Thermal Conductivity Of Sandstone Research Articles

Thermal conductivity of sediments from well-logs and its application to determine heat flow density in the Pannonian Basin, Hungary

The thermal conductivity of rocks can be deduced from available data of exploration wells such as core samples, cuttings, lithological descriptions and geophysical well logs. We present a methodology for determining the thermal conductivity of the Neogene and Quaternary clastic sediments in the Pannonian Basin using geophysical well logs and thermal conductivity data measured in laboratory. The lithological composition consisting of shale, sand and water was identified and the volumetric fractions of these components were derived from wireline logging data that included natural gamma ray, resistivity, bulk density and neutron porosity logs. The bulk thermal conductivity was computed by applying an appropriate mixing law using the thermal conductivity values of the lithological components. The thermal conductivities of the lithological components were determined by the best fit of the calculated bulk thermal conductivity values to the laboratory data. Different mixing models are recommended to calculate thermal conductivity of shales and sandstones. The thermal conductivity of shales was calculated with the weighted harmonic mean of the constituents, where the volumetric fractions and the porosity were the weights. The thermal conductivity of sandstones can be equally well estimated by the weighted geometric mean and the three component lower Hashin-Shtrikman bound. The geometric mean was used in calculations due its simplicity. Shale to sand ratio was utilized to separate shaly and sandstone samples. Heat flow density determination was carried out using the Bullard-plot technique with thermal conductivities calculated by our method. Heat flow density calculated by our method is in the range of heat flow density values previously conducted but with substantially lower uncertainties. The significance of the method is that it allows the harmonization of the heat flow density in the countries lying in the Pannonian Basin, because the Neogene and Quaternary sedimentary cycle resulting in the filling of the basin was uniform throughout the basin.

Thermal conductivity of sandstones from Biot’s coefficient

Thermal conductivity of rocks is typically measured on core samples and cannot be directly measured from logs. We have developed a method to estimate thermal conductivity from logging data, where the key parameter is rock elasticity. This will be relevant for the subsurface industry. Present models for thermal conductivity are typically based primarily on porosity and are limited by inherent constraints and inadequate characterization of the rock texture and can therefore be inaccurate. Provided known or estimated mineralogy, we have developed a theoretical model for prediction of thermal conductivity with application to sandstones. Input parameters are derived from standard logging campaigns through conventional log interpretation. The model is formulated from a simplified rock cube enclosed in a unit volume, where a 1D heat flow passes through constituents in three parallel heat paths: solid, fluid, and solid-fluid in series. The cross section of each path perpendicular to the heat flow represents the rock texture: (1) The cross section with heat transfer through the solid alone is limited by grain contacts, and it is equal to the area governing the material stiffness and quantified through Biot’s coefficient. (2) The cross section with heat transfer through the fluid alone is equal to the area governing fluid flow in the same direction and quantified by a factor analogous to Kozeny’s factor for permeability. (3) The residual cross section involves the residual constituents in the solid-fluid heat path. By using laboratory data for outcrop sandstones and well-log data from a Triassic sandstone formation in Denmark, we compared measured thermal conductivity with our model predictions as well as to the more conventional porosity-based geometric mean. For outcrop material, we find good agreement with model predictions from our work and with the geometric mean, whereas when using well-log data, our model predictions indicate better agreement.

Effect of water saturation and temperature in the range of 193 to 373 K on the thermal conductivity of sandstone

The thermal conductivity of porous media is crucial for many geological and engineering projects. Although the thermal conductivity at low temperatures is often overlooked, it is of great significance to calculate the amount of heat that the ice sheet absorbs from the Earth. In this study, the thermal conductivity of dry and water-saturated sandstone was measured in the temperature range of 193 to 373K using a transient hot wire method. All samples were collected from East China, with a sample porosity distribution of 5 to 13%. The effects of temperature, water saturation and phase transition of fluid in the pores were investigated. The results indicate that the thermal conductivity decreases with an increase in temperature and that the decrease is steeper when the temperature is below 273K. Moreover, it is found that the thermal conductivity of the saturated sandstone is larger than that of the dry sandstone. With an increase in porosity, the thermal conductivity significantly increases in saturated sandstone but remains almost the same or even decreases in dry sandstones. Finally, it is revealed that the effect of phase transformation on the thermal conductivity is significant. When the water in pores becomes ice, the thermal conductivity increases significantly and increases further as the temperature decreases.

