着系数明显降低,当湿度从20%增加到100%时,粘着系数将降低约17%;干态和油水介质下,随轴重增加轮轨粘着系数呈明显增加趋势;轮轨接触面间加入新鲜树叶后粘着系数将降低,树叶与水共同作用下的轮轨粘着系数最小;通过撒砂能提高水油介质工况下的轮轨粘着系数,但会加剧轮轨试样表面损伤,导致剥落损伤出现。

介质作用下轮轨增粘特性

利用MMS-2A滚动摩擦磨损试验机研究了水、油和落叶介质作用下轮轨粘着特性,分析了介质工况下砂、氧化铝和研磨块对轮轨增粘效果的影响。结果表明,水、油和落叶介质会使轮轨粘着系数明显下降,相比干态,水、油和落叶介质工况下,轮轨粘着系数分别降低约53%、83%和86%;落叶与水混合物形成良好的润滑剂,此工况下粘着系数最小;3种介质工况下,撒砂、撒氧化铝颗粒和使用研磨块均能提高粘着系数;水和油介质工况下,氧化铝颗粒提高粘着系数最为明显,砂次之,研磨块最差;落叶介质工况下,由于落叶浆较厚,砂颗粒较大,能迅速穿透增大接触面积,故其最为明显,氧化铝次之,研磨块最差。

水油介质下研磨子对轮轨增黏与损伤影响

利用滚动磨损试验机开展轮轨黏着试验,研究水油介质下研磨子对轮轨增黏与损伤行为的影响。结果表明:水油介质下研磨子具有明显轮轨增黏作用,其增黏效果随施加压力的增加而增大,相同压力作用时油介质下研磨子的轮轨增黏效果更佳;水油介质下施加研磨子会加重轮轨试样的磨损,随压力增加轮轨试样磨损量呈增加趋势;水油介质下研磨子对轮轨试样表面损伤具有较大影响作用,增加压力会加重轮轨试样的表面损伤和塑性流动;随施加压力增加,水介质下轮轨试样损伤从轻微磨损向明显的表面剥离损伤转变,油介质下轮轨试样损伤从轻微点蚀转变为明显的表面疲劳损伤。

铁路轮轨润滑脂的研制

采用IR、XRD、SEM-EDS等手段,对常用铁路轮轨润滑脂进行剖析,得到润滑脂的基础油种类和添加剂组成。研制一种新型铁路轮轨润滑脂,并与常用铁路轮轨润滑脂的性能进行比较。结果表明:研制的润滑脂的最大无卡咬负荷为863 N,比常用铁路轮轨润滑脂的大一倍多,其摩擦因数为0.008～0.032,明显小于常用铁路轮轨润滑脂的0.039～0.051,但烧结负荷小于常用铁路轮轨润滑脂;研制的润滑脂具有更好的胶体稳定性和耐热性。

发动机燃用麻疯树油制生物柴油的非常规排放特性研究

对某共轨柴油机燃用0#车用柴油、麻疯树油制生物柴油及其混合燃料的非常规排放特性进行了研究。在未对原机做任何改动的情况下,分别燃用BD0、BD5、BD10、BD20、BD50和BD100 6种不同体积配比的麻疯树油制生物柴油与石化柴油的混合燃料,分析比较了不同生物柴油配比对发动机醛类、SO2和CO2等主要非常规排放的影响。结果表明:共轨柴油机燃用生物柴油与石化柴油混合燃料后,醛类、SO2、CO2排放均减少,且随着生物柴油掺混比例的升高而降低。

辊—轨摩擦磨损模拟试验研究与分析

在 M2 0 0磨损试验机上对重型钢轨的矫直过程进行了模拟试验。矫直辊试件的表面形状不同 ,使用的润滑油不同 ,模拟试件的磨损结果便有很大差异。本文的结论可供大型轨梁厂加工和使用矫直辊时参考。

