A TIME-STEPPING FINITE ELEMENT METHOD FOR ANALYSIS OF CONTAMINANT TRANSPORT IN FRACTURED POROUS MEDIA

This paper describes the development of a finite element method for analysing contaminant transport in double-porosity geomaterials using a time-stepping approach. In many cases, double-porosity models may be used to represent fractured rock formations and fissured soils. A distinctive feature of utilizing this kind of model is that it is not necessary to have an intimate knowledge of the nature, distribution and properties of individual fractures and fracture arrangement since the fracture geometry and details are considered only in an averaged or equivalent continuum sense. The flux exchange that occurs between the fluid in the fractures and in the solid matrix is represented by a linear heriditary process. This has the consequence that in order to carry the solution forward from time t to t+Δt, it is necessary to know and to store the complete contaminant history up to time t. This paper shows that all the hereditary information necessary to carry the solution forward is contained in the values of certain hereditary variables at time t so that it is not necessary to store the complete time history and consequently a more efficient numerical process can be developed.     

ANALYSIS OF COUNT DATA USING POISSON REGRESSION*

In geographical research the data of interest are often in the form of counts. Standard regression analysis is inappropriate for such data, but if certain assumptions are met, a form of regression based on the Poisson distribution can be used. This paper illustrates the use of Poisson regression in the computer package GLIM with an example from historical geography. Apprentice migration to Edinburgh is regressed on a combination of categorical, count, and continuous explanatory variables.     

The Emergence of New Hispanic Settlement Patterns in Appalachia*

This article evaluates the emerging Hispanic population in Appalachia, which nearly tripled in size to 465,000 between 1980 and 2000. Using 1980, 1990, and 2000 census data, changes in the geographic distribution of Hispanics and in the economic characteristics of counties with growth in Hispanic population are assessed. Results suggest that high‐growth counties are clustered in peripheral areas in the northern and southern subregions and are characterized by higher per capita income and greater economic viability than those areas with relatively low Hispanic population growth.     

丽水-椒江凹陷新生代构造应力场数值模拟与油气运聚关系探讨

根据前人对东海丽水-椒江凹陷地质研究成果和最新资料,指出新生代的丽水-椒江凹陷主要处于张性应力场中,应力场是控制该区油气运聚的主要因素。采用Maxwell粘弹性模型,对新生代古构造应力场进行了数值模拟。模拟结果表明瓯江运动期,丽水-椒江凹陷处于一种右旋拉张环境;玉泉期的丽水-椒江凹陷处于一种比较稳定的弱拉张环境。研究表明丽水西次凹LS36-1-1井以西,MYF-1井以南的缓坡带是比较有利的油气勘探区域。灵峰凸起带因为应力值偏高有可能导致运移到此处的油气已经沿断层逸散或者被破坏。     

关于煤炭三维地震勘探发展的几点思考

根据中国煤炭地震勘探技术发展现状及趋势,提出了三维地震勘探技术今后应重点关注及开展研究的几个问题.提高地震勘探分辨率,首先要提高地震勘探反射波的频率,其次可考虑激发和利用低速波.采用小网格采集技术有利于小构造识别,使用该技术要考虑：一是目标地质体的大小尺度,二是针对倾斜层的最高无混叠频率,三是横向分辨率.利用多次覆盖技术提高地震波信噪比,针对地层倾角大、构造复杂地区,应使用叠前深度偏移处理技术.为提高矿藏及其构造的精细刻画与描述,改善成像质量,应加强开展单点地震勘探高密度采集技术的应用.     

塔里木盆地西南部齐姆根逆冲推覆构造的特征及其与油气的关系

齐姆根逆冲推覆构造带位于喀什凹陷与叶城凹陷之间的齐姆根凸起上,由3个与盆地边缘大体平行的次级逆冲构造带组成,即阿尔塔什推覆构造带、科克然达坂-希根纳孜吉勒嘎推覆构造带、库斯拉甫推覆构造带。3个次级逆冲构造带分别将石炭系—二叠系推覆在侏罗系、白垩系及古近系—新近系之上,将泥盆系推覆在石炭系—二叠系之上,将元古宙变质岩及古生代花岗岩逆冲在泥盆系及泥盆系之上不整合覆盖的侏罗系之上。根据推覆体地层的叠置关系及逆冲断层的发育特征,齐姆根逆冲推覆构造带是由北向南演化的、后展式发展的逆冲推覆构造系统,其间发育横向调节的走滑断层。逆冲推覆体系的主体断裂沟通了源岩与储层,推覆体下盘发育的大型背斜圈闭为油气聚集提供了有利的场所,运聚条件的合理配置为该区油气勘探提供了良好的前景。     

The Offset-Domain Prestack Depth Migration with Optimal Separable Approximation

The offset-domain prestack depth migration with optimal separable approximation, based on the double square root equation, is used to image complex media with large and rapid velocity variations. The method downward continues the source and the receiver wavefields simultaneously. The mixed domain algorithm with forward Fourier and inverse Fourier transform is used to construct the double square root equation wavefield extrapolation operator. This operator separates variables in the wave number domain and variables in the space domain. The phase operation is implemented in the wave number domain, whereas the time delay for lateral velocity variation is corrected in the space domain. The migration algorithm is efficient since the seismic data are not computed shot by shot. The data set test of the Marmousi model indicates that the offset-domain migration provides a satisfied seismic migration section on which complex geologic structures are imaged in media with large and rapid lateral velocity variations.     

叠前深度偏移在复杂构造模型成像中的应用

研究了叠前深度偏移在复杂构造模型成像中的应用。主要对一个复杂的地质模型所正演出的地震数据资料进行试验性处理,并对该试验性处理结果进行归纳分析,得出速度~深度模型的准确性决定于对偏移结果的质量以及根据地下构造选取偏移孔径的原则等定性认识和结论。通过这些认识和结论,对实际地震资料的处理有一定的指导意义。