浅水三角洲分流河道沉积模式分类

通过浅水三角洲现代沉积考察分析,结合探地雷达(GPR)资料,对浅水三角洲分类方案和对应的沉积模式进行探讨。结果表明:根据分流河道弯曲指数和分叉参数,将浅水三角洲分为分叉平直河三角洲、分叉曲流河三角洲、分汇曲流河三角洲和分汇辫状河三角洲4种类型,并建立了各类型的沉积模式; 浅水三角洲沉积模式的控制因素是分流河道下蚀作用和侧蚀作用的强度。将该沉积模式应用于渤海南部海域BZ25-1油田新近系明化镇组下段砂体内部构型的研究认为:明化镇组下段4油层组2小层(NmⅣ₂)时期是低位体系域早期,发育分汇曲流河三角洲,河道间为侧积隔夹层; 明化镇组下段4油层组1小层(NmⅣ₁)时期湖平面上升,发育分汇辫状河三角洲,河道间为垂积隔夹层。这为下一步的开发方案设计提供了指导。     

隐性前积浅水曲流河三角洲地震沉积学特征——以渤海湾盆地冀中坳陷饶阳凹陷肃宁地区为例

以渤海湾盆地冀中坳陷饶阳凹陷肃宁地区为例,综合岩心、测井和三维地震综合解释资料,开展隐性前积浅水曲流河三角洲地震沉积学特征研究,并总结隐性前积浅水曲流河三角洲沉积模式。肃宁地区古近系沙一上亚段(Es1s)—东三段(Ed3)可识别出8个四级层序,反映湖平面周期性变化。从湖心向湖岸、从湖侵域向高位域,泥岩由灰色变为红色,显示湖水由深变浅。地震反射结构指示湖水变浅:Es1s(SQV3)叠瓦状前积厚度显示湖心水深40~60 m;随后叠瓦状前积结构消失,演变为亚平行结构(SQV4—SQV6),反射连续性逐渐变差,反映水深不超过30 m。岩心、测井曲线和地层切片分析揭示,与Es1s的SQV3叠瓦状前积浅水曲流河三角洲体系不同,Es1s的SQV4—SQV6为隐性前积浅水曲流河三角洲体系,地震沉积学响应特征主要为分带向湖盆中心推进的河道状和垛状地貌体系,指示分流河道和三角洲垛状体沉积。     

浅海低频声场水声信号时间相关性研究

起伏的声场接收信号是时变的,浅海声场的时间相关性研究有利于目标深度的判别以及水声信号的数据融合。研究浅海低频声场时间相关性以信号的自相关和互相关原理为基础,完成对信号时间相关半径、相关函数值的影响因素分析,得到不同声场条件下信号传播的作用结果。通过仿真比较在不同频率、不同信噪比条件下低频声场信号的相关性曲线,并结合实际海试数据进行验证。研究表明浅海低频声场随机扰动随着低频波长的增加而减弱,且信号时间相关性研究为声场的实际应用提供了一定参考。     

坳陷湖盆大型浅水三角洲沉积特征与生长模式

坳陷湖盆大型浅水三角洲是目前中国陆上岩性油气藏规模储量增长的主体。通过对松辽盆地南部上白垩统保乾三角洲和现代鄱阳湖赣江三角洲解剖,重点探讨湖盆浅水三角洲形成的地质背景、沉积特征与生长模式。结果表面:①坳陷湖盆具有形成大型浅水三角洲的沉积背景,敞流型湖盆导致的湖平面频繁升降控制了浅水三角洲的纵横向发育规模。②松辽盆地南部上白垩统发育2种不同类型的三角洲,深湖型三角洲一般呈朵叶状,沉积亚相展布清晰,沉积微相以分流河道、河口坝和分流河道间为主;浅湖型三角洲一般呈鸟足状或树枝状,沉积亚相分异不明显,沉积微相以分流河道和分流河道间为主,河口坝不发育;③通过现代沉积遥感定量分析,刻画了鄱阳湖赣江中支三角洲近50年的发育特征和演化规律,揭示了分流河道从分散树枝状到闭合结网状的生长过程。④坳陷湖盆大型浅水三角洲是不断发育的多期朵叶体在平面上拼接而成的复合体,其中分流河道是最重要的储集砂体类型,在平面上呈结网状分布,控制了大面积岩性油气藏的分布与富集。     

GENERAL CAUCHY PROBLEM FOR THE LINEAR SHALLOW -WATER EQUATIONS ON AN EQUATORIAL BETA-PLANE

1. INTRODUCTION Over the last two decades, studies in the tropical meteorology and ocean have dramatically increased, such as the EI Nino/Southern Oscillation (ENSO), the large-scale heat-induced circulation of the tropical atmosphere and nonlinear effec…     

NUMERICAL SIMULATION OF TWO-DIMENSIONAL DAM-BREAK FLOWS IN CURVED CHANNELS

Two-dimensional transient dam-break flows in a river with bends were theoretically studied. The river was modeled as a curved channel with a constant width and a flat bottom. The water was assumed to be an incompressible and homogeneous fluid. A channel-fitted orthogonal curvilinear coordinate system was established and the corresponding two-dimensional shallow-water equations were derived for this system. The governing equations with well-posed initial and boundary conditions were numerically solved in a rectangular domain by use of the Godunov-type finite-difference scheme, which can capture the hydraulic jump of dam-break flows. The comparison between the obtained numerical results and the experimental data of Miller and Chaudry in a semicircle channel shows the validity of the present numerical scheme. The mathematical model and the numerical method were applied to the dam-break flows in channels with various curvatures. Based on the numerical results, the influence of river curvatures on the dam-break flows was analyzed in details.     

