煤层中流体地震可探测性的模拟分析

作为一种典型的强阻抗差低阻抗薄层,煤层中孔隙含流体时是否会引起地震反射产生明显的异常是回答地震检测流体是否可行的根本.为此,本文针对强阻抗差薄层模型,基于Biot双相介质理论,通过弹性波有限差分法数值模拟,与各向同性单相介质假设的煤层反射对比,探讨了反射复合波受煤层孔隙度及流体性质变化的影响程度.模拟分析发现：由于薄层孔隙度和孔隙流体属性的变化在Biot理论中表现为纵波速度的变化,PP波反射AVO（Amplitude Versus Offset,振幅随偏移距变化）特征对薄层是否含流体相对敏感;综合使用PP与PS波对比有利于薄层中流体的预测;孔隙度一定时,PP波反射振幅随着含气饱和度的增加而增大;受薄层调谐作用的影响,孔隙和流体变化对煤层反射的频谱特征影响不大,近似于单相介质时的情况.

     

Experimental investigation on seismic behavior of single piles in sandy soil

This paper describes a quasi-static test program featuring lateral cyclic loading on single piles in sandy soil. The tests were conducted on 18 aluminum model piles with different cross sections and lateral load eccentricity ratios, e/d, (e is the lateral load eccentricity and d is the diameter of pile) of 0, 4 and 8, embedded in sand with a relative density of 30% and 70%. The experimental results include lateral load-displacement hysteresis loops, skeleton curves and energy dissipation curves. Lateral capacity, ductility and energy dissipation capacity of single piles under seismic load were evaluated in detail. The lateral capacities and the energy dissipation capacity of piles in dense sand were much higher than in loose sand. When embedded in loose sand, the maximum lateral load and the maximum lateral displacement of piles increased as e/d increased. On the contrary, when embedded in dense sand, the maximum lateral load of piles decreased as e/d increased. Piles with a higher load eccentricity ratio experienced higher energy dissipation capacity than piles with e/d of 0 in both dense and loose sand. At a given level of displacement, piles with circular cross sections provided the best energy dissipation capacity in both loose and dense sand.     

利用单渗砂层能量厚度研究有利沉积微相及其含油有利区的方法

针对鄂尔多斯盆地陕北斜坡中部特低渗透储层识别主体骨架砂体微相带及筛选含油有利区工作,提出利用单渗砂层能量厚度控制划分最为有利的沉积微相带。利用多种测井响应提取单渗砂层沉积能量及其能量厚度信息,使其曲线幅度、厚度、形状、接触关系、次级形态等特征和数据大小能够集中反映相对高渗的单渗砂层最大沉积能量及厚度变化,确认出三角洲前缘水下分流河道微相及其河道叠置型河口坝微相骨架砂体的发育、规模及分布范围,有效地克服了层段中几个成因相近薄砂层或砂泥互层中砂层累加厚度识别和划分主体骨架砂体微相带的失误。通过该区目的层段自然电位、自然伽马、密度、中子、声波、电阻率测井曲线和岩性、物性及其能量厚度统计,建立起单渗砂层能量厚度下限标准及夹层扣除标准,在该区长4+511特低渗透储层中提取单渗砂层及其沉积能量信息,控制划分出有利沉积微相带及其骨架砂体分布,预测和筛选出不同类型相对高渗高产含油有利区,它们不同程度勾画出河道主体带油藏与南西部华池油藏连片延伸趋势、形态和特征,为该区特低渗透油田增储上产提供有利目标和重点层位及井区。     

Do river deltas in east India retreat? A case of the Krishna Delta

The construction of multiple dams and barrages in many Indian River basins over the last few decades significantly reduced river flow to the sea and affected the sediment regime. More reservoir construction is planned through the proposed National River Linking Project (NRLP), which will transfer massive amounts of water from the North to the South of India. The impacts of these developments on fertile and ecologically sensitive deltaic environments are poorly understood and quantified at present. In this paper an attempt is made to identify, locate and quantify coastal erosion and deposition processes in one of the major river basins in India—the Krishna—using a time series of Landsat images for 1977, 1990 and 2001 with a spatial resolution ranging from 57.0 m to 28.5 m. The dynamics of these processes are analyzed together with the time series of river flow, sediment discharge and sediment storage in the basin. Comparisons are made with similar processes identified and quantified earlier in the delta of a neighboring similarly large river basin—the Godavari. The results suggest that coastal erosion in the Krishna Delta progressed over the last 25 years at the average rate of 77.6 ha yr^− 1, dominating the entire delta coastline and exceeding the deposition rate threefold. The retreat of the Krishna Delta may be explained primarily by the reduced river inflow to the delta (which is three times less at present than 50 years ago) and the associated reduction of sediment load. Both are invariably related to upstream reservoir storage development.     

