Deep subpermafrost thermal regime in the Mackenzie Delta basin, northern Canada—Analysis from petroleum bottom‐hole temperature data

Abstract

In our studies of the thermal regime of sediments of the young Mackenzie Delta in the southeastern part of the Beaufort-Mackenzie basin of northern Canada, we used thermal data from the base of the permafrost layer, together with temperature data from petroleum wells. By analyzing bottom-hole temperature (BHT) data, we found that the percentage correction, i.e., the percentage difference between BHT and equilibrium temperature, is less than 10% ((with 67% probability) for times exceeding 10 hours after circulation ended, regardless of circulation time. No correlation exists between the percentage correction and depths for the BHT data. Theoretical temperature-depth profiles were constructed from the individual heat flow Q, Q [Formula: see text] and [Formula: see text] values (δQ is error of estimate of Q), the interval thermal conductivities, and a permafrost base temperature of 0°C. Estimates of Q were based on the maximum BHTs from depths >2.7 km. The measured and corrected BHT values for depths less than 1.5 km lie outside the range defined by the predicted temperature and temperature at the base of permafrost. Therefore, the temperature gradient based on interval‐temperature difference between deep and shallow BHTs or ground‐surface temperature and shallow BHTs may not represent the thermal field accurately within the sedimentary strata. The temperature data from the maximum depths, the permafrost base temperature of 0 °C from the 10 deep wells, and estimated thermal conductivities for the sedimentary column give an average heat flow [Formula: see text] of [Formula: see text] (error of estimate of the individual Q value, [Formula: see text]), which is comparable to the values found in the region of the Canada basin.