大别超高压榴辉岩高温高压下电导率实验研究

为研究大陆中下地壳高导层成因及与物质组成之间的关系,用模拟实验的方法在不同的温度、压力条件下分别测定了干的和1mol/LNaCl溶液饱和的榴辉岩的电导率.结果表明,干榴辉岩平行线理方向的电导率比垂直于线理方向的高,但两个方向上的活化能相近.在中下地壳条件下,干榴辉岩的电导率比中下地壳高导层电导率值低几个数量级.常温下1mol/LNaCl溶液饱和的榴辉岩两个方向上的电导率对压力具有不同的依赖性;在中下地壳条件下,1mol/LNaCl溶液饱和的榴辉岩的电导率可达到一般高导层的电导率值.无论干的还是饱和的榴辉岩都不能解释大别山20—50km深处的高导层成因,因此,在该深度范围内榴辉岩不可能是主要的岩石组成.     

考虑压裂裂缝的煤层气藏井网井距确定方法

煤层气藏具有低渗透率特点, 这使得其在直井排采前须对产层进行压裂改造,而压裂裂缝参数对井距的确定影响很大,因此研究裂缝长度、导流能力与井距的关系具有实际意义。通过对比不同裂缝穿透比和导流能力下的煤层气产量与采出程度,探讨裂缝参数对煤层气产出的影响规律;并以煤层气开采15a采出程度达到50%时的井距作为评价指标,研究压裂效果与井距的关系。研究结果表明,裂缝越长,导流能力越大,井距就越大-尤其在渗透率较小时,裂缝参数对井距的影响更明显。因此,在确定煤层气藏井距时,由于人工裂缝影响,裂缝方向的井距可适当放大。以我国韩城矿区煤层气区块储层参数为例,在给定优化指标下,宜选择矩形井网(350m×300m),或菱形井网(对角线长度为700m×400m)。     

Joint three-dimensional inversion of coupled groundwater flow and heat transfer based on automatic differentiation: sensitivity calculation, verification, and synthetic examples

Inverse methods are useful tools not only for deriving estimates of unknown parameters of the subsurface, but also for appraisal of the thus obtained models. While not being neither the most general nor the most efficient methods, Bayesian inversion based on the calculation of the Jacobian of a given forward model can be used to evaluate many quantities useful in this process. The calculation of the Jacobian, however, is computationally expensive and, if done by divided differences, prone to truncation error. Here, automatic differentiation can be used to produce derivative code by source transformation of an existing forward model. We describe this process for a coupled fluid flow and heat transport finite difference code, which is used in a Bayesian inverse scheme to estimate thermal and hydraulic properties and boundary conditions form measured hydraulic potentials and temperatures. The resulting derivative code was validated by comparison to simple analytical solutions and divided differences. Synthetic examples from different flow regimes demonstrate the use of the inverse scheme, and its behaviour in different configurations.     

α卡法和高密度电法在采空区探测中的应用

在治理采空区塌陷等地质灾害时,采空区位置的探测显得尤为重要。根据采空区和围岩间的导电性差异,结合地质资料,采用α卡法和高密度电法相结合的综合地球物理勘探方法,开展采空区位置的探测研究。研究表明：未充水的采空区出现α射线强度脉冲读数和视电阻率异常高值是探测采空区的地球物理前提条件;利用α卡法和高密度电法相结合的手段对采空区进行探测,效果良好,结论可靠。     

Effects of experimental uncertainty on the calculation of hillslope flow paths

Measurement uncertainty is a key hindrance to the quantification of water fluxes at all scales of investigation. Predictions of soil‐water flux rely on accurate or representative measurements of hydraulic gradients and field‐state hydraulic conductivity. We quantified the potential magnitude of errors associated with the parameters and variables used directly and indirectly within the Darcy – Buckingham soil‐water‐flux equation. These potential errors were applied to a field hydrometric data set collected from a forested hillslope in central Singapore, and their effect on flow pathway predictions was assessed. Potential errors in the hydraulic gradient calculations were small, approximately one order of magnitude less than the absolute magnitude of the hydraulic gradients. However, errors associated with field‐state hydraulic conductivity derivation were very large. Borehole (Guelph permeameter) and core‐based (Talsma ring permeameter) techniques were used to measure field‐saturated hydraulic conductivity. Measurements using these two approaches differed by up to 3\9 orders of magnitude, with the difference becoming increasingly marked within the B horizon. The sensitivity of the shape of the predicted unsaturated hydraulic conductivity curve to ±5% moisture content error on the moisture release curve was also assessed. Applied moisture release curve error resulted in hydraulic conductivity predictions of less than ±0\2 orders of magnitude deviation from the apparent conductivity. The flow pathways derived from the borehole saturated hydraulic conductivity approach suggested a dominant near‐surface flow pathway, whereas pathways calculated from the core‐based measurements indicated vertical percolation to depth. Direct tracer evidence supported the latter flow pathway, although tracer velocities were approximately two orders of magnitude smaller than the Darcy predictions. We conclude that saturated hydraulic conductivity is the critical hillslope hydrological parameter, and there is an urgent need to address the issues regarding its measurement further. Copyright © 2000 John Wiley & Sons, Ltd.     