Treatment of Hydrodynamic Loading for Random Sea State

- In order to employ cost effective frequency domain analysis for off-shore structures treatment of hydrodynamic loading is essential. Drag and inertia dominated, resonating and antiresonating cases under random sea states are analyzed to highlight the implications and relative merits of four salient linearization techniques.     

煤体静载破坏中低频磁场变化特征及产生机制研究

为了研究煤体静载破坏中低频磁场变化特征及其产生机制,进一步完善煤矿动力灾害监测预警技术,通过室内试验、现场试验研究了煤体静载破坏中低频磁场时、频谱特征,并结合微震信号提出了低频磁信号的产生机制。结果表明：煤体静载破坏中所产生低频磁场信号强度为19～156 nT,信号最大幅值、能量与试样强度、加载速度均呈正相关关系。垂直于裂纹扩展面磁场最强,平行于裂纹扩展面磁场最弱。并结果微震信号提出了低频磁场产生机制。低频磁场与微震信号具有时、频域同步性,带电裂纹面随微震信号同频振荡为低频磁场产生机制。现场放炮破煤低频磁信号由簇状脉冲信号及小幅震荡信号组成,其中簇状脉冲成分产生于炮后振动波带动带电壁面的同频振动,而小幅震荡成分是巷帮煤壁趋向新应力平衡状态时发生的横向拉伸破坏及带电煤碎屑运移、摩擦及转动的结果。     

植被对波浪作用下床面切应力影响的数值模拟分析

本文基于OpenFOAM建立三维波浪数值水槽,模拟计算植被水域波浪作用下的床面切应力,分析了入射波高、植被密度、植被淹没高度、水流对植被水域波浪作用下床面切应力的影响。结果表明：纯波时,由于植被的阻水作用,植被水域床面切应力沿程衰减,其衰减程度与入射波高、植被密度及植被淹没高度呈现正相关;与纯波时相比,在波浪和同向流共同作用下正向床面切应力幅值增大,负向床面切应力幅值减小;弱水流对植被水域床面切应力的大小及分布无明显影响;强水流时,床面切应力在植被水域先增大后逐渐减小并在植被水域后显著降低。     

扬子及周缘地区上奥陶统-下志留统烃源岩发育环境及其控制因素

扬子地区下古生界发育了上奥陶统五峰组和下志留统龙马溪组两套有效烃源岩,查清其发育环境及其控制因素具有重要的科学理论和油气勘探意义.晚奥陶世开始,扬子地区进入碎屑岩陆棚演化阶段;五峰期-龙马溪期,扬子地区主体为局限的深水陆棚环境,总体呈现出浅水陆棚、深水陆棚、次深海共存的古地理格局.沉积体系展布和沉积演化主要受扬子陆块与华夏陆块的汇聚作用控制.扬子地区上奥陶统-下志留统烃源岩的形成与生烃母质生物的高生产力和高埋藏率、冰期-冰后期之交的气温快速转暖、海平面快速上升以及粘土矿物在有机质富集保存过程中的赋存驻留作用等密切相关.     

Multiple-Step Predictive Control for Offshore Structures

—Ocean wave propagation is slow,visible and measurable,so a wave theory can be used to approxi-mately predict the imminnent wave force on an offshore structure based on measured,real-time wave elevation nearthe structure.This predictability suggests the development of a more efficient algorithm,than those that have beendeveloped for structures under wind and seismic loads,for the active vibration control of offshore structures.Thepresent study delveops a mutiple-step predictive optimal control(MPOC)algorithm that accounts for multiple-step external loading in the determibation of optimal control forces.The control efficiency of the newly developedMPOC algorithm has been investigated under both regular(single-frequency)and irregular(multiple-frequency)wave loads,and compared with that of two other well-known optimal control algorithms:classical linear optimalcontrol(CLOC)and instantaneou optimal control(IOC).     

The influence of dunes on mixing in a migrating salt‐wedge: Fraser River estuary,Canada

Dune bedforms and salt‐wedge intrusions are common features in many estuaries with sand beds, and yet little is known about the interactions between the two. Flow visualization with an echosounder and velocity measurements with an acoustic Doppler current profiler over areas of flat‐bed and sand dunes in the highly‐stratified Fraser River estuary, Canada, were used to examine the effect of dunes on interfacial mixing. As the salt‐wedge migrates upstream over the flat‐bed, mixing is restricted to the lower portion of the water column. However, as the salt‐wedge migrates into the dune field from the flat bed, there is a dramatic change in the flow, and large internal in‐phase waves develop over each of the larger dunes, with water from the salt‐wedge reaching the surface of the estuary. The friction Richardson number shows that bed friction is more important in interfacial mixing over the dunes than over the flat‐bed, and a plot of internal Froude Number versus obstacle (dune) height shows that the salt‐wedge flow over the dunes is mainly supercritical. Such bedforms can be expected to cause similar effects in interfacial mixing in other estuaries and sediment‐laden density currents, and may thus be influential in fluid mixing and sediment transport. Copyright © 2010 John Wiley & Sons, Ltd.