Sedimentology and seismic geomorphology of a lacustrine depositional system from the deep zone of the Gaoyou Sag,Subei Basin,eastern China

Sandstones of the Dainan Formation in the Gaoyou Sag of the Subei Basin are important hydrocarbon reservoirs. This paper studies the sedimentary facies and sandstone dispersal patterns in the Gaoyou Sag, based on the analysis of sedimentology and seismic geomorphology. The data used in this study include lithological data, wire-line-log data and three-dimensional (3D) seismic data. The target strata are the Eocene Daiyi Member (E₂d₁³, E₂d₁² and E₂d₁¹) and the lower Dai'er Member (E₂d₂⁵), which belong to three third-order sequences. Five types of depositional systems were identified in the Dainan Formation based on core observation and log-facies analysis. They are, respectively, delta, fan delta, sub-lacustrine fan, nearshore subaqueous fan and lacustrine system. Stratal slices from 3D seismic volumes have been used to map the sandstone dispersal patterns and to document the evolution of the depositional systems within these third-order sequences and associated systems tracts. In the low-stand systems tract and the high-stand systems tract, sandstones of delta, fan delta and nearshore subaqueous fan were well developed and can be delineated by stratal slices showing distinct progradation towards the deep lake centre. In the transgressive systems tract, sandstones are less common. Stratal slices indicate that the depositional environments of individual third-order sequences evolved from gravel-rich or sand-rich fans to lacustrine mudstones, and finally to mixed sandstone–mudstone fans. Sandstone dispersal patterns appear to be primarily controlled by syn-sedimentary faults, and generally sandstone thickness decreases with distance from the syn-sedimentary faults. Deltas and fan deltas have different characteristics in sand-body thickness because they have different sedimentary subfacies. The proposed geomorphology and sedimentary evolution of the lacustrine depositional system may aid in the prediction of potential reservoir distribution in the Gaoyou Sag.     

一种基于四叉树的大规模影像数据库构建方法

为了能流畅地漫游大范围的影像数据,必须使用影像金字塔技术,将影像的切片数据存入数据库系统,建立全区域的多分辨率影像数据库。使用数据库索引机制结合四叉索引树模型,可以完美地实现影像切片数据的高效检索,进而实现全区域影像的流畅漫游。     

两种土壤条件下荒漠盐生植物根际系统养分分布的实验研究

采用水平根垫法对四种不同类型的荒漠盐生植物进行栽培实验,应用冰冻薄层切片法对距根表不同距离的土壤进行分层取样,并测定不同层次土壤中pH值、总盐、速效N、有效P、速效K、交换性Ca和Mg的含量。结果表明,在盐土中,距根表不同距离的土壤中,pH值均呈有规律的梯度分布,即根际微区pH值较土体下降,且距根表越近,pH值越低,而在棉田土中却没有显著变化;总盐在根际出现较大的亏缺区。在盐土中,四种植物根际的速效N都呈现出亏缺的趋势,在0—3 mm范围内变化幅度最大。四种植物根际速效N在棉田土壤中的变化趋势与盐土中相似,也呈现出亏缺,但亏缺的程度稍低。四种植物根际有效P的变化与速效N不同,在盐土中,四种植物根际有效P呈现富集的趋势,但富集程度不高,最大富集范围出现在距根表0—5 mm范围内,芦苇的富集率最低。在棉田土中,根际有效P的变化与在盐土中相反,表现为亏缺,并且亏缺幅度很大;四种植物根际速效K的变化与有效P相似。根际交换性Ca的在盐土和棉田土中的分布有差异。在盐土中,根际中交换性Ca分布较均匀,没有显著的变化,而在盐土中却富集。在荒漠盐土中, N、P和K在几乎所有植株中地上部分都显著大于地下部分,N和K尤为显著;除芦苇外,Ca和Mg则是地下部分大于地上部分,琵琶柴尤为显著,这可能与它们各自的生理类型有关。     

河道砂体宽/窄方位三维观测系统地震物理模型分析

The effect of the wide and narrow azimuth 3D observation systems on seismic imaging precision is becoming a hot area for studies of high precision 3D seismic acquisition methods in recent years. In this paper we utilize 3D physical seismic modeling experiments. A 3D channel sand body physical seismic model is constructed and two acquisition systems are designed with wide azimuth （16 lines） and narrow azimuth （8 lines） to model 3D seismic data acquisition and processing seismic work flows. From analysis of migrated time slice data with high quality and small size, we conclude that when the overlying layers are smooth and lateral velocities have little change, both wide and narrow azimuth observation systems in 3D acquisition can be used for obtaining high precision imaging and equivalent resolution of the channel sand body.     

