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1.
Measured groundwater temperatures in the surficial zone are dependent on the properties of porous media and vertical flow velocity. Sensitivity analyses, collinear diagnostics and an inverse numerical solution to the one-dimensional heat-transport equation are used to determine which parameters can be estimated from temperature measurements in the surficial zone. This is done for heat transport in the saturated zone considering a constant vertical flow velocity. The use of temperature profiles, temperature time-series and temperature envelopes are considered. There is an important difference between a conduction and a convection dominated system. Sensitivity analysis shows that temperature measurements are sensitive to effective thermal conductivity and heat capacity and are insensitive to effective porosity and thermal dispersivity. In a conduction dominated system, temperature is also insensitive for vertical velocity. Collinear diagnostics show that in a conduction dominated system, only the combination of heat capacity and effective thermal conductivity, the thermal diffusivity, can be derived. In a convection dominated system, both the vertical velocity and the effective thermal conductivity can, theoretically, be derived. 相似文献
2.
Free thermal convection and mixed convection are considered as potential mechanisms for mass and heat transport in sedimentary
basins. Mixed convection occurs when horizontal flows (forced convection) are superimposed on thermally driven flows. In cross
section, mixed convection is characterized by convection cells that migrate laterally in the direction of forced convective
flow. Two-dimensional finite-element simulations of variable-density groundwater flow and heat transport in a horizontal porous
layer were performed to determine critical mean Rayleigh numbers for the onset of free convection, using both isothermal and
semi-conductive boundaries. Additional simulations imposed a varying lateral fluid flux on the free-convection pattern. Results
from these experiments indicate that forced convection becomes dominant, completely eliminating buoyancy-driven circulation,
when the total forced-convection fluid flux exceeds the total flux possible due to free convection. Calculations of the thermal
rock alteration index (RAI=q·∇T) delineate the patterns of potential diagenesis produced by fluid movement through temperature gradients. Free convection
produces a distinct pattern of alternating positive and negative RAIs, whereas mixed convection produces a simpler layering
of positive and negative values and in general less diagenetic alteration.
Received, January 1999/Revised, June 1999/Accepted, July 1999 相似文献
3.
4.
This study aims to model temperature distributions in an aquifer thermal extraction (ATE) system that contains a single extraction well in a thin confined aquifer. The aquifer is bounded by hot dry rocks with different thermomechanical properties and thicknesses. Based on the heat convection–conduction equation, a mathematical model is developed to describe the spatial and temporal temperature distributions of the ATE systems. The mechanisms of heat transfer in the model involve horizontal convection and thermal conduction in the aquifer, and vertical thermal conduction in both rocks. A semi‐analytical solution in dimensionless form is developed using the Laplace transform technique and its corresponding time‐domain result is computed by the modified Crump method. In addition, the steady‐state solution is obtained by applying the final value theorem. The simulation results from the semi‐analytical solution indicate that the aquifer temperature distributions are affected by aquifer thickness, the thermomechanical properties of the aquifer and rocks, geothermal gradient, outer boundary temperatures of the rocks, extraction rate, and operating time. The present solution can be used as a preliminary tool for assessing heat extraction efficiency in ATE systems. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
5.
A modeling study was carried out to evaluate the influence of aquifer heterogeneity, as represented by geologic layering, on heat transport and storage in an aquifer thermal energy storage (ATES) system in Agassiz, British Columbia, Canada. Two 3D heat transport models were developed and calibrated using the flow and heat transport code FEFLOW including: a “non-layered” model domain with homogeneous hydraulic and thermal properties; and, a “layered” model domain with variable hydraulic and thermal properties assigned to discrete geological units to represent aquifer heterogeneity. The base model (non-layered) shows limited sensitivity for the ranges of all thermal and hydraulic properties expected at the site; the model is most sensitive to vertical anisotropy and hydraulic gradient. Simulated and observed temperatures within the wells reflect a combination of screen placement and layering, with inconsistencies largely explained by the lateral continuity of high permeability layers represented in the model. Simulation of heat injection, storage and recovery show preferential transport along high permeability layers, resulting in longitudinal plume distortion, and overall higher short-term storage efficiencies. 相似文献
6.