共轨系统多次喷射油量波动与轨压的关系

高压共轨系统进行多次喷射时,前一次喷射引起的高压油管内燃油压力波动会导致后一次喷射的喷油量出现偏差。在两个不同的第1次喷射脉宽下,研究轨压对两次喷射中第2次喷射油量波动幅度的影响。结果表明,轨压对第2次喷射油量波动幅度的影响因第1次喷射脉宽的不同而呈现出不同的规律。分别在两个喷射脉宽下研究轨压对单次喷射引起的压力波动幅度的影响。结果显示,小脉宽下,轨压对单次喷射引起的压力波动幅度的影响规律与轨压对第2次喷射油量波动幅度的影响规律相同,但大脉宽下的影响规律稍有不同。讨论轨压对油量波动幅度的影响机理,提出喷油时间波动系数,该系数说明轨压对第2次喷射喷油量波动的影响机理,得到轨压对喷油量波动幅度的影响规律。

中压共轨系统油压控制中PID参数的整定方法

简要介绍了一种柴油机液力中压共轨系统的构成 .在系统共轨管油压的控制中引入遇限制削弱积分法 ,采样周期是从试验测出的阶跃响应曲线获取的 ,并考虑诸多的影响因素 .采用正交试验方法安排试验来整定共轨油压 PID参数 ,并用极差方法分析试验结果 ,从而获取 PID参数的影响主次、影响规律及相互间的关系 ,最终获得某一工况下的

磁场作用下轮轨黏着特性研究

利用JD-1轮轨模拟试验机研究水和油介质工况下磁场对轮轨黏着特性的影响。结果表明:在水和油介质工况下,磁场作用下的轮轨黏着力大于无磁场作用的黏着力,其中加磁水介质黏着力相对增幅达20%,加磁油介质黏着力相对增幅达50%;水和油介质工况下,施加磁场时速度对轮轨黏着力影响不大。

基于AMESim的柴油机高压共轨系统高压油泵的建模仿真分析

对当前高压共轨系统使用较广泛的径向柱塞式高压油泵的结构及工作原理进行研究,通过LMS公司的AMESim软件对高压油泵液力、机械、关键部件(电磁计量阀)分别进行模块化分析,建立带有电磁计量阀的高压共轨系统高压油泵模型,并进行仿真分析。通过改变高压油泵的结构参数,得出高压油泵进、回油孔直径对燃油输出油压、流量的影响,为整个高压共轨系统及共轨管和喷油机的优化设计提供参考。

高压共轨柴油机起动工况高压泵控制策略

针对2.8TC柴油机起动过程的特点,将起动过程分为拖转期和起动期两大部分,由此设计了不同阶段不同的高压泵计量阀控制策略,确定了目标启喷压力和启喷转速,在此基础上试验研究了拖转期燃油计量阀接通时间和开度对轨压动态特性的影响,由此优化拖转期燃油泵的控制方法。研究了起动期燃油计量阀的开度和控制方法对轨压动态特性的影响。结果表明,所设计的高压泵燃油计量阀分阶段的控制策略可有效改善柴油机起动过程目标启喷压力的稳定性和跟随性,为提高起动性提供良好的喷射条件。

轮轨油污染黏着特性的三维数值分析

在油污染工况下,建立一个考虑轮轨表面粗糙度的三维轮轨黏着特性数值分析模型。应用Patir和Cheng提出的平均流量模型,以多重网格法和多重网格积分法作为数值计算的工具,得到轮轨间存在油介质时的液体、固体粗糙峰接触压力以及膜厚的分布规律,并研究列车速度以及轮轨表面粗糙度对轮轨间黏着特性的影响。研究结果表明:随着列车速度增加,轮轨间的黏着系数逐渐下降;随着轮轨表面粗糙度的增大,轮轨间的黏着系数逐渐增大。此外,从数值角度分析速度增大引起黏着系数下降和粗糙度增大所引起黏着系数上升的机理。

用有限元法计算罐车内轻油温度场

为了解决铁路罐车轻油上卸管路系统存在的气阻问题,通过分析罐车的几何特性,建立了油罐车内轻油温度场数学模型和求解边界条件,使用ANSYS有限元软件求解该数学模型。将油罐车内轻油温度场简化为二维非稳定传热问题。通过对轻油温度场一个运行周期的计算,既可求出在运行周期内某时刻轻油温度场的温度分布,也可以求出罐车内任意点在整个运行周期中的温度变化值。