Physical and Acoustic Properties of Gas-bearing Sediments in Jinhae Bay,the South Sea of Korea

High-resolution seismic survey and sediment core sampling were conducted to investigate acoustic characteristics of gas-bearing sediments in Jinhae Bay, the southeast of Korea. The sediment in Jinhae Bay is mostly homogenous mud deposited after the Holocene transgression. Along with the 410 km of chirp seismic profiling, five piston core samples were collected on the track lines.

Gassy sediments are common and occur widely in the bay. Core samples were analyzed for sediment texture, physical properties (porosity, water content, bulk density, and grain density), acoustic properties (compressional wave velocity and attenuation), and electrical resistivity. X-radiograph image analysis was also performed to observe the shape of degassing cracks. There is no significant downcore variation on physical and sediment textures regardless of existence of gas bubbles. However, compressional wave velocity dramatically decreases from average 1480 to 1380～739 m/s for the cores that penetrate the gas-bearing zones. This is probably due to degassying cracks that developed by escaping gases and free gas bubbles that are still trapped in the cores. Electrical resistivity is the only geotechnical property that increases in the gas-bearing zone where compressional wave velocity abruptly decreases. This indicates the possibility of using both electrical resistivity as an index variable as well as to compressional wave velocity to identify gassy sediment microstructure because there are little changes in texture and composition of sediment.     

裂隙网络管道模型弥散试验

为了探求不同裂隙几何参数对裂隙网络溶质运移的影响,基于离散裂隙网络思想和优势流、沟槽流理论,建立裂隙管道网络概念模型,搭建不同管径、不同连通方式的管道网络试验装置,进行渗流和溶质运移实验。运用应用广泛的模拟软件CHEMFLO-2000建立等效多孔介质模型,拟合不同几何参数下等效弥散度,定量刻画不同管道网络几何参数对溶质运移的影响,讨论了不同管径、连通方式等与等效弥散度之间的关系。通过进一步分析得出:在连通方式相同的情况下,不同管径的管道网络等效弥散度存在差异,但是差异不大;溶质在小管径中的穿透时间短于大管径,穿透曲线缓和程度相差不大;管道网络连通方式越复杂,其等效弥散度越大、对溶质运移的影响越大、穿透曲线越缓和、路径越长,等效弥散度越大;用这种等效弥散度的方法表征管道网络对溶质运移的影响,与多孔介质弥散度具有相似性;管道数目、管道面数目与等效弥散度成正相关关系,且等效弥散度随尺度的增大而增加。     

廊固凹陷河西务构造带沙四上亚段有效储层成因机制

中深层有效储层成因机制一直是中深层油气勘探备受关注的内容。综合运用岩心观察、薄片鉴定、物性分析及流体包裹体分析等技术手段,研究了廊固凹陷河西务构造带沙四上亚段储层岩石学特征、储集特征及成岩作用特征,并在有效储层物性下限计算的基础上,分析了有效储层物性控制因素,总结了有效储层成因机制,建立了有效储层成因模式。研究表明：廊固凹陷河西务构造带沙四上亚段储层以岩屑质长石砂岩为主,含少量长石质岩屑砂岩,成分成熟度中等,结构成熟度高;压实作用较强,胶结作用南北差异性明显,溶解作用弱;储层储集空间以原生孔隙为主,含少量的粒内溶孔及粒间溶扩孔隙,孔渗相关性好。储层胶结物含量、分选系数、沉积微相及地层压力是廊固凹陷河西务构造带沙四上亚段有效储层形成的主要控制因素。辫状河三角洲前缘分支河道沉积环境中杂基含量少、分选好、碳酸盐岩屑含量低的细砂岩、中粗砂岩及含砾砂岩是沙四上亚段有效储层形成的有利物质基础。早期地层超压,抑制压实作用,保护原生孔隙;早期油气充注,抑制胶结作用与压实作用,保护孔隙空间。二者共同作用,是有效储层形成的主要原因。溶解作用少量增孔,颗粒边缘形成的早期石英加大抑制压实,对有效储层的形成起辅助作用。     

沁水盆地南部煤中矿物赋存特征及其对煤储层物性的影响

煤中矿物可以影响煤储层物性,进而影响煤层气的开发。运用光学显微镜和扫描电镜研究沁水盆地南部煤中矿物的种类、含量和赋存特征。基于煤储层的平衡水等温吸附实验和压汞实验,研究了沁南地区煤中矿物对煤储层吸附性能和孔渗性能的影响。结果表明,柿庄北区块3号和15号煤平均矿物含量分别为10.68%和12.81%,且15号煤硫化物含量较高。扫描电镜下可观察到充填煤储层胞腔孔、粒间孔隙和微裂隙的方解石、黄铁矿、高岭石和石英。孔隙度和渗透率以及兰氏体积和煤中大中孔比例均随灰分产率的增加而减小,表明煤中矿物的存在会降低煤储层的吸附性能和孔渗性能,煤储层中矿物充填主要影响煤的大中孔和裂隙,影响煤层气在割理和裂隙中的渗流,导致孔隙度和渗透率下降,而少量粘土矿物充填微孔可导致煤的吸附性能下降。     

