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1.
Great strides have been made in understanding the upper part of the crust by in-situ logging in, and laboratory experiments on core recovered from super-deep bore-holes such as the KTB. These boreholes do not extend into the lower crust, and can contribute little to the elucidation of mechanisms that produce the high electrical conductivities that are commonly observed therein by magneto-telluric (MT) methods. Laboratory studies at simulated lower crustal conditions of temperature, pressure and saturation, on electrolyte saturated rocks thought to have been derived from the lower crust, have not been possible up until now due to their experimental difficulty. It is necessary to subject electrolyte-saturated rock samples to independently controlled confining and pore-fluid pressure, which implies that the rock be sleeved in some impermeable but deformable material, that can withstand the very high temperatures required. Metals are the only materials capable of being used, but these cause great difficulties for cell sealing and conductivity measurement. In this paper we describe recent breakthroughs in experimental work, specifically the development of two new types of sophisticated metal/ceramic seal, and a conductivity measurement technique that enables the measurement of saturated rock conductivity in the presence of a highly conducting metallic sleeve. The advances in experimental technique have enabled us to obtain data on the electrical conductivity of brine saturated basic, acidic and graphite-bearing rocks at lower crustal temperatures and raised pressures. These data have facilitated the comparison of MT derived crustal electrical conductivity profiles with profiles obtained from laboratory experiments for the first time. Initial modelling shows a good agreement between laboratory derived and MT derived profiles only if the mid-crust is composed of amphibolite pervaded by aqueous fluids, and the lower crust is composed of granulite that is saturated with aqueous fluids and/or contains interconnected grain surface films of graphite. The experimental data are consistent with a three layer crust consisting of an aqueous fluid saturated acidic uppermost layer, above an aqueous fluid saturated amphibolite mid-crust, and a granulite lowermost crust, which may or may not be saturated with aqueous fluids, but if not, requires the presence of an additional conduction mechanism such as conduction through thin graphite films. 相似文献
2.
Interrelations Between Thermal Conductivity and Other Physical Properties of Rocks: Experimental Data 总被引：2，自引：0，他引：2
Y. Popov V. Tertychnyi R. Romushkevich D. Korobkov J. Pohl 《Pure and Applied Geophysics》2003,160(5-6):1137-1161
— A new non-contact and non-destructive optical scanning instrument provided a large number of high-precision measurements of thermal conductivity tensor components in samples of sedimentary and impact rocks, as well as new insights into interrelations between thermal conductivity and other physical properties. More than 800 core samples (dry and fluid-saturated) of sedimentary rocks from different Russian oil-gas deposits and impact rocks from the well “Nördlingen 1973” drilled in the Ries impact structure (Germany) were studied using optical scanning technology. It was established that the thermal conductivity parallel to the stratification is more informative for petrophysical investigations than the thermal conductivity perpendicular to the layering. Different approaches were developed to estimate porosity, permeability, pore space geometry, and matrix thermal conductivity with a combination of thermal conductivity measurements in dry and fluid-saturated samples and mathematical modelling. These approaches allow prediction of the rock porosity and permeability and their spatial distribution along a well using thermal conductivity measurements performed with the optical scanning instrument directly applied to cores. Conditions and constraints for using Lichtenecker-Asaad's theoretical model for the estimation of porosity and thermal conductivity of sedimentary rocks were determined. A correlation between thermal conductivity and acoustic velocity, porosity, density, and electric resistivity of impact rocks was found for different rock types. New relationships between permeability, electrical and thermal conductivity found for sedimentary rocks are described. 相似文献
3.