基于复合单元法,结合三维热传导-对流方程和“充填模型”,提出了裂隙岩体不稳定温度场的复合单元模型。该模型前处理简便快捷,计算网格生成时无需考虑裂隙的存在,网格剖分不受限制,随后利用复合单元前处理程序,依据裂隙的位置和方位将其自动离散在单元内。对常规热传导-对流方程进行自伴随性调整,应用变分原理,推导出裂隙岩体不稳定温度场的复合单元算法,该算法可分别计算出岩块子单元和裂隙的温度值,且可真实反映裂隙中水流与相邻岩块间的热能量交换规律。将复合单元数值模型计算的不稳定温度场结果与相应的实测数据进行对比分析可知,数值计算结果与实测数据基本一致,验证了裂隙岩体不稳定温度场复合单元算法的可靠性与有效性。算例分析表明,裂隙中水流与相邻岩块间有明显的热传导和热对流作用。 相似文献
7.
封闭条件下抛石路堤降温效果及机理的试验研究 总被引：22，自引：13，他引：9
在多年冻土地区道路工程的修筑与维护中, 如何保证多年冻土不退化所采取措施的长期可靠度问题日益为人们所关注. 通过室内试验研究了实际工程中半开放半封闭抛石路堤受到风沙或积雪填埋后,在不同温度变幅条件下的降温效果. 实验结果发现: 在满足一定厚度时, 封闭条件下的块石层仍具有良好的降温效果, 具有可变等效导热系数的特性, 在实验中充分体现了"热二极管效应". 在外界温度变幅较大的条件下, 降温速度和降温效率均大于温度变幅较小的情况. 通过对块石层顶底温差与其顶部温度变化关系, 以及块石层内温度场特征的分析, 证实了封闭块石层内自然对流的真实存在和对流的运动发展趋势. 试验结果为抛石路堤降温的长期可靠性提供了依据. 相似文献
8.
D. Mottaghy R. Schellschmidt Y.A. Popov C. Clauser I.T. Kukkonen G. Nover S. Milanovsky R.A. Romushkevich 《Tectonophysics》2005,401(1-2):119-142
We present new heat flow values and other geothermal data in the upper crystalline crust in the immediate vicinity of the 12.4-km deep Kola super-deep borehole, NW Russia. Our results show a systematic vertical increase in geothermal gradient and heat flow density as deep as we could measure (1.6 km). Our results confirm earlier results on vertical heat flow trends of in the uppermost part of the Kola super-deep hole, and imply that the thermal regime is not in steady-state conductive conditions. In an area of 3-km × 5-km measurements were performed in 1–2-km deep boreholes surrounding the Kola super-deep hole and on core samples from these holes. Temperature logs are available from 36 holes. Core data exists from 23 boreholes with a total length of 11.5 km at a vertical resolution of 10 m. We carried out a very detailed study on thermal conductivity with regard to anisotropy, inhomogeneity and temperature dependence. Tensor components of thermal conductivity were determined on 1375 core samples from 21 boreholes in 3400 measurements. Additionally, we measured specific heat capacity, heat generation rate, density, porosity, and permeability on selected subsets of core samples. Heat flow from 19 boreholes varies between 31 and 45 mW m−2 with an average value of 38 mW m−2. In most boreholes the vertical heat flow profiles show a considerable variation with depth. This is consistent with observations in the upper part of the Kola super-deep borehole. We conclude that this variation is not caused by technical operations but reflects a natural process. It is considered to be due to a combination of advective, structural and paleoclimatic effects. Preliminary 3-D numerical modeling of heat and flow in the study area provides an indication of relative contributions of each of these factors: advective heat transfer turns out to have a major influence on the vertical variation of heat flow, although transient changes in surface temperature may also cause a significant variation. Heterogeneity of the rocks in the study area is less important. 相似文献
9.
为保证地热资源可持续开发利用,深入开展回灌工程采灌井合理井距研究、防止短时间内发生热突破是地热领域的重大关切。本文根据全井段测温结果,对砂岩热储不同采灌工程地温场变化特征进行了分析。研究表明：随着回灌年度的增加,冷水范围越来越大,热量对回灌井有效补给路径变长,回灌井热储段温度曲线波动幅度越小;当采灌井距较小、底部温度相对较低时,回灌冷水会对开采井造成影响,致使开采井热储温度降低;在回灌初期热对流在热量恢复中占主导作用,随着回灌年数的增加,冷水范围越来越大,热对流对温度场恢复的作用逐渐减弱,周边和相邻隔水层热传导在温度恢复中的作用越来越显著,温度恢复越来越慢,因此,在规模化回灌条件下,热突破是必然的。 相似文献
10.