罗子沟盆地有机质热演化对砂岩物性的改造作用

基于岩石薄片观察、压汞分析、扫描电镜和X衍射分析等方法对罗子沟盆地大砬子组砂岩物性特征进行了定性-定量研究。结果表明：罗子沟盆地大砬子组砂岩成分成熟度和结构成熟度低,以岩屑长石砂岩和长石砂岩为主;岩石孔隙度高,孔隙度主要为16.2%~26.4%,次生孔隙占总孔隙度面孔率的88%,但总体渗透率极低,渗透率主要分布在（0.13~1.68）×10^-3 μm²,为高孔特低渗的物性特征。有机元素分析、色谱分析、岩石热解及显微组分镜检分析表明,罗子沟盆地大砬子组泥页岩中有机质在热演化过程中产生大量有机酸,有机酸对砂岩中长石等矿物的溶蚀作用是次生孔隙发育的主要原因,但有机酸溶蚀产生的次生矿物在一定程度上堵塞了孔隙喉道。因此,研究区砂岩形成高孔特低渗的物性特征。     

滑坡-碎屑流物理模型试验及运动机制探讨

滑坡-碎屑流由于高速、远程的特点常常引发灾难性事故,其复杂的运动机制导致预测致灾范围非常困难。通过开展室内模型试验,研究了碎屑粒径、滑床糙率和挑坎对运动特性的影响。试验结果发现,滑坡碎屑运动距离受控于前端碎屑,且随着碎屑的粒径增大而增加,增加滑床糙率、挑坎均可使碎屑的运动距离减小。在前人研究成果的基础上结合碎屑材料的力学特性探讨了滑坡-碎屑流出现流态化的原因和高速远程机制,即高速运动中颗粒间的作用力远小于完整岩体,因此颗粒间的“黏聚力”不能维持滑坡体的整体性,同时致使滑坡体与滑床接触的过程中传递至滑坡体内部的摩阻力减少,从而导致碎屑滑坡的远程结果。     

基于居民个体的城市虚-实空间关联指标研究——以南京市为例

信息技术对城市空间结构的影响一直是地理学关注的话题。随着信息技术的革新及其在社会生活中的普及应用,地理学者开始将研究视角从空间转向网络用户。引入信息科学领域的“地理关联”概念,通过南京居民问卷调查获得973个样本数据,采用结构方程模型分析,尝试从微观个体角度探索基于居民个体的虚-实空间的关联指标。结果发现：居民信息化程度、居民信息化认知、居民信息化习惯、居民流动性是微观层面虚-实空间关联的主要指标;居民流动性是空间关联最重要的衡量指标,其次是居民信息化认知、居民信息化习惯、居民信息化程度;工作地是最能展示网络空间与实体空间紧密关联的场所类型。     

车辆碾压对沙质草原表土物理力学性质的影响

通过野外现场调查、载荷试验、轻型圆锥动力触探、车辆碾压原状草地观测试验及室内试验方法,对呼伦贝尔沙质草原不同碾压程度表层沙土物理力学性质及变形和剪切破坏特征进行研究。结果表明:碾压使上软下硬高压缩性的原状表层沙土因应力集中产生振动密实沉降、塑性变形,直接破坏表土层原状结构。碾压程度越大,沙土密实度越高、抗剪强度越大、承载力越高。碾压形成上硬下软土层,因强度不足发生整体剪切破坏,塑性变形区的沙土在重复荷载作用下产生振动蠕变及砂土液化,使土层强度、稳定性显著降低。车辆碾压可直接或间接破坏沙质草原表层沙土,加剧土层破口形成及扩大,加速草原沙漠化。     

The use of live vegetation in geomorphological experiments: how to create optimal growing conditions

There has been increasing use of live vegetation in laboratory experiments, in particular in fluvial geomorphology. The results from these studies have provided useful insight into the role that vegetation plays in impacting and modifying geomorphic systems. However there has been little published on the seed preparation techniques and vegetation growing conditions required for use in these experiments. This commentary presents results from a series of experiments investigating these factors using Medicago sativa and Avena Sativa, with the aim of highlighting the optimal growing conditions found to provide a starting point for researchers interested in implementing these techniques. Copyright © 2014 John Wiley & Sons, Ltd.     

Perturbation of nuclear decay rates during the solar flare of 2006 December 13

Recently, correlations have been reported between fluctuations in nuclear decay rates and Earth–Sun distance, which suggest that nuclear decay rates may be affected by solar activity. In this paper, we report the detection of a significant decrease in the decay of ⁵⁴Mn during the solar flare of 2006 December 13, whose X-rays were first recorded at 02:37 UT (21:37 EST on 2006 December 12). Our detector was a 1 μCi sample of ⁵⁴Mn, whose decay rate exhibited a dip coincident in time with spikes in both the X-ray and subsequent charged particle fluxes recorded by the Geostationary Operational Environmental Satellites (GOES). A secondary peak in the X-ray and proton fluxes on December 17 at 12:40 EST was also accompanied by a coincident dip in the ⁵⁴Mn decay rate. These observations support the claim by Jenkins et al. that nuclear decay rates may vary with Earth–Sun distance.