— The success of the Soultz-sous-Forêts Hot-Dry-Rock project depends on the ability to maintain fluid circulation in a fractured granite. Fractures represent the main fluid pathways. To understand the behavior of this granite in respect to thermal fluid-rock interaction the important aspects are (1) the porous network around these fractures and (2) the thermal conductivity of the rock. This granite is altered and composed of different weathered facies. Variations of porosity and thermal conductivity take place in regard to the alteration and fracturing of the granite. Two types of porosity measurements were performed, mercury injection and water porosity on two samples sizes. The two methods give similar porosity values between 0.3% and 10%. Thermal conductivity measurements were performed in two perpendicular directions to look at anisotropy with two methods at different scale and value ranges from 2.3 to 3.9 W.m?1.K?1. Optical scanning provides us with a good knowledge of local increase of thermal conductivity due to sealed fracture or quartz-cemented matrix. The relationship between porosity and thermal conductivity is not obvious and has to be studied in details, and results show three cases: (1)?a relationship between conductivity and porosity (increase of conductivity with a decrease of porosity), (2)?a relationship between conductivity and sealed fractures (increase of conductivity related to an increase of fracture density), (3)?and a combination of the two previous ones. The results are carefully compared for different types of granite: alterated, fractured or both. These first results indicate that parameters such as thermal conductivity are linked to the porous medium, the structure and the mineralogy of the rock. 相似文献
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本文采用有限元方法研究含湿孔隙岩石的有效热导率,即随机划分网格并指定材料性质,建立三维含湿孔隙岩石的有限元模型,模型的上下表面施加不同的温度,侧面绝热,计算出总热流,然后结合上下表面的温度梯度计算出岩石的有效热导率.考虑到单个随机模型不一定具有代表性,对给定的孔隙率和饱和度均生成了200种矿物、水、空气随机分布的岩石模型,进行Monte Carlo实验和统计分析,统计分析结果与前人实验结果吻合良好.数值分析结果表明,孔隙岩石的有效热导率与岩石的孔隙率、饱和度、固体矿物组分及孔隙的分布情况有关,数值计算的误差随着网格数目的增加而减小.此有限元方法可以用来估算岩石的有效热导率,在已知组分性质的多矿物岩石物性计算方面有广阔应用前景. 相似文献
7.
Transport properties (permeability and electrical conductivity) have been measured at different hydrostatic pressure runs on 7 crystalline rocks (gneisses and amphibolites) sampled from the KTB drilling project. The decrease of permeability by pressure are compared with the pressure-dependent data of the electrical conductivity (formation factor) resulting from complex impedance measurements. According to the equivalent-channel model (ECM), there exists a linear relationship between these parameters by representing both properties on logarithmic scales. The results show that it is possible to extrapolate high-pressure permeability from low-pressure (< 60 MPa) permeability data by using the pressure-dependent electrical conductivity (up to 300 MPa). 相似文献
8.
电导率是表征岩石电学性质的重要物理参数,在地质资源勘查和测井解释等领域发挥着巨大作用.快速、准确地确定岩石电导率具有重要的理论和实践意义.作为近年来发展的一种岩石物理数值模拟工具,数字岩心技术在定量计算电导率等物性参数方面应用广泛.三维微观结构的准确获取是数字岩心技术计算岩石电导率的关键,但传统获取岩石三维微观结构的方法较为复杂费时.为了方便快速地通过数字岩心技术计算岩石的电导率,本文研究了岩石二维与三维数字岩心的电导率联系.我们基于微米级X射线CT扫描得到的三个砂岩样品的微观结构信息建立了三维数字岩心,并通过有限元法计算的三维数字岩心电导率与实验数据的对比验证数值计算方法的有效性.随后我们数字地扩展了岩石的孔隙,产生了较大孔隙度的三维数字岩心样本,在此基础上,计算了三维数字岩心和相应二维数字岩心的电导率,并通过Archie公式分别拟合了电导率与孔隙度之间的关系,得到了相应的胶结系数.结果表明,三维数字岩心的胶结系数小于二维数字岩心的胶结系数,且二者的比值与岩石实测孔隙度呈线性负相关关系.以该联系为纽带,通过二维图像快速计算得到的电导率与孔隙度关系,确定了三维数字岩心的电导率与孔隙度关系,并进一步通过三维数字岩心的孔隙度计算其电导率.该方法计算得到的人工砂岩样品的电导率与其三维数字岩心电导率相关系数高于96%,验证了基于二维图像的数字岩心电导率计算方法的有效性.本文的研究结果为快速、准确地计算岩石电导率提供了新的思路,在油气勘探开发中有广阔的应用前景. 相似文献
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Seismic driven probabilistic classification of reservoir facies for static reservoir modelling: a case history in the Barents Sea 总被引：2，自引：0，他引：2
Dario Grana Enrico Paparozzi Silvia Mancini Cristiano Tarchiani 《Geophysical Prospecting》2013,61(3):613-629
In this paper we present a case history of seismic reservoir characterization where we estimate the probability of facies from seismic data and simulate a set of reservoir models honouring seismically‐derived probabilistic information. In appraisal and development phases, seismic data have a key role in reservoir characterization and static reservoir modelling, as in most of the cases seismic data are the only information available far away from the wells. However seismic data do not provide any direct measurements of reservoir properties, which have then to be estimated as a solution of a joint inverse problem. For this reason, we show the application of a complete workflow for static reservoir modelling where seismic data are integrated to derive probability volumes of facies and reservoir properties to condition reservoir geostatistical simulations. The