壳-幔动力学与活化构造(地洼)理论 总被引：9，自引：9，他引：0
陈胜早 《大地构造与成矿学》2005,29(1):87-98
壳-幔动力学是地球内部物理学和大地构造演化的重要研究方向之一。本文从地球物理角度出发,以物理概念和数学描述相结合的定量方式,对陈国达院士生前所创建的活化构造(地洼)理论研究中的某些地球深部动力学问题进行了较系统的综合评述和探讨。主要论题包括岩石圈的性质与物理学、地幔流变学、重力与均衡理论、地球的温度和热传递,诸如热传导、物质的物理运动所引起的热传输、地球内部的热对流及地幔柱的形成和作用等。作者特别强调了构造演化的定量分析问题,如热时间常数、热应力与其它力源、水平运动与垂直运动的关系,以及地壳断裂作用。岩石圈的构造作用与演化是与深部热运动有关的水平 (压缩和扩张)应力和由地壳厚度差异所导致的垂直应力差的共同结果。热应力的构造意义主要表现为短时间尺度的脆性断裂或柔性应变松弛过程。局部对流机制对活化构造(地洼)研究值得重视。 相似文献
11.
Yu. L. Rebetskii 《Doklady Earth Sciences》2011,440(1):1328-1333
The set of equations for the problem of thermal-gravitational convection accounts for compressibility of solid bodies, which
changes for elementary volumes moving during convection process in fields of the initial temperature and the initial gravitational
stress pattern for rheology of an elastic-viscous Maxwell body. It was shown that equations of momentum conservation in the
vertical direction and heat transfer for steady convection differ from the equation for incompressible liquid by terms containing
the rate of elastic volume change and the connected rate of heat change. It was established that an additional term in the
momentum conservation equation defines a new class of the instable state of a solid body, which is able to form huge deformations
at the expense of plasticity and creep at large segments of time—flow in the field of gravity force—instability of the gravitational
stress pattern of elastic-plastic body. Analysis of different boundary conditions for which this instability can be realized
in the form of convective cells showed that the convection rate is totally defined by reconstruction processes of vertical
stresses on horizontal boundaries close to the initial gravitation pattern. Alignment process of these stresses can be provided
not only by erosion and denudation processes occurring on the Earth’s surface, but also by processes on the inner boundaries
of the tectonosphere which provide isostasy in the mantle. 相似文献
12.
中生代、新生代时期地壳剧烈运动将胶东半岛划分为胶北隆起、胶莱凹陷、胶南-威海隆起三大构造单元,其中隆起山地区广泛分布花岗岩、变质岩,凹陷盆地区主要分布砂岩沉积地层,胶北隆起区与威海隆起区相对于胶莱凹陷盆地区具有更高的大地热流值.为系统分析胶东半岛大地热流值分布特征及其形成机理,本文在分析胶东半岛构造-热发展史、地热地质背景、地温场分布、岩石热导率、钻孔岩性与测温数据、地热流体化学成分等基础上,发现胶东半岛地热资源均为断裂构造控制类型的中低温对流型,其热源主要为三元聚热:导热断裂带水热对流、大地热流传导、地下水运移传导-对流;构造分布、岩石热物性、地热热储分布、地下水活动等是影响地温场分布的主要因素.针对胶东半岛地温场特征及其控制因素,提出了适合该地区的隆起-凹陷分流聚热模式与概念模型,即隆起山地区岩性以导热率、渗透率相对较高的侵入岩、变质岩为主,凹陷盆地区岩性以导热率、渗透率相对较低的砂岩为主,低导热率、低渗透率的凹陷区底部更像是一个相对隔热、隔水的顶板,使得来自地壳深部的大地热流及携带热量的流体、气体等在上涌的过程中在凹陷区的底部发生折射与再分配,从而导致热流在隆起山地区的底部形成一个温度相对更高的聚热区,反映在地表即是隆起山地区相对凹陷盆地区具有更高的大地热流值,特别隆起山地区轴部位置为热流值最高的区域,高热流值区域分布形态呈NE、NNE向分布,基本与胶东半岛NE、NNE向的深大断裂走向一致,该模式的提出可以更好地为胶东地区的地热资源勘探提供指导方向. 相似文献
13.
