非常规油气储集孔隙多尺度连通性的定量显微CT研究

非常规油气储集孔隙结构复杂多样,以纳米级孔喉系统为主,局部发育毫米-微米级孔隙和裂隙。孔、裂隙大小、形态及三维连通性等微观结构特征对油气赋存状态、运移方式、渗流特征等地质问题研究具有重要意义。常规方法无法实现微纳孔隙多尺度三维结构及连通性分析。本文采用同步辐射多能CT技术,结合数据约束模型(DCM)方法对非常规油气储集微纳孔、裂隙研究,可实现多尺度三维可视化表征,进一步获得孔、裂隙体积统计分布及其三维连通结构等信息。基于上海光源显微CT实验平台,针对碳酸盐岩及陆相页岩两种样品,成功获得了孔、裂隙三维结构以及统计分布、三维连通结构等定量信息。实验结果表明,该方法有望成为非常规油气储集研究强有力的手段。     

螺旋CT机的维护和检修探讨

本文根据现阶段医院螺旋CT所处的环境及使用特点,对其维护检修工作按优先级分三个方面依次进行论述:首先强调加强预防性维护的重要性并综述相关内容和具体方法;随后阐述对现场即时维修的要求和应做好的准备工作;最后在分析若干实际故障解决案例的基础上总结了停机检修的经验和应注意的原则.     

The structure of methane gas hydrate bearing sediments from the Krishna-Godavari Basin as seen from Micro-CT scanning

The Indian National Gas Hydrate Program (NGHP) Expedition 1, of 2006, cored through several methane gas hydrate deposits on the continental shelf around the coast of India. The pressure coring techniques utilized during the expedition (HYACINTH and PCS) enabled recovery of gas hydrate bearing, fine-grained, sediment cores to the surface. After initial characterization core sections were rapidly depressurized and submerged in liquid nitrogen, preserving the structure and form of the hydrate within the host sediment. Once on shore, high resolution X-ray CT scanning was employed to obtain detailed three-dimensional images of the internal structure of the gas hydrate. Using a resolution of 80 μm the detailed structure of the hydrate veins present in each core could be observed, and allowed for an in depth analysis of orientation, width and persistence of each vein. Hydrate saturation estimates could also be made and saturations of 20-30% were found to be the average across the core section with some portions showing highs of almost 60% saturation. The majority of hydrate veins in each core section were found to be orientated between 50 and 80° to the horizontal. Analysis of the strikes of the veins suggested a slight preferential orientation in individual sample sections, although correlation between individual sections was not possible due to the initial orientation of the sections being lost during the sampling stage. The preferred vein orientation within sample sections coupled with several geometric features identified in individual veins, suggest that hydraulic fracturing by upward advecting pore fluids is the main formation mechanism for the veined hydrate deposits in the K-G Basin.     

SOMATOM PLUS全身CTX线管旋转阳极及其控制电路的工作原理及维修

Ｘ线管是ＣＴ中最重要、最昂贵同时也是最易损坏的部件之一，而旋转阳级又是Ｘ线管中故障率最高的部件。因此正确判断Ｘ线管旋转阳级的故障显得尤为重要。如判断失误，将会给用户造成巨大的经济损失。本文阐述西门子ＳｏｍａｔｏｍＰｌｕｓ全身ＣＴ的旋转阳极及其控制电路的工作原理及维修方法，并以流程图的形式给出了步骤。     

Aluminosilicate cementation of saprolites,grits and silcretes in Western Australia