studied case is a clastic reservoir in the Barents Sea, where a complete data set of well logs from five wells and a set of partial‐stacked seismic data are available. The multi‐property workflow is based on seismic inversion, petrophysics and rock physics modelling. In particular, log‐facies are defined on the basis of sedimentological information, petrophysical properties and also their elastic response. The link between petrophysical and elastic attributes is preserved by introducing a rock‐physics model in the inversion methodology. Finally, the uncertainty in the reservoir model is represented by multiple geostatistical realizations. The main result of this workflow is a set of facies realizations and associated rock properties that honour, within a fixed tolerance, seismic and well log data and assess the uncertainty associated with reservoir modelling. 相似文献
10.
Common problems encountered during the determination of the thermal conductivities of tight sandstones are rock specimen-to-heat source contact and complicated sample preparation. An experimental technique using an electromagnetic heat source solves the direct contact problem between the heat source and the sample. Also, it simplifies the sample preparation and reduces the measurement time. A CO2 laser operating in a pulsed mode is used as a heat source with about 500 W output power. Thus, heat losses due to radiation and air convection are negligible. Unpolished penny-sized samples of tight sandstones are irradiated on one side and the temperature is measured on the opposite side. The temperature is recorded with 12-bit accuracy by a digital data acquisition system. Carbon black is used to give the samples a uniform absorption. The transient temperature data are acquired, processed, and interpreted with interactive computer programs. Transients for each sample can be stacked, to improve the signal-to-noise ratio, and normalized. The thermal conductivity is calculated from the rise portion of the transient using a ridge-regression type generalized linear inversion scheme. As many as 20 samples per hour can be measured with this simple but expensive set-up. In the long run, this means a reduction of laboratory expenses. In addition, the resolution of this method is superior to other variable-state measurement methods due to the real time controlled data acquisition and the numerical interpretation. 相似文献
11.
Time domain electromagnetic‐induced polarisation: extracting more induced polarisation information from grounded source time domain electromagnetic data 
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下载免费PDF全文 Electrical induced polarisation surveys are used to detect chargeable materials in the earth. For interpretation of time domain electrical‐induced polarisation data a common procedure is to first invert the direct current data (electric current on time) to recover conductivity and then invert the induced polarisation data (current off‐time) to recover chargeability. This direct current‐induced polarisation inversion procedure assumes that the off time data are free of secondary electromagnetic induction effects. To comply with this, early time data are often discarded or not recorded. For mid‐time data, an electromagnetic decoupling technique, which removes electromagnetic induction in the observations, needs to be implemented. Usually, responses from a half‐space or a layered earth are subtracted. Recent capability in three‐dimensional time domain electromagnetic forward modelling and inversion allows to revisit these procedures. In a Time domain electromagnetic‐induced polarisation survey, a high sampling rate allows early time channels of the electromagnetic data to be recorded. The recovery of chargeability then follows a three‐step workflow: (i) invert early time channel time domain electromagnetic data to recover the three‐dimensional conductivity; (ii) use that conductivity to compute the time domain electromagnetic response at later time channels and subtract this fundamental response from the observations to extract the induced polarisation responses, and (iii) invert the induced polarisation responses to recover a three‐dimensional chargeability. This workflow effectively removes electromagnetic induction effects in the observations and produces better chargeability and conductivity models compared with conventional approaches. In a synthetic example involving a gradient array, we show that the conductivity structure obtained from the early time channel data, which are usually discarded, is superior to that obtained from the steady state direct current voltages. This adds a further reason to collect these electromagnetic data. 相似文献
12.
