应用数理分析法确定致密油压裂水平井产能影响因素主次

水平井大规模压裂已成为提高致密油储层单井产能、保证动用效果的有效技术手段,通过数值模拟方法确定地层渗透率、裂缝长度、裂缝数量和导流数值对产能影响主次,是提高压裂优化设计准确性进而提高产能的保障。由于要进行四种参数、多参数水平值进行正交对比工作量大,本文使用直观分析法和方差分析法进行对比,大幅度减少了数值模拟的工作量,并确定地层渗透率、裂缝长度、裂缝数量和导流数值这4个因素对产能的影响依次减小。     

燃爆诱导压裂油井产能计算模型

油井燃爆压裂或燃爆诱导水力压裂在低渗油田开发中地位越来越重要,而对近井地带多裂缝系统的产能研究较少,难以支撑压裂参数的定量优化。针对该问题,基于带有多裂缝单井物理模型,利用油藏渗流理论和节点系统分析的方法,建立了燃爆诱导压裂油井产能计算模型,并分析了不同裂缝长度和裂缝条数对油井产能的影响。结果表明,油井产能随着裂缝长度近似线性增加,随着裂缝条数的增加也逐步增加,但超过5条增加幅度减缓。研究成果对燃爆压裂设计和压后产能评测具有一定的指导作用。     

基于FracproPT软件模拟长8层压裂分析及优化

FracproPT压裂模拟软件可以对已进行过压裂的油井的进行分析和优化,本文采用FracproPT软件分析姬塬油田长8层的已压裂井数据,得出长8层中,裂缝优化长度为96～120 m,铺砂浓度5～7 kg/m2左右能够满足导流能力的需要,并根据不同裂缝长度和不同的铺砂浓度做模拟加砂,为压裂施工提供参考依据.     

小10-16区块整体压裂参数优化

大港油田小10-16区块为低孔、低渗型油藏,根据该区块压裂改造的实际需要,建立了反九点法井网条件下考虑启动压力梯度的三维两相油藏数值模拟模型,研究了裂缝半长和裂缝导流能力对油井产量、累计产油量的影响,优化了裂缝参数.研究结果表明,对于该区块的低渗透油藏,相对于裂缝长度,导流能力不是影响油井产量的主要因素.综合考虑裂缝导流能力取25,裂缝穿透比取0.4左右,裂缝半径90～95m为最佳.     

径向井压裂产能水电模拟实验研究

径向井压裂拥有成本低,增产效果好的优势,在小规模油藏的运用越来越多。基于水电相似原理,利用水电模拟实验,研究了径向井压裂产能,分析了不同裂缝间距和不同裂缝长度对于径向井压裂产能的影响和不同裂缝间距下的等势线。通过对实验内容分析得出:裂缝间距越大,径向井的压裂效果越好,其控制的泄油面积也越大,有利于提高油藏采收率;随着裂缝间距的增加,产能的增加幅度逐渐变小;裂缝的长度越大,径向井压裂后的产能越大;对比裂缝长度和裂缝间距对于径向井压裂产能的影响,发现裂缝长度的增加更能提高压后产能。基于上述研究,可以为现场的径向井压裂产能研究提供一定的理论支撑。     

特低渗透油藏压裂井产能分析

低渗透储层由于渗透率比较低,往往通过水力压裂提高单井产能,因此,压裂井产能的评价对低渗透油田的开发尤为重要。基于低速非线性渗流新模型,建立了低渗透无限导流能力和有限导流能力垂直裂缝井产能公式,并与基于达西模型和拟启动压力梯度模型的裂缝井产能公式进行了对比分析。为便于工程应用,用等效直井产能公式表示有限导流能力裂缝的产能,并对影响其产能的参数进行了分析,对低渗透油田的开发具有重要的意义。     

分段压裂水平井产能影响因素分析

建立了分段压裂水平井不稳渗流数学模型。模型采用有限元非结构化网格进行剖分,基于离散裂缝模型的思想对水力裂缝进行降维处理,使用伽辽金有限元方法进行求解,最后通过编程计算绘制了产能动态曲线,并对影响曲线的因素进行分析。研究结果表明,裂缝的导流能力在分段压裂水平井生产前期对产能有明显影响。导流能力越大,压裂水平井的日产量就越高。随着裂缝导流能的增大,井的增产幅度不断降低。裂缝条数越大,压裂水平井的产量越大。随着裂缝间距减小,缝间干扰增强,反而产量降低。这对深入认识分段压裂水平井的生产动态具有重要意义。     

