Effects of ethylene-octene copolymer (POE) on the brittle to ductile transition of high-density polyethylene/POE blends

Three kinds of ethylene-octene copolymers (POE) were melt-blended with high-density polyethylene (PE-HD) in different proportions. Detailed characterizations were conducted to analyze their structural differences of POE and its effects in toughening PE-HD. The higher molecular weight POE can improve the toughness of PE-HD. 60:40 PE-HD/POE is elongated to break up to 700% while impact strength is 84.7 kJ/m² at −30°C, which is 21-fold of PE-HD. In the brittle to ductile transition (BDT) during impact, the fracture mechanism changes from the crazing mode to the shear yield-plastic deformation mode. The BDT temperature decreases as the POE molecular weight and its content increase. The interface strength in tension is estimated to access their effects. The Boltzmann-type models were successfully extended to describe the typical S-shaped curves in BDT of notched impact strength vs POE content or temperature. The supplementary decay model is suggested for the attenuation in toughening. Transition map in impact is proposed to select the use range of composition (c ) and temperature (T ) for high toughness. The curves are converted into 3D graph of T -c -impact strength for illustrating their coupling-separate effects, and further into the contour map of impact strength in T -c space for finding their partial equivalence.     

论四川盆地天然气勘探前景

中石油及其前身已在四川盆地从事天然气勘探开发工作50余年,截至2005年底累计探明天然气地质储量逾8400×10⁸m³,累计生产天然气超过2300×10⁸m³,年产量现已超过120×10⁸m³,已成为国内目前最大的产气区。对于该盆地进一步勘探前景如何的命题,从以下4个方面给予了论证：一是资源丰富、勘探成果持久不衰，近期仍有大发现；二是要辩证地认识盆地油气地质的复杂性，探索新规律，解放新领域；三是寻求地质认识和勘探技术进步是勘探突破的关键；四是继续以盆地两大地质体系（海相古隆起体系及陆相前陆盆地体系）和8套裂缝-孔隙性储集层（中上寒武统白云岩、石炭系白云岩、上二叠统长兴组生物礁白云岩、下三叠统飞仙关组鲕状白云岩、下三叠统嘉陵江组粒屑白云岩、中三叠统雷口坡组藻粒白云岩、上三叠统须家河组长石岩屑石英砂岩和中上侏罗统红层砂岩）为对象获取更多的天然气资源量及优质储量。据此得出结论：四川盆地天然气勘探前景是广阔的，但勘探难度会逐步加大。     

岩性指示曲线重构及其在储层预测中的应用

大牛地上古生界岩性气藏主要发育在三角洲分流河道沉积的下石盒子组、海陆交互沉积的山西组及以潮坪相沉积为主的太原组,储层是储集性能较差的致密砂岩,平均孔隙度小于10％,渗透率小于1×10-2μm2,储层单层厚度一般小于10 m,砂体横向连通性较差。由于低孔、低渗特征导致储层与围岩的波阻抗差异微弱,用地震资料进行储层预测困难。为此,针对大牛地石板太工区优质储层的岩性特征和测井响应特征进行了测井综合分析,利用对岩性粒度敏感的自然伽马曲线,以及对岩性粒度响应频率较低,且与波阻抗有较好对应关系的中子曲线重构了岩性指示曲线。岩性指示曲线不仅可以有效地识别优质砂体,划分不同岩性,为地震、测井信息结合的岩性反演建立桥梁,同时也为反演结果识别气层打下了基础。利用岩性指示曲线、波阻抗和电阻率曲线进行的地震、测井联合反演技术在石板太工区取得了较好的效果,同时,对石板太工区下石盒子组盒2段、山2段进行了储层和含气性预测,划分了有利含气区带,部署的2口开发井和1口探井有2口井见气,其中1口井获高产气流。     

吐哈盆地巴喀油田特低渗砂岩油层裂缝分布特征

巴喀油田中侏罗统砂岩属特低渗透裂缝 孔隙型储集层 ,平均渗透率为 0 .3× 10 - 3μm2 ;地下基质岩块孔隙度为7.4%,渗透率为 0 .16× 10 - 3μm2 。砂岩储集层发育的主要裂缝类型有构造层理缝、正向正交缝、斜向正交缝和羽裂等 ,裂缝宽度一般为 0 .3～ 3 .2mm ,纵向切深为 0 .1～ 0 .8m ,水平延伸长度为 0 .2～ 2 .1m。裂缝以半充填为主 ,其分布受岩性、层厚和构造位置的影响 ,纵向、横向均呈带状分布 ,被裂缝切割而成的基质岩块尺寸取决于裂缝频率 ,岩块长轴方向以北西西向为主 ,与构造轴向基本一致。图 3表 4参 8     