Amorphous to poorly crystalline aluminosilicates have been found as cementing agents within saprolites, hardpans and silcretes, particularly in granitic terrains in the Yilgarn Block, Western Australia. The cements range mineralogically from siliceous allophane to a kaolinite‐opal‐CT assemblage probably derived from the allophane. The allophane is non‐crystalline, with no distinctive X‐ray or electron diffraction patterns, and has close optical similarities to opaline silica. It is characterised by Al/Si ratios of 0.35–1.0, with small amounts of adsorbed iron and titanium. It occurs as colloform void and vein fillings, and permeating the kaolinitic matrix of saprolites. The kaolinite and opal‐CT have a similar occurrence, with the kaolinite oriented parallel to colloform and related banding. The aluminosilicate cements are found in saprolite, usually in the upper zones, and in overlying grits and silcretes. At Gabbin, in the central Yilgarn, the grits are up to 10 m thick and have aluminosilicate as the only cement. Although very hard when in situ, the grits tend to disaggregate on exposure and rarely, if ever, crop out. In profiles exposed in breakaways of the Barr‐Smith Range in the northern Yilgarn, the saprolite is overlain by silcretes with a quartz‐anatase‐zircon assemblage as cementing matrix, in turn overlain by alumino‐silicate‐cemented grits. The contact is gradational, and most silcretes and grits contain both types of cement, with the aluminosilicate increasing in abundance upwards. Kaolinitic spherules in sand plains are possibly derived from similar aluminosilicates.     

井中地震CT观测系统研究

井中地震CT具有高精度、高分辨率、接近探测目标等优点,在各类工程中得到较多应用。在震源确定情况下,地震数据的质量主要取决于观测系统的合理设计。本文通过理论模型正演得到相应的观测数据并进行CT成像反演,阐述了观测系统中射线角度、射线密度等因素对CT成像结果的影响。将研究成果应用于工程实际,取得满意效果。     

冲击荷载作用下混凝土破坏强度的确定及CT验证

从细观结构出发,把混凝土看作由骨料、界面和砂浆组成的非均质复合材料,建立随机骨料模型,应用损伤塑性本构,对试件进行了冲击荷载作用下的数值模拟,通过施加不同的加载方式,研究材料的损伤破坏过程,最终以位移加载得出荷载-位移曲线的峰值强度作为细观混凝土试样的破坏强度.通过对混凝土进行冲击荷载作用下的实时CT扫描,得出试件的荷载位移曲线及各个应力阶段的CT图像,发现数值模拟所得混凝土强度及破坏过程与CT观测到的结果有较好的相似性.结果表明,利用该方法研究混凝土在冲击荷载作用下的损伤破坏过程是合适的,以荷载-位移曲线的峰值点作为混凝土破坏强度点是合理的.     

解析法图像重建中的理想斜变滤波器的进一步研究(英文)

理想斜变滤波器是一种被傅里叶逆变换定义的广义函数。设计理想斜变滤波器的实用数字滤波器是最重要的任务之一。推导了理想斜变滤波器的单位冲激响应的公式。提出了两种实用数字滤波器的设计模式:连续模式和离散模式。分析了3种已经存在的实用滤波器,设计了2种新的实用滤波器。通过一个仿真实验,比较了这5种滤波器。总的来说,以离散模式设计的离散方法优于以连续模式设计的连续方法。对于2种离散方法来说,无限长离散方法优于自适应长度离散方法,它们均可以得到较好的重建质量。对于3种连续方法而言,线性方法是最好的,可以重建出工程可用的CT图像,而常数方法和抛物线方法不能重建出可用的CT图像。     

碳纤维复合材料气瓶的CT检测实验研究

目前国内碳纤维复合材料气瓶的定期检验对于内部缺陷还没有成熟的无损检测方法,射线检测可以对内部缺陷进行定性检测,CT检测技术可实现缺陷的精确定位和定量。针对某型号呼吸器用碳纤维复合材料气瓶的结构特点,依据有关定期检验标准,制作各种缺陷,开展CT检测实验研究。结果表明该技术对表面缺陷和纤维层内部缺陷都有很好的检出效果。以厚度2姗的铝内胆为基础,对缺陷的位置和深度进行了估算。     

声波CT在基桩检测及桩基勘测中的应用

从实践的角度介绍声波层析成像的原理、数据采集与处理方法。为保证反演精度,提高原始数据质量,特别强调慎重选择震源、记录仪器、传感器,以及合理选择采集参数与成像参数,并通过实例介绍声波CT在基桩检测及桩基础勘测中的应用。