曲流点坝内部剩余油形成与分布规律物理模拟

建立了曲流点坝物理模型,模拟地下曲流点坝储层进行驱替实验。观察注入剂的运动规律,同时,在模型上布置了测量电极,以双电极法测量驱替过程中垂向电阻变化,反映注入剂波及高度的变化规律。分析了侧积泥岩夹层的建筑结构对注入剂在点坝砂体中的流动规律,以及对剩余油的形成分布的影响。通过实验研究证实,在曲流点坝内部,侧积泥岩夹层对注入剂具有强烈的遮挡作用,受其影响形成侧积体差异型剩余油、重力型剩余油以及压力异常型剩余油三种类型剩余油,主要分布在点坝的中上部。在实际生产中,利用水平井钻遇点坝上部进行开采是主要的手段。     

S-wave velocity images of the Dead Sea Basin provided by ambient seismic noise

Based on passive seismic interferometry applied to ambient seismic noise recordings between station pairs belonging to a small-scale array, we have obtained shear wave velocity images of the uppermost materials that make up the Dead Sea Basin. We extracted empirical Green’s functions from cross-correlations of long-term recordings of continuous data, and measured inter-station Rayleigh wave group velocities from the daily correlation functions for positive and negative correlation time lags in the 0.1–0.5 Hz bandwidth. A tomographic inversion of the travel times estimated for each frequency is performed, allowing the laterally varying 3-D surface wave velocity structure below the array to be retrieved. Subsequently, the velocity-frequency curves are inverted to obtain S-wave velocity images of the study area as horizontal depth sections and longitude- and latitude-depth sections. The results, which are consistent with other previous ones, provide clear images of the local seismic velocity structure of the basin. Low shear velocities are dominant at shallow depths above 3.5 km, but even so a spit of land with a depth that does not exceed 4 km is identified as a salt diapir separating the low velocities associated with sedimentary infill on both sides of the Lisan Peninsula. The lack of low speeds at the sampling depth of 11.5 km implies that there are no sediments and therefore that the basement is near 10–11 km depth, but gradually decreasing from south to north. The results also highlight the bowl-shaped basin with poorly consolidated sedimentary materials accumulated in the central part of the basin. The structure of the western margin of the basin evidences a certain asymmetry both whether it is compared to the eastern margin and it is observed in north–south direction. Infill materials down to ∼8 km depth are observed in the hollow of the basin, unlike what happens in the north and south where they are spread beyond the western Dead Sea shore.     

平推式滑坡多级拉陷槽形成过程及成因机理分析

通过对中江县冯店垮梁子滑坡的现场调查和室内物理模拟试验研究,发现滑坡滑动过程中存在诱发次级拉裂缝产生甚至贯通的现象,结合滑坡的变形历史迹象,进行受力分析,论证拉裂缝产生形成过程及位于拉裂缝间滑带局部贯通现象,提出U形槽模式多级平推式滑动理论; 对比宣汉天台乡滑坡已有对多级平推式滑坡研究,针对多级平推式滑坡后缘多级拉陷槽的形成过程和成因机理进行分析,提出多级平推式滑坡存在牵引后退式和推动前进式两种不同启动和运动模式,就两种模式各自岩性组成、构造裂隙发育情况、启动水头、启动速度、及多级滑动启动水头变化对比分析,建立地质力学机制模型。     

Seismic response of flexible cantilever retaining walls with dry backfill

Failure of retaining walls during earthquakes has occurred many times in the past. Although significant progress has been made in analysing the seismic response of rigid gravity type retaining walls, considerable difficulties still exist in the seismic-resistant design of the flexible cantilever type of retaining walls because of the complex nature of the dynamic soil–structure interaction. In this paper the seismic response of cantilever retaining walls with dry backfill is simulated using centrifuge modelling and numerical modelling. It is found that bending moments on the wall increased significantly during an earthquake. After the end of base shaking, the residual moment on the wall was significantly higher than the moment under static loading. The numerical simulation is able to model quite accurately the main characteristics of acceleration, bending moment, and displacement recorded in the centrifuge test.     

FLAC3D在边坡数值分析及位移监测中应用

以辽宁省岫岩县某山头边坡为例,通过槽探、钻探、大型剪切试验等多种手段,找出合理潜在滑动面。利用FLAC3D软件对该边坡进行三维数值模拟,分析应力应变关系,得出变形较大及应力集中区域,同时利用强度折减法得出边坡的安全系数,评价其稳定性。将从边坡后缘张拉裂隙上布设的位移监测点采集到的数据,与数值模拟结果进行对比分析,验证数值模拟的可靠性,为边坡抗滑设计提供依据。     

Evaluation of distributed recharge in an upland semi-arid karst system: the West Bank Mountain Aquifer,Middle East

