Alan Judge

Terrestrial heat flow from project CESAR, Alpha Ridge, Arctic Ocean

During two months in spring, 1983, a multidisciplinary study, project CESAR, was undertaken from the sea ice across the eastern Alpha Ridge, Arctic Ocean. In the geothermal program, 10 gradiometer profiles were obtained; 63 determinations of in situ sediment thermal conductivity were obtained with the same probe, and 714 measurements of conductivity using the needle probe method were obtained on nearby core. Weighted means of the thermal conductivity of the sediment are 1.26 W/mK (in situ) and 1.34 W/mK (core), consistent with the compacted sediment encountered across the ridge and with the lithology. Calculated terrestrial heat flow values, corrected for the regional topography, range from 37 to 72 mWm−2; the average is 56+/−8 mWm−2. Some temperature and heat flow versus depth profiles exhibit non-linearities that can be explained by physically reasonable (but otherwise unsubstantiated) variations in bottom water temperatures preceding the measurements; models are hypothesized that reduce the curvatures. Two heat flow values considerably higher than others in the area may be explained by higher bottom water temperature over several years, while the low value is consistent with a recent deposition from a slump. This hypothetical modelling reduces the scatter of heat flows and reduces the average to 53+/−6 mWm−2. The CESAR heat flow is somewhat greater than expected for a purely continental fragment but is consistent with crust of oceanic origin. The heat flow is similar to values obtained in Cretaceous back-arc basins. Based on the oceanic heat flow-age relationship, the heat flow constrains the age of the ridge to 60–120 million years. The heat flow observed on other aseismic features in the worlds oceans suggests that the Alpha Ridge has experienced no significant tectono-thermal event in the last 100 million years.

Automatic Data Acquisition System Installed in Offshore Canadian Arctic Well; Monitoring Precise Temperatures By Acoustic Telemetry

A methodology has been developed to instrument an offshore petroleum exploration well for long term downhole temperature observations. A demonstration deployment was completed successfully in May, 1985 at a well in 244m of water in the Canadian Arctic. The data acquisition system acquired well temperatures to 800m below the sea floor at 4 hour intervals for most of the first year following system deployment and well abandonment. Data was transmitted acoustically through the water to a recording package left on the sea ice. The concept has application in monitoring temperatures and other parameters in abandoned holes and in production wells. The recording package could be mounted in a buoy for open sea areas.