楔形裂缝多段压裂水平井数值模拟研究

多段压裂水平井模拟过程中大多采用与实际不符的恒定缝宽假设,压裂井产能预测结果不精确。利用商业数值模拟软件,对裂缝形态进行了近似实际的描述。采用楔形裂缝的等效形式和等导流能力方法,分析了启动压力梯度和介质变形对多段压裂水平井产能的影响,并且对比了楔形裂缝和矩形裂缝多段压裂水平井的产量。结果表明:在其他条件一样的情况下,多段压裂水平井产量随着启动压力梯度增大和介质变形程度增强而降低;且楔形裂缝多段压裂水平井产量比矩形裂缝多段压裂水平井产量低,二者相对误差随着启动压力梯度增大呈现先增大后降低的趋势,随着介质变形程度的降低呈现逐渐降低的趋势,但总体上相差幅度不大。该研究方法为多段压裂水平井产能准确预测及裂缝参数优化提供了借鉴。     

压裂水平井产能影响因素研究

本文充分调研了前人的研究成果,经过分析、综合,总结出了影响压裂水平井产能的七大因素:测试时间,污染系数,裂缝穿透率,裂缝条数,井筒长度,裂缝角度和裂缝导流能力。研究表明,测试时间的长短直接影响不同的流动阶段;污染系数越大,产能越低;裂缝穿透率、裂缝条数和导流能力与产能之间存在一个最优值;水平井筒长度越大,压裂水平井的产量越大;此外,应尽可能使裂缝垂直于水平井筒,以提高压裂效果。     

重复压裂井产能影响因素及产能预测——以富县大东沟地区为例

目前富县大东沟区采出程度很高,为保持稳产需要对部分低产低效井进行重复改造,恢复其裂缝导流能力,提高二次改造成功率,达到增产效果。对富县大东沟的单井产能影响因素进行分析,确定影响重复压裂井产能的关键因素,为后期选井提供理论依据。通过分析现有重复压裂井储层、施工参数、累产油和日产油的关系,用灰色关联法对产能影响因素进行排序,并建立产能预测模型,快速优选潜力井并对产能进行预测。     

空分装置换热器开孔接管开裂失效事故的应力分析

基于管道有限元基本理论,根据相关规范,结合一空分装置换热器铝管道断裂失效实例,分析了铝管道支管与主管开孔和换热器封头开孔焊接处的局部应力状态.对失效管道进行安全性评定,给出切实可行的整改措施,并就该类管道的分析方法和工程运用给出建议.     

Fracture behavior of robocast HA/β-TCP scaffolds studied by X-ray tomography and finite element modeling

Hydroxyapatite (HA)/α-tricalcium phosphate (α-TCP) cellular composites were fabricated by robocasting. Polymeric beads were intentionally added into the solid rods of the samples to generate artificial defects in order to characterize their influence on the fracture behavior in uniaxial compression. The samples were characterized by X-ray tomography at two resolutions to observe their architectural and microstructural features, for the latter using a local tomography mode. Then ex situ compression tests were performed to follow the deformation of the sample at low resolution by tomography. The images showed a brittle-like behavior with the propagation of a main crack parallel to the compression direction. Finally, the high-resolution images of the initial sample were processed to create a finite element (FE) model of the whole sample and including the presence of artificial defects in the struts. The ex situ test and the modeling show the influence of the artificial defects on the crack initiation.     

轮胎橡胶材料裂纹开裂方向的研究

用断裂力学的方法分析了二维板状试样轮胎橡胶材料的裂纹扩展特性。建立了二维轮胎橡胶材料的有限元模型，用应变能密度这个参数模拟了试样承受单向拉伸时裂纹的扩展方向。模型中考虑了橡胶材料的非线性和不可压缩性，以及断裂奇异单元的收敛性。通过有限元分析，得出了橡胶材料单向拉伸时的裂纹扩展方向，并将计算结果与试验结果进行比较，两者吻合得很好。实验证明：应变能密度是解决橡胶断裂问题的一个有效参数。     

Mode I Fracture Load Predictions of Adhesive T-joints

This paper presents fracture data and a finite element analysis for adhesive T-joints, It is shown that fracture loads of T-joints, bonded with two different structural epoxies and subjected to either tensile loading or three-point bending, can be predicted using a fracture mechanics approach. Fracture loads were predicted by calculating the applied energy release rate, G, using finite element methods, and comparing that with a critical value, G_c, determined experimentally using double-cantilever-beam specimens. By recording the failure sequence of the bondline with a video camera attached to a microscope, it was seen that subcritical crack propagation took place prior to final fracture of the bondline. Accounting for the observed subcritical crack propagation in the finite element analysis gave a good agreement between the actual and the calculated fracture loads.     

