Thermal Properties Of Rocks Research Articles

ISRM Suggested Methods for Determining Thermal Properties of Rocks from Laboratory Tests at Atmospheric Pressure

ISRM Suggested Methods for Determining Thermal Properties of Rocks from Laboratory Tests at Atmospheric Pressure

Thermomechanical controls on magma supply and volcanic deformation: application to Aira caldera, Japan.

Ground deformation often precedes volcanic eruptions, and results from complex interactions between source processes and the thermomechanical behaviour of surrounding rocks. Previous models aiming to constrain source processes were unable to include realistic mechanical and thermal rock properties, and the role of thermomechanical heterogeneity in magma accumulation was unclear. Here we show how spatio-temporal deformation and magma reservoir evolution are fundamentally controlled by three-dimensional thermomechanical heterogeneity. Using the example of continued inflation at Aira caldera, Japan, we demonstrate that magma is accumulating faster than it can be erupted, and the current uplift is approaching the level inferred prior to the violent 1914 Plinian eruption. Magma storage conditions coincide with estimates for the caldera-forming reservoir ~29,000 years ago, and the inferred magma supply rate indicates a ~130-year timeframe to amass enough magma to feed a future 1914-sized eruption. These new inferences are important for eruption forecasting and risk mitigation, and have significant implications for the interpretations of volcanic deformation worldwide.

울릉도 산출 암석의 열물성 자료를 이용한 울릉도 지열 성인에 대한 열전도 수치모델링 연구

울릉도 산출 암석의 열물성 자료를 이용한 울릉도 지열 성인에 대한 열전도 수치모델링 연구

Improving the temperature predictions of subsurface thermal models by using high-quality input data. Part 1: Uncertainty analysis of the thermal-conductivity parameterization

The subsurface temperature field and the geothermal conditions in sedimentary basins are frequently examined by using numerical thermal models. For those models, detailed knowledge of rock thermal properties are paramount for a reliable parameterization of layer properties and boundary conditions. Despite the state-of-the-art in other research fields (e.g. hydrogeological ground-water models) where the spatial permeability variations within geological layers is often considered, parameterization of the major rock thermal properties (in particular thermal conductivity, to minor extent radiogenic heat production and specific heat capacity) is almost always conducted by applying constant parameters for each modelled layer. Moreover, initial parameter values are usually obtained from only few core measurements and/or literature values, which raise questions for their representativeness. Only some rare studies have considered detailed lithological composition or well log information, still with constant layer properties.This study presents a thermal-modelling scenario analysis in which we demonstrate how the use of both different parameter input type (from literature, lithology and well logs) and parameter input style (constant or spatially varying layer values) affects model temperature predictions in sedimentary basins. It is a case study located in the Danish-German border region at the northern margin of the North German Basin. To conduct the scenario analysis, rock thermal properties are determined from lithological descriptions and standard petrophysical well logs for several boreholes in the area of study. Statistical values of rock thermal properties are derived for each geological formation at each well location and, furthermore, for the entire dataset. The thermal model is validated against known observed temperatures of good quality.Results clearly show that the use of location-specific well-log derived rock thermal properties and the integration of laterally varying input data (reflecting changes of lithofacies) significantly improves the temperature prediction. The parameterization from boreholes always prevails over the parameterization based on literature values, and it allows for reducing uncertainty of model temperatures by up to 80%.

Improving the temperature predictions of subsurface thermal models by using high-quality input data. Part 2: A case study from the Danish-German border region