针对高放射性核废物地下处置库近场饱和裂隙岩体环境,提出一种由分布热源、饱和单裂隙和两侧无限大岩石构成的三维水流-传热简化模型,建立了控制微分方程和基于拉氏变换域格林函数的积分方程;采用矩形单元把裂隙面域离散化,利用极坐标下的解析方法计算包含奇点的单元积分,利用数值方法计算分布热源和不包含奇点的单元积分,建立拉氏变换域的线性代数方程组,求解后,利用拉氏数值逆变换,计算任意时刻裂隙水和岩石的温度分布。对两个无内热源、流场确定的计算模型进行了计算,与仅考虑岩石沿裂隙面法向一维热传导的解析解进行了对比。计算分析了分布热源作用下饱和单裂隙岩体的三维水流-传热特征及其对裂隙水流速、岩石热传导系数和热源热流集度的敏感度。计算结果表明：与直接采用高斯数值积分相比,提出的解析法奇异积分精度较高;就裂隙水温度而言,单裂隙岩体三维水流-传热半解析计算方法与解析法得到的结果基本一致,但由于半解析计算方法考虑了岩石的三维热传导,使得裂隙水的上游温度较低,而下游温度较高;无分布热源作用时,岩石热传导系数越大,裂隙水温度越低;裂隙水流速越大,裂隙进水温度对裂隙水和岩石温度分布的影响越明显;由于受到裂隙水流动传热的作用,分布热源对裂隙水温度和岩石温度的影响在裂隙水流的下游区域比较显著。 相似文献
14.
边界条件对碎石层降温效果及机理的影响 总被引：22，自引：14，他引：8
对平均粒径为22.1 cm, 厚度1.3 m, 边界为开放和封闭的碎石层进行了一系列的实验. 从环境温度为最高和最低时刻封闭碎石层内的温度和速度分布可知: 当碎石层上表面温度低于下表面时,碎石层自下向上的散热由空气对流和碎石间的热传导来完成; 当上表面温度高于下表面时, 自上向下传递的热量由碎石接触面间的热传导完成, 此时, 由于其内部的空气几乎静止, 能阻隔热量的传入, 因此封闭边界的碎石层具有热半导体特性. 而开放边界的碎石层, 当平均温度为 0.5℃的空气从上表面吹过时, 碎石体内的热量传递主要是靠强迫对流来完成, 热半导体效果不明显, 不利于使其下面的冻土降温. 相似文献
15.
A distinct feature of the world-class Mount Isa copper system is the presence of a massive silica body enveloping the chalcopyrite ore body in the Urquhart shale. Because silicification may be genetically linked to the copper mineralization, it is important to understand its formation. It can be shown by numerical simulations of reactive transport processes that both hydraulic head and buoyancy driven flow are capable of generating silicification patterns similar to the field example. Considering the physical conditions required to form the observed patterns we suggest, however, that head-driven flow rather than free thermal convection produced the silica body. Free convection requires very special conditions and only one of several possible scenarios reproduces the observed silicification whereas any of the tested forced flux scenario is capable of doing so. 相似文献
16.
采暖尾水回灌对砂岩热储地温场的影响
——以鲁北地区为例 总被引：1，自引：0，他引：1
为保证地热资源可持续开发利用,深入开展回灌工程采灌井合理井距研究、防止短时间内发生热突破是地热领域的重大关切。本文根据全井段测温结果,对砂岩热储不同采灌工程地温场变化特征进行了分析。研究表明：随着回灌年度的增加,冷水范围越来越大,热量对回灌井有效补给路径变长,回灌井热储段温度曲线波动幅度越小;当采灌井距较小、底部温度相对较低时,回灌冷水会对开采井造成影响,致使开采井热储温度降低;在回灌初期热对流在热量恢复中占主导作用,随着回灌年数的增加,冷水范围越来越大,热对流对温度场恢复的作用逐渐减弱,周边和相邻隔水层热传导在温度恢复中的作用越来越显著,温度恢复越来越慢,因此,在规模化回灌条件下,热突破是必然的。 相似文献
17.
