Prediction of volumes and risk in hydrocarbon exploration: a quantification of geology

 The prediction of the hydrocarbon potential of a specific trap or of a number of specific traps (venture), referred to herein as prospect appraisal, concerns a probabilistic exercise based on the quantification of geology in terms of structural closure, reservoir quality, hydrocarbon charge, and the retention potential of the seal. Its objectives include: (a) prediction of the hydrocarbon volumes that could be present in the trap from an analysis of its geologic attributes; (b) the amount of uncertainty introduced in the volumetric prediction by the uncertainties in the subsurface geology; (c) the risk that one or more of the essential attributes of the prospect are underdeveloped and recoverable reserves are absent. The uncertainty of the geologic input requires a probabilistic approach, for which the Monte Carlo procedure is well suited. Prospect appraisal forms the basis for decision-making in oil exploration and development and, therefore, should be reliable, consistent, and auditable. This requires the use of a consistent methodology, the development of reliable models to quantify the geologic processes involved, and the collection of comprehensive and relational databases for the many geologic variables. As a result of data availability, uncertainty and risk tend to increase strongly from mature, producing basins to areas of frontier exploration. This may complicate management of exploration portfolios. Received: 1 July 1996/Accepted: 25 November 1996     

Seismic Hazard Studies in the U.K.: Source Specification Problems of Intraplate Seismicity

Although the U.K. is in an area of only low to moderate seismicity, the seismic hazard is sufficient to pose a threat to sensitive structures such as chemical plants and nuclear facilities. In quantifying the level of hazard by conventional probabilistic methodology, however, some problems arise in attempting to interpret earthquake data in terms of geological structure and faults. In the U.K., not only is it impossible to identify any demonstrably active faults, but also it is extremely difficult to discern any relationship between the pattern of seismicity and local or regional geological structure.This study discusses the use of two zonation approaches which complement each other in such a way that the general character and trend of seismicity is preserved. In one approach, the zonation is informed by the structural geology, where possible; geological zonation is avoided if it produces sources with heterogeneous seismicity. In the other approach, the record of past earthquakes is divided up into very small zones around individual epicentres or groups of epicentres, the size of each zone usually being proportional to the uncertainty in the epicentral determination of the appropriate event. This zonation preserves an observed tendency of some British earthquakes to repeat themselves. It is suggested that, in intraplate areas such as the U.K., it is often inappropriate to attempt to model individual fault sources. No faults in the U.K. are provably active. Because an earthquake of moderate size can occur on a very short fault segment, it is impractical to restrict fault modelling to major features. Even the two largest U.K. faults, suspected to be active, pose problems in attributing historical seismicity to them as distinct features.     

Conceptually-based shot noise modeling of streamflows at short time interval

A conceptual-stochastic approach to short time runoff data modelling is proposed, according to the aim of reproducing the hydrological aspects of the streamflow process and of preserving as much as possible the dynamics of the process itself. This latter task implies preservation of streamflow characteristics at higher scales of aggregation and, within a conceptual framework, involves compatibility with models proposed for the runoff process at those scales. At a daily time scale the watershed response to the effective rainfall is considered as deriving from the response of three linear reservoirs, respectively representing contributions to streamflows of large deep aquifers, with over-year response lag, of aquifers which run dry by the end of the dry season and of subsurface runoff. The surface runoff component is regarded as an uncorrelated point process. Considering the occurrences of effective rainfall events as generated by an independent Poisson process, the output of the linear system represents a conceptually-based multiple shot noise process. Model identification and parameter estimation are supported by information related to the aggregated runoff process, in agreement to the conceptual framework proposed, and this allows parameter parsimony, efficient estimation and effectiveness of the streamflow reproduction. Good performances emerged from the model application and testing made with reference to some daily runoff series from Italian basins.     

地质速率计—矿物氧扩散的应用

概述了同位素封闭体系内的矿物氧扩散和同位素交换机制及其在地质速率计上的应用。火成岩从高温冷却或变质岩从高峰主质温度冷却过程中，由于冷却速度不同，扩散作用导致的矿物晶体内部及晶粒间氧同位素再平衡也有所不同。通过实测岩石中各组成矿物氧同位素比值，模式含量和颗粒半径，据矿物氧扩散和同位素交换模型，可以估算出岩石的冷却速率。     

金矿床地球化学异常模式研究的新进展

论述了近十年来金矿床地球化学异常模式研究的新进展，９０年代以前研究和建立了石英脉和蚀变岩型金矿地球化学异常模式，９０年代以来，研究和建立了中国主要类型金矿床地球化学导航异常模式，热液金矿床和原生叠加晕理想模式，金矿床包裹体气晕，离子晕及其叠加晕理想模式。     

大汶河流域洪灾的成因及防治对策

阐述了大汶河流域洪涝灾害的特点,并对洪涝灾害发生的原因进行了分析,提出了预防为主、综合治理、系统防治和重点防治相结合、标本兼治的防治思路及具体防治对策.     

Numerical simulations for coupled rock deformation and gas leak flow in parallel coal seams

Based on the new viewpoint of interaction mechanics for solid and gas, gas leakage in parallel deformable coal seams can be understood. That is, under the action of varied geophysical fields, the methane gas flow in a double deformable coal seam can be essentially considered to be compressible with time-dependent and mixed permeation and diffusion through a pore-cleat deformable, heterogeneous and anisotropic medium. From this new viewpoint, coupled mathematical models for coal seam deformation and gas leak flow in parallel coal seams were formulated and the numerical simulations for slow gas emission from the parallel coal seams are presented. It is found that coupled models might be close to reality. Meanwhile, a coupled model for solid deformation and gas leak flow can be applied to the problems of gas leak flow including mining engineering, gas drainage engineering and mining safety engineering in particular the prediction of the safe range using protective layer mining where coal and gas outbursts can efficiently be prevented. This revised version was published online in July 2006 with corrections to the Cover Date.     

长江流域水资源、灾害及水环境状况初步分析

长江是我国第一、世界第三大河流,发源于青藏高原,全长6300多公里,流域面积180×104km²,占中国陆地面积的1/5。长江及其流域不仅以其不可替代的自然资源优势和其他江河无法比拟的区位优势,在我国国民经济和社会发展中扮演着举足轻重的角色,特别是约占全国的36%、拥有9616×10⁸m³的年径流量(为黄河的20倍),是我国最重要的水源地。这不仅对长江流域资源优势的发挥和缓解我国北方地区日趋严重的水资源短缺问题至关重要,而且对全国的可持续发展也将产生深远影响。然而,在长江流域大规模开发及经济快速发展的同时,人类活动与自然规律的负面效应相互叠加,导致了流域环境的生态调节和自我恢复功能大幅降低,引起了日趋严重的水环境退化、洪涝灾害威胁加剧等问题。文章首先对长江流域水资源的重要性及其作用做了分析,肯定了其丰富的资源和重要的战略地位,该流域在占全国不足18%的土地上,集中了40%以上的人口及国民生产总值,而且其经济地位有进一步上升的趋势,在水量及水能的蕴藏上,全流域湖泊面积达10323km²,占我国淡水湖泊总面积的37.2%,水能蕴藏总计达2.7×10⁸kW。另外,对长江流域日趋严重灾害及水环境问题做了探讨,尤其中游的洪水、淤积以及随着经济发