Dueterium and 18O analyses were made on waters associated with oil and gas from Niigata basin. The δD and δ18O values of formation waters vary from -8 to -20‰ and -4 to +3.5‰ relative to SMOW respectively. The δ18O values of formation waters from lower horizons tend to enrich the heavier oxygen. There is a positive correlation between δ18O value and formation temperature. Although the δD and δ18O values of condensed waters vary widely, they seem to be lighter than those of formation waters. It is inferred that the origin of formation waters may be sea waters entrapped during deposition and undergone chemical and isotopic alteration since their original entrapment. The isotopic composition of condensed waters and formation waters in a reservoir shows a stragiht line on δD vs δ18O plot. The estimated temperature from slope of the line agrees with measured temperatures. Since the isotopic compostion of condensed waters in a gas pool may have a close relationship to distance from the water level, it could be useful in monitering the gas/water contact.
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.