We conduct a theoretical analysis of steady‐state heat transfer problems through mid‐crustal vertical cracks with upward throughflow in hydrothermal systems. In particular, we derive analytical solutions for both the far field and near field of the system. In order to investigate the contribution of the forced advection to the total temperature of the system, two concepts, namely the critical Peclet number and the critical permeability of the system, have been presented and discussed in this paper. The analytical solution for the far field of the system indicates that if the pore‐fluid pressure gradient in the crust is lithostatic, the critical permeability of the system can be used to determine whether or not the contribution of the forced advection to the total temperature of the system is negligible. Otherwise, the critical Peclet number should be used. For a crust of moderate thickness, the critical permeability is of the order of magnitude of 10?20 m2, under which heat conduction is the overwhelming mechanism to transfer heat energy, even though the pore‐fluid pressure gradient in the crust is lithostatic. Furthermore, the lower bound analytical solution for the near field of the system demonstrates that the permeable vertical cracks in the middle crust can efficiently transfer heat energy from the lower crust to the upper crust of the Earth. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
18.
《Russian Geology and Geophysics》2014,55(7):801-811
The structure of mantle convection and spatial fields of superlitho static pressure and vertical and horizontal stresses in the Earth’s mantle are studied in a 2D numerical model with non-Newtonian viscosity and heat sources. The model demonstrates a jump-like motion of subduction zones and reveals abrupt changes in the stress fields depending on the stage of slab detachment. The stresses decrease dramatically in the areas without slabs. The horizontal stresses oxx, superlitho static pressure, and vertical stresses ozz in the part of the mantle lacking intense near-vertical flows are approximately equal, varying within ± 6, ± 8, and ± 10 MPa, respectively. However, these fields are stronger in the areas of descending slabs, where the values of the above parameters are about an order of magnitude higher (± 50 MPa).This result agrees with the current views of the oceanic slabs as the most important gent of mantle convection. We have found significant differences among the oxx, ozz, and pressure fields. The pressure field reveals both the vertical and horizontal features of slabs and plumes, clearly showing their long thermal conduits with broader heads. The distributions of oxx are sensitive to the near-horizontal parts of the flows, whereas the ozz fields reveal mainly their vertical substructures. The model shows the presence of relatively cold remnants of slabs in the lower mantle above the thermal boundary layer. Numerous hot plumes penetrating through these high-viscosity remnants, as well as the new descending slabs, induce intense stress fields in the lower mantle, which are strongly inhomogeneous in space and time. 相似文献
19.
G. S. Bhat 《Journal of Earth System Science》2003,112(2):131-146
This paper describes the near surface characteristics and vertical variations based on the observations made at 17.5‡N and
89‡E from ORV Sagar Kanya in the north Bay of Bengal during the Bay of Bengal Monsoon Experiment (BOBMEX) carried out in July–August
1999. BOBMEX captured both the active and weak phases of convection. SST remained above the convection threshold throughout
the BOBMEX. While the response of the SST to atmospheric forcing was clearly observed, the response of the atmosphere to SST
changes was not clear. SST decreased during periods of large scale precipitation, and increased during a weak phase of convection.
It is shown that the latent heat flux at comparable wind speeds was about 25–50% lower over the Bay during BOBMEX compared
to that over the Indian Ocean during other seasons and tropical west Pacific. On the other hand, the largest variations in
the surface daily net heat flux are observed over the Bay during BOBMEX. SST predicted using observed surface fluxes showed
that 1-D heat balance model works sometime but not always, and horizontal advection is important. The high resolution Vaisala
radiosondes launched during BOBMEX could clearly bring out the changes in the vertical structure of the atmosphere between
active and weak phases of convection. Convective Available Potential Energy of the surface air decreased by 2–3 kJ kg-1 following convection, and recovered in a time period of one or two days. The mid tropospheric relative humidity and water
vapor content, and wind direction show the major changes between the active and weak phases of convection. 相似文献
20.
沧东断裂是华北平原区一条规模较大的隐伏断裂,经历了中、新生代两个裂陷旋回,一直为地热地质工作者所关注。人工地震表明:沧东断裂是一空间构造形态上陡下缓、走向北东、北部边界已沿至蓟运河断裂附近的大型拆离断裂。以水文地质理论为基础,对沧东断裂附近地热流体的水化学场、温度场特征的研究表明:沧东断裂在下部并不具备控制天津地热热源的构造条件,但断裂上部却具有明显的将深部高位热能以热对流形式向浅部传导的特征;在水力传导方面,除局部地段稍弱外,总体上沧东断裂带在水平和垂直方向上有较强的导水能力。 相似文献