Method for determining the thermal conductivity of in situ formation rock using drilling cuttings

Abstract

In this paper, a method for determining the thermal conductivity of in situ formation rock, which combines experimental measurements, theoretical model predictions, and geophysical logging of formation porosity, is presented to predict the thermal conductivity of in situ formation rocks (this method effectively combines experimental measurements, theoretical model, and geological conditions, referred to as “ETG,” where E is for experimental measurements, T is for the theoretical model, and G is for geological conditions). 24 drilling cuttings samples from rocks down to a depth of 2000 m were selected for transient plane source thermal conductivity tests, and an effective thermal conductivity method was used to predict the thermal conductivity of rocks corresponding to each formation. The predicted thermal conductivity of mudstone was 2.31–3.27 W/(m K), and that of sandstone was 2.40–3.69 W/(m K). An independent-samples t test was carried out between the thermal conductivity results from the ETG prediction method and those from a diagenetic mineral-theory model. The results showed that there were no statistically significant differences between the two groups (P > 0.05) and that the fitting degree was high. The mean-square error in the solid thermal conductivities determined by the two methods was about 0.3, which indirectly demonstrates that the ETG method has high accuracy for predicting the thermal conductivity of in situ formation rock. Therefore, this method is likely to become popular in engineering practice.