Estimating thermal conductivity from core and well log data 总被引：1，自引：1，他引：0
The aim of the presented work was to introduce a method of estimating thermal conductivity using well log data. Many petrophysical properties of rocks can be determined both by laboratory measurements and well-logs. It is thus possible to apply geophysical data to empirical models based on relationships between laboratory measured parameters and derive continuous thermal conductivity values in well profiles. Laboratory measurements were conducted on 62 core samples of Meso-Paleozoic rocks from the Carpathian Foredeep. Mathematical models were derived using multiple regression and neural network methods. Geophysical data from a set of seven well logs: density, sonic, neutron, gamma ray, spectral gamma ray, caliper and resistivity were applied to the obtained models. Continuous thermal conductivity values were derived in three well profiles. Analysis of the obtained results shows good consistence between laboratory data and values predicted from well log data. 相似文献
13.
J. P. McGreevy 《地球表面变化过程与地形》1985,10(2):125-136
Four rock types (basalt, sandstone, granite, and chalk) are examined with respect to the maximum surface temperatures which they experience when subjected to similar conditions of exposure. Rock temperature measurements are reported for an urban environment and for two experimental situations in which an infrared lamp is used to simulate heating under cold and hot conditions. Differences in rock temperatures are discussed with reference to thermal rock properties (albedo, specific heat capacity, and thermal conductivity). Some natural situations are suggested in which thermal rock properties could conceivably play a role in determining the extent to which rocks would be affected by particular weathering processes. 相似文献
14.
查干凹陷是银根-额济纳旗盆地最具勘探潜力的凹陷, 但是查干凹陷及整个银根-额济纳旗盆地的大地热流研究仍为空白, 严重制约该盆地的油气资源的评价. 本文通过测试19口井107块岩芯的岩石热导率和岩石热导率原位校正, 利用协和平均公式计算得到查干凹陷各地层的岩石热导率大小; 并利用9口井的温度数据, 结合岩石热导率数据对查干凹陷的地温梯度和大地热流进行了计算. 研究结果表明查干凹陷具有构造稳定区和构造活动区之间的中温型地温场特征, 其平均地温梯度和大地热流分别为33.6℃/km, 74.5 mW/m2. 本文的研究成果为查干凹陷及银根-额济纳旗盆地油气资源评价提供地热参数. 相似文献
15.
Paul Morgan 《Earth and Planetary Science Letters》1975,26(2):253-262
A standard core analysis technique has been modified to estimate porosities from measurements on rock fragments. For the range of rocks tested, chip-determined fractional porosities were within ±0.025 of the values measured on solid-core samples. This has enabled thermal conductivity measurements on rock fragments to be corrected for the effect of porosity, yielding agreement with conductivity determinations on solid core generally to better than ± 10%. The application of this is illustrated by the determination of heat flow in a 300-m borehole in western Cyprus (latitude 34°54′N, longitude 32°34′E, elevation 82 m). A decrease in temperature gradient with depth is almost completely compensated for by increasing thermal conductivity, and the best value for heat flow at this site is 23 ± 4 mW m?2. 相似文献
16.