Assessment of recharge in a structurally complex upland karst limestone aquifer situated in a semi-arid environment is difficult. Resort to surrogate indicators such as measurement of spring outflow and borehole discharge, is a common alternative, and attempts to apply conventional soil moisture deficit analysis may not adequately account for the intermittent spate conditions that arise in such environments. A modelling approach has been made using the West Bank Mountain Aquifer system in the Middle East as a trial. The model uses object oriented software which allows various objects to be switched on and off. Each of the main recharge processes identified in the West Bank is incorporated. The model allows either conventional soil moisture deficit analysis calculations or wetting threshold calculations to be made as appropriate, and accommodates both direct recharge and secondary recharge. Daily time steps enable recharge and runoff routing to be calculated for each node. Model runs have enabled a series of simulations for each of the three aquifer basins in the West Bank and for the whole of the West Bank. These provide recharge estimates comparable to those prepared by earlier workers by conventional means. The model is adaptable and has been successfully used in other environments.     

On CO<Subscript>2</Subscript> fluid flow and heat transfer behavior in the subsurface,following leakage from a geologic storage reservoir

Geologic storage of CO₂ is expected to produce plumes of large areal extent, and some leakage may occur along fractures, fault zones, or improperly plugged pre-existing wellbores. A review of physical and chemical processes accompanying leakage suggests a potential for self-enhancement. The numerical simulations presented here confirm this expectation, but reveal self-limiting features as well. It seems unlikely that CO₂ leakage could trigger a high-energy run-away discharge, a so-called “pneumatic eruption,” but present understanding is insufficient to rule out this possibility. The most promising avenue for increasing understanding of CO₂ leakage behavior is the study of natural analogues.     

Reciprocality between biology and geology: Reconstructing polar Gondwana

The reciprocal nature of the relationship between historical geology (reconstruction models) and biology (constructing phylogenies) is discussed and the conceptual basis of such a relationship is examined through its historical development. Examples to illustrate aspects of the relationship are drawn from the Cretaceous breakup of polar Gondwana and the Cenozoic history of some of the resultant microcontinental fragments. A new mid-Cretaceous (circa 100 Ma) rift zone, separating the west Gondwanan Campbell Plateau, southern New Zealand, from the east Gondwanan Melanesian Rift is proposed, and biological and geological evidence for it is presented and discussed. It is also suggested that the Bounty Trough, Chatham Rise, and Hikurangi Plateau unit is incorrectly placed in reconstruction models, and it should be fitted outboard of the Melanesian Rift until its mid-Cenozoic attachment to the Campbell Plateau. It is concluded that both reconstruction modelling and phylogenetic analyses have much to gain through ‘reciprocal illumination’.     

Groundwater flow and solute transport at the Mourquong saline-water disposal basin, Murray Basin, southeastern Australia

Saline groundwater and drainage effluent from irrigation are commonly stored in some 200 natural and artificial saline-water disposal basins throughout the Murray-Darling Basin of Australia. Their impact on underlying aquifers and the River Murray, one of Australia's major water supplies, is of serious concern. In one such scheme, saline groundwater is pumped into Lake Mourquong, a natural groundwater discharge complex. The disposal basin is hydrodynamically restricted by low-permeability lacustrine clays, but there are vulnerable areas in the southeast where the clay is apparently missing. The extent of vertical and lateral leakage of basin brines and the processes controlling their migration are examined using (1) analyses of chloride and stable isotopes of water (²H/¹H and ¹⁸O/¹⁶O) to infer mixing between regional groundwater and lake water, and (2) the variable-density groundwater flow and solute-transport code SUTRA. Hydrochemical results indicate that evaporated disposal water has moved at least 100 m in an easterly direction and that there is negligible movement of brines in a southerly direction towards the River Murray. The model is used to consider various management scenarios. Salt-load movement to the River Murray was highest in a "worst-case" scenario with irrigation employed between the basin and the River Murray. Present-day operating conditions lead to little, if any, direct movement of brine from the basin into the river. Electronic Publication     

Can flat-ramp-flat fault geometry be inferred from fold shape?: A comparison of kinematic and mechanical folds

The inference of fault geometry from suprajacent fold shape relies on consistent and verified forward models of fault-cored folds, e.g. suites of models with differing fault boundary conditions demonstrate the range of possible folding. Results of kinematic (fault-parallel flow) and mechanical (boundary element method) models are compared to ascertain differences in the way the two methods simulate flexure associated with slip along flat-ramp-flat geometry. These differences are assessed by systematically altering fault parameters in each model and observing subsequent changes in the suprajacent fold shapes. Differences between the kinematic and mechanical fault-fold relationships highlight the differences between the methods. Additionally, a laboratory fold is simulated to determine which method might best predict fault parameters from fold shape. Although kinematic folds do not fully capture the three-dimensional nature of geologic folds, mechanical models have non-unique fold-fault relationships. Predicting fault geometry from fold shape is best accomplished by a combination of the two methods.