高分辨率预测地下复杂采空区的空间分布特征--高密度电法在山西阳泉某复杂采空区中的初步应用研究

据前人资料,目标勘查区的深部可能存在多期、多类型、多开采对象的古采硐,但难以通过地表调查和常规的技术方法准确搞清其规模、形态、埋深等重要参数.本文采用高密度电法,结合厘米级高精度GPS测量和浅部钻探技术,针对不同类型的洞窟,选用不同的电极距,在复杂采空区地表布设了17条测线,完成了1 140个测点,共圈出120个电性异常.结合测区地质情况和异常的特殊形态,预测了可能为古采硐或相对致密岩石的物探异常.经首批19个钻孔验证,确认15个异常属于发生明显掉钻或漏浆现象的古采硐（陷落坑？）,4个异常是较为致密的石灰岩.实践证明,采用高密度电法能够高精度预测地下复杂采空区的空间分布特征,值得进一步推广.     

Estimation of anisotropic hydraulic conductivity using geophysical data in a coastal aquifer of Karnataka,India

Estimation of hydraulic parameters is essential to understand the interaction between groundwater flow and seawater intrusion. Though several studies have addressed hydraulic parameter estimation, based on pumping tests as well as geophysical methods, not many studies have addressed the problem with clayey formations being present. In this study, a methodology is proposed to estimate anisotropic hydraulic conductivity and porosity values for the coastal aquifer with unconsolidated formations. For this purpose, the one-dimensional resistivity of the aquifer and the groundwater conductivity data are used to estimate porosity at discrete points. The hydraulic conductivity values are estimated by its mutual dependence with porosity and petrophysical parameters. From these estimated values, the bilinear relationship between hydraulic conductivity and aquifer resistivity is established based on the clay content of the sampled formation. The methodology is applied on a coastal aquifer along with the coastal Karnataka, India, which has significant clayey formations embedded in unconsolidated rock. The estimation of hydraulic conductivity values from the established correlations has a correlation coefficient of 0.83 with pumping test data, indicating good reliability of the methodology. The established correlations also enable the estimation of horizontal hydraulic conductivity on two-dimensional resistivity sections, which was not addressed by earlier studies. The inventive approach of using the established bilinear correlations at one-dimensional to two-dimensional resistivity sections is verified by the comparison method. The horizontal hydraulic conductivity agrees with previous findings from inverse modelling. Additionally, this study provides critical insights into the estimation of vertical hydraulic conductivity and an equation is formulated which relates vertical hydraulic conductivity with horizontal. Based on the approach presented, the anisotropic hydraulic conductivity of any type aquifer with embedded clayey formations can be estimated. The anisotropic hydraulic conductivity has the potential to be used as an important input to the groundwater models.     

A partial explanation of the dependency of hydraulic conductivity on positive pore water pressure in peat soils

Part of the relationship between positive pore water pressures and hydraulic conductivity in peat soils may be explained by accumulations of methane bubbles. We show how compression and expansion of gas bubbles with changes in pore water pressure could cause changes in hydraulic conductivity and thus help to explain some observations of dependency of hydraulic conductivity in peats on pore water pressure. Consideration is also given to the effect on hydraulic conductivities of methane gas going into solution with increase in pore water pressure.     

Study of the air-earth electrical current density in Athens

In the present study, we examine the daily and annual variation of the air-earth current density in Athens for all weather as well as for fair weather for a 16-year period 1965–1980.The daily variation of the air-earth current density has a definite bimodal form while the annual variation has no definitive form but simply reaches its larger values during the summer months. There has also been a Fourier analysis of the daily variation.Furthermore, and for a 3-year period 1968–70, we present the mean daily and annual variation of the electric field, air-earth current density and total conductivity of the air. Based on these parameters we have estimated the conduction and the convection current and we have correlated them to the total (measured) current. In addition, we have estimated the values of the parameter, in order to test the fulfillment of Ohm's law in atmosphere.     

Complex and imitation Tectonites from the Kosciusko Pluton,snowy mountains,New South Wales

Rocks of Upper Precambrian age near Adelaide show evidence of two or more phases of deformation. The first phase has resulted in concentric and similar folds with an associated slaty cleavage. Structures of this phase are overprinted by folds with associated crenulation cleavage. Minor occurrences of later kink folds are also observed. The hypothesis that the first phase folds overprint very large folds not observable in the field is examined. The observed variation in the attitude of first phase folds could also have resulted from large scale inhomogeneities of strain.

1 “Torrens Group” is used in place of the “Torrensian Series” of Mawson and Sprigg (1950) at the suggestion of Daily (1963) since the Torrensian Series has an unwarranted time significance.

2 The scale of folds follows that of Weiss (1957). Macroscopic‐folds larger than a single outcrop. Mesoscopic‐folds on the scale of a hand specimen or single outcrop. Microscopic‐folds on the scale of a thin section.