Effect of FRP Pipe Scaling on its Adhesive Bonding Strength

Polymer-based materials are emerging as a potential substitute for metallic structures in the oil and gas industry. In this context, fiber-reinforced polymer (FRP) piping is one promising application. An important area of the research pertaining to FRP piping is the connection of pipe sections. Challenges associated with the joining of FRP tubular sections are often considerable, which limits more widespread industrial application. Adhesive bonding is emerging as a promising technique to join tubular FRP structures. The ability to maintain undamaged fiber architecture is a major advantage of adhesive bonding technology. In the present study a strength-of-materials as well as fracture mechanics approach was employed in conjunction with the finite element method to investigate the scaling effects on adhesively bonded tubular sections. It was found that the scaling effects in joined FRP pipe may be significant. For certain composite material configurations the analysis indicated a shift of the region of failure from the pipe structure to pure adhesive (cohesive) failure with increasing pipe diameter.     

单纤维拉拔过程数值模拟

介绍了纤维复合材料作为具有强烈的结构特性的多相体材料,其力学性能及损伤破坏规律不仅取决于各组分材料性能,同时也取决于细观结构特征.单纤维拔出测试方法作为增强纤维表面改性效果和评价复合材料界面质量的重要手段一直受到人们的极大重视.利用有限元软件,对纤维拉拔过程进行了数值模拟,分别得到不同时问下的应力和位移图及纤维拉拔时的应力状态及其对界面性能的影响.     

Cohesive Zone Model Characterization of the Adhesive Hysol EA-9394

Abstract

The cohesive zone model approach is attractive for the analysis of failure of adhesively bonded structures. While the numerical implementation of cohesive elements has been well established, there remains a lack of cohesive material data. The present paper contributes to efforts to fill this void. An investigation of crack growth in the widely used structural adhesive Hysol EA-9394 is presented, and the adhesive is characterized by a cohesive zone law. Crack growth experiments were performed on specimens consisting of aluminum adherends bonded by use of the adhesive. Measurements of the surface topography leading reconstruction of fracture processes indicate that plastic deformation is absent during fracture. Thus, the cohesive zone law can directly be determined from the energy release rate and the material separation measured at the initial crack tip. The cohesive zone law is then applied in finite element model to predict crack growth. The predicted strain fields during crack growth are well matched to those obtained by digital image correlation measurements. An independent set of crack growth experiments was performed, and finite element models based on the cohesive law were used to predict the outcome of these experiments. Again good agreement between simulation and experiment was obtained. The results give confidence that the cohesive zone model parameters are transferable to the analysis of structures bonded with the adhesive Hysol EA-9394 in general. A comparison of the cohesive zone law for Hysol EA-9394 demonstrates that this adhesive possesses high strength and moderate toughness. Limits to the transferability regime are discussed.     

拓扑互锁易碎复合材料隔水罩的设计与试验研究

导弹发射筒盖与导弹弹体之间的隔水罩必须具备足够的强度和刚度以抵抗海水进筒时的冲击力和进筒后的压力,而在导弹射出筒前的瞬间隔水罩必须能够在外加触发条件下自行碎裂,使导弹顺利通过。为实现这一工作机制,采用拓扑互锁原理和有限元方法设计了拓扑互锁易碎复合材料隔水罩,并根据相似理论制作了隔水罩模型。试验表明,所设计的拓扑互锁结构满足承压要求;当在反向施加一较小冲击力时,承载层各子构件的拓扑互锁约束被解除,互锁功能消失,使结构完成触发碎裂。有限元分析结果与试验结果基本吻合。     

Fracture Toughness of a Crystalline Silicon Carbide Fiber (Tyranno-SA3®)

The fracture toughness of a crystalline silicon carbide fiber, Tyranno-SA^®, was determined by introducing an artificial notch directly into the fiber test specimens using a focused-ion (Ga⁺) beam. The relation between fracture strength and notch size was determined experimentally, while the relation among the notch size, fiber diameter, applied stress at infinity, and stress intensity factor was analyzed by the finite element method. By applying the analyzed result to the experimental results, the fracture toughness of the fiber was determined to be     .