We present a 3D numerical crustal temperature model and analyse the present-day conductive thermal field of the Danish-German border region. The model region covers the northernmost part of the North German Basin, a transition zone between the deep-reaching sedimentary rocks of the Glückstadt Graben (including complex salt structures) and the shallow crystalline basement of the Ringkøbing-Fyn High. The modelling approach is novel as it implements for the first time a comprehensive analysis of well-log data on a regional modelling scale. Those logs were used both to derive the spatial distribution of rock thermal conductivity across the study area, and to calculate heat flow values. New values of terrestrial surface heat flow are reported for eight deep boreholes in the North German Basin ranging from 72 to 84mW/m2 with a mean of 80±5mW/m2. The values are computed from continuous temperature logs, carefully corrected BHT values, drill-stem tests and well-log derived rock thermal properties (thermal conductivity, radiogenic heat production) and were included in the setup of the numerical lower boundary conditions. New surface heat flow is up to 20mW/m2 higher than low values reported in some previous studies for this region. Heat flow from the mantle is 33–40mW/m2.The model temperature predictions are validated against 59 temperature observations from 24 wells. The prediction uncertainties between observed and modelled temperatures at deep borehole sites are small (rms=3.5°C, ame=2.1°C). Pronounced lateral temperature variations are predicted and found to be caused mainly by complex geological structures, including a large amount of salt structures and marked lateral variations in the thickness of basin sediments. The associated variations in rock thermal conductivity generate significant variations in model heat flow and large variations in temperature gradients.With regard to the utilization of geothermal energy, the Rhaetian and the Middle Buntsandstein sandstone reservoirs are found with temperatures within the range of 40–80°C, suitable for low enthalpy heating purposes, in most of the area and locally also with higher temperatures. Temperatures above 120°C, of interest for the production of electricity, are observed only in the very southeastern part of the study area.

Measurement and analysis of thermal properties of rocks for the compilation of geothermal maps of Cyprus

Previous studies in Cyprus classified the island in the category of low enthalpy with high potentials in the usage of geothermal energy for space air-conditioning. Due to the little existing information about the underground thermal properties, an extended geological sampling has been carried out on the island. Measurements of thermal properties have been performed in the laboratory at room temperature for all the collected samples both in their dry and water-saturated state. The impact on thermal conductivity of water in samples, the mineralogical composition, and the geological age of samples have been the objectives of the current study.Laboratory results of each rock type in Cyprus are found within certain ranges for each thermo-physical property as follows. Thermal conductivity values for dry rock samples vary between 0.4 and 4.2 W m−1 K−1, thermal diffusivity values range between 0.3 and 1.9 × 10−6 m2 s−1 and specific heat capacity values range from 0.5 to 1.5 J K−1 kg−1. Results also show that thermal conductivity and thermal diffusivity under moisture conditions increase for most of the lythotypes. The notable exception is Gypsum (Kalavaso Formation), which exhibits higher thermal response under dry conditions.Measured thermal properties also present a difference between thermal properties of the lithologies of the Troodos Ophiolite and the Circum Troodos Sedimentary Succession in Cyprus. Mean values of thermal conductivity and thermal diffusivity for dry samples and water-saturated samples have higher values for the lithologies of the Troodos Ophiolite than measured values for the lithologies of the Circum Troodos Sedimentary Succession, mostly due to their mineralogical composition.Moreover, the geological age of a lithology has been shown to affect its thermal response. Thermal conductivity of reef limestone and calcarenite rocks increases with the geological age of the lithology.In order to understand and visualize all measured data the Thermal Conductivity and the Thermal Diffusivity Maps of Cyprus have been compiled with the use of a Geographic Information System (GIS) to be available to engineers as a powerful tool for use in the design of thermal engineering systems. From the obtained maps Troodos Ophiolite can be visualized as a separate part by having the highest values.

Estimation of subsurface formation temperature in the Tarim Basin, northwest China: implications for hydrocarbon generation and preservation