Slope stability analysis by polar slice method in rotational failure mechanism

In this paper, a polar slice method is proposed to quantify the energy dissipation in the inner sliding soil mass and evaluate the slope stability in rotational failure mechanism. The polar slice method is compared with the vertical slice method. Despite similar results, the advantages of the polar slice method are explained. Besides, the comparison between the polar slice method and Chen’s method shows that the polar slice method would lead to more accurate results than Chen’s method, while Chen’s method which neglects the energy dissipation in the inner sliding soil mass is relatively conservative.     

Effective KEM solutions for the limit load and the slope stability problem

The matrix formulation for the limit‐load problem in soil mechanics can be solved by the KEM effectively. The solution of the slope stability problem is more complicated in principle, but together with an effective iteration technique the solution of the implicit equation system can be simplified to the recursive solution of just a quadratic equation. Copyright © 2000 John Wiley & Sons, Ltd.     

相干体与方差体技术在全三维地震资料解释中的应用

近几年迅速发展起来的相干体与方差体技术是研究三维数据体中的不连续性特征及相邻道地震信号之间相似性的解释性处理技术,有利于在三维地震资料解释之前,了解研究区内断层的展布情况,缩短三维地震资料解释周期,提高解释效率和精度。该技术充分利用了三维资料中每个CDP点的信息,避免了因常规抽线解释而遗漏小断层。该项技术在全三维地震解释中起着重要的作用,应用效果明显。本文介绍了方法原理和基于相干体与方差体技术的全三维地震资料解释思路,展示了相干体与方差体技术的应用实例。     

花岗岩中熔融包裹体恢复均匀化后探针片的磨制工艺

针对磨制样品十分细小和较薄等特点，采用如下三个步骤磨制：①以加热过的细小样品为中心创建一磨制平面；②将样品周围的岩石薄块磨至接近细小样品的相同厚度；③在抛光机上抛光，使包裹体完全露出表面。文中还介绍了样品磨毛后观察其中包裹体的方法以及包裹体完全磨出表面后的若干识别标志。     

降雨入渗非饱和黏土边坡稳定性的极限平衡条分法研究

考虑非饱和黏土边坡的基质吸力和渗流力,根据水位线位于滑面上、下的临界平衡状态,分别建立了滑体条块极限平衡状态下力和力矩平衡式,获得了降雨条件下非饱和黏土边坡稳定性的极限平衡条分法计算式。通过试验、参量变换以及作用力的位置关系可以确定相关参量,并采用数值计算求解临界平衡状态下滑体条块的相互作用力系数和非饱和边坡安全系数。案例结果表明：考虑渗流力时的非饱和黏土边坡安全系数比不考虑渗流力的安全系数降低约13.8%,且考虑渗流力作用的条间力作用系数变化率明显大于不考虑渗流力的结果;当降雨强度超过一定值时,坡面径流很快形成,边坡出现不稳定的时间基本相同。     

采空区残余倾斜变形对路基稳定性的影响分析与评价

地下开采导致的地表残余倾斜对采空区公路路基的稳定性有重要影响。针对采空区公路路基的稳定性评价,笔者提出了基于概率积分法和Knothe时间函数的地表残余倾斜的计算方法,分析了路基稳定性的条分法计算原理及残余倾斜对路基稳定性的影响机理,推导了基于解析法的路基最不利滑动面计算公式,使用C#语言编制了路基稳定性系数计算软件,并通过工程实例,对提出的方法和软件进行了验证,分析了地表残余倾斜、路基边坡坡率对路基稳定性的影响。