Todd H. Skaggs 《Advances in water resources》2011,34(10):1335-1342
Critical path analysis (CPA) is a method for estimating macroscopic transport coefficients of heterogeneous materials that are highly disordered at the micro-scale. Developed originally to model conduction in semiconductors, numerous researchers have noted that CPA might also have relevance to flow and transport processes in porous media. However, the results of several numerical investigations of critical path analysis on pore network models raise questions about the applicability of CPA to porous media. Among other things, these studies found that (i) in well-connected 3D networks, CPA predictions were inaccurate and became worse when heterogeneity was increased; and (ii) CPA could not fully explain the transport properties of 2D networks. To better understand the applicability of CPA to porous media, we made numerical computations of permeability and electrical conductivity on 2D and 3D networks with differing pore-size distributions and geometries. A new CPA model for the relationship between the permeability and electrical conductivity was found to be in good agreement with numerical data, and to be a significant improvement over a classical CPA model. In sufficiently disordered 3D networks, the new CPA prediction was within ±20% of the true value, and was nearly optimal in terms of minimizing the squared prediction errors across differing network configurations. The agreement of CPA predictions with 2D network computations was similarly good, although 2D networks are in general not well-suited for evaluating CPA. Numerical transport coefficients derived for regular 3D networks of slit-shaped pores were found to be in better agreement with experimental data from rock samples than were coefficients derived for networks of cylindrical pores. 相似文献
17.
An accurate prediction of the thermal conductivity of reservoir rocks in the subsurface is extremely important for a quantitative analysis of basin thermal history and hydrocarbon maturation. A model for calculating the thermal conductivity of reservoir rocks as a function of mineral composition, porosity, fluid type, and temperature has been developed based on fabric theory and experimental data. The study indicates that thermal conductivities of reservoir rocks are dependent on the volume fraction of components (minerals, porosity, and fluids), the temperature, and the fraction of series elements (FSE) which represents the way that the mineral components aggregate. The sensitivity test of the fabric model shows that quartz is the most sensitive mineral for the thermal conductivity of clastic rocks. The study results indicate that the FSE value is very critical. Different lithologies have different optimum FSE values because of different textures and sedimentary structures. The optimum FSE values are defined as those which result in the least error in the model computation of the thermal conductivity of the rocks. These values are 0.444 for water-saturated clay rocks, 0.498 for water-saturated sandstones, and 0.337 for water-saturated carbonates. Compared with the geometric mean model, the fabric model yields better results for the thermal conductivity, largely because the model parameters can be adjusted to satisfy different lithologies and to minimize the mean errors. The fabric model provides a good approach for estimating paleothermal conductivity in complex rock systems based on the mineral composition and pore fluid saturation of the rocks. 相似文献
18.
A conceptual model for describing effective saturation in fractured hard rock is presented. The fracture network and the rock matrix are considered as an equivalent continuum medium where each fracture is conceptualized as a porous medium of granular structure and the rock matrix is assumed to be impermeable. The proposed model is based on the representation of a rough‐walled fracture by an equivalent porous medium, which is described using classical constitutive models. A simple closed‐form equation for the effective saturation is obtained when the van Genuchten model is used to describe saturation inside fractures and fractal laws are assumed for both aperture and number of fractures. The relative hydraulic conductivity for the fractured rock is predicted from a simple relation derived by Liu and Bodvarsson. The proposed constitutive model contains three independent parameters, which may be obtained by fitting the proposed effective saturation curve to experimental data. Two of the model parameters have physical meaning and can be identified with the reciprocal of the air entry pressure values in the fractures of minimum and maximum apertures. Effective saturation and relative hydraulic conductivity curves match fairly well the simulated constitutive relations obtained by Liu and Bodvarsson. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
19.
Thermal diffusivity of rhyolite melt and rhyolite foam (70–80% porosity) has been measured using the radial heat transfer method. Cylindrical samples (length 50–55 mm, diameter 22 mm) of rhyolite melt and foam have been derived by heating samples of Little Glass Mountain obsidian. Using available data on heat capacity and density of rhyolite melt, the thermal conductivity of samples has been determined. The difference in thermal conductivity between rhyolite melt and foam at igneous temperatures ( 1000°C) is about one order of magnitude. The effect of thermal insulation of magmas due to vesiculation and foaming of the top layer is discussed in terms of the data obtained using a simple illustrative model of magma chamber convection. 相似文献