Subsurface formation temperature in the Tarim Basin, northwest China, is vital for assessment of hydrocarbon generation and preservation, and of geothermal energy potential. However, it has not previously been well understood, due to poor data coverage and a lack of highly accurate temperature data. Here, we combined recently acquired steady-state temperature logging data with drill stem test temperature data and measured rock thermal properties, to investigate the geothermal regime and estimate the subsurface formation temperature at depth in the range of 1000–5000 m, together with temperatures at the lower boundary of each of four major Lower Paleozoic marine source rocks buried in this basin. Results show that heat flow of the Tarim Basin ranges between 26.2 and 66.1 mW/m2, with a mean of 42.5 ± 7.6 mW/m2; the geothermal gradient at depth of 3000 m varies from 14.9 to 30.2 °C/km, with a mean of 20.7 ± 2.9 °C/km. Formation temperature estimated at the depth of 1000 m is between 29 and 41 °C, with a mean of 35 °C, while 63–100 °C is for the temperature at the depth of 3000 m with a mean of 82 °C. Temperature at 5000 m ranges from 97 to 160 °C, with a mean of 129 °C. Generally spatial patterns of the subsurface formation temperature at depth are basically similar, characterized by higher temperatures in the uplift areas and lower temperatures in the sags, which indicates the influence of basement structure and lateral variations in thermal properties on the geotemperature field. Using temperature to identify the oil window in the source rocks, most of the uplifted areas in the basin are under favorable condition for oil generation and/or preservation, whereas the sags with thick sediments are favorable for gas generation and/or preservation. We conclude that relatively low present-day geothermal regime and large burial depth of the source rocks in the Tarim Basin are favorable for hydrocarbon generation and preservation. In addition, it is found that the oil and gas fields discovered in the Tarim Basin are usually associated with relatively high-temperature anomalies, and the upward migration and accumulation of hot geofluids along faults as conduit from below could explain this coincidence. Accordingly, this thermal anomaly could be indicative of hydrocarbon exploration targets in the basin.

Thermoelastic properties of the Rotokawa Andesite: A geothermal reservoir constraint

Knowledge of the thermal properties of geothermal reservoir rocks is essential to constraining important engineering concerns such as wellbore stability, reservoir forecasting and stimulation procedures. The thermo-mechanical evolution of geological material is also important to assess when considering natural processes such as magmatic dyke propagation, contact metamorphism and magma/lava emplacement and cooling effects. To better constrain these properties in the geothermal reservoir, thermal measurements were carried out on core samples from production wells drilled in the Rotokawa Andesite geothermal reservoir, located in the Taupo Volcanic Zone, New Zealand. Linear thermal expansion testing, thermogravimetric analysis, and differential scanning calorimetry were used, employing experimental heating rates of 2, 5 and 20°C/min. Thermal property analyses can elucidate whether thermal expansion values measured under varied heating (and cooling) rates are rate dependent and if thermo-chemical reactions influence the resultant expansivity. Measured thermal expansion coefficients of the Rotokawa Andesite are shown not to be heating rate dependent. We have also found that significant thermochemical reactions occur during heating above 500°C resulting in non-reversible changes to the thermomechanical properties. The combined thermogravimetric, calorimetric and thermomechanical analysis allows insight to the reactions occurring and how the thermomechanical properties are affected at high temperature. We incorporated results of tensile strength testing on the Rotokawa Andesite to apply our thermal property measurements to a one-dimensional thermal stress model. The developed model provides a failure criterion for the Rotokawa Andesite under thermal stress. The importance of this study is to further understand the critical heating and cooling rates at which thermal stress may cause cracking within the Rotokawa reservoir. Thermal cracking in the reservoir can be beneficial in reservoir stimulation procedures, but also poses potential risk to wellbore stability, so constraining the conditions at which this can occur can be beneficial to resource utilization.

Surface heat flow and lithosphere thermal structure of the Rhenohercynian Zone in the greater Luxembourg region

Comprehensive knowledge of surface heat flow and subsurface temperature distribution is indispensable for the interpretation and quantification of crustal/mantle processes as well as for the evaluation of the geothermal potential of an area. In cases where subsurface temperature data are sparse, thermal modeling may be used as a tool for inferring the geothermal resource at depth but requires profound structural, geological, and petrophysical input data. The study area encompasses the Trier–Luxembourg Basin and the western realm of the Rhenish Massif, itself subdivided into the Ardennes region in the west as well as the Eifel and Hunsrück regions in the east. For the study area, 2-D steady-state and conductive thermal models were established based on geological models of lithosphere-scale which were parameterized using thermal rock properties including thermal conductivity, radiogenic heat production, and density. The thermal models are constrained by surface heat flow (qs) and the geophysically-estimated depth of the lithosphere–asthenosphere boundary (LAB). A qs of 75±7 (2σ)mWm−2 was determined in the area. A LAB depth of 100km, as seismically derived for the Ardennes, provides the best fit with the measured qs. Modeled temperatures are in the range of 120–125°C at 5km depth and of 600–650°C at the Moho, respectively. The mantle heat flow amounts to ∼40mWm−2. Possible thermal consequences of the 10–20Ma old Eifel plume, which caused elevation of the LAB to 50–60km depth, were modeled in a steady-state thermal scenario resulting in a qs of 91mWm−2 in the Eifel region. Available qs values (65–80mWm−2) are significantly lower and do indicate that the plume-related heating has not yet reached the surface in its entirety.

The influence of gravel on the ambient temperature of power substations

This paper examines the role of gravel in the heating process of substation environments. The choice of the material applied to the electric energy substation surface level can influence temperature changes in equipment. Ambient temperature is an important parameter used to define how many years a transformer will last when subjected to a load curve, under normal and emergency operation conditions. This paper shows that the ambient temperature of 30°C, suggested in IEEE C 57.91 standard for calculating transformer's loading depending on the desired equipment life span is underestimated. There are differences in ambient temperature on surfaces when applying different rocks on the soil surface substations. In terms of the resistivity, some rocks have higher values than others when the drain systems fail to drain all the rainwater to the soil. Two field tests were performed, one in the 345kV/138kV Jacarepagua Substation in Rio de Janeiro, and the other in the Substation of Foz do Iguaçu in the state of Paraná, where measurements were performed at three locations: switchyard of 600kV direct current – DC, 500kV and 750kV alternating current – AC. Laboratory tests of thermal and electrical properties of rocks typically used to cover the ground of substations were also performed. This paper presents some consideration of drainage properties.

Thermal front propagation in variable aperture fracture–matrix system: A numerical study

A numerical study on the effect of complex fracture aperture geometry on propagation of thermal front in a coupled single fracture–matrix system has been carried out. Sinusoidal and logarithmic functions have been used to capture the variation in fracture aperture. Modifications have been made to existing coupled partial differential governing equations to consider the variation of fracture aperture. Effect of temperature on the thermal and physical properties of rock have been incorporated. A fully implicit finite difference scheme has been used to discretize the coupled governing equations. Thermal convection, dispersion and conduction are the major transport processes within fracture, while conduction is the major transport process within rock matrix. The results suggest that variation of fracture aperture increases the heat transfer rate at the fracture–matrix interface. Sensitivity analysis on rock thermal conductivity and fracture aperture have been carried out. The results suggest that the heat transfer from rock matrix to fracture for the case of the parallel plate model is greatly dependent on the rock thermal conductivity (λ m) as compared to variable aperture model. Further, the thermal front propagation for both parallel plate model and variable aperture model is sensitive to changes in fracture aperture. The heat transfer rate at the interface is greater at smaller fracture apertures and decreases with increase in aperture.

Relationship of the thermal conductivity of rocks in the Komsomol’sk ore district (Khabarovsk Territory) with minerageny and metasomatism

Statistical data are given on the thermal conductivity of rocks in the Komsomol’sk ore district (Khabarovsk Territory). The regularities of variations in the thermal-conductivity and thermal-inhomogeneity factors of the studied types of rocks are considered in relation to their mineral composition, texture, structure, and degree of metasomatic alteration. Thermophysical sections of the studied mineralized zones are presented. The conclusion is substantiated that the thermal properties of rocks are highly informative and detailed thermophysical studies of sections might be useful for their lithological subdivision.© 2015, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

고온 조건하 암석의 열적·역학적 물성에 대한 연구현황

본 기술보고서에서는 현재까지 발표된 국내외 70여 편의 주요 연구들을 토대로 고온 조건하 암석의 열적 역학적 물성에 대한 실험 데이터를 수집하여 요약 제시하였다. 대부분 특정 암석에 대해 일회성으로 보고되었던 선행연구들의 실험 결과를 보다 체계적으로 통합하여 제시함으로써 향후 열적 환경에 건설되는 암반구조물의 타당성 조사단계 및 초기 설계단계에서 이들의 활용성을 제고하고자 하였다. In this technical report we summarize the observational data on thermal and mechanical properties of rocks reported by over 70 best published papers. The experimental results reported individually are integrated and presented in tables and figures here, which will provide fundamental data to fairly determine and evaluate the rock properties at the initial design stage of underground structures exposed to high temperature environment.

Numerical model of the Habanero geothermal reservoir, Australia

A TOUGH2 reservoir model has been developed for the Habanero enhanced geothermal system (EGS), located in the Cooper Basin, Australia. The reservoir, interpreted to be the sub-horizontal Habanero fault, was defined by the extent of the stimulated seismic cloud. A 1D natural state model was used first to calibrate the rock thermal properties, heat generation and the heat flux at the base of the model. The temperature distribution was matched against measured down-hole data from well Habanero 1. A 3D model was then developed with 9 horizontal layers and aligned along an impermeable eastern boundary fault. Gravity potentially plays an important role so the model was tilted to the west-south-west. Since the fine 72,000 cell model only extends to 20km2 whilst the reservoir rock (Innamincka Granite) extends to over ∼1000km2, Dirichlet boundary condition (large block volumes) was used for the sides with closed boundaries at the top and bottom. These large cells simulate the extension of the reservoir beyond the limited dimensions of the basic model. The permeability of the stimulated and mud damaged zones was calibrated using stable closed-loop (doublet) production and injection history data. The porosity was calibrated by simulating the two tracer tests carried out at Habanero. In preparing future production forecasts, four different well layouts were considered: staggered line drive (SLD); inverted 4-spot, regular 5-spot and east-west SLD. For each scenario, closed-loop circulation at 25, 35 and 45kg/s per well was modeled for a production period of 20 years. The well patterns were stretched to about the maximum well separation available within the existing seismic cloud, as well as hypothetical seismic clouds. For a larger-scale development plan the best outcome was chosen by balancing short-term temperature against long-term extensibility. The results within the existing seismic cloud indicate the 4-spot layout as the most optimum. The best temperature performance is obtained from an extended seismic cloud when using an east-west SLD.

Estimating the thermal properties of soils and soft rocks for ground source heat pumps installation in Constanta county, Romania

The main objective of ThermoMap project was to develop a methodology for estimating the thermal conductivity and heat capacity in the first 10 m of the ground, in order to identify areas favourable for installation of ground heat source pumps. Based on best available data regarding climate, soil type, soil texture, geology and water table depth, maps of the thermal parameters were computed in test areas from partner countries. Three depth layers were investigated: 0–3, 3–6 and 6–10 m, each one characteristic for different types of ground source heat pumps. In order to check the computed values, samples were collected in test areas and measured in the laboratory. This paper presents the results of the validation performed for Constanta county test area (Romania). Samples of soil and Quaternary formations collected in the Danube terraces and the Black Sea high shores were analyzed in the laboratory for determining the bulk density, soil texture, thermal conductivity and heat capacity. The measurements were performed on samples simulating the three possible system conditions: unsaturated (arid or humid) and saturated conditions. The values determined by laboratory measurements were interpolated in order to obtain the appropriate thermal conductivity values for the defined bulk density values used by ThermoMap for each depth layer. The comparison between ThermoMap computed data and the laboratory measurements of thermal conductivity showed that out of three samples, at least two are within the specified error range of ±25 %. The best fit occurs for layer 3–6 m, whose assigned density is closer to the mean of measured bulk density values.

Hardware and Software for Determining the Thermal Properties of Rocks Under Close to Stratified Conditions

An instrument for determining the nonlinear thermal properties of rocks under natural conditions is proposed. Software is developed for processing the temperature readings, obtained from the instrument sensors, using mainly the theory of the solution of inverse problems for a parabolic-type nonlinear equation. Practical examples of the determination of the nonlinear thermal properties of some materials are presented.

Effect of groundwater flow in vertical and horizontal fractures on borehole heat exchanger temperatures

Vertical closed loop systems, also known as borehole heat exchangers (BHEs), are a popular way of extracting the ground source heat energy. Primary factors affecting the performance of BHEs are the thermal and hydrogeological properties of the subsurface. Groundwater flow is known to potentially influence heat transport and system performance. The effect of groundwater movement is more commonly studied under homogeneous conditions. However, in heterogeneous fractured rocks, BHEs are more common than horizontal or open loops due to lack of sufficient soil layers and productive aquifers. The finite-element modelling shows that fractures can play an important role in BHE functioning. Especially, vertical open fractures (≥1 mm) near the borehole (≤10 m) can have a considerable impact. Although increase in fracture aperture continuously affects the subsurface and BHE temperatures, the increase in its effect progressively lessens. Depending on the distance and aperture, one major fracture influencing the BHE operation performance can be identified; yet a larger number of fractures may govern heat transport (thermal plume outline) and thermal recovery. Individually, horizontal fractures may have less influence than vertical fractures. However, as the density of horizontal fractures increases, their impact can be major, exceeding that of fracture aperture. In particular, we propose that measurements of rock thermal properties be combined with fracture mapping, to better analyse the thermal response testing results and integrate the configuration of fractures in design and layout of the BHE(s). This is particularly valid for (vertical) fractures not intersecting with the borehole.

Thermal conductivity of the sedimentary-cover rocks of the West Siberian Plate in relation to their humidity and porosity

We analyze the results of measurements of the thermal conductivity, porosity, and permeability of Mesozoic sedimentary rocks from wells drilled in the northeast of the West Siberian Plate and in the Cis-Yenisei basin. The thermal conductivity was measured by a “Thermal-conductivity comparator”, and the porosity and permeability were determined using standard techniques. A total of 135 samples of dry rocks were studied for thermal conductivity (Ad). Ninety-two of them were then saturated with water, and their thermal conductivity was measured again. The average thermal conductivity of dry and water-saturated (Aw) sedimentary rocks is 1.8-2.0 W/m/K and 2.4-2.8 W/m/K, respectively. Porosity (Kpor) was measured for 95 samples, and permeability (Kperm), for 44 samples. Comparison of the results of measurements revealed stable linear correlations between the thermal conductivity of dry samples and Aw, Kpor, and Kperm. The established dependences are proposed for the express evaluation of the thermal (Aw from Ad and Kpor values) and structural (Kpor and Kperm from Ad values) properties of sedimentary rocks, though the revealed correlations need further refinement.

Thermal and transport properties of the sedimentary rocks at Site C0020, IODP Expedition 337 in Sanriku-oki basin off Shimokita Peninsula

Thermal and transport properties of the sedimentary rocks at Site C0020, IODP Expedition 337 in Sanriku-oki basin off Shimokita Peninsula

Analytical solutions for transient temperature distribution in a geothermal reservoir due to cold water injection

An analytical solution to describe the transient temperature distribution in a geothermal reservoir in response to injection of cold water is presented. The reservoir is composed of a confined aquifer, sandwiched between rocks of different thermo-geological properties. The heat transport processes considered are advection, longitudinal conduction in the geothermal aquifer, and the conductive heat transfer to the underlying and overlying rocks of different geological properties. The one-dimensional heat transfer equation has been solved using the Laplace transform with the assumption of constant density and thermal properties of both rock and fluid. Two simple solutions are derived afterwards, first neglecting the longitudinal conductive heat transport and then heat transport to confining rocks. Results show that heat loss to the confining rock layers plays a vital role in slowing down the cooling of the reservoir. The influence of some parameters, e.g. the volumetric injection rate, the longitudinal thermal conductivity and the porosity of the porous media, on the transient heat transport phenomenon is judged by observing the variation of the transient temperature distribution with different values of the parameters. The effects of injection rate and thermal conductivity have been found to be profound on the results.