浅水波近岸行为分步傅里叶方法研究

研究了用KdV方程模拟浅水波近岸的行为,如果用分步傅里叶方法,则水深变化导致的变系数KdV方程的非线性项存在局域性不好以及容易溢出等问题,作者用Matlab语言讨论了解决这些问题的简单方法,实现了浅水波近岸行为的快速分步傅里叶算法模拟,可模拟较长的传输距离,结果表明近岸水深减少导致水波峰值变大,前沿变陡,后沿变宽．     

胜坨油田浅水浊积相储集层流动单元研究

胜坨油田沙二段1砂层组2小层是浅水浊积相储集层，综合考虑岩性、物性、电性及非均质性和水淹特征，采用模糊聚类的方法将其分为4类流动单元。流动单元E以中砂岩为主，处在沉积旋回下部，分布于浊流中心相，基本没有无水开采期，高含水期含水上升减缓，非均质性弱，纵向剩余油分布差别小；流动单元G以细砂岩为主，处于沉积旋回中下部，分布于浊流中心相边部及边缘相内侧，非均质性最弱，水淹较均匀，高含水期仍有可观的可动剩余油；流动单元M以细砂岩、粉砂岩为主，处于沉积旋回中上部，分布于浊流边缘相的外侧，非均质性较强，是剩余油较富集的部位；流动单元P以夹泥质粉砂岩、粉砂质泥岩的细、粉砂岩为主，处于沉积旋回的顶部及底部，分布浊流相与湖相的交界部位，非均质性强，极容易形成剩余油，但剩余油总量不大且较难开发，经济价值不大。把流动单元研究与剩余油研究结合起来，可以为提高油气采收率提供可行的地质依据。     

Waves Generated by a Moving Source in a Two-Layer Ocean of Finite Depth

The velocity potentials of a point source moving at a constant velocity in the upper layer of a two-layer fluid are obtained in a form amenable to numerical integration. Each fluid layer is of finite depth, and the density difference between the two layers is not necessarily small. The far-field asymptotic behavior of the surface waves and internal waves are also derived using the method of stationary phase. They show that the wave system at the free surface or at the interface each contains contributions from two different modes: a surface-wave mode and an internal-wave mode. When the density difference between the two layers is small or the depth of the upper layer is large, the surface-wave mode mainly affects the surface waves while the internal-wave mode mainly affects the internal waves. However, for large density difference, both modes contribute to the surface wave or internal wave system. For each mode, both divergent and transverse waves are present if the total depth Froude number is less than a certain critical Froude number which is mode-dependent. For depth Froude number greater than the critical Froude number, only divergent waves exist for that mode. This classification is similar to that of a uniform fluid of finite depth, where the critical Froude number is simply unity. The surface waves and internal waves are also calculated using the full expressions of the source potentials. They further confirm and illustrate the features observed in the asymptotic analysis.     

辽东湾坳陷新近系馆陶组浅水三角洲的发现及其油气勘探意义

为突破辽东湾坳陷新近系馆陶组沉积相的早期认识对该区油气勘探下一步进展的制约,以沉积地质、地球物理和古生物相结合的分析方法,详细分析了湖泊及浅水三角洲存在的地质背景和证据。通过辽河坳陷馆陶组和明化镇组下段的沉积模式及可可西里卓乃湖-库赛湖区的现代沉积比较,结合孢粉百分含量法和相对比值法的半定量分析方法所揭示的古湿度和古温度分析结果,认为馆陶组主要是亚热带且湿度逐渐增大的气候条件下,以冲积扇和辫状河为主,具有大平原小前缘特点的浅水三角洲沉积模式。三角洲平原分为以冲积扇为主的上平原和以辫状河为主的下平原,三角洲前缘具有平面规模小、不稳定、河口坝和远砂坝不发育的特征。馆陶组下段封闭型湖泊面积小,以三角洲平原沉积为主;馆陶组上段湖域面积扩大,三角洲前缘更加发育,且次级洼陷之间由辫状河水系连通,呈敞流型湖泊特征。辽东湾坳陷新近系馆陶组浅水三角洲沉积体系的新认识使得前三角洲泥岩发育区可能成为区域性盖层,为下一步大型油气藏的勘探提供重要的地质指导。