The Characteristics of Rock Thermal Conductivity of Coal Measure Strata and its Influence on Geothermal Field in Huainan-Huaibei Coalfield

The rock thermal conductivity of coal measure strata in Huainan-Huaibei Coalfield ranges from 0.37 W/mK to 4.36W/mK and the average value is 2.54W/mK. The thermal conductivity closely relates to lithology,buried depth,stratigraphic age and density, the thermal conductivity of sandstone is generally greater than the one of mudstone and coal, and thermal conductivity and depth, density all show the positive correlation relationship; The differences of thermal conductivity of rocks have greater effects on the Geothermal field characteristics, unconsolidated layers and coal seams with poor heat conductivity tend to cause the abnormal ground temperature.

Effect of pressure, temperature, and oil-saturation on the thermal conductivity of sandstone up to 250 MPa and 520 K

Effective thermal conductivity (ETC) of oil-saturated sandstone (porosity 13%) have been measured over a temperature range from (288 to 520) K and at pressures up to 250 MPa with a steady-state parallel-plate apparatus. The expanded uncertainty of thermal conductivity, pressure, and temperature measurements at the 95% confidence level with a coverage factor of k = 2 were estimated to be 2%, 0.05%, and 30 mK, respectively. The estimated uncertainty in ETC measurement does not include the uncertainty due to contact thermal resistance and radiative conductivity. A rapid increase of ETC was found for oil-saturated sandstone at low pressures between (0.1 and 100) MPa along various isotherms. At high pressures ( P > 100 MPa) a weak linear dependence of the ETC with pressure was observed. The pressure effect is negligible small after the first 100 MPa where bridging of microcracks or improvement of grain contacts take place. The temperature, ∂ ln λ / ∂ T P , and pressure, ∂ ln λ / ∂ P T , coefficients for oil-saturated sandstone were calculated by using the measured ETC. We interpreted measured ETC data for oil-saturated sandstone using various theoretical models in order to check their accuracy, predictive capability, and applicability. We demonstrated that the combined effect of porosity, temperature, pressure, and fluid saturation can be predicted accurately using a Zimmerman's model. The effect of saturating fluids, structure (size, shape, and distribution of the pores), porosity, and mineralogical composition on temperature and pressure dependences of the ETC of oil-saturated sandstone was discussed.

Effect of temperature and pressure on the thermal conductivity of sandstone

Effective thermal conductivity (ETC) of dry sandstone was measured over a temperature range from 275 to 523 K and at pressures up to 400 MPa with a guarded parallel-plate apparatus. The estimated uncertainty of the ETC measurements is 2%. The porosity of the sample was 13%. A rapid increase of ETC was found for dry sandstone at low pressures between 0.1 and 100 MPa along various isotherms. At high-pressure range ( P>100 MPa) a weak linear dependence of the ETC with pressure was observed. The pressure effect is negligibly small after first 80–100 MPa where bridging of microcracks or improvement of grain contacts takes place. We interpreted the measured ETC data using a various theoretical and semi-empirical models in order to check their accuracy and predictive capability. The effect of structure (size, shape, and distribution of the pores), porosity, and mineralogical composition on temperature and pressure dependences of the ETC of sandstone was discussed. To estimate the effect of temperature and pressure on the ETC of sandstone the pressure, β P , and temperature, β T , coefficients of ETC were calculated from the measured values of ETC. The measured values of the ETC were also used to calculate the values of the isothermal compressibility, χ T , and thermal expansion coefficient, α. The equation of state of sandstone was developed using the measured ETC data.

Thermal conductivity of sandstone at high pressures and temperatures

Results are given of experimental investigations of the coefficient of thermal conductivity of samples of sandstone at hydrostatic pressures of up to 400 MPa and temperatures of 275–523 K. It is demonstrated that the pressure increase causes a weaker temperature dependence of thermal conductivity. Processes are discussed which lead to additional scattering of heat waves in disordered media.