砂岩酸化中水化硅沉淀的影响因素分析

讨论了砂岩酸化中产生水化硅沉淀的反应机理。使高岭土与1.0%HF和多种配比的HCl HF在不同温度(20-90℃)反应不同时间(10-300分钟),用等离子吸收光谱法(ICP)测定酸液中可溶性硅的浓度(mg/L),取某时段测定值的减小量为该时段水化硅沉淀生成量,讨论了多种因素的影响,得到了如下结果和结论。反应温度越高,则高岭土与HF之间的反应越快,形成水化硅沉淀的时间越短,最终生成的沉淀量越大;在HF中加入HCl(使用土酸体系)、减小土酸中HF质量分数、加大土酸中HCl、HF质量分数比,均可使生成沉淀时间延后,使最终生成沉淀量减少。60℃时300分钟沉淀量,在1.0%HF、5.0%HCl 1.0%HF、9.0%HCl 1.0%HF中分别为482、321、201mg/L。提出了在酸化设计与施工中可以采取的6条简便易行的减少水化硅沉淀量的措施。图4表1参6。     

利用谱分解技术进行薄储层预测

采用短时窗离散傅里叶变换的频谱分解技术,实现了在频率域内通过调谐振幅的成像特征来研究储层横向变化规律的目标,最大限度地挖掘了地震资料主频至高频端的地震分辨能力。本文介绍了谱分解技术的基本原理、谱分解数据体的类型及其解释方法,充分利用谱分解得到的一系列单一频率的调谐振幅数据体研究辽河盆地东部凹陷西斜坡铁匠炉地区近源沉积砂砾岩储层,查清了该套储层沉积相带的平面分布和有效储层横向展布特征,预测结果已被钻井所证实。     

陆西凹陷包日温都断裂构造带岩性油藏研究

为寻找岩性油藏，应用波阻抗反演地震储层预测技术，对包日温都断裂构造带砂体展布情况进行了预测，发现并落实了2个岩性圈闭，由此认为，研究区北部是大型水下扇砂体与半深湖相暗色泥岩交汇之处，有利于形成岩性油藏，这一结论将对今后加强储层预测工作和寻找有利砂体提供借鉴。     

Dynamic crack propagation with cohesive elements: a methodology to address mesh dependency

In this paper, two brittle fracture problems are numerically simulated: the failure of a ceramic ring under centrifugal loading and crack branching in a PMMA strip. A three‐dimensional finite element package in which cohesive elements are dynamically inserted has been developed. The cohesive elements' strength is chosen to follow a modified weakest link Weibull distribution. The probability of introducing a weak cohesive element is set to increase with the cohesive element size. This reflects the physically based effect according to which larger elements are more likely to contain defects. The calculations illustrate how the area dependence of the Weibull model can be used to effectively address mesh dependency. On the other hand, regular Weibull distributions have failed to reduce mesh dependency for the examples shown in this paper. The ceramic ring calculations revealed that two distinct phenomena appear depending on the magnitude of the Weibull modulus. For low Weibull modulus, the fragmentation of the ring is dominated by heterogeneities. Whereas many cracks were generated, few of them could propagate to the outer surface. Monte Carlo simulations revealed that for highly heterogeneous rings, the number of small fragments was large and that few large fragments were generated. For high Weibull modulus, signifying that the ring is close to being homogeneous, the fragmentation process was very different. Monte Carlo simulations highlighted that a larger number of large fragments are generated due to crack branching. Copyright © 2003 John Wiley & Sons, Ltd.     

实验室条件下聚能射孔损害带研究

在实验室条件下对贝雷砂岩进行射孔试验,并分别对射孔后的靶体进行酸化、压裂工艺处理,利用核磁共振和工业X-CT技术分别对未射孔的靶体、射孔后的靶体、射孔后酸化的靶体、射孔后压裂的靶体进行测试.定量分析了射孔对砂岩靶体的损害及酸化、压裂对射孔损害的解除作用.     

THE FRACTURE MECHANISM OF 475°C EMBRITTLEMENT IN A DUPLEX STAINLESS STEEL

The mechanism of “475°C embrittlement” of a duplex stainless steel was investigated using finite element modelling of the stress distribution at brittle fracture initiation. Brittle fracture initiated at a critical shear stress, which increased with ferrite hardness. The fracture stress was affected by the duplex microstructure. Fracture was nucleated by deformation twins, which were identified using electron back-scatter diffraction. The ductile-to-brittle fracture transition was sensitive to age-hardening and could be described simply by the effect of age-hardening and test temperature on the yield stress.