Munesuke Kyo

Continuous measurement of effective thermal conductivity of well cuttings - water mixture at geothermal conditions by hot-wire method under transient temperature field

Abstract A new continuous technique has been developed for the rapid measurement of the effective thermal conductivity of cuttings-water mixture beds at simulated in situ geothermal conditions to estimate the thermal conductivity of rocks in situ. The technique is based on a modified transient hot-wire method. Beds of mixtures of pure fused quartz grains and water were used as reference samples. Measurements were made at a sample heating rate of 20°C/h from room temperature to 110°C for the reference and to 200°C for the cuttings, and at natural cooling conditions from their maximum temperatures to room temperature. Higher accurate data were obtained with natural cooling than with forced heating. Thermal conductivity of the fused quartz grains estimated from the Kunii-Smith formula and the measured effective thermal conductivity of the sample agreed with literature data within the sum of experimental and estimating errors, ± 15.0% . Data obtained with cuttings from the Satsunan geothermal field, Kyushu, Japan are discussed.

Practical measuring method of thermal conductivity of drilling mud at high temperature and high pressurs.

The transient hot-wire method have been used to measure the thermal conductivity of gases and liquids acculately using a very thin wire of diameter from 15 to 40μm, recently. On the other hand a practical method to measure thermal conductivities of viscous suspensions contained fine and/or coarse grains easily with practically enough accuracies at a high temperature and high pressure is needed in the fields of drilling technology and others. A needle probe type sensor having 2mm in diameter and 1, 000mm in length with a thermopile of six magnifications of sensitivity of temperature and the measuring system were developed. The thermal conductivites of three standard and test samples were measured by analyzing the data of smooth curve relations at an early period between the temperature increase of the probe and the constant heat supplied time to the probe using a theory of unsteady hot thick wire method and the multivariate analysis. Measurement errors of this method were estimated at less than ±10%. Thermal conductivity of montmorillonite-water based muds having concentrations of 3.0, 6.0 and 10.0% were measured at the temperature range from 20 to 180°C. From the measurement characteristic temperature and concentration dependencies on the thermal